Shotpoint navigation (60 shot interval) for lines 1-5 of USGS GYRE cruise 99002 (L1_5SP.SHP)

This GIS overlay is a component of the U.S. Geological Survey, Woods Hole Science Center's, Gulf of Mexico GIS database. The Gulf of Mexico GIS database is intended to organize and display USGS held data and provide on-line (WWW) access to the data and/or metadata.

A two week cruise aboard the R/V GYRE focused on mapping surficial sedimentary processes and their connection to the subsurface geology. The study area was on the upper continental slope in the northwestern Gulf of Mexico; an area of active hydrocarbon exploration. Active salt movement, hydrocarbon movement up faults, the presence of gas hydrates associated with biogenic and thermogenic methane, and overpressured sand deposits all present hazards to oil exploration in this area. This study used sidescan sonar and high-resolution chirp subbottom profiling techniques to map the surficial and shallow subsurface expression of these processes in two areas roughly 15 by 25 km in size. High-resolution multi-channel seismic-reflection data were collected simultaneously with the sidescan imagery to provide a link to the deeper subsurface. Additional multi-channel and Huntec seismic data were collected along regional lines between the detailed study areas to tie these studies to other areas of known hydrates and to wells where shallow overpressured sands have been drilled.

The detailed studies attempted to map entire geological systems in this upper slope environment to provide a broader perspective than can be seen from studying a single lease block. One study area focused on two adjacent salt withdrawal basins to assess the processes that are shaping the flanks of the basins, the processes affecting sedimentation in the basin floors, and to compare the deeper structures and surficial processes between the basins. The second study area focused on three salt domes, the processes associated with them, and how they affect the shallow subsurface stratigraphy. Initial observations suggest that most of the surface and shallow subsurface geohazards are associated with the flanks of salt structures. Here active salt movement generates faults along which hydrocarbons can escape to the seafloor, and tectonic oversteepenning generates slope failures.

本地理信息系统叠加层（Geographic Information System overlay）隶属于美国地质调查局（U.S. Geological Survey，USGS）伍兹霍尔科学中心旗下的墨西哥湾地理信息系统数据库。该数据库旨在整理并展示美国地质调查局所持有数据，并通过万维网（World Wide Web，WWW）为用户提供数据及/或元数据的在线访问渠道。

本次研究依托“回旋号”研究船（Research Vessel GYRE，R/V GYRE）开展了为期两周的科考航次，核心目标为绘制表层沉积过程及其与地下地质的关联图谱。研究区域位于墨西哥湾西北部的大陆坡上段，该区域为油气勘探活跃区。区内活跃的盐体运动、油气沿断层运移、与生物成因及热成因甲烷伴生的天然气水合物（gas hydrates），以及超压砂体，均对该区域的油气勘探构成潜在威胁。本研究采用侧扫声呐与高分辨率chirp浅地层剖面测量技术，对两个面积约15km×25km的区域内上述过程的表层及浅层地下表现进行测绘。研究同步采集了高分辨率多道地震反射数据与侧扫影像，以建立与深层地下地质的关联。此外，研究团队还在详细研究区域之间的区域测线上采集了额外的多道地震数据及Huntec地震数据，以将本研究与已知天然气水合物分布区以及已钻探浅层超压砂体的井位区域进行衔接。

本次详细研究旨在绘制该大陆坡上段环境下的完整地质系统图谱，以获得相较于单一租赁区块研究更为全面的认知。其中一个研究区域聚焦于两个相邻的盐撤退盆地（salt withdrawal basins），旨在解析塑造盆地侧翼的地质过程、影响盆地底部沉积的作用机制，并对比两个盆地的深层构造与表层沉积过程。第二个研究区域则聚焦于三个盐丘（salt domes），以及与之相关的地质过程和其对浅层地下地层的影响。初步观测结果显示，绝大多数地表及浅层地下地质灾害均与盐构造侧翼相关：活跃的盐体运动可形成断层，为油气运移至海底提供通道；而构造过陡化则会引发斜坡失稳（滑坡）。