Paleoecology and Paleoenvironment of the Basal Purple Shales of the Pabdeh Formation at Bisheh-Deraz Section,  Southwest of Iran

Rabbani, J; Ghasemi-Nejad, E; Ashouri, A.R; Vahidinia, M

doi:10.22071/gsj.2015.42601

Paleoecology and Paleoenvironment of the Basal Purple Shales of the Pabdeh Formation at Bisheh-Deraz Section, Southwest of Iran

Document Type : Original Research Paper

Authors

J Rabbani ¹

E Ghasemi-Nejad ²

A.R Ashouri ³

M Vahidinia ⁴

¹ 1Geology, Ferdowsi University of Mashhad, Mashhad, Iran

² Professor, College of Science, Faculty of Geology, University of Tehran, Tehran, Iran

³ Professor, Faculty of Science, Department of Geology, Ferdowsi University of Mashhad, Mashhad, Iran

⁴ Associate Professor, Faculty of Science, Department of Geology, Ferdowsi University of Mashhad, Mashhad, Iran

10.22071/gsj.2015.42601

Abstract

The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences including palynofacies, abundance and diversity of dinocysts and environmental index have been investigated. Four Palynofacies types including IV: shelf to basin transition, VII-VIII: distal dysoxic-anoxic shelf, IX: distal suboxic-anoxic basin) have been differentiated that propose a distal suboxic-anoxic basin as depositional setting. According to the microfacies of planktonic foraminiferal Wakestone/Packestone a deep environment is proposed as the depositional basin. Using such parameters as palynofacies evidences, C/PPC ratio, AOM/MP ratio, abundance and diversity of dinocysts and environmental index, three system tracts related to one sequence (3^rdorder) with one sequence boundary type 2 and one maximum flooding surface have been determined. In general, the factors all together show a deepening upward trend through this rock unit.

Keywords

Paleoenvironment

Paleoecology

Purple shales

Pabdeh Formation

Zagros