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

干燥的托尔图加斯是一个250平方公里的偏远碳酸盐浅滩区域，珊瑚礁和岛屿位于佛罗里达大陆架的西南边界。托尔图加斯平台的独特之处在于，它可以被归类为孤立的碳酸盐斜坡，缺乏连续的边缘生物礁和周围的深水。计划沿平台的五个东西走向收集约150个沉积物样本，并进行质地、成分和矿物学分析。这个项目有三个目标。(1)在沉积物成分和结构定量分析的基础上，结合海底观测资料，编制了干式托尔图加斯孤立坡道高分辨率相图。(2)沉积物颗粒的磨损、破碎、钻孔、重结晶、胶结和溶解等早期成岩特征的空间变异性估计。(3)沉积物组成和结构与1908-15年(Thorp 1936)和1967-69年(Jandrich 1972；Multer Unpubl.)这将为记录一个世纪以来沉积物分布的时间变化提供独特的机会。可以评估碳酸盐产生体的生物变化和物理干扰(例如，重大风暴；寒冷事件)的影响。申请人根据以前的数据集编制的初步相图产生了相的镶嵌，而不是更大的、连续的相区域。这可能是托尔图加斯独特的坡状地貌的结果，该地貌缺乏连续的台地边缘，没有砂质围裙、陡峭的外侧和深厚的台地内部，再加上碳酸盐生产的高度局部变异性。

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.