Counter-regional normal faults in shale-dominated deltas: Origin, mechanism and evolution

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• 作者：Fran?ois Sapin ; Jean-Claude Ringenbach ; Thierry Rives ; Manuel Pubellier
• 关键词：Deltaic margin ; Shale detachment ; Shale diapir ; Gravity-driven tectonics ; Counter-regional normal faults ; Fold collapse
• 刊名：Marine and Petroleum Geology
• 出版年：2012
• 出版时间：November, 2012
• 年：2012
• 卷：37
• 期：1
• 页码：121-128
• 全文大小：3040 K

文摘

The Niger and Brunei Deltas are two of the major prolific petroleum deltas of the world. As a result, large datasets of 2D and 3D seismic are available. However, some of the structures remain poorly understood because they are poorly imaged and a ¡°shale diapir interpretation¡± has often prevailed.

These two deltas are, in places, driven by particular landward structures described as ¡°counter-regional normal faults¡± (CRNF). These faults initiated on the apex of early folds, as the shelf-break propagated seaward. During a first stage of deformation, CRNF started as diffuse faults rather than localised single faults. Later, as the sediment load increased in the area affected by the CRNF, a major landward dipping fault developed, controlling the delta-front emplacement. Finally, the fault was choked by the sedimentary system and another fault (landward or seaward) developed.

The description of the pre-existing fold structures controlling the development of CRNF allows a reassessment of the structural evolution of shale gravity-driven tectonics. It is agreed that, in many cases, the existence of mud diapirs and ridges may be discarded.