Stratigraphic similarities between Caborca strata and coeval strata in the Mojave and southern Great Basin regions (California and Nevada) have lead to diverse interpretations for the origin of the Caborca succession. Most notably, translocation of the Caborca block 700-800 km along the left-lateral Mesozoic Mojave-Sonora megashear was proposed to account for the detached position of Caborca strata southeast of correlative units in the U.S. However, recent work suggests that the Caborca succession is an autochthonous terrain that represents deposition within a northern embayment along a continuous, wrap-around, southern Cordilleran continental margin. To test either of these two hypotheses, it is fundamental to examine regional relations of Caborca strata with coeval strata in the adjacent southern Basin and Range (Arizona), however, such relations are poorly documented in the literature and necessitate reevaluation.
This project will emphasize documenting stratigraphic, sedimentologic, and petrologic attributes of the Middle-Upper Cambrian Arrojos-Tren succession in the Caborca region and the Middle-Upper Cambrian Bolsa Quartzite-Abrigo succession in southeastern Arizona. Stratigraphic and sedimentologic analyses will be used to define facies relationships and interpret depositional systems within both regions. Microprobe, X-Ray fluorescence, and neodymium isotopic analyses of clastic units will be performed to determine trace element and bulk-rock mineralogy to be used in provenance interpretations. Trilobite and conodont zonations will provide temporal constraints. When combined, these results may allow reasonable interpretations to be made for the spatial distribution of Cambrian deposition of Caborca strata with respect to the southern Basin and Range and help aid in the resolution of the uncertain origin of the Caborca succession.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid