TRACKING EVOLUTION OF THE EAGLE MOUNTAIN FORMATION CATCHMENT THROUGH HEAVY MINERAL ANALYSIS AND DETRITAL ZIRCON GEOCHRONOLOGY

The Eagle Mountain Formation, located east of Death Valley, is a clastic sedimentary unit that has been used to reconstruct post-middle Miocene extension and strike-slip deformation across eastern California. The formation contains a distinct clast assemblage, interpreted to have been sourced over 100 km northwest, in the southern part of the Cottonwood Mountains. Contrasting interpretations of the unit’s depositional environment, as an alluvial fan or fluvial setting, arise from its sedimentary structures, lack of dilution of distinct clasts, and the unit’s stacking arrangement. While more recent investigations of the Eagle Mountain Formation (Niemi, 2013) confirm the provenance of Hunter Mountain batholith clast-bearing intervals and suggest deposition in close (<12 km) proximity to a southern Cottonwood Mountains source, recent investigations in the adjacent Panamint Range suggest that exhumation along the Panamint-Emigrant detachment began within the timeframe of the unit’s deposition. The genesis of this detachment system and other extensional faults in the region is likely to have altered the catchment of the unit over time. This study aims to explore the evolution of the catchment and its relationship to nearby structures by tracking changes in heavy mineral compositions and detrital zircon age populations. To do this, we collected four samples from a transect across exposures at the Eagle Mountain Formation type locality. Preliminary results from mineral separation reveal distinct differences in heavy mineral concentrations in the samples that will be further explored through counting and classification of non-opaque grains and use of provenance-sensitive heavy mineral indices. The heavy mineral data will be used in conjunction with detrital zircon U-Pb ages from the samples to determine if any changes in sediment sources can be recognized up section and to explore their implications for this tectonically evolving landscape.