Late Miocene Mega Slumping along the southwest African Coast


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Estella.Weigelt [ at ] awi.de

Abstract

Large Neogene slumps affected the sedimentary sequence on the southwest African margin. Based on an integrated study of borehole and seismic data we aim to generate a spatial and chronological classification of slump scarp traces to gain an understanding of the origin of these mass-movements. In our contribution, we focus on an extended slump scarp zone identifiable on all seismic lines available to us along the eastern Cape Basin. This large slumping feature is located at the upper slope region of the continental margin and dated to originate in the Middle/Late Miocene (15-10 Ma ).In the northern Cape Basin, we defined a lower age of about 10 Ma for this slumping scarp zone which is also acossiated with a sudden change in reflection pattern of seismic units above and below. In contrast, only weak traces of slump scarps can be distinguished in the Middle Cape Basin. Probably they are masked by a reflection free zone indicating the presence of gas and hydrocarbons. Again, in the southern Cape Basin we have observed slumping scarps throughout the upper seismic units since the Late Miocene. As possible preconditions for laterally extended mass movement we suggest (1) either a high instability of deposited material resulting of an increased sedimentation in response to enhanced upwelling since the Middle Miocene or (2) instabilities due to gas hydrates. A strong Middle/Late Miocene sea level regression later probably triggered contemporaneously slumping and sliding.



Item Type
Conference (Poster)
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Not peer-reviewed
Publication Status
Published
Event Details
IODP-Kolloquium 2008, 12. - 14. Apr., Hannover..
Eprint ID
18483
Cite as
Weigelt, E. and Uenzelmann-Neben, G. (2008): Late Miocene Mega Slumping along the southwest African Coast , IODP-Kolloquium 2008, 12. - 14. Apr., Hannover. .


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