RAPID: Investigating the Link between Fluvial Flood Events, Remobilization, and Preservation in the Stratigraphic Record along the Northwestern Gulf of Mexico Continental Shelf

这项建议由沉积地质学和古生物学计划(EAR/GEO)和海洋地质和地球物理计划(OCE/GEO)共同资助。与拥有广泛泥沙输送系统的大河流或大河口不同，这些较小的河流有一条更直接的泥沙进入海洋的路径，因此保持了更好的洪水事件信号。这些以事件为主导的河流通常反映的是气候变化，而不是季节循环。这导致了保存在海洋沉积沉积物中的过去洪水事件的记录，可以洞察较长时间尺度上的气候变化。从区域上了解这些过去的气候变化，对于预测未来气候变化的变化至关重要。不幸的是，由于沉积物沿大陆边缘扩散的复杂性，利用海洋沉积记录开发强大的河流洪水替代指标并不是一个简单的应用。该项目旨在利用布拉索斯河最近发生的接近历史的洪水，布拉索斯河是一条流入墨西哥湾的中等规模的断断续续的河流，旨在调查洪水沉积是如何最终保存在大陆架沉积物记录中的。由于这条河流内的大洪水通常是厄尔尼诺条件下的结果，保存在沉积记录中的洪水沉积物将反映过去与厄尔尼诺事件有关的强烈洪水时期。这项研究的目的是根据这一最新的洪水事件，开发一个高流量/厄尔尼诺现象的GOM西北部替代模型，这可能对未来的古气候研究有用。为此，PI计划沿河口和远岸沉积中心之间的陆架进行两次采样巡航，收集沉积物岩心，这一特征被称为德克萨斯泥毯(TMB)。这些巡航将在洪峰流量后大约3个月和6个月进行，以调查：1)洪水沉积在这段时间内如何变化；2)单一事件期间可能输送到TMB的部分；以及3)TMB事件层的保存潜力。为了回答这些问题，他们将通过分析各种沉积学性质来圈定岩心中的洪泛层，包括：物理特征、短期放射性同位素(例如7Be和234)，以及来自XRF岩心测井的元素组成。了解这些沉积特征将有助于为这类事件建立适当的环境指标。这项研究的一些更广泛的影响包括资助一名早期职业科学家，以及让本科生和研究生参与和培训地球科学研究，其中许多人将来自传统上代表性较低的群体。

This proposal was co-funded by the Sedimentary Geology and and Paleobiology Program (EAR/GEO) and the Marine Geology and Geophysics Program (OCE/GEO)AbstractSediment dispersal in the marine environment from small and moderately sized rivers can often be significantly impacted by episodic events such as large floods. Unlike large rivers with extensive sediment routing systems or large estuaries at their mouths, these smaller rivers have a more direct sediment path to the ocean, thus maintaining a better signal of the flood event. These episodic-event dominated rivers typically reflect climate variability rather than seasonal cycles. This results in the record of past flood events preserved in the marine sedimentary deposit that can give insight into climatic variations over longer time scales. Understanding these past climatic variations regionally will be critical for anticipating future variations due to climate change. Unfortunately, developing strong proxies for river floods using the marine sedimentary record is not a straightforward application due to the complexities of sediment dispersal along continental margins. This project aims to take advantage of recent, near historic floods on the Brazos River, a moderately sized, episodic river draining into the Gulf of Mexico (GOM), to investigate how a flood deposit is ultimately preserved in the continental shelf sediment record. As large floods within this river typically result from El Niño conditions, flood deposits preserved in the sedimentary record will reflect past periods of intense flooding associated with El Niño events in the northwestern GOM. The goal of this study is to develop a high-discharge/El Niño proxy for the northwestern GOM based on this most recent flood event that may be useful for future paleo-climate studies. To accomplish this, PIs plan to collect sediment cores during two sampling cruises along the shelf between the river mouth and the distal depocenter, a feature known as the Texas Mud Blanket (TMB). These cruises will take place at approximately 3 and 6 months following peak discharge to investigate: 1) how the flood deposit changes over this time period; 2) the fraction that may be transported to the TMB during a single event; and 3) the preservation potential of event layers in the TMB. To answer these questions they will delineate the flood layer in the cores by analyzing a variety of sedimentological properties including: physical characteristics, short-lived radioisotopes (e.g. 7Be and 234Th), and elemental composition from XRF core logging. Understanding these depositional characteristics will help to establish an appropriate environmental proxy for such events. Some of the broader impacts from this study include funding an early career scientist, and engaging and training undergraduate and graduate students in geoscience research, many of which will be from traditionally under represented groups.