Deep seismic and Late Quaternary sedimentological investigations of the great lakes of Nicaragua (NicaBridge ICDP pre-site survey)

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Lake Nicaragua and Managua are the largest lakes of Central America and globally important aquatic ecosystems, whose origin dates back to at least the Pliocene. Their long history and associated geological features predestine the lakes as natural laboratories to study socio-economic scientific issues of local, regional and global significance. The lakes are also endemic hotspots located in a paleozoogeographic key position close to the isthmus of Panama, which enables studying one of the most important diversification and extinction events of North and South American species during the Cenozoic. Therefore, the ICDP initiative NicaBridge was launched, which conducted a successful ICDP workshop in 03/2020, where the long-term project goal of a deep drilling was planned. To achieve this goal, at first the current knowledge about the sediments’ architecture, including their composition, distribution and variability over time need to be improved significantly, which is targeted in this proposal. In a first step the few existing seismic information, which are currently limited to Lake Nicaragua, will be extended. For this purpose, a deep survey is planned to obtain high-quality seismic data of Lake Managua. These investigations aim at exploring the sediment’s architecture of the lake basin and to identify well-stratified sediment sequences, but also faults and mass movement deposits. Based on the new data, sites for future deep drilling will be selected. Data will also be used to understand the general basin evolution and to provide information for hazard assessment.In addition to that, up to 18 m long piston cores from Lake Nicaragua and gravity cores as well as surface samples will be recovered from both lakes. Surface samples obtained during this campaign and provided from a previous project will be studied to understand the recent lake internal sediment distribution and associated processes. Gravity cores taken along the lakes will be used to understand the younger volcanic activity of the adjacent volcanoes, but will also allow to investigate the pre-Columbian and modern anthropogenic impact on the lakes. The major focus of the sedimentological investigations, however, will be on longer sediment successions of (late)glacial conditions recovered by piston coring since no information about sediments from the Pleistocene and only partly of the Holocene are available. Sediments will be characterized for their geophysical, geochemical and sedimentological properties and dated by a multi-dating approach (14C, tephrochronology, magnetostratigraphy). Joint interpretation of the data will provide new insights into basin evolution, the paleoenvironmental history of the region, and the occurrence and magnitude of natural hazards since the Upper Pleistocene. This information will be fundamental for developing a potential deep drilling campaign of the Nicaraguan lakes.