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A Composite Stable Isotope Curve for the Jurassic of Kuwait: An Important Step Towards Cross-Border Correlation in the Middle East Region

Abstract

In Kuwait, the Jurassic is attracting more and more attention as a target for oil exploration. In fact, the Jurassic of the entire Middle East region contains both important source rocks and reservoirs. Although the Jurassic successions across the Arabian Platform are broadly similar, detailed cross-border correlations are still lacking. In order to develop regional petroleum geological models, high-resolution long-distance correlations are essential. Unfortunately, unfavourable lithologies such as anhydrite, dolomite and organic rich argillaceous limestone, limit the use of regular biostratigraphic techniques. However, the application of stable isotopes provides a powerful correlation tool across the region. Here we present the results of a large study aimed at developing a composite stable isotope curve that may serve as a standard for the Jurassic of the entire Middle East region. In total, 695 samples from 13 wells have been analyzed, mostly from cored sections. All samples have been analyzed for carbon (δ13C) and oxygen (δ18O) isotope composition of the in-situ carbonate. In particular, the trend of the δ13Ccarbonate curve turns out to be very robust, which is reflected in the perfect match of the overlapping stratigraphic sections from different wells. Both subtle trends are recorded as well as a number of larger shifts. One particularly interesting event, probably recorded for the first time, is a 7 per mil negative shift in the δ13Ccarbonate record spanning the transition between the Sargelu and Najmah Formations. Based on new biostratigraphic data, this event is correlated to the Late Bathonian. Whether this isotope excursion is global or regional remains to be seen, but it illustrates the promising perspective for long-distance stable isotope correlation.