Assateague Island sediment core radiochemistry data from March-April 2014, USGS Field Activity Number 2014-301-FA

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.

热带气旋与温带气旋（tropical and extratropical cyclones）对滨海湿地与沼泽的影响在时空尺度上均表现出显著的异质性，其作用效果受气候、地质及物理等多类变量共同调控。风暴对湿地与沼泽生态系统的影响兼具正负两面性：风暴或其他极端事件所携带的少量至中等体量的无机沉积物，可有效缓解海平面上升带来的胁迫压力；但若沉积物总量过大、沉积层厚度过高，则会导致有机基质发生压实作用，进而引发湿地淹没与高程损失。同理，厚层粗粒无机沉积物亦可能改变研究区域的水文条件，阻碍植被生理过程。风暴相关的其他潜在影响还包括沼泽岸线的侵蚀，以及可能出现的地表出露现象。对上述各类响应结果及其潜在长期效应的预测，可通过对历史及近期事件沉积记录的系统性评估实现。本研究的目标分为两点：其一，表征从残留型到近期形成的冲溢扇（washover fans）与障后沼泽（back-barrier marshes）的表层沉积物特征；其二，对障后沼泽的6个沼泽岩芯（marsh cores）以及大陆附近的1个沼泽岛岩芯的沉积物特征进行解析。上述地质数据将与马里兰州/弗吉尼亚州阿萨蒂格岛（Assateague Island）沿岸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。