ORCID Profile
0000-0003-0385-7686
Current Organisation
Université de Genève
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Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-6826
Abstract: Submarine fans are deposits of coarse sediments of continental origin in the deep sea, and are generally characterized by a complex depositional architecture, due to the multiple triggering mechanisms of deep-water sediment gravity flows. Consequently, this poses great challenges to deep water petroleum exploration and development. We analyzed the geomorphologic evolution and architecture of C anian, deeply buried, submarine fans in the Kribi-C o sub-basin, offshore Cameroon. Using a 3D seismic reflection data set and logs from two wells, we mapped seven horizons, including the fan base, fan top and five internal horizons. In cross-section, the fan is characterized by a high litude seismic facies exhibiting an aggradational pattern with parallel and continuous reflectors. The stacked fan-shaped morphology is up to 340 ms TWT thick, extends over an area of 600 km2 and oriented NE-SW, near the Kribi High. The analysis of lobes and channels on each horizon provided a timelapse that captures the major geomorphologic transformations of the submarine fan from its initiation, growth, and abandonment. & The submarine fan is composed of depositional lobes whose beds consist of sand, silt and mud. The detailed structure of these lobes has a finger-like morphology and is generally oriented at high angles to the channel that delivered the sediment to the lobes. The finger-like features are interpreted as thick massive sands, formed as a result of sediment-gravity flows which branched off the main flow eroding into pelagic clay substrate. Two types of channel morphology were identified (straight and sinuous). Our results show that channel and sand-body architecture evolve in a predictive manner, primarily controlled by fan aggradation. The elongated shape and morphology of the submarine fan may arise from the interaction of the fault-related folds and Kribi High, with sandstone deposition within the intervening topographic lows, sourced from the east. The 3D seismic geomorphological analysis of the submarine fan, as presented in this study, is essential to better understand their geometries, facies distribution, stacking patterns and depositional architecture to improve reservoir predictions.
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-2105
Abstract: The Indo-Pacific Warm Pool (IPWP) is the warmest and most dynamic ocean-atmosphere-climate system on Earth and has undergone significant climatic changes during the Pleistocene glacial periods (De Deckker et al., 2012 Lea et al., 2000 Russell et al., 2014). During the Last Glacial Maximum, the latitudinal position of the Southern Ocean fronts, both south of Africa and Australia, was shown to be critical in controlling the outflow of warm water of the Agulhas Current from the Indian Ocean and the IPWP area. Yet, there is no direct evidence for such oceanic change on the scale of the Late Pleistocene glacial-interglacial transitions.Here, we combine sea surface temperature proxies (d18O and Mg/Ca) with the neodymium (Nd) isotopic signature to reconstruct changes in climate and oceanic circulation in the eastern tropical Indian Ocean over the last 500 ka. The most striking feature of our dataset is the oscillating Nd signal that mimics the glacial-interglacial cycles. While interglacial periods are characterized by a more significant contribution from the less radiogenic Antarctic intermediate water mass (AAIW, ~ -7 & #949 Nd), glacial periods are marked by more radiogenic water mass of Pacific origin (~ -5 & #949 Nd). We argue that under global cooling, the northward penetration of the AAIW has weakened due to the general slowdown of the global thermohaline circulation. Furthermore, the oscillating pattern is also recorded in the sea surface temperature and salinity, indicating the settlement of cooler and more saline surface water masses probably linked to a less expanded IPWP and weaker Leeuwin Current during glacial intervals.We suggest that under low AAIW a less intense advective mixing occurred, allowing a deepening of both halocline and thermocline in the tropical eastern Indian Ocean. Our new proxy-derived dataset confirms results from models (DiNiezo et al., 2018), suggesting that these ocean conditions could lify the externally forced climate changes resulting from drier atmospheric conditions and weaken the monsoon during glacial periods in the Indonesian region.
Publisher: Springer Science and Business Media LLC
Date: 19-11-2013
No related grants have been discovered for Elias Samankassou.