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Megaslides, Source Rocks and Mantle Convection

2017, Proceedings

“Megaslides, source rocks, and mantle convection” Karyna Rodriguez, Director of Geoscience, Spectrum Geoscience 26th March 2018 – 5pm – 6pm Abstract A simple play model for the exploration of deepwater basin floor fans along the Atlantic margin is proposed. One aspect of this play is the identification of source rock on seismic. Seismic characterization is one route, and another is to look for behaviors of clastic sequences loading source rocks that might indicate the presence of maturing organic material. It has been proposed that one such is the development of gravity controlled fold and thrust systems or “megaslides” (examples from Orange River, Namibia and Juba Lamu Basin, Somalia). Yet similar clastic sequences in other basins have not developed these features. Mechanisms for megaslide formation, and indeed the controls on post-rift passive margin clastic stability in general will be discussed and a model for control by dynamic topography introduced. A global model related to mantle convection (Hoggard et al 2016) is discussed. We explore the consequence of this for the stability of clastic sequences in passive margin basins, developing the idea to provide alternative insight on a number of geologic phenomena familiar on passive margins basin unique unconformities, crust architecture on passive margins, conjugate asymmetry, magmacity of rift processes and consequential SDR characteristics are discussed in the context of this model. The mechanism of plate tectonic processes and measurement of global sea level curves are challenged by this model. We propose that the basin specific control on subsidence that determines clastic prism stability on passive margins can be mapped on a global reference framework back through such that basin histories on passive margins from rift-inception to the present day can be understood in a simple coherent framework. This gives an opportunity for a new understanding of hydrocarbon potential of passive margins to be developed. Reference M.J. Hoggard, N. White and D. Al-Attar. Global dynamic topography observations reveal influence of large scale mantle flow. Nature Geoscience, published online May 2016 (DOI 10.10.38/NGEO2709).