Parvaneh Roozbahani
Lithostratigraphy and biostratigraphy of the Lower Cretaceous of the Jalmajird area (northeast of Khomeyn, Central Iran Basin), Iran

Geo.Alp 9, 2012, p. 48–58

Abstract
In order to study the lithostratigraphy and biostratigraphy of the Lower Cretaceous of the Jalmajird area (northeast of Khomeyn, central Iran) two sections were measured and sampled. The main part of the succession consists of gray-bluish thin-bedded to massive orbitolinid limestones which are of Barremian-Albian age. The Lower Cretaceous sediments overlie the Rhaetian-Middle Jurassic Shemshak Group with an angular unconformity. At the base of the succession a several meter thick transgressive unit of dark red to brown conglomerates and sandstones is developed which corresponds stratigraphically to the Sangestan Formation (sensu Nabavi, 1972). The Lower Cretaceous is disconformably overlain by the Early Cenomanian Chrysalidina Limestone. According to the stratigraphic distribution of benthic foraminifera and associated fossil assemblages the Lower Cretaceous deposits of the studied sections are divided into four biozones. The angular unconformity at the base of the Lower Cretacecous unit is attributed to the Middle Cimmerian orogenic event. The Early Cretaceous transgression in the study area is considered to have occurred during the Neocomian? – Barremian.


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