ABSTRACT
Provenance and tectonic setting of the Late Lower Cretaceous (Albian)
sandstones in SW Iran have been interpreted on the basis of geochemistry (major
and trace elements) of 35 samples from Iranian offshore oil fields (Soroosh,
Nowrooz, Foroozan and Hendijan). Geochemically, trace-element concentrations,
such as La, Th, Sc and Zr, and ratios, such as La/Sc, Th/Sc, La/Co, and Th/Co,
of sandstones from Kazhdumi Formation at four localities indicate that they
were derived from felsic source rocks and deposited in a passive continental
margin. Most major and trace element contents of Kazhdumi sandstones are
generally similar to upper continental crust (UCC) values. However, some samples are depleted in major and trace
elements (such as K2O, Na2O, Sr and Ba) relative to UCC,
which is mainly due to absence or smaller amount of Na-rich plagioclase and
K-feldspar and also paucity of clay minerals, which is possibly due to
intense weathering and recycling. Enrichments in Zr, negative Sr anomalies and
Th/U ratios higher than 4 for Kazhdumi sandstones are further evidence for
recycled sources. The study of paleoweathering conditions based on chemical
index of weathering (CIW) indicates a moderate to intense weathering of first
cycle sediments, or it may alternatively reflect recycling under semi-arid to
semi-humid climate conditions in Kazhdumi sandstones. The results of this study
suggest that the main source for the Kazhdumi sandstones is likely located in
uplifted shoulders of a rifted basin (Neo-Tethys) in its post-rift stage
(Arabian basement).