Orals: Mon, 28 Apr | Room -2.21
We investigate the suitability of radiolarian species as palaeoceanographic proxies in the Northwest Pacific Ocean using 33 new core-top samples collected since 2021 during Joint Usage/Research Center for Atmosphere and Ocean Science (JURCAOS, Japan), combined with existing datasets published by authors of this study. The main target of this study is to review the suitability of radiolarian species as a paleoceanographic proxy and to develop a robust methodology to estimate past Sea Surface Temperature based on radiolarian species abundances. For this purpose, we compiled our new data from the East China Sea and Central Northwest Pacific with previous datasets obtained in the same area, Japanese coast, and Japan Sea. Our analysis revealed considerable differences between Sea of Japan and Northwest Pacific radiolarian assemblages, suggesting different responses of biota to environmental changes in this marginal sea; thus, we excluded Sea of Japan data from Northwest Pacific Sea Surface Temperature (SST) reconstructions. Factor Analysis identified four radiolarian assemblages in the Northwest Pacific and East China Sea, each associated with specific water masses and SST ranges: Subtropical, Sea of Okhotsk-related subarctic, Oyashio Current to transitional zone-related, and coastal water assemblages. Warm-water species (e.g., Tetrapyle circularis/fruticosa, Dictyocoryne tetrathalamus) showed strong correlation with temperatures above 24°C, while cold-water species (e.g., Lithomelissa setosa, Ceratospyris borealis) were linked to temperatures below 14°C. Literature review suggests these radiolarian-based SST reconstructions primarily reflect summer conditions. Using weighted averaging partial least squares analysis, we reconstructed past summer SSTs at IODP Site U1429 in the northern East China Sea with high precision (R²=0.97, ±1.4°C). These reconstructions align well with Globigerinoides ruber Mg/Ca-based summer SSTs, despite minor glacial period discrepancies, while showing consistent offsets from alkenone-based estimates, likely due to seasonal biases.
How to cite: Matsuzaki, K., Itaki, T., Kubota, Y., Lee, K. E., Motoyama, I., Sagawa, T., Horikawa, K., Murayama, M., and Obata, H.: Radiolarian Microfossils as a Tool for Reconstructing Sea Surface Temperature of the past in the Northwest Pacific, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-247, https://doi.org/10.5194/egusphere-egu25-247, 2025.
The Fergana Basin, one of the largest depressions in Central Asia, is situated within the intermountain range of the southwestern Tien Shan. The final stage of marine sedimentation in the basin, represented by middle Eocene layers, marks the onset of the Asian aridification. This shift in paleoenvironmental conditions coincided with significant global changes, including the restriction of the Peri-Tethys, the isolation of Asian realms, and alterations in oceanographic and climatic systems. Microfossil assemblages provide important information about changes in the palaeoenvironment. Despite the abundance and importance of foraminifera and ostracods in the Fergana Basin, the paleoenvironmental conditions, species diversity, and paleobiogeography remain poorly understood, largely due to the outdated literature, most of which is in Russian. The present study focuses on foraminiferal and ostracod assemblages to gain new insights into environmental changes within the Fergana Basin and its connections to other marine basins during the middle Eocene. The material analyzed in this study comprises foraminifera and ostracods collected from the Sauk-Tanga section (40° 2'50.82"N, 70°15'42.70"E) and the Chamangul section (40° 1'50.34"N, 70°26'7.82"E), both located in the southern part of the Fergana Basin. The study site is located within the Madygen Geopark in the Batken Region of Kyrgyzstan, and the sections comprise an expanded middle Eocene clay sequence.
A total of 17 foraminiferal species and 11 ostracod species were identified. The foraminiferal community is characterized by three distinct assemblages: one dominated by Cribroelphidium, one comprising a combination of Ammonia, Cribroelphidium, and Nonion, and another dominated solely by Nonion. A comprehensive analysis of the micropaleontological assemblages indicates that conditions were shallow and fully marine during the Middle Eocene epoch. The environmental conditions are marked by elevated oxygen levels within the water column, extending from the intertidal zone to the high subtidal regions, in contrast to the low oxygen conditions prevalent within the sediments. The microfauna recovered is comparable to faunal communities in Europe and western Siberia, as well as neighboring regions such as the Tajik and Tarim basins. However, it differs significantly from the microfauna of the Turan Basin. The findings indicate that the Fergana Basin functioned as a transitional zone between the western Peri-Tethys and the easternmost realms, contradicting previous hypothesis that it merely served as a gulf. This novel perspective contributes to a more comprehensive understanding of the region's paleogeography and its significance in broader paleoenvironmental changes.
How to cite: Trubin, Y., Winkler, A., and Langer, M.: Paleoenvironmental reconstruction and transitional role of the Fergana Sea (Central Asia) during the middle Eocene through the lens of Micropaleontology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17334, https://doi.org/10.5194/egusphere-egu25-17334, 2025.
Charophytes, a group of green algae, are one of the main components found in continental carbonate microfacies. The combination of the palaeontologic (taxonomic and taphonomic) study with the sedimentologic analysis has demonstrates that the charophyte microfacies are highly diverse, representing a broad diversity of environments. However, the integration of these palaeoecological data with geochemical proxies (stable isotopes and elementary geochemistry) has not been poorly explored
Sixty-three thin sections from different levels were obtained along the 50 m-thick carbonate section of La Pedrera de MeiàKonservat-Lagerstätte (Southern Pyrenees, Spain). Two thin sections were obtained from charophyte-rich beds, which is demonstrated as useful to study charophytes in thin sections. A combined sedimentological study and taphonomic analysis of the fossils was performed to make palaeoecological inferences. The results were latter integrated with the palaeoenvironmental proxies, mainly elementary geochemistry and δ18O previously described in the same facies with the objective of refining the palaeoenvironmental reconstruction of the lake.
According to the palaeoecologial analysis, two communities are distinguished. Monospecific Echinochara sp.-Charaxis spicatus meadows solely occurred in temporary lakes formed during the early stages of the infilling. These meadows were associated to high Al, K, Fe and Ti concentrations, which suggests that the infilling of these lakes was associated to meteoric waters. The δ18O indicates intermittent periods of evaporation, which favoured the formation of cyanobacterial crusts around charophyte remains and the formation of mud-cracks visible in thin sections under the microscope.
The second charophyte assemblage coincides with the last stage of the lake infilling and was characterized by having two distinct communities, freshwater and brackish. The freshwater community as composed of mixed meadows with Atopochara-Clavatoraxis, Clavatoroidae utricles -Clavatoraxis, and Ascidiella-Favargerella plants while the meadows of brackish settings were composed of Porocharacean – Charaxis sp. and Echinochara sp.-Charaxis spicatus plants. This latter flora was associated to miliolids and broken dasycladaleans, suggesting brackish conditions. The Sr/Ba ratios are high suggesting marine influence, but REE+Y concentrations, and δ18O values previously reported for these lacustrine carbonates suggest predominantly freshwater conditions. These geochemical results suggest the establishment of dominantly freshwater environments with rare brackish to marine influence. This interpretation aligns with the presence of distinct brackish and freshwater charophyte assemblages, along with organisms exhibiting marine affinities, such as miliolids and dasycladaleans.
The present work demonstrates the value of cross-validation between geochemical and palaeontological and palaeoecological data of lacustrine settings that contain benthic organisms, such as charophytes and ostracods. In addition, this work also provides insights to understand the palaeoenvironmental conditions necessary for the thriving of these organisms in fossil lakes.
How to cite: Perez-Cano, J., Gil-Delgado, A., Oms, O., and Mercedes-Martín, R.: Integrating Charophyte Paleoecology and Geochemical Proxies in the La Pedrera de Meià Konservat-Lagerstätte (Southern Pyrenees, Spain): A Tool for better understanding fossil lacustrine settings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4519, https://doi.org/10.5194/egusphere-egu25-4519, 2025.
This study examines the sedimentation of the calcified microbes in the late Miaolingian and Furongian microbialites in response to relative sea-level changes. The microbialites mainly bulge out as undifferentiated microbial boundstones observed as leiolitic bioherms in the upper reaches of four third-order depositional sequences, as recognized through the Gushan, Changshan and Fengshan formations. A flat-bedded biostromal thrombolite also developed in the lower Furongian strata, with a variety of poorly-preserved calcimicrobes. In geologic record, the variety of microbialites is widely attributed to the microbial mats of diverse size and bionetwork. The cyanobacteria are believed to predominate other mat-building microorganisms in mediating a sophisticated in-situ carbonate precipitation across the Miaolingian-Furongian boundary interval. A rapid shift in the microbialite microfabric from Miaolingian to Furongian is observed in the study area, which is marked by a substantial increase in the diversity and abundance of calcified microbes. The Miaolingian leiolitic bioherms hold abundant crust-forming structures in the mixed ground mass of micrite and microspar. With reduced occurrence, these possible microbial structures with uncertain biological affinity extend upward across Miaolingian-Furongian boundary. The Furongian leiolitic bioherms are unique as they developed in response to forced regression during third-order relative sea level fall. The well-preserved calcimicrobes recovered from these bioherms include Girvanella, Subtifloria, Epiphyton and Renalcis confirm the recovery phase of microbial carbonate abundance and the intense cyanobacteria calcification episode of Cambrian-Early Ordovician. The recovery of Epiphyton from the Furongian microbialites in the study area contradicts the possible decline in Epiphyton abundance at the end of Miaolingian series, as reported from other parts of the North China Platform. This study offers significant implications towards the sedimentation pattern in the shallow skeleton-deficient sea during Furongian before the metazoan radiation of the middle Ordovician.
How to cite: Latif, K., Riaz, M., and Xiao, E.: Late Miaolingian to Furongian Transition in Calcified Microbes from the North China Platform (Shanxi Province): Implications for Microbialite Development, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-937, https://doi.org/10.5194/egusphere-egu25-937, 2025.
Moyano strongly pointed out that the origins and evolutionary history of the Bryozoa both Antarctica and magellanic South America could not be understood without reference to the still poorly known but very extensive Paleocene and Lower Miocene faunas of Patagonia (see Moyano, 1983.
The taxonomic studies with the extensive use of SEM of more than 110 bryozoan specimens of the Early Paleocene (Danian) and the Lower Miocene of the southern South America (Patagonia) from the Canu’s collections (1908-1911) at the Bernardino Rivadavia Museum have revealed that cyclostomes and cheilostomes have their taxonomical counterparts among the late Early Eocene fauna of Seymour Island, Antarctic Peninsula (Hara, 2008). One of the example is the anascan microporoidean represented by austral Aspidostoma Hincks, 1881 genus, known from the Paleogene and the Neogene strata of the triangle Antarctica-South America-Australia-New Zealand. It shows their earliest fossil record in the Lower Danian of Patagonia, therefore Patagonia should be consider as an important place of origin and migration route of this genus. A rich occurrence of Aspidostoma has been also described from the late Early Eocene, clastic sediments of the La Meseta Fm. on Seymour Island (Hara 2001). Other bryozoans such as umbonulomorph (lepraliellids) represented by multilaminar, massive Celleporaria Lamouroux, 1821 occur also in the shallow-water Roca Fm. of Patagonia and predated the rich occurrence of this genus from the late Early Eocene of the La Meseta Fm. (Seymour Island). Particularly important for taxonomy and closest biogeographical connection of South America-Antarctic during the Early Paleocene up to the Lower Miocene has the common occurrence of several globular, multilaminar cyclostomes of Ceriopora, Reptomulticava, as well as reticulate colonies of Reticresis, branched microporidean Aspidostoma, and nodular multilaminar umbonulomorphs of Celleporaria and Osthimosia.
Biogeographical comparision of the southern South America bryozan fauna of the Early Paleocene age is interesting because the Canu’s collections contains important information that some of the taxa have the earliest fossil records in the Patagonian shallow-water Roca Fm., which predated the younger New Zealand and Antarctic bryozans ranging from the latest Paleocene- Early Eocene.
The Southern Ocean bryozoans seems to be a product of the long period of evolution in situ, possibly streaching back to late Cretaceous, therefore the reconstruction of the Cenozoic ecosystem, possible migration routes and paleobiogeography of the Weddellian Province of the southern hemisphere should be refer to the Antarctic fauna, possibly of the Createous age.
Hara U., 2001 – Bryozoa from the Eocene of Seymour Island, Antarctic Peninsula. Palaeontologia Polonica. In: Palaeontological Results of the Polish Antarctic Expeditions, Part III, 60: 33–156.
Hara U., 2008. Biogeographical relationship of the Cenozoic South America -Antarctic bryozoan biota: an example of austral Aspidostoma genus in Antarctica: a Keystone in Changing World – Online Proceedings of the 10th ISEAS, edited by A. K. Cooper and C.R.Raymond et al. USGS open File Report 2007-xxx, Extended Abstract yyy, 1-5.
Moyano, G.H.,I., 1983. Southern Pacific Bryozoa : a general view with emphasis on Chilian species. Gayana, Zoologia, 46, 1-45.
How to cite: Hara, U.: Biogeographical links of the South American-Antarctic bryozoan biota in Cenozoic (Early Paleocene-Miocene), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20474, https://doi.org/10.5194/egusphere-egu25-20474, 2025.
Coastal xeric ecosystems face a major threat under the current global warming trend. Changes in water availability and precipitation patterns can contribute to the development of new landscapes and affect existing biotic interactions. The late Miocene, characterized by warm climates and comparable pCO2 values (∼400 ppm), presents an opportunity to understand future warming scenarios for dry coastal ecosystems. In this study, we present the first-known late Miocene paleobotanical record from the Peruvian coast (15ºS), where a non-vegetated desert is found today. Recalibrated leaf-based precipitation estimates indicate that coastal rainfall values were 4 times higher than today; while significant wetter conditions compared to the present existed on the western slopes during the austral summer. The combined paleobotanical record reveals a diverse community dominated by elements typical of modern dry forests rather than desert-like habitats, including a mixture of lowland and Andean wooded taxa. These findings suggest a substantial shift in the ecosystem that allowed the development of a greener woodland landscape along the central Peruvian coastal region during the warmth of the late Miocene. Although the sources of extra humidity remain uncertain, warmer sea surface temperatures in the eastern Pacific and local convection may have contributed to the additional moisture. Moreover, intensified or even a permanent El-Niño state during the warmer late Miocene could have potentially served as an additional moisture source. Regardless of the mechanism, our results provide compelling evidence of reduced aridity, leading to a greening of the coastal Peruvian desert and large-scale biome and landscape changes in response to the Miocene greenhouse climate.
How to cite: Ochoa, D., Montenegro, J.-F., Salas-Gismondi, R., Carre, M., and Flores, J.-A.: A Late Miocene paleobotanical record from the Peruvian Pisco Formation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15553, https://doi.org/10.5194/egusphere-egu25-15553, 2025.
Intramontane basins serve as exceptional archives of long-term climate, depositional and environmental changes. Additionally, these basins are biodiversity hotspots, harboring freshwater lacustrine fauna, making them invaluable for studying the interplay between paleoenvironmental dynamics and evolutionary processes.
During Miocene, a multitude of intramontane basins emerged within the Dinarides mountain range. The basins were filled with a series of long-lived lakes, hosting endemic lacustrine fauna significant for understanding Neogene paleoenvironments and paleogeography. Two freshwater systems, representing distinct paleobiogeographic entities, occupied areas corresponding to present-day Croatia and Bosnia and Herzegovina (Dinarides Lake System, DLS) and Serbia, Kosovo, and North Macedonia (Serbian Lake System, SLS). Faunal samples were collected from various localities within the DLS and a single locality in the SLS. Within the DLS, key sites include the Kupres, Livno, and Tomislavgrad basins in Bosnia and Herzegovina, whereas the samples retrieved from the SLS belong to the Valjevo-Mionica Basin in western Serbia.
This research aims to comprehensively revise and provide detailed taxonomic descriptions of the freshwater benthic assemblages from both the DLS and SLS. Comparative analysis of ostracod and mollusk compositions has been used to investigate evolutionary connections between species in these intramontane lacustrine systems. The ostracod fauna is of particular interest due to the absence of in-depth descriptions and detailed figures. In contrast, mollusk assemblages have been thoroughly revised and described in previous publications. Correlation within the DLS is based on ostracod and mollusk samples from the Table section (Livno Basin), the Kongora section (Tomislavgrad Basin), and the Fatelj section (Kupres Basin). A taxonomic analysis was conducted using samples from the Ribnica section of the Valjevo-Mionica Basin to compare this fauna with that of the SLS.
The future direction of this research involves expanding comparative taxonomic analyses with other Neogene long-lived lakes, aiming to provide deeper insights into evolutionary patterns and further our understanding of faunal developments.
How to cite: Mužek, K., Mandic, O., Hajek-Tadesse, V., Andrić-Tomašević, N., and Rundić, L.: A comparative study of lacustrine ostracods and mollusks of the Dinarides and Serbian Lake Systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7355, https://doi.org/10.5194/egusphere-egu25-7355, 2025.
A holy grail of both palaeoecology and biogeochemistry has been an accurate proxy of past biological productivity. Such a metric would offer a way to identify and quantify Earth’s deep-time ecosystem and carbon cycle function (and dysfunction). Plants have been the principal contributors to the terrestrial carbon cycle for hundreds of millions of years. We hypothesise that their absolute abundances in the fossil record can indicate ecosystem-mediated changes in carbon sequestration rates (='terrestrial net ecosystem productivity').
Many key parameters of biological systems—e.g., productivity, population sizes, biomass—are best expressed as absolute values. Unlike proportional data (e.g., percentages), absolute values provide standardized metrics for comparing the functioning of organisms, species and ecosystems across time and space. Since it is generally impractical to count entire populations, statistically significant abundance estimates require an accurate and precise sampling method. These typically entail more data collection effort (or time) than proportional data.
Firstly, we present a new method for precise estimates of microfossil concentrations: the ‘field-of-view subsampling’ (FOVS) method. It applies ecological quadrat sampling principles to microfossil samples spiked with exotic markers (e.g., Lycopodium spores). We tested the new FOVS method against the traditional ‘linear method’ with two case studies: 1, computer simulations; and 2, observational data of terrestrial organic microfossils from the end-Permian event (EPE; c. 252 Ma) records of eastern Australia. Four output parameters were measured: 1, absolute abundance (measured as specimens per unit sample size [e.g., sediment mass]); 2, accuracy (measured as variance from an idealised data set); 3, precision (measured as statistical error); and 4, data collection effort (measured as time). The FOVS method consistently provided estimates with greater accuracy, and higher precision and/or reduced effort under almost all conditions.
Secondly, we assessed the potential application of this method (and others) for gauging palaeoproductivity. As a result of this review, we: 1, identified the factors that influence the preservation of land-derived organic carbon in the fossil record; 2, adapted and applied a framework of modern ecosystem productivity to prehistoric settings by incorporating post-burial impacts; and 3, explored the conditions under which terrestrial organic microfossil concentrations may provide valid estimates of relative changes in palaeoproductivity.
Lastly, we demonstrate how refined estimates of deep-time terrestrial productivity may be achieved in the future. This would lead to more precise land carbon cycle models since the emergence of large land plants >360 million years ago.
Although we have explored a narrow application of the new method to palaeoproductivity, the range of potential applications is far broader. In the microfossil realm, the method can be immediately applied to any study using exotic markers (e.g., Lycopodium spores) for absolute abundances. Given its demonstrable increased efficiency, we recommend the FOVS method as the new standard for such absolute abundance estimates.
How to cite: Mays, C., Hren, M., Amores, M., Tyson, R., and Mays, A.: A novel method for improved estimates of absolute microfossil abundance: A big step towards a deep-time terrestrial productivity proxy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6742, https://doi.org/10.5194/egusphere-egu25-6742, 2025.
Understanding past changes in oceanic circulation and the corresponding heat, salt delivery variations are essential for assessing the climatic roles of ocean dynamic processes since the last glacial period. Unravelling salinity budget variation in the North Pacific and its controls is important to better understand the North Pacific Intermediate/Deep Water formation and associated climate impacts. The Tsushima Warm Current (TWC), the northernmost Kuroshio branch entering the semi-closed Japan Sea through the shallow strait, is regarded as a fundamental component for oceanographic changes in the Japan Sea.
To obtain a comprehensive history of the Japan Sea salinity budget, this study reconstructed the evolution history of the TWC inflow by compiling paleo-hydrographic records in the Japan Sea, including the radiolarian, diatom, coccolithophore, and planktonic foraminiferal assemblages. Following a persistent but weakened TWC inflow during Marine Isotope Stage 3, radiolarian assemblage data revealed that the TWC taxa disappeared since ~30 thousand years ago (ka). The synchronous onset of the low salinity anomaly event was in response to the cutoff of saline TWC inflow due to the rapid fall in global sea level at 30 ka. Extreme restriction of seawater exchange caused a persistent freshening of the glacial Japan Sea and formed a low-salinity water mass in the upper ocean. The compiled microfossil data confirmed that the Japan Sea accumulated excess freshwater during the glacial sea-level lowstands and the low-salinity pool extended downward to ~900 m depths. Coinciding with the peak of the low salinity anomaly event (minimum values of ∼20 psu), re-emerging TWC inflow after 19 ka reflected the reconnection of the open ocean to the Japan Sea. The persistent TWC inflow mainly drove the reduction in magnitude of the deep low-salinity pool during the last deglaciation. As a large and isolated freshwater sink for the glacial North Pacific, the deep low-salinity pool evolution could potentially have strong impacts on the North Pacific salinity budget and subsequent large-scale circulation.
How to cite: Dong, Z., Shi, X., Zou, J., Wang, S., Liu, Y., and Zou, X.: Global sea level controlled the deep low-salinity pool evolution in the Japan Sea since the last glacial period, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2258, https://doi.org/10.5194/egusphere-egu25-2258, 2025.
One of the most studied and debated time intervals in our planet‘s recent climate history is the Early-Middle-Pleistocene Transition (EMPT). It represents a significant reorganization in the global climate system between 1.2-0.7 Ma, without any considerable variation in the orbital parameters controlling Earth’s insolation. This climate rearrangement is exemplified by a strengthening of ice ages and a switch in the periodicity of the glacial/interglacial changes from 41 kyr to a quasi-100 kyr cyclicity. The causes of the onset of this global climatic transition remain unclear, and its impact on equatorial to mid-latitude shelf areas is, to date, scarcely investigated.
IODP Site U1460 (27°22.4949′S, 112°55.4296′E; 214.5 mbsl) is located in the south-eastern Indian Ocean, on the uppermost slope of the Carnarvon Ramp. The study area is of particular interest, as it allowed the recovery of an expanded EMPT section and appears to have never been exposed to sub-aerial conditions during the sea-level lowstands during the glacial phases. Therefore, it is well-suited to assess the sensitivity of the western Australian carbonatic platform at high resolution to the EMPT sea level fluctuations.
The studied sedimentary sequence represents a time interval between 639.91 and 1092.34 ka, from marine isotope stage (MIS) 16 to MIS 32. For this period, we reconstructed the plankton/benthos (P/B) ratio to qualitatively establish the eustatic fluctuations in the region, as highstand and lowstand stages correspond to higher and lower values of the P/B ratio, respectively.
The P/B ratio has been coupled with a benthic foraminiferal assemblage study to ascertain the ecological variations in the area and their link to the glacial-interglacial-induced sea level oscillations. Benthic foraminiferal assemblages revealed a polyspecific and highly diversified assemblage. Specifically, within the studied interval, we recorded more than 318 species, most of which are represented by <1% abundance. Preliminary data allowed to distinguish a first part of the record (MIS 27-23) dominated by Cibicidoides spp., Heterolepa spp., Trifarina bradyi, and nodosarids, from the most recent interval (MIS 22-16), which recorded abundant agglutinated tests (e.g., Gaudryina spp., Textularia spp., Spirotextularia spp.), Cibicidoides spp., Heterolepa spp., Siphogenerina spp., uvigerinids and bolivinids. Other common taxa are Lenticulina spp., Nuttallides umbonifer, cassidulinids and lagenids.
Benthic assemblage analysis revealed that diversity remains high throughout the record (average Shannon H´ = 4.24) but tends to decrease during interglacial intervals (average Shannon H´ = 4.001). Such a diversity decrease supports the persistence of warmer, more tropical conditions during interglacials at the study Site. Agglutinated tests’ abundance increases towards the most recent part of the record, but no significant changes in their abundance are noticeable at the glacial-interglacial turns. Conversely, the increase of dominance during the interglacial phases (MIS 17, MIS 19 and MIS 21) in the youngest part of the record seems to be linked to an increase in the uvigerinids abundance and a concomitant decrease in Cibicides/Cibicidoides abundance. The oldest part of the record (between 1092.34-755.59 ka) registered an important decline in the number of uvigerinids and a contemporary increase in the abundance of Trifarina bradyi and cassidulinids.
How to cite: Arrigoni, A., Piller, W. E., Mamo, B., Petrick, B., and Auer, G.: Benthic foraminiferal assemblage response to the Early-Middle Pleistocene sea-level variations in the south-eastern Indian Ocean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11038, https://doi.org/10.5194/egusphere-egu25-11038, 2025.
The production, export and accumulation of calcite (CaCO3) are key components of the marine carbon system and the global carbon cycle. Coccolithophores are responsible for ~20-80% of the open ocean CaCO3 production. Over geological timescales, their activity significantly influences the global carbon cycle, impacting long-term climate evolution. Despite the critical importance of this group, an integrated understanding of the environmental factors that control their CaCO3 production remains incomplete. This uncertainty arises from difficulties extrapolating laboratory-based findings to natural settings and challenges interpreting fossil records. We present new profiles of the distribution of key coccolithophore species and groups in the modern Atlantic Ocean alongside detailed morphometric analyses at the individual coccolith level. Applying a suite of advanced micropaleontological and morphometric techniques on well-preserved surface sediment materials, we explore different pathways for reconstructing coccolithophore physiology and CaCO3 production from nannofossil records. This research provides new insights into the dominant environmental controls over coccolithophore CaCO3 production in response to natural oceanic forcing. Relationships between coccolithophore assemblage structure, group-specific physiology, morphometric variability and CaCO3 production with the environment contribute to the understanding of the role of coccolithophores in the marine carbon cycle and provide a basis for a novel application of nannofossil assemblages for the reconstruction of past oceanic physicochemical conditions.
How to cite: González-Lanchas, A., Karl-Heinz, B., Heather M., S., José-Abel, F., Miguel Angel, F., and Rosalind E.M., R.: Coccolithophore calcite production from nannofossil records , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10717, https://doi.org/10.5194/egusphere-egu25-10717, 2025.
The Iberian Margin, including the Portugal Shelf, is a distinctive area in our planet, characterized by a narrow continental shelf where detrital sediments transported by rivers record continental climate patterns. Ocean dynamics in this region are strongly influenced by the Mediterranean Outflow Water (MOW), and the North Atlantic subtropical gyre, both key components of the Atlantic Meridional Overturning Circulation (AMOC) and essential for understanding climate dynamics.
Past research has demonstrated that sedimentary processes from this region are driven by astronomically-forced climatic mechanisms. This study assesses the interaction of continental and oceanic processes along the Iberian Margin during the early Pliocene, an interval of significant palaeoceanographic interest marked by the reestablishment of the MOW after the Messinian Salinity Crisis.
For this, a high-resolution study of calcareous nannofossils assemblages and X-ray fluorescence (XRF) analyses were carried out on sedimentary material retrieved from the 397 IODP expedition (site 1587, southwestern Iberian Margin). Calcareous nannofossils assemblages reveal changes in paleoenvironmental parameters such as productivity and sea surface temperatures, while XRF data indicate changes in continental input.
Based on spectral and wavelet analyses of the XRF data, we identify a robust astronomical signal of precessional origin in the sediments. Moreover, the abundance of Reticulofenestra minuta and Reticulofenestra pseudoumbilicus larger than 7 µm correlates with eccentricity-driven orbital changes. In contrast, Reticulofenestra producta, R. haqii y R. minutula exhibit declining abundance at the base of the Pliocene, suggesting modulation by oceanic mechanisms independent of astronomical forcing. These findings thus evidence the role of orbital-driven climate processes (eccentricity and precession) shaping the continental input. Furthermore, the calcareous nannofossil association reflects distinct ocean dynamics associated to the North Atlantic and processes that determine variability in productivity in the region.
How to cite: Martín García, L., Jiménez-Espejo, F. J., Ochoa, D., Helbert, T., Clark, W., and Flores, J.-A.: Deciphering continental and oceanic climate signals in early Pliocene sediments from the Iberian Margin , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8192, https://doi.org/10.5194/egusphere-egu25-8192, 2025.
This study focuses on high-resolution analyses of coccolithophore assemblages from a sediment core retrieved at IODP Site U1386, located in the Gulf of Cádiz. This area plays a crucial role in studying the Atlantic-Mediterranean water exchange. Our samples span the Termination V period (MIS 12-11, 434-404 kyr) that roughly corresponds with Mid-Brunhes Event, a major global climatic shift in glacial-interglacial cycles during the Quaternary. The main objective is to reconstruct coccolithophore paleoproductivity variations and use it as an indicator of surface ocean dynamics and environmental conditions during this critical interval of global environmental change.
Our results reveal higher paleoproductivity during the interglacial period (MIS 11), with an average of 8.33 × 10⁹ coccoliths/g, compared to lower paleoproductivity during the glacial period (MIS 12), with an average of 4.23 × 109 coccoliths/g. This difference is also reflected in nannoplankton assemblage composition: with cold-water species such as Coccolithus pelagicus subsp. pelagicus dominating during the glacial, and an increase in warm-water species during the interglacial. These patterns are consistent with a cooling in sea surface temperatures (SST) during the glacial period and warming during the interglacial, and with benthic δ¹⁸O values, which were higher in the glacial and lower in the interglacial, reflecting an increase in Northern Hemisphere ice cover during the cold period. Our data, along with previous studies, suggest that MIS 12 in the study region was characterized by severe climatic conditions, with intensified circulation of subpolar surface water masses into the study region and a potential southward migration of the polar front. In contrast, during MIS 11, the climate was warmer, with intensified influence from subtropical surface water masses. Additionally, we observe a significant decrease in paleoproductivity around 430 kyr, coincident with severe SST cooling and peaks in ice-rafted debris (IRD), which could correlate with Heinrich type Event 4 (Ht-4), previously observed in the Iberian margin.
How to cite: González-Martín, M., Rigual-Hernández, A. S., González-Lanchas, A., Balestra, B., and Flores, J. A.: Coccolithophore paleoproductivity variability as a proxy of ocean surface dynamics and climate variability in the Gulf of Cadiz during the Mid-Brunhes Event (MIS 12-11), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8200, https://doi.org/10.5194/egusphere-egu25-8200, 2025.
The Middle to Late Miocene represents an important time interval on a global scale. Due to continental reorganisation in the Indian Ocean (IO) a near-modern monsoonal wind system was established, a series of climatic changes linked to the Middle Miocene Climatic Transition occurred and the subsequent shift of the region dominated by the Westerlies to the north took place during the Late Miocene. However, how these processes and forcing mechanisms interact and affect the surface ocean dynamics in the southern subtropical IO is poorly understood. In this regard, Ocean Drilling Program (ODP) Site 752, located on the west flank of Broken Ridge (30° 53.475ˈS/93° 34.652ˈE), represents a key location to study how the above-mentioned processes may have affected the surface currents in the eastern sector of the subtropical IO during the Middle to Late Miocene.
In order to ascertain changes in the surface ocean conditions and their connection to surface currents dynamics between 7.31 and 16.06 Ma, we evaluated the overall changes in the calcareous nannofossil assemblage at Site 752. For this purpose, we performed a quantitative study on 122 calcareous nannofossil samples (with a temporal resolution of ~60 kyr) and performed statistical analyses to observe variations in the assemblage composition. The UPGMA (Bray-Curtis) clustering ordination analyses revealed a total of 5 clusters (Cluster 1-5), defined at a cut-off distance of ~0.76 and a cophenetic correlation coefficient of 0.75. Additionally, Cluster 5 was divided into two sub-clusters (Cluster 5a-5b), at a cut-off distance of ~0.77.
Cluster 1 indicates high nutrient availability due to the abundance of Reticulofenestra minuta. Cluster 2 also indicates high nutrient supply in the region, as per the high abundance of R. minuta, differing from Cluster 1 by the presence of Calcidiscus leptoporus and Coccolithus pelagicus, both indicative of cold surface waters with a deep mixed layer. Cluster 3 is characterised by the concomitant presence of species typical of warm/cold stratified/mixed regions, such as Discoaster spp., C. pelagicus and R. pseudoumbilicus. Cluster 4 is dominated by Reticulofenestra haqii and Reticulofenestra producta, which thrive in warm and oligo/mesotrophic conditions. Reticulofenestra producta is also abundant in Cluster 5a. However, the high abundances of Reticulofenestra perplexa and R. pseudoumbilicus indicate more moderate nutrient conditions with relatively cold surface waters compared to Clusters 1 to 4. Lastly, Cluster 5b is characterised by an increase in the abundance of R. pseudoumbilicus and the common presence of R. haqii, indicating warmer surface water conditions compared with Cluster 5a.
Temporal progression from Cluster 4 to Cluster 2 over our study interval reflects a distinct shift to higher nutrient palaeoceanographic conditions at the Broken Ridge between 15–8 Ma. This change in surface water nutrient availability can be linked to an invigoration of the Antarctic Circumpolar Current and the Southern Indian Ocean Current at ODP Site 752. These shifts indicate the impact of the Middle to Late Miocene northward migration of the Westerlies (from 40 to 30º S) on mid-latitude paleoceanographic conditions and confirm the proposed shift in global nutrient cycling around 11 Ma ago.
How to cite: Puentes Jorge, X., V. Del Gaudio, A., E. Piller, W., De Vleeschower, D., Hechemer, T., Lyu, J., and Auer, G.: South eastern Indian Ocean (ODP Site 752) paleoceanographic conditions during the Middle to Late Miocene based on calcareous nannofossils assemblages, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10620, https://doi.org/10.5194/egusphere-egu25-10620, 2025.
Marine phytoplankton play a fundamental role in marine ecosystems and are sensitive to changes in ocean temperature and associated ocean properties (such as dissolved CO2 and nutrient availability). Fossil time series recovered from the deep-sea are unique archives of the long-term adaptation and evolution of marine algae with mineralized parts, such as coccolithophores and diatoms. For example, ample evidence exists for long-term compositional overturn and extinctions in marine plankton communities across the Eocene Oligocene transition (EOT; ~34.5-33.7 Ma), when a globally warm and largely ice-free climate shifted to an overall cooler state with major ice sheets on Antarctica. Early studies already highlighted how coccolithophore species compositions and their latitudinal contrasts drastically changed from the late Eocene to the early Oligocene. Here, we revisit these meridional gradients in species composition across a north-south transect in the Atlantic and Southern Ocean, in order to detail the cell size distribution of ancient coccolithophores and to determine the timing of phytoplankton community shifts on a common age scale. Calcareous nannofossil census counts confirm the existence of distinct regional signatures and ecological gradients between sites. Coccolithophore communities in the Southern Ocean stood out with lowest species richness and largest cells, whereas the Atlantic sites hosted more species with smaller cells. A decrease in mean cell size across the EOT was most pronounced in the Southern Ocean, where communities became dominated by medium-sized Reticulofenestra daviesii during the early Oligocene. In the Atlantic, phylogenetically related taxa (small Reticulofenestra spp. and Cyclicargolithus floridanus) increased in prominence in the cooler and glaciated world. The compositional changes and decrease in mean cell size of common taxa are consistent with increased cellular growth rates, major changes in the mixed layer depth and (seasonally) increased nutrient entrainment into the upper photic zone. This is supported by regional gradients in δ13C between surface- and deep-sea carbonates (indicating alleviation of nutrient-limitation) and abrupt increases in siliceous microfossils in the Southern Ocean and equatorial Atlantic sedimentary archives, although the latter may relate to changes in seafloor preservation of silica because of changes in deep water mass properties.
How to cite: Henderiks, J., Bordiga, M., and Bohaty, S. M.: Phytoplankton Communities across the Eocene-Oligocene Transition: A Paleo-Atlantic Meridional Transect, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12328, https://doi.org/10.5194/egusphere-egu25-12328, 2025.
This study examines the paleoenvironmental evolution of the Qom Formation using biostratigraphy and petrography within a sequence stratigraphic framework to figure out spatial and temporal distribution of the depositional characteristics. The upper part of the Qom Formation (members e and f) was deposited in the northern branch of the Tethyan Seaway in the Central Iran Basin, and investigated along the Dochah and Jujukzar sections. Calcareous nannofossils and large benthic foraminifera indicate the succession was deposited during the early to middle Burdigalian in the Central Iran Basin. According to nannofossil assemblages two biozones NN2 (Discoaster Druggii zone) and lower part of NN4 (Sphenolithus heteromorphus zone) of Burdigalian age are identified in both members of the Qom succession. With respect to nannofossil zones, a hiatus (NN3, ca. 19-18 Ma) is recognized, related to erosion. Based on large benthic foraminifera, SBZ25 biozone including Borelis melo curdica (Burdigalian) is recognized in the member f of the Qom Formation. Based on petrography, ten depositional facies were deposited in four facies belts including lagoon, shoal, mid ramp, and basin, propagated in a ramp-type platform in the Qom Basin. Regarding stacking pattern of facies, three 3rd-orderdepositional sequences were formed at the time, driven by relative sea-level changes. Regarding the sequence stratigraphic context, the upper part of the member e and member f are stratigraphically equivalent as evident by biostratigraphic and sedimentary evidence, which has not been investigated in previous studies. This study underscores and evaluates the sequence stratigraphy and sedimentary model of the Qom Basin in a high-resolution scale.
Key words: Qom Formation, Biostratigraphy, Sequence stratigraphy, Tethyan Seaway
How to cite: Sharifi-Yazdi, M., Ćorić, S., and Wagreich, M.: Biostratigraphy and depositional characteristics of the northern part of the Tethyan Seaway (Burdigalian, Central Iran) in a sequence stratigraphic framework, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9166, https://doi.org/10.5194/egusphere-egu25-9166, 2025.
The Cenomanian/Turonian boundary interval was marked by an extreme environmental change coinciding with Oceanic Anoxic Event 2 (OAE 2; ~94 Ma) characterized by global warming, accelerated hydrological cycle, enhanced production and burial of organic matter and high concentrations of CO2. The causes are linked to Large Igneous Provinces (LIPs) activity, which released vast amounts of greenhouse gases into the ocean-atmosphere system as well as toxic metals responsible of altered chemistry and structure of the oceans. Also, the OAE 2 experienced a significant brief period of cooling (ca. 40 kyr) occurred known as the Plenus Cold Event (PCE), firstly identified and described in the Eastbourne section (Sussex, England). In its complex, the OAE 2 represents a key case study to understand the dynamics of oceanic process as well as the response of biota to climate change.
In this work we present data on calcareous nannofossils from the Eastbourne section, which is a reference section for OAE 2, with the general aim to implement our understanding of the effects of OAE 2 perturbation on calcareous nannoplankton. Specifically, 44 samples were analysed for morphometry of Eprolithus floralis and assemblage composition. For each sample nannofossil temperature and nutrient indices were also calculated.
We selected Eprolithus floralis because is a nannolith taxon, heavily calcified and with a reconstructed preference of cooler waters. Previous morphometric investigations focused on coccolith taxa (i.e. Biscutum constans, Discorhabdus ignotus, Zeugrhabdotus erectus and Watznaueria barnesiae) predominantly associated with fertility fluctuations in surface waters.
Results show that E. floralis underwent significant size variations across OAE 2 with a decrease in the total diameter during OAE 2 of ca. 0.5 μm. Minimum sizes are reached in the latest part of OAE 2 (chemostratigraphic peak B), with specimens ca. 1 μm smaller than in pre- and post-OAE 2 intervals.
Two distinct E. floralis morphotypes were separated, one with spiky and one with rounded elements. The latter morphogroup, more abundant during OAE 2, has a relatively smaller (ca. 0.2 μm) total average diameter.
The diaphragm diameter also shows size changes but with opposite trends, thus specimens have larger diameter during OAE 2 except for peak B which is characterized by the smallest values.
Our findings indicate that morphometric fluctuations are unrelated to abundance. Moreover, although E. floralis is as a cold-water species, its abiundance is unrelated to temperature fluctuations across OAE 2, including the PCE.
The main size patterns of E. floralis are partially similar to those of B. constans, D. ignotus and Z. erectus possibly suggesting that common environmental stressors affected all these species. We speculate that also E. floralis used the strategy to reduce the average size to cope with excess CO2 and/or toxic metals. Moreover, we do see a change in the dominance of the morphotypes probably suggesting that those with rounded shape and smaller size were better adaptable to/ less stressed by the OAE 2 perturbation.
How to cite: Bottini, C., Tungo, E., Erba, E., and Fauth, G.: Calcareous nannoplankton response to Oceanic Anoxic Event 2 (Cenomanian-Turonian, Late Cretaceous), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9838, https://doi.org/10.5194/egusphere-egu25-9838, 2025.
As atmospheric carbon dioxide continues to rise at unprecedented rates, it is imperative that we better understand the potential long-term effects of warming on marine communities. Calcareous nannoplankton are likely particularly sensitive to the effects of rising CO2, and as one of the most important groups of mineralizing phytoplankton, their response to climatic change will have a knock-on effect on both marine food web dynamics and biogeochemical cycling.
As calcareous nannoplankton have a rich global fossil record spanning the last ~220 million years of Earth history, it is possible to examine how they were affected by high CO2 conditions in the geological past. These data can then be fed into Earth System Models, allowing for better predictions as to how modern communities might be affected by – and recover from – current global climate change. The earliest Eocene ca. 52 - 56 million years ago (Ma) is an excellent case study as to how the Earth system might respond to ‘worst-case’ climate scenarios. Additionally, as the high CO2 world of the early Eocene was punctuated by transient warming events of different magnitudes and durations, it is possible to examine potential threshold paleoecological responses to warming, as well as the recovery rates following individual events.
Here, we present new high-resolution data documenting changes in early Eocene calcareous nannoplankton community composition from two high-latitude International Ocean Discovery Program (IODP) sites (Site U1553 and Site U1514) in the historically understudied Southern Hemisphere. As well as elucidating how climatically sensitive, high-latitude communities were affected by high CO2 conditions, direct comparison of our data with published lower latitude records will reveal any ocean basin- or region-specific responses to warming.
How to cite: Jones, H. L., Niederbockstruck, B., Kulhanek, D. K., and Röhl, U.: High-latitude paleoecological response to early Eocene warming events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21237, https://doi.org/10.5194/egusphere-egu25-21237, 2025.
Understanding the spatial and temporal changes in phytoplankton assemblages is essential in the context of climate change, due to their impact on carbon burial and the marine food web. Here we investigate the effects of environmental shifts in the Mediterranean Sea on phytoplankton taxonomy and size structure using an AI-based approach. We analyzed two sediment trap series from the northwestern Mediterranean Sea between 2010 and 2018: one in the oligotrophic Ligurian Sea and the other in the Gulf of Lion, a region where deep convection occurs regularly in the winter. We used novel deep-learning protocols for image analysis to generate data for phytoplankton particle fluxes, size distributions, and relative assemblages, with a focus on coccolithophores and diatoms. This automated approach enabled the rapid, high-throughput processing of microscope images, producing a standardized dataset across both time series. Our results show a general decline of phytoplankton fluxes towards the seafloor, mirroring the decrease in vertical mixing that affects the water column. Both sites show a shift towards phytoplankton species associated with stratified and nutrient-depleted conditions, but with contrasting patterns despite their proximity: In the Ligurian Sea, deep-dwelling coccolithophore species become increasingly dominant, while in the Gulf of Lion, summer-associated siliceous species, including large diatoms and silicoflagellates, show an increase. These contrasting trends likely result from differences in nutrient inputs and surface pH changes between the sites. We find that the increasing dominance of smaller phytoplankton in the Ligurian Sea leads to a reduction in carbon burial efficiency, while in the Gulf of Lion, the enhanced contribution of larger diatoms may sustain relatively higher export and burial rates in the future. These findings highlight the heterogeneous responses of phytoplankton communities to the increasing surface temperatures and stratification in the Mediterranean Sea, and their contrasting impact on carbon burial.
How to cite: Godbillot, C., Pesenti, B., Leblanc, K., Beaufort, L., Chevalier, C., Di Pane, J., Durrieu de Madron, X., and de Garidel-Thoron, T.: Contrasting changes in phytoplankton assemblage and size to environmental shifts in the Mediterranean Sea using novel deep-learning protocols, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8949, https://doi.org/10.5194/egusphere-egu25-8949, 2025.
Foraminifera's diverse reproductive strategies contribute greatly to their capacity for evolutionary change and their remarkable success throughout Earth's history. This includes sexual reproduction (where genetic material from two individuals is combined), asexual reproduction (where offspring are produced from a single parent) and multiple fission events, giving them the ability to evolve and thrive over time, and the potential to adapt to new environments, develop new traits and diversify into new species. Previous laboratory studies have consistently shown that foraminifera can each produce a large number of offspring from a single reproductive event, but finding foraminifera during their reproductive phase in nature is a rarity.
Here we report on symbiont-bearing foraminifera of the genus Peneroplis in a reproductive state from two natural sites in the Pacific Ocean that are in the process of releasing their juveniles. Findings of adult Peneroplis parent shells with pre-emergent juveniles contained within the test provided a rare opportunity to examine the range of morphologic variability within a single brood of offspring resulting. The adult specimens were complete and contained numerous calcified megalospheric juveniles. We examined the parental test and the megalospheric juveniles by high-resolution Scanning Electron Microscopy to document the quantity, morphology, and size range of the juveniles and to provide novel insight into the reproductive biology and ontogenetic constraints of P. pertusus. The juveniles are non-uniform and highly heterogenous, varying in size, ornamentation, position of the flexostyle, and extent of test deformations. We also report on morphological features in normal and deformed juvenile tests as displayed in the proloculus and the flexostyle. To test whether the juvenile test deformations are expressed in adults, more than 100 specimens of P. pertusus were examined. Previous studies suggested that juvenile test deformities can be carried through into the adult. Our study shows, however, that test abnormalities among juveniles are not expressed in adults of natural population, indicating that they are either transitioning to normal growth forms or are not viable. The small juveniles ultimately become the proloculus and associated juvenile chamber(s) of adults, features that are used in the taxonomy of some larger foraminifera. Morphological features of juveniles and prolocular size across contemporary populations and among populations through time may be used to infer ecological and paleoecological conditions. Results of this study inform such investigations.
How to cite: Langer, M. R., Trubin, I., Tian, S. Y., and Goldstein, S. T.: Size range, morphotypes, and test deformations in juvenile megalospheres of the symbiont-bearing foraminifer Peneroplis: Windows on evolutionary processes and past environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9929, https://doi.org/10.5194/egusphere-egu25-9929, 2025.
In 2023, Plymouth City Council created the Plymouth Sound National Marine Park. While this declaration carries no conservation status, it is based on the European recognition of the area as a Special Area of Conservation in 2005 by Natural England. Marine Research Plymouth, in collaboration with Plymouth City Council, is promoting research into the development of Plymouth Sound since the Last Glacial Maximum. In 1988, two boreholes were drilled into the palaeo-channel of the River Tamar in the middle of Plymouth Sound. The buried channel, which had been located during a geophysical survey, recorded a succession of gravels, saltmarsh, inter-tidal mud flats and open marine sands: all of which contain diagnostic microfossil assemblages. A comparable succession has been recorded near Jersey in another series of marine boreholes in the base of which there is a peat that has been carbon dated as 8300 years b.p.
The Plymouth Sound and Jersey data record the Holocene rise in sea-level following the Last Glacial Maximum (LGM) (20,000–18,000 years b.p.) when the British-Irish ice sheet extended as far south as the north coast of Cornwall. At the LGM, sea level was 125–130 m below the present day and the coastline was almost at the edge of the Continental Shelf. The amelioration in climate and the Holocene sea-level rise generated the present sub-environments of Plymouth Sound and the other rias in South-West England. The present glacial/interglacial cycle is, however, only the latest of a series of climate cycles, numbering perhaps 20+ over the last 2 million years.
Before, and after, the LGM – when permafrost was extensive in South-West England – the caves of South Devon hosted both a significant megafauna and hominin remains and the combination of this terrestrial palaeontology and the marine (foraminiferal) record makes the area of great significance in understanding the Late Pleistocene and Holocene.
How to cite: Hart, M. and Smart, C.: Plymouth Sound Boreholes: a record of sea level rise in the Plymouth Sound National Marine Park (South-West England, U.K.) since the Last Glacial Maximum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2883, https://doi.org/10.5194/egusphere-egu25-2883, 2025.
The ocean productivity plays a crucial role in the ocean carbon cycle by influencing atmospheric CO2 levels. Although upper water column mixing associated with East Asian monsoon and terrestrial weathering input are the primary sources of surface water nutrients in the northern South China Sea (SCS), their contributions to paleo-productivity changes in the northern SCS during the late Pleistocene remains contentious. This study reconstructs paleo-productivity, East Asian monsoon dynamics, and terrestrial nutrient matter inputs over the past 350kyr, using multiple proxies, including the relative abundance of planktonic foraminifer Globigerina bulloides, sediment TOC content, TOC/TN ratio, the ratio of mixed-layer species to thermocline species, the thermal gradient of the upper water column and δ18Oresidual from International Ocean Discovery Program (IODP) Site U1505. The results reveal a distinct glacial-interglacial cyclicity with higher paleo-productivity attributed to increased terrestrial nutrient inputs and intensified East Asian winter monsoon during glacial lowstands. Furthermore, paleo-productivity exhibits a pronounced ~23 kyr cyclicity and is coupled with enhanced East Asian summer monsoon intensity during periods of low-latitude insolation maximum, suggesting a precession forcing on paleo-productivity via East Asian summer monsoon intensity and insolation maximum.
How to cite: Xu, Y., Li, B.-H., and Cui, Q.: Planktonic Foraminifera Reveal Late Pleistocene Paleo-Productivity Changes in the Northern South China Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2985, https://doi.org/10.5194/egusphere-egu25-2985, 2025.
One of the key questions is how and if large complex reef systems can survive under future climate change scenarios. It is known that during the Middle Miocene, there were extensive reefs across the Indo-Pacific. Since the Middle Miocene was a time of global temperatures and CO2 similar to end-of-century predictions, this is an ideal time interval to study. However, there has been a lack of multi-million-year proxy records from these ecosystems for the Miocene. For the first time, we present an SST record from a site (IODP U1464) near the large Miocene Barrier Reef on the NW Shelf of Australia. In this study, we use biomarkers to reconstruct oceanic conditions and look at the changing environments from a carbonate facies perspective. Our research shows that the reef system might have initiated at temperatures that were close to modern summer values in the region. However, during the height of the Miocene Climatic Optimum, when summer temperatures reached 34°C, the reef system was at its maximum extent. Arid conditions, heat-tolerant corals, and a low local subsidence rate allowed the barrier reef to tolerate the hot summer conditions. When the sea level dropped, and sabkhas covered the site during the Middle Miocene climate transition, cooler SSTs allowed for faster reef growth. However, starting at 12 Ma, higher summer SSTs and increased local subsidence led to the end of the barrier system and the continuous collapse of the reef between 11-7 Ma. This suggests that a reduction in stressing conditions is critical for reef survival in a warmer world. Predictions for rapidly changing oceanic conditions coupled with sea-level rise indicate that future climate change will harm modern large complex reefs, much like during the Late Miocene.
How to cite: Petrick, B., Reuning, L., Schwark, L., Bialik, O., and Pfeiffer, M.: A Miocene Climatic Optimum Tropical Barrier Reef: Combining biomarker and facies analysis to understand conditions of reef survival. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8820, https://doi.org/10.5194/egusphere-egu25-8820, 2025.
The curation of Micropaleontology collection at the Laboratory of Historical Geology and Biogeosciences (HG-BioGeoSci), National and Kapodistrian University of Athens (NKUA), undergoes the auspices of the newly introduced MSc programme in Industrial and Environmental Applications in Micropaleontology (IdEA-M, https://idea-m.com/) at the Department of Geology and Geoenvironment. Originated as ‘Laboratory of Geology and Paleontology’ in 1906, HG-BioGeoSci incorporated micropaleontological collections mainly since the mid ’70s, when Professor Michael D. Dermitzakis established Micropaleontology as an educational discipline in the Greek academic domain. The scope of this project is to create a free access database of all micropaleontological objects stored in the HG-BioGeoSci, not only for educational purposes but also benefiting all interested parties to visit and study the collections. The Micropaleontology collection comprises the main microfossil groups/proxies (nannofossils and coccolithophores, foraminifera, pollen, dinoflagellates and other palynomorphs, ostracods, siliceous microfossils etc.), dated from the Paleozoic to the present day. In terms of geographic distribution, the majority of the micropaleontological items comes from the Greek territory and the broader Mediterranean area as also other locations worldwide, including samples collected by the global deep-sea drilling programs (DSDP, ODP, IODP, ICDP). The material mostly refers to microscope slides, isolated specimens or species assemblages, thin sections, mounted SEM stubs and filtered water samples. Except from the microfossil content, the raw material comprising rock samples, marine and terrestrial core records, surface sediments, sediment traps, as well as sample residues is also documented in a digital database. The database displays a 2 level classification where all different types of microfossils are documented, labeled with a unique Laboratory code and linked to all available data, i.e., lithology/material type, sampling date and methods, preparation date and analysis techniques, biozone/ biostratigraphic assignment, applied biozonal scheme, age, paleoenvironment type, owner, analyst, references list, repository and notes (e.g., field notes, photos, original drawings, derived publications etc.).
Up to now, more than 8.000 calcareous nannoplankton preparations have been entered associated with more than 20.000 entries of sample residues and raw samples, while it is estimated that the total amount of the Micropaleontology collection at HG-BioGeoSci will exceed 130.000 entities.
How to cite: Triantaphyllou, M., Dimou, V.-G., Skampa, E., Kouli, K., Tsourou, T., Kontakiotis, G., Besiou, E., Dimiza, M., Stathopoulou, E., Drinia, H., and Antonarakou, A.: The Laboratory of Historical Geology and Biogeosciences (National and Kapodistrian University of Athens) Micropaleontology collection: a first glance, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11634, https://doi.org/10.5194/egusphere-egu25-11634, 2025.
During the Pleistocene epoch, diatom mat blooming occurred in the global ocean for serval times, particularly during several glacial periods (MIS 14, 12, 6, 4, 2). One intriguing phenomenon related to these blooming is the deposition of Ethmodiscus rex diatom mats in tropical-subtropical oligotrophic marine zones. However, the causal mechanism of this occurrence, known as the " Ethmodiscus rex problem " remains under debate and it is crucial to understand this mechanism. This study investigates the diatom mat core GT01, which was enriched in E. rex and retrieved from the Mariana Trench’s Challenger Deep in the Western equatorial Pacific Ocean. We aim to determine the geological age of the diatom blooming event through AMS 14C dating and to explore the nitrogen source of the diatom bloom using δ13C, δ15Norg, and other proxies, and conduct a semi quantitative assessment of the sea surface productivity status during that period.
By comparing the nitrogen isotope signals and considering the isotopic fractionation effects of diatom biology and remineralization, it is suggested that the main source of nitrogen nutrients for E. rex diatom bursts is subsurface nitrate rather than the "new nitrogen". This viewpoint aligns with the findings of previous biological studies on Ethmodiscus species. Based on the nitrogen nutrient source, there is a further hypothesis that E. rex diatoms may also uptake nutrients such as phosphate concurrently with subsurface nitrate. The carbon isotope signal indicates a significant increase in marine primary productivity during the flourishing of E. rex diatoms. The extensive remineralization of organic matter during deposition, along with the substantial production of respired carbon, may have contributed to the reduction of atmospheric CO2 concentration during glacial periods.
As primary producer in the ocean, diatoms are crucial in coupling nitrogen and carbon cycles in marine ecosystems. Investigating the nutrient sources and productivity of diatom mats is vital for gaining insights into the oceanic carbon and nitrogen cycles. These findings enhance our understanding of global biogeochemical cycles and their broader implications for past marine productivity and climate regulation.
How to cite: Cai, W., Huang, E., Liu, S., and Tian, J.: Glacial-deglacial bloom of giant diatoms in the tropical western Pacific through utilization of subsurface nutrients, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-224, https://doi.org/10.5194/egusphere-egu25-224, 2025.
The Kuroshio is crucial in transporting heat and materials poleward. Its variability interacts with the global climate system and affects local and regional climates. However, long-term Kuroshio variability remains poorly understood, especially during the last glacial time. Here, we use a depth sediment cores recovered from the northern Okinawa Trough to investigate past Kuroshio variability. Radiocarbon results indicate that the recovered cores range in age from modern to ~50 ka. Bottom water temperature on the eastern edge of the trough at a relatively shallow site (~300 mbsl) was stable during the past 12 ka, with little increase during the Holocene. We estimate that this site experience ~60 m sea level rise. Based on World Ocean Atlas data for the site, an increase in depth of 60 m corresponds roughly to a 2˚C temperature decrease. Thus, Holocene warming was likely offset by rising sea level. The results further suggest that the vertical temperature gradient and thus the temperature structure was similar at 12 ka to the late Holocene, probably related to the existence of the Kuroshio main axis since that time.
How to cite: Obrochta, S., Hatakeyama, Y., Oda, S., Sato, S., Wardani, A., Ishendriati, R., Izawa, S., Miyakoshi, Y., Inanobe, T., Kujiraoka, Y., Kubota, Y., Sagawa, T., Takayanagi, H., Yokoyama, Y., and Miyairi, Y.: East China Sea climate and Kuroshio variability since the Last Glacial Maximum, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16502, https://doi.org/10.5194/egusphere-egu25-16502, 2025.
The Ross Sea is a globally significant annual atmospheric CO2 sink and hosts the largest phytoplankton bloom. It is characterized by a shallow carbonate compensation depth (CCD) and crucial water mass transformations. This study investigates the distribution of calcareous foraminifera and microtektites to evaluate carbonate preservation in surface sediments approximately 0.8 million years old.
In the western Ross Sea (WRS), pale-yellow microtektites originating from northern Victoria Land are distributed along the pathway of cold shelf water (SW), influenced by terrestrial input from the Victoria Land shelf. Calcareous benthic and pelagic foraminifera dominate in the central and eastern Ross Sea (CRS and ERS), following the pathways of warm Modified Circumpolar Deep Water (MCDW) and/or Circumpolar Deep Water (CDW). Surface sediments in these regions contain few diatoms and a higher proportion of >125 μm sediment fractions.
In the CRS, foraminiferal assemblages are dominated by Trifarina earlandi, with common occurrences of Ehrenbergina glabra, Globocassidulina biora, and Cibicides spp., along with abundant Neogloboquadrina pachyderma. In the ERS, G. biora dominates, accompanied by E. glabra and N. pachyderma. The Ross Sea’s shallow CCD, ranging from 350–400 m to 500–550 m, coexists with calcareous foraminiferal assemblages in sediments at depths of 400–600 m, suggesting that CCD depth is not the primary factor governing carbonate preservation.
The distribution of calcareous foraminifera aligns with water current pathways, highlighting water temperature as the key determinant of their survival. The temperature of MCDW, modulated by mixing with cold SW, plays a critical role in carbonate preservation.
How to cite: Wang, X.: Interactions Between Water Masses and Carbonate Preservation in the Ross Sea: Evidence from Foraminiferal and Microtektite Distribution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15615, https://doi.org/10.5194/egusphere-egu25-15615, 2025.
Posters on site: Tue, 29 Apr, 10:45–12:30 | Hall X3
Ostracods and foraminifers are often used as proxies to reconstruct paleoenvironments and their changes through time. In this study, they are utilized to give insights on the environmental transitions at the Sarmatian-Pannonian-boundary of the Vienna Basin at which various layers of accumulated ascidian spiculae were previously observed.
A drill core was taken during the expansion of the subway network in Vienna. It originates from the depth range of 38-42 meters below surface which is suggested to represent the transition from the Sarmatian to the Pannonian stages at this location. Selected 5cm segments were extracted from the core and processed. The preparation included wet sieving with 125 and 250µm mesh size. After oven-drying, the remaining sediment was split, and the microfossils were picked. Ostracods and foraminifers were identified using literature and paleoenvironmental changes were inferred based on variations in their assemblages along the core.
Preliminary results reveal distinct patterns in the assemblages of ostracods and foraminifers. At 42m below surface no ostracods and very few foraminifers are present indicating high sedimentation rates. At 40,5m below surface the identified ostracods species belong to Loxoconchidae and Leptocytheridae families and foraminifers belong to the families Elphidiidae and Miliolidae. At 38m below surface no foraminifers are present, and the ostracods belong to Candonidae families which are associated with lacustrine waters.
How to cite: Schmied, N., Berndt, C., Maslo, M., and Heinz, P.: Palaeoenvironment of the Sarmatian-Pannonian boundary in the Vienna Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20071, https://doi.org/10.5194/egusphere-egu25-20071, 2025.
Eocene is one of the most eventful epochs of Earth’s geologic history, ranging from a series of global warming events in the early Eocene (~56-47 Ma) to an icehouse transition at the end of Eocene to Oligocene. Kutch, a pericratonic rift basin at the western boundary of India, hosts thick sedimentary strata with intervening marine deposits of Eocene with hiatus at Lutetian (~47-42 Ma) and Priabonian (~37-33 Ma). Given Kutch's equatorial paleolatitudinal position (~10°S-10°N) during the Eocene, it is particularly interesting to investigate the basin's response to global climatic perturbations. Bulk sediment samples from Naredi (Ypresian), Harudi, and Fulra Limestone (Bartonian) formations are collected at 0.5-meter intervals or at lithological changes, whichever provided a finer resolution. Stable isotope analyses of organic carbon (δ¹³Corg) from the samples are performed. A pronounced negative δ¹³Corg excursion indicative of Eocene Thermal Maximum (ETM2) is recorded from the first fossil-bearing shale beds with the occurrence of larger benthic foraminifera (LBF). The Assilina Limestone Unit, the topmost fossiliferous bed of the Naredi Formation, records the Early Eocene Climatic Optimum (EECO). The top of Naredi and basal Harudi Formation has relatively lower δ¹³Corg values in the range of -24 to -26‰ (VPDB). δ¹³Corg values are relatively higher from the overlying coquina shell beds, and another negative excursion (~1.5‰ VPDB) has been observed concurrently to the Nummulites obtusus bed. This negative excursion is likely linked to the Middle Eocene Climatic Optimum (MECO) warming event. An abundance of other LBFs like Nummulites spectabilis and Nummulites vredenburgi have been noticed at this level. No major shift in the δ¹³Corg profile has been noticed in the overlying carbonate platform deposit of the Fulra Limestone Formation. The limestone is highly fossiliferous, dominated by diverse species of LBF such as Discocyclina, Assilina and Nummulites. This investigation indicates a correlation between sea-level rise and global warming events during the Eocene epoch in the paleo-equatorial Kutch Basin. Elevated temperatures and increased nutrient input during the EECO and MECO fostered the growth and diversification of LBF like Nummulites and Assilina. These warm, nutrient-rich conditions enabled LBF to achieve high diversity, abundance, larger sizes, and an expanded latitudinal range in the middle Eocene, demonstrating their adaptability to global warming. The observed negative δ¹³C excursion in the Naredi and Harudi formations is likely linked to sea-level fluctuations and changes in terrestrial carbon input to the marine environment. This study contributes to a better understanding of the complex interplay between climate change, sea-level fluctuations, and carbon cycling at the Kutch Basin during the Eocene.
How to cite: Chaudhuri, S., Mitra, A., and Claeys, P.: Paleoclimate and paleoenvironmental reconstructions of the Kutch Basin, India, during the Eocene: Insights from geochemical and micropaleontological signatures, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-690, https://doi.org/10.5194/egusphere-egu25-690, 2025.
Foraminifera are benthic microorganisms that are used as environmental proxies due to their sensitivity to changes in their surrounding living conditions. This study focuses on shifts in species abundance and diversity of foraminiferal assemblages from western Florida. This research has explored how Floridian hurricane activity and other related factors, including resuspended sediment contaminants, influenced these shifts. Samples were taken from vibracore PR-30, a sediment core taken along a barrier island, a location particularly vulnerable to hurricane events. These factors have all been analyzed in a comprehensive survey of the foraminifera present and XRF scans of potential contaminants in the sediment. We hypothesized that foraminiferal assemblages would decline in abundance and diversity in response to these factors. The preliminary data from a few of the samples has proven to be consistent in diversity and abundance with small variations between samples. This could suggest a strong resilience and ability to recover in Flordian ecosystems or that this period of time in the sediment had not yet experienced a severe weather event, leaving little data. More data collection and analysis will be necessary to achieve a comprehensive understanding of the vibracore foraminifera and the effects of hurricanes on marine ecosystems. The results of this study will help create a strengthened understanding of ecosystem resilience and recovery. As climatic events intensify, a strong understanding of the resilience of marine ecosystems will be key to understanding the long lasting effects caused by severe weather events.
How to cite: Watson, S., Smith, C., and Dellapenna, T.: An Analysis of Floridian Foraminifera in Past Hurricane Sediment., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1398, https://doi.org/10.5194/egusphere-egu25-1398, 2025.
The Late Pleistocene Szekou Formation in southern Taiwan preserves an exceptional fossil assemblage that includes marine vertebrates, mollusks, and microfossils, which offers a unique peek into the paleo-lagoon environment during a period of rapid tectonic uplift and sea-level fluctuations. Previous studies utilizing sedimentological and lithofacies analyses, fossil assemblages, and stable isotope analyses, suggests a semi-open to open lagoonal system surrounded by barrier islands that provide partial isolation from the open ocean. However, the stratigraphic complexities, inconsistent sampling, and limited dating methods have led to contradictory interpretations and coarse age estimates, with the stratigraphic age roughly constrained between 30,000 and 260,000 years.
Recently, the National Museum of Natural Science's discovery of numerous in-situ preserved cetacean fossils, combined with new core data from the Geological Survey and Mining Management Agency, has provided new chronological evidence to further clarify the paleoenvironmental conditions. We integrated GNSS-based sampling location and elevation data to ensure accuracy. Carbon isotope ratio (δ13C) range from -22‰ to -25‰, while organic carbon-to-total nitrogen ratios (C/N) range between 7 and 29, suggesting C3 terrestrial plants or marine dissolved organic carbon as primary organic matter source(s). Additionally, foraminiferal assemblages indicate that the lagoon's water depth (60 meter) exceeded earlier estimates of 20 meters.
By integrating stratigraphically continuous core materials, stable isotope ratios and foraminifera data, this study reconciles prior discrepancies in paleoenvironmental interpretations of the Szekou formation. It reconstructs the sequential evolution of the Szekou lagoon, from its initial formation to later stages of development, emphasizing the influence of rapid uplift and sea level fluctuations on lagoon-ocean connectivity. Ultimately, this research seeks to contribute to broader understanding of evolution of coastal lagoons during the Late Pleistocene in southern Taiwan.
How to cite: Chen, Z.-D., Yang, T.-R., and Löwemark, L.: Integrating Microfossil and Geochemical Evidence to Refine our understanding of the Paleoenvironmental Evolution of the Szekou Formation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4797, https://doi.org/10.5194/egusphere-egu25-4797, 2025.
Calcareous nannofossils are essential tools for reconstructing palaeoenvironmental conditions and understanding evolutionary trends in plankton organisms during the Late Cretaceous. This study presents a comparative morphometric analysis of the Aspidolithus enormis - parcus group from the Lower Campanian and distant sections of the deep-water Rhenodanubian Supergroup (Loibichl, Eastern Alps, Austria) and the pelagic Smoky Hill Member of the Niobrara Formation (Western Interior Seaway, Kansas, USA). The aim is to refine our understanding of the evolutionary trends within this group, particularly in response to changing palaeoceanographic and climatic conditions.
Morphometric analysis of Aspidolithus taxa in both sections reveals that A. enormis (“small A. parcus”) can be clearly distinguished from A. parcus based on the total length of the coccolith, with a threshold of approximately 8.5 µm. A. enormis consistently exhibits a smaller coccolith size (< 8.5 µm), while A. parcus is characterized by a larger size (> 8.5 µm). However, despite clear size differences between A. enormis and A. parcus, statistical differentiation between the subspecies of A. parcus (A. parcus parcus, A. parcus expansus, and A. parcus constrictus) based on the ratio of central area width to external ring width (b/a) was not observed in either of the studied sections.
Interestingly, both the sections exhibit a similar pattern in which size variation in the b/a ratio correlates with sea surface temperature, with larger central areas associated with higher temperatures.
These findings reinforce the hypothesis that the Aspidolithus group exhibits regional consistency in response to environmental fluctuations, highlighting the applicability of nannofossil morphometry for palaeoenvironmental reconstructions and stratigraphic correlation.
How to cite: Granero Ordóñez, P., Wagreich, M., and Wierzbicki, A.: Morphometric and Palaeoenvironmental Analysis of Aspidolithus (Calcareous Nannofossils): Rhenodanubian Flysch Zone (Eastern Alps, Austria) vs. Niobrara Formation (Kansas, USA), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5844, https://doi.org/10.5194/egusphere-egu25-5844, 2025.
The Middle Eocene Climatic Optimum (MECO) was a global warming period that interrupted the gradual cooling trend of the middle-late Eocene at around 40 Ma. It is characterized by high temperatures, increased pCO2 levels in the atmosphere, and marine carbonate dissolution. Its gradual onset, rapid termination, long duration (500 kyr), and the lack of a global negative carbon isotope excursion clearly differentiate the MECO from other Eocene hyperthermals, making its study of utmost interest to understand the effects of warming on the carbon cycle. Herein, we present the first record of the benthic foraminiferal response to the MECO at abyssal depths, and we reconstruct the paleoenvironmental impact. The Eocene sediment samples from International Ocean Discovery Program Site U1511 in the Tasman Abyssal Plain (Southwest Pacific Ocean) were deposited below the CCD and contain well-preserved agglutinated benthic foraminifera. The foraminiferal assemblages show low diversity values across the whole study interval. The MECO is characterized by the dominance of the opportunistic species Spiroplectammina spectabilis, which points to environmental instability and changes in food availability, likely linked to water column stratification associated with warming. Mineralogical analyses show an increase in smectite content during the MECO, suggesting changes in deep-water sources. These findings are consistent with previously documented changes in ocean circulation and nutrient dynamics in the region during the MECO.
How to cite: Peñalver Clavel, I., Laita, E., Dallanave, E., Sutherland, R., Westerhold, T., Dickens, G. R., Bauluz, B., and Alegret, L.: Abyssal record of Eocene warming in the Tasman Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6986, https://doi.org/10.5194/egusphere-egu25-6986, 2025.
During the Badenian (Langhian-early Serravallian), a diverse biocenosis inhabited the warm marine environments of the epicontinental Central Paratethys Sea. The investigated site in the southeastern part of the Pannonian Basin (North Croatian Basin) provides a unique insight into the palaeoenvironmental evolution of that part of the sea, including changes in water depth, salinity, oxygen, and nutrient levels. A multi-micropaleontological study integrated benthic and planktonic foraminifera, ostracods, calcareous nannoplankton, palynological assemblages, and diversity proxies. This approach encompasses biostratigraphic dating and detailed paleoenvironmental reconstruction.
The studied sediments described a transition from an oligotrophic deeper marine environment, frequently influenced by terrigenous input (river discharge) to shallow marine habitats. A short-lived eutrophication event, likely triggered by high nutrient activity and transport into the marine basin, occurred slightly above the volcanoclastic layer, correlative to dated tuff in the vicinity (14.4 ± 0.03 Ma, Marković et al., 2021). Following the overall shallowing trend, the environment stabilized into a shallow, oligotrophic state.
This research contributes to a refined understanding of the Miocene environmental history of the southern Pannonian Basin, adding more pieces to the puzzle called the evolutionary history of the Central Paratethys. By integrated multiple proxy groups, we aimed to elucidate the timing and character of key environmental changes within this region.
Marković, F.; Kuiper, K.; Ćorić, S.; Hajek-Tadesse, V.; Kučenjak, M.H.; Bakrač, K.; Pezelj, Đ. & Kovačić, M. (2021): Middle Miocene marine flooding: New 40Ar/39Ar age constraints with integrated biostratigraphy on tuffs from the North Croatian Basin. Geologia Croatica, 74(3), 237–252.
ACKNOWLEDGMENTS
This research was conducted in the scope of the internal research project „RAMPA - Development of Miocene paleoenvironments in Croatia and their connection with global events“at the Croatian Geological Survey, funded by the National Recovery and Resilience Plan 2021–2026 of the European Union – NextGenerationEU, and monitored by the Ministry of Science and Education of the Republic of Croatia.
Partly this research was also supported by the internal research project WEGETA – Weathering and vegetation intertwined-multiproxy approach to understand the fate of terrestrial ecosystems in times of global climate change“ at the Croatian Geological Survey, funded by the National Recovery and Resilience Plan 2021–2026 of the European Union – NextGenerationEU, and monitored by the Ministry of Science and Education of the Republic of Croatia and „PYROSKA – Miocene syn-rift evolution of the North Croatian Basin (Carpathian-Pannonian Region): a multi-proxy approach, correlation and integration of sedimentary and volcanic record“ at the Croatian Geological Survey, funded by Croatian Science Foundation, Installation Research projects (UIO-2019-04-7761).
How to cite: Milošević, M., Baranyi, V., Ćosović, V., Hajek-Tadesse, V., Galović, I., and Miknić, M.: Micropaleontological insight into the Badenian Sea from the North Croatian Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8064, https://doi.org/10.5194/egusphere-egu25-8064, 2025.
The carbonate ion concentration ([CO₃²⁻]) in the deep ocean is a key parameter for reconstructing ocean carbonate chemistry and understanding its role in the global carbon cycle. The dissolution of planktonic foraminiferal tests has long been used as a proxy for past deep ocean [CO₃²⁻] variability (Lohmann, 1995; Broecker and Clark, 2001a,b, 2003). However, traditional dissolution proxies, such as size-normalized weight (SNW), have inherent limitations in quantitatively constraining past fluctuations in deep-sea carbonate chemistry. For instance, fossil tests are often filled with sediments, making it difficult to clean them without damaging the original shell. Additionally, the initial size-normalized weight (SNW) values are influenced by ambient environmental conditions (such as the surface water [CO₃²⁻]) during calcification (Barker and Elderfield, 2002; Broecker and Clark, 2004).
To address these limitations, a new quantitative approach has been developed to reconstruct bottom water saturation with respect to calcite (Δ[CO₃²⁻]) using micro X-ray computed tomography (MXCT) to separately evaluate the density of the test surface and interior. This method has been employed to reconstruct ocean carbon storage during the Last Glacial Period (Iwasaki et al., 2022). Δ[CO₃²⁻] represents the difference between the carbonate ion concentration at saturation and the in situ carbonate ion concentration, providing an effective method for reconstructing past carbonate ion levels. This technique enables high-resolution, non-destructive three-dimensional analysis of foraminiferal test microstructures, offering more precise constraints on past ocean carbonate chemistry (Iwasaki et al., 2023; Kimoto et al., 2023).
In this study, we applied MXCT technology at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) to investigate foraminiferal test dissolution patterns in the North Atlantic on orbital timescales. We constructed three-dimensional models of Globigerina bulloides to examine its dissolution processes from the Pliocene to the Pleistocene. Previous dissolution experiments have shown that the inner calcite of G. bulloides dissolves selectively, and dissolution intensity can be evaluated using CT histogram patterns (Iwasaki et al., 2015). Our research results are consistent with previous studies showing that as shell dissolution progresses, the shape of the CT value histogram shifts toward a bimodal distribution. These findings contribute to improving alternative dissolution-based proxies and enhancing our understanding of the oceanic carbonate system’s response to climatic and oceanographic changes.
How to cite: Lee-Takeda, S., Iwasaki, S., Kimoto, K., Harada, N., and 395 Science Party, I. E.: Micro X-ray CT Scanning of planktonic foraminifera tests (Globigerina bulloides) for Paleoceanographic reconstructions of ocean carbonate chemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10772, https://doi.org/10.5194/egusphere-egu25-10772, 2025.
During the Cenomanian, one of the largest transgressions took place in the southern Tethys, where huge sequences of calcareous sediments were deposited on a wide platform. In Israel, the Cretaceous Judea Group is the most lithologically diverse and least studied in terms of the calcareous nannofossils. Three sections of the Kefar Shaul Fm. in the Judea Mts and CT2 borehole in Mt Carmel area were selected for the palaeocological reconstruction of the Albian-Cenomanian basin.
The 237.6 m deep borehole CT2 (32.7°N 34.98°E) penetrates the Yagur (dolomite), Isfiye (dolomitised chalk), Tavasim Tuff and Arqan (micritic carbonates, chalk) formations, which have been probed at 2 m intervals, with 97 samples for palaeoecological analysis. The Kefar Shaul sections (31°44'42"N 35°08'13"E; 31°45'12"N 35°07'16"E; 31°35'23"N 35°23'56"E) are represented by soft light yellowish very clayey marls and argillaceous limestones (~30 m); 40 samples for biostratigraphic and palaeoecological analysis have been taken at 0.3–1 m intervals.
The entire succession of borehole CT2 belongs to (sub)zones NC9b, UC0a–b (all Upper Albian), UC0c (Upper Albian – Lower Cenomanian), UC1, UC2 (Lower Cenomanian), and UC3 (Middle – Upper Cenomanian).
In the combined Kefar Shaul section of the Jerusalem Area, Subzone UC3d (Upper Cenomanian), undivided interval of Subzone UC3e – Zone UC4 (Upper Cenomanian) and Subzone UC5a (Upper Cenomanian) are recognized.
The quantitative analysis of nannofossils suggests that the general dominance of Watznaueria spp. throughout the whole successions in the Carmel and Jerusalem areas points to quite warm, open marine or coastal, generally oligotrophic conditions. Due to poor nutrient supply, the productivity of the calcareous nannoplankton was quite low. Low values of the Shannon index, Evenness and Species richness can be interpreted as reflecting unstable environment.
In the Carmel area, the Upper Albian Isfiye Fm. accumulated under temperate, oligotrophic conditions. The lower part of the Arqan Fm. (Upper Albian) was deposited under temperate climate but mesotrophic conditions. The higher (Lower Cenomanian) part of the Arqan Fm. was deposited in oligotrophic waters and relatively warm climate. The uppermost (Middle–Upper Cenomanian) part of the Arqan Fm. was accumulated during a progressively cooling period, yet characterized by alternating warming and cooling phases and oligotrophic conditions.
In borehole CT2, the Oceanic Anoxic Event 1d is recorded in the Isfiye Fm. and Middle Cenomanian Event I is detected in the Arqan Fm.; both datums corroborate well with the globally recorded carbon isotopic anomalies. The oxygen isotope analysis suggests temperate (~26°C) conditions during the Late Albian–Early Cenomanian followed by warming in the late Early Cenomanian, with temperatures gradually increasing to ~32°C towards the Middle Cenomanian.
The Kefar Shaul Fm. corresponds to the upper part (Middle–Upper Cenomanian) of the Arqan Fm. in the Carmel area and reflects oligotrophic conditions with mesotrophic phases, during a progressively warming period with episodes of cooling. The oxygen isotope data indicate approximate temperatures of 29–33℃ for the Late Cenomanian. The Kefar Shaul Fm. probably represents the deepest open marine facies of the Judea Group.
The project is supported by the Israel Ministry of National Infrastructure.
How to cite: Ovechkina, M.: Calcareous nannofossils and stable isotopes as proxies for understanding paleoenvironmental evolution of the Levant Basin during the Albian–Cenomanian, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12449, https://doi.org/10.5194/egusphere-egu25-12449, 2025.
Singapore is a highly urbanized country, where much of its natural coastline has been modified to protect against erosion and rising sea levels. While coastal developments play a crucial role to safeguard against sea level changes, they can significantly affect the coastal dynamics and ecological health of the coastal environments. To assess and monitor the impact of urbanization and environmental changes on these coastal systems, foraminifera serve as valuable environmental indicators. Here, we collected 20 surface sediment samples over a year period from five study sites of Singapore and Johor Straits to characterise the foraminiferal assemblages and sediment composition of different coastal environments (e.g., highly engineered coastlines, sandy beach). Foraminiferal assemblages show strong relationship with sediment type and organic content. In the Johor Strait, where sediments are predominantly muddy with higher organic content, there is a low diversity assemblage dominated by agglutinated taxa (e.g., Ammobaculites sp.). Conversely in the Singapore Strait, where sediments are generally coarser with lower organic content, there is a high diversity assemblage dominated by calcareous taxa (e.g., Elphidium sp.). This study presents important baseline data to understand the coastal dynamics and for environmental monitoring in Singapore, and therefore, help provide a framework for interpreting past coastal and climatic changes and inform coastal management decisions in the face of urbanization and warming climate.
How to cite: Yan, Y. T., Chua, S., Nugraha, A., Lai, I., Siek, K., Horton, B., and Switzer, A.: Linking foraminiferal distribution to coastal dynamics in Singapore, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14574, https://doi.org/10.5194/egusphere-egu25-14574, 2025.
Shenmihu is a lake in northeastern Taiwan at an elevation of approximately 1100 meters, marking the boundary between broadleaf and coniferous forests. Pasania currently dominates the surrounding vegetation. This study aims to reconstruct environmental changes in the Shenmihu catchment over the past 10000 years during the Holocene through pollen analysis. Because plants produce pollen, which is often preserved in sediments, pollen analysis is a crucial proxy for investigating how vegetation distributions have responded to shifts in climate and human agricultural activities.
The results show that, although Pasania generally dominates the region, Alnus populations increased between 4900 and 900 cal BP, becoming the main species from 3500 to 1400 cal BP. This shift was likely driven by cooler climates and significant disturbances, such as typhoons that triggered landslides. These findings underscore the importance of climate fluctuations and extreme weather events in shaping local vegetation over time. Additionally, human agricultural activities likely played a role in altering plant communities, illustrating the complex interplay between natural and anthropogenic factors.
To understand broader regional trends, pollen data from Shenmihu were compared with records from Cuifeng Lake and Retreat Lake, both located in northeastern Taiwan. Through this comparative approach, the study aims to document past climate fluctuations in northeastern Taiwan and assess how vegetation distribution evolved throughout the Holocene.
How to cite: Chen, X.-A., Löwemark, L., and Wang, L.-C.: Holocene climate fluctuations and vegetation dynamics in northeastern Taiwan reconstructed through pollen analysis from Shenmihu Lake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14824, https://doi.org/10.5194/egusphere-egu25-14824, 2025.
The Miocene Climatic Optimum (MCO) represents a climate period characterized by lower ice volumes and temperatures that were 3-4°C warmer than today. Indian Ocean Sub-Antarctic Mode Water (SAMW) is primarily formed south of 30°S and is the main return path for deep waters to the surface, migrating and intermixing northwards at Intermediate Water (IW) depths. The modern SAMW transports nutrients into the lower latitudes, strongly impacting mid- and low latitude productivity. During warmer climates, decreasing sea ice may increase nutrient trapping in the Southern Ocean, reducing the nutrient flux through SAMW into the lower latitudes. To better understand trajectories of nutrient fluxes in future climate change scenarios studies in past warm climate analogues of the near future – such as the MCO – are necessary. Thus, we use Ocean Drilling Project (ODP) Site 752, located on Broken Ridge in the southeastern Indian Ocean at a water depth of 1086.3 m, as a key location for understanding changes in IW conditions.
This study aims to reconstruct paleoenvironmental conditions and bottom-water oxygenation at ODP Site 752 during the Middle to Late Miocene (15-8 Ma) using benthic foraminifera assemblages as a proxy for bottom-water-oxygenation and the enhanced Benthic Foraminifera Oxygen Index (eBFOI) for calculating dissolved oxygen content. We combine these assemblage data with Mg/Ca ratios of Cibicidoides wuellerstorfi and Cibicidoides mundulus as a proxy for bottom water temperatures (BWT). For reconstructing sea surface temperatures (SST), and temperatures from the open ocean thermocline, the Mg/Ca data were additionally gathered on the foraminifera species Globigerina bulloides (SST) and Globorotalia menardii (thermocline). We aim to analyze temperature variability through the water column to investigate influxes from cooler water bodies by increasing SAMW intensity and compare our new temperature data with our benthic foraminiferal assemblages. Therefore, we provide novel insights into Late Miocene IW circulation changes and deep water mass variation with the progressive northward shift of the Subantarctic Tropical Front (SAF).
We present a high-resolution record of benthic foraminifera, tracing paleoenvironmental changes in deep water masses in addition to IW variation in the southeastern Indian Ocean. After the MCO, benthic foraminifera assemblages, and respectively the eBFOI indicate a relatively high oxic environment. Starting around 11 Ma, we first detect an increase of dysoxic conditions and deep infaunal foraminifera, e.g. the genus Bolivina spp., with minimal variation in the dissolved oxygen content of the bottom water. Such an assemblage shift is contemporary with increased current winnowing following the northward migration of the SAF. Furthermore, the higher abundance of epiphytic species Cibicidoides wuellerstorfi and Lobatula lobatula, and also Vulvulina pennatula as an elevated epifauna, support an increase in bottom current energy at Broken Ridge from 15 to 11 Ma. Combined, our assemblages and Mg/Ca paleotemperature data suggest that the strengthening of the SAMW and Antarctic Intermediate Water formation in the Late Miocene, since about 11 Ma, resulted in notable changes in bottom water conditions at Broken Ridge, including the increase of current winnowing.
How to cite: Hechemer, T., E. Piller, W., Puentes-Jorge, X., Hauzenberger, C., Petersen, J., Grunert, P., V. Del Gaudio, A., De Vleeschouwer, D., M. Bialik, O., Drury, A. J., Christensen, B., Lyu, J., and Auer, G.: Benthic foraminifera as paleoceanographic tracers in the southeastern Indian Ocean during the Middle to Late Miocene: New insights from ODP Site 752, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15159, https://doi.org/10.5194/egusphere-egu25-15159, 2025.
The Mid-Cenomanian Event (MCE) was a period of significant climatic and oceanographic perturbation, marked by a global carbon isotope excursion (CIE) and ecological shifts in marine systems. Current evidence from macrofauna and neodymium isotopes highlights increased Boreal influences in northwest European epicontinental seas during this interval. Here we use calcareous nannoplankton from the Lydden Spout section (Dover, east Kent, United Kingdom) to reconstruct the surface water conditions and evaluate their response to MCE. We found a notable increase in the high productivity taxa Biscutum constans and small Zeugrhabdotus spp., coinciding with the double-peaked CIE that characterises the MCE. The most significant changes in the productivity and stratification indices also occur at these CIE levels, suggesting enhanced nutrient availability, possibly driven by intensified upwelling or terrestrial nutrient runoff. A relative decline in the generalist taxon Watznaureia barnesiae underscores reduced water column stratification. This change in surface water nutrient dynamics and stratification is also evident in planktonic foraminifera, which show the disappearance of thermocline-dwelling oligotrophic rotaliporids for the duration of the CIE and emergence of meso-eutrophic taxa (Petrizzo and Gale, 2023).
The nannofossil temperature indices indicate transient warming maxima immediately preceding and midway through the MCE (between the two CIE peaks), a short cooling interval just above the MCE onset and a step down to cooler conditions from the upper MCE. The cold-water species Repagulum parvidentatum increased to higher levels and then peak values coincident with the two CIE maxima, and a second cold water/high latitude specialist, Seribiscutum primitivum has a consistent first appearance coincident with the lower CIE peak and persists until just after the event termination. This surface water cooling is also indicated by bulk sediment δ¹⁸O records showing episodes of cooler sea surface temperatures (SSTs; Petrizzo and Gale, 2023), which coincide with precession-paced high-amplitude cooling cycles during the low to mid-MCE. Additionally, the occurrences of Boreal-affiliated macrofossil taxa, such as the belemnite Praectinocamax and the bivalves Chlamys arlesiensis and Oxytoma seminudum, are interpreted as marking the incursion of cooler Boreal waters into the proto-Atlantic during this interval (Gale and Kennedy, 2022).
Our analysis suggests that orbital forcing, and particularly precession and eccentricity cycles, played a significant role in modulating climatic and oceanographic conditions during the MCE. Orbital forcing, particularly 100 kyr and 405 kyr eccentricity cycles, modulated carbon cycle, climatic, and ecological changes, with precession-driven variations influencing terrigenous input and productivity. The interplay between orbital forcing and nannoplankton diversity further supports the influence of orbital pacing on the carbon cycle. The 405 kyr eccentricity maxima correspond with minima in nannoplankton diversity and communities indicative of cooler SSTs and higher productivity. This suggests that eccentricity maxima were associated with enhanced nutrient availability, fostering increased primary productivity and communities dominated by fewer opportunistic taxa, resulting in lower overall diversity. These findings highlight the complexity of climatic and oceanographic dynamics during the MCE, revealing transient cooling episodes that disrupt the predominantly warm conditions of the Cenomanian.
How to cite: Tangunan, D., Bown, P. R., Gale, A. S., Petrizzo, M. R., Witts, J. D., and Twitchett, R. J.: Orbitally driven nannoplankton evidence of surface ocean cooling and productivity in the Late Cretaceous greenhouse world , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17546, https://doi.org/10.5194/egusphere-egu25-17546, 2025.
During the Miocene, a huge (~1 million km2), long-lived (~10 myr) aquatic environment, the so-called Pebas System (Hoorn et al., 2010), existed in Western Amazonia, which is known for its highly diverse and endemic mollusk and ostracod faunas (Gross et al., 2014; Nuttall, 1990; Purper, 1979; Wesselingh, 2006). In the latter group, the asymmetrical-shelled genus Cyprideis is the most relevant, both in terms of abundance and number of endemic taxa, generating a flock of species in the Pebas System (Gross et al., 2014; Whatley et al., 1998). Although the understanding of certain aspects of this flock, such as taxonomy, has improved in recent years, the mechanisms responsible for this speciation remain elusive. In this study, we focus on a peculiar feature of the Cyprideis species flock, as about one-third of its species have a ‘reversed’ hinge and valve overlap compared to what is typical for the genus.
Several outcrops (Marañón Basin, Peru) and boreholes (Solimões Basin, Brazil) yielded abundant and well-preserved material of some little known species (Cyprideis caraionae Purper & Pinto, 1985, Cyprideis krsticae Purper & Pinto, 1985 and Cyprideis retrobispinosa Purper & Pinto, 1983) with complete ‘populations’ (males, females and juvenile stages) within the samples, allowing us to understand the variation of these species over a broad temporal span (~16-13 Ma). Our analyses demonstrate that the development of a shell reversal from previous ‘normal’ shelled Cyprideis species is an effective mechanism for reproductive isolation of the populations, and hence, of sympatric speciation in the Pebas biome.
How to cite: Salazar Rios, A., Gross, M., Zamudio, M. B., and Piller, W. E.: The reversal of valve overlap in Cyprideis (Ostracoda, Crustacea) as a mechanism for sympatric speciation in the Pebas System (Miocene) of Western Amazonia , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18723, https://doi.org/10.5194/egusphere-egu25-18723, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot 2
EGU25-11788 | ECS | Posters virtual | VPS26
Environmental changes since 39 ka reflected by diatom in core sediments from Dongzhaigang Harbor, Hainan IslandWed, 30 Apr, 14:00–15:45 (CEST) | vP2.10
EGU25-7029 | ECS | Posters virtual | VPS26
Investigation of shallow-water carbonate distributions related to the QomFormation in distant sections of the type area, southeast of Kerman, Iran: insight to calcareous nannofossilsWed, 30 Apr, 14:00–15:45 (CEST) | vP2.11
Calcareous nannofossils are essential for age dating and studying environmental changes. These microscopic (1–20µm) calcitic cell-wall fossils coverings are abundant in most post-Paleozoic marine sedimentary rocks, providing a continuous stratigraphic record of biotic change. This study aims to document the stratigraphic occurrence of calcareous nannofossils at the wide-spread shallow marine carbonates of related to the Qom Formation in the Nargesan, Band, and Qaleh-Gabri sections, southeast of Kerman province (East of Central Iran Basin). Samples were collected at 50-100cm intervals from the marly parts of the section to basal part of the Upper Red Formation. To preserve the small-sized coccoliths, samples were processed using simple smear slide method. The prepared slides were examined with an Olympus BX53 light microscope using cross-polarized light at a magnification 1500-2000X. Gypsum and Quartz plates were used to identify various species. In this study employed the standard calcareous nannofossil zonation by Martini 1971 for the Oligocene sediments. The studied interval ranges from the Lowest Appearance (LA) of Sphenolithus ciperoensis species to the Highest Appearance (HA) of the Sphenolithus distentus, corresponding to the NP24 zone defined by Martini 1971. The calcareous nannofossil assemblages exhibit moderate diversity and frequency, with moderately to well-preserved nannofossil specimens observed, such as: Sphenolithus ciperoensis, Sphenolithus conicus, Sphenolithus moriformis, Zygrhablithus bijugatus bijugatus, Helicosphaera recta, Helicosphaera euphratis, Reticulofenestra bisecta, Reticulofenestra dictyoda, Reticulofenestra minuta, Cyclicargolithus floridanus, Cyclicargolithus abisectus, Coccolithus pelagicus, Braarudosphaera bigelowii, etc. According to the above-mentioned calcareous nannofossil assemblages, the age of late Rupelian can be assigned for the studied samples from the surface sections. Furthermore, the high-resolution study of calcareous nannofossils indicates a significant decrease in the abundance and diversity of Oligocene nannofossils, mirroring trends observed at other low and middle latitudes sites. This record of calcareous nannofossils and bioevents provides valuable insights into the paleoenvironments of thatperiod. This research marks the first report of nannofossils from shallow-water carbonates (related to the Qom Formation) from Jiroft-Kerman area.
References
Martini, E. (1971) Standard Tertiary and Quaternary Calcareous Nannoplankton Zonation. Proceedings of the 2nd Planktonic Conference, Roma, 1970, 739-785.
How to cite: kiani shahvandi, M., Parandavar, M., and Heinz, P.: Investigation of shallow-water carbonate distributions related to the QomFormation in distant sections of the type area, southeast of Kerman, Iran: insight to calcareous nannofossils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7029, https://doi.org/10.5194/egusphere-egu25-7029, 2025.
