Potassium-Argon Dates of Three Pleistocene Interglacial Basalt Flows From the Sierra Nevada, California

Dalrymple, G. Brent

doi:10.1130/0016-7606(1964)75[753:pdotpi]2.0.co;2

Cited by 34 publications

(23 citation statements)

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“…More modern studies (Blackwelder, 1931;Putnam, 1950;Sharp and Birman, 1963;Dalrymple, 1964;Sharp, 1968Sharp, , 1972Burke and Birkeland, 1979;Gillespie, 1982;Clark and Gillespie, 1994) further subdivided the Pleistocene units, and reported one or more minor Holocene(?) stages.…”

Section: Owens Lake History and Sierra Nevada Glaciationmentioning

confidence: 96%

Synthesis of the paleoclimatic record from Owens Lake core OL-92

Smith¹,

Bischoff²,

Bradbury³

1997

An 800,000-Year Paleoclimatic Record From Core OL-92, Owens Lake, Southeast California

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During much of the late Quaternary, Owens Lake overflowed into one or more of four successively lower-elevation basins. Most of the water came from the high, eastern slopes of the southern Sierra Nevada, and changes in the volumes of that water reflect a dominant climatic cycle of ~100 k.y.Variations in the inflow to, and outflow from, Owens Lake since ca. 800 ka left biological, chemical, mineralogical, and geophysical evidence in the sediments of those changes. Biological evidence includes fossil ostracodes, diatoms, fish, and mollusks (and δ 18 O data from their shells) which indicate fresh or brackish lake water on the basis of their modern habitats. Fossil pollens indicate ~20 regional vegetation cycles during the same period. Chemical evidence of high inflow and, commonly, outflow volumes is provided by the low inorganic-and organic-C content of some sediments, reflecting short lake-water residence times; long residence times produced higher and more variable quantities of these components. Mineralogical variations in illite/smectite ratios indicate changes in weathering processes and glacial comminution. High magnetic susceptibility correlates with other criteria that indicate high runoff.Between 810 ka and 645 ka, Owens Lake was fresh, several meters deep, and depositing silt with a few beds of sand; it supported a flora and fauna now found in fresh, sometimes very cool, waters. (Note that most geologic ages describing the OL-92 chronology have been rounded to the nearest 5 or 10 ka.) A shallow-but-freshwater lake may have been the result of accelerated sedimentation during an earlier (>800 ka) glaciation in the Sierra Nevada, choking the basin with sediment nearly to its spillway level. Between 645 ka and 450 ka, the lake was probably even shallower, depositing beds of coarse to fine sand, but overflowing periodically allowing its water to remain fresh. Between 450 ka and 5 ka, Owens Lake was mostly deep, alternating between spilling and being closed part of the time. It deposited silt and clay on its floor, yet underwent detectable variations in salinity caused by climate changes; this part of the record is the most easily interpreted and constitutes the main basis for comparing this paleoclimatic record with other long records. From 5 ka to A.D. 1913, when the Owens River was diverted into an aqueduct, Owens Lake was shallow (~2 m to ~15 m), moderately saline (~5% to <15% salts), and depositing oolites. After 1913, the lake desiccated.

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Section: Owens Lake History and Sierra Nevada Glaciationmentioning

confidence: 96%

Synthesis of the paleoclimatic record from Owens Lake core OL-92

Smith¹,

Bischoff²,

Bradbury³

1997

An 800,000-Year Paleoclimatic Record From Core OL-92, Owens Lake, Southeast California

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“…The intercalation of basalt flows between two late Pleistocene glacial moraines in Sawmill Canyon (Figure 1) affords a valuable opportunity to obtain absolute limits on the age of Sierran glacial stages and to strengthen correlations with the better understood chronology of continental glaciation [Dalrymple, 1964a]. The intercalation of basalt flows between two late Pleistocene glacial moraines in Sawmill Canyon (Figure 1) affords a valuable opportunity to obtain absolute limits on the age of Sierran glacial stages and to strengthen correlations with the better understood chronology of continental glaciation [Dalrymple, 1964a].…”

Section: Fig 1 Map Showing Sample Locations In Sawmill Canyon Glacmentioning

confidence: 99%

“…Site SC-115 is on the same outcrop from which Dalrymple [1964a] obtained his basalt samples KA970 and KA970A (Figure 1). SC-115 and SC-118 underlie moraine II.…”

Section: We Sampled the Basalt At Several Locations In Sawmill Canyonmentioning

confidence: 99%

“…The granodiorite of the Spook pluton is composed of approximately 24% quartz, 19% K-feldspar, 48% plagioclase, 6% biotite, and lesser amounts of hornblende and accessory minerals [Moore, 1963]. Dalrymple [1964a] observed that some of the perthitic Kfeldspar in the xenoliths had been altered to sodic sanidine. Some grains exhibit microcline twinning.…”

Section: Petrographymentioning

confidence: 99%

“…Site SC-115 was the same outcrop sampled by Dalrymple [1964a] for K/Ar dating of the basalt underlying the glacial Extraction temperatures are given in the first column. The second column shows the total 4øAr released in each step, including blank 4øAr (third column).…”

Section: Xenolith Samples From Sites $C-115 and $C-118mentioning

confidence: 99%

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Eruption age of a ∼100,000‐year‐old basalt from ⁴⁰Ar‐³⁹Ar analysis of partially degassed xenoliths

Gillespie¹,

Huneke²,

Wasserburg³

1984

J. Geophys. Res.

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We have applied 40Ar‐39Ar dating, using stepwise thermal extraction of Ar, to five potassium‐rich granitic xenoliths and their host basalt from Sawmill Canyon in the Sierra Nevada, California. Previous K/Ar analyses showed the age of the basalt to be roughly 100,000 years or less. The xenoliths, which had accumulated large amounts of radiogenic 40Ar since their crystallization ∼100 m.y. ago, were partially degassed upon their inclusion in the basaltic magma. Ar released from the xenoliths in the laboratory at temperatures substantially below the melting temperature of the basalt, was created since the host magma cooled. Isotopic compositions of Ar released from the xenoliths in several extraction steps at temperatures below ∼900°C were colinear in 36Ar/40Ar versus 39Ar/40Ar diagrams and defined isochrons giving a mean age of degassing of 119,000±7000 (2σ) years. 40Ar extracted at higher temperatures included ancient radiogenic 40Ar that was never diffused from the xenoliths during immersion in the magma. This 40Ar caused an increase in the apparent age for the high‐temperature extractions. The high precision of the eruption age determined by this method is comparable to that obtained elsewhere by conventional K/Ar dating of sanidine. 40Ar‐39Ar analysis of granitic xenoliths to date young basaltic lava flows may prove to yield results superior to those found from analysis of the lava itself. Establishing the age of eruption of the basalt flow in Sawmill Canyon establishes age limits for two Sierran glaciations which left moraines stratigraphically above and below the lava. Thus the younger glaciation must be Wisconsin; the older must be pre‐Wisconsin in age.

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

Woolford

2015

Geochem Geophys Geosyst

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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.

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Potassium-Argon Dates of Three Pleistocene Interglacial Basalt Flows From the Sierra Nevada, California

Cited by 34 publications

References 0 publications

Synthesis of the paleoclimatic record from Owens Lake core OL-92

Synthesis of the paleoclimatic record from Owens Lake core OL-92

Eruption age of a ∼100,000‐year‐old basalt from ⁴⁰Ar‐³⁹Ar analysis of partially degassed xenoliths

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

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Potassium-Argon Dates of Three Pleistocene Interglacial Basalt Flows From the Sierra Nevada, California

Cited by 34 publications

References 0 publications

Synthesis of the paleoclimatic record from Owens Lake core OL-92

Synthesis of the paleoclimatic record from Owens Lake core OL-92

Eruption age of a ∼100,000‐year‐old basalt from 40Ar‐39Ar analysis of partially degassed xenoliths

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

Contact Info

Product

Resources

About

Eruption age of a ∼100,000‐year‐old basalt from ⁴⁰Ar‐³⁹Ar analysis of partially degassed xenoliths

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