T208 Lakes, Playas, and Soils

Monday, 6 October 2008
1:30 PM - 5:30 PM

Soil Development, Pluvial Lakes, Alluvial Fans, and Quaternary Faults in Newark Valley, Central Nevada

Paper number: T208-10
Program: Technical Sessions
Time: 3:45 PM – 4:00 PM

Authors

Abstract

Soil development into shoreline deposits in Newark Valley, central Nevada, is used to interpret paleoclimate, bracket alluvial fan ages, and provide constraints for faulting along the Newark Valley Fault Zone (NVFZ). We distinguish two age groups of shoreline deposits which are correlative to specific altitudes of lake highstands. Four soil chronosequences were examined within the main lake basin allowing for comparison of local influences on soil development such as dominant wind direction, minor parent material differences, and age. Comparisons of soil morphology and four soil indices were used to distinguish relative ages and to correlate soil development to dated deposits within Newark Valley and elsewhere in the Great Basin. The last highstand in Newark Valley dates to 13,780 14C yr B.P and typical soil development into them (Av/Bwk1/Bwk2/2Coxk, stage I+ Carbonate morphology) differs markedly from the older shorelines (Av/Bwk1/Bwk2/2Bkm/2Coxk, stage III+ Carbonate morphology) that are likely OIS 6 in age. Twenty-seven soil profiles into these deposits show the two ages of deposits can be correlated around the basin, though variations among the study locations suggest a suite of soils is preferable to establish correlations and viable age estimates.

The older, higher shoreline deposits extend 20m above the younger shorelines and suggest an effectively wetter climate during OIS 6 than in OIS 2. These older shorelines also provide constraints on alluvial fan ages and rates and recency of faulting in Newark Valley. Three mappable fan units (Qf1, <~15ka; Qf2 ~15ka to ~130 - 190ka, OIS 4?; and Qf3, ≥~130 - 190ka, ≥OIS 6) are present in the valley but only Qf2 and Qf3 are offset by faults. Based on possible fan ages and offsets, tentative slip rate estimates range from ~0.05 to ~0.1 mm/yr.