LATE NEOGENE-QUATERNARY TEPHROCHRONOLOGY, STRATIGRAPHY AND PALEOCLIMATE OF DEATH VALLEY, CA, U.S.A

Seventy-seven tephra beds tephra beds sourced from five different volcanic centers found in multiple stratigraphic sections were correlated to elucidate late Neogene to Quaternary (3.58 Ma to 32 ka) stratigraphy and paleoclimate of Death Valley, U.S.A.. We informally named seven previously unrecognized units: 3.54 Ma tuffs of Curry canyon, 3.45 Ma tuff of Furnace Creek, 3.1 Ma tuff of Kit Fox Hills, 3.1 Ma tuff of Mesquite Flat, 3.122 Ma tuff of Echo Canyon, 3.15 Ma tuff of Texas Spring, and the 1.22 Ma Amargosa ash beds. Using tephrochronology, magnetic polarity and ⁴⁰Ar/³⁹Ar age data we redefine the Furnace Creek Formation as a time-transgressive lacustrine and alluvial fan sequence deposited between 6.0 and 2.5 Ma. The 2.5 to 1.7 Ma Funeral Formation is typically comprised of proximal alluvial-fan facies that often includes the 1.98-1.78 Ma lower tuffs of Glass Mountain. We correlated deposits in the Kit Fox Hills, Salt Creek, Nova Basin, and southern Death Valley with deposits in the 1.3-0.5 Ma Mormon Point formation. Exposures of the 32 ka Wilson Creek ash bed 15 in the Lake Rogers deposits shows that these deposits unambiguously coincident with the Last Glacial Maximum (Marine Isotope Stage [MIS] 2). The stratigraphy allows correlation of the Pliocene and Pleistocene Death Valley climate with the marine tropical/subtropical record. Pluvial Pliocene lakes in Death Valley and Searles Valley began by 3.5-3.4 Ma, providing indirect evidence of a wetter (glaciated) climate in western North America during the late Pliocene (MIS M2/MG2). Otherwise, the late Pliocene Death Valley climate was arid including during the Northern Hemisphere Glaciation. Pleistocene pluvial lakes existed in Death Valley at ca. 1.98 to 1.78 Ma, 1.3 to 1 Ma and 0.6 Ma (MIS 16), but Death Valley was relatively dry at 0.77 Ma (MIS 19). From the shallow lake to marsh deposits of Lake Rogers, we infer that MIS 2 was wetter than today, but not as wet as MIS 6.