ISOTOPIC PROVENANCE DETERMINATION OF CALCAREOUS CLASTS IN THE EBRO BASIN, SPAIN

Provenance analysis to the level of precision of individual formations has traditionally proved difficult for extrabasinal carbonate clasts. This limits the possibility of reconstructing regions such as the Catalán Coastal Ranges (CCR) and the adjacent Ebro Basin (northeastern Spain), in which any unroofing sequence will primarily record input from the CCR's thick Mesozoic carbonate platform sequence. We demonstrate the feasibility of carbonate provenance determination by stable isotope (C, O) geochemistry. Following earlier studies which have mainly demonstrated the possibility of using stable isotope geochemistry for such a task, we now focus on attempting to determine an unroofing sequence for the CCR and demonstrate results which yield provenance interpretations more specific than those attempted previously. A suite of individual clasts from several basin-fill units at two sampling locations (southeast and east-central) within the Ebro Basin were analyzed for δ¹³C and δ¹⁸O. The vast majority of analyzed clasts fall within δ¹³C/δ¹⁸O fields defined by groups of CCR carbonate units, indicating that δ¹³C and δ¹⁸O are likely preserving a provenance signal. There is an apparent difference in the provenance of sands and gravels in the southeastern sampling location, while gravels sampled from the two sites were determined to derive from different levels within the CCR carbonate succession: Triassic material predominates in the east-central location, and appears to be nearly absent in the southeast, where a mixture of Jurassic and Cretaceous material makes up the basin fill. That our method can distinguish this provenance information indicates that we will be able to use it to determine an unroofing sequence for the CCR, and that it may be applicable for determining unroofing sequences in similar areas where basin-fill is similarly dominated by extrabasinal carbonate clasts.