Sequence stratigraphic controls on early-diagenetic carbonate cementation of shallow marine clastic sediments (the Devonian Zakeen Formation, southern Zagros, Iran)

摘要

Distribution pattern of carbonate cements of the Middle to Upper Devonian Zakeen Formation of southern Zagros, suggests a close relationship between relative sea-level changes and diagenetic processes. Ferroan dolomite cementation is closely linked to genetically related facies (parasequences, systems tracts, sequences) and/or major stratal surfaces (transgressive and maximum flooding surfaces and sequence boundaries). The cements are systematically distributed within the lowstand, transgressive and highstand systems tracts. Eogenetic ferroan dolomite cement (δ18O from 1.06 to ?6.00‰ VPDB and δ13C from ?1.23 to ?4.94‰ VPDB) was developed in the form of: 1) ferroan dolomite cemented conglomerates in LST estuarine environments, 2) laterally extensive ferroan dolomite cemented sandstones in LST estuarine and TST foreshore-shoreface environments and along maximum flooding surfaces and 3) ferroan dolomite cemented nodules in LST, TST and HST foreshore-shoreface environments. Prolonged subaerial exposure of the strata, resulted from epeirogenetic movements of the Hercynian Orogeny, is considered to be responsible for cement and grains leaching and porosity development in sandstones underlying the major sequence boundary at the top of the Zakeen Formation.