چكيده فارسي :
A very rich brachiopod fauna comprising 54 taxa has been found in the Tournasian marly limestones and bioclastic limestones of the Mobarak Formation, Alborz Mountains and N Iran. It comprises: Leptagonia cf. L. analoga (Phillips, 1836), Caenanoplia cf. C. burlingtonensis (Carter, 1968), Geniculifera sp. ind., ?Rhytiophora sp. ind., Antiquatonia sp. ind., Promarginifera sp. ind., Dictyoclostinae gen. et sp. ind., Buxtonia sp. ind., Marginatia vaughani (Muir-Wood, 1928), Marginatia aff. M. deruptoides Sarytcheva in Sarytcheva, Sokolskaya, Beznosova Maksimova, 1963, Tomiproductus elegantulus (Tolmatchoff, 1924), Tolmatchoffiini gen. et sp. ind., Pustula cf. P. altaica Tolmatchoff, 1924, Pustula sp. ind., Pustulinae gen. et sp. ind., Brochocarina sp. ind., Orthotetoidea fam. ind., Schellwienella sp. ind., Rhipidomella michelini (Léveillé, 1835), Schizophoria (Schizophoria) resupinata (Martin, 1809), Hemiplethorhynchus crassus Gaetani, 1968, Rossirhynchus adamantinus Gaetani, 1964, Paraphorhynchus aff. P. elongatum Weller, 1905, Athyris sp. ind., Lamellosathyris lamellosus (Léveillé, 1835), Cleiothyridina kusbassica Beznosova in Sarytcheva, Sokolskaya, Beznosova Maksimova, 1963, Cleiothyridina sp. ind., Gerankalasiella sp. ind., Carteridina sp. ind., Composita megala (Tolmatchoff, 1924), Composita subquadrata (Hall, 1858), Composita aff. C. pentagonia (Weller, 1914), Composita cf. C. caimaensis Chen, Tazawa, Shi Matsuda, 2005, Composita sp. ind., ?Densalvus sp. ind., ?Iniathyris sp. ind., Sottofam. Spirigerellinae gen. et sp. ind., Fam. Athyrididae sottofam., gen. et sp. ind., Kisilia sp. ind., ?Tenisia sp. ind., Ectochoristites sp. ind., Parallelora sp. ind., Unispirifer (Unispirifer) striatoconvolutus (Benson Dun in Benson, Dun Browne, 1920), Unispirifer cf. U. (Septimispirifer) septimus (Thomas, 1971), Unispirifer sp. ind., Atylephorous sp. ind., Sottofam. Prospirinae gen. et sp. ind., Voiseyella aff. V. texana (Carter, 1967), Brachythyris sp. ind., Kitakamithyris sp. ind., Torynifer sp. ind., Syringothyris carteri (Hall, 1857b), Syringothyris skinderi Sokolskaya in Sarytcheva, Sokolskaya, Beznosova Maksimova, 1963, Pseudosyrinx sp. ind. The fauna has been bed by bed collected along two sections: Abrendan section and Simeh Kuh section, whose correlation has been tempted using quantitative biostratigraphy. Although mostly cosmopolitan, the brachiopods show close affinity to North
America, Western Europe and the Russian Platform than to cold water Australian faunas, confirming the affinity of foraminifers and other biota. This seems to contradict Early Mississippian paleomagnetic reconstructions placing the Alborz region at 45– 50° South latitude. The answer to this discrepancy may lie in the circulation of Paleo-Tethyan currents to the south along the Gondwanan shelf.
