Seismic Stratigraphic Reconstruction of Cretaceous to Holocene Current Flow Through the Southeastern Gulf of Mexico

墨西哥湾的海洋环流由环流主导，环流通过墨西哥和古巴之间的尤卡坦海峡流入墨西哥湾，然后在墨西哥湾周围盘旋，然后进入佛罗里达和古巴之间的佛罗里达海峡，在那里形成佛罗里达海流并注入墨西哥湾流。这个相互连接的洋流系统是大西洋向北输送热量的主要机制之一，因此对北美和欧洲的气候有着关键影响。尽管环流对区域和全球气候的重要性，但人们对其长期历史知之甚少，包括它是何时建立的以及它如何随着时间而变化。例如，了解环流如何影响热量向北输送以应对外部强迫的变化，对于重建海洋/气候历史和预测未来变化至关重要。幸运的是，过去环流行为的独特记录保存在海底的沉积物漂移沉积物中。当洋流流过海底时，它们会移动沉积物。沉积物从水流较强的地方被侵蚀，在流速下降的地方沉积。随着时间的推移，这些沉积物可以形成厚厚的堆积物，称为漂流沉积物，代表了数百万年来过去水流的档案。最近的回声测深仪调查已经确定了墨西哥湾坎佩切浅滩上的沉积物漂移。在邻近的深水沃茨，1980年代进行的地震勘测揭示了海底的大型特征，这些特征似乎也是沉积物漂移，尽管这些较旧的数据没有分辨率来看到内部特征，而这些特征是解释海流强度和位置变化的关键。该项目将对这两个地区的矿床进行高分辨率多通道地震调查，以绘制和确定这些矿床的性质，并利用其三维地震结构重建过去9 000万年来墨西哥湾的环流。所获得的地震数据也将用于该区域未来可能进行的科学钻探的现场勘测，这是一个多国合作项目，正在与墨西哥国立自治大学以及来自德国和古巴的科学家进行合作。项目小组将在墨西哥国立自治大学的Justo Sierra号研究船上安装得克萨斯大学地球物理研究所的便携式多通道地震系统，沿坎佩切河岸和邻近的深水环境沿着进行地震勘测，以便对那里的漂流沉积物进行成像。沉积单元的年龄将通过追踪其中的关键层位到深海钻探项目以前在研究区域内收集的岩心来确定。综合数据将用于检验以下假设：1）进入墨西哥湾东部的水流强度的变化驱动了坎佩切浅滩和邻近深水的沉积结构的变化; 2）整个新生代的逐渐冷却加强了墨西哥湾东部的水流，导致一些地区的冲刷增加，其他地区的漂流沉积增加; 3）坎佩切浅滩上的漂流沉积物可追溯到晚白垩世，表明存在进入墨西哥湾约9000万年的原环流; 4）尤卡坦和佛罗里达海峡之间较深盆地中的重要漂流沉积物可追溯到始新世/渐新世边界，并追踪北大西洋深水流入墨西哥湾的情况。通过识别和研究墨西哥湾东部的漂流沉积物，该项目将为未来的科学海洋钻探铺平道路，以更详细地研究这些漂流物并研究墨西哥湾环流和气候的变化。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ocean circulation in the Gulf of Mexico (GoM) is dominated by the Loop Current, which flows into the Gulf through the Yucatan Channel between Mexico and Cuba and then loops up and around the Gulf before entering the Florida Straits between Florida and Cuba, where it forms the Florida Current and feeds into the Gulf Stream. This system of connected ocean currents is one of the main mechanisms for transporting heat northward in the Atlantic Ocean and thus has a key influence on the climate of North America and Europe. Despite the importance of the Loop Current for regional and global climate, little is known about its long-term history, including when it was established and how it has varied through time. Understanding how the Loop Current has impacted the northward delivery of heat in response to changes in outside forcing, for example, is critical for reconstructing ocean/climate history and for predicting future changes. Fortunately, a unique record of past Loop Current behavior is preserved in sediment drift deposits preserved on the ocean floor. As currents flow across the seafloor, they move sediment around. Sediment is eroded from areas where currents are stronger and deposited where current velocity drops. Over time, these sediments can form thick accumulations known as drift deposits that represent archives of past current flow over millions of years. Recent echosounder surveys have identified sediment drifts on the shallow Campeche Bank in the GoM. In the adjacent deep waters, seismic surveys conducted in the 1980s revealed large features on the seafloor that also appear to be sediment drifts, though these older data do not have the resolution to see internal features that are key to interpreting changes in current strength and position. This project will conduct a high-resolution multichannel seismic (MCS) survey of the deposits in both regions to map and determine the nature of these deposits and use their 3-D seismic architecture to reconstruct the Gulf of Mexico's Loop Current over the past 90 million years. The seismic data obtained will also be used as a site survey for potential future scientific drilling in the region.This project is a multinational collaboration being conducted with scientists at the National Autonomous University of Mexico (UNAM) and from Germany and Cuba. The project team will deploy the University of Texas Institute for Geophysics' portable multichannel seismic system on board UNAM's R/V Justo Sierra to conduct a seismic survey along the Campeche Bank and adjacent deep-water environments to image the drift deposits there. The ages of the sedimentary units will be determined by tracing key horizons within them to cores previously collected within the study area by the Deep Sea Drilling Project. The combined data will be used to test the following hypotheses: 1) changes in the strength of currents entering the eastern GoM drove changes in the sedimentary architecture of both the shallow Campeche Bank and the adjacent deeper water; 2) progressive cooling throughout the Cenozoic has strengthened current flow in the eastern GoM, resulting in both increased scour in some areas and increased drift deposition in others; 3) drift deposits on shallow Campeche Bank extend back to the Late Cretaceous, indicating the presence of a proto-Loop Current entering the GoM for ~90 million years; and 4) significant drift deposits in the deeper basin between the Yucatan and Florida Straits date back to the Eocene/Oligocene Boundary and track the inflow of North Atlantic Deep Water into the GoM. By identifying and studying drift deposits in the eastern GoM, this project will pave the way for future scientific ocean drilling to core these drifts and study changes in Gulf of Mexico circulation and climate in much greater detail.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.