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（tropical cyclones）与温带气旋（extratropical cyclones）对滨海湿地与沼泽的影响在时空尺度上均呈现高度变异性，且受多种气候、地质及物理变量制约。风暴对湿地与沼泽生态系统的影响可分为正向与负向两类：风暴或其他事件过程中沉积的少量至中等体量的无机沉积物，有助于缓解海平面上升带来的胁迫。但若沉积物总量过大且沉积层过厚，则有机基质可能发生压实，进而引发湿地淹没及高程损失。同理，厚层粗粒无机沉积物也可能改变研究区域的水文状况，阻碍植被生长过程。风暴带来的其他影响还包括沼泽边缘的岸线侵蚀，以及潜在的滩涂出露。通过对历史及近期风暴沉积事件开展系统性评估，可预测上述各类响应的结果及其潜在长期影响。本研究的目标为：1）表征从残留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）对取自障后沼泽的6根沼泽岩芯及大陆附近单根沼泽岛岩芯的沉积物进行特征分析。本研究将把这些地质数据与在马里兰州/弗吉尼亚州阿萨蒂格岛沿岸采集的其他遥感数据进行整合，并将其纳入滨海湿地对风暴响应的评估研究。