Sinuous pockmark belt as indicator of a shallow buried turbiditic channel on the lower slope of the Congo basin, West African margin

Author:

Gay A.12,Lopez M.2,Cochonat P.3,Sultan N.3,Cauquil E.4,Brigaud F.4

Affiliation:

1. Université de Lille I, Laboratoire Sédimentologie et Géodynamique FRE 2255, Bât SN5, 59655 Villeneuve d’Ascq, France

2. Université de Montpellier II, Laboratoire Géophysique Tectonique et Sédimentologie CC60, Bât 22, place E. Bataillon, 34095 Montpellier cedex, France gay@elstu-univ-montp2.fr

3. IFREMER, Institut Français de Recherche et d’Exploitation de la MER, Département Géosciences Marines, Laboratoire Environnements Sédimentaires BP70, 29280 Plouzané, France

4. Total-Fina-Elf 64018 Pau Cedex, France

Abstract

AbstractPockmarks on the slope of the Lower Congo Basin are distributed along a meandering band on seafloor coincident with a shallow buried palaeochannel imaged from the 3D-seismic database. Each pockmark originates systematically at the channel-levee interface and the seafloor expression of the palaeochannel’s sinuosity is mimicked by the sinuous trend of pockmarks. 3D-seismic on the slope, calibrated by biostratigraphic data from cores of the Leg ODP 175, indicate a seaward decrease of the sedimentation rate. We suggest that this condition induces a differential loading of the hemipelagic cover over the palaeochannel and propose a model for episodic dewatering of fluids trapped in the buried turbiditic channel. The consequence is a fluid flow caused by a longitudinal pressure gradient along the buried channel. A hydromechanical model proposed for the formation of shallow pockmarks indicates that the sedimentation rate cannot generate the overpressure required for pockmark formation on the seafloor. Therefore, it is suggested that hydrocarbon migration from deeper overpressured reservoirs is added to the pore fluid pressure in the shallow subsurface sediments. Horizontal drainage by the turbiditic palaeochannel and vertical migration along many vertical conduits (seismic chimneys) probably initiated at shallow subbottom depth. It is concluded that these shallow processes have important implications for fluid migration from deeply buried hydrocarbon reservoirs.

Publisher

Geological Society of London

Subject

Geology,Ocean Engineering,Water Science and Technology

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3