Foraminiferal proliferations in the Alborz Basin (northern Iran): global responses to Early Carboniferous glaciations

Mississippian lithofacies and foraminiferal biozonation of the Alborz Mountains, Iran: Implications for regional geology

“…The Mobarak Formation in south‐central Alborz (Mobarakabad, Geirud, and Abnak areas) is mostly represented by a succession of marly and black shale interbedded with thin‐bedded, clayey crinoid‐ and brachiopod‐bearing limestone, dolomitic limestone, and medium‐ to thick‐bedded ooidal limestone (Figure ; Assereto, ; Brenckle et al, ; Najafi, ; Zandkarimi, ). In the east‐central Alborz (Aieneh‐Varzan Anticline, eastern Damavand City), it shows significant lithological variations (Figures ) so that the lower marly and shaly parts are missing or are very thin (Abadi, Kulagina, & Voeten, ; Payami‐e Rad, ; Zandkarimi, ). The Mobarak Formation of the north‐central Alborz has a relatively different lithology compared with that of type area, in south‐central Alborz.…”

“…Towards the south‐eastern Alborz, the Semnan and Damghan areas, the Mobarak Formation mainly consists of lower marl and shale with macrofossil‐bearing limy intercalations and upper medium‐ to thick‐bedded limestone (Abadi et al, ; Mosaddegh, ), indicating high resemblance to that of east‐central Alborz, despite the absence of the uppermost Viséan ooidal lower unit (Figure ). There are a few data about the lithology of the Mobarak Formation in the north‐eastern Alborz.…”

“…As mentioned above, the Mobarakabad area, south‐central Alborz, contains lower marl, middle dolomitic limestone, and upper oolitic limestone (Figure ). Towards east‐central Alborz, eastern Damavand City (Aieneh‐Varzan Anticline), the lower marl unit becomes very thin or even is missing (Figure ; Abadi et al, ; Payami‐e Rad, ; Zandkarimi, ). Moreover, the oolitic limestone that is characteristic of the northern Alborz is not observed in the east‐central and south‐eastern Alborz (Abadi et al, ; Brenckle et al, ; Mosaddegh, ; Zandkarimi, ).…”

“…Towards east‐central Alborz, eastern Damavand City (Aieneh‐Varzan Anticline), the lower marl unit becomes very thin or even is missing (Figure ; Abadi et al, ; Payami‐e Rad, ; Zandkarimi, ). Moreover, the oolitic limestone that is characteristic of the northern Alborz is not observed in the east‐central and south‐eastern Alborz (Abadi et al, ; Brenckle et al, ; Mosaddegh, ; Zandkarimi, ). The Mississippian rocks of the north‐eastern Kiyasar area (Falahatgar & Mosaddegh, ) and most north‐easterly areas of the Alborz (eastern Gorgan City, Tilabad; Jenny et al, ; Lys et al, ; Saeidi et al, ) show lithological and facies resemblances to the north‐central Alborz and significantly different from the southern flanks (Figure ).…”

“…Palaeoenvironment reconstruction of the Alborz Mississippian across the SE–NW direction. (a) A relatively deeper marine conditions dominated in most parts of eastern Alborz during the Late Tournaisian, whereas very shallow water environments (supratidal to lower tidal) are observed in east‐central Alborz (Aieneh‐Varzan Anticline), immediately changing to the north into deeper middle and inner ramp settings (Mobarakabad and Abnak sections); (b) during the Viséan–Serpukhovian probably due to effects of inherited basement faults such as Mosha–Firuzkuh fault system, most of east‐central Alborz and eastern Alborz experienced uplift and nondeposition, whereas at the same time, northern Alborz remained under marine conditions (data compiled from Abadi et al, ; Bozorgnia, ; Brenckle et al, ; Falahatgar & Mosaddegh, ; Jenny et al, ; Lys et al, ; Mosaddegh, ; Najafi, ; Zandkarimi, ). Abbreviations of microfacies are as follows: PSPW = peloidal spicule packstone/wackestone; APWM = argillaceous peloidal wackestone/mudstone; BMW = bioclastic mudstone/wackestone; CP = crinoid packstone; BP = bioclastic packstone; OMW = ostracod mudstone/wackestone; AG = aggregate grain grainstone; ROP = radial ooid grainstone; CBOG = coated bioclastic ooid grainstone; COG = concentric ooid grainstone; IG = intraclastic grainstone; BG = bioclastic grainstone; SOG = shelly ooid grainstone; SBG = sandy bioclastic grainstone; PG = peloidal grainstone; GAG = green algal grainstone; LM = lime mudstone; FGAG = foraminiferal green algal grainstone; BPG = bioclastic packstone/grainstone; QROG = quartz radial ooid grainstone; SBP = sandy bioclastic packstone; SWM = sandy wackestone/mudstone; MQ = mature quartzarenite; SQ = submature quartzarenite [Colour figure can be viewed at wileyonlinelibrary.com]…”