DETAILED GEOLOGIC MAP OF THE NORTHERN CALICO MOUNTAINS AND THE LANE MOUNTAIN AREA, CENTRAL MOJAVE DESERT CALIFORNIA: PART 3 PRELIMINARY DIGITAL GEOLOGIC MAP

Detailed geologic mapping (1:6,000 scale) of the northern Calico Mountains and Lane Mountain area north of Barstow, CA, has been compiled into a preliminary digital geologic map at a scale of 1:18,000. The map displays ~50 units representing Paleozoic and Mesozoic(?) metasedimentary and metavolcanic rocks, at least 3 generations of plutonic rocks (Permo-Triassic, Late Jurassic, and Late Cretaceous), early Miocene volcanic, sedimentary and intrusive rocks, (Lane Mtn volcanics, Jackhammer and Pickhandle Formations), and Quaternary deposits. The metasedimentary and metavolcanic rocks form east-dipping, folded, tectonostratigraphic units with an aggregate thickness of ~8 km. From bottom to top the metamorphic sequence comprises a basal unit of metavolcanic rocks; slope and basin affinity rocks (mostly quartzite), structurally interleaved with miogeoclinal carbonate rocks interpreted to represent Cambrian Bonanza King Formation, Mississippian Monte Cristo Limestone and Pennsylvanian-Permian Bird Spring formation; mixed siliciclastic and carbonate offshore and shallow water carbonate rocks of possible Permian age; structurally repeated metavolcanic rocks; overlain by quartzitic turbidites, vitreous quartzite; and offshore and shallow-water mixed siliciclastic and impure carbonate rocks. Calc-hornfels and conglomerate resembling Early Jurassic Fairview Valley Formation are also present, but the age and stratigraphic/structural relations of these rocks are uncertain. A detrital zircon study to constrain the ages of the metasedimentary rocks is underway. New U-Pb zircon SHRIMP analysis of selected plutonic rocks indcate the existence of ~253-Ma diorite, ~150-Ma gabbro, quartz diorite, and quartz monzonite. New Rb-Sr data indicate Sri of ~0.704, 0.705, and 0.708 for the Permo-Triassic, Late Jurassic, and Late Cretaceous plutons, respectively, reflecting an increasing continental signature in the magmas through time. Stratigraphically and structurally complex, faulted and locally folded Miocene rocks are thought to have formed in synextensional supradetachment basins related to development of the central Mojave core complex.