Sequence stratigraphic model for a Barremian-Aptian deltaic sandstone to carbonate platform transition (upper Biyadh and Sallah Formations, Central Saudi Arabia).

This study elucidates the stratigraphic relationship between Barremian and Aptian proximal, siliciclastic dominated sediments of the Biyadh and Sallah formations, and their time equivalent shallow water carbonate and intrashelf basinal sediments (Kharaib and Shuaiba formations). It fills in a gap of the established regional stratigraphic models published for this time interval. A regional subsurface stratigraphic framework (Barremian to Aptian) is constructed based on 10 wells along a 750 km long transect from central Arabia to Rub' al-Khali and Abu Dhabi (UAE). The sequence stratigraphic correlation is based on total gamma-ray logs, spectral gamma-ray (SGR) logs (uranium U and thorium Th), lithology and calcareous nannofossil analyses from well cuttings. The subsurface study is complemented with an outcrop sedimentological measured section of the time-equivalent of the Shuaiba formation, the lower Aptian Sallah formation. Three composite sequences are distinguished (Biyadh sequence, lower Shuaiba sequence and upper Shuaiba sequence) that show an overall backstepping followed by a seaward stepping of the marginal marine sandstones. The main maximum flooding surface is MFS K80, which is placed in the upper part of the lower Shuaiba sequence and is dated as early Aptian based on the presence of the nannofossil Lithraphidtes houghtonii and the ammonite Cheloniceras sp. The succession evolved from (a) a very low angle shallow-marine mixed carbonate-siliciclastic sequence (Biyadh sequence; Kharaib formations; Barremian) with limited accommodation space, to (b) an aggrading and backstepping platform with time-equivalent source rock accumulation in the adjacent (Bab) intrashelf basin, reaching maximum coastal encroachment (MFS K80) in the upper part of the carbonate platform succession, followed by regression, (lower Shuaiba sequence; lower Aptian), and (c) a lowstand wedge and basin infill with detrital argillaceous limestone (upper Shuaiba sequence). [ABSTRACT FROM AUTHOR]