Provenance and depositional environment of Neogene alluvial deposits in Birjand plain (South Khorasan)

Articles in Press

Document Type : Research Paper

Authors

1 Department of Geology, Faculty of Sciences, University of Birjand, Birjand, Iran

2 Department of Geology, Faculty of Sciences, University of Birjand. Birjand. Iran

Abstract

The Neogene alluvial deposits in the Birjand plain have been studied to investigate sedimentary environment, provenance and tectonic setting. This study is based on the field observations of 8 alluvial profiles in the road-cut outcrops and petrography of conglomerate clasts and sandstones. The petrography of the conglomeratic clasts indicates the presence of intrusive and extrusive igneous rock fragments such as ultramafic, mafic and intermediate rocks as well as sedimentary rock fragments such as sandstone and sandy limestone in these samples. Based on the quantitative analysis of detritus minerals sandstones are feldespathic litharenite to litharenite and their components are probably originated from intermediate to ultramafic igneous, sedimentary and minor amounts of metamorphic rocks. Ploting of the point-counting results on the provenance and tectonic triangular discriminating diagrams reflect these sediments were derived from the recycled orogen and mixed magmatic arc. According to the regional geology and the paleocurrent analysis, it seems that the Cretaceous ophiolitic units, the Late Cretaceous to Eocene flysch units, the Paleogene carbonate-clastic sedimentary rocks and Eocene-Miocene volcanic rocks in the north of study area are the source rock of the above sediments. The textural features and sedimentary structures show that these sediments are classified into three sets of conglomerate, sandstone and mudstone facies. Based on the vertical and lateral facies changes, the sedimentary environment of these deposits was probably a proximal shallow gravel bed braided system.

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Journal of Stratigraphy and Sedimentology Researches

Articles in Press, Accepted Manuscript
Available Online from 12 November 2024

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