Tectonic evolution of the Oman Mountains: an introduction

Abstract

It is now more than 20 years since the GeologicalSociety published The Geology and Tectonics ofthe Oman Region (Robertson et al. 1990) as oneof its early special publications. That volume, the‘blue book’ as it became fondly known to multiplegenerations of undergraduates, has been a majorreference on the geology of Oman for many whowork in the region. This present volume, moremodest in its size compared to its illustrious prede-cessor, is the fruit of a conference on The Geologyof the Arabian Plate and the Oman Mountainsheld in January 2012 at Sultan Qaboos Universityin Muscat, organized by Professor Sobhi Nasirwith colleagues from Sultan Qaboos University,the Oman Government and the Geological Societyof Oman. Since the first comprehensive study ofthe geology of the Oman Mountains during thelate 1960s and early 1970s by Ken Glennie and histeam from Shell, the Oman Mountains have beenknown to contain some of the most spectacularand best-exposed geology not only in the MiddleEast but across the world. A summary of the geo-logy and the lithostratigraphy is given in Figure 1.The publications of Glennie et al. (1973, 1974),building on many earlier Shell geologists’ internalreports (notably D. M. Morton, R. H. Tschopp,H. H. Wilson, B. M. Reinhardt and M. W. Hughes-Clarke) set out the major stratigraphic frameworkfor the whole area, defined the major structuresand critically interpreted the Semail Ophiolite as athrust sheet of oceanic crust and upper mantleemplaced onto the previously passive continentalmargin of Arabia. Since the Glennie et al. (1974)memoir was published, oil companies have carriedout increasingly more intensive work comparingwell sections in the interior with the Permian–Mesozoic shelf carbonates so beautifully exposedalong numerous wadis cutting through the JebelAl-Akhdar and Saih Hatat massifs.During the late 1970s and 1980s two majorresearchteamsfromtheUSGS(ledbyBobColemanand Cliff Hopson) and the Open University, UK(led by Ian Gass, John Smewing and Steve Lip-pard) conducted detailed geological surveys acrossthe ophiolite in the Muscat–Ibra transect (USGS)and northern ophiolite (OU), respectively. Theirresults were published in a Special Issue of theJournal of Geophysical Research (volume 86,editors Coleman & Hopson 1981) and the Geologi-cal Society of London Memoir no. 11 (Lippard etal.1986). Major systematic mapping of the OmanMountains as well as the interior, Batain coast andDhofar region has been carried out by the Bureaude Recherches Ge´ologiques et Minieres (BRGM),France, the Geological Survey of Japan and theUniversity of Berne, Switzerland (see for examplePeters et al. (1991)) and the whole UAE part of thenorthern Oman Mountains was recently mapped bythe British Geological Survey (UAE Ministry ofEnergy Petroleum & Mineral Resources 2012).During the last 20 years major research groupsfrom France, Japan, USA and the UK have con-ducted research projects in the country. Detailedfield studies of the Oman Ophiolite have beencombined with geochemical and isotopic studiesto determine the tectonic setting and evolution ofthe Late Cretaceous oceanic crust and upper mantle(Boudier & Juteau 2000). Field-based studies havealso been linked to ocean drilling sites, in particularthe East Pacific rise, to compare the ophiolite toregions of active fast spreading. Key to the obduc-tion–emplacement story are the amphibolite andgreenschist facies rocks in the metamorphic solethat record an inverted metamorphic field gradientalong the base of the ophiolite. The ophiolite hasbeen the source of recent detailed studies involvingthe possible sequestration of CO