Preprints
https://doi.org/10.5194/egusphere-2022-708
https://doi.org/10.5194/egusphere-2022-708
15 Aug 2022
 | 15 Aug 2022

Formation and geophysical character of transitional crust at the passive continental margin around Walvis Ridge, Namibia

Gesa Franz, Marion Jegen, Max Moorkamp, Christian Berndt, and Wolfgang Rabbel

Abstract. When interpreting geophysical models, we need to establish a link between the models’ physical parameters and geological units. To define these connections, it is crucial to consider and compare geophysical models with multiple, independent parameters. Particularly in complex geological scenarios, such as the rifted passive margin offshore Namibia, multi-parameter analysis and joint inversion are key techniques for comprehensive geological inferences. The models resulting from joint inversion enable the definition of specific parameter combinations, which can then be ascribed to geological units. Here we perform a user-unbiased clustering analysis of the parameters electrical resistivity and density from two models derived in a joint inversion along the Namibian passive margin. We link the resulting parameter combinations to break-up related lithology, and infer the history of margin formation. This analysis enables us to clearly differentiate two types of sediment cover. Namely, one of near-shore, thick, clastic sediments, and a second one of further offshore located, more biogenic, marine sediments. Furthermore, we clearly identify areas of interlayered massive, and weathered volcanic flows, which are usually only identified in reflection seismic studies as seaward dipping reflectors. Lastly, we find a distinct difference in the signature of the transitional crust south of- and along the supposed hot-spot track Walvis Ridge. We ascribe this contrast to an increase in magmatic activity above the volcanic centre along Walvis Ridge, and potentially a change in melt sources or depth of melting. This characterizes a rift-related southern complex, and a plume-driven Walvis Ridge regime. All of these observations demonstrate the importance of multi-parameter geophysical analysis for large-scale geological interpretations. Furthermore, our results may improve future joint inversions using direct parameter coupling, by providing a guideline for the complex passive margins parameter correlations.

Journal article(s) based on this preprint

06 Mar 2023
Formation and geophysical character of transitional crust at the passive continental margin around Walvis Ridge, Namibia
Gesa Franz, Marion Jegen, Max Moorkamp, Christian Berndt, and Wolfgang Rabbel
Solid Earth, 14, 237–259, https://doi.org/10.5194/se-14-237-2023,https://doi.org/10.5194/se-14-237-2023, 2023
Short summary

Gesa Franz et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-708', Anonymous Referee #1, 07 Nov 2022
    • AC1: 'Reply on RC1', Gesa Franz, 05 Jan 2023
  • RC2: 'Comment on egusphere-2022-708', Anonymous Referee #2, 12 Dec 2022
    • AC2: 'Reply on RC2', Gesa Franz, 05 Jan 2023
  • RC3: 'Comment on egusphere-2022-708', Anonymous Referee #3, 22 Dec 2022
    • AC3: 'Reply on RC3', Gesa Franz, 05 Jan 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-708', Anonymous Referee #1, 07 Nov 2022
    • AC1: 'Reply on RC1', Gesa Franz, 05 Jan 2023
  • RC2: 'Comment on egusphere-2022-708', Anonymous Referee #2, 12 Dec 2022
    • AC2: 'Reply on RC2', Gesa Franz, 05 Jan 2023
  • RC3: 'Comment on egusphere-2022-708', Anonymous Referee #3, 22 Dec 2022
    • AC3: 'Reply on RC3', Gesa Franz, 05 Jan 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Gesa Franz on behalf of the Authors (05 Jan 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (09 Jan 2023) by Ulrike Werban
RR by Anonymous Referee #3 (19 Jan 2023)
RR by Majid Khan (24 Jan 2023)
ED: Publish subject to minor revisions (review by editor) (25 Jan 2023) by Ulrike Werban
AR by Gesa Franz on behalf of the Authors (01 Feb 2023)  Author's response   Author's tracked changes   Manuscript 
EF by Lisa Appel (02 Feb 2023)  Manuscript 
ED: Publish as is (06 Feb 2023) by Ulrike Werban
ED: Publish as is (06 Feb 2023) by CharLotte Krawczyk (Executive editor)
AR by Gesa Franz on behalf of the Authors (07 Feb 2023)

Journal article(s) based on this preprint

06 Mar 2023
Formation and geophysical character of transitional crust at the passive continental margin around Walvis Ridge, Namibia
Gesa Franz, Marion Jegen, Max Moorkamp, Christian Berndt, and Wolfgang Rabbel
Solid Earth, 14, 237–259, https://doi.org/10.5194/se-14-237-2023,https://doi.org/10.5194/se-14-237-2023, 2023
Short summary

Gesa Franz et al.

Gesa Franz et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
Our study focuses on the correlation of two geophysical parameters (electrical resistivity and density) with geological units. We use this computer-aided correlation to improve interpretation of the Earth’s formation history along the Namibian coast and the associated formation of the South Atlantic ocean. It helps to distinguish different types of sediment cover and varieties of oceanic crust, as well as to identify typical features associated with the breaking-apart of continents.