Shale Tectonics: A Preface

Abstract

The phenomenon of rocks moving under their own means has always fascinated both scientists and the nonscientists. Salt is known to extrude and flow as a result of differences in density of the material and surrounding sediments. However, movement of fine-grained clastics as intrusive injectites or diapirs or as extrusive eruptive sand blows or mud volcanoes has captured the public’s imagination and given scientists the impetus to reconsider the physics of how sediments behave in the subsurface. The 2006 AAPG Hedberg Conference on Mobile Shale Basins was held in response to a need to gather industry and academic communities in a common forum to address the very existence of mobile shales. Because this question involved integrated understanding of argillokinesis from the grain scale to the basin-gravity scale, the forum attracted a broad cross section of the geoscience community. These attendees presented a wide variety of topical presentations that ranged from geochemistry of modern fluid-mud extrusions to gravity studies in basins characterized by mobile shales. An ongoing topic of debate at this forum was the very term ‘‘mobile shales.’’ The attendees decided at the meeting that this term was a misnomer and that a more appropriate term to be used to describe this phenomena was shale tectonics, thus the title of this volume. Stimulating and informative discussions at the Hedberg conference led to this special volume on shale tectonics, with contributions from researchers in industry, academia, and government covering diverse aspects of shale tectonics from grain to basin scale. In addition, to works from authors who attended the Hedberg conference, this book also contains articles from authors who did not have an opportunity to present their work at the meeting. We hope this volume presents a representative cross section of the most current research and understanding regarding shale tectonics. The volume documents shale tectonics from a variety of basins around the world, including the southern Beaufort Sea (Elsley and Tieman, 2010), the KrishnaGodavari Basin, India (Choudhuri et al., 2010), the Niger Delta (Wiener et al., 2010), eastern offshore Trinidad (De Landro Clarke, 2010), offshore Brunei (Warren et al., 2010), and along the Spanish arm of the Mediterranean Sea (Soto et al., 2010). Publication of this memoir coincides with a growing interest in shales as hydrocarbon reservoirs. Because of the burgeoning of shale gas and shale oil research, geoscientists are gaining a better understanding of the petrographic framework of shales, as well as their behavior under various pressure and temperature regimes and the manner in how fluids move thorough these strata (for a review, see Day-Stirrat et al., 2010). Advances in seismic imaging and processing technologies illuminate stratal geometries associated with shale tectonics that have led to a new understanding of the processes responsible for the geometries we observe in shale strata (see Day-Stirrat et al., 2010; Elsley and Tieman, 2010). In addition, advances in modeling and understanding of how both muds and shales behave after burial have led to new geodynamic models for interpreting process from response reflected in stratal packages (Albertz et al., 2010). Field geoscientists have added to our understanding of the geochemistry and physical character of extrusive mud features and their relationship to the overall basin hydrocarbon system (Battani et al., 2010;