Sedimentological and radiochemical characteristics of marsh deposits from Assateague Island and adjacent vicinity, Maryland and Virginia, following Hurricane Sandy

The influence of tropical and extratropical cyclones on coastal wetlands and marshes is highly variable in both space and time and depends on a number of climatic, geologic, and physical variables. The impacts storms can be either positive or negative with respect to the wetland and marsh ecosystems. Small to moderate amounts of inorganic sediment added during storms or other events helps to abate pressure from sea-level rise. However, if the volume of sediment is large and the resulting deposits thick, the organic substrate may compact causing submergence and a loss in elevation. Similarly, thick deposits of coarse inorganic sediment may also alter the hydrology of the site and impede vegetative processes. Alternative impacts associated with storms include shoreline erosion at the marsh edge as well as potential emergence. Predicting the outcome of these various responses and potential long-term implications can be obtained from a systematic assessment of both historical and recent event deposits. The objectives of this study are to 1) characterize the surficial sediment of the relict to recent washover fans and back-barrier marshes, and 2) characterize the sediment of 6 marsh cores from the back-barrier marshes and a single marsh island core near the mainland. These geologic data will be integrated with other remote sensing data collected along Assateague Island, Maryland / Virginia and assimilated into an assessment of coastal wetland response to storms.

热带与温带气旋（tropical and extratropical cyclones）对滨海湿地与沼泽的影响在时空尺度上均存在显著变异性，且受多种气候、地质及物理变量共同调控。风暴对湿地与沼泽生态系统的影响可兼具正向与负向效应：风暴或其他事件带来的少量至中等体量的无机沉积物输入，有助于缓解海平面上升带来的胁迫。然而，若沉积物输入量过大且沉积层过厚，有机基质可能发生压实作用，进而导致湿地被淹没、高程降低。同理，厚层粗粒无机沉积物亦可改变研究区域的水文条件，阻碍植被生长与生态过程。风暴带来的其他次生影响还包括沼泽岸线侵蚀，以及潜在的陆地出露。对上述多样响应结果与潜在长期影响的预测，可通过对历史及近期事件沉积层开展系统评估实现。本研究的目标分为两点：1）表征从遗迹沉积至近期形成的冲溢扇（washover fans）与障后沼泽（back-barrier marshes）的表层沉积物特征；2）分析取自障后沼泽的6个沼泽岩芯（marsh cores），以及大陆附近单个沼泽岛岩芯的沉积物特征。上述地质数据将与沿马里兰州与弗吉尼亚州交界处的阿萨蒂格岛（Assateague Island）采集的其他遥感数据（remote sensing data）进行整合，并用于滨海湿地对风暴响应的评估研究。