SSP1.1 | Open session on stratigraphy, sedimentology and palaeontology
EDI PICO

This session offers stratigraphers, sedimentologists and palaeontologists an opportunity to present papers that do not fall within research areas covered by this year's special themes. The PICO format provides the maximum opportunity to present research on diverse themes to the widest possible audience.

Convener: Marc De Batist | Co-conveners: Wessel van der SandeECSECS, Francesco Salese, Cinzia Bottini, Alicia FantasiaECSECS, Madeleine VickersECSECS, Guilhem Amin DouilletECSECS
PICO
| Mon, 24 Apr, 14:00–18:00 (CEST)
 
PICO spot 2
Mon, 14:00

PICO: Mon, 24 Apr | PICO spot 2

Chairpersons: Cinzia Bottini, Francesco Salese, Wessel van der Sande
14:00–14:05
Sediment facies
14:05–14:07
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PICO2.1
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EGU23-255
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SSP1.1
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Virtual presentation
Diagenesis and pore evolution in thermal simulation-a case study of fine-grained sedimentary rocks in Kong2 member of Cangdong sag
(withdrawn)
Lingzhi Yin
14:07–14:09
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PICO2.2
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EGU23-256
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SSP1.1
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Virtual presentation
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GuoZheng Feng

Cangdong sag is an important oil-rich sag in Bohai Bay Basin, eastern China. Organic-rich fine-grained sedimentary rocks with a thickness of 400m are developed in the second member of Paleogene Kongdian Formation, which have good shale oil resource potential. However, there are few studies on diagenesis of fine-grained sedimentary rocks in Kong-2 member of Cangdong sag, especially the study on pore-increasing and pore-reducing mechanism based on diagenesis is insufficient, which restricts the fine evaluation of shale oil reservoir performance in different lithofacies and stratigraphic units.

Based on the qualitative analysis of core observation description, rock thin section analysis and scanning electron microscopy of Well G108-8 , Well GD12, and Well GX12X1 in Cangdong sag, combined with quantitative characterization techniques such as XRD whole rock analysis, XRD clay mineral analysis and energy spectrum analysis, it is clear that the diagenesis of fine-grained sedimentary rocks in the second member of Kong in Cangdong sag includes compaction, cementation, dissolution, metasomatism, clay mineral transformation and thermal evolution of organic matter. Because of the widespread development of cristobalite in Cangdong sag, a large number of cristobalite cements are filled in cracks or intergranular pores. The thermal evolution of organic matter is mainly characterized by internal hydrocarbon generation pores and marginal contraction joints. Under the scanning electron microscope, it is observed that the organic matter in the second member of Kong Formation in Cangdong sag is easy to combine with clay minerals to form 'organic matter-clay aggregate'. The conversion process of clay minerals can catalyze the hydrocarbon generation of organic matter, thus promoting the development of organic pores in the aggregate. Corrosion is common in the second member of Kong in Cangdong sag, mainly developed feldspar and carbonate rock corrosion. Under the influence of organic acids released from hydrocarbon generation of organic matter, corrosion pores formed by dissolution are more likely to be seen in unstable minerals in carbonate or clastic lamina adjacent to organic matter.

According to the data of porosity and permeability, pressure porosity and permeability, gas adsorption, high pressure mercury injection and nuclear magnetic resonance, the reservoir characteristics of Kong 2 member in Cangdong sag are analyzed. The results show that the porosity of the fine-grained sedimentary rock reservoir in Kong-2 member of Cangdong sag is between 0.24% and 9.35%, with an average of 2.95%. The permeability is between (0.01-25.3) × 10-3μm2, with an average of 0.613 × 10-3μm2, and the overall reservoir is ‘ultra-low porosity and ultra-low permeability’. Pores include inorganic pores, organic pores and micro cracks. The pore size is small, mainly micro-nano pores.

The influence of diagenesis on the reservoir of the second member of Kong Formation in Cangdong sag is complex, including the mechanism of increasing porosity and reducing porosity. The pore-increasing mechanism includes thermal evolution of organic matter, dissolution and clay mineral transformation;compaction and cementation are the main factors affecting the porosity and permeability of the reservoir, which belong to porosity reduction for the reservoir of Kong 2 member in Cangdong sag.

How to cite: Feng, G.: Diagenesis Types of Fine-grained Sedimentary Rocks in the Ek2 of Cangdong sag and Their Influence on Reservoirs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-256, https://doi.org/10.5194/egusphere-egu23-256, 2023.

14:09–14:11
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PICO2.3
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EGU23-979
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SSP1.1
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ECS
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Virtual presentation
Xudong Liu

Area A is located in the east of Yangjiang Sag in Zhusan Depression, Pearl River Mouth Basin. The Neogene Hanjiang Formation in this area has deposited a large number of sand, silt and mud mixed clastic sediments, with different particle sizes and complex composition. Predecessors have done some research on lithology, sedimentation and reservoir of this Formation, but the understanding of genesis and distribution of high argillaceous sandstone is not clear. In this paper, the genesis and vertical distribution of high argillaceous sandstone in Hanjiang Formation are analyzed by core, logging and analytical test data. Combined with high resolution seismic data, the density and seismic elastic parameters inversion method are used to clarify the plane distribution characteristics. The results show that high argillaceous sandstone is mainly distributed in deltaic front underwater distributary channel, interdistributary bay and distal bar. Sediment deposition rate of deltaic front underwater distributary channel is fast, low energy hydrodynamic can not be fully scoured sediment screening, resulting in high mud content. The hydrodynamic conditions of deltaic front interdistributary bay and distal bar are weak, and fine-grained and argillaceous sediments are deposited in large quantities, so the argillaceous content of sandstone is high.

How to cite: Liu, X.: Sedimentary Genesis and Distribution of High Argillaceous Sandstone, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-979, https://doi.org/10.5194/egusphere-egu23-979, 2023.

14:11–14:13
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PICO2.4
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EGU23-999
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SSP1.1
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Virtual presentation
Wei Zheng

The Zhujiang Formation in A oilfield of Yangjiang Sag, Pearl River Mouth Basin has superior reservoir-cap assemblage and good oil accumulation conditions. However, due to the frequent drilling of high-calcareous and low-permeability sandstone, and the unclear understanding of the formation of high-calcareous and low-permeability sandstone and the distribution of sand bodies, the oil and gas exploration progress is restricted. In this paper, the formation and vertical distribution of high calcareous and low permeability sandstone are studied by using core, logging and analysis data combined with the sedimentary background in this area, and seismic inversion of reservoir is carried out by using seismic data combined with permeability, so as to realize the plane distribution prediction of high calcareous and low permeability sandstone. The results show that the Zhujiang Formation in the study area is mainly characterized by underwater river-bay microfacies, which provides abundant carbonate provenance conditions for high calcium content of sand bodies. And the sand bodies in the underwater distributary channel microfacies are closely interlaced with the calcare-rich mudstone at the top-bottom interface, moreover the migration of carbonate from mudstone to sandstone and related chemical reactions occur at the junction, which further increases the calcium content of sand bodies. Combined with the study of permeability inversion model, it is considered that the high-calcareous and low-permeability sandstones are mainly distributed in the underwater distributary channel near the provenance in the northern part of the study area.

How to cite: Zheng, W.: Genesis and Distribution Prediction of High Calcareous and Low Permeability Sandstone, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-999, https://doi.org/10.5194/egusphere-egu23-999, 2023.

14:13–14:15
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PICO2.5
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EGU23-4211
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SSP1.1
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ECS
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Virtual presentation
Dawen Zhou

Fan delta is an important reservoir for hydrocarbon accumulation.The channel sand bodies of fan-delta front facies are narrow , and the lithologic assemblage changes quickly in space and is sensitive to water depth changes. It is a key and challenging task to accurately identify and characterize the channel with seismic data under the condition of few Wells. In this study, we selected the fan delta deposits of the Shahejie Formation in the Gangzhong area of the Bohai Bay Basin, China as an example to explore the method to accurately characterize the channel in the fan delta system by using seismic multi-attribute fusion technology.Six types of thirty-eight seismic attributes reflecting different geological information are extracted for river channel identification in the target area, and the most sensitive attributes to geological conditions are selected in each class of attributes. The physical meaning of various attributes is analyzed to identify the differences between different river structures. The multi-attribute clustering analysis based on FCM algorithm is used to reduce data dimension and reduce redundancy. Three seismic attributes that reflect the boundaries of geological bodies and lithological characteristics are selected for RGB fusion to highlight the overall characteristics of river distribution in this area, and enhance the characterization of the boundaries of channel sand body. It provides practical value for the next favorable target prediction of channel sand body.

How to cite: Zhou, D.: Application of Multi-attribute fusion Technology in Channel Sand Body Recognition and Boundary Characterization : A Case Study of the Gangzhong Oil Field in Bohai Bay Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4211, https://doi.org/10.5194/egusphere-egu23-4211, 2023.

Sedimentary and morphodynamics; Bedforms
14:15–14:17
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PICO2.6
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EGU23-12415
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SSP1.1
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On-site presentation
Mechanism of Sand-Mud Transition Dynamics at an Artificial Beach Based on Horizontal and Vertical Sedimentary Modeling
(withdrawn)
Huidi Liang, Xiao Zhu, Wei Chen, and Lianqiang Shi
14:17–14:19
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PICO2.7
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EGU23-9849
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SSP1.1
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On-site presentation
Natasha Dowey, Pete Rowley, Rebecca Williams, Nemi Walding, Greg Smith, Matthew Johnson, and Thomas Johnston

Pyroclastic density currents (PDCs) are density-driven flows of gas, ash and rock generated during explosive volcanic eruptions, or by the collapse of volcanic lava domes. They can reach temperatures of >500 °C and are highly mobile, with the ability to travel at speeds of >200 m/s and to scale obstacles hundreds of metres high. PDCs are a devastating volcanic hazard and have killed >90 000 people since 1600 AD1; understanding their behaviour is an important aspect of volcanic disaster risk reduction. Because of their extreme nature, PDCs are difficult to observe and quantify in real time. Volcanologists therefore use field studies and modelling techniques to investigate their dynamics.

As PDCs travel they progressively deposit ignimbrite, a poorly sorted volcanic rock typically rich in pumice and ash. Ignimbrites commonly display a variety of bedforms and stratigraphic architecture; such architecture can be interpreted to unpick the behaviour of the original PDC, and of the evolution of the eruption that created it. However, there is considerable uncertainty involved in ignimbrite bedform interpretation, due to the potential for complexity (such as cryptic bypass, erosion, and hybrid processes) and also due to fundamental gaps in our knowledge of the physical properties of PDCs.

Our work uses analogue modelling of gas-fluidised, dense, granular currents in a laboratory flume together with examples from the field to explore what the dynamics of experimental PDCs (and their resultant bedforms) can tell us about our interpretations of real-world volcanic stratigraphy. The examples presented examine a range of bedforms and processes, including the impact of fluidisation and grainsize on PDC mobility and bedform morphology, the influence of moisture on cohesivity and bedform preservation, and the implications of grading in volcanic stratigraphy. The significant challenges in quantifying the sedimentation of ignimbrites are discussed. This work seeks to improve field interpretations of volcanic bedforms and contribute to the development of volcano risk models.

 

1: Auker et al. (2013) J Appl. Volcanol. https://doi.org/10.1186/2191-5040-2-2

How to cite: Dowey, N., Rowley, P., Williams, R., Walding, N., Smith, G., Johnson, M., and Johnston, T.: From flume to field: using analogue modelling to delve into uncertainty in our interpretations of volcanic bedforms and what they tell us about deadly hazards, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9849, https://doi.org/10.5194/egusphere-egu23-9849, 2023.

14:19–14:21
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PICO2.8
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EGU23-889
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SSP1.1
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ECS
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Virtual presentation
Mohd Faisal Ansari and Zulfequar Ahmad

Flow near the confluence of two channels is complex and need investigation. The ratio of momentum of flow in the channels and confluent angle are important parameters affecting the flow structures and development of the mixing layers downstream of the confluence. Numerical modelling constitutes an essential tool for studying these complex flow phenomena. The main objective of this study is to investigate flow structure for different momentum in the channels. To achieve this, a Computational Fluid Dynamics model of the parallel open channel confluence was simulated with the help of ANSYS FLUENT and validated with an experimental study. 3D velocities were measured in the confluence region using Acoustic Doppler Velocimetry (ADV). These velocities were compared with the velocities obtained numerically and found to be in good agreement. Transverse development of the turbulent mixing layers in the post confluence region was affected by transverse distribution of the streamwise velocity.

How to cite: Ansari, M. F. and Ahmad, Z.: Experimental and Numerical Study at Parallel Open Channels Confluence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-889, https://doi.org/10.5194/egusphere-egu23-889, 2023.

14:21–14:23
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PICO2.9
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EGU23-7223
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SSP1.1
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ECS
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Highlight
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Virtual presentation
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Jimmy Daynac, Paul Bessin, Stéphane Pochat, and Régis Mourgues

The surface of some planet’s present abundant periodic topographic forms at different scales (mm- km) and in different environments. They are called bedforms and develop at the interface between a moving fluid and a deformable and/or erodible material. Sand dunes are major bedforms in aeolian systems and play an important role in understanding how aeolian environments evolve. Generally grouped in dune fields, their morphological characteristics (e.g. shape, size, patterns of spatial organization) play a critical role understanding how aeolian environments evolve and interact with global changes. Detailed maps of these morphologies are produced by GIS manual digitizing from high-resolution satellite imagery and digital terrain models but this approach remains time-consuming. One way to override these locks is to use Artificial Intelligence (AI) to increase the computational speed, accuracy and reproducibility of mapping.

We here present a GIS automated mapping protocol of aeolian bedforms contours and crestlines based on AI. First, we extract the Residual Relief in order to delete the regional topographic trend and map the different dune generations. Secondly, an unsupervised pixel-based classificator (Deep Learning, U-Net CNN) trained with Residual Relief samples of different dune forms is used to detect and map dunes independently of the bedrock. Thirdly, the dune crests are skeletonized from the identification of high inflection point of the dunes from a Volumetric Obscurance approach. The protocol is repeated for each dune order of magnitude to extract the different superimposed generations of dunes and their relationships.

To illustrate its performance, the protocol was applied on a part of the Rub’Al Khali (220,000 km²) and Namib deserts (115,000 km²) to map the various dune forms and a first morphometric analysis is realized at the scale of the two sand seas. We produced a detailed map of the aeolian morphologies for each desert at two orders of magnitude (kilometer-scale and hectometer-scale dunes). For the Rub’Al Khali desert, more than 78,000 dunes (58,000 km²) and crestlines were mapped in 6 hours of processing and more than 17,000 dunes (12,000 km²) and crestlines for the Namib desert in the same processing time. The first morphometric parameters calculated from the previous results show a spatial variability of the length, width, height and crests orientation for Rub’Al Khali and Namib dunes. Thus, the protocol contributes to provide a digital atlas of the different dune generations (kilometer-scale and hectometer-scale dunes). All of these results allow to visualize the morphological dunes diversity and contribute to understand the relationships between forms and processes at a dune field scale.

How to cite: Daynac, J., Bessin, P., Pochat, S., and Mourgues, R.: Automatically dunes mapping and morphometric analysis using Artificial Intelligence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7223, https://doi.org/10.5194/egusphere-egu23-7223, 2023.

14:23–14:25
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PICO2.10
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EGU23-11049
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SSP1.1
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Virtual presentation
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Ankur Roy, Tapan Mukerji, and Amitabha Chakrabarti

Ripple marks formed in different sub-environments of a tidal flat are considered helpful in distinguishing such sub-environments from one another owing to the predominance of specific agencies that generate and stabilize these ripples. For example, ripple stabilized in tidal channels are dominated by tidal currents and those in estuarine settings are both wave and current dominated. In order to evaluate the possibility of using ripple morphology in distinguishing between such sub-environments, data on ripple index (RI) from an estuary and tidal channels were analyzed. These data were collected from the east coast of India that provides examples of open-coast tidal flats at Chandipur and 50 km north-east at Digha. It was found that they have overlapping morphological patterns as delineated from RI vs. the percentage fraction for each case of estuarine and tidal channels. So, while RI can broadly define environments, e.g., aeolian and water borne ripples, when it comes to separating wave from current ripples, a fair overlap is seen in tidal flat regions. On the other hand, grain-size study alone is insufficient for the purpose of delineating differences between such sub-environments. This is because it is seen in our analyses that while most estuarine sediments are finer than 3 on the Φ-scale and tidal channel sediments are coarser, much better sorted as well as mostly positively skewed, these values overlap such that a clear distinction cannot be achieved. Therefore, in order to distinguish between such sub-environments, we took into account both grain-size parameters associated with ripple marks and the corresponding RI values. A relative “distance” was calculated between pairs of samples based on RI, mean, sorting, skewness and kurtosis. In other words, this “distance” is a way to determine how similar two samples are in terms of their respective RI and grain-size parameters. A dissimilarity matrix was constructed which, in turn, was translated into a configuration of points in the Euclidean Space via Multidimensional Scaling (MDS). Four different “types” of measure of this “distance” were considered: Euclidean, Standard Euclidean, City Block and Minkowski (P=3). It was observed that the MDS plot based on City Block distance generated two distinct clusters of points for samples collected from estuary and tidal channels. A way forward is to employ Random Forest Analysis and test whether RI in conjunction with grain-size parameters may be used for classifying modern sediments or even rock samples representing paleo-environments as belonging to either estuarine or tidal channel setting.

How to cite: Roy, A., Mukerji, T., and Chakrabarti, A.: Identifying Sub-environments in a Tidal Flat: An MDS Approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11049, https://doi.org/10.5194/egusphere-egu23-11049, 2023.

Palaeontology, Palaeoecology and Evolution of Life
14:25–14:27
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PICO2.11
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EGU23-6116
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SSP1.1
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ECS
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On-site presentation
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Christian Geier, Johannes M. Bouchal, Silvia Ulrich, Torsten Wappler, and Friðgeir Grímsson

The Onagraceae or evening-primrose family has a fossil record composed mainly of dispersed pollen that has been discovered in Late Cretaceous to Holocene sediments around the globe. The pollen record suggests the family reached a cosmopolitan distribution during the Eocene. Currently, there is no reliable Onagraceae leaf record, and the meagre mesofossil record is composed of only a few fruits/seeds of Circaea and Ludwigia from the Oligocene to Pliocene of Eurasia. There is also a unique fossil Fuchsia flower that was described from the early Miocene of New Zealand, but other than that, there are no fossil Onagraceae flowers known to date. In addition, Onagraceae pollen has never been found adhering to fossil insects, and as such, there is no direct evidence of which insects visited Onagraceae flowers prior to modern times. Here we present an exceptional finding, an Onagraceae flower bud of Eocene age, from Eckfeld in Germany. Due to the flower’s bud stage the stamens were still packed with pollen. Nevertheless, the in situ pollen enabled us to assign the flower to the genus Ludwigia, based on a combination of unique morphological and ultrastructural traits observed with combined LM, SEM, and TEM, making it one of the earliest records of this genus. More importantly, we also discovered the same Ludwigia-type pollen adhering to the exterior of two different fossil beetles, a Buprestidae and Scarabaeidae, from the same locality. These provide the first-ever direct evidence for paleo-flower-insect visitation in Ludwigia and Onagraceae. Interestingly, we did not discover any Ludwigia-type pollen on the several Hymenoptera fossils investigated during this study, but Hymenoptera are the main flower visitors and pollinators of Ludwigia at present. These findings might suggest that beetles were the main flower visitors and potential pollinators of European Ludwigia during the Eocene and that there has been a shift in primary pollinators through the geological record.

How to cite: Geier, C., Bouchal, J. M., Ulrich, S., Wappler, T., and Grímsson, F.: Fossil Onagraceae flower and insects with in situ or adhered pollen from the Eocene of Eckfeld, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6116, https://doi.org/10.5194/egusphere-egu23-6116, 2023.

14:27–14:29
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PICO2.12
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EGU23-6499
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SSP1.1
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ECS
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On-site presentation
Johannes M. Bouchal, Christian Geier, Silvia Ulrich, Volker Wilde, Olaf K. Lenz, Reinhard Zetter, and Friðgeir Grímsson

The early to middle Eocene maar lake of Messel is a world-renowned fossil locality. Its oil shale deposits are well-known for their exceptional preservation of vertebrates (e.g., crocodiles, early horses) and invertebrates, especially insects. The makro- and microfossil remains of plants also contributed to providing a more holistic snapshot of this Eocene ecosystem. So far, the palynoflora has mostly been investigated using only conventional LM, and the classic taxonomic qualitative/illustrative work on the palynoflora dates back to the late 1980ies. Here we report on the first results from an ongoing study using combined LM and SEM, and in some cases even TEM, to re-investigate the Messel palynoflora qualitatively. The main goals of our study are to conclude (I) if some of the spores/pollen can be systematically placed with more certainty, (II) if additional spore/pollen types can be discovered, (III) to compare our combined method of investigation with the classic LM-based counting method, and finally (IV) to conclude about the composition and species richness of the palynoflora and how it correlates with the macro- and mesofloras. To accomplish this, we first processed a single sedimentary rock sample without fine-mesh sieving and then extracted and investigated every pollen type encountered using the single-grain method. So far, this sample has produced 30 spore types, 5 gymnosperm pollen types, and about 185 different angiosperm pollen types. The previous LM-based qualitative work identified 173 palynomorphs in an accumulative account from numerous rock samples up-trough the oil shale section. Our study, on a single sample from the lowest part of the oil shale revealed every single pollen type (except for Milfordia (Restionaceae) and Pityosporites microalatus (Cathaya, Pinaceae)) discovered in the accumulative approach using the classic LM counting method. Also, in addition to the c. 140 angiosperm pollen types previously recorded, we can now add at least 45 new pollen types for this locality. Our study shows that when taxonomic resolution and diversity are key, a combined LM and SEM investigation produces higher diversity than relying only on the conventional LM counting method when single samples are compared. In addition, a well-preserved single sample extensively studied using the combined approach is likely to provide the same or even higher number of taxa when compared to conventional LM counting methods analyzing an entire stratigraphic section. The qualitative combined approach will provide a more reliable presence/absence of taxa in the accumulation site hinterland. For quantitative analysis and subtle changes in the surrounding environments conventional counting methods are more appropriate because of the universal availability of light microscopes and difficulties with SEM-counting.

How to cite: Bouchal, J. M., Geier, C., Ulrich, S., Wilde, V., Lenz, O. K., Zetter, R., and Grímsson, F.: Revisiting the Messel palynoflora using a combined LM and SEM approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6499, https://doi.org/10.5194/egusphere-egu23-6499, 2023.

14:29–14:31
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PICO2.13
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EGU23-6860
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SSP1.1
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ECS
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On-site presentation
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Julia Hoffmann, Bonnie F. Jacobs, Ellen D. Currano, Aaron D. Pan, and Friðgeir Grímsson

The early Miocene Mush flora has the potential to provide exceptional insight into the paleoecology and floral biogeography of East Africa, which is otherwise deprived of fossil plant assemblages from that time. However, at present only three genera within two families, Englerodendron (Fabaceae: Detarioideae), Newtonia (Fabaceae: Mimoseae), and Tacca (Dioscoreaceae), have been described from the plant macrofossil record. The remaining c. 50 leaf morphotypes have been classified on the basis of their morphological features and require additional cuticle analyses and comparative study. Previous work on the palynoflora was based on light microscopy (LM) only and comprised 32 palynomorphs, representing 24 families – ferns (single family) and angiosperms. To assist in the identification of the macrofossils and to establish a more complete picture of the paleovegetation, we are investigating pollen and spores from three (out of six) of the same stratigraphic levels from which leaf macrofossil censuses have been conducted. The primary results from this combined LM and SEM study follows. The palynoflora is composed entirely of fern spores and angiosperm pollen with a notable absence of gymnosperm pollen. So far we have discovered 15 different types of fern spores, and an amazing number of different angiosperm pollen types. Interestingly, monocots are not diverse, and so far we have only identified two types, pollen of Sclerosperma (Arecaceae) and that of Pontederiaceae. The former a typical swamp element in tropical Central West Africa and the latter aquatic plants with a pan-(sub)tropical distribution. The dicot component is the most diverse with 85 different pollen types discovered so far. The highest diversity occurs in the Fabaceae (8 spp.) and the Sapotaceae (7 spp.). Other families, represented by a number of taxa, include Apocynaceae, Araliaceae, Euphorbiaceae, Malvaceae sensu lato, Moraceae, and Vitaceae. This rich angiosperm palynoflora reflects a diverse and complex forest vegetation surrounding the ancient lake. The forest was composed of various trees, shrubs, and woody climbers, thriving under a hot and humid climate. The high terrestrial diversity together with striking wetland and aquatic components hint at vegetation under tropical rainforest-like conditions. Future work will complete the SEM study from the censused levels and provide a reliable illustrated taxonomic list that will be used for pollen/spores counts within the Mush section. This will provide a final quantitative analysis based on the qualitative SEM work now in progress.

How to cite: Hoffmann, J., Jacobs, B. F., Currano, E. D., Pan, A. D., and Grímsson, F.: High taxonomic resolution SEM study of pollen and spores from the 21.73 Ma Mush flora, Ethiopia, Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6860, https://doi.org/10.5194/egusphere-egu23-6860, 2023.

14:31–14:33
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PICO2.14
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EGU23-14198
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SSP1.1
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Highlight
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On-site presentation
Sissa Stefanowicz, Marianne Ask, Cyril Julian, and Sofie Lindström

Palynology is widely used in both academic and industrial research for correlation and interpretation of subsurface geology on both local and regional scales. While most data gathering tools for the subsurface have undergone major technological developments during the last decades, palynological research has, apart from the use of more advanced microscopes, remained virtually unchanged and can be quite time consuming when large data sets are required. With increasing demand for faster, more high resolution and more detailed palynological analyses from the continuously developing technological industry as well as the academic science community, palynology is at risk of being left behind.

The answer could lie in adopting strategies of digitalisation and Artificial Intelligence (AI) originally developed for medical research. The technology of scanning microscope slides into a digital high-resolution image has already been developed, and AI software specifically developed for palynology can be utilised to examine the digital images and detect, identify and quantify the fossil content.

In this project we have designed and developed an AI software for clustering and classification of microfossils based on deep-learning based algorithms for detection of palynomorphs and algorithms based on autoencoders for extracting features predictive of different fossil types. The AI is trained to recognize and identify fossils from different angles, preservation levels and fragmentation stages, as well as partially obscured or folded specimens. The AI can then analyse specimens for morphological parameters such as texture, shape and/or RGB/HSV values and use these parameters to categorize the specimen into clusters. The clustering has many applications, e.g., identifying morphological variations within taxa and recognizing variations in colour and preservation related to reworking or caving during the drilling process. The project also explores the advantages and disadvantages of working with digitally scanned palynological slides and the use of AI software recognition. The project will establish if the digital scans of the palynological samples have the resolution needed to be used for quantitative analyses and develop a preparation process to reliably produce the best digital samples possible.

How to cite: Stefanowicz, S., Ask, M., Julian, C., and Lindström, S.: Detection, identification and clustering of palynomorphs using AI and machine learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14198, https://doi.org/10.5194/egusphere-egu23-14198, 2023.

14:33–14:35
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PICO2.15
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EGU23-16147
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SSP1.1
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On-site presentation
Compositional fidelity of phyla and classes in marine benthic associations
(withdrawn)
Michal Kowalewski, Carrie Tyler, and Michał Kowalewski
14:35–15:45
Coffee break
Chairpersons: Alicia Fantasia, Madeleine Vickers, Guilhem Amin Douillet
General topics
16:15–16:17
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PICO2.1
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EGU23-15674
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SSP1.1
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On-site presentation
Differentiation of saffron geographic origin by stable isotope (C, H, O, N) and 87Sr/86Sr analysis
(withdrawn)
Micha Horacek
16:17–16:19
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PICO2.2
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EGU23-4121
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SSP1.1
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Highlight
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On-site presentation
Stephen Lokier and Sarah Giles

The development, dissemination, and communication of research findings is a critical element of the journey to completing a graduate degree.

Traditionally, in-person presentations of research at conferences, meetings, and workshops – in the form of posters, oral presentations and, interactive displays (such as PICOS), provides early career scientists with an invaluable opportunity to promote their research, ‘road-test’ hypotheses and solicit feedback in a friendly collegial atmosphere. Meeting attendance exposes early career researchers to the latest research advances, affording an opportunity to network and build collaborations with other researchers. Presentations allow students to develop their proficiency in oral and written communication – critical skills for post graduate employment.

The above may seem obvious yet, for many of us, the significance, importance, and necessity of these ‘traditional’ modes of communication were, perhaps, vastly underappreciated until they were precipitously withdrawn with the global lockdown during the COVID-19 pandemic. For many, the loss of easy access to meetings led to the realization that countless researchers have, in fact, never had the luxury of this interaction – all be it for reasons of geographical, cultural, political, health, mobility or financial isolation from the global scientific community.

The necessity to maintain communications during the pandemic resulted in an explosion in the development of on-line meetings. Among the leaders in this field was Seds Online, an initiative developed in March 2020 aiming to aid, promote, maintain and enhance communication within the global sedimentology community. At inception, Seds Online offered a series of global daily meetings (Coffee Breaks) and weekly Webinars. As the initiative developed, further formats were tried, including Sedimentology Debates and Student Webinars.

Seds Online Student Webinars provide a venue for students, regardless of location, to present their sedimentology-focused research, to the global geoscience community. A theme is selected for each webinar, and submissions are invited from the global sedimentology student community. Applicants provide a brief description of the project purpose, methods, and results, and how these relate to the webinar theme. This approach requires students to synthesize their research, communicate it succinctly, and determine its applicability in a broader geoscience context. To ensure equability, applications are anonymised, before being reviewed and ranked by a committee.

Invited presenters are provided with advice on presentation design followed by post presentation feedback. The format is similar to a ‘normal’ in-person meeting, each presentation is followed by a few questions with an additional 15 minutes at the end of the meeting for open discussion on the topic in hand. The webinar is recorded and uploaded to SedsOnline.com for wider audience viewing. The continued availability of the recorded presentation allows the presentation to be viewed beyond the time constraints of the ‘live’ event, and also serves as an artifact for students to share on their personal webpage, or link to their CV, job applications or grant proposals.

The Seds Online Student Webinar presentation format is low-risk and high-reward for students, enabling presentation of research and building confidence – we hope this format serves as inspiration for student webinars in other realms of geoscience.

How to cite: Lokier, S. and Giles, S.: Seds Online Student Webinars – Creating impactful opportunities for students to share their geoscience research, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4121, https://doi.org/10.5194/egusphere-egu23-4121, 2023.

16:19–16:21
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PICO2.3
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EGU23-10273
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SSP1.1
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ECS
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Virtual presentation
Coastal and marine geoarchaeology – the opportunities of recognising its adolescence
(withdrawn)
Ingrid Ward, Piers Larcombe, Stephen Lokier, Moyra Wilson, and Juliet Sefton
Stratigraphy, Earth Systems History and Climate Geology
16:21–16:23
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PICO2.4
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EGU23-2891
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SSP1.1
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ECS
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On-site presentation
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Luis Collantes, Sofia Pereira, Eladio Liñán, Eduardo Mayoral, and Rodolfo Gozalo

The Cambrian Series 2 is challenging for biostratigraphy and correlation. In current Europe (mostly West Gondwana), this Series sequences are hard to identify due to the scarcity of its fossil record. An exception is the Ossa-Morena Zone (OMZ), southwestern Iberia, where lower Cambrian fossils are fairly abundant. The OMZ belongs to the southern branch of the Variscan Orogen of the Iberian Peninsula, comprising rocks dating from the latest Proterozoic to the Carboniferous. Its Cambrian sequences are preserved in distinct ‘blocks’, showing a significant change of facies and thicknesses, most likely related to downthrow and tilting along an active growth fault during sedimentation.  Four regional stages were proposed for the Cambrian Series 2: Ovetian, Marianian, Bilbilian and Leonian (lower part). Among these, the Marianian Stage has suffered significant conceptual modifications since its original erection. At the moment, its correlation through the Iberian Peninsula is still a subject of debate.

The OMZ record of trilobite fossils and, therefore, their biostratigraphy, has been hindered due to the limited continuity of trilobite facies in many sections, the poor preservation of the specimens, and tectonic distortion. Based on work carried out in recent years, we present the updated trilobite distribution and contribution for the biostratigraphical subdivision of the Marianian Stage in the OMZ, to improve and refine intra- and inter-regional correlation. The base of the Marianian Stage is characterized by the FAD of Strenuella; being the lower Marianian substage characterized by the co-occurrence of Delgadella souzai, Mimacca? and Saukianda andalusiae. The boundary with the middle Marianian is defined by the FAD of Strenuaeva sampelayoi, and this substage is characterized by D. souzai, S. andalusiae, Alanisia guillermoi, Perrector perrectus, Eops eo, Gigantopygus cf. bondoni, Andalusiana cornuta, Triangulaspis fusca, Callavia choffatiRinconia schneideri, Calodiscus ibericus, Atops calanus, Hicksia elvensis and Termierella sevillana. Finally, the base and top of the upper Marianian are marked, respectively, by the FAD and LAD of Serrodiscus bellimarginatus, being this substage characterized by the presence of T. fusca, Chelediscus garzoni, Protaldonaia morenica, and Pseudatops reticulatus. The new biostratigraphical data strengthens the correlation with Cambrian Series 2 sequences along the western Gondwana margin (e.g. Banian Stage from Morocco and the Charlottenhof Fm from Germany), western and eastern Avalonia (upper Callavia and lower Strenuella sabulosa Biozones), Baltica (lowermost Holmia kjerulfi to lowermost Ellipsostrenua spinosa Biozones) and Siberia (Botoman and lowermost Toyonian Stages). In addition, biostratigraphical correlation with the Dyeran Stage of Laurentia, Elliptocephala asaphoides Biozone from the Taconic Allochthon and Pararaia janeae Biozone from Australia have been improved.

How to cite: Collantes, L., Pereira, S., Liñán, E., Mayoral, E., and Gozalo, R.: The regional Marianian Stage (Cambrian Series 2) of the Ossa-Morena Zone, SW Iberia: trilobite biostratigraphy and international correlation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2891, https://doi.org/10.5194/egusphere-egu23-2891, 2023.

16:23–16:25
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PICO2.5
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EGU23-5495
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SSP1.1
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On-site presentation
Tadeusz Peryt, Izabela Ploch, Paweł Raczyński, Sebastian Voigt, Hubert Kiersnowski, and Wojciech Pawlak

The geology of the Intrasudetic Basin (Poland and Czech Republic) in the past was studied separately in both countries. Our project combined data from both parts of the basin to study the development of the limnic basin during the seasonally extreme climate in the Early Permian. The Lower Rotliegend Słupiec Formation (Broumov Formation in the Czech part) red bed deposits appear the most promising for palaeoenvironmental and palaeoclimatic studies. Fine-grained weathering products  (black shales), tuff admixtures and autochthonous components (limestones) in lakes contain many remains of plants, and traces of activity of invertebrates and vertebrates including extraordinarily numerous traces fossils of tetrapods (reptiles and amphibians) (e.g., Voigt et al. 2012) and fish remains (e.g., Stamberg & Zajíc, 2008). The Słupiec Formation is interpreted as a successively finning-upwards megacyclothem consisting, from base to top, of alluvial fan, fluvial and lacustrine deposits (Wojewoda and Mastalerz, 1989; Kurowski, 2004). However, the cyclicity is also clearly marked by successive transitions from lacustrine sediments with preserved fish remains to terrestrial sediments with numerous tracks of terrestrial reptiles and amphibians. This seasonal climate with dominant monsoonal rainy summer and winter seasons with low precipitation is clearly recorded in deposits of alluvial-fluvial plains and lakes. Extreme weather conditions, such as possible night frosts, were also recorded in the sediments, although the basin was located relatively close to the equator.

This research was funded by the Polish National Science Centre (Grant 017/26/M/ST10/00646).

Kurowski, L. (2004); Geologia Sudetica, 36: 21–38; Štamberg, S. & Zajíc, J. (2008): Carboniferous and Permian faunas and their occurrence in the limnic basins of the Czech Republic. Museum of Eastern Bohemia; Voigt, S., Niedźwiedzki, G., Raczyński, P., Mastalerz, K. & Ptaszyński, P. (2012): Palaeogeography, Palaeoclimatology, Palaeoecology, 313-314: 173-180; Wojewoda, J. & Mastalerz, K. (1989): Przegląd Geologiczny, 37: 173–180.

How to cite: Peryt, T., Ploch, I., Raczyński, P., Voigt, S., Kiersnowski, H., and Pawlak, W.: Lower Permian sediments of the Intrasudetic Basin: a record of cyclic, climatically-controlled transitions from lacustrine to terrestrial conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5495, https://doi.org/10.5194/egusphere-egu23-5495, 2023.

16:25–16:27
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PICO2.6
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EGU23-5168
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SSP1.1
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On-site presentation
Izabela Ploch, Marek Awdankiewicz, Wojciech Pawlak, Tadeusz Peryt, Paweł Raczyński, Sebastian Voigt, and Magdalena Pańczyk

The Intrasudetic Basin represents one of the larger late- to post-Variscan intramontane troughs of Central Europe. It is situated at the northern margin of the Bohemian Massif. The Basin represents a fault-bounded synclinorial structure and was formed in the late Visean as a depression framed by tectonically active margins. During the Permian, the basin was filled with dominantly fine-grained alluvial to lacustrine deposits, accompanied by volcanic rocks. Volcanic activity evolved with time and comprised emplacement of subvolcanic intrusions, effusion of lava flows as well as deposition of widespread ignimbrites (Awdankiewicz, 1999). These volcano-sedimentary units are known as the Słupiec Formation in the Polish part and the Broumov Formation in the Czech part of the Intrasudetic Basin, respectively. So far, based on generally imprecise biostratigraphic evidence and regional correlations, the Słupiec Formation sedimentary rocks together with the intercalated volcanic rocks were (usually) assigned to the Sakmarian. However, preliminary results of U-Pb SHRIMP zircon dating of the Góry Suche Rhyolitic Tuffs and the Łomnica Rhyolites – a widespread ignimbrite sheet and associated rhyolitic laccoliths intercalated in the Słupiec/Broumov Formation - suggest that these volcanic rocks can be older than supposed by 5-10 My. Such age estimate would assign these ignimbrites and rhyolites to the Asselian, not Sakmarian.

In this contribution the biostratigraphic evidence on the position of the Słupiec/Broumov Formation is re-assessed. The fluvio-lacustrine sedimentary members of these formations accumulated probably in semi-arid palaeoclimatic conditions with seasonally-controlled watertable.Numerous footprints of reptiles and amphibians, aquatic vertebrates: chondrichthyans, actinopterygians and amphibians, also palaeobotanical remains were preserved (e. g.  Jerzykiewicz, 1987; Zajíc, 2000; Stamberg & Zajíc, 2008; Voigt et al., 2012; Opluštil et al., 2016). Unfortunately, they appear only fairly suitable for detailed biostratigraphy as their successions may be environmentally-controlled, and most of them indicate a latest Carboniferous to early Permian age. At this level of knowledge, they are not suitable for detailed biostratigraphy, and thus comprehensive and comparative studies of the Late Carboniferous and Early Permian Central European volcanic-sedimentary basins are necessary to better constrain the stratigraphic position of the Słupiec/Broumov Formation of the Intrasudetic Basin.

This research is funded by the Polish National Science Centre (Grant 017/26/M/ST10/00646).

Awdankiewicz, M. (1999): Geologia Sudetica, 32 (1): 13-47; Jerzykiewicz, J. (1987): Palynology 11: 117-131; Opluštil, S., Schmitz, M., Kachlík, V. & Štamberg, S. (2016): Bulletin of Geosciences, 91: 399–432; Štamberg, S. & Zajíc, J. (2008): Carboniferous and Permian faunas and their occurrence in the limnic basins of the Czech Republic. Museum of Eastern Bohemia; Voigt, S., Niedźwiedzki, G., Raczyński, P., Mastalerz, K. & Ptaszyński, P. (2012): Palaeoclimatology, Palaeoecology, 313-314: 173-180; Zajíc, J. (2000): Courier-Forschungsinstitut Senckenberg, 223: 563-575.

 

How to cite: Ploch, I., Awdankiewicz, M., Pawlak, W., Peryt, T., Raczyński, P., Voigt, S., and Pańczyk, M.: Problematic age and stratigraphic position of the volcano-sedimentary Słupiec/Broumov formation in the Permian of the Intrasudetic Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5168, https://doi.org/10.5194/egusphere-egu23-5168, 2023.

16:27–16:29
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PICO2.7
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EGU23-4059
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SSP1.1
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ECS
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On-site presentation
Septriandi Chan, Michael Kaminski, and John Humphrey

There is relatively little information on the taxonomy of foraminifera found in Saudi Arabia's Cenozoic formations compared with those from the Mesozoic formations. Four outcrops in the Al Lidam area, eastern province of Saudi Arabia have been studied to document the Miocene foraminiferal assemblages. Acetic acid was used to extract foraminifera from lithified carbonate rocks from 80 samples representing seven lithofacies. Results of disaggregation using acetic acid are promising. In total, 46 species of benthic foraminifera have been identified. The foraminifera are dominated by calcareous porcelaneous Miliolina (Coscinospira, Sigmoilinita, Peneroplis, Quinqueloculina, Triloculina), followed by hyaline genera (Ammonia, Cibicides, Discorbinella, Elphidium), a few agglutinated forms (Textularina), but planktonic foraminifera are absent. Borelis melo melo indicates that the studied formation is dated to Burdigalian to Langhian age. Based on the identified species, the studied formation is interpreted as having been deposited in an arid subtropical environment in hypersaline waters that were present on a restricted and very shallow carbonate platform (inner ramp). The foraminiferal faunas of the present-day Arabian Gulf show similarity with the Miocene faunas. Thus, the present-day Arabian Gulf provides a highly suitable modern analog for earlier Cenozoic conditions in the region.

How to cite: Chan, S., Kaminski, M., and Humphrey, J.: Micropaleontological study of the Miocene Dam Formation, Eastern Province of Saudi Arabia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4059, https://doi.org/10.5194/egusphere-egu23-4059, 2023.

16:29–16:31
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PICO2.8
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EGU23-4531
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SSP1.1
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On-site presentation
Danuta Peryt, Przemysław Gedl, Elżbieta Worobiec, Grzegorz Worobiec, and Tadeusz Peryt

The Badenian/Sarmatian boundary in the Central Paratethys has been traditionally identified by the faunal turnover recording an important environmental change possibly controlled by the change from marine to brackish conditions. The strata below the Badenian/Sarmatian boundary in the northern Carpathian Foredeep in Poland are included into the Pecten beds, and those above it into the Syndesmya beds. Foraminiferal study of the Babczyn 2 borehole which is one of the crucial sections in the northern Carpathian Foredeep, well-known for the depositional age of rhyolite tuff within the Pecten beds dated by Śliwiński et al. (2012) at 13.06 ±0.11 Ma, indicated that in fact the boundary occurs within the Syndesmya beds. This conclusion is based upon the rapid change from a stenohaline foraminiferal fauna to a euryhaline one.

Benthic foraminifera and palynofacies from the Upper Badenian  Neobulimina longa, Hanzawaia crassiseptata and lower Sarmatian Elphidium angulatum and Anomalinoides dividens zones have been studied (Peryt et al., 2021).  Benthic assemblages are moderately to highly diversified. The benthic foraminiferal successions in the studied interval suggest normal marine salinity, middle shelf depth basin, with relatively small oxygenation and productivity changes during the late Badenian. The rapid change in the taxonomic composition between the H. crassiseptata and E. angulatum zones reflected by extinction/disappearance of stenohaline taxa from the foraminiferal assemblages and replace them by euryhaline forms resulted from shallowing and decrease in salinity of the Polish Carpathian Foredeep Basin.

Palynofacies is dominated by terrestrial elements represented by palynodebris (black and dark brown phytoclasts and cuticles) and pollen grains. The proportion of marine elements (dinoflagellate cysts, prasinophytes, acritarchs, and rare zooclasts) rarely exceeds 10%. Taxonomic diversity of the dinoflagellate cyst assemblages is low. Majority of samples yielded assemblages dominated by 3–4 species with remaining taxa represented by rare or even single specimens. Qualitative and quantitative analysis of aquatic palynomorphs show that the borehole interval studied accumulated during variable, unstable sedimentary conditions. A short interval that occurs just above the last occurrence of stenohaline foraminifers is characterized by lack of dinoflagellate cysts and flowering of Leiosphaeridiaceae. Lack of dinoflagellate cysts points to conditions disastrous for dinoflagellate cysts. But the most likely reason was salinity increase above the level tolerable even for hypersaline forms (e.g., Polysphaeridium) but still favourable for Leiosphaeridia. These possibly hypersaline conditions were associated with stagnant, possibly stratified waters that led to anoxic conditions in the bottom waters manifested by amorphous organic matter. A cease of these conditions was caused by a possible sea level rise and a gradual return of a less saline water regime. The latter interpretation can be supported by high frequency of Polysphaeridium (a genus known from hypersaline environments).

The study was financed by the National Science Centre, Poland, grant No. UMO-2017/27/B/ST10/01129.

Peryt, D., Garecka, M., Peryt, T.M., 2021: Geological Quarterly, 65: 18, doi: 10.7306/gq.1584; Śliwiński, M., Bąbel, M., Nejbert, K., Olszewska-Nejbert, D., Gąsiewicz, A., Schreiber, B.C., Be-Nowitz, J.A., Layer P., 2012: Palaeogeography Palaeoclimatology Palaeoecology, 326–328: 12–29.

How to cite: Peryt, D., Gedl, P., Worobiec, E., Worobiec, G., and Peryt, T.: Palaeoenvironmental changes during the late Badenian - earliest Sarmatian (Middle Miocene) in Central Paratethys inferred from foraminiferal and palynological data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4531, https://doi.org/10.5194/egusphere-egu23-4531, 2023.

16:31–16:33
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PICO2.9
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EGU23-13111
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SSP1.1
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ECS
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On-site presentation
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Alexandra Siebels, Johan Ten Veen, Dirk Munsterman, Jef Deckers, Cornelis Kasse, and Ronald Van Balen

The Miocene sequence in the Roer Valley Rift System consists of alternating shallow marine, coastal and fluvio-deltaic deposits. In this study seismostratigraphy and biostratigraphy are used to determine major unconformities and sediment dispersal patterns. This research is important for future studies related to the geothermal energy potential, and for the improvement of cross-border correlations with the German and Belgian stratigraphic framework. Results show that a depocenter developed in the south-eastern part of the Roer Valley Graben above the Early Miocene Unconformity (EMU) during the Early- and Middle Miocene. Clinoforms are present in a limited area here, but show sediment dispersal from the south-east towards the north-west during periods of progradation. From the late Middle Miocene onwards, larger displacement rates occurred along the major bounding fault zones, i.e. the Peel Boundary Fault Zone, the Feldbiss Fault Zone and the Veldhoven Fault. As a result, the depocenter narrowed and shifted to the central part of the Roer Valley Graben, where accumulation rates increased and larger-scale clinoforms start prograding both towards the west-north-west. This phase coincides with the development of a regional hiatus on the structural highs and forced regression in the south-eastern Roer Valley Graben, caused by a major sea-level fall related to the Middle Miocene Climatic Transition. The effects of tectonics, eustacy and climate resulted in the formation of the Mid-Miocene Unconformity (MMU), which represents a series of events related both to tectonics and sea-level fluctuations, and is therefore expressed differently throughout the Roer Valley Rift System. Sedimentation continued through this period in the deeper parts of the Roer Valley Graben and on the Venlo Block, while an erosional hiatus is evident on the Campine Block and Peel Block. During the latest Miocene, the depocenter migrated to the south-western rim of the Roer Valley Graben, where the youngest Miocene sediments are deposited during a latest Tortonian-Messinian sea level fall that led to the formation of the Late Miocene Unconformity (LMU).

How to cite: Siebels, A., Ten Veen, J., Munsterman, D., Deckers, J., Kasse, C., and Van Balen, R.: Miocene Depocenters and  Sediment Supply in the Roer Valley Rift System: Impacts of Tectonics, Eustacy and Climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13111, https://doi.org/10.5194/egusphere-egu23-13111, 2023.

16:33–16:35
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PICO2.10
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EGU23-11157
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SSP1.1
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ECS
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On-site presentation
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Yu Ting Yan, Adam D. Switzer, Christophe Fontainer, Stephen J. Culver, Stephen Chua, Kyle Morgan, Yama Dixit, and Benjamin P. Horton

In the context of warming climate and rising sea level, records from the early-to-mid Holocene provide important analogues to investigate how the environment responds to such changes. The Sunda shelf provides favourable conditions to reconstruct past environmental change as the presence of numerous large paleo-valley systems and high sedimentation rates allow transgressive deposits from the early-mid Holocene sea-level rise to accumulate continuously in topographic depressions.  To this end, we analysed the sedimentological, geochemical and micropaleontological characteristics of a sediment core (GRBH03) to investigate early-to-mid Holocene environmental changes in southern Singapore. We constrained the chronology with ten radiocarbon dates that were placed in Bchron age-depth model. Using a multi-proxy approach (e.g., grain size distribution, loss on ignition and XRF core-scanning), supported by benthic foraminifera, three sedimentary units were identified in GRBH03. Sedimentary unit I was found at the base of the core. This unit was characterised by a dark grey sandy silt unit deposited from about 9.0 to 8.9 cal ka BP. Few or no foraminifera were found in this unit, likely due to degradation of organic material. Sedimentary unit II was a blue-grey marine mud that was deposited between 8.8 and 5.8 cal ka BP. Within the marine mud unit, foraminiferal assemblages show a transition to shallow marine environment from about 8.8 to 6.4 cal ka BP as open marine species (e.g., Murrayinella murrayi and Bulimina sp. cf. B. marginata) become more abundant up-core. Subsequently, brackish species such as Muyrrayinella globosa and Ammonia veneta started to dominate mud unit assemblages, reflecting a transition from shallow marine to brackish environments, likely associated with decelerating sea level rise. The marine unit is then overlain by the sedimentary unit III, which is a shelly-silt unit deposited after 5.9 cal ka BP. This unit was mostly barren of foraminifera, which may be attributed to a high-energy marginal marine environment where conditions were unfavourable for foraminiferal preservation. Our study show that changes in sedimentary units and foraminiferal assemblages present in GRBH03 are linked to varying rate of relative sea-level rise during the early-to-mid Holocene. 

How to cite: Yan, Y. T., Switzer, A. D., Fontainer, C., Culver, S. J., Chua, S., Morgan, K., Dixit, Y., and Horton, B. P.: A sedimentary and foraminiferal record of early to mid-Holocene environmental change from Singapore, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11157, https://doi.org/10.5194/egusphere-egu23-11157, 2023.

16:35–16:37
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PICO2.11
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EGU23-5008
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SSP1.1
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Virtual presentation
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Aleksander Kowalski

Ephemeral fluvial systems dominated by seasonal discharge fluctuations and episodic events of rapid flood flows are typical for arid to semi-arid climatic conditions. Dryland fluvial systems have been described from many ancient and modern, predominantly tectonically-controlled sedimentary basins across the globe. The author shows the results of detailed sedimentological analysis and palaeoenvironmental interpretation of the Early Permian (Rotliegend) Krajanów Formation exposed within a continental, fault-bounded Intra-Sudetic Basin (ISB), NE Bohemian Massif. This basin started its development in the middle Viséan (Turnau et al., 2002), as an narrow, intramontane trough and underwent complex evolution from Early Carboniferous to Late Cretaceous. The maximum stratigraphic thickness of the basin infill reaches about 11 000 metres (Nemec et al., 1982). During the Early Permian the ISB constituted a semi-enclosed, south-western outlier of the Polish Rotliegend Basin (Southern Permian Basin of Central Europe). The Permian sedimentary-volanogenic succession of the ISB exhibits distinct, large-scale cyclic structure and comprises successive, fining-upwards continental megacyclothems (megasequences) up to 600 metres thick (Awdankiewicz et al., 2003). Such megacyclic structure is thought to have originated from tectonic activity and is attributed to relatively rapid, fault-controlled subsidence of the basin floor (Nemec et al., 1982; Wojewoda and Mastalerz, 1989).

The Krajanów Formation is composed of fluvial, playa-like and lacustrine deposits which form one of such fining-upwards cyclothems and attain up to 300 m in thickness. Sediments of the lowermost part of the Formation are represented by coarse-grained fluvial red-bed assemblage. Early investigations described these sediments as fluvial in origin. The upper part of the Formation distinguished as the Upper Anthracosia Shale, is characterized by the mudstone-dominated siliciclastics interbedded with fine-grained calcareous deposits which acummulated in a floodplain-to-ephemeral („terminal”) lacustrine setting.

High-resolution sedimentological logging and facies analysis indicate that the Early Permian fluvial system in the study area was dominated by ephemeral fluvial processes influenced strongly by semi-arid to arid climate. Rapid (catastrophic?) flood events led to episodic sedimentation of poorly channelized, laterally extensive sheet-like bodies of sandstone as well as vertically and laterally amalgamated fluvial channel infills, with abundant upper-flow regime structures. The overbank deposits are poorly preserved due to the frequent lateral shifting of the channels. Soft sediment deformational structures formed due to events of river bank collapse as well as debris-flow facies point to high-energy, waning flows. It is concluded that deposition occurred on a broad, terminal-type alluvial fans, probably in their proximal- to medial sub-environments. Petrographic composition and measured paleocurrent directions show that the sediment was sourced from the framing massifs – the Sowie Mts. Block to the east and a hypothetical Southern Massif to the south/south-east.

The research was funded by the Polish National Science Centre (Grant 2017/26/M/ST10/00646).

References

Awdankiewicz, M., Kurowski, L., Mastalerz, K., Raczyński, P., 2003: Geolines 16, 165–183;

Nemec, W., Porębski, S.J., Teisseyre, A.K., 1982: Veröff. Zentralinst. Erde, Potsdam, 267–278;

Turnau, E., Żelaźniewicz, A., Franke, W., 2002: Geologia Sudetica 34, 9–16;

Wojewoda, J., Mastalerz, K., 1989: Przegląd Geologiczny 432, 173–180.

How to cite: Kowalski, A.: Development of an ephemeral fluvial system in continental fault-bounded basin – an example from the Early Permian Krajanów Formation of the Intra-Sudetic Basin (NE Bohemian Massif), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5008, https://doi.org/10.5194/egusphere-egu23-5008, 2023.

16:37–16:39
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PICO2.12
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EGU23-4906
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SSP1.1
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ECS
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Virtual presentation
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Akash Trivedi, Sudipta Sarkar, Stephan Ker, and Timothy A. Minshull

Active methane venting in the upper continental slope off western Svalbard results from methane hydrate dissociation caused by bottom water warming. Lithological heterogeneity in the glaciomarine sediments influences fluid migration, accumulation, and methane venting. However, seismic imaging with an airgun source could not resolve glaciomarine stratal architecture in the top 50 m below the seafloor (mbsf). We address this limitation by collecting several deep-towed high-frequency (220–1050 Hz) SYSIF seismic data (vertical and horizontal resolutions 1 and 3 m, respectively). Based on seismic interpretation, we improve the seismic stratigraphic framework and infer the depositional processes controlling the distribution of glaciomarine sediments in the interfan region between the Kongsfjorden and Isfjorden Trough Mouth Fans. We identify six seismic reflectors that separate five seismic units, 1 (youngest)–5 (oldest), characterize the seismic facies, and map the facies distribution in different units. We assign ages to the reflectors based on the results from the drill core GS10-164-09PC collected at 846 m water depth. Basal unit 5 consists of low amplitude, chaotic reflections indicating poorly sorted glacial debris materials above a basal erosional surface. The upper part of this unit is characterized by isolated, parallel, high to moderate-amplitude reflections embedded within low-amplitude chaotic reflections. The overlying unit 4 shows parallel, well-stratified, continuous reflections pinching out upslope. Unit 3 consists of chaotic facies that occur as isolated lenses. Unit 2 consists of moderate amplitude, parallel, well-stratified, continuous reflections. The topmost unit 1 shows low amplitude, parallel, continuous reflection.

The erosional base of unit 5 is a result of incision by strong hyperpycnal flow during the onset of early mid-Weichselian glaciation. The chaotic facies within unit 5 (74–54 ka) is attributed to glacial debris flow (GDF). Glacial advancement to the shelf break led to the formation of a till delta and debris flow as the delta front steepened and failed. On the uppermost slope, eastward dipping toe thrusts within the GDFs formed due to frontal obstruction caused by pre-existing debris mound. The well-stratified layers embedded within the GDFs suggest sediment deposition from turbidity currents that emerge as a result of the mixing of debris flow with water. The well-stratified reflections within uniformly thick unit 4 covering the GDFs are primarily a result of the deposition of hemipelagic materials by contour currents between 54 and 38 ka. The isolated chaotic lens in unit 3 represents debris flow lobes detached from the parent debris unit. Their deposition occurred during the last glacial maxima (38–24 ka) when the ice sheet re-advanced to the shelf break. The well-stratified reflections in unit 2 represent plumite deposition since the last deglaciation (24–15 ka). The low-amplitude reflections in unit 1 indicate finer winnowed sediments (15 ka–Present). The well-stratified contourites and turbidites in units 4 and 5 are suitable reservoirs that can store and transmit fluid more efficiently than the GDFs. The clustering of methane seeps above these shallowest reservoirs indicates flow focusing in those sediments after the methane hydrates have completely melted.

How to cite: Trivedi, A., Sarkar, S., Ker, S., and Minshull, T. A.: An improved Weichselian seismic stratigraphic framework of the Kongsfjorden-Isfjorden Interfan region off western Svalbard from high-frequency deep-towed seismic data and its implication on fluid migration and methane venting, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4906, https://doi.org/10.5194/egusphere-egu23-4906, 2023.

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