Petrography and geochemistry of sandstones of the Ash Shumaysi Formation in the Jeddah-Makkah region, Saudi Arabia: Implications for provenance, tectonic setting, paleoweathering, paleoclimate and paleogeography

Abstract

This study aims to evaluate the provenance of sandstones of the Ash Shumaysi Formation (Early Eocene to Oligo-Miocene) exposed in the Jeddah-Makkah region (an intra-continental cratonic region in the west of the central part of the Arabian Shield), in addition to re-establish the tectonic setting, paleoclimate and paleo-weathering of their source rocks. This aim has been achieved by petrographic investigation and geochemical (major, trace and rare earth elements) analysis of the sandstones. Integration of both petrographic and geochemical data reflects a derivation of the sandstones from intensively-weathered and multi-recycled felsic igneous (granites) rocks, with a minor contribution of intermediate (granodiorite), mafic igneous (andesite), metamorphic (mainly gneisses) and recycled sedimentary rocks, which correspond to the Precambrian rock units of the west of the central part of the Arabian Shield. The latter was developed under semi-humid climatic conditions in the source area. Tectonically, the source rocks are of a cratonic interior in a passive continental margin of the Upper Continental Crust. This passive continental margin was later affected by rifting as revealed from the discrimination function diagrams of high-silica samples of sandstones. In general, the Ash Shumaysi sandstones may represent erosional products of the nearby high-topographic crystalline rocks of the Western Arabian Shield that were located in a tectonically stable passive margin subjected to a subsequent continental rift. Results of this study could add to the knowledge about paleoweathering, paleoclimate and tectonic setting in the Arabian Shield which is a part of the southern margin of the broad stable continental shelf of the northern margin of the Gondwana supercontinent.