Structural Analysis of the Western Afar Margin, East Africa: Evidence for Multiphase Rotational Rifting

Zwaan, F.; Corti, G.; Sani, F.; Keir, D.; Muluneh, A. A.; Illsley-Kemp, F.; Papini, M. (2020). Structural Analysis of the Western Afar Margin, East Africa: Evidence for Multiphase Rotational Rifting. Tectonics, 39(7) American Geophysical Union, European Geophysical Society 10.1029/2019TC006043

[img] Text
Zwaan_etal_2020_Tectonics.pdf - Published Version
Restricted to registered users only until 19 December 2020.
Available under License Publisher holds Copyright.

Download (2MB) | Request a copy
[img]
Preview
Text
Zwaan et al_Tectonics_in press.pdf - Accepted Version
Available under License Publisher holds Copyright.

Download (9MB) | Preview

The Afar region in East Africa represents a key location to study continental breakup. We present an integrated structural analysis of the Western Afar Margin (WAM) aiming to better understand rifted margin development and the role of plate rotation during rifting. New structural information from remote sensing, fieldwork, and earthquake data sets reveals that the N‐S striking WAM is still actively deforming and is characterized by NNW‐SSE normal faulting as well as a series of marginal grabens. Seismicity distribution analysis and the first‐ever borehole‐calibrated sections of this developing passive margin show recent slip concentrated along antithetic faults. Tectonic stress parameters derived from earthquake focal mechanisms reveal different extension directions along the WAM (82°N), in Afar (66°N) and in the Main Ethiopian Rift (108°N). Fault slip analysis along the WAM yields the same extension direction. Combined with GPS data, this shows that current tectonics in Afar is dominated by the local rotation of the Danakil Block, considered to have occurred since 11 Ma. Earlier stages of Afar development (since 31–25 Ma) were most likely related to the large‐scale rotation of the Arabian plate. Various authors have proposed scenarios for the evolution of the WAM. Any complete model should consider, among other factors, the multiphase tectonic history and antithetic fault activity of the margin. The findings of this study are not only relevant for a better understanding of the WAM but also provide insights into the role of multiphase rotational extension during rifting and passive margin formation in general.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Exogenous Geology
08 Faculty of Science > Institute of Geological Sciences > Tectonics

UniBE Contributor:

Zwaan, Frank

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0278-7407

Publisher:

American Geophysical Union, European Geophysical Society

Funders:

[4] Swiss National Science Foundation
[UNSPECIFIED] Università di Firenze
[UNSPECIFIED] Ministero Università e Ricerca
[UNSPECIFIED] New Zealand Ministry of Business Innovation and Employment

Projects:

[UNSPECIFIED] The breaking up of continents: the Western Afar Margin as a case study

Language:

English

Submitter:

Frank Zwaan

Date Deposited:

16 Jul 2020 15:14

Last Modified:

28 Jul 2020 06:29

Publisher DOI:

10.1029/2019TC006043

Uncontrolled Keywords:

Rifting, continental break-up, Afar, Oblique extension, marginal flexure, fieldwork, seismicity, earthquakes,

BORIS DOI:

10.7892/boris.145229

URI:

https://boris.unibe.ch/id/eprint/145229

Actions (login required)

Edit item Edit item
Provide Feedback