Reporting in the journal Nature, scientists from Royal Holloway, University of London and the Institut de Ciencies del Mar (Spanish Research Council) have revealed a new model that explains how continents thin as well as helping to more accurately predict the location of hydrocarbons such as oil and gas.
For oil to be formed, sediments need to be deposited under the right temperatures. "When continents extend, the top of the crust subsides and deepens, creating a space for sediments which may convert into oil," explains Dr Marta Pérez-Gussinyé from Royal Holloway. "Our model presents a conceptual framework to predict more accurately the temperature conditions through which sediments go, therefore helping in the search for oil and gas."
Geologists have long debated the paradoxes arising from their understandings of how continents break apart and drift forming new oceans. Many continents, such as Africa, parts of South and North America, Europe, Asia and Australia, are surrounded by rifted margins, which are the stretched areas where the geological processes of rifting and break-up are recorded.
The new model is based on high resolution images of the tectonic structure of the crust at such margins. These images are obtained using elaborate seismic methods which give a picture of the crust below the oceans, showing where faults and sediments are.
It was previously believed that as the Earth's plates drifted away from each other the rocks in the stretched area broke up by faulting all at the same time. The new concept is that, in fact, the faults form one after another in this region as the crust thins. As the faults are forming, sediments are deposited and the youngest ones are found closest to the new oceans that eventually form.
This model has important implications for the formation of hydrocarbon resources, the style of faulting during continental thinning, sediment deposition and potentially for the opening of oceanic gateways and oceanic circulation.
- César R. Ranero, Marta Pérez-Gussinyé. Sequential faulting explains the asymmetry and extension discrepancy of conjugate margins. Nature, 2010; DOI: 10.1038/nature09520
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