TITLE:
Lithostratigraphy and Microbiostratigraphy of Gadvan and Darian Formations in South Semirom, East of Zagros Basin, South-Central Iran
AUTHORS:
Mohammad Kazem Hamedanian, Seyed Hamid Vaziri, Mahnaz Amir Shakarami, Mehran Arian, Naser Arzani
KEYWORDS:
Lower Cretaceous, Foraminifera, Gadvan, Darian, Biozone, Zagros, Semirom
JOURNAL NAME:
Open Journal of Geology,
Vol.7 No.2,
February
22,
2017
ABSTRACT: This research focuses on the lithostratigraphy and microbiostratigraphy implications
of the Gadvan and Darian Formations in a part of Zagros sedimentary basin. The
Gadvan and Darian Formations in the study area with a thick-ness of 520 meters consist
of gray to green marls and shales, dark-grey limestones and Orbitolina limestone with Late Barremian-Aptian
age. According to the lithostratigraphic investigations, the Gadvan and Darian Formations
in the study area are subdivided into eleven units. The upper boundary of the
Darian Formation with the Kazhdomi Formation and the lower boundary of Gadvan
Formation with the Fahliyan Formation are in the form of disconformity.
Micropaleontological study of the Gadvan and Dariyan Formations has led to the
recognition 20 families, 45 genera, 35 species of benthic foraminifera, 2
genera of pelagic foraminifera and 8 genera and species of the calcareous
algae. In this research, three biozones have been recognized by distribution of
the larger benthic foraminifera in the Gadvan and Dariyan Formations of the
South Semirom, including: 1) Palorbitolina
lenticularis-Choffatella decipiens Concurrent Range Zone (middle Late Barremian to
early Early Aptian); 2) Praeorbitolina
cormyi-Orbitolina (Mesorbitolina) lotzei Assemblage Zone (late Early Aptian); 3): Orbitolina (Mesorbitolina) texanae-Orbitolina (Mesorbitolina) parva Assemblage Zone (Middle to Late Aptian).
Based on the identified foraminifera, the age of the Gadvan and Darian Formations
in the study area is assigned to Late Barremian to Aptian.