Point Shapefile of Interpreted Base of Mud Isopach Based on Seismic-Reflection Profiles Collected in Apalachicola Bay in 2006 from U.S. Geological Survey Cruise 06001 (BASEMUD_GEOG.SHP, Geographic, WGS84)

Apalachicola Bay and St. George Sound contain the largest oyster fishery in Florida, and the growth and distribution of the numerous oyster reefs here are the combined product of modern estuarine conditions and the late Holocene evolution of the bay. A suite of geophysical data and cores were collected during a cooperative study by the U.S. Geological Survey, the National Oceanic and Atmospheric Administration Coastal Services Center, and the Apalachicola National Estuarine Research Reserve to refine the geology of the bay floor as well as the bay's Holocene stratigraphy. Sidescan-sonar imagery, bathymetry, high-resolution seismic profiles, and cores show that oyster reefs occupy the crests of sandy shoals that range from 1 to 7 kilometers in length, while most of the remainder of the bay floor is covered by mud. The sandy shoals are the surficial expression of broader sand deposits associated with deltas that advanced southward into the bay between 6,400 and 4,400 years before present. The seismic and core data indicate that the extent of oyster reefs was greatest between 2,400 and 1,200 years before present and has decreased since then due to the continued input of mud to the bay by the Apalachicola River. The association of oyster reefs with the middle to late Holocene sandy delta deposits indicates that the present distribution of oyster beds is controlled in part by the geologic evolution of the estuary. For more information on the surveys involved in this project, see http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2005-001-FA and http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2006-001-FA.

阿巴拉契科拉湾（Apalachicola Bay）与圣乔治湾（St. George Sound）拥有佛罗里达州规模最大的牡蛎渔场，区内众多牡蛎礁的生长与分布，是现代河口环境与该海湾全新世晚期演化共同作用的产物。美国地质调查局（U.S. Geological Survey）、美国国家海洋和大气管理局海岸服务中心（National Oceanic and Atmospheric Administration Coastal Services Center）与阿巴拉契科拉国家河口研究保护区（Apalachicola National Estuarine Research Reserve）联合开展协同研究，采集了一系列地球物理数据与沉积物岩心（cores），旨在厘清并完善海湾底部的地质特征及其全新世地层结构。侧扫声呐（sidescan-sonar）影像、水深测量（bathymetry）数据、高分辨率地震剖面（high-resolution seismic profiles）与岩心分析结果显示，牡蛎礁分布于长度1至7千米的沙质浅滩顶部，而海湾底部的其余绝大部分区域均被泥质沉积物覆盖。这些沙质浅滩是距今6400至4400年间向南侵入海湾的三角洲相关大型砂质沉积的地表表现。地震与岩心数据表明，牡蛎礁的分布范围在距今2400至1200年间达到峰值，此后由于阿巴拉契科拉河持续向海湾输入泥质沉积物，其覆盖范围逐步缩减。牡蛎礁与中全新世至晚全新世砂质三角洲沉积的共生关系表明，当前牡蛎床的空间分布在一定程度上受控于河口的地质演化历程。如需了解本项目所涉调查的更多信息，请访问：http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2005-001-FA 与 http://woodshole.er.usgs.gov/operations/ia/public_ds_info.php?fa=2006-001-FA。