Crustal Architecture and Nature of Continental Breakup Along a Transform Margin: New Insights From Tanzania‐Mozambique Margin

Abstract

The Tanzania‐North Mozambique continental margin is a transform segment associated with Davie Fracture Zone (DFZ). The DFZ is described as an elongated linear oceanic fracture zone, commonly linked with the breakup between Eastern and Western Gondwana. We conducted a synthesized study using gravity, magnetic, and seismic data presenting the crustal architecture, geometry, and the kinematic nature of continental breakup along a transform margin. The crustal nature of DFZ, its role in forming kinematic linkage between two extensional margins during continental breakup processes, is focus of our study. The two extensional margins, Somalia‐Majunga and North Mozambique‐Antarctica, were linked via a 2,600‐km‐long dextral transform segment, partially overlapping with DFZ. Absence of classical rift indicators, weak signs of hyperextension, and abrupt ocean‐continent boundary suggest transform margin architecture. We redefined this feature as the Davie Transform System. The nature of deformation varies from transtensional pull‐apart in Tanzania to almost pure strike slip in North Mozambique. The southern transform segment exhibits abrupt change in ocean continent transition with a narrow zone of continental extension. This variation is recognized through the newly interpreted ocean‐continent boundary along this entire transform segment. Notably, within large pull‐apart systems in the north, the presence of fossilized incipient spreading center suggests that the extension had reached at quite advanced stages, characterized by significant thermal weakening as a consequence of strong magmatic activity. Through a series of reconstruction snapshots, we show the geodynamic evolution along the Tanzania‐North Mozambique margin explaining the role of Davie Transform System in the southward movement of Madagascar.

The Davie Fracture Zone: A recorder of continents drifts and kinematic changes

“…So far, several works based on these data have been published (e.g., Attoh et al, 2004;Dailly et al, 2013;Mahanjane, 2014;Mahanjane et al, 2014;Nemčok et al, 2016b;Klimke et al, 2018;Sauter et al, 2018;Baby et al, 2018;Sinha et al, 2019). They showed different structures and evolutions suggesting a considerable degree of variability.…”

“…Recent synthesis (e.g., Lepinay et al, 2016;Loncke et al 2020) highlighted also common characteristics of transform margins such as steep continental slopes, marginal ridges along the edge of the continental slope, and marginal plateaus systematically located between the platform and the lower continental slope. But these criteria are not systematic, suggesting that key parameters, such as lithospheric inherited heterogeneities and thermal state, may strongly influence the dynamics of their formation (e.g., Sinha et al, 2019).…”

Reclus, a New Database for Investigating the Tectonics of the Earth: An Example From the East African Margin and Hinterland

“…Although we show this zone of mixed magmatic crust with an inferred ridge continuing the trend of that in the West Somali Basin, based on the juxtaposition of mapped features, we accept that the hypothesis of Sinha et al. (2019) is a viable alternative and that this zone may be part of an earlier incipent ocean, related to the Phase 1 rifting of Tuck‐Martin et al. (2018, discussed below).…”

Crustal variability along the rifted/sheared East African margin: a review

“…3 (182 Ma)) (Leitchenkov et al 2008). Northern Madagascar fits close to the Somali and Kenyan shores (Leinweber and Jokat 2012;Davis et al 2016;Phethean et al 2016;Reeves 2018;Tuck-Martin et al 2018;Müller and Jokat 2019;Sinha et al 2019).…”

“…Madagascar, whilst still connected to India, reached its final position with respect to Africa at some point in Early Cretaceous times (M9n-M1n, Eagles and König 2008;Davis et al 2016;Tuck-Martin et al 2018;Müller and Jokat 2019). The latter movement created a large fracture zone and/or transform system in the Somali Basin and the Mozambique Channel, known as the Davie Fracture Zone (DFZ) or Davie Transform System (DTS) (Bunce and Molnar 1977;Davis et al 2016;Sinha et al 2019).…”