Tectonic Settings of Continental Extensional Provinces and their Impact on Sedimentation and Hydrocarbon Prospectivity
Chris K. Morley, 2002. "Tectonic Settings of Continental Extensional Provinces and their Impact on Sedimentation and Hydrocarbon Prospectivity", Sedimentation in Continental Rifts, Robin W. Renaut, Gail M. Ashley
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Extensional basins can be classified according to plate-tectonic setting and driving mechanism into: (1) regional continental extension, (2) extension at the tips of permanently or temporarily abandoned spreading centers, (3) in the upper plate of volcanic arc-oceanic crust subduction zones, (4) soft collision zones, (5) post-orogenic wide rifts (Cordilleran type), (6) Himalayan-type extension; and (7) in response to far-field orogenic stresses. These settings display differences in mantle geometry, volcanic history, fault geometry and evolution, generation of lithospheric thermal anomalies, rift topography, post-rift history, sediment source characteristics, sediment pathways, and timing and intensity of inversion tectonics, which can impact hydrocarbon prospectivity. In convergent settings subduction rollback and slab-suction forces are very important mechanisms for generating extension, creating the conditions for non-uniform lithospheric thinning, and very characteristic thick (4-6 km), rapidly formed (10-15 Myr) thermal subsidence basins. The enhanced gravity potential of overthickened crust appears to be an important driving mechanism for extension in orogenic belts, but it is usually accompanied by other mechanisms (escape tectonics, subduction rollback, propagating spreading centers) for extension to occur.
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Sedimentation in Continental Rifts
Continental rift basins have long been of interest to sedimentologists. Of all the terrestrial settings, rift basins typically provide the greatest accommodation space, and consequently have some of the longest records of continental sedimentation. These records are a product of a complex interplay between several factors that include geological structure and tectonic activity, volcanism, climate and its temporal variability, hydrology, biology and time. Sedimentation in Continental Rifts is a timely update on this exciting interdisciplinary field and presents new approaches and insights into tectonic and structural controls of sedimentation. Other topics included are lacustrine and fluviatile depositional environments and some lesser-known settings, such as springs, wetlands, and paleosols. Several papers consider the behavior of silica in rift lakes, particularly the roles of microorganisms in silica precipitation, whereas others examine the paleoenvironmental importance of freshwater carbonates. The contents of the volume show that sedimentological research in rift basins has progressed beyond basic facies description and general models, and is now focused on understanding the integrative effects of physical, chemical and biological processes in rifts.