Geochemical characteristics of bitumen seeps from the pila spi and bekhme formations: insights from fourier transform infrared spectroscopy and trace metals

Abstract

A collection of 9 bitumen samples from Pila Spi Formation (Middle–Late Eocene) and Bekhme Formation (Late Campanian – Early Maastrichtian) were subjected for geochemical analysis of Fourier Transform Infrared Spectroscopy (FTIR) and trace metals. The results of FTIR analysis reveal the different intensity for the samples of both formations. The broad band centered around 1500–2000 cm−1 which is indicative of the presence of C=O Stretch band and C=C Stretch might be assigned to a carbonyl stretching. The Frequency of the bitumen - derived asphaltene samples of the Gulley Keer indicate the presence of Carboxylic acids, while no band appeared for Bekhme samples which indicates the absence of Carboxylic acid. The peak absorption bands of the analyzed samples at 1452, 2802, 2905, and 3050cm−1 can be due to C-H bending, Alkyl C-H stretch, and Alkenyl C-H stretching respectively. Based on the Aromatic, Aliphatic and long chain indices as well as the ratio of Nickle to Vanadium, two different sources of the organic matter are suggested for analyzed samples. Moreover, all samples from both sections are believed to be from a marine euxinic carbonate environment with the exception of one sample that seems to be marine anoxic- shale- carbonate.