A recently cored 49-m-thick succession of Early to early Late Aptian age from Garbsen, a small city 6 km northwest of Hannover, has been studied with respect to sedimentology, bulk organic geochemistry and biostratigraphy.

The basal 14 m cover an alternating paper shale-mudstone sequence (topmost Hoheneggelsen Formation) with a 2.3-m-thick “Fischschiefer” bed at the top. It is overlain by partly reddish-colored hemipelagic marlstones representing lithostratigraphically the Sarstedt Member, formerly also named Hedbergella Marls. The “Fischschiefer” is considered to represent the local expression of the global Oceanic Anoxic Event 1a in the Lower Saxony Basin. During Early Cretaceous times the Hannover area represented paleogeographically the eastern-central part and, thus, the depocenter of the Lower Saxony Basin.

In addition to detailed lithological data, we present high-resolution δ¹³C_org, CaCO₃ and TOC data as well as a calcareous nannofossil biostratigraphy for this Boreal Aptian succession. This new core complements other records in the western part of the basin (Alstätte, Bottini et al., 2012) as well as southeast of Hannover (Hoheneggelsen KB9, Heldt et al., 2012) and, due to its completeness, provides new insights in the transition from the “Fischschiefer” deposit to the hemipelagic marlstone sedimentation.

References:

Bottini, C., Mutterlose, J., 2012. Integrated stratigraphy of Early Aptian black shales in the Boreal Realm: calcareous nannofossil and stable isotope evidence for global and regional processes. Newsl Stratigr 45, 115–137. doi:10.1127/0078-0421/2012/0017

Heldt, M., Mutterlose, J., Berner, U., Erbacher, J., 2012. First high-resolution δ¹³C-records across black shales of the Early Aptian Oceanic Anoxic Event 1a within the mid-latitudes of northwest Europe (Germany, Lower Saxony Basin). Newsl Stratigr 45, 151–169. doi:10.1127/0078-0421/2012/0019

How to cite: Bornemann, A., Blumenberg, M., Erbacher, J., Koch, R., and Lippmann, R.: A new extended record of Lower to lower Upper Aptian deposits in Northern Germany – new insights in the Boreal Oceanic Anoxic Event 1a, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4007, https://doi.org/10.5194/egusphere-egu24-4007, 2024.

The Fish Canyon tuff sanidine (FCs) is the most widely used standard in ⁴⁰Ar/³⁹Ar geo­chronology. Its age is determined either through intercalibration with astronomical or U/Pb dating, as intrinsic uncertainties in the K-Ar dating method are too large to provide a “primary”  FCs age. Hence, this age is not only critical for ⁴⁰Ar/³⁹Ar dating, but its determination also guarantees the intercalibration of the 3 main dating methods used to construct our standard geological time scale so that they produce the same age for the same event.In 2008, Kuiper and others published an astronomically calibrated age of 28.201 ± 0.046 Ma that apparently settled the debate as demonstrated by its subsequent incorporation in GTS2012. Yet, this age has been challenged by later studies that used various approaches, leading again to a ~1.5% age scattering. This ongoing uncertainty hampers the construction of a uniform and coherent time scale that is key to modern high-resolution, multi-disciplinary studies in Earth history.

Here we combine 1) a re-examination of the astronomical tuning on which the FCs age of 28.201 Ma is based, 2) a statistical analysis of this tuning using a quantitative record and 3) new single crystal U/Pb zircon ages of the FCT and K/Pg boundary with 4) an in-depth literature review. The re-examination and statistical analysis show that the original tuning is correct and that alternative tunings consistent with different FCs ages are less plausible. Our new U/Pb ages are also in agreement with this FCs age. Finally, this outcome is consistent with studies that use single crystal ⁴⁰Ar/³⁹Ar sanidine and/or U/Pb zircon dating of usually astro­nomically dated volcanic beds and magnetic reversals of Cretaceous to Quaternary age.

Alternative astronomical calibrations that are substantially younger may have suffered from less reliable radio-isotopic ages and/or uncertainties in the astronomical solution and the tuning to this solution. Recent progress in astronomical dating of the K/Pg boundary further suggest a ~100-kyr younger age, but boundary ages based on the 3 main dating methods remain inconsistent. An older FCs age based on statistical optimization may result from the inclusion of ⁴⁰Ar/³⁹Ar-U/Pb data pairs that do not follow Earthtime protocols, but is in itself an elegant approach to tackle both decay constants and standard issues.

In summary the fundamental issue of the FCs age has still not been solved but consensus is being reached on an age close to 28.2 Ma. We therefore recommend the continued use of the astronomically calibrated age of 28.201 ± 0.046 Ma; this recommendation is in line with the recent decision to adopt this age again in GTS2020. However, we endorse further investigation in a community-based effort, where new data and improved methodologies may lead to better insight into fundamental properties and a slightly different age of the standard. This effort will also reveal whether lternative approaches, such as statistical optimization or direct U/Pb FCT zircon dating, may provide an even more accurate and precise FCs age.

How to cite: Hilgen, F., Kuiper, K., Condon, D., Sahy, D., Sierro, F. J., Toorenburgh, Z., Wotzlaw, J.-F., and Zeeden, C.: Re-evaluation of the astronomically calibrated FC sanidine age, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8094, https://doi.org/10.5194/egusphere-egu24-8094, 2024.

The middle Nama Group, deposited during the late Ediacaran in southern Namibia, is a 1 km-thick mixed carbonate-siliciclastic shallow-marine succession that displays observable regularity in its weathering profile. However, the possible role of astronomical climate forcing in this succession remains poorly understood. As a first step to understand the origin of the regularity, an initial cyclostratigraphic framework was developed using Google Earth satellite images and published U-Pb zircon ages of volcanic ash beds. Although the estimated average periodicity of 120-180 k.y. for the dominant scale of variation falls within the frequency band of astronomical forcing, it is not yet possible to discriminate between an origin related to short (~100 k.y.) eccentricity or 173 k.y. obliquity amplitude modulation. In order to refine the framework, we generated high-resolution quantitative records of the weathering profile based on drone photogrammetry. Spectral analysis on the depth series of slope steepness reveals significant spectral power related to the dominant variation at a scale of tens of meters. Additionally, it captures spectral power related to smaller-scale variations at less than 10 m. For age control, the depth series are linked to published U-Pb ages as well as to newly collected volcanic ash samples more closely tied to the analyzed sections. New high-precision dates will be crucial to determine the astronomical origin of these cycles.

How to cite: Spiering, B., Zwarts, M., Bissick, A., Boscaini, A., Davies, J., Halverson, G., Gibson, B., Laflamme, M., and Hilgen, F.: Cyclostratigraphy of the Ediacaran Nama Group in Namibia based on photogrammetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11593, https://doi.org/10.5194/egusphere-egu24-11593, 2024.

Radiometric dating methods are indispensable tools for providing a common and precise timescale for different paleo-environmental archives and their climate records. The cosmogenic radionuclides ²⁶Al and ¹⁰Be decay with half-lives of 0.7 Ma (²⁶Al) and 1.4 Ma (¹⁰Be), respectively, allowing radiometric dating of climate archives far beyond the range of ¹⁴C (t_1/2=5730 a) and ²³⁰Th (t_1/2=75 ka).
While ¹⁰Be has become a common tool in marine geology, ²⁶Al has been studied significantly less. Low atmospheric ²⁶Al production rates and high stable ²⁷Al concentrations result in very low ²⁶Al/²⁷Al ratios, often near the detection limit of accelerator mass spectrometry (AMS). However, with its half-life of 0.7 Ma ²⁶Al would be perfectly suited to bridge a gap of the currently available radiometric dating methods and may allow for constructing better age models in the 1-3 Ma range. Recently, new developments in the field of AMS enable measurements of low ²⁶Al/²⁷Al ratios by isobar suppression using selective photodetachment via ion laser interaction (ILIAMS at University of Vienna). We use these advances to study ²⁶Al/²⁷Al of globally distributed core-top marine sediments. In combination with the corresponding ¹⁰Be/⁹Be we can now assess the spatial variability of authigenic ²⁶Al/²⁷Al and ²⁶Al/¹⁰Be in core-top marine sediments as an important premise for the use of ²⁶Al as a dating tool. Based on these measurements we are able to identify suitable locations for further studies on the behaviour of ²⁶Al/²⁷Al and ²⁶Al/¹⁰Be during deposition in the sediment.

Ackn.: Parts of the measurements were supported by the RADIATE project from the EU Research and Innovation programme HORIZON 2020 under grant agreement No 824096. Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden-Rossendorf e. V., a member of the Helmholtz Association.

How to cite: Lausecker, M., Wieser, A., Marchhart, O., Koll, D., Lachner, J., Merchel, S., and Adolphi, F.: Towards dating marine sediments using 26Al, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11631, https://doi.org/10.5194/egusphere-egu24-11631, 2024.

The late Quaternary stratigraphy and depositional history at the eastern Yellow Sea shelf was studied using a dense network of high-resolution, single-channel seismic reflection profiles and sediment data. The shelf deposits in this area consists of six seismic units formed since the LGM. During the LGM, the study area was completely exposed, resulting in subaerial erosion associated with paleo-channel incision by the Huanghe and Korean Rivers. As the shelf was flooded, the incised channels were backfilled fluvial or coastal sediments, forming incised channel-fill deposits (SU1). The paleo-river may have supplied abundant terrigenous sediments to the study area around the paleo-river mouth and adjacent area. These sediments were trapped within the paleo-estuary and formed SU2, regarded as an estuarine deposit. Two types of serial sand ridges (SU3 and SU5) which correspond to transgressive deposits developed. SU3 on the southern part (80~110 m deep) is regarded as a moribund-type mainly formed during the early to middle stage of transgression. These are thought to have ceased growing and remobilizing. In contrast, SU5 (occurring 30~50 m deep off the Korean Peninsula) is generally regarded as active sand ridges deposited during the late stage of transgression and is partly modified by modern tidal currents. As the transgression continued, the near-surface sediments were reworked and redistributed by shelf erosion, resulting in a thin veneer of transgressive sands (SU4). The uppermost unit (SU6) formed the Heuksan Mud Belt (HMB), which is one of the most prominent mud deposits in the Yellow Sea. The lower part of the HMD corresponds to shelf-mud deposited during the late stage of transgression, whereas the upper part consists of a recent shelf-delta developed after the highstand sea level at about 7 ka BP. 

How to cite: Yoo, D.-G., Hong, S.-H., Lee, G.-S., Kim, G.-Y., and Choi, Y.: Sequence stratigraphy based on high-resolution seismic profiles in the late Pleistocene-Holocene deposits of the eastern Yellow Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13252, https://doi.org/10.5194/egusphere-egu24-13252, 2024.

Bayhead delta is one of the links between fluvial and estuarine system where terrestrial sediments are prograding into the estuary. Despite the critical position of the bayhead delta, the Holocene reconstructions of coastal linkage area are poorly documented based on bayhead delta data from direct cores. This study provides sedimentary characteristics, stratigraphic interpretations, and also a new concept of a full-filled bayhead delta. Five cores are acquired in the Nakdong valley fills consisting of late Pleistocene to Holocene deposits. Sixteen facies are defined and grouped into eight facies association; alluvial plain, fluvial channel and floodplain, oxidized fluvial channel, tidal flat, tidal bar, central basin and bayhead prodelta, bayhead delta front, and bayhead delta plain. The associations are compiled up three depositional units in the Nakdong valley fills: Unit 1, 2, and 3. Unit I consists of alluvial plain and fluvial channel in the lowermost part of cores. Unit II contains tidal flats, tidal bars, and central basin in an estuarine environment adjacent to Unit I. The topmost Unit III is bayhead delta deposits consisting of bayhead delta plain, bayhead delta front, and bayhead prodelta after the depositions of Unit II. Age data for the Nakdong valley fills, suggest that these depositional environments developed in depositional stages (before about 12 ka, 12 and 9 ka, 9 and 7 ka, 7 and 5 ka, 5 and 3, and after 3 ka). The sequence stratigraphy of the Nakdong valley fills can be divided into three systems tract; a lowstand systems tract (LST), a transgressive systems tract (TST), and highstand systems tract (HST). The uppermost deposits of the Nakdong valley show a bayhead deltaic succession string imprint of fluvial processes in an embayed environment. Most bayhead deltas are limitedly developed within the head of the estuarine systems, whereas the Nakdong deltaic deposits fully filled in the estuary system. This full-filled type is interpreted to represent that the relative rate of fluvial sediment input exceeds the rate of local accommodation creation. 

How to cite: Hong, S.-H., Ryang, W. H., Yoo, D.-G., and Kimg, J. C.: Reconstruction of bayhead delta in response to the Holocene sea-level changes in confined morphology, the Nakdong valley fill, southeastern Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13499, https://doi.org/10.5194/egusphere-egu24-13499, 2024.

Sand ridges are more developed around the continental shelfs with the strong tide current. Various sand ridges are distributed in the continental shelf of the South Sea, Korea. The deep core samples from the sand ridges of South Sea were collected and analyzed to characterize physical property with sedimentary depth. Laboratory analysis (compressional velocity, physical properties, and grain size) was conducted on core samples. Wet bulk densities are mostly ranges from 1.75 to 2.15 g/cm³. Grain densities are dominant between 2.55 g/cm³ and 2.65 g/cm³. Velocities are distributed between 1650 m/s and 1850 m/s. Whereas, porosities are low less than 50% (mostly 40%) compared to muddy sediments. The sand ridge sediments are mostly composed of sandy materials (less than 4Ø in mean grain size). Shell fragments and are intermittently included in the sediments. Muddy sediments are also frequently observed. The lithology of deep core samples with sedimentary depth are various, reflecting changes of sedimentary environments during deposition. The physical property data were readily classified in good agreement with the lithological units alternating sand and muddy sand with sedimentary depth. The sand ridge sediments in study area were largely originated and redistributed from paleo-Seomjin River, caused by sea-level changes during the Quaternary. These results suggest that the physical properties of these sediments are mainly controlled by depositional processes in the vicinity of the paleo-Seomjin River, and that sea-level change specifically was a dominant sedimentary process in the study area during the Quaternary.

How to cite: Kim, G. Y., Park, K., Hong, S.-H., Jeong, E. J., Lee, G. S., Yoo, D. G., Kong, G. S., and Yu, S.: Physical property characterization of sand ridge sediments in the continental shelf of the South Sea, Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14116, https://doi.org/10.5194/egusphere-egu24-14116, 2024.

Toarcian to Aalenian sedimentary deposits in southern Germany have been accumulated in a shallow-marine, epicontinental shelf environment. The according successions are dominated by marlstones, thick claystones and argillaceous siltstones, with increasing percentages of sandstones towards the top of the Aalenian. While the Toarcian, including the TOC-rich paper shales of the Toarcian Oceanic Anoxic Event (T-OAE), is characterized by distinct lithologies, resulting in a number of hiatuses, Aalenian sedi­ments are likely to represent a relatively complete stratigraphic record. Although the investigated sequences are located in a region that has been known for its famous Jurassic sequences for more than 150 years, the sedimentary evolution and paleoclimatic significance of these successions, remain largely unexplored on a basin-wide scale. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning, stable organic carbon isotope and biostratigraphy data to identify Transgressive-Regressive cycles during the Late Toarcian to Aalenian. Results are based on four scientific drill cores of 200 - 250 m length, taken on a profile over a distance of about 300 km. Resulting trends in elemental Si/Al ratios, which are indicative for subtle grain-size variations, combined with sedimentological observations on ichnofacies and bedform development were used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework. Our study mainly focus the thick and largely homogenous lower Aalenian Opalinuston Formation.

How to cite: Jochen, E., Thomas, M., André, B., Martin, B., and Tilo, K.: Chemo- and sequence stratigraphy of Toarcian to Aalenian sedimentary successions from southern Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16720, https://doi.org/10.5194/egusphere-egu24-16720, 2024.

The Cambro-Ordovician Cow Head Group is an allochthonous sedimentary succession situated in the Humber zone of Western Newfoundland, the westernmost outer domain of the Appalachian orogenic belt in North America. It records submarine carbonate and rare siliciclastic deposits on a fault-bounded basin Laurentian margin shelf. It is characterized by interstratified carbonate conglomerate, mudstone, grainstone, packstone, wackestone, and lime mudstone. Mega-conglomerate along the Cambro-Ordovician boundary with anomalously coarse clasts are attributed to slope failure of the adjacent carbonate platform. While most authors agree that the transport and deposition of mega-conglomerate was related to seismicity and slope failure, their sedimentation have also commonly been linked to eustatic regression.

To try and better understand the tectonic vs. eustatic forces driving the stratal evolution of the Cow Head Group, detrital zircon U-Pb ages were obtained from the Furongian Tuckers Cove and coeval Martin Point members of the Cow Head Group, and used to better constrain the tectonic, eustatic, and stratal evolution of the Laurentian passive margin. The Tuckers Cove Member is particularly significant due to its record of quartz sand influx into an otherwise carbonate- and mud-dominated basin, and because it underlies megaconglomerate sedimentation linked to terminal Cambrian faulting. Moreover, its sedimentation was coeval with the Furongian Steptoean positive carbon isotope excursion (SPICE), and with shelf regression and the delivery of quartz sand documented in otherwise carbonate-dominated intracratonic basins throughout Laurentia, including in central Iowa, Utah, and coeval shelf carbonates in Western Newfoundland. Such a correlation is supported by preliminary detrital zircon U-Pb results from the Tuckers Cove and Martin Point members, revealing a mixture of typical Laurentian cratonic populations including Archean (ca. 2.73 Ga), Paleoproterozoic (ca. 1.9 Ga), Mesoproterozoic (ca. 1.1 Ga), and Neoproterozoic (ca. 593 Ma) detrital zircons. This implies continental-scale erosion and sediment flux, with sediment sourced from a widespread Laurentian cratonic catchment during the Furongian, including Archean and Proterozoic sources like the Superior, Makkoviak and Grenville provinces, and Ediacaran rift-related strata from the western Newfoundland - Quebec Appalachians. At present these zircon data do not resolve tectonic versus eustatic controls on Cow Head Group sedimentation. Nevertheless, they validate the concept of continental-scale weathering, drainage, and clastic sedimentation across Laurentia during the Furongonian. More work is needed to understand the relationship between such punctuated and widespread sediment generation and Late Cambrian plate tectonics, eustasy, and SPICE.

How to cite: Iturralde, J. and Lowe, D.: New U-Pb detrital zircon ages from the Upper Cambrian – Lower Ordovician Cow Head Group in the Humber Arm allochthon, Western Newfoundland: continental-scale drainage, local deformation, and global stratigraphy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17985, https://doi.org/10.5194/egusphere-egu24-17985, 2024.

The Corinth Gulf is a young, active rift with high rates of tectonic activity, high sediment fluxes, and a closed drainage system. The Gulf is currently connected to the Ionian Sea and the Mediterranean Sea by the Rion Sill and Acheloos-Cape Pappas Sill in the west (currently at 60 m and 55 m below sea level, respectively), and the Corinth Canal (completed in 1893) in the east. During glacial lowstands, the sea level dropped below the sill height and separated the Gulf from the Mediterranean The International Ocean Discovery Program (IODP) Expedition 381 focused on sampling sediments in the Corinth Basin to better understand past environmental changes, especially during glacial to interglacial transitions. Ostracode assemblages have been studied from the sediment core M0078, drilled in the center of the basin to a depth of 610 mbsf. This study relies on benthic ostracodes, which are persistent in the core and inform large changes in chemical-physical parameters and water depth within the basin We find ostracode fauna are particularly sensitive to environmental conditions driven by global sea level oscillations, which cause the Gulf of Corinth to be connected or isolated from the Mediterranean and therefore global oceans. In core M0078, ecosystem shifts are documented by coeval changes in the ostracode assemblages, reflecting variations in water depth (deep-shallow marine environments) degree of confinement-salinity (marine-lacustrine environments).
Two different types of assemblages have been identified from the ostracode assemblages: Mediterranean marine (Cytheropteron spp.; Henryhowella spp.; Aurila spp.; Cytherois spp.) and brackish with Black Sea influences (Amnicythere spp.; Tuberoloxoconcha spp.; Candonidae). Thirteen environmental-ecological stages followed one another crossing six tipping points that mark changes in relative sea level (RSL), climate and/or fluvial regime. Such faunal turnovers identify glacials (brackish assemblage, low sea level) and interglacials (marine assemblage, high sea level) and indicate a complex history of sea level changes that changed the drainage and depth of the Corinth Gulf during the Quaternary. 

How to cite: Parisi, R., Mazzini, I., and Cronin, T. M.: Glacial-interglacial faunal shifts in rift ecosystems during the Quaternary: dynamics and drivers of change from the Corinth Gulf record (Greece)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21621, https://doi.org/10.5194/egusphere-egu24-21621, 2024.

Age-depth models are fundamental tools used in all disciplines that rely on geohistorical records. They assign ages to stratigraphic positions (e.g., in outcrops or drill cores), which is necessary to estimate rates of past environmental change and establish timing of events in the Earth’s history.

Methods to estimate age-depth models commonly use simplified parametric assumptions on the uncertainties of ages of tie points, e.g., that they follow a normal distribution. The distribution of time between tie points is estimated using simplistic assumptions on the formation of the stratigraphic record, for example that sediment accumulation follows a Poisson process. As a result, these methods cannot incorporate evidence from complex empirical data or expert knowledge (e.g., from sedimentary structures such as erosional surfaces or from basin models) into their estimates, leaving important sources of information un- or underused.

Here, we present two non-parametric methods to estimate age-depth relationships from complex sedimentological and stratigraphic data. The methods are implemented in the admtools package for R Software and allow the user to specify any error model and distribution of uncertainties. As use cases of the package, we

• construct age-depth models for Devonian strata in the La Thure section, Belgium, using sedimentation rates constrained by cyclostratigraphic methods.
• use measurements of extra-terrestrial ³He from ODP site 690 (Maud Rise, Weddell Sea) to construct age-depth models for the Paleocene–Eocene thermal maximum.
• examine how temporally variable ²¹⁰Pb fluxes in lacustrine environments affect estimates of sedimentation rates and age-depth models.

These examples show how information from a variety of sedimentological and stratigraphic sources can be combined to estimate age-depth relationships that accurately reflect uncertainties of both available data and expert knowledge.

How to cite: Hohmann, N., De Vleeschouwer, D., Batenburg, S., and Jarochowska, E.: Nonparametric estimation of age-depth relationships from sedimentological and stratigraphic information, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1320, https://doi.org/10.5194/egusphere-egu24-1320, 2024.

The Triassic interval of the northern North Sea contains important hydrocarbon reservoirs and potential targets for CO2 sequestration. However, understanding of the age and distribution of sedimentary facies within the Triassic succession is hampered by the absence of a robust chronostratigraphic framework. Although recent studies for the UK Central North Sea (UK CNS) have defined a robust Triassic chronostratigraphic framework, significant stratigraphic nomenclature differences coupled with lack of dateable palynomorphs within the Triassic continental Hegre Group of the Norwegian Northern North Sea have led to non-biostratigraphic cross-border correlations.

Preliminary results from palynology and heavy mineral studies from the Norwegian Northern North Sea within a newly refined tectonostratigraphic framework have prompted a re-examination of the chronostratigraphic correlations between the Central and Northern North Sea. In the greater Tampen Spur area, a lack of active fault movement during sedimentation suggests that deposition of up to 2 km of Triassic Hegre Group sediments is largely climatically controlled and potentially regionally correlatable. Herein we aim to extend the well-established Triassic chronostratigraphic framework of the UK CNS to the Norwegian Northern North Sea area using distinct and age-equivalent Triassic mudstone units.

Well data from the Tampen Spur area reveal a regionally correlatable Norian mudstone which represents the Alke formation of the Hegre Group and an additional unassigned Ladinian mudstone package. These mudstone units were deposited on the distal fringes of a major distributive fluvial system sourced from the Norwegian margin. The Alke Formation seals the progradational motif of the Norian Lunde Formation and the Ladinian mudstone seals the Norian-Ladinian sandstone of the Lomvi Formation. The sandstones record the progradation and mudstones the retrogradation of the distributive fluvial system.

Given the age and similar petrophysical properties, we propose that the Alke Formation is equivalent to the Jonathan Mudstone Member and the Ladinian Mudstone is equivalent to the Julius Mudstone Member of the Skagerrak Formation in the UK CNS. Thus, the Lunde formation is Josephine equivalent and the Lomvi formation represents the Joanne Member. This layer-cake reservoir configuration is completed with a sandier and locally truncated Raude Formation which is equivalent to the Rhaetian Joshua Mudstone Member of the UK CNS.

This preliminary cross-border chronostratigraphic framework unifies the Triassic stratigraphy of the North Sea within a newly refined tectonostratigraphic framework. Regional chronostratigraphic correlations allow a comprehensive paleogeographic reconstruction between the Central and Northern North Sea enlightening all major climatic alternations from Olenekian to Rhaetian.

How to cite: Saltapidas, S., Hartley, A., Howell, J., Schofield, N., Brackenridge, R., and Watson, D.: Triassic Stratigraphy of the North Sea: A New Cross-border Chronostratigraphic Framework using Age Equivalent Units from the Tampen Spur Area, Norwegian North Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5591, https://doi.org/10.5194/egusphere-egu24-5591, 2024.

The Upper Triassic carbonate-evaporite-bearing succession in the Honaz Mountain Range (HMR) in SW Anatolia (Turkey), exists as a tectonic slice within the carbonate and ophiolithic units of allochthonous Lycian Nappe stacks. It comprises interbedded layers of sulphates (gypsum) and limestones or dolostones. Sedimentological and palynofacies analyses suggest that the Honaz succession was deposited in the more protected areas of the peritidal zone of a shallow inner ramp under a tropical/arid climate. Three main subenvironments are identified based on facies and microfacies associations: (i) Sabkha, exhibiting two distinct microfacies-gypsum and peloidal packstone/grainstone, (ii) Tidal flat, consisting of six microfacies-cryptalgal boundstone, fenestral bindstone, laminated peloidal mudstone, laminated algal/microbial boundstone, pisolite rudstone, and carbonate breccias, (iii) Lagoon, featuring five microfacies-laminated peloidal packstone/grainstone, crinoidal wackestone/packstone, mudstone, bioclastic packstone, and ostracodal/peloidal packstone to grainstone. The succession is characterized by meter/submeter-scale cyclic facies alternations, similar to Lofer cycles, Dolomia Principale/Hauptdolomit Formation, and Dachstein Formation of European basins.

Facies and petrographic analyses, along with Sr isotope ratios of dolomites, indicate early dolomitization from evaporated seawater in this environment (shallow seepage reflux or evaporative-drawdown). However, the depletion in δ¹⁸O (-11.53 to -5.46 ‰, mean -8.29 ‰), and slightly radiogenic Sr isotope values of dolomites are attributed to a recrystallization process, occurring at high temperatures during burial diagenesis. The relatively high δ¹³C values (+0.76 to +3.60 ‰, mean +2.42 ‰) suggest dolomite alteration in a relatively closed system. The microfacies of the Honaz succession are comparable to those in other Upper Triassic successions (e.g., western Carpathians, Italian Apennines, Spain, northern Calcareous and southern Alps, external Dinarides and Hellenides, southwestern Germanic Basin, Morocco, Israel, Albany) deposited under similar environmental conditions. Comparing facies with those from other coeval sequences allows us to delineate such carbonate-evaporite shallow water platforms on the northern margin of the Neotethys Ocean. This study was supported by the Pamukkale University BAP Research Project (2022ÜBBİD001).

How to cite: Alçiçek, H., Spina, A., Cirilli, S., Yılmaz, İ. Ö., Capezzuoli, E., Brogi, A., Liotta, D., and Alçiçek, M. C.: Sedimentary facies and depositional environments of the Upper Triassic carbonate-evaporite succession in the Honaz Mountain Range (SW Anatolia, Turkey) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8260, https://doi.org/10.5194/egusphere-egu24-8260, 2024.

The research area is located in the central part of North Macedonia, in the area of the Klepa Mts. Based on sedimentological, micropaleontological and biostratigraphical investigations of samples from both the east and west side of the Klepa Mts., sedimentary rocks of the Upper Creaceous age are determined. During the latest Cretaceous, this area was dominated by the sedimentation of dominantly carbonate rocks with variable amounts of clastic components.
From the tectonic point of view, investigated area belongs to the contact zone between the Adriatic microplate (on the west) and the Eurasian margin (on the east). This contact zone is represented by a relatively wide area, that evolved in the form of tectonically active sedimentary basins due to a convergence between the aforementioned tectonic plates. However, the nature of this contact zone, also known as the Sava-Vardar zone, which extends along the central part of the Balkan Peninsula, is still a matter of debate. The traditional view explains the Sava – Vardar zone as the remnant of the Late Cretaceous oceanic domain, which subducted under the Eurasian plate and initiated the formation of the Banat-Timok-Srednjegornje volcanic arc. Nevertheless, based on the study of several Upper Cretaceous basaltic occurrences within the Sava-Vardar zone, it is concluded that they are of an intraplate origin. Following that, if we assume that this traditional point of view for the contact zone is true, these basalts should be interpreted as being formed in the forearc region. Alternatively, if these basaltic occurrences are of intracontinental origin, they can be interpreted as being formed in the area of a diffuse tectonic zone between the Adriatic microplate and the Eurasian plate, that was suitable for the formation of pull-apart basins.
Investigated carbonate rocks are represented by reddish, locally pinkish, or grey, light-gray hemipelagic and pelagic biomicrites with very rich planktonic and benthic foraminiferal associations and other diverse micro- and macrofossil assemblages (calcareous nannoplankton, calcified radiolarians, palynomorphs, inoceramids, as well as reef-fossil detritus, transported to deeper parts of the basin). According to biostratigraphical analysis, defined units of scaglia type limestones of the Klepa Mts. implied that basin formation began during late Santonian.
A study of lithological and stratigraphical characteristics on the field, as well as the determination of a very rich association of the Upper Cretaceous fossils, indicate constant sedimentation from the late Santonian to early Maastrichtian time in the area of the Klepa Mts. Palaeoecological characteristics of the determined association of planktonic foraminifers indicate relatively deep sedimentation (~300 m) of the studied limestones, with periodical changes in bathymetry.

Acknowledgement: This research was financed by the Science Fund of the Republic of Serbia through project RECON TETHYS (7744807).

How to cite: Gajić, V., Dunčić, M., Mladenović, A., and Prelević, D.: UPPER CRETACEOUS SCAGLIA TYPE LIMESTONE FROM KLEPA Mts. (NORTH MACEDONIA) – SEDIMENTOLOGY AND BIOSTRATIGRAPHY, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21298, https://doi.org/10.5194/egusphere-egu24-21298, 2024.

Ikaite, CaCO₃•6H₂O, is a metastable polymorph of calcium carbonate which is the parent mineral to glendonites (stellate calcite pseudomorphs found throughout the geological record). In the modern ocean, ikaite may be found below the sediment-water interface, or in tufa columns, at temperatures of<7 °C (Buchardt et al., 2001; Zhou et al., 2015; Vickers et al., 2022), yet the presence of glendonites in marine sediments believed to have been deposited under much warmer conditions (i.e. > 10 °C) suggests that this ikaite could have formed under warmer conditions than it does today, or that short-duration cooling interrupted hyperthermal episodes of the early Cenozoic (Vickers et al., 2024). As much uncertainty surrounds the timing, and physical and chemical conditions of the formation, and transformation, of the precursor ikaite, the usefulness of glendonite for (semi-)quantitatively reconstructing temperature and environmental conditions is uncertain, and the explanation for the early Cenozoic glendonites remains obscure. This study examines the physical and chemical controls on ikaite nucleation, growth and transformation in seawater, with a view to understanding trace element and isotope partitioning into ikaite and ikaite transformation products, and if and how certain elemental and isotopic environmental proxies may be applied to glendonite calcite phases.

References

Buchardt, B., Israelson, C., Seaman, P. and Stockmann, G., 2001. Ikaite tufa towers in Ikka Fjord, southwest Greenland: their formation by mixing of seawater and alkaline spring water. Journal of Sedimentary Research, 71(1), 176-189.

Zhou, X., Lu, Z., Rickaby, R.E., Domack, E.W., Wellner, J.S. and Kennedy, H.A., 2015. Ikaite abundance controlled by porewater phosphorus level: Potential links to dust and productivity. The Journal of Geology, 123(3), 269-281.

Vickers, M.L., Vickers, M., Rickaby, R.E., Wu, H., Bernasconi, S.M., Ullmann, C.V., Bohrmann, G., Spielhagen, R.F., Kassens, H., Schultz, B.P. and Alwmark, C., 2022. The ikaite to calcite transformation: Implications for palaeoclimate studies. Geochimica et Cosmochimica Acta, 334, 201-216.

Vickers, M.L., Jones, M.T., Longman, J., Evans, D., Ullmann, C.V., Wulfsberg Stokke, E., Vickers, M., Frieling, J., Harper, D.T., Clementi, V.J. and Expedition, I.O.D.P., 2024. Paleocene–Eocene age glendonites from the Mid-Norwegian Margin–indicators of cold snaps in the hothouse?. Climate of the Past, 20(1), 1-23.

How to cite: Vickers, M. and Evans, D.: Physical and chemical controls on ikaite (calcium carbonate hexahydrate) precipitation in seawater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4748, https://doi.org/10.5194/egusphere-egu24-4748, 2024.

The Hengchun Peninsula is the southernmost part of Taiwan Island, and marks the youngest portion of this active orogenic belt. At the southwestern corner of the peninsula, the Western Hengchun Tableland is underlain by the Pleistocene Hengchun Limestone, one of the youngest stratigraphic units of the Hengchun Peninsula. The Maobitou Limestone, which only crops out at the southern tip of the tableland, is a distinctive part within the Hengchun Limestone. Its ubiquitous large-scale cross beds have sparked controversy in its sedimentary environments. The location of this unit makes it a crucial stratigraphic marker for further understanding the growth processes of the peninsula, and even the orogen itself. However, the Maobitou Limestone has not been studied as much as the other parts of the Hengchun Limestone. Therefore, we investigated 15 outcrops of the Maobitou Limestone along the coastline for their detailed sedimentological and stratigraphical characteristics. We interpreted the limestone as a deposit under storm-influenced environment, due to the observations of (i) amalgamated beds with hummocky cross-stratification (HCS); (ii) graded grains observed within polished slabs; (iii) shelly beds rich in broken barnacles; (iv) various taphonomic conditions of fossils; (v) micrite found in grainstones; and (vi) slightly bioturbated or burrowed beds at bottom of units. Three lithofacies groups were established from these observations: (a) bioclastic packstone facies; (b) bioclastic packstone-grainstone facies, and (c) bioclastic grainstone facies. Variations within these groups were also identified through further subdivision with sedimentary structures and abundance of lithoclasts. We can further correlate these facies between stratigraphic columns using an irregular scouring surface at a similar horizon, and with a 70-m long borehole core. Based on biostratigraphy, the depositional age of the Maobitou Limestone likely ranges between 0.61 and 1.70 Ma, and appears to be different from the other parts of Hengchun Limestone. The source of winnowed skeletal materials may be a topographic high that is likely a coral reef area, supporting our interpretation that the Maobitou Limestone is deposited from high energy storm waves, above the storm wave base off the ramp. As the orogen grows, the depositional setting evolved from a storm-influenced middle ramp and shallowed upward into the inner ramp. 

How to cite: Wong, Q. C., Shyu, J. B. H., Wang, S.-W., and Shea, K.-S.: Stratigraphy and sedimentology of the Pleistocene Maobitou Limestone in the Western Hengchun Tableland, southern Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14075, https://doi.org/10.5194/egusphere-egu24-14075, 2024.

Carbonate platform strata have been extensively utilized to decipher geological history. However, due to the fluctuating ambient environment and the complex growth pattern of carbonate factories, preserved records are generally incomplete. For example, given the platforms are located in shallow water environment, they are prone to subaerial denudation when the sea level falls. Numerical modelling is a popular approach to examine spatial and temporal heterogeneities of carbonate platform architectures. While growth and submarine transportations that have been extensively considered, surprisingly, substantially less efforts have been invested to subaerial denudation and its effects on 3-dimentional carbonate platform architecture (e.g., the denudation rates are simplified to constant dissolution rates regardless of the varying ambient environment and local geomorphology).

Herein, we implemented a model with chemical dissolution and physical erosion, calibrated with 35Cl (a geochemical proxy used to estimate kyr-scale denudation) karst regions into CarboKitten.jl (https://mindthegap-erc.github.io/CarboKitten.jl/), a new open-source carbonate platform model. We compared the outputs of models with and without the denudation by using mathematical tool (LBP method) and assessed how the presence of denudation distorts the age-depth relationships. We find that the inclusion of denudation could increase both temporal and spatial heterogeneities, which may decrease the estimation biases on age-depth model. Our results emphasize the importance of considering subaerial denudation in reconstructing geological histories. This study provides a comprehensive framework for refining interpretations and enhancing the accuracy of paleoenvironmental reconstructions based on carbonate platform sediments.

How to cite: Liu, X., Hidding, J., Hohmann, N., Burgess, P., De Vleeschouwer, D., and Jarochowska, E.: How does subaerial erosion of carbonate platform distort the sedimentary record?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19418, https://doi.org/10.5194/egusphere-egu24-19418, 2024.

Tabei area is an important area of Cambrian ultra deep exploration in Tarim Basin. Middle Cambrian dolomite reservoirs are developed and the relationship between reservoir and cap rock configuration is complex. Therefore, the study of sedimentary facies types and their distribution characteristics is of great significance for the next exploration plan in the region. This study is based on drilling and seismic data within the work area, and comprehensively analyzes the sedimentary evolution process of the Middle Cambrian platform in the Tabei area through petrology, seismic facies, and well connected sedimentary facies. The research results indicate that the Middle Cambrian in the study area is a typical bordered platform, which is influenced by ancient terrain and develops (evaporates) tidal flats, reef shoals, platform edge reef shoals, slopes, and basins from west to east. The overall trend of the facies belt shows an eastward migration. The Taiwan region mainly develops tidal flat, evaporative tidal flat, and granular beach, further divided into six microfacies such as argillaceous dolomite and micritic dolomite. Six stages of reef shoals are developed at the edge of the platform, stacked in an aggradation progradation manner. Based on comprehensive analysis, it is believed that in addition to the platform edge reef beach body, the dolomite behind the reef beach is another favorable facies zone with good exploration potential.

How to cite: Wang, J., Yu, K., and Maimaiti, A.: Sedimentary Evolution Characteristics of Middle Cambrian Carbonate Platform in Tabei Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2789, https://doi.org/10.5194/egusphere-egu24-2789, 2024.

Marine climate archives in Red Sea sediments have the great potential to improve our understanding of mankind’s dispersal out of Africa. However, cores from deep sea sediments are often greatly disturbed by bioturbation reducing the resolution of recorded climate events. We report geochemical and geophysical data from a 244 cm long sediment core collected from a recently discovered deep sea brine pool near the Arabian slope and the Al Wajh carbonate platform. The analysis of the high-resolution climate archive preserved in the undisturbed sediments of the brine pool provide excellent correlations to numerous known historical events in the last 6.5 ka, and indicate the great potential of brine pool sediments to provide further insights into climate changes and human civilization development within the African-Arabian dessert belt.

The recovered marine sediment core from a brine pool was therefore investigated to test its reliability for in-depth Holocene climate studies. The brine-filled depression (>190 PSU; 25 m thick) is located 25 km south of the Al Wajh carbonate platform in 640 m water depths. It is bounded by a salt extrusion in the northwest and a steep shallow water reef in the east. The undisturbed dark-olive coloured sediment succession are carbonate-dominated, devoid of bioturbation, and rich in TOC indicating an anoxic environment. The established stratigraphy via five radiocarbon dates of (planktic foraminifera. T.sacculifer and O. universa) resulted in high sedimentation rates ranging from 30.22 to 50.6 cm/ka. The integration of geochemical (e.g., isotope data, XRF) and geophysical data (e.g., magnetic susceptibility, spectrophotometer reflectance) revealed the recording of dozens of prominent climate periods (e.g., Roman Climate Optimum, Little Ice Age), changes (e.g., Mid-Holocene Highstand), and historical events (e.g., collapse of Late Uruk and Akkadian Empire) since the Mid-Holocene. In addition, the data analyses suggest that even periods of increased ENSO activity are recorded within the brine pool sediments of the Red Sea.

The outcome of this study highlights the potential of anoxic brine pool sediments as a unique and important high-resolution climate archive and the urgent need to further in-depth studies.

How to cite: Petrovic, A., Lakrani, P., and Vahrenkamp, V.: Global to regional Holocene climate changes and events recorded in a near-slope deep sea brine-pool sediments of the NE Red Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4630, https://doi.org/10.5194/egusphere-egu24-4630, 2024.

Carbonate Platforms form an important source of information on the past evolution of species as well as the climate conditions they lived in. However, stratigraphic records are often considered unreliable tracers of evolution, since they contain many gaps.

These gaps are often on a time scale too short to measure, but may significantly affect further studies of biodiversity and climate change. This is why we use forward modelling to estimate the statistics of gap distributions under a wide variety of environmental parameters. Forward modelling can be used to test hypotheses at time scales that are not available for experimentation. The dominant driver for generating different stratigraphic architectures is the input sea-level curve, balancing periodic (Milankovich), stochastic and subsidence only effects. Added to that are varying degrees self-organisation, sediment transport and subarial erosion.

The basis of our model is sediment production following the model by Bosscher and Schlager (1992), with biological self-organisation modeled after the cellular automaton approach (CarboCAT) by Burgess (2013) and a sediment transport model inspired on Warrlich (2000).

CarboKitten is fully Open Source, written in Julia, aiming for performance, modularity and ease of use. We will show preliminary results produced by CarboKitten and also explain how they are generated.

How to cite: Hidding, J., Liu, X., Burgess, P., and Jarochowska, E.: CarboKitten.jl, an Open Source simulator for Carbonate Platform formation in Julia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8906, https://doi.org/10.5194/egusphere-egu24-8906, 2024.

In the more than 120 years since Amadeus William Grabau (1870-1964) first proposed the classification of carbonate rocks in 1904, geologists have conducted in-depth research on this issue and made multiple modifications, forming the currently relatively comprehensive and systematic limestone classification scheme. Among them, Folk (1959, 1962) and Dunham (1962) classified limestones based on the perspective of structural maturity, which has become the most widely used classification scheme to this day. It is worth noting that Mei Mingxiang supplemented Wright VP’s (1992) classification scheme in 2001 by adding types of limestones formed by event sedimentation that cannot be explained by the perspective of structural maturity, such as seismolithic limestone, turbidite limestone, etc.

However, there are also problems with previous classification schemes. First, limestone types similar in structure to clastic rocks formed by terrigenous carbonate particles under abnormal depositional processes are not included in the carbonate rock classification system; Second, travertine precipitated carbonate rocks are not included in the carbonate rock classification system. Based on studies of carbonate rudite in the Bengbu depression, conglomerate deposits of the Guanzhuang Formation in the Pingyi Basin, and travertine, as well as years of field work experience, the author has further modified the limestone classification system by adding a terrigenous limestone class formed under abnormal depositional conditions and a purely chemical limestone class.

In view of the well-developed characteristics of terrestrial carbonate rocks in China, a terrigenous clastic limestone subclass was added under the abnormal deposition subclass, and a purely chemical limestone class with mud crystal components was added under the diagenetic class. The following changes have been made to the cause-structure classification table of limestones in this study: (1) The classification method of dividing limestones into depositional, biological and diagenetic classes remains unchanged, but the skeletal components are used as the basis for further subdivision. Compared with the previous scheme, more terrigenous clastic and mud crystal classes have been added to the skeletal components. (2) For limestones formed by terrigenous carbonate particles under abnormal depositional conditions, they are subdivided into rudite limestone, arenite limestone, mudstone limestone and their transitional types according to the particle size of the skeletal grains. (3) In the diagenetic class, the added purely chemical limestone refers specifically to travertine or travertine cemented collapse limestone (cave limestone), with mud crystal as its skeletal component.

How to cite: Ma, X., Qiu, L., Wang, Y., and Yang, Y.: Discussion and Supplement of Limestone Classification Schemes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13802, https://doi.org/10.5194/egusphere-egu24-13802, 2024.

The AMUSED project (A MUltidisciplinary Study of past global climatE changes from continental and marine archives in the MeDiterranean region, https://progetti.ingv.it/index.php/it/amused) aims at improving knowledge of middle-late Quaternary climate variability by integrating paleoclimate multi-proxy data acquired in different geological settings of the Mediterranean region. In this context, we investigate the Castiglione maar, Colli Albani volcanic district in central Italy, for acquiring a high-resolution and geochronologically well-constrained multi-proxy record of the lacustrine succession. After geophysical exploration, two parallel 116 m- and 126.5 m-long sediment successions were recovered from the central sector of the basin. The sedimentary infilling mainly consists of fine sand, silt and clay, with minor gravel intervals and numerous tephras mostly deriving from explosive eruptions of the Roman Province volcanoes such as Mt. Vulsini, Vico, Mt. Sabatini and Alban Hills. More than fifty visible volcanic layers were identified and used, together with some lithostratigraphic features, for correlating the two parallel cores and build up a composite sediment section of 131.2 m in length. The geochemical fingerprinting of some key tephra layers allowed to establish a preliminary chronological framework for the Castiglione succession spanning the last 365 ka, with a mean sedimentation rate of 0.33 mm/yr. High resolution X-ray Fluorescence scanning was acquired at 2.5 mm intervals on the composite section and will be used, along with preliminary results from total inorganic and organic carbon, δ¹⁸O-δ¹⁴C and ostracods analyses, for paleoenvironmental reconstructions.

How to cite: Macrì, P., Siravo, G., Smedile, A., Caricchi, C., Minelli, L., Wagner, B., Regattieri, E., Di Vincenzo, G., Ferretti, P., Mazzini, I., Giaccio, B., Scateni, B., Cascella, A., Isola, I., and Di Roberto, A.: A multiproxies paleoclimatic study of lacustrine sediment from the Castiglione maar drilling (central Italy):  first insight of the AMUSED Project., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1891, https://doi.org/10.5194/egusphere-egu24-1891, 2024.