Davie Ridge: Cretaceous Incipient Subduction Zone in the Mozambique Channel

This abstract, written by Spectrum Geoscientist Anongporn Intawong, was originally submitted for the EAGE 2019 Convention held in June 2019.

The Davie Ridge has been observed as a prominent morphological feature in the Mozambique Channel. It is characterized by a zone of N-S trending gravity low anomaly bounded to the east by gravity high anomaly striking across the continental margin of Mozambique and Madagascar. The ridge was discovered by Heirtzler and Burroughs (1971) who, upon noticing a bathymetric elevation in the Mozambique Channel, proposed that the Davie Ridge represents the expression of a transform fault resulting from the relative southward motion of Madagascar with respect to Africa. The entire feature was subsequently termed the Davie Fracture Zone by Scrutton (1978).

It has long been considered that Madagascar was first disconnected from the Kenya-Somalia part of the African continent during the Middle Late Jurassic, by dextral transform movement along the Davie Ridge (e.g. Coffin and Rabinowicz, 1987; Kusky et al., 2007), after the Gondwana breakup in the Late Liassic (Geiger et al., 2004) creating the West Somali Basin (WSB). Most of plate tectonic reconstructions have assumed an inactive transform fault of the Davie Ridge since 125 Ma based on the extinction of the spreading centre in the WSB (e.g. Coffin and Rabinowicz, 1987; Gaina et al., 2013; Reeves, 2014). The Davie Ridge was interpreted to represent either the western transform fault of the WSB (Coffin and Rabinowicz, 1987), continent-ocean transform margin (e.g. Gaina et al., 2013), or ocean-ocean transform margin (Phethean et al., 2016), in respect to the southward movement of the Madagascar-India continent in relation to Kenya-Somalia.

The Davie Ridge is also commonly interpreted as a fracture zone accommodating the southward movement of Antarctica in relation to Africa following the break-up of the Gondwana super-continent (Senkans et al., 2019; Leinweber and Jokat, 2012; Mueller and Jokat, 2017). The break-up of the African and Antarctic continents resulted in the formation of the Angoche/Mozambique Basin in the central Mozambique passive margin in the Middle Jurassic (Senkans et al., 2019), and this is based on an identification of magnetic anomaly chron M38n indicating that the first oceanic crust formed in the Angoche Basin at 164 Ma (late Collovian) (Mueller and Jokat, 2017). The break-up also resulted in the fragmentation of the Gondwana super-continent Beira High, showing a remaining pre-rift sedimentary unit on seismic sections (Senkans et al., 2019).

Understanding the origin of crustal features and geodynamic of the David Ridge and Angoche Basin is a crucial step in plate reconstruction, as well as enabling an assessment of petroleum potential, including potential source rocks and geothermal gradient estimation and its implication on source rock maturity.

 

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Davie Ridge: Cretaceous Incipient Subduction Zone in the Mozambique Channel