PALEOMAGNETISM OF THE FURNACE CREEK FORMATION IN ZABRISKIE WASH, DEATH VALLEY, CALIFORNIA

The late Miocene to early Pleistocene Furnace Creek Formation in Death Valley, CA, is interbedded conglomerate, sandstone, siltstone, and mudstone that strikes about 300˚ and dips 40˚ to the northeast. The formation crops out on the east side of the valley in Zabriskie Wash and parallel unnamed washes. Exposed in the washes are four tuff beds that bracket the lower boundary of the Mammoth Reverse Subchron (3.33 ma) in the Gauss Normal Chron (2.58 - 3.58 ma): Curry Canyon Tuff and tuff of Zabriskie Wash that record normal paleomagnetic polarity, and upper Mesquite Springs tuff and Nomlaki Tuff Member of the Tuccan and Tehama formations that record reverse paleomagnetic polarity (Machette et al., 2005). The paleomagnetic polarity has been measured lower in the formation and shows that deposition occurred during the upper Gilbert Reverse Chron (earlier than 3.58 ma), and at Zabriskie Point the formation might record the Cochiti Normal Subchron (4.18 - 4.29 ma). At the base of the Mammoth Reverse Subchron where the formation was most densely sampled in a vertical stratigraphic interval of about 100 meters, three sites record reverse paleomagnetic polarity and five record normal paleomagnetic polarity. The mean paleomagnetic directions for those sites following thermal demagnetization to 600˚C are Incl. = 60.6˚, Decl. = 355.2˚, Alpha-95 = 24.6˚, N = 8. Similar paleomagnetic directions are recorded at the base of the Mammoth Reverse Subchron in the unnamed wash immediately north of Zabriskie Wash. Our paleomagnetic investigation of the Furnace Creek Formation follows an introduction by Michael Machette to exposures of the formation and volcanic tuffs in Zabriskie Wash and parallel ones during the 2001 Friends of the Pleistocene Field Trip in Death Valley. Thus, for Liddicoat and Knott, we welcome the opportunity to participate in the topical session recognizing Michael’s years of laudable geologic research of the Quaternary.