LITHOSTRATIGRAPHIC REVISION IN THE ARABIAN SHIELD: THE IMPACTS OF GEOCHRONOLOGY AND TECTONIC ANALYSIS

Lithostratigraphy, which describes the spatial and temporal relationships between rock units, is fundamental to an adequate understanding of geologic history. The structural complexity, great variety of rock types, large range of volcanic, sedimentary, and intrusive environments, and multiplicity of metamorphic events, make the task of lithostratigraphic analysis particularly daunting in the Arabian shield. It is an ongoing process that advances in degrees of refinement and reliability in concert with advances in information about the origins and formation ages of the rocks and about their subsequent structural and metamorphic modifications. Robust geochronology and an understanding of the tectonic setting of the rocks are fundamental to this process. As reported here, advances in high-precision, singlegrain zircon U–Pb dating yield greatly improved precision in crystallization ages and have led to a better knowledge of the formation ages of volcanic assemblages, the intrusive ages of plutonic suites, and the maximum deposition ages of sedimentary units. Accepting that the shield consists of amalgamated terranes and intervening suture zones requires a limitation of where in the shield to apply particular formation and group names, the renaming of certain formations and groups, and the revision of lithostratigraphies for several regions. As a result, earlier lithostratigraphic models have been changed and new lithostratigaphic relationships and names are proposed.