Segmentation and volcano-tectonic characteristics along the SW African continental margin, South Atlantic, as derived from multichannel seismic and potential field data

Koopmann H, Franke D, Schreckenberger B, Schulz H, Hartwig A, Stollhofen H, Di Primio R (2013)

Publication Language: English

Publication Type: Journal article, Original article

Publication year: 2013

Journal

Marine and Petroleum Geology Elsevier

Publisher: Elsevier

Book Volume: 50

Pages Range: 22-39

DOI: 10.1016/j.marpetgeo.2013.10.016

Abstract

Regional seismic reflection and potential field data document the South Atlantic’s break-up history,
between 39S and 19S, from the Early Cretaceous onwards. Previous maps of distribution of volcanics
along the margin showed volcanics along the whole African margin based on extrapolation of data. Based
on previously unpublished marine geophysical data, we found the southernmost 460 km long margin
segment to be lacking huge volumes of break-up related volcanic effusives. Northwards, break-up was
accompanied by the emplacement of huge volumes of volcanic material, prominently featured in seismic
sections as huge wedge-shaped seaward dipping reflectors (SDRs). Detailed mapping of offsets (left- and
right-stepping) and variations in structural character of the volcanics reveal the segmentation along and
the break-up history of the margin. Several superimposed SDR sequences, suggesting episodicity of
volcanic emplacement (divided by periods of erosion and sedimentation), are distinct along southerly
lines, losing prominence northwards.
A main outcome of our study is that this passive margin is not continuously of the volcanic type and
that the change from a non-volcanic to a volcanic margin occurs abruptly.
We define four distinct First-order Segments along the 2400 km section of the southwestern African
margin covered by our seismic data. From south to north these First-order Segments are: Magma-poor
Segment I; Segment II with enormous SDRs volumes; decreasing SDRs volumes in Segment III; Segment
IV again with enormous volcanic output, likely influenced by Walvis Ridge volcanism.
Most important is that there is no systematic increase in the volumes of the effusives towards the
Tristan da Cunha hot-spot. Rather there is an alternating pattern in the SDRs’ volumes and widths.
The boundary between the volcanic and magma-poor margin segments in the southernmost study
area is sharp (10s of km), which we propose is reflected in magnetic anomaly data as well. We suggest
that this variability along the margin is mainly due to a change in stretching/rifting character from
oblique during the early stages of breakup to conventional seafloor spreading from Chron M4 (c. 130 Ma)
onwards.

Authors with CRIS profile

Henning Schulz Geozentrum Nordbayern Harald Stollhofen Lehrstuhl für Geologie (Exogene Dynamik)

Related research project(s)

Late Cretaceous to Recent post-breakup evolution of the African S-Atlantic margin: integrating onshore field studies; sequence development, offshore seismic data, numerical dating and modelling SPP 1375: SAMPLE: South Atlantic Margin Processes and Links with onshore Evolution Nov. 1, 2008 - Sept. 30, 2013

Involved external institutions

Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) DE Germany (DE) Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum - GFZ DE Germany (DE)

How to cite

APA:

Koopmann, H., Franke, D., Schreckenberger, B., Schulz, H., Hartwig, A., Stollhofen, H., & Di Primio, R. (2013). Segmentation and volcano-tectonic characteristics along the SW African continental margin, South Atlantic, as derived from multichannel seismic and potential field data. Marine and Petroleum Geology, 50, 22-39. https://dx.doi.org/10.1016/j.marpetgeo.2013.10.016

MLA:

Koopmann, Hannes, et al. "Segmentation and volcano-tectonic characteristics along the SW African continental margin, South Atlantic, as derived from multichannel seismic and potential field data." Marine and Petroleum Geology 50 (2013): 22-39.

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