In the framework of the INGV–Pianeta Dinamico research theme TIFEHO (Trachytic Ignimbrites magma-chambers Formation and Evolution in the pre-HOlocene history of the Campania volcanic area), whose main goal is to understand the growth and evolution of the deep magmatic feeding system prior to high magnitude eruptions of the Neapolitan volcanic area, a deep scientific drilling has been performed, down to 113.2 m below the ground level, in the Ponti Rossi area, north of Naples (Italy). The drilling site was chosen for three main reasons: 1) it is external to any proposed Campi Flegrei (CF) caldera rim, topographic or structural scarp and downthrown area; 2) the surface geological record consists of a stratigraphic succession including several pyroclastic units sandwiched between the products of the 39.2 ka Campanian Ignimbrite (CI) eruption at the base and the 15 ka Neapolitan Yellow Tuff (NYT) eruption at the top, representing the two largest explosive events of CF, responsible for the caldera formation; 3) a 96 m deep scientific drilling, carried out in the same site in the late 1990’s, retrieved a pre-CI succession composed of eleven pyroclastic units totalling 61.8 m. Results from a detailed stratigraphic investigation, coupled with the sedimentological and geochemical characterization of a total of seventy-seven samples collected throughout the sequence, highlight that the Ponti Rossi borehole retrieved a stratigraphic record in which the NYT deposits represent the shallowest sediments. An important result is the absence of the CI deposits as well as of any pyroclastic deposit belonging to the CI-NYT (39-15 ka) chronostratigraphic interval, testifying a prolonged phase of strong erosion preceding the NYT eruption. Most of the cored succession, directly underlying the NYT deposits, consists of a thick pyroclastic sequence, totalling 88.05 m and representing the 78% of the retrieved succession, attributed to volcanism older than CI. The stratigraphic investigation and the X-Ray diffraction analysis (XRD) of the cored sediments allowed to identify at least thirty-four pyroclastic units older than CI, having thickness between 0.13 and 21.5 m, separated by well-developed paleosols and/or reworked volcaniclastic deposits. This pyroclastic succession consists predominantly of massive to stratified, matrix-supported to fines-poor pyroclastic current deposits, both magmatic and phreatomagmatic, and minor coarse- to fine-grained fall deposits. The features of several units (e.g., coarseness, lithic enrichment, considerable thickness) are compatible with a proximal vent while a number of units could be intermediate to distal tephra layers, some of which sourced from the Island of Ischia as highlighted by the available geochemical data. The retrieved stratigraphic record suggests the occurrence of a remarkable explosive activity >40 ka, the study of which will allow the achievement of a better knowledge of the magmatic systems feeding the volcanic activity of Neapolitan volcanoes.

How to cite: de Vita, S., Sparice, D., Di Vito, M. A., Arienzo, I., Di Roberto, A., Giaccio, B., Mormone, A., Pappalardo, L., Pelullo, C., Petrosino, P., and Re, G.: Reconstructing the Neapolitan volcanism prior to the 39.2 ka Campanian Ignimbrite: new stratigraphical results from a scientific drilling north of Naples (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11467, https://doi.org/10.5194/egusphere-egu24-11467, 2024.

How to cite: Geßner, A.-L., Wollschläger, J., Giebel, H. A., and Badewien, T.:  Long-term Effects of Coastal Protection Measures on Sedimentology in a Dynamic Tidal Inlet: Spiekeroog, East Frisian Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22096, https://doi.org/10.5194/egusphere-egu24-22096, 2024.

The formation of extensive dolomite across ancient carbonate platform is widely attributed to the replacement of the calcium-carbonate so-called dolomitization. However, it is still unclear whether the extensive dolomite formation is controlled by one single or multiple mechanisms, as whether the mineralogical, petrological, and geochemical records of dolomite preserve the pristine signature or diagenetic effect is still under debate. In this study, we integrate carbon, oxygen, strontium and magnesium isotopes to provide new insights into ancient dolomite origin interpretation. 
Dolomite in the Upper Jurassic Arab Formation on the Arabian Plate has widely been studied due to the complete carbonate-evaporite cycle and relevance to oil reservoirs. Sabkha and seepage reflux dolomitization models have been proposed despite the high temperatures inferred from clumped isotopes and fluid inclusions, as well as some geochemical data such as oxygen and strontium isotopes, are inconsistent with near-surface dolomitization conditions. Here we performed integrated isotope study of the Upper Jurassic Arab Formation, and found that (1) Mg isotope data range from -2.25 ‰ to -1.78 ‰, suggesting the Mg cations for Arab dolomite formation were delivered from Late Jurassic seawater, which is consistent with the idea that dolomite is a valid archive of seawater Mg isotope composition through geological times; (2) in each cycle, more depleted Mg isotope signatures in dolomite formed at shallower depth than that formed at deeper depth, indicating top-down dolomitization process which is controlled by percolation of dense and saline fluids, suggesting the advective flow model and related seepage reflux dolomitization; (3) parts of Sr isotopic ratios are out of Late Jurassic seawater range, revealing hydrothermal or burial dolomitization probably altered the dolomite formed from near-surface conditions, which can also be verified by depleted oxygen isotopic values. This study indicates that ancient carbonate platform with massive dolomite distribution are probably generated by multi-mechanism dolomitization processes and it is necessary to integrate Mg isotope with traditional isotope methods to unravel the dolomite problem.

How to cite: Jia, X., Li, W., Xia, Z., and Alsuwaidi, M.: Geochemical fingerprints of dolomitization in Upper Jurassic Arabian carbonate platform: Evidence from carbon, oxygen, strontium and magnesium isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14160, https://doi.org/10.5194/egusphere-egu24-14160, 2024.

Provenance analysis is the foundation of basin analysis, and also an important means to restore the tectonic background of the sedimentary source area, estimate transport paths and distances of sediment, reconstruct paleocurrent systems, and reproduce the evolution history of sedimentary basins.The Bozi-Dabei area is located in the northwestern margin of Kuqa Depression in the Tarim Basin, where Bashijiqike Formation and Baxigai Formation of the Lower Cretaceous are held by multiple uplifts, which leads to the possibility of multiple provenances. Thus, detailed study of the provenance characteristics is needed to ascertain the the supply range and duration time of the indefinite provenances.

We identify the sediment provenance combining proportion of stratum lithology, rock and mineral compositions, and heavy mineral combination characteristic. And the paleocurrent direction is interpreted by the bedding dip direction obtained from imaging logging.

In the study area, there is an overall decreasing trend of the ratio between sandstone and stratum thickness from north to south, indicating that the South Tianshan on the north is the main provenance for this area, while the anomalous high-value zone in the southwest suggesting the possibility of regional provenance. According to the petrologic and mineralogical data of sandstone composition, detritus component, and heavy minerals, there is a certain regular variation from the northwest and northeast of the study area to the central location, such as the increasing proportion of quartz, metamorphic debris, and stable heavy minerals like garnet. Meanwhile, consistent heavy minerals combination with those in South Tianshan indicates that sediments originated from this provenance and were supplied to the study area along two paleocurrent systems.Consistent with the proportion of stratum lithology, the rock and mineral composition in the southwest, high magmatic grains and zircon for example, differs significantly from most parts of the study area. Combination characteristic of heavy mineral shows difference compared to those from South Tianshan provenance but matching those from Wensu Uplift, suggesting a local sediment supply from Wensu Uplift on the southwest. Paleocurrent data indicate three paleocurrent directions: NNW-SSE direction in northeast; NNE-SSW direction in northwest; SW-NE direction in southwest - all consistent with three paleocurrent systems indicated by rock and mineral compositions.

The results show that sediments originating from both South Tianshan and Wensu Uplift have been deposited into DFS during sedimentary period.The proportion of stratum lithology, rock and mineral composition, as well as bedding occurrence indicate that during Baxigai Formation deposition period, Wensu Uplift had a larger influence range which gradually diminished during Bashijiqike Formation deposition period - possibly implying a further tectonic uplift of Tianshan due to Himalayan movement.

How to cite: Ju, Q., Ren, L., and Luan, G.: Evolution of Early Cretaceous Multi-provenance deposition system in the northwestern margin of Kuqa Depression: Evidence from stratigraphic lithology proportions, mineral composition, and bedding dip direction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5569, https://doi.org/10.5194/egusphere-egu24-5569, 2024.

The Gyeongsang Basin, Korea, is a non-marine sedimentary basin formed in an active continental margin setting by the subduction of proto-Pacific plates beneath the East Asian continent during Early Cretaceous time. The basin fill is divided into four Goups based on volcanism and plutonism. They are the Sindong (no volcanic materials), Hayang (some volcanic materials), Yucheon (mostly volcanic materials), and Bulguksa intrusive Groups. Since siliciclastic sediments were dominant in the early stages of basin evolution, it was relatively easy to classify the relative ages of strata through lithostratigraphy. However, the chronostratigraphic correlation of the Yucheon sediments is very difficult due to the intermittent development of siliciclastic deposits compared to volcaniclastics by increased volcanic activity. The Icheonri Formation, belonging to the Yucheon Group, is very difficult to correlate chronostratigraphy with other strata. Additionally, radiolarian-bearing chert pebbles, whose source rocks have not been reported in Korea, were recently found in the Icheonri Formation, raising interest in their provenance. Therefore, LA-MS-ICP-MS detrital zircon U-Pb dating was performed on two sandstone samples to constrain the maximum deposition age of the formation and obtain information about their provenance. Both samples showed a relatively wide age range, from the Precambrian to the Cretaceous. Among them, the weighted mean ²⁰⁶Pb/²³⁸U ages of the youngest age clusters were calculated to be 99.76±0.58 Ma (n=10, MSWD=1.5) and 99.86±0.38 Ma (n=25, MSWD=1.5), respectively. These ages correspond to the early Cenomanian in geological time scale. The presence of radiorarian-bearing chert pebbles and significant concentrations of Permian zircons in the Icheonri Formation raises the likelihood that some of the sediments that comprise the formation are from SW Japan. This study provides important evidence indicating that before the opening of the East Sea, the Korean Peninsula and Japan were closer together than they are now. The temporal and spatial variations of the origin and supply processes from the source to the sink, however, still require more investigation.

How to cite: Kim, G., Chae, Y.-U., Joo, Y. J., Choi, T., and Lim, H. S.: Maximum depositional age and provenance of the Cretaceous Icheonri Formation in southeast Korea using detrital zircon U-Pb dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15199, https://doi.org/10.5194/egusphere-egu24-15199, 2024.

Quartzose sandstone dominates the Upper Cretaceous sedimentary succession of the Barmer Basin, but its source of sediments is mostly hypothetical. This study elaborates the modal analysis of sandstone, EPMA mineral chemistry of detrital tourmaline and rutile and U-Th-total Pb monazite geochronology within the Fatehgarh Formation to track the possible source rocks. The poorly studied, fluvial- to marine-originated, Upper Cretaceous, roughly 125 m thick, locally cross-stratified formation crops out nearby the Barmer town, Rajasthan. The formation contains mainly sandstone, shale, claystone, conglomerate and evaporite beds forming nonconformity with Lathi Formation/Precambrian Malani Igneous Suites. The Fatehgarh Formation is medium- to coarse-grained, subangular to rounded grains, and moderately to well sorted. The sandstones are cemented by the silica, calcite and iron oxide cement. The QFR modal analysis classified quartzose sandstone and implies craton interior and recycled orogeny provenance for the sandstone. The presence of derital quartz overgrowth and rounded zircon, rutile and tourmaline suggest sediment recycling in the formation. The heavy mineral assemblage of the formation includes primarily tourmaline, zircon, and rutile with leucoxene, Fe-Ti minerals, staurolite, monazite, andalusite and opaque mineral. The EPMA analysis of the tourmaline reveals schorl and dravite varieties of tourmaline. The tourmaline composition Ca-Fe-Mg plot within the fields of ‘Li-poor granites and Ca-poor metapelites and metapsammites’. The tourmaline suggests their derivation from the Paleoproterozoic Pb-Zn deposits of Rajpura-Dariba, Zawarmala, Rampura-Agucha and Mangalwar Complex in the Aravalli-Delhi Fold Belt, and leucogranites of Sewariya-Govindgarh and Balda-Motiya of Delhi Supergroup. The rutile mineral chemistry shows ‘metapelitic origin’ of the majority of rutile grains for the basin. The presence of staurolite and andalusite mineral supports metamorphic source contribution for the sediments. The U-Th-total Pb dating of monazite grains shows major peaks at 950 Ma and 500 Ma. The monazite geochronology corroborates Pan-African and Delhi orogeny- related sediments for the Barmer Basin. The formation shows SW paleocurrent direction. The petrography, mineral chemistry and geochronology indicates the possible source of the sediments from the Marwar Supergroup, Malani Igneous Suites, and Aravalli-Delhi Fold Belts.

How to cite: Rajak, P. K., Banerjee, S., and Prabhakar, N.: Geochemical and petrographic study helps to understand the source of Upper Cretaceous Fatehgarh Formation, Barmer Basin, Rajasthan, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11591, https://doi.org/10.5194/egusphere-egu24-11591, 2024.

The Sichuan Basin is an expansive Mesozoic-Cenozoic basin in the southwestern mainland of China, with dinosaur fossils widely scattered and full-type accumulated in the Jurassic strata. Wangcang dinosaur fossil burial site is located at the southern foot of the Qinling Mountains and the southern wing of Micang Mountain Uplift in the northern Sichuan Basin. Geologic cross-section measurement, fieldwork, and study of 3D seismic profiles are carried out to explore the mechanism of rapid accumulation and burial of rich incomplete dinosaur fossils in Wangcang. 
The results show that both the sedimentary process and the tectonic function of the Shaximiao Formation in Wangcang have undergone major changes due to basin and mountain relationships during the sedimentary period. The Shaximiao Formation experienced a transition from the lacustrine sedimentation of the Qianfoya Formation to fluvial-deltaic facies, suggesting climatic and environmental changes. Notably, the Second Member of the Shaximiao Formation coincided with intensified seismic activities, we identified indicators of seismites, including sand pillows, seismic fractures, step faults, liquefied veins, shattering rocks, and seismic breccias, etc. Each set of seismites has different vertical sequences, and the typical liquefied structure deformation directly suggests seismic activities. Tectonically, while the Qianfoya Formation displayed reverse faults, the Shaximiao Formation showed a series of strike-slip normal faults. The seismites and sediment tectonic features reveal a correlation with the catastrophic mass mortality of dinosaurs in Wangcang. We propose that seismic events significantly impacted dinosaur habitats, leading to mass deaths and subsequent burials in the purplish-red argillaceous siltstone near Huaishu Village in Wangcang. For the first time, the seismites are presented as new evidence of tectonic shifts and seismic activities in Wangcang during the Middle Jurassic, and it provides a new perspective for dinosaur taphonomy in the Sichuan Basin.

How to cite: Guo, Y.: Seismites of the Jurassic Shaximiao Formation in NW Sichuan Basin of SW China: Implication for Dinosaur Taphonomy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2681, https://doi.org/10.5194/egusphere-egu24-2681, 2024.

The study of ontogeny in fossil organisms is vital to broader understanding of their ecology and evolution. Ontogeny in Tyrannosaurus rex (Theropoda: Coelurosauria) has been studied extensively by dinosaur researchers, documenting the transition from small juvenile to gigantic adult. Previous authors have regarded this transition as largely linear, serving as a model for understanding growth and development in other tyrannosaurids as well as theropods as a whole. However, the presence of sequence polymorphism (variation in the temporal order of developmental events) has yet to be investigated for this taxon, representing a potential source of error for published ontogenetic series. Here we present the first Ontogenetic Sequence Analysis (OSA) of Tyrannosaurus, recovering extensive sequence polymorphism in a previously published ontogenetic character matrix. In contrast to ontogenetic series of Tyrannosaurus recovered by cladistic ontogenetic methods, we find a significant correlation between maturity and body size among large adult specimens, and corroborate previous assertions of a relationship between histologic and morphological indicators of maturity. Our results highlight the prevalence of sequence polymorphism among saurischian dinosaurs, and demonstrate the importance of considering such variability when attempting to reconstruct the ontogeny of fossil vertebrates. We expect that further study will reveal similar variability across closely related taxa and recommend that this possibility be incorporated into interpretations of morphological variation in tyrannosaurids.

How to cite: Warshaw, E., Barrera Guevara, D., and Yu, E.: Ontogenetic Sequence Analysis Reveals Extensive Sequence Polymorphism in Tyrannosaurus rex, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2319, https://doi.org/10.5194/egusphere-egu24-2319, 2024.

This study is part of a larger research project (INSITE) - PRIN 2022 founded by MUR – Ministero dell’Università e della Ricerca. It is focused on two pilot sites to highlight the intrinsic potentialities of the paleontological heritage as a tool for valorising territorial resources, particularly referring to inner areas. These sites, Pietraroja (PTJ) and Le Ciampate del Diavolo (LCD), are areas of great paleontological importance, in the Campania region. The PTJ (Benevento) is the place where the fossil of a small dinosaur, Scypionix samniticus named CIRO, was found. The LCD ichnosite (Caserta) preserves elements that allow behavioural and structural evaluations of hominins of the middle Pleistocene. The main intention of the study refers to the attempt to broaden the spectrum of interest around these sites, suggesting mainstreaming the potentialities of the whole territorial context in which these sites are located. To identify innovative communication modalities and to develop a new knowledge model, we present here the reconstruction of Pietraroja paleoenvironment using technological tools. Using immersive technologies for virtual, augmented, and mixed-reality models, it is possible to build an immersive digital space in which the visitor will perceive the original environment and interact with the fossils' virtual avatar. The CIRO digital model was obtained based on complete information on the anatomical structure of Scipionyx samniticus and, through accurate 3D modeling, the digital model of the dinosaur was generated. The same approach was used to recreate the landscape and the marine and vegetation species.

How to cite: Amore, F. O., Argenio, C., Di Vito, M. A., Fistola, R., Messina, M. Y., Panarello, A., Rastelli, A., Zingariello, I., and La Rocca, R. A.: Improving the territorial awareness through paleontological heritage: preliminary results from Pietraroja site (southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12875, https://doi.org/10.5194/egusphere-egu24-12875, 2024.

The middle Eocene Eckfeld maar (c. 44 Ma) deposits in Germany are known for numerous well-preserved fossils they have yielded until today. Among these records, thousands of insects have been recorded that potentially provide direct evidence for flower visitations and entomophilic pollination processes. In order to obtain data on flower visits and possible pollinator roles, we extracted pollen from selected groups of fossil Coleoptera from Eckfeld and studied them with light microscopy (LM) and scanning electron microscopy (SEM). In total, we screened 332 Coleoptera: 51 Buprestidae (six with pollen), 21 Cerambycidae (two with pollen), 87 Chrysomelidae (four with pollen), 80 Elateridae (three with pollen), ten Eucnemidae (one with pollen), 78 Scarabaeidae (three with pollen), and five Throscidae (no pollen). The beetles were screened for both in situ pollen occurring in their digestive system and adhering pollen occurring on various parts of their exoskeleton (head, thorax, abdomen, leg etc.). The pollen was most frequently associated with members of Sagrinae, a subfamily of leaf beetles (Chrysomelidae), and Agrilinae, a subfamily of jewel beetles (Buprestidae). The adhering or in situ pollen can be assigned to at least 15 different taxa. While some are unique and only associated with one beetle specimen (e.g., Malvaceae, Moraceae), other pollen types were found associated with two or more beetle specimens, namely, Castaneoidea, Euphorbiaceae, Oleaceae, Onagraceae (Ludwigia), Sapotaceae, and Vitaceae (Parthenocissus).

How to cite: Bouchal, J. M., Geier, C., Ulrich, S., Uhl, D., Wedmann, S., Wappler, T., and Grímsson, F.: Fossil Coleoptera with in situ and adhered pollen from the Eocene of Eckfeld, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5326, https://doi.org/10.5194/egusphere-egu24-5326, 2024.

Pollination by insects, including flies, is commonly a mutualistic interaction, in which both the plant and the insect benefit. Compared to other groups of pollinators or flower visitors relatively little is known about flower visitation by flies (Diptera) during most of the Cenozoic. Until now, the fossil record has provided only a few reliable fossils where flies are preserved with in situ or adhered pollen from flowers they visited before death and fossilization. Here, we report preliminary results from an ongoing study on flower-dipteran interactions during the middle Eocene of Central Europe. We screened 220 Diptera (19 with pollen) from the Middle Eocene of Messel and 20 Diptera (one with pollen) from the Middle Eocene of Eckfeld. The flies were screened for in situ pollen in their digestive system and adhering pollen present on various parts of their exoskeleton (head, thorax, abdomen, leg, etc.). From Messel, we studied, among other Arthropoda, 65 Brachycera (=flies; eleven with pollen) and 93 Nematocera (incl. gnats and midges; six with pollen). Out of the 20 pollen-bearing specimens, one had both gut content and adhering pollen, seven had only gut content pollen, and twelve had only adhering pollen. Each fly had between one and seven different pollen types. The number of pollen types found on the flies suggests both oligo- and polylectic feeding behaviour depending on the taxon. Only a few of the same pollen types (four pollen types) were found on different flies. In total we discovered 19 different pollen types on all the fossil fly specimens. The pollen represents, among others, Araliaceae, Cornaceae, Hamamelidaceae, Juglandaceae, Lythraceae (Decodon), Oleaceae, Rutaceae, Sapotaceae, and Vitaceae (Parthenocissus). Surprisingly, four flies carried Juglandaceae pollen on their exterior, but today, this family is mainly wind-pollinated. The amount of in situ pollen discovered was, in most cases, filling the whole digestive system of the flies, suggesting long and active feeding from anthers of flowers. About half the flies bearing adhered pollen had considerable amounts on their exterior, suggesting they could be potential pollinators of the plants they visited, especially Araliaceae, Hamamelidaceae, and Sapotaceae.

How to cite: Geier, C., Bouchal, J. M., Ulrich, S., Uhl, D., Wedmann, S., Wappler, T., and Grimsson, F.: Eocene flower visitation of European Diptera and their potential pollinator role, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5607, https://doi.org/10.5194/egusphere-egu24-5607, 2024.

The Late Miocene – Pliocene is a time of significant environmental changes in western Eurasia. The intensified mountain building process between the Eurasian, African and Arabian plates restructured the regional landscapes, basins, and biotic record. It has resulted in dramatic palaeoenvironmental events, like the Messinian salinity crisis (MSC) in the Mediterranean, the shrinking of the Eastern Paratethys and the formation of present-day basins and highlands. During such prominent tectonic vents, the shift in climate contributed to formation of climatic barriers and/or corridors for the faunistic interchanges. Nevertheless, the role of tectonics the evolution of the past biotic record has been poorly studied. The Middle East as a region is considered a key paleobiogeographic tying point between Europe, Asia, and Africa and, thus, has played a vital role in the intercontinental dispersal of vertebrate communities. The present study focuses on the newly discovered late Miocene vertebrate site Tazhga in the NW Zagros belt, Kurdistan Region of Iraq. The fossiliferous horizon is enclosed in bioturbated floodplain deposits that belong to the upper Miocene fluvial deposits of the Zagros foreland Basin. This new vertebrate fauna will enable constraining the age of the deposits and shed light on the effect of tectonics on biogeography. We will compare the newly discovered fauna with local and more extensive regional scale fossil records in the Middle East to provide palaeobiogeographical information on the evolution of vertebrate communities of the region. Such data will enable us to clarify the role of the Arabia-Eurasia convergence during the late Miocene – Pliocene on both regional evolution of the biotic record and the intercontinental dispersals.

How to cite: Vasilyan, D., Koshnaw, R., and Ameen, F.: Tectonic and climatic controls on the vertebrate evolution in the Middle East: insights from a new late Miocene terrestrial vertebrate fauna from the NW Zagros foreland Basin in the Kurdistan Region of Iraq, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19039, https://doi.org/10.5194/egusphere-egu24-19039, 2024.

The Cenozoic Niger Delta formed after the separation of the African and South American plates.An integrated micropaleontology analysis was employed based on foraminifera studies  to determine age, biostratigraphic zonation, paleowaterdepth, paleosalinity and sea-level history of the well interval based on ditch cutting samples. Foraminifera preparation was based on standard micropaleontology preparation techniques and identification, which showed a high diversity and abundance of both planktonic and benthonic foraminifera occurrence. The planktonic foraminifera: Globigerinoides bulloidues, Globigerinoides primordius, Globorotalia obesa, Globigerinoides sp.,Catapsydrax stainforthi showed the entire deposition took place during the early to late Miocene (N6-N17) based on the First Downhole Occurrence (FDO) and Last Downhole Occurrence (LDO).The boundary resolution between the Early and Middle Miocene was identified based on the FDO of Catapsydrax stainforthi and the boundary between Middle and Late Miocene based on the FDO Globorotalia obesa. Two benthic biozones are proposed for the well interval equivalent to the N11-N17 and N6-N11 based on bioevents of chronostratigrahically significant benthonic foraminifera and whose stratigraphic range were well established in the Niger Delta and worldwide. Three third-order sea-level rises and falls occurred during the Early to Late Miocene within the Niger Delta, with a corresponding paleo-waterdepth from transitional to outer neritic based on biofacies such as ; Ammonia beccarii, Quinqueloculina microcostata, Poritextularia panamensis, Uvigerina subperegrina, Brizalina mandoroveensis, Lenticulina grandis and Eponides eshira.The maximum flooding surfaces shown by,the Chiloguembelina-3 Shale (16.0 Ma), Dodo Shale (11.6 Ma) and the Uvigerina-8 Shale (9.2 Ma), were associated with transgression. The 15.5 Ma SB of Depositional Sequence 1(Early Miocene), 10.5 Ma SB of Depositional Sequence 2(Middle Miocene) and 8.5 Ma SB of Depositional Sequence 3(Late Miocene) due to progradation, resulting in three depositional sequences established within the study interval. This showed  that the study interval was exposed to three local depositional cycles (cycle 6,9and 10), three regional cycles (cycles 2.3,2.6 and 3.1) within the TB2  and TB3 super cycles, correlated to the Niger Delta chronostratigraphic sea-level chart, which indicated that the sedimentary cyclic pattern was due to tectonics, eustatic and climatic conditions. Based on the triangular plot of the foraminifera test type (arenaceous, porcelaneous and hyaline), suggests a transition from the brackish marginal marine environment to open neritic conditions. The study interval is said to have penetrated sediments of the parallic Early to Late Miocene Agbada formation.

Keywords: Biostratigraphy, Early-Late Miocene, Planktonic Foraminifera, Benthic Foraminifera, sedimentary cyclic pattern

How to cite: Solomon, J. A., Obiosio, E., Ibrahim, H., Gospower, U., and Anyanna, L.: Neogene biostratigraphy in the  Niger Delta by  intergrating  foraminifera and  Paleo-oceonographic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1204, https://doi.org/10.5194/egusphere-egu24-1204, 2024.

Sedimentary records from passive continental margins can be used to reconstruct regional climate–ocean trends while identifying mass transport deposits (MTD) and elucidating their characteristics and timing in relation to regional paleoclimate and paleoseismicity. This study used two radiocarbon-dated piston cores from the Southeastern Mediterranean continental slope that cover the Holocene period. The cores were collected from the shelf edge (122 m depth) and the mid slope (588 m depth) to the north east of the Nile Delta at the Dor Disturbance off-shore Israel.

Computed Tomography (CT) scanning showed the sedimentary record evolved along the Holocene representing a gradual change in the sediment grain size and composition, while detecting units of MTD. The base of the cores was dated to 10-11 ka BP, and the shelf edge core captured the transgression on the continental shelf. The Early Holocene sediments are characterized by coarser grain size, higher content of biogenic material and highest foraminiferal abundances that reflect stable and favorable environmental conditions. Sapropel S1 is recorded as the lowest Ti/Al and the highest Si/Al values and TOC content that indicate higher precipitation in the source region and the high discharge of Nile. The disappearance of benthic foraminifera in the slope core point to the development of bottom water anoxia. During the time interval of sapropel formation, a clear interruption is observed by a decrease in TOC and a moderate presence of benthic foraminifera indicating re-oxygenation of the see-floor in corresponds with the ~8.2 ka BP cold event. Towards the mid Holocene the Ti/Al ratio and Fe contend increase in association with the increase of weathering rates in the Ethiopian Highlands at the Nile watershed as a result of reduced rainfall, and thus reduced vegetation cover. This trend aligns well and correlates with the many studies documenting a middle to late Holocene orbital change that led to the decrease of solar insolation forcing southward migration of the summer ITCZ and a gradual decrease of monsoon precipitation making this region increasingly arid.

In the slope core, four units were identified in the CT scanning as relatively higher bulk density sediments, which is consistent with enhanced consolidation and reduction in porosity, observed in MTDs. Older and out of stratigraphical order radiocarbon ages within these MTD units point to deposition of recycled sediments. Interestingly, the Ca/Fe ratios showed prominent peaks and distinct changes are observed in the benthic foraminifera community including the total number of individuals per gram dry sediment (BF/g), species richness, dominance, and species composition. Furthermore, within all the MTD units a noticeable increase in broken BF shells is also detected. It is noteworthy that the abundances of the opportunistic benthic species stay moderately high in between MTD events, probably reflecting the instability of the benthic habitat.

How to cite: Bookman, R., Harmon, Y., Makovsky, Y., Kanari, M., Boaretto, E., Garrett, E., and Avnaim-Katav, S.: Multi-proxy analysis for deciphering the Holocene record and mass transport processes at the Dor Disturbance in the Southeastern Mediterranean continental slope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13015, https://doi.org/10.5194/egusphere-egu24-13015, 2024.

In order to clarify the sedimentary system evolution and sandbody development characteristics of Shaximiao Formation, this paper takes the Shaximiao Formation in the central Sichuan Basin as the research object to systematically study the sedimentary microfacies and sandbody genetic types of Shaximiao Formation by using core data, thin section analysis, logging and seismic data comprehensively. And the following research results are obtained.

First, due to the gradual uplifting of the Daba Mountain and the Micang Mountain on the northeast, the Sichuan Basin was a NE-SW trending foreland basin during the sedimentation of Shaximiao Formation, the topography in the basin was wide and gentle and the ancient water system was mainly in the NE-SW direction, so the sedimentary pattern of Shaximiao Formation in the central Sichuan Basin is under the joint control of the Daba Mountain on the north and the provenance on the south.

Second, glauconite minerals are common in the sandstone of the central Sichuan Basin, indicating that the depocenter of Shaximiao Formation is located in the center of the basin. Shaximiao Formation is characterized by frequent alternation of dry and wet climate, shallow and turbulent lake basin and wide and gentle terrain, and has the sedimentary background to form shallow water deltas.

Third, the shallow water deltas developed in the first Member of Shahejie Formation under the condition of semi-arid climate are mostly in the shape of lobate, with a wide distribution of sedimentary facies. In the plane, they are presented as a complex of multiple lobates, sandbodies are overlapped and developed continuously, single-phase channel sandbodies are wide and river mouth bars are common.

Fourth, branched distributary channel-type shallow water deltas are mainly developed in the second Member of Shahejie Formation under the condition of arid climate, and they are mostly in the shape of bird’s foot or branch. Sandbodies are distributed in strips along channels, which are narrow and cut each other. River mouth bars are only distributed at the channel end, with a small single scale.

In conclusion, this paper systematically analyzes the evolution and distribution laws of sedimentary facies of Shaximiao Formation in the central Sichuan Basin and summarizes the sedimentary characteristics and sandbody development models of Shaximiao Formation.

How to cite: Liang, W., Qiu, L., and Yang, Y.: Sedimentary system evolution and sandbody development characteristics of Jurassic Shaximiao Formation in the central Sichuan Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2398, https://doi.org/10.5194/egusphere-egu24-2398, 2024.

The most widely distributed shallow marine sandy formations in the western foothills of Taiwan is the Guizhulin Formation of late Middle Miocene to early Pliocene age, along with its contemporaneous strata. Its facies transition is also the most prominent, exhibiting an overall trend of increasing sedimentary environment depth from north to south. The lower part of the Guizhulin Formation in northern and central Taiwan, is of late Middle Miocene age and can be correlated to the Tangenshan Sandstone in southwestern Taiwan. According to numerous previous studies, in terms of tectonic evolution for the western foothills terrain, the former have been regarded as the accumulation in the early stage of the foreland basin (syn-orogenic) to the north of the Peikang High, whereas the latter represents the deposits in the passive continental margin stage (pre-orogenic) to the south of the Peikang High. In order to understand the sedimentological distinction between the lower part of the Guizhulin Formation and Tangenshan Sandstone, this study reconstructs and analyzes stratigraphic columns and lithofacies of the Tangenshan Sandstone, which is approximately 380 meters thick and exposed in the hanging wall of the Chutouchi Fault in the Kueitanchi section in the Tainan area, southwestern Taiwan. Observations and records of trace fossils were also utilized to comprehensively reveal the variations in sedimentary environment and the characteristics of depositional facies in the study area. The aim of this study is to investigate the tectonic implication for the variations in the sedimentary environment based on the sedimentology study results.

Based on the descriptions in the field, the lithofacies can be categorized into one mudstone facies, two siltstone facies, and three sandstone facies. According to the lithofacies association, they can be further subdivided into channel deposits and non-channel deposits, indicating two distinct sedimentary features. It is inferred that the sedimentary environment during the deposition was primarily an offshore depositional system dominated by storm wave and possible turbidity currents. Lithofacies association indicates that the thick sandstone layers in the study area were transported deeper in the continental shelf by turbidity currents induced by storms. These currents carried coarse-grained sediments below the average storm wave base, resulting in the formation of submarine channels and finer-grained non-channel deposits. The overall sedimentary characteristics resemble those of shallow water turbidite deposits in terms of features and mechanisms. Furthermore, with comparison with previous research results, it is inferred that the deposition of the Tangenshan Sandstone in the study area was in an atypical passive continental margin environment but rather influenced by pre-orogenic normal faulting, leading to an increase in thickness but decrease in sedimentary environment depth of the contemporaneous Tangenshan Sandstone deposits from the west (basin margin) to the east (basin center).

How to cite: Tang, T.-K., Lin, G.-W., Wu, L.-C., Yang, K.-M., and Chang, S.-P.: Sedimentary environment of Tangenshan sandstone in southwestern Taiwan and its tectonic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4882, https://doi.org/10.5194/egusphere-egu24-4882, 2024.

The shallow water delta sand bodies within the Jurassic Shaximiao Formation in the Sichuan Basin play a crucial role in tight gas exploration. The efficient exploration of these areas is hindered by the establishment of the favorable reservoirs’ model. The Zitong area, situated on the northwest of the Sichuan Basin, is of particular interest. The Shaximiao Formation in this region can be subdivided into the first and second members, separated by dark leaf limb shale. The first member primarily features delta-lacustrine sediments, while the second member is dominated by fluvial-lacustrine sediments. In this study, we focus on the tight sandstone clastic reservoir within the Shaximiao Formation in the Zitong area.

Through core observations from four wells and a comprehensive analysis involving conventional slices, casting section, scanning electron microscopy, high-pressure mercury injection, nuclear magnetic resonance, and core plunger porosity and permeability, we explore the reservoir's development characteristics and controlling factors from both sedimentation and diagenesis perspectives.

The research reveals the following findings:

• The reservoir components in the Zitong area are mainly composed of medium to fine-grained feldspar lithic sandstone and lithic feldspar sandstone. The primary reservoir space is intergranular pores, followed by intragranular dissolution pores. Porosity is mainly distributed in the range of 7-10%, and permeability ranges from 0.1-1.0 mD. While different subsegments exhibit varying physical properties, the overall characteristics indicate low porosity and ultra-low permeability, with the predominant reservoir type being pore type.
• The advantage of relatively high-energy and stable sedimentary facies is crucial for high-quality reservoir formation. The underwater distributary channel in the delta front of the Shaximiao Formation serves as a favorable facies zone for high-quality reservoir development. Variations in particle size, sorting, and mud content contribute to the reservoir's properties, with the middle sandstone presenting optimal conditions for reservoir development.
• Compaction and cementation emerge as the primary mechanisms reducing porosity. Utilizing the Ehrenberg (1989) model, calculations indicate that cementation contributes approximately 25.42% to porosity reduction, while compaction contributes 65.07%. Vertical distribution differences in zeolite and calcite contribute to variations in reservoir properties.
• The dissolution of feldspar and the development of chlorite crust are identified as key factors in high-quality reservoir formation. Factors such as the preservation of primary pores, strong dissolution, weak cementation, and the role of chlorite thin films influence the constraints on high-quality reservoir development. The preservation of primary pores is particularly associated with the formation of chlorite thin films.

These findings contribute valuable insights into understanding and optimizing the exploration and development of tight gas reservoirs within the Shaximiao Formation in the Zitong area.

How to cite: Hu, Y. and Yang, Y.: Development characteristics and main controlling factors of tight sandstone reservoirs in the Shaximiao Formation in Zitong area, Sichuan Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7040, https://doi.org/10.5194/egusphere-egu24-7040, 2024.

We present a heavy minerals study of several sedimentary units deposited within the Yukon-Koyukuk basin (YKB) in Alaska. The YKB started to form in middle to late Jurassic after the collision between an intraoceanic volcanic arc and the Arctic Alaska margin. The collision led to thrusting of the seafloor (mafic and ultramafic rocks of the Angayucham Terrane), over the future Brooks Range and Ruby Terrane. The basin is flanked on three sides by metamorphic rocks of the Seaward Peninsula to the west, the Ruby terrane to the east and the Brooks Range to the north. The remnants of the volcanic arc (Koyukuk Arc Terrane, KAT) divide the basin into a northern Kobuk-Koyukuk basin (KKB) and a southern Lower-Yukon basin (LYB).

We present results from the Kv, Kvg, Ks, Kms, Kmc, and Kqc units (after Patton et al.2009), collected along the Koyukuk and the Yukon rivers. The units are as follows:

• Kv: formed by basaltic and andesitic lava flows interbedded with volcanogenic conglomerate to mudstone rocks. K-Ar ages vary from 134 Ma and 118 Ma with a U-Pb age obtained through a tuff of about 138 Ma.
• Kvg: mainly consists of volcaniclastic greywacke and mudstone interbedded with tuffaceous layers which gave U-Pb ages comprised between 112 and 110 Ma (Albian). Molluscs of the same time have been reported throughout the entire unit.
• Kms: mainly fine to coarse sandstone interbedded with shaly layers. Interpreted to be the marine tongue of the Ks deposits.
• Ks: late Cretaceous in age, this unit consists of alternations of sandstone and shale layers deposited in fluvial to shallow marine environments.
• Kmc: mafic igneous clasts conglomerate with mafic and calcareous greywacke and mudstone. Marine molluscs of Cretaceous age have been found.
• Kqc: overall a quartz rich unit composed of conglomerate, sandstone and mudstone. Plant fossils date the unit to the Cretaceous.

We use Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN®) for heavy mineral (HM) analysis to establish a clear relationship between sediments and source regions and build a model for the basin formation and evolution. Kv and Kmc samples reflect a volcanic source, while Kvg, Kms, Ks, and Kqc display the progressive unroofing of deeper and higher grade metamorphic rocks. Combining these data with DZ and U-Pb absolute ages, we interpret the YKB to be formed prior to 138 Ma as the forearc basin of the intraoceanic arc. It evolved into a hinterland setting at about 110 Ma when the first deposition of metamorphic detritus is recorded by the Kvg unit, mainly derived from erosion of the Brooks Range.  Limited paleocurrent data along with the novel HM data attribute the Ks, Kms, Kmc and the Kqc to the erosion of the Ruby terrane as it uplifted during middle to late Cretaceous time.

How to cite: Seminara, S., Pease, V., and Toro, J.: Heavy mineral analyses to reconstruct basin evolution, an insight from the Yukon-Koyukuk basin sandstones, Alaska. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5303, https://doi.org/10.5194/egusphere-egu24-5303, 2024.

Tidal-dominated estuaries are a type of depositional system that is highly dynamic under the influence of tides. The interaction intensity between fluvial, tidal, and wave currents varies vertically along the coastline, resulting in a unique pattern of longitudinal gradient changes of facies associations and sediment distribution. Compared to river and delta sediments, research on ancient estuarine sediments is relatively limited. In this study, we analyzed observable data from the Late Cretaceous M1 Sandstone formation in the central northern region of the Oriente Basin, conducted in-depth research on its sedimentary characteristics, and proposed a tidal-dominated estuarine sedimentary model of this region. The rich core data provides reliable support for identifying sedimentary sequences of tidal environments, identifying a total of 14 lithofacies and 6 main types of facies associations, including tidal sand bars, tidal channels, and four types of tidal flats. These 6 types of facies associations correspond to the sediment accumulation characteristics in different sedimentary zones of the estuary, reflecting the differences in hydrodynamic conditions during the sedimentation process, such as strength, combination, and directionality. Furthermore, under the constraint of a dense well network, a detailed study of the stratigraphic pattern and deposit thickness was conducted to establish a matching relationship between sediment distribution characteristics and hydrodynamic characteristics in the entire region, providing sedimentary evidence for identifying tidal-dominated estuaries. Additionally, based on the combination relationships of tidal sequences, it was determined that there is a set of short-term sea level rise-fall cycles during episodic marine transgressions. The facies change of estuaries is sensitive to the response of sea level fluctuations. The results indicate that tidal sand bars are generally developed at the bottom of the tidal sequence. As the sea level decreases, the outer area is gradually covered by the tidal flat, of which the periodicity of the interior is clearer than that of tidal sand bars. Our research indicates a transition process from estuaries to deltas in the tidal system of M1 Sandstone formation under the influence of sea level fluctuations. The results provide evidence for a better understanding of the evolution of estuarine sediments in ancient strata.

How to cite: Zhu, S., Sun, P., and Xu, H.: Paleogeographic reconstruction and sedimentary evolution of tidal-dominated estuarine depositional systems: Insights from ancient deposit records of the Oriente Basin M1 Sandstone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14770, https://doi.org/10.5194/egusphere-egu24-14770, 2024.

This comprehensive study explores the Upper Pleistocene geological history of Mallorca, employing a multifaceted approach that integrates previous findings with new insights. The research spans various coastal regions, focusing on four distinct study areas characterized by different geomorphological and structural contexts. The first structural context, exemplified by Port des Canonge, showcases folded and thrusted deposits, resulting in prominent cliffs with Jurassic and Triassic formations. The second context, observed in Caloscamps, features smoother reliefs and notable terrestrial sediment input. Meanwhile, the third context, represented by Punta de s’Avançada and Punta de n’Amer, exhibits cliffs  carved on Upper Miocene tabular deposits devoid of terrestrial sediment input. The main objective is to provide a comprehensive understanding of the geological and sedimentological characteristics of the Upper Pleistocene deposits across Mallorca's coastal regions by investigating different study areas located along the west, north-west, north-east, and east coasts, in distinct geomorphological and geological contexts through a multifaceted approach using classical sedimentological methodologies: stratigraphic analysis, X-ray analysis, microscopic techniques, and assessment of sediment color. Additionally, Optically Stimulated Luminescence (OSL) dating techniques are employed, providing a precise temporal framework spanning Marine Isotope Stage 6 (MIS 6) to Marine Isotope Stage 3 (MIS 3). The findings reveal the complex interplay of environmental factors, climatic variations, and geological evolution across Mallorca. Colluvial deposits and paleosols reflect climatic shifts. Alluvial fans and aeolianites highlight periods of intense sediment transport and deposition linked to climate fluctuations. Fossil evidence, such as tracks and trackways associated to Myotragus balearicus, contributes to understanding evolutionary adaptation and isolation, offering unique insights into the island's paleontological legacy. Finally, to provide a comprehensive overview of the outcrops present on the island, a stratigraphic correlation of the mentioned areas was conducted, integrating data from seven other study sites (Es Caló, Punta Manresa, Platja de sa Font de Sant Joan, Sa Ferradura, s’Estret des Temps, Es Carnatge and Ses Penyes Rotges). In conclusion, the study enhances our comprehension of Mallorca's coastal dynamics, geological composition, and environmental history, providing invaluable contributions to the broader understanding of Pleistocene deposits.

How to cite: Perazzotti, F., Del Valle, L., Gómez-Pujol, L., and Fornós, J. J.: Upper Pleistocene in Mallorca: Sedimentary variability of littoral deposits in relation to different structural contexts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6084, https://doi.org/10.5194/egusphere-egu24-6084, 2024.

During the lower sub-member sedimentary period of the third member of the Shahejie Formation in the Boxing Sag, a transition from a humid to an arid climate occurred. Concurrently, the lacustrine basin experienced accelerated subsidence, leading to the development of thick-layered sand bodies caused by gravity flow. Provenance restoration plays a pivotal role in determining the location, properties, and sediment transport path of these sand bodies. This restoration was instrumental in predicting sand body distribution and holds great significance in elucidating the laws governing oil and gas accumulation.The study focused on the lower part of the third member of the Shahejie Formation in the western section of the Boxing Sag, undertaking a comprehensive investigation of sedimentary and provenance characteristics.

Core wells were observed, with 50 wells having a total core length of 2547m, and over 7000 core photos were analyzed to elucidate main facies types and sedimentary landmarks in the study area. Heavy minerals and cuttings were systematically analyzed, contributing to the restoration of the provenance system. By studying typical drilling cores and logging data, the sedimentary facies of individual wells and continuous wells were determined. A sedimentary development model was established based on sand body assemblage types and spatial distribution laws. Finally, through the integration of sand dispersion system analysis, seismic attribute technology, and paleogeomorphology, a sedimentary system plan for the study area was formulated.

The results show that the provenance area can be categorized into three types based on rock types and heavy mineral characteristics in the provenance area: the northwest source area, the western provenance area, and the southern provenance area. The northwestern, western, and southern provenance areas exhibited stable development during the study period, with heavy mineral assemblages remaining consistent on the horizontal development. Meanwhile, The turbidity fan in the study area primarily originated from the northwest provenance area, with minimal influence from the western and southern provenance areas on the cross-section. The characteristics of the lower provenance system of the third member of the Shahejie Formation in the Boxing Sag were clarified. Main sand body types and facies markers were summarized, leading to the establishment of an accurate sedimentary development model.

To sum up, this research aims to elucidate the accumulation laws of oil and gas reservoirs, providing a theoretical and data foundation for the identification and exploration of favorable areas, ultimately minimizing exploration risks.

How to cite: Yan, S. and Yang, Y.: Research on Sedimentary and Provenance Characteristics of the Lower Sub-member of the Third Member of Eocene Shahejie Formation in Boxing Sag, Dongying Depression, Bohai Bay Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7025, https://doi.org/10.5194/egusphere-egu24-7025, 2024.

We document medial shelf parasequences in the Upper Albian Sikanni Formation in the Liard Basin, Northwest Territories, Canada, deposited during a greenhouse climate in the Western Interior Cretaceous Seaway. It is characterised as a fine-grained glauconitic sandstone with argillaceous shales, ranging approximately 100 to 300 metres in thickness. We measured 111 metres of section, passing from sandier to more distal shale facies towards the contact with the conformably overlying Sully shale, indicating an overall deepening. The sandier section shows well-organised upward coarsening facies successions, transitioning from wave to hummocky cross stratified sandstones to pervasively bioturbated sandstones, dominated by Zoophycos to distal Cruziana ichnofacies, interpreted as a medial shelf environment. There are at least 8 well-expressed parasequences in the sandier lower part of the section, transitioning into more uniform shalier units near the contact of the Sully Formation. The sandier parasequences are sharply bounded by shales forming well-expressed ‘simple parasequences’. Simple parasequences are defined as upward-coarsening facies successions lacking evidence of key bounding surfaces indicating bypass or subaerial exposure, such as lag deposits, roots, or transgressive erosion. These are distinguished from ‘complex parasequences’, commonly containing these features. The changing environment of the more uniform muddier facies can be distinguished using increases and decreases in bioturbation, corresponding to lower and higher sedimentation rates, respectively. The Sikanni units lack evidence of subaerial exposure, indicating that it is unlikely the parasequences shallowed up to the shoreline. Nevertheless, these cycles are well-expressed, suggesting that simple parasequences can be identified in medial shelf environments. Additionally, a guiding framework based on Dene (First Nations) principles was developed as a basis for this project. The phases on the framework are: (1) Decolonisation of the Self, (2) Building Relationships and Community Consultation, (3) Community Entry and Data Collection, (4) Data Analysis, and (5) Knowledge Translation and Dissemination. A special thanks to Acho Dene Koe First Nation in the community of Acho Dene Koe, Northwest Territories, for graciously welcoming us onto their lands, into their community, and allowing us to share the geologic stories of the rocks they have coexisted with since time immemorial.

How to cite: Abi Daoud, A. A. and Bhattacharya, J. P.: Simple parasequences in a medial shelf setting: Albian Sikanni Formation, Northwest Territories, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14129, https://doi.org/10.5194/egusphere-egu24-14129, 2024.

  The fan delta reservoir is developed in many basins in China widely, with which internal sand body structure is complex and strong heterogeneity. It is of great significance for the development of high water cut oilfield to determine the single sand-body superposed pattern and the development characteristics of inside the single sand-body in reservoir.Taking the upper Es3 in Gangzhong Oilfield, Huanghua Depression as an example, this paper studies the reservoir architecture characteristics and heterogeneity of the fan delta front.Most of the studies on reservoir architecture of fan-delta front at home and abroad focus on identification and quantitative characterization, but the characteristics and heterogeneity of architecture units under the constraints of a Multi-level interface are not explained.In view of the above problems, the author combined core, well logging and seismic data and took sedimentary genetic model as the constraint condition to quantitatively characterize the architecture interface in hierarchical order. Through the classification of architecture levels, the characteristics of composite genetic sand body and single genetic sand body and the study of heterogeneity, the reservoir architecture and heterogeneity of the upper submember of Sha3 in Gangzhong Oilfield were revealed. It provides a powerful theoretical basis for the subsequent exploitation of oil fields.

  Specific steps include: (i) Combined with the sedimentary background of the fan delta front and the actual situation of the working area, the fine anatomy of the single genetic sand body and the composite genetic sand body is carried out by using the data of the dense well pattern, and the architecture model of the fan delta front in the study area is improved; (ii) Based on the identification marks of the architecture interface, the development characteristics of the architecture units constrained by the interface at all levels were defined, the overlapping mode inside the composite genetic sand body and the distribution characteristics of the sand body on the plane were established, and the characteristics of the single genetic sand body were described. The heterogeneity inside the architecture unit was analyzed according to the data, and finally the control effect of the reservoir heterogeneity was clarified by combining the sedimentary and tectonic processes; (iii) Through dynamic and static analysis, the remaining oil distribution model under the control of different reservoir architectures is established. The control effect of multi-stage architecture on remaining oil distribution is clarified, and the understanding of the control effect of reservoir architecture on remaining oil can provide reference for the exploitation of potential in the later stage of high water cut old oil field.

How to cite: Wei, T.: Study on reservoir architecture characteristics and heterogeneity of the fan delta front, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10444, https://doi.org/10.5194/egusphere-egu24-10444, 2024.

To understand the influence of downstream changes in hydrodynamics on floodplain sedimentation and associated channel avulsion in stream-dominated alluvial fans, we studied the Cretaceous Duwon Formation in the southern Korea (Goheung area). The Duwon Formation unconformably overlies the Paleoproterozoic basements and mainly consists of braided stream and calcrete-bearing floodplain deposits. Close to the basements, channel deposits show radial paleoflow patterns, and the sediment size and ratio of channel to floodplain deposits decrease downstream over a relatively short distance (< 7 km). These lines of evidence indicate that the Duwon Formation was deposited in the stream-dominated alluvial fans under arid to semi-arid climatic conditions, which can be classified into the proximal, medial, and distal zones. In the medial zone, floodplain deposits are mainly composed of purple sandstones and compensational stacked crevasse channel and splay deposits with unsystematic paleoflow directions. Whereas in the distal zone, floodplain deposits are mainly composed of purple mudstones with calcretes and vegetation traces. They are interbedded with and overlain by progradational stacked (coarsening- and thickening-upward trends) crevasse channel and splay deposits with constant paleoflow directions. These floodplain deposits are finally overlain by braided stream deposits as a result of channel avulsion. In the medial zone, as the relatively high stream flood discharge caused frequent overbank flooding and formed multiple breaching points in channel levees, crevasse channel and splay deposits were compensational accumulated via these breaching points. On the other hand, in the distal zone, the relatively low stream flood discharge commonly supplied fine-grained sediments into floodplains, resulting in the deposition of purple mudstones. Once channel levees collapsed, vegetation stabilized the breaching point of channel levees, progressively incised by the multiple flooding events. Overbank floodwaters through the relatively stabilized-breaching point led to a continuous supply of coarse-grained sediments, resulting in progradational stacked crevasse channel and splay deposits. Thus, floodplain sedimentation, accumulation of crevasse channel and splay deposits, causes rapid filling of accommodation space in the proximal floodplains. With in-channel bed aggradation, their accumulation resulted in the growth of alluvial ridges and a gradual increase in the cross-floodplain topographic gradient. When the channel bed is sufficiently perched above the distal floodplains by alluvial ridge growth, the gradient advantages caused channel pathway to shift on floodplains with the formation of a new channel (channel avulsion). This study suggests that downstream changes in hydrodynamics and associated floodplain sedimentation are important for channel avulsion and thus, ultimately influence sediment dispersal patterns on the stream-dominated alluvial fans (fan-building processes).

How to cite: Lee, K. and Gihm, Y. S.: Influence of downstream changes in hydrodynamics on floodplain sedimentation and resultant channel avulsion in stream-dominated alluvial fans: An example from the Cretaceous Duwon Formation in the southern Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6881, https://doi.org/10.5194/egusphere-egu24-6881, 2024.

  The subaqueous coarse clastic rock fans in the Northern Bonan Depression of the Bohai Bay Basin are one of the typical reservoirs for oil and gas accumulation in the Mesozoic-Cenozoic continental rift basin. With the comprehensive exploration of oil and gas fields in eastern China transitioning from the concealed exploration phase to the refined exploration phase, the lack of understanding of the internal structure and distribution law of favorable zones within the subaqueous coarse clastic rock bodies has seriously hindered the exploration and development of such oil and gas reservoirs. This paper focuses on the subaqueous coarse clastic rocks of the third member - fourth member of the Shahejie Formation（Es3–Es4） of Northern Bonan Depression as the research objects. By integrating seismic, logging, core, and analysis tests, investigating the genetic types, sedimentary structures, and transport processes of subaqueous coarse clastic rocks under differential tectonic activities. Furthermore, a comparative analysis of reservoir characteristics and the main controlling factors for reservoir properties are carried out for different types of subaqueous coarse clastic rock bodies, aiming to provide a clear understanding of the development mechanisms of high-quality reservoirs. The following understandings have been obtained.

（1）A sedimentary evolution sequence of subaqueous coarse clastic rocks controlled by differential tectonic activity is proposed. In Es4, thesegments of the boundary faults experience a low tectonic subsidence rate, relatively gentle topography, and sufficient sediment supply, fan deltas form. The subaqueous distributary channels cut each other, migrate and swing frequently, resulting in a wide lateral distribution of the fans.In Es3,the segments of the boundary faults experience high tectonic subsidence rates and large drops, which contribute to the development of nearshore subaqueous fans. The internal migration and superposition of multi-stage fan bodies occur, while the lateral migration capacity of braided channels is weak, and vertical accretion dominates the overall deposition.

（2）This study has identified the differences in lithology, reservoir characteristics, main authigenic mineral types and contents of subaqueous coarse clastic fans during the third member - fourth member of the Shahejie Formation of Northern Bonan Depression。The parent rock of fan delta is mainly composed of metamorphic rocks, while the nearshore subaqueous fans consists of metamorphic rocks and mixed parent rock. The reservoir space type is dominated by feldspar and igneous rock fragment dissolution pore. The highest pore surface porosity is found in the fan delta, followed by the nearshore subaqueous fans。

（3）Quantitatively evaluated the differences in diagenesis subaqueous coarse clastic rock reservoirs during the third member - fourth member of the Shahejie Formation of Northern Bonan Depression，and clarified the types of favorable sedimentary facies belts. The sedimentary environment of the fan delta shows medium compaction, weak cementation, and strong dissolution, medium to strong compaction, medium to strong cementation, and weak to strong dissolution for the nearshore subaqueous fans。 The subaqueous distributary channel of fan delta, braided channels in the nearshore subaqueous fan are the most favorable sedimentary facies。

How to cite: zou, Y. and Qiu, L.: Depositional Characteristics and Reservoir Formation Mechanism of Subaqueous Coarse Clastic Rocks along Steep Slopes in a Continental Lacustrine Rift Basin: A Case Study of Northern Bonan Depression, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2530, https://doi.org/10.5194/egusphere-egu24-2530, 2024.