A comprehensive approach toward provenance study; Mineralogy, Sr, Pb and Nd isotopes; the case of the Cambrian sandstones, Israel

Provenance studies are important for understanding continental-scale processes such as uplift, erosion and sedimentation and they are generally based on one or two proxies such as heavy mineral assemblage, zircon dating and... [ view full abstract ]

Provenance studies are important for understanding continental-scale processes such as uplift, erosion and sedimentation and they are generally based on one or two proxies such as heavy mineral assemblage, zircon dating and petrography. The Cambrian siliciclastic sequence of Northern Gondwana is exposed in Southern Israel and constitutes the Yam Suf Group. At the base, nonconformally overlaying the eroded basement, are medium to coarse subarkoses (Amudei Shelomo Fm) which are overlain by dolomitic and lime (Timna Fm.). On top of this marine intercalation, subarkoses reappear (Shehoret Fm.) and the sequence is capped by quartz arenites (Netafim Fm.), terminated by a Cretaceous unconformity. In general, the sequence indicates a continental-scale long distance braided streams system with a general south to north (current configuration) flow direction. However, the provenance of each of the sands formations is not fully understood.
In order to trace the potential sources for these sediments we applied mineralogical and elemental analyses along with isotopic measurements of Pb, Nd and Sr on three mineralogical phases separated from each representative sample; heavy mineral assemblage, clays and feldspars. In addition, feldspars and saprolite separated from representative lithologies of the Arabian Nubian Shield were also analyzed for reference.
Each of the proxies applied on each mineralogical phase lead to discrete characterization of potential provenance. For example, 87Sr/86Sr, 206Pb/204Pb ratios, Pb model age and µ values of feldspars suggest a distinct isotopic fingerprint, which is not compatible fully with their derivation from the nearby ANS. This is further emphasized by the difference in Nd model ages between detrital feldspars (ca. 1400 Ma) and feldspars extracted from the ANS (1000 Ma).
Overall, results indicate that feldspars were derived from the shield (remote and nearby), while and heavy minerals and clays suggest a mixture of sediments derived from several sources of distinct geological and geochemical nature; the adjacent juvenile Arabian Nubian Shield and the remote and ancient remobilized terrains.
These results complement previous studies that focused primarily on heavy minerals and zircons in particular and demonstrate the strength of the methodology that can be further applied in future studies of siliciclastic sedimentary sequences.