REIDENTIFICATION AND REPOSITIONING OF DEVONIAN ROCKS IN THE SOUTHERN FUNERAL MOUNTAINS, SOUTHEASTERN CALIFORNIA

Our litho-, bio-, and event-stratigraphic correlations demonstrate that the previously mapped Lost Burro Formation, just east of Death Valley, is actually a displaced part of the Middle to Late Devonian carbonate platform of Nevada and western Utah. The upper ~85 m of Lost Burro unit lb2, containing abundant Stringocephalus brachiopods, is the upper Middle Devonian (Givetian) Fox Mountain Formation (see Sandberg and Morrow, this meeting). A sharp transgressive surface separating lower and upper parts of this interval represents the continent-wide Taghanic onlap. The overlying basal part of Lost Burro unit lb3, consisting of ~30 m of yellow-weathering argillaceous dolostone, is the widespread highest Middle Devonian yellow slope-forming (YSF) unit of the Guilmette Formation. Overlying the YSF is a ~245-m-thick carbonate-platform sequence within the upper part of Lost Burro unit lb3 and lower part of unit lb4, consisting of bedded dolostone, limestone, quartz sandstone, and biostromal rocks correlative with the lower Guilmette. An anomalous, 1.5-m-thick, high-energy channel deposit discovered in the middle of unit lb4 is related to the middle Frasnian (punctata Zone), marine Alamo Impact Event. An ~8.5-m-thick limestone interval above contains common middle Frasnian Tenticospirifer utahensis and Orecopia sp., an index gastropod occurring in punctata Zone rocks above Alamo channel deposits in Nevada and Utah. The upper ~195 m of unit lb4 consists mainly of upper Guilmette biostromal carbonate that is probably no younger than early late Frasnian (early Early rhenana Zone). The unconformably overlying upper Upper Devonian (Famennian) platform rocks of Lost Burro unit lb5 may represent the Crystal Pass Limestone. The Funeral Mountains Devonian sequence has been displaced northwestward and then southward by strike-slip offset across the Las Vegas lineament, Stewart Valley fault, and Death Valley-Furnace Creek fault zone. Comparison of this Devonian sequence and overlying Mississippian units to coeval sequences north of the Las Vegas lineament show that it was originally located in the vicinity of present-day Las Vegas and possibly is an extension of the Las Vegas Range.