Cyclostratigraphy across a Mississippian carbonate ramp in the Esfahan–Sirjan Basin, Iran: implications for the amplitudes and frequencies of sea-level fluctuations along the southern margin of the Paleotethys

Palaeoenvironment, palaeogeography, and palaeoclimatology of the Mississippian carbonate ramp in the Alborz tectonostratigraphic zone: Implications for deciphering the controlling factors on ramp evolution

“…Towards the top of the succession, a significant reduction of heterolithic bedsets or muddy beds, the presence of thick, amalgamated beds displaying HCS and coarser grain‐size along with the characteristic ichnologic features, all indicate the high‐energy and progressive sorting linked with continuous and intense wave/current reworking in a high‐energy setting of the proximal middle ramp. The grain‐supported microfacies with greater homogeneity than the previous sequence, peloids, disarticulation/fragmentation, and the erosion of crinoid columnals and brachiopod shells in thick calcareous layers with small amounts of carbonate mud and reduced biological turbulence, most probably suggest multiple reworking by successive hydrodynamic events (Bayet‐Goll et al, 2014, 2018; Palma, López‐Gómez, & Piethé, 2007; Sharafi, Rodríguez‐Tovar, Bayet‐Goll, et al, 2021). Expanded storm deposits in the proximal middle ramp of this sequence, with dominant echinoderm‐bioclastic grainstones and packstones and stormy sedimentary structures, are typical evidence of proximal tempestites.…”

“…However, palaeoenvironmental studies of Carboniferous sediments of the tectonic blocks in Iran (Alborz, Kopeh-Dagh, and Central Iran) have rarely been considered, and there are still many ambiguities regarding Carboniferous tectono-depositional processes in the southern margin of the Palaeotethys Ocean. Basically, according to Bayet-Goll et al (2018), the geological history of the southern Palaeo-Tethyan platforms, including the tectonic blocks of the Late Palaeozoic in Iran, being a part of a Late Palaeozoic megaplatform complex on the northern edge of Gondwana, is poorly known. Advances in facies studies and long-term sedimentary conditions to achieve a stratigraphic, palaeoenvironmental, and biostratigraphic framework, will significantly aid to resolve these ambiguities.…”

“…In general, Carboniferous sequences in many Iranian basins (Alborz, Kopeh Dagh, and Central Iran basins) include shallow‐water carbonates and siliciclastics deposited on low‐angle shelves, tens of kilometres in width (Aghanabati, 2004; Bayet‐Goll et al, 2018; Esfahani, Bayet‐Goll, Kangazian, Sadri, & Mohammadi, 2019). Such a wide ramp was created subsequent to the Ordovician‐Silurian rifting phase in the northern margin of Gondwana or along the southern border of the Palaeotethys Ocean (Bagheri & Stampfli, 2008).…”

“…Such thick units of organic matter-rich shales deposited in a flattopped, low-to moderate-energy carbonate platform have been reported in the basal Mobarak Formation in the Eastern Alborz (Bayet-Goll et al, 2020), the Tournaisian-Visean carbonate successions of the Esfahan-Sirjan Basin (ESB) from Sanandaj-Sirjan Zone (SSZ; Bayet-Goll et al, 2018) and the Kopeh Dagh Basin (field observations). These thick units are considered as an indication of a post-glacial transgressive episode (Late Devonian-earliest Mississippian glaciation in Gondwanaland; Isbell et al, 2003) of which their presence on a broad ramp platform and marine transgression of the Devonian-Carboniferous boundary due to melting of glaciers are the main factors in the development of organic matter-rich muddy intervals in the boundary (seeBayet-Goll et al, 2018). On this broad ramp platform along the southern margin of the Palaeotethys, the association of transgressive events with the deposition of thick open-marine marls/shales is considered as a common feature of the Mississippian of many Iranian basins(Bayet-Goll et al, 2018.…”

“…These thick units are considered as an indication of a post-glacial transgressive episode (Late Devonian-earliest Mississippian glaciation in Gondwanaland; Isbell et al, 2003) of which their presence on a broad ramp platform and marine transgression of the Devonian-Carboniferous boundary due to melting of glaciers are the main factors in the development of organic matter-rich muddy intervals in the boundary (seeBayet-Goll et al, 2018). On this broad ramp platform along the southern margin of the Palaeotethys, the association of transgressive events with the deposition of thick open-marine marls/shales is considered as a common feature of the Mississippian of many Iranian basins(Bayet-Goll et al, 2018.…”