Filters: Tags: Joshua tree (X)
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USGS Historical Quadrangle in GeoPDF.
Thirty-eight dated packrat middens were collected from upper desert (930–1357 m) elevations within Joshua Tree National Park near the ecotone between the Mojave Desert and Colorado Desert, providing a 30 ka record of vegetation change with remarkably even coverage for the last 15 ka. This record indicates that vegetation was relatively stable, which may reflect the lack of invasion by extralocal species during the late glacial and the early establishment and persistence of many desert scrub elements. Many of the species found in the modern vegetation assemblages were present by the early Holocene, as indicated by increasing Sørenson's Similarity Index values. C4 grasses and summer-flowering annuals arrived later...
Categories: Publication;
Types: Citation;
Tags: Holocene,
Joshua tree,
Packrat middens,
Pleis,
juniper
USGS Historical Quadrangle in GeoPDF.
These data on the concentrations of 27 selected elements were collected using a field portable (handheld) X-ray fluorescence (pXRF) instrument (Groover and Izbicki, 2016) equipped with a 4-watt Ta/Au X-ray tube on samples of 1) surficial alluvium, 2) rock, and 3) archived core material and drill cuttings from monitoring wells across an approximately 14,300 square kilometer area in the western part of the Mojave Desert, between 60 to 210 kilometers (km) northeast of Los Angeles, California. These samples were measured using a pXRF as part of a regional-scale investigation of naturally-occurring trace elements (including arsenic, chromium, and uranium) dissolved in groundwater (Groover and Izbicki, 2018), and a local-scale...
Types: Map Service,
OGC WFS Layer,
OGC WMS Layer,
OGC WMS Service;
Tags: Arsenic,
Barstow,
California (CA),
Chromium,
El Mirage,
USGS Historical Quadrangle in GeoPDF.
These data were collected using field portable (handheld) X-ray fluorescence (pXRF) equipped with a 4-watt Ta/Au X-ray tube. Samples of surficial alluvium, rock, and archived drill cuttings from monitoring wells in the western part of the Mojave Desert, 60 to 210 kilometers (km) northeast of Los Angeles, California, were measured using as part of an investigation of naturally-occurring trace elements dissolved in groundwater. Surficial alluvium samples were collected from small stream channels draining distinct geologic units, or from previously mapped river deposits, and generally consisted of silt, sand, and granules to small pebbles. Twigs and other detritus were removed prior to measurement. Rocks were collected...
These data were collected using field portable (handheld) X-ray fluorescence (pXRF) equipped with a 4-watt Ta/Au X-ray tube on two National Institute of Standards and Technology (NIST) certified standard reference materials 2710a and 2711a, a U.S. Geological Survey (USGS) certified standard reference material BHVO-2, and a silicon dioxide blank. These quality assurance data were collected as part of detailed pXRF studies in Hinkley and Water Valleys, 140 kilometers (km) northeast of Los Angeles, California, and as part of a regional geochemical survey in the western Mojave Desert, between 60 to 210 km northeast of Los Angeles. Measurements on National Institute of Standards and Technology (NIST) and U.S. Geological...
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