Schwenk, Tilmann
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Item-typ:Veröffentlichung, The Bengal Fan: architecture, morphology and depositional processes at different scales revealed from high-resolution seismic and hydroacoustic data(2004-02-12); ; ; The Bengal Fan has developed as a result of the collision of India with Asia, resulting in the orogeny of the Himalayas. Erosion of the Himalayas since Eocene times had formed the largest submarine fan on Earth today. Accordingly, the Bengal Fan is well suited to study the tectonic and climatic history of the Himalayas, but also to analyze architecture and depositional processes of submarine fans and channel-levee systems in general. In this thesis, the active channel-levee system of the Middle Bengal Fan is described by a combined analysis of Parasound and Hydrosweep data. Morphological parameters of the channel and the structure of the levees are analyzed. The results are used to describe the built-up of the active channel-levee system, which is mainly controlled by frequent avulsions within the system leading to numerous cut-off loops. The development of the system is then discussed and compared with other submarine fans. Furthermore, high-resolution seismic data are used to reveal the structure of the active and buried channel-levee systems on the Middle Bengal Fan. Downfan changes of the individual channel-levee systems are analyzed, and differences between the systems are discussed. Two evolutionary scenarios for the active and one buried system are developed and discussed. Finally, the reservoir potential of channel-levee systems in the study area is described. Additionally, high-resolution seismic data collected on four long east-west profiles located on the Middle and Lower Bengal Fan are analyzed. The architecture of surface and buried channel-levee systems and their downfan variations are revealed and the built-up of distinct channel-levee complexes on the upper Middle Fan is discussed. The seismic stratigraphy of the southern profiles is linked to results of DSDP Site 218 and of the ODP Leg 116 site. The seismic results are discussed with respect to deformation events in the central Indian Ocean and to tectonic and climatic events in the Himalayas.Dissertation343 350 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Evolution of a buried moat–drift system in the Ewing Terrace uncovering highly dynamic bottom currents at the Argentine margin from the early Oligocene to middle Miocene(Society for Sedimentary Geology, 2024-11-23); ; ; ; The Ewing Terrace is a relatively flat surface formed by the action of bottom-currents and part of a Contourite Depositional System (CDS) at the Argentine continental slope. It is situated in a highly complex oceanographic setting at the Brazil-Malvinas Confluence Zone. Located in water depths of ~1000–1200 m and incised by the Mar del Plata Canyon, the Ewing Terrace is separated into the Northern Ewing Terrace (NET) and the Southern Ewing Terrace (SET). The long-term variations in ocean circulation led to a complex internal architecture of the terrace. As a result, this region represents a unique archive for studying sedimentary features that were eroded, transported, and deposited by along- and down-slope processes. An in-depth data analysis of high-resolution multichannel seismic profiles exhibits a complex sequence of erosional and depositional contouritic features, namely buried moat-drift systems identified in depths of ~ 370-750 m below the seafloor. They are arranged in migrating sequences and clustered in the Early Oligocene to Middle Miocene. This pattern is probably attributable to the vertical shift of water masses and to a highly dynamic oceanographic setting with spatial changes influenced by the Brazil-Malvinas Confluence Zone over this particular geological time. The moat-drift systems reveal significant lateral changes from north to south. In the southern area of the SET, the moats are constructional, and the associated separated mounded drifts are well developed. In contrast, the northern area exhibits two types of moats, reminiscent of cut-and-fill structures that mirror the significant and rapid changes in bottom current dynamics. With these new insights, this study contributes to a better understanding of moat-drift systems and improves the knowledge about past oceanographic dynamics and sediment deposition at the northern Argentine margin.Wissenschaftlicher ArtikelBand:94Heft:660 59