Paleoenvironments and Organic-Rich Facies Deposition in the Tethyan Realm

Abstract

The Tethyan realm contains about 70% of the world petroleum reserves (Bois et al., 1980; Ulmishek and Klemme, 1990, among others). The major stratigraphic intervals during which the rocks that were the source of the Middle East oil and gas reserves were deposited are Jurassic and Mid-Cretaceous in age. Such a situation results from both organic sedimentation factors and global phenomena existing during this time interval (Herbin et al., 1989). In order to distinguish global causes from local effects, it is necessary to obtain a better knowledge of the spatial distribution of the organic-rich facies. A recent multidisciplinary study (Dercourt et al., 1993) provided a set of paleoenvironmental maps of the Tethyan realm, from Indonesia and Australia in the east to the Caribbean in the west. These maps attempted to reconstruct the paleogeography and the paleoenvironments of the Tethys Ocean and surrounding continents from the Late Permian to the Tortonian. Data from hundreds of publications on regional geology and stratigraphy were used in construction of every map. They are not cited here, but the interested reader is referred to the Tethys Paleoenvironmental Atlas (Dercourt et al., 1993). Each map presents (1) the present-day coastlines as a reference; (2) a paleolatitude grid; (3) 14 types of paleoenvironments, both marine and continental, selected for their depositional or bathymetric indications; and (4) the major hydrodynamic pattern.