Modern sediment facies and dynamics of the Dry Tortugas, south Florida, USA: an isolated carbonate ramp

干龟是一个250平方公里的偏远碳酸盐浅滩地区，珊瑚礁和岛屿位于佛罗里达大陆架的西南边界。Tortugas平台的独特之处在于它可以被归类为孤立的碳酸盐斜坡，缺乏连续的边缘礁和周围的深水。计划收集。沿沿着五条东西走向横穿台地的路线采集150个沉积物样品，并进行结构、成分和埋藏学分析。该项目有三个目标。(1)通过对沉积物成分、结构的定量分析，结合海底观测资料，编制了陆龟孤立斜坡高分辨率相图。(2)沉积物颗粒的埋藏和早期成岩特征的空间变异性的估计，如磨蚀、破碎、钻孔、重结晶、胶结和溶解。(3)将沉积物成分和结构与1908- 1915年（Thorp 1936）和1967-69年（Jindrich 1972; Multer unpubl.）将为记录沉积物分布在世纪内的时间变化提供独特的机会。产生碳酸盐的生物体的生物变化和物理干扰（例如，大风暴;冷事件）可以被评估。申请人根据以前的数据集制作的初步相图产生了相的镶嵌图，而不是更大的连续相区。这可能是由于托尔图加斯独特的斜坡状地貌，缺乏连续的台地边缘和砂裙，陡峭的外侧翼和深台地内部，以及碳酸盐生产的高度局部变化。

The Dry Tortugas are a 250 km2 remote carbonate shoal area with coral reefs and islands located at the southwestern boundary of the Florida shelf. The Tortugas platform is unique in that it may be classified as an isolated carbonate ramp, lacking continuous marginal reefs and surrounding deep water. It is planned to collect ca. 150 sediment samples along five east-west traverses across the platform, and to perform textural, compositional, and taphonomic analyses. This project has three objectives. (1) The compilation a of high-resolution facies map of the Dry Tortugas isolated ramp based on the quantitative analysis of sediment composition and texture, and bottom observations. (2) The estimation of spatial variability in taphonomic and early diagenetic signatures of sediment particles such as abrasion, fragmentation, boring, recrystallization, cementation, and dissolution. (3) The comparison of sediment composition and texture with previous datasets of 1908-15 (Thorp 1936) and 1967-69 (Jindrich 1972; Multer unpubl.) will open the unique opportunity to record temporal variation in sediment distribution over a century. The influence of biotic changes in carbonate-producing organisms and physical disturbances (e.g., major storms; cold events) may be evaluated. Preliminary facies maps put together by the applicant based on the previous datasets result in a mosaic of facies rather than larger, continuous facies areas. This is presumably a consequence of the unique, ramp-like geomorphology of the Tortugas lacking a continuous platform margin with sand aprons, steep outer flanks, and a deep platform interior, in combination with high local variability in carbonate prodution.