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

尼加拉瓜湖和马那瓜湖是中美洲最大的湖泊和全球重要的水生生态系统，其起源至少可以追溯到上新世。它们悠久的历史和相关的地质特征注定了这些湖泊是研究具有地方、区域和全球意义的社会经济科学问题的天然实验室。这些湖泊也是特有的热点，位于靠近巴拿马地峡的古动物地理学关键位置，这使得研究新生代期间北美和南美物种最重要的多样化和灭绝事件之一成为可能。因此，ICDP倡议NicaBridge启动了，该倡议于2020年3月成功举办了ICDP研讨会，并计划了深层钻探的长期项目目标。为了实现这一目标，首先需要大大改进目前关于沉积物结构的知识，包括其组成、分布和随时间的变化，这也是本提案的目标。作为第一步，将扩大目前仅限于尼加拉瓜湖的少数现有地震资料。为此目的，计划进行一次深层勘测，以获得马那瓜湖的高质量地震数据。这些调查旨在探索湖盆的沉积物结构，并确定分层良好的沉积物序列，以及断层和块体运动沉积物。根据新的数据，将选择未来深层钻探的地点。数据还将用于了解盆地的总体演变情况，并为灾害评估提供信息，此外，还将从尼加拉瓜湖采集长达18米的活塞岩心和重力岩心，并从两个湖采集地表样本。将研究在这一活动期间获得的和以前项目提供的表面样品，以了解最近的湖泊内部沉积物分布和相关过程。沿着湖泊沿着采集的重力岩心将用于了解邻近火山的年轻火山活动，但也将允许调查前哥伦布时期和现代人类活动对湖泊的影响。然而，沉积学调查的主要重点将是通过活塞取芯恢复的（晚期）冰川条件的较长沉积物序列，因为没有关于更新世沉积物的信息，只有部分全新世沉积物的信息。将对沉积物的地球物理、地球化学和沉积学特性进行鉴定，并采用多测年法（14 C、火山灰年代学、磁性地层学）测定年代。对这些数据的联合解释将为盆地演化、该地区的古环境史以及上更新世以来自然灾害的发生和规模提供新的见解。这一信息将是制定一个潜在的深钻探活动的纳闽湖的基本。

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.