Pockmark Occurrence in the Northern Gulf of Mexico Influenced by Glacial Cycles and Hydrate Stability

IF 2.9 2区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
A. Kumar, A. E. Cook, M. A. Lawal, A. Portnov, V. Lecours
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Abstract

On the continental slope of the northern Gulf of Mexico, pockmarks concentrate near the estimated updip edge of the hydrate stability zone (HSZ). We identified 5,691 pockmarks in the northern Gulf of Mexico by combining existing records with manually mapped pockmarks from bathymetric data. Nearly 70 percent of the pockmarks occur within 330–600 m water depth and the number of pockmarks drops abruptly at water depths >600 m. Based on hydrate stability modeling, we argue that the updip edge of the HSZ shifted downslope since the last glacial maximum. This downslope shift caused hydrate dissociation and released charged free gas resulting in pockmark formation on the seafloor. Moreover, we observe that fluctuations in the updip edge of the HSZ since the last glacial maximum (from 330 to 605 m water depth) coincide with increased pockmark abundance. On other continental margins, pockmarks have been observed within a similar water depth range, suggesting that the loss of hydrate stability during deglaciation is a worldwide phenomenon that created intense fluid emission from the seafloor.

Abstract Image

冰期旋回与水合物稳定性对墨西哥湾北部麻坑分布的影响
在墨西哥湾北部的大陆斜坡上,麻点集中在水合物稳定带(HSZ)的估计上倾边缘附近。通过将现有记录与水深数据手工绘制的麻点相结合,我们在墨西哥湾北部确定了5691个麻点。近70%的麻点发生在水深330 ~ 600 m范围内,水深600 m时麻点数量急剧下降。基于水合物稳定性模型,我们认为自末次极大期以来,青藏高原的上倾边缘发生了下坡移动。这种下坡移动导致水合物解离并释放出带电的自由气体,从而在海底形成麻点。此外,我们观察到,自末次盛冰期以来(从330至605 m水深),HSZ上倾角边缘的波动与麻子丰度的增加相吻合。在其他大陆边缘,在类似的水深范围内也观察到麻坑,这表明在冰川消融期间水合物稳定性的丧失是一种世界范围的现象,造成了海底强烈的流体排放。
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来源期刊
Geochemistry Geophysics Geosystems
Geochemistry Geophysics Geosystems 地学-地球化学与地球物理
CiteScore
5.90
自引率
11.40%
发文量
252
审稿时长
1 months
期刊介绍: Geochemistry, Geophysics, Geosystems (G3) publishes research papers on Earth and planetary processes with a focus on understanding the Earth as a system. Observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, biosphere, and solar system at all spatial and temporal scales are welcome. Articles should be of broad interest, and interdisciplinary approaches are encouraged. Areas of interest for this peer-reviewed journal include, but are not limited to: The physics and chemistry of the Earth, including its structure, composition, physical properties, dynamics, and evolution Principles and applications of geochemical proxies to studies of Earth history The physical properties, composition, and temporal evolution of the Earth''s major reservoirs and the coupling between them The dynamics of geochemical and biogeochemical cycles at all spatial and temporal scales Physical and cosmochemical constraints on the composition, origin, and evolution of the Earth and other terrestrial planets The chemistry and physics of solar system materials that are relevant to the formation, evolution, and current state of the Earth and the planets Advances in modeling, observation, and experimentation that are of widespread interest in the geosciences.
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