Elevation of the regional transgressive unconformity underlying the inner shelf of Long Bay (Grid; transgr_grd)

In 1999, the U.S. Geological Survey (USGS), in partnership with the South Carolina Sea Grant Consortium, began a study to investigate processes affecting shoreline change along the northern coast of South Carolina, focusing on the Grand Strand region. Previous work along the U.S. Atlantic coast shows that the structure and composition of older geologic strata located seaward of the coast heavily influences the coastal behavior of areas with limited sediment supply, such as the Grand Strand. By defining this geologic framework and identifying the transport pathways and sinks of sediment, geoscientists are developing conceptual models of the present-day physical processes shaping the South Carolina coast. The primary objectives of this research effort are: 1) to provide a regional synthesis of the shallow geologic framework underlying the coastal upland, shoreface and inner continental shelf, and define its role in coastal evolution and modern beach behavior; 2) to identify and model the physical processes affecting coastal ocean circulation and sediment transport, and to define their role in shaping the modern shoreline; and 3) to identify sediment sources and transport pathways; leading to construction of a regional sediment budget.
This data set contains a surface depicting the elevation of the regional transgressive unconformity underlying the inner shelf of Long Bay, offshore of the South Carolina Grand Strand. Chirp seismic data collected with Benthos SIS-1000 and Edgetech SB-512 acquisition systems were processed using SIOSEIS (Scripps Institute of Oceanography) and Seismic Unix (Colorado School of Mines) to produce segy files and jpg images of the profiles. Data were then imported into Landmark SeisWorks, a digital seismic interpretation package, where the sea floor and underlying transgressive surface were interpreted and digitized. The isopach between these horizons was exported at every 50th shot as xyz points, and imported to ArcGIS for interpolation into a 10-m raster grid. The isopach grid was then subtracted from a seafloor bathymetry grid (bathy_grd) to approximate the proper elevation of the transgressive unconformity beneath the sea floor.

1999年，美国地质调查局（U.S. Geological Survey, USGS）与南卡罗来纳海洋赠款联盟（South Carolina Sea Grant Consortium）开展合作，启动了一项针对南卡罗来纳州北部海岸（重点覆盖大斯特兰德（Grand Strand）海岸带）的研究，旨在探究影响岸线变化的各类过程。此前针对美国大西洋沿岸的研究显示，分布于海岸向海侧的古老地质地层的结构与组成，会对沉积物供给受限区域（如大斯特兰德海岸带）的海岸动力行为产生显著调控作用。通过明确该区域的地质框架并识别沉积物的输运路径与沉积汇，地球科学家正着手构建塑造现今南卡罗来纳州海岸的现代物理过程的概念模型。本研究的核心目标包含三项：其一，对海岸高地、滨面及内陆架下方的浅层地质框架开展区域综合研究，并阐明其在海岸演化与现代海滩动力行为中的作用；其二，识别并模拟影响近海环流与沉积物输运的物理过程，明确其对现代岸线形态的塑造机制；其三，明确沉积物源区与输运路径，进而构建区域沉积物收支模型。
本数据集涵盖一幅展示长湾（Long Bay）内陆架下方区域性海侵不整合面高程的表面数据图，该区域位于南卡罗来纳州大斯特兰德海岸带近海。研究团队使用Benthos SIS-1000与Edgetech SB-512采集系统获取chirp声呐地震数据，并通过斯克里普斯海洋研究所的SIOSEIS软件与科罗拉多矿业学院的Seismic Unix（地震Unix）软件完成处理，生成了SEG-Y格式文件与剖面JPEG图像。随后将数据导入兰德马克SeisWorks数字地震解释软件，对海底面与下方的海侵界面进行解释与数字化处理。将每50炮对应的两层界面间的等厚数据以XYZ点形式导出，并导入ArcGIS地理信息系统中，插值生成10米分辨率的栅格网格。最后，将该等厚栅格与海底水深栅格（bathy_grd）进行差值运算，以近似推算海底下方海侵不整合面的真实高程。