Chemical Variation during Pabdeh Formation Deposition, Zagros Basin: Gurpi-Pabdeh-Asmari Boundaries determination and Paleoenvironmental Condition

Tabatabaei Hossein Motamed Ahmad,Soleimani Bahman Kamali Mohammad Reza

doi:10.4172/2329-6755.1000102

Abstract

Determination of the formation of the Pabdeh boundary is a main challenge in Zagros sedimentary basin area. The work on hand is an attempt to clarify those based on chemical changes. The location under observation is the outcrop of the Pabdeh Formation (Paleocene-Oligocene) in Bangestan Anticline, the southern part of Zagros orogenic belt. The Pabdeh Formation stratigraphy linked to Asmari and Gurpi has been introduced as a gradual type and somewhat vague in this respect. To overcome these problems, 12 fresh samples from Gurpi, Pabdeh, and Asmari have been selected and chemically analyzed. Variation on both major and trace elements during this stratigraphy sequence generally reveal the high peaks of their frequencies in the lower and upper borders of the Pabdeh Formation. This border is different to the border which was determined during normal studies. These variations illustrate that the stratigraphy age reduction in the boundary of expected deposition time is based on present data documented that the Cretaceous-Tertiary boundary (K-T) had started lower than the stratigraphy limit. Geochemical ratios, including Ni/Co, V/Cr, and V/(V+Ni) were used to diagnose the Paleo-environmental conditions of Pabdeh Formation in comparison to Gurpi and Asmari formations. These chemical indicators present variable paleoredox conditions for the Pabdeh Formation.

Highlights

According to the stratigraphy evidence available, Pabdeh-Asmari and Pabdeh-Gurpi have been mentioned as ultimate border in the Zagros sedimentary basin [1]
76 samples were collected from the sample cuts and 70 of them belonged to the Pabdeh Formation while 3 samples to Gurpi and 3 belonged to Asmari
Changes in the mineral compositions of a formation can be noticed and which are dependent on parameters and different processes such as sedimentation rate, deposition environment and paleo-climatic conditions, litho logy and digenetic effects

Summary

Introduction

According to the stratigraphy evidence available, Pabdeh-Asmari and Pabdeh-Gurpi have been mentioned as ultimate border in the Zagros sedimentary basin [1]. The Cretaceous-Paleocene sediments are widely distributed throughout the Dezful Embayment, Zagros region but identification of the boundary of the Gurpi Formation (Cretaceous) sometimes are exposed to problems with the Pabdeh Formation (Paleocene) and so litho-stratigraphically it’s called Gurpi-Pabdeh. In Zagros area there are many obscurities regarding the K-T border which means the border between Gorpi and Pabdeh formations As far as these two formations are concerned, in this article we try to with regard to the geochemical differences provide dissociation through time since working is impossible through stratigraphy. Formation pieces being connected to each other via a mold of shale and marl (Figure 2) This border is erosion type with same inclination. Geographical specifications of the area studied are 50°15′ east, 3035′ north

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