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BOLETÍN DE LA SOCIEDAD GEOLÓGICA MEXICANA http://dx.doi.org/10.18268/BSGM2009v61n3a6 |
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Late Triassic and Early Cretaceous sedimentary sequences of the northern Isfahan Province (Central Iran): stratigraphy and paleoenvironments
Paleoecología y paleogeografía de secuencias del Triásico Superior al Cretácico Inferior en el área de Isfahan (Irán central)
Maryam Mannani1,*and Mehdi Yazdi1
1 Department of Geology, University of Isfahan, Isfahan, Iran.
* This email address is being protected from spambots. You need JavaScript enabled to view it..
Abstract
This research gives a general outline of the Upper Triassic and Lower Cretaceous sequences cropping out north of Isfahan, Central Iran. Upper Triassic Nayband Formation subdivided into the Gelkan, Bidestan, Howz–e–Sheikh, Howz–e Khan and Qadir members. Two biostromal levels are documented in the Bidestan and Howz–e–Khan members. Due to a suitable condition in Late Triassic time including light, oxygen and nutrient, fauna such as: corals, sponges, hydrozoas, bivalves, gastropods, brachiopods, echinoderms and Dicroidium were fourished in water and flora on land. The first appearance of Heterastridium spp. in level of the Bidestan Member is apparently the first occurrence of this taxon in Central Iran. Qadir Member has several key beds, one key bed with land flora Clathropteris spp., and three key beds with bivalve Indopecten glabra, dating as Rhaetian Stage. An angular unconformity can be traced between Rhaetian sediments and red conglomerates and sandstones of Lower Cretaceous Sequences in Isfahan area which encompasses all Jurassic rocks. This gap can be related to Cimmerian tectonic phase.
Keywords: Upper Triassic, Lower Cretaceous, Nayband Formation, Isfahan Province, Cimmerian.
