This session addresses the dynamics of sedimentary basins at different temporal and spatial scales and aims to bring together a wide range of studies focusing on geodynamics, tectonics and sediment dynamics. Contributions addressing major processes affecting the genesis and evolution of basins are in particular encouraged (from rifting and overlying passive continental margins to orogenic, intra-montane and extensional back-arcs in convergent settings). A wide range of studies are encouraged, aimed at understanding the evolution of sedimentary fill, the underlying crustal and lithospheric -scale dynamics as well as the integration with processes taking place in the source areas, such as active orogens or long-term landscape evolution. We welcome contributions integrating data from different depth levels of the lithosphere with the shallower parts of the basin system as subsidence pattern, stress, vertical motions, erosion and sedimentation dynamics, thermal structure, lithosphere dynamics and (active) faulting by the means of observational studies, numerical and analogue modeling, or their combination. Studies yielding constraints on a variety of conceptual and quantitative models explaining the origin and evolution of basins are also welcomed.Session sponsored by the International Lithosphere Program Task Force VI Sedimentary Basins
4:15pm - 4:45pm
Subduction Dynamics and Rheology Control on Forearc and Backarc Subsidence: Numerical Models and Observations from the Mediterranean
1ETH Zurich, Department of Earth Sciences, zurich, Switzerland; 2Università Roma Tre, Rome, Italy
The dynamics of subduction zones is linked to the rise and demise of forearc and backarc sedimentary basins in the overriding plate. Subsidence and uplift rates of these distinct basins are controlled by variations in plate convergence and subduction velocities and determined by the rheological and thermal structure of the lithosphere. In this study we conducted a series of high-resolution 2D numerical models of oceanic subduction and subsequent continental collision. The numerical code 2DELVIS involves erosion, sedimentation, and hydration processes. The models show the evolution of wedge-top basins overlying the accretionary wedge and retro-forearc basins in the continental overriding plate, separated by a forearc high. These forearc regions are affected by repeated compression and extension phases. Higher subsidence rates are recorded in the syncline structure of the retro-forearc basin when the slab dip angle is higher and the subduction interface is stronger. This implies the importance of the slab suction force as the main forcing factor creating up to 3-4 km negative residual topographic signals. Extensional back-arc basins are either localized along inherited weak zones at large distance from the forearc region or are initiated just above the hydrated mantle wedge. Back-arc subsidence is primarily governed by crustal and lithospheric thinning controlled by slab roll-back. Our results are compared with the evolution of the Mediterranean and we classify the Western and Eastern Alboran, Paola and Tyrrhenian, Transylvanian and Pannonian Basins to be genetically similar forearc–backarc basins, respectively.
4:45pm - 5:00pm
Deepwater Systems Reloaded: Advances on our understanding on submarine lobe deposits
1Leibniz Universität Hannover, Germany; 2University of Leeds, UK; 3Utrecht Universiteit, NL; 4University of Manchester, UK; 5University of Liverpool, UK; 6University of Calgary, Canada; 7Beicip-Franlab, France; 8Durham University, UK
Submarine lobes are high aspect ratio sand-rich deposits that are fed by turbidity currents and debris flows via channels in deep-marine settings. As a major component of submarine fans, they represent 1) an important archive of palaeo-environmental change, 2) sinks for organic carbon and pollutants, and 3) are also of economic interest. Classic models describe lobes as purely depositional tabular sheets that thin and fine from an apex. Over the last decade, outcrop studies, numerical and stochastic modelling, and flume tank experiments have been undertaken to constrain the hierarchy, geometries and stacking patterns of submarine lobe deposits and test these simple models for lobe deposition.
With this talk I want to give an insight into the discoveries made and new understanding gained about lobe deposits, including: 1) The variety of lobe fringe deposits depending on the level of confinement experienced by the lobe: Distinguishing frontal and lateral lobe fringes enables more accurate reconstructions of the geometry, distribution, and orientation of deep-water lobes, whereas the recognition of aggradational lobe fringes enables the reconstruction of subtle intrabasinal relief. 2) Boundary conditions governing lobe dimensions: lobe dimensions, and their relation to their feeder channels, vary with basin-floor angle, and the concentration of sediment within the feeding gravity-current. Discharge rate is also important, controlling when deposition starts. Because these parameters change during evolution of natural deepwater systems, lobes formed at different times will have different geometries.
5:00pm - 5:15pm
Evolution and Modeling of the Carbonate-Clastic Permian system in the Jeffara Basin, Central Tunisia
1Department of Geoscience and Engineering, Delft University of Technology, Delft, The Netherlands; 2Mazarine Energy BV, Tunis, Tunisia; 3Universite de Tunis El Manar, Campus Universitaire Farhat Hached BP94, 1068 Tunis, Tunisia
Permian deposits are found in outcrops and in the subsurface of Central Tunisia. Their sedimentary and stratigraphic characteristics and origin are not fully understood and represents the main focus of this work. Base level changes, location of the palaeo-coastline and stratigraphic architecture and sandstone connectivity of formations are insufficiently known. Answering these questions will impact future hydrocarbon exploration and improve the geological understanding of Tunisia.
Seismic lines and well data of the Jeffara Basin have been re-interpreted and seismic data converted to depth domain. The results indicate a shallow marine rimmed shelf depositional environment, with dimensions of 100 square kilometers and a general east-west orientation. Seventy kilometers to the north of the reconstructed paleoshore line twelve stacked reef complexes up to 3000 meters thick were identified. Literature study of the area indicates a tropical climate. Structurally, it was observed that the Permian is not affected by major normal faults and appears at large scale gently folded. Wells and outcrop investigations provide lithological information, which is composed of limestone and dolomite, with intervals of sand and shale. The thickness gradually increases northwards, reaching 4000 meter maximum.
Using DionisosFlow, 3D stratigraphic models are constructed. They provide a number of equiprobable scenarios of facies distribution through the basin matching the available data. This modelling approach highlighted the impact of base level changes on reef geometry and in the lateral connectivity of clastic deposits. It also indicates depocenters shifting, shoreline evolution and feeder systems position and importance over time.
5:15pm - 5:30pm
Structural modelling of Agbada (Tertiary) sandstone reservoirs in “Atled Creek”, Onshore Niger Delta, Nigeria
1Structural Geology and Tectonics, Institute of Applied Geosciences, KIT - Karlsruhe Institute of Technology, Adenauerring 20a, 76131 Karlsruhe, Germany; 2Shell Petroleum Development Company, Rumuobiakani, Port Harcourt, Rivers State, Nigeria; 3Department of Geoscience, University of Tübingen, Sigwartstraße 10, 72076 Tübingen, Germany
The distribution of rocks and rock properties is an important part of an overall strategy for reservoir development, placement of new wells and prediction of future production. It also provides a detailed look into the local development of a sedimentary basin. Here we present a case-study from the “Atled Creek” concession, onshore Nigeria. A 3D structural reservoir model of the concession was prepared from available industry seismic data and well logs. Four sandstone reservoirs within the Cenozoic have been identified in the “Atled Creek” and modelled in this study to highlight variations in the reservoir properties. Four available wells were subjected to conventional well log analyses and reservoir units were mapped on the 3D seismic volume. The resulting facies and property logs were upscaled and together with the interpreted seismic horizons and faults formed the input data for facies and property modelling. This resulted in frameworks of 3D facies, petrophysical and fault models. The fault model revealed the dominance of generally W–E trending faults. A major fault trending WNW –ESE (F1) separates the reservoirs into two major blocks with the existing well located in the southern block. Fault assisted anticlinal closure is likely the prominent trapping mechanism revealed by the structural model. The reservoir model classified the reservoirs as moderate to good with total porosity of 23.8 – 34.7% in reservoir unit A, 6.3 – 33.1% in reservoir unit B,3.1 – 42.8% in reservoir unit C and 6.4 – 41.7% in reservoir unit D.
5:30pm - 5:45pm
The influence of sea-level changes on Eocene coastal wetlands during greenhouse conditions at the southern edge of the proto-North Sea in Northern Germany
Senckenberg Gesellschaft für Naturforschung, Germany
The sedimentary succession of the Helmstedt Lignite Mining District at Schöningen in northern Germany includes the upper Paleocene to lower Eocene Schöningen Formation and the middle Eocene Helmstedt Formation. It covers the entire Paleogene greenhouse phase including the long-term Early Eocene Climatic Optimum (EECO) and short-term events such as the Paleocene-Eocene Thermal Maximum (PETM/ETM1) and its gentle demise almost continuously in an estuarine situation at the southern edge of the proto-North Sea. Due to the interaction between changes in sea level, salt withdrawal in the subsurface and climate-related changes in runoff from the hinterland the area was subject to frequent changes between marine and terrestrial conditions, repeatedly leading to peat formation. A new robust stratigraphic framework for the succession is based on a combination of biostratigraphy, eustatic sea-level changes and carbon isotope data.
The more than 200 m thick succession with 13 up to 15 m thick lignites offers a rare opportunity to study Paleocene–Eocene near-coastal ecosystems and to trace the effects of long- and short-term climate change on the diversity and composition of the plant communities across 10 million years during the Paleogene greenhouse. As far as known, the estuarine succession at Schöningen is worldwide unique with respect to duration and continuity. The aim of an ongoing project is to study the response of the vegetation in this paralic environment to climate change by applying pollen and spores as proxies.