Stratigraphic architecture and fracture-controlled dolomitization of the Cretaceous Khami and Bangestan groups: an outcrop case study, Zagros Mountains, Iran

• DOI: 10.1144/sp329.14
• Publication Date: 2010-04-01T15:35:32Z
• Authors: I. Sharp; P. Gillespie; D. Morsalnezhad; C. Taberner; R. Karpuz; J. Vergés; A. Horbury; N. Pickard; J. Garland; D. Hunt
• Keywords: Dolomitization; Outcrop

Abstract The Barremian–Aptian upper Khami Group and Albian–Campanian Bangestan have been studied at outcrop in Lurestan, SW Iran. comprises a thin deltaic wedge (Gadvan Fm) transgressively overlain by shelfal carbonates (Dariyan Fm). Dariyan Fm can be divided into lower units separated major intra-Aptian fracture-controlled karst. top of the Daryian is capped Arabian plate-wide Aptian–Albian unconformity. overlying includes Kazhdumi, Sarvak, Surgah Ilam formations. Kazhdumi represents mixed carbonate-clastic intrashelf basin succession, passes laterally (towards NE) low-angle Orbitolina- dominated muddy carbonate ramp/shoal (Mauddud Mbr). Mauddud Mbr an angular unconformity karst latest Albian–earliest Cenomanian age. Sarvak both ramp steeper dipping (5–10°) shelf/platform systems. Three regionally extensive surfaces are developed Cenomanian–Turonian interval Fm, interpreted to related flexure plate margin due initiation intra-oceanic deformation. represent clastic depositional systems respectively. Both groups affected spectacularly exposed dolomitization. Dolomite bodies 100 m several km width, plume-like geometry, with fracture (fault/joint) gradational diagenetic contacts undolomitized country rock. Sheets dolomite extend away from along steeply fault/joint zones, as strata-bound preferentially following specific depositional/diagenetic facies or stratal surfaces. There close link between primary architecture/facies secondary Vertical barriers dolomitization low permeability mudstones, below which dolomitizing fluids moved laterally. Where these cut faults corridors, observed advanced upwards, indicating that joints were fluid migration conduits. Comparisons Jurassic–Cenozoic dolomites elsewhere Iran, Palaeozoic North America Neogene Gulf Suez indicate striking textural, paragenetic outcrop-scale similarities. These data imply common process applicable regardless tectonic setting (compressional, transtensional extensional).