AAPG Geoscience Technology Workshop

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The Oligo-Miocene Chemostratigraphic Framework of the Levant Basin

Abstract

The discovery of prolific natural gas reservoirs in the Levant basin has driven renewed economic interest in this area and emphasized the importance of characterizing the properties of the Oligo-Miocene deposits in the East Mediterranean, including their source, transport pathways, and depositional conditions. As these sections have until recently not been recovered from the deep basin, their properties are poorly constrained and available observations in regards to the oceanographic history of the Levant Basin during the Oligo-Miocene are typically derived from marginal sites and at very coarse temporal and resolution. Here, we present the first high-resolution chemostratigraphic framework of Oligocene-Miocene deposits from the Leviathan-1 and Dolphin-1 wells in the East Mediterranean, based on the major and minor elemental abundances of drilling cuttings. The results reveal two prominent, superimposed, secular evolution patterns. The first consists of two major cycles of carbonate deposition occurring ca. ~20-14 Ma and ~10-7 Ma, reflected by Ca and Mg concentrations, as well as foraminifera deposition cycles. The second pattern is expressed by an ongoing trend of increase in the contents of the terrigenous-silicate detrital fraction, recognized through a gradual increase in the Fe/Al ratio over time between ~23-6 Ma. These patterns correspond to Sr and Nd isotope curves of sediments and foraminifera from the Umberia-Marche region (Kocsis et al., 2008, Paleoceanography), suggesting a regional scale control. By contrast, they appear to be unrelated to suggested episodes of opening and closing of the Neo-Tethys Indo-Pacific gateway. The terrigenous input record suggests a gradual long term shift in the sediment sources, which is hypothesized to be related to the development of the northern Africa landscape.