--> Tracking structural changes in the Maniobra Basin to determine tectonic history and depositional setting

AAPG Pacific Section Convention 2019

Datapages, Inc.Print this page

Tracking structural changes in the Maniobra Basin to determine tectonic history and depositional setting

Abstract

The Maniobra Formation is composed of Eocene marine strata located on the northeastern flank of Orocopia Mountains in Southern California. The formation lies unconformably above Cretaceous granitic rocks and below the non-marine Miocene Diligencia Formation. Previous work described the lithofacies and interpreted these strata as a southwest trending submarine canyon formed along the continental margin forarc basin ~50 m.y. ago. The proximity of these sedimentary deposits to the Orocopia schist and Orocopia and Clemens Well detachments systems, combined with normal faulting of the basin units, suggests that there may be a causal relationship between exhumation of the the Orocopia Schist and basin formation represented by the Maniobra deposits. To test the hypothesis that the Maniobra Formation was deposited in a supra-detachment basin during the Eocene, we present new geologic mapping, detrital zircon geochronology, and magnetostratigraphy from the Maniobra Formation. Three sections in the western portion of the study area have been measured and correlated with a total stratigraphic thickness of 450 meters. The lithologies are sedimentary ranging from fine grained shale to boulder conglomerate. Key lithologies within the measured section have been mapped, units were chosen based on distinguishing attributes such as fossils, color, and overall appearance. Sample collection for magnetostratigraphy has been done throughout the measured sections. These samples will be used to determine reversals in the section. Detrital zircon samples have been collected at the base, middle and top of the entire study area. The detrital zircon data will be used to calculate ages of the section. If normal faulting from a supra-detachment basin has occurred, a combination of mapping, magnetostratigraphy, and detrital zircon data should support that theory. Our results will provide new constraints on the timing and provenance of basin stratigraphy, and support or refute our hypothesis that these strata represent deposition within a hyper-extending basin during the Eocene.