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

Abstract

The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an 1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36 Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36 Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at 17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at 17 ka, and produced a lava flow field covering 35 km 2 . The late Pleistocene 36 Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

Geochemical studies on rock varnish and petroglyphs in the Owens and Rose Valleys, California

“…The Big Pine volcanic field is of Quaternary age, with the youngest flows occurring near Aberdeen. Here, six distinct flow units have been dated to the late Pleistocene by 3 He and 36 Cl techniques [ 48 , 50 ]. We measured the areal density of Mn and Fe on the flow surfaces and sampled varnish from four of these flow units at the same locations sampled by Vazquez and Woolford [ 50 ]: Units Qba (sample CLS-03, 40 ka), Qbbs (CLS-06, 27 ka), Qbac (CLS-04, 17 ka), and Qbtc (CLS-05, 17 ka).…”

“…Given the relative success of our approach in Saudi Arabia, we intended to examine the possibility of extending it to other regions. We chose the southern Owens Valley and the adjacent Rose Valley, both parts of the Mojave Desert in southern California, as an initial test site because of its prominent role in the scientific study of rock varnish [e.g., 2 , 19 ], the existence of radiometrically dated rock surfaces [e.g., 19 , 28 , 48 – 50 ], and the presence of well-documented rock art [e.g., 24 , 51 ], including a large corpus of dated petroglyphs in this and nearby regions [ 36 , and references therein, 52 ]. The rock art in this area has been the subject of vigorous–and sometimes acerbic–debate over decades, both with regards to its meaning and function [e.g., 24 , 51 , 53 – 59 ] and its time of creation [e.g., 24 , 28 , 36 , 52 , 54 , 55 , 60 , 61 – 63 ].…”

Evidence of Rapid Phenocryst Growth of Olivine During Ascent in Basalts From the Big Pine Volcanic Field: Application of Olivine‐Melt Thermometry and Hygrometry at the Liquidus

“…BP‐11, shown in red (this study), contains a mantle xenolith. Cosmogenic 36 Cl ages and whole‐rock 40 Ar/ 39 Ar ages are from Vazquez and Woolford (2015) and Blondes et al (2008), respectively. The inset map shows the location of the Big Pine volcanic field along the western margin of the Basin and Range province.…”

“…Mantle xenolith localities from Wilshire et al (1988) and Beard and Glazner (1995) are shown in Figure 1. The BP volcanic field has been active since 1.2 Ma (Blondes et al, 2007, 2008), with the youngest eruptions (17, 27, and 40 ka) identified using cosmogenic 36 Cl dating (Vazquez & Woolford, 2015). All BP basalts, regardless of age, have chondrite‐normalized trace‐element patterns that display enrichments in fluid‐mobile elements (e.g., Ba), which is consistent with a subduction modified lithospheric mantle source (e.g., Blondes et al, 2008; Gazel et al, 2012; Ormerod et al, 1988, 1991; Putirka et al, 2012).…”

A Multidisciplinary Investigation Into the Eruptive Style, Processes, and Duration of a Cascades Back-Arc Tholeiitic Basalt: A Case Study of the Brushy Butte Flow Field, Northern California, United States

“…A method that has proved useful for providing ages on young flows in arid environments that lack extensive vegetation cover and erosion is the 36 Cl cosmogenic surface-exposure dating (e.g., Vazquez and Woolford, 2015;Downs et al, 2018;Downs et al, 2019;Stelten et al, 2018;Stelten et al, 2020;Bromley et al, 2019). We utilized the 36 Cl cosmogenic method (see Supplementary Material for details on sample collection and analysis) for the Brushy Butte flow field to determine its emplacement age, and we couple this with 40 Ar/ 39 Ar ages of surrounding older tholeiitic basalts to better understand the eruptive history of volcanism prior to eruption of the Brushy Butte flow field.…”