Biomarkers and inorganic geochemical elements of Late Jurassic-Early Cretaceous limestone sediments from Banik Village i
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ORIGINAL PAPER
Biomarkers and inorganic geochemical elements of Late Jurassic-Early Cretaceous limestone sediments from Banik Village in the Kurdistan Region, Northern Iraq: implications for origin of organic matter and depositional environment conditions Mohammed Hail Hakimi & Ibrahim M. J. Mohialdeen & Wan Hasiah Abdullah & William Wimbledon & Yousif M. Makeen & Khairul Azlan Mustapha
Received: 2 December 2014 / Accepted: 24 February 2015 # Saudi Society for Geosciences 2015
Abstract Late Jurassic-Early Cretaceous limestone sediments from Banik Village in the Kurdistan Region, Northern Iraq, were analysed based on a combined investigation of elemental composition and biomarker characterisation. These investigations were used to define the origin, type of organic matters and their relation to the environment conditions during deposition. The bulk geochemical characteristics indicated that the Late Jurassic-Early Cretaceous limestone sediments were deposited in a marine environment with calcium-rich seawater. Their biomarkers provide evidence for a major contribution by aquatic organic matter with a minor terrigenous organic matter contribution. This is confirmed by normal alkanes, hopanoids, steroids and related compounds of the saturated hydrocarbons. Moreover, the salinity stratification and relatively reducing bottom water conditions are evidenced in the Late Jurassic-Early Cretaceous limestone sediments, as identified from Sr/Br, V/Ni and Pr/Ph ratios. The occurrence of gammacerane biomarker in the analysed samples is also a M. H. Hakimi (*) Geology Department, Faculty of Applied Science, Taiz University, 6803 Taiz, Yemen e-mail: [email protected] I. M. J. Mohialdeen Department of Geology, School of Science, University of Sulaimani, Kurdistan, Iraq W. H. Abdullah : Y. M. Makeen : K. A. Mustapha Department of Geology, University of Malaya, 50603 Kuala Lumpur, Malaysia W. Wimbledon Department of Earth Sciences, University of Bristol, Bristol, England
strong indicator of reducing and salinity stratification during deposition. Therefore, a stratified water column with salinity and relatively anoxic bottom water conditions contribute to organic matter (OM) preservation. Keywords Late Jurassic-Early Cretaceous limestone . Biomarkers . Inorganic geochemistry . Depositional condition . Banik Village . Kurdistan Region
Introduction The Kurdistan Region is an oil-rich area and has become the largest oil-producing portion of north Iraq. The Late JurassicEarly Cretaceous sediments are widespread and occur in Northern Iraq. The dataset used herein is from the Banik Village, Duhok Governorate, Kurdistan Region (Fig. 1a). The study area occupies the Northern part of the Kurdistan Region, which lies between latitudes 37° 13′ 33.4″ N and longitudes 42° 58′ 2.6″ E (Fig. 1b) and has attracted the interest of numerous researchers. The Banik Village is located at about 25 km northeast of Zakho City in the Kurdistan Region. The area is situated within the highly folded zone of Iraq (Buday 1980; Edilbi 2010). The Banik sect
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