CORRELATION OF THE BLACK ROCK AND OLDS FERRY ARC TERRANES? NEW DETRITAL ZIRCON FROM THE BOULDER CREEK BEDS IN THE JACKSON MOUNTAINS, NW NEVADA, USA

Late Triassic reconstructions have suggested that the Olds Ferry and Black Rock terranes represent fragments of the same Mesozoic fringing arc that were then separated and displaced by ~400 km of Cretaceous dextral strike-slip motion. In this model, the Mojave-Snow Lake Fault, the Western Nevada Shear Zone, and the Western Idaho Shear Zone represent strands of a Cretaceous fault zone that translated outboard terranes to their current positions. The Jackson Mountains (NW Nevada) represent an important locality to test this model being situated inboard of the proposed Cretaceous strike-slip faults. Therefore, the Jackson Mountains are effectively in place with respect to the North American continent and may act as potential tie between the continent and outboard terranes when assessing the role and magnitude of strike-slip displacement along the margin. Using a combination of LA-ICPMS and CA-IDTIMS, the Boulder Creek Beds are found to represent a package of Norian (~215 Ma) to Sinemurian (~195 Ma) volcanogenic, marine rocks. All analyzed subunits contain a primary Triassic to Early Jurassic mode with minimal input of older grains. Considering the texturally immature, volcanogenic, marine lithologies, these new data support marine deposition adjacent to an active Triassic and Jurassic volcanic arc with minimal input from other sources. Combined with regional geology, these new data are consistent with Triassic-Early Jurassic reconstructions in which the Black Rock arc was separated from the continent by a deep-marine basin. When compared to sediments deposited in the forearc of the Olds Ferry terrane, these data can be used to test the translation model. Sandstones from the Weatherby Formation yield a Late Triassic to Early Jurassic mode with minimal older grains. These patterns are remarkably similar to those from the Boulder Creek Beds and suggest derivation from similar-aged, active arc sources with no input from older, continentally derived material. This strong similarity in provenance supports a paleogeographic linkage between these geographically separated arc fragments and provides support for the correlation of Black Rock and Olds Ferry arc terranes as fragments of the same Mesozoic fringing arc system that was later separated by ~400 km of dextral strike-slip motion.