THE HANAUPAH-FAN SHORELINE DEPOSIT AT TULE SPRING (DEATH VALLEY, CALIFORNIA) REVISITED

We ran 2 new GPR lines across the Hanaupah-Fan Shoreline Deposit at Tule Spring, a gravelly shoreline deposit of Pleistocene Lake Manly in Death Valley, California. The lines are 790 m and 220 m long, oriented parallel and perpendicular to the fan axis. The deposit was first described by Ibbeken and Warnke in 2000 (J. of Paleolimnology, v. 23, p. 439-447). At that time it was assumed that the deposit was formed during a transgressive phase of Lake Manly during marine-isotope stage (MIS 2), i.e. Wisconsinan. Our new GPR lines, and a newly available age date by Machette, Phillips, and Slate (Geological Society of America Abstracts with Programs, Vol. 35, No. 6, September 2003, p. 257-258) necessitate a re-interpretation. The age of this deposit is given by Machette et al. as 128-145 ka and correlates with MIS 6. The GPR data resolve dipping reflectors at depths of approximately 2-4 m. The axial line shows a few landward-dipping reflectors, but offlapping, basinward-dipping reflectors are more common, indicating that the deposit was mainly formed during a regressive phase of Lake Manly (albeit with oscillations) towards the end of MIS 6. The deposit is now being destroyed by erosional processes as is the surrounding Q3 surface of the fan. The original extent of the deposit remains unknown.