K-Ar ages and paleomagnetic directions from the Lathrop Wells Volcanic Center, southwestern Nevada; an evaluation of polycyclic volcanism

Abstract

Paleomagnetic data suggest that there may be two eruptive units at the Lathrop Wells volcanic center, Nevada. The measured directions of remanent magnetization for the two units are 51.5° inclination, 2.2° declination, and 51.4° inclination, 354.5° declination. The difference in the paleomagnetic field directions of 4.7°, is significant at the 99.98 percent confidence level. The observed angular difference between the two mean directions suggests a minimum age difference between the eruptive events of about 100 years. Weighted means of K-Ar ages on these two units (Ql3 = 131 ± 10 ka; Qls = 115 ± 12 ka), though reversed from the mapped stratigraphic succession, are not significantly different at the 95 percent confidence level. Based on statistical analysis, the difference in age between the flows is less than or equal to approximately 30 k.y.Moreover, the K-Ar ages from the flow units Qls and Qls are consistent with the reported uranium series dating, uranium-trend chronology, and ^Cl and 3He exposure ages of the surficial units in the Yucca Mountain region.

Neogene tephra correlations in eastern Idaho and Wyoming: Implications for Yellowstone hotspot-related volcanism and tectonic activity

“…This was necessary because of the high probability of contamination of the feldspar population due to reworking. Statistical analysis of the results from multiple analyses of grains was performed using a weighted-average technique (Taylor, 1982;Turrin et al, 1998).…”

Late Pleistocene ages for the most recent volcanism and glacial‐pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

“…However, despite several geochronologic studies over the last three decades, the timing of the most recent volcanism at BPVF has been poorly resolved due to large uncertainties for the late Pleistocene dates derived using K‐Ar and 40 Ar/ 39 Ar techniques coupled with an uncertain volcanic stratigraphy. Due to their eruption at the boundary between the Sierra Nevada Range and the Owens Valley graben, a number of BPVF lavas are interbedded with Quaternary moraine deposits from alpine glaciers [e.g., Dalrymple , ; Gillespie et al ., ; Turrin and Gillespie , ], and in several cases flowed to lower elevations where they were subsequently modified by a pluvial body of water [ Jayko and Bacon , 2008]. Hence, a reliable eruption chronology for the lavas and pyroclastic deposits at BPVF also provides a unique opportunity for dating local geologic deposits and geomorphic features that reflect Quaternary paleoclimate.…”

“…Past geochronologic studies have established that BPVF volcanism is Pleistocene in age, with the most recent eruptions occurring during the late Pleistocene (∼12–126 ka), but a precise and reliable chronology for the youngest eruptions has not been constrained. Dating of BPVF lavas and lava‐hosted xenoliths using K‐Ar, 40 Ar/ 39 Ar, and (U‐Th)/He methods has yielded dates between ∼1.2 Ma and <0.1 Ma [ Cox et al ., , 1963b; Dalrymple , ; Gillespie , ; Gillespie et al ., ; Turrin and Gillespie , ; Martel et al ., ; Dorn et al ., ; Blondes et al ., 2007, ]; most of these reported K‐Ar and 40 Ar/ 39 Ar dates are compiled by Connor and Conway [2000] and Bierman et al . [].…”