A tectono-stratigraphic review of continental breakup on intraplate continental margins and its impact on resultant hydrocarbon systems

Tiago Alves,Marcos Fetter,Cathy Busby,Rogerio Gontijo,Tiago A Cunha,Nathalia H Mattos

doi:10.1016/j.marpetgeo.2020.104341

Abstract

Intraplate Continental Margins comprise fully rifted areas of continents and cratons recording the tectonic events associated with plate breakup and subsequent continental drift. In contrast to extensional basins, this tectonism post-dates the initial stages of continental rifting of tectonic plates and is specifically associated with the breakup and ‘drifting’ of continents. Seismic and outcrop data from eight (8) Intraplate Continental Margins are reviewed in this work and tectonic-subsidence models are compiled to highlight their large-scale structural and depositional variability. Specific geological aspects that enhance the hydrocarbon potential of Intraplate Continental margins include: a) syn-rift strata that are strikingly thicker, and presumed older, than previously assumed on vintage seismic profiles, b) an important control of basement type and fabric on tectonic subsidence and subsequent reactivation after continental breakup is achieved, and c) widespread extensional collapse accompanying the continental breakup process to generate a phase of important sediment bypass into relatively deeper, distal depocentres. There is evidence on seismic data that the continental breakup process per se overprints older syn-rift structures to create a complex mosaic of uplifting and subsiding basins that may not coincide in location and extent with early syn-rift depocentres. This character has the potential of generating vast amounts of reservoir strata during tectonically active periods, at the same time enhancing the influx of organic matter to basins distant from point-sources of sediment during continental breakup. As a corollary, a classification of breakup sequences is presented in this work and a new case-study from South California is developed to acknowledge the varied hydrocarbon-generating settings of Intraplate Continental Margins when continental breakup is established.

Highlights

Continental rifts formed on new cratons and tectonic plates can evolve into nascent ocean basins bordered by Intraplate Continental Margins that obey four main configurations: shelf-slope-rise, transform, embankment and halokinetic (Ingersoll, 2011; Busby and Azor, 2012)
Tectonic subsidence is one of the key parameters controlling the burial history of sedimentary basins, and the maturity of potential source rock intervals leading to oil and gas generation and expulsion (Magoon and Beaumont, 1999)
B) Crustal extension leading to continental breakup is responsible for important subsidence on ICMs which, do not become tectonically ‘passive’ in their entirety at this stage

Summary

Introduction

Continental rifts formed on new cratons and tectonic plates can evolve into nascent ocean basins bordered by Intraplate Continental Margins that obey four main configurations: shelf-slope-rise, transform, embankment and halokinetic (Ingersoll, 2011; Busby and Azor, 2012). Intraplate Continental Margins record important tectonic movements whenever older crustal structures are reactivated in association with far-field crustal stresses (Sykes, 1978; Sibson, 1994; Hand and Sandiford, 1999; Sandiford and Egholm, 2008; Holford et al, 2011; Pinet, 2016; Craddock et al, 2017). Such a tectonism post-dates the initial stages of continental rifting of tectonic plates and is associated with the breakup and ‘drifting’ of continents Magmatic events during the continental breakup and drift stages, together with regional stress ‘readjustments’, are additional phenomena capable of imposing important changes in plate motion and near-field tectonic stresses (Koptev et al, 2016; Cavazza et al, 2015)

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Conclusion