Tectonic history along the South Gabon Basin: Anomalous early post-rift subsidence

Abstract

An integrated study of the South Gabon Margin (South Atlantic) based on reflection seismic and well data has been performed to quantify tectonic activity. A regional profile crossing the entire basin together with subsidence analysis, highlights important aspects of the post-rift history. The most striking event in the margin evolution appears to be the anomalous extra subsidence during the early postrift period characterized by high sedimentation rates, equivalent to one third of the syn-rift subsidence. Although the presence of evaporite layers restricts knowledge of the underlying structures essentially composed of pre-rift and syn-rift sequences, the outcome of this post-rift tectonic study has strong implications for the rifting history. The early post-rift subsidence patterns can be related to a high thermal anomaly during the early rifting thermal state of the lithosphere. These findings are highly relevant for petroleum system studies and have implications for hydrocarbon generation. r

Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust

“…This nearby analogy reinforces our perception that the lower part of the Gabon rifted margin behaves in a ductile way. The observed weakness of the base of the crust is possibly explained by a positive thermal anomaly during rifting suggested by Dupré et al, (2007;. The origin of this thermal anomaly is still poorly constrained, but we suggest a potential effect of the sediment thickness.…”

Coupled onshore erosion and offshore sediment loading as causes of lower crust flow on the margins of South China Sea

“…I anticipate that this process is not limited to basins around the South China Sea and has been recognized in the Gulf of Thailand (Morley and Westaway 2006) and likely in other regions of post-rift subsidence anomalies that have not yet been identified, or have not yet been satisfactorily explained, e.g. Paleozoic passive margin of West North America (Levy and Christie-Blick 1991), the early postrift offshore Gabon, West Africa (Dupré et al 2007), and the Gulf of Lions, Mediterranean Sea (Burrus et al 1987). …”

Tectonic Models for the Evolution of Sedimentary Basins

“…On these basins, the petroleum industry has acquired large databases that document their structural styles and allow detailed reconstruction of their evolution. Academic research programs have provided information on the crustal and lithospheric configuration of tectonically active rifts, paleorifts, and passive margins (e.g., Abadi et al, 2008;Beglinger et al, 2012a,b,c,d;Corver et al, 2009Corver et al, , 2011Dupré et al, 2007Dupré et al, , 2011. Petrologic and geochemical studies have advanced the understanding of rift-related magmatic processes.…”

“…It appears that in many areas, the postrift evolution is characterized by initial rift-related subsidence, sometimes followed by accelerated subsidence of the central parts of an extensional sedimentary basin, simultaneously occurring with broad uplift in adjacent areas flanking the depocenter. Examples can be found in the Atlantic margin of Morocco (Ghorbal et al, 2008;Gouiza et al, 2010), the southern Atlantic rifted margins (Beglinger et al, 2012a,b,c,d;Dupré et al, 2007Dupré et al, , 2011, and the Sirte Basin in Libya (Abadi et al, 2008).…”