Holocene sedimentology and stratigraphy of coastal sediments in an arid climate, Al Qahmah, southern Red Sea, Saudi Arabia

Holocene sedimentary deposits in Al Qahmah coast, southern Red Sea, in Saudi Arabia have been accumulated on an arid siliciclastic coast in a rift tectonic setting. This study provides a detail interpretation and analysis of sedimentary facies, stratigraphy, depositional environment, and major geological processes. Two studies have been undertaken. First, petrological study of composition and texture of modern sediments and facies mapping delineate facies distribution and mechanisms of sediment transport and deposition. A unique suite of complex riverine, wave, tidal, wind, and chemical and biological processes affect the composition, texture, and distribution of the facies. Second, the depositional environments of the Holocene deposits were interpreted on the basis of detailed lithofacies analysis and lithostratigraphic correlation, along with absolute age dating, using subsurface trenching and seismic refraction tomography (SRT) and electrical resistivity tomography (ERT) methods. Two major facies, underlying carbonate and overlying siliciclastic facies, were delineated. The carbonate facies are interpreted as shallow normal marine deposits. The siliciclastic facies are marginal marine and nonmarine coastal deposits. A disconformity and an erosional unconformity are identified, across which significant changes in tectonic and climatic conditions had occurred. This study presents a detailed sedimentologic, stratigraphic, environmental, and paleoclimatic reconstruction in modern and recent arid siliciclastic coast in a rift tectonic setting.