Geochemistry of siliciclastic rocks from the Corral de En medio Formation and Camas Sandstone, Cabullona basin, Sonora: paleoweathering and provenance

The sedimentary sequence of the Cabullona Group deposited in the Cabullona basin during Late Cretaceous is well exposed in the Naco region of northeastern Sonora. It has been divided into various formations and the total thickness of this group is about 2.5 km with possible age of 72 Ma. Geochemical study was undertaken on the sandstones of the Corral de Enmedio Formation and the Camas Sandstone to determine the paleoweathering, provenance and tectonic setting. The SREE contents range from 96 to 144 ppm for the sandstones from Corral de Enmedio Formation and 74 to 169 ppm for the Camas Sandstone. The chondrite normalized REE diagrams for sandstones from both formations have LREE enriched, relatively flat HREE patterns with negative to positive Eu anomalies. The CIA and PIA values and A- CN- K diagram indicate that the sandstones of the Corral de Enmedio Formation were derived from the source area that was subjected to a low degree of chemical weathering, whereas the Camas Sandstone reveals low to moderate intensity of chemical weathering of the source area. Al2O3/TiO2 ratios, and various bivariate and ternary diagrams, comparison of REE patterns with source rocks, and mixing calculation of source rocks indicate that the sandstones of the Corral de Enmedio Formation were predominantly derived from felsic source rocks, with minor contribution from intermediate rocks, whereas the Camas Sandstone received sediments mainly from felsic source rocks.