| Project Detail |
Initial rift basins are characterized by heterogeneous sedimentation patterns varying at short spatial and temporal scales. The interaction and feedback between tectonics, surface processes, climate variations and eustasy on sediment flux, sediment deposition and basin dynamics explain their complex stratigraphic architecture. Both, tectonic and eustatic drivers are controlling the basinal connectivity through bounding sills, and as such the rapid transition between isolated continental and semi-isolated or marine conditions. This turns the paleohydrological evolution of those basins complex. Besides, rapid salinity fluctuations in those initial rift basins are not only driven by the opening and closure of the gateways, but also by freshwater influx and dilution, precipitation-evaporation rates, water body stratification and/or overturning during the semi-isolated versus isolated phases. Yet, how tectonics, climate and eustasy interact to exceed the threshold on bounding sills in initial rift basins, and as such its paleoconnectivity and paleohydrology, at the verge between continental and oceanic settings is often still a matter of debate. Only through the study of the spatial distribution of sedimentary facies patterns and the full temporal evolution of the sedimentary record, the paleoconnectivity and complex paleohydrological evolution and budget in those basins can be unveiled. Although known as one of the most active rift regions on Earth and being a young incipient rift basin at the transition between continental rifting and oceanization, Pleistocene and Holocene sedimentary patterns in the Danakil Depression (northern Afar) has been only recently studied. First results indicate several cycles of opening and closure of the basin with the Red Sea, based on the mapping of elevated marine coralgal reef terraces and associated deposits at the western margin of the basin. Preliminary studies on subsurface core and seismic sections unveil that the central part of the basin is filled with more than 1.5 km of evaporites due to several cycles of flooding and desiccation which makes the Danakil Basin the youngest salt giant on Earth. Although the timing of opening and closure of the Danakil basin during Pleistocene times has been constrained, the localization of the gateways is not yet known due to the lack of regional studies along the eastern margin of the semi-enclosed Danakil Depression, and along possible connection pathways between the Danakil Depression and the western margin of the Red Sea. Moreover, the correlation between fragmented and discontinuous sedimentary facies (coralgal reefs, microbialites, crusts and gypsum deposits) in marginal outcrops and more continuous transitional facies (siliciclastic sediments, marls and evaporites) in subsurface core sections in the central part of the basin is missing. This hampers the full understanding of the paleohydrological evolution and hydrological balance of the Pleistocene Danakil Sea. The strong regional bias in data collection towards the western margin of the Danakil Depression, did not allow yet to compile an integrative stratigraphic framework. The overall goal of the CONNECT project is (1) to constrain and localize the gateways between the Pleistocene Danakil Sea and the Red Sea, (2) to unravel the paleohydrological evolution of the Danakil Basin and (3) to construct an integrative stratigraphic framework for the Danakil Basin. This will be mainly achieved through the mapping of coralgal reef terraces and associated deposits in marginal outcrops at the eastern margin of the Danakil Depression and along connection pathways. Pristine aragonitic coral skeletons will be selected for absolute U/Th dating. Sr-isotopes measured on microbialites, aragonite crusts and gypsum deposits will be used to constrain the paleohydrological budget of the basin and its connection with other water bodies (fresh water input versus Red Sea water). Facies, microfacies and component analyses in subsurface core sections will allow to understand the rapid and continuous paleohydrological evolution in the central part of the basin. Correlation between distinct sedimentary units in marginal outcrops with core sections, well log data and subsurface seismic data will allow the construction of an integrative stratigraphic framework. This will not only result in the better understanding of the complex stratigraphic architecture of passive rifted margins, but also the potential future evolution of the Danakil Depression considering future sea-level rise and rapid uplift/subsidence rates. The better understanding of complex facies variations related to the paleohydrological evolution of Danakil Sea will definitely provide keys to solve controversies on the origin and evolution of other salt giants on Earth and beyond, such as for example the Messinian evaporites in Mediterranean regions. Finally, unravelling the paleoconnectivity and paleohydrology of the Danakil Depression, will also help in evaluating the relative role of climate variations, eustasy and tectonics on the out-of-Africa migration of Homo Sapiens. |
