Geodetic constraints on cratonic microplates and broad strain during rifting of thick Southern African lithosphere

Luke N J Wedmore, Juliet J Biggs, Michael Floyd, Åke Fagereng, H. Mdala, Patrick Chindandali, Jack N Williams, Felix Mphepo

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Southern Africa is typically considered to belong to a single tectonic plate, Nubia, despite active faulting along the southwestern branch of the East African Rift System. We analyse regional GNSS measurements, and find that the ‘San’ microplate, situated south of the southwestern branch of the East African Rift, is statistically distinct from Nubia, with 0.4-0.7 mm/yr of extension across the boundary. Adding 9 new campaign GNSS sites, we show that the extension rate across the southern Malawi Rift is 2.2 ± 0.3 mm/yr, with 75% of the relative velocity occurring over 890 km, despite the surface expression of faulting being <150 km wide. Thus, for the first time, we use geodetic measurements to describe the accommodation of strain in broad zones between Archean cratons in southern Africa’s thick continental lithosphere.
Original languageEnglish
Article numbere2021GL093785
JournalGeophysical Research Letters
Volume48
Issue number17
Early online date6 Aug 2021
DOIs
Publication statusPublished - 16 Sep 2021

Bibliographical note

Funding Information:
The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the “Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa” grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR‐1724794.

Funding Information:
The authors thank Kondwani Dombola, Denson Makwela, and Jalf Salima at the Geological Survey Department, Malawi for making this work possible. The authors also thank the district governors, drivers, schoolteachers, doctors, national park wardens, and guards in Malawi for assistance with the GPS deployment. We thank Ophelia George for her assistance in uploading the GNSS data to Unavco. The authors thank the Cindy Ebinger, two other reviewers, and the associate editor for careful and detailed comments that significantly improved this manuscript. This work was funded by a number of EPSRC grants funded under the Global Challenges Research Fund (GCRF): PREPARE (EP/P028233/1); SAFER PREPARED (part of the ?Innovative data services for aquaculture, seismic resilience, and drought adaptation in East Africa? grant; EP/T015462/1); and a GCRF EPSRC Institutional Sponsorship Award. The authors also received a fieldwork grant from COMET, the NERC Centre for the Observation and Modeling of Earthquakes, Volcanoes, and Tectonics, a partnership between UK Universities and the British Geological Survey. This material is based on services provided by the GAGE Facility, operated by UNAVCO, Inc., with the support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794.

Publisher Copyright:
© 2021. The Authors.

Keywords

  • GNSS
  • plate tectonics
  • Africa
  • geodesy
  • strain
  • rift

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