Samples were analyzed using the handheld portable X-ray fluorescence (pXRF) analyzer as part of a study examining the occurrence chromium and of natural and anthropogenic hexavalent Chromium, Cr(VI) in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). Relative concentrations for 18 elements of interest were measured on the less than 2mm and sized- fraction splits of the 36 field samples. Greater than 20 percent of the samples analyzed using pXRF also have Contract Laboratory results for comparison. These pXRF results are part of a data release including grain size distribution, photographic, and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as Scanning Electron Microscopy analyses on select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board.

Heavy and light mineral separates were extracted from the 36 collected field samples following a USGS procedure (Strong and Driscoll, 2016) and analyzed using the handheld portable X-ray fluorescence (pXRF) analyzer as part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI), in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). These pXRF results are part of a data release including grain size distribution, photographic and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as Scanning Electron Microscopy analysis on select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board.

Heavy and light mineral separates were extracted from the 36 collected field samples following a USGS procedure (Strong and Driscoll, 2016) and analyzed using the handheld portable X-ray fluorescence (pXRF) analyzer as part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI), in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). These pXRF results are part of a data release including grain size distribution, photographic and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as Scanning Electron Microscopy analysis on select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board.

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 core material from existing auger- or sonic-drilled monitoring wells in Hinkley Valley and the adjoining Water Valley, 140 kilometers (km) northeast of Los Angeles, California, were measured as part of an investigation of naturally-occurring and anthropogenic hexavalent chromium, Cr(VI), concentrations in local 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 from outcrops or from colluvium eroded from nearby outcrops and were broken to expose fresh surfaces whenever possible. Core material was measured within the screened interval of wells sampled for water-quality as part of the study, along with additional core material from other intervals of geologic or lithologic interest to the study. Some measurements of core material were made on materials from selected geologic settings including oxide-rich zones formed near lithologic and redox contacts, groundwater discharge deposits, and weathered bedrock. Measurements were made on 155 samples of alluvium and rock, and archived core material from 69 monitoring well sites, located over an approximately 200 square km area between March 2015 and May 2018. Measurements on National Institute of Standards and Technology (NIST) and U.S. Geological Survey standard reference materials (available in a separate child page associated with https://doi.org/10.5066/P9CU0EH3) indicated the pXRF was sufficiently accurate for chromium and selected trace elements for the intended purpose of the dataset. Standard reference material indicated a need to adjust instrument beam times to optimize measurements of chromium. Measurements on a silica dioxide blank showed consistent clean (few to no measurable elements) data.

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 core material from existing auger- or sonic-drilled monitoring wells in Hinkley Valley and the adjoining Water Valley, 140 kilometers (km) northeast of Los Angeles, California, were measured as part of an investigation of naturally-occurring and anthropogenic hexavalent chromium, Cr(VI), concentrations in local 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 from outcrops or from colluvium eroded from nearby outcrops and were broken to expose fresh surfaces whenever possible. Core material was measured within the screened interval of wells sampled for water-quality as part of the study, along with additional core material from other intervals of geologic or lithologic interest to the study. Some measurements of core material were made on materials from selected geologic settings including oxide-rich zones formed near lithologic and redox contacts, groundwater discharge deposits, and weathered bedrock. Measurements were made on 155 samples of alluvium and rock, and archived core material from 69 monitoring well sites, located over an approximately 200 square km area between March 2015 and May 2018. Measurements on National Institute of Standards and Technology (NIST) and U.S. Geological Survey standard reference materials (available in a separate child page associated with https://doi.org/10.5066/P9CU0EH3) indicated the pXRF was sufficiently accurate for chromium and selected trace elements for the intended purpose of the dataset. Standard reference material indicated a need to adjust instrument beam times to optimize measurements of chromium. Measurements on a silica dioxide blank showed consistent clean (few to no measurable elements) data.

Samples were submitted for contract laboratory analysis as part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI) in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). These Contract Lab results are part of the data release including grain-size distribution, photographic and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as Scanning Electron Microscopy analysis on select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board.

Splits of the less than 38 micron size fraction were processed to make oriented clay mounts and analyzed using X-ray diffraction (XRD) as part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI) in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). These clay mineralogy XRD results are part of a data release including grain size distribution, photographic, and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board. Results are provided in this data release organized by analysis type.

Splits of the less than 38 micron size fraction were processed to make oriented clay mounts and analyzed using X-ray diffraction (XRD) as part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI) in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). These clay mineralogy XRD results are part of a data release including grain size distribution, photographic, and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board. Results are provided in this data release organized by analysis type.

This data release is part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI) in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). The data release includes grain size distribution, photographic, and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as Scanning Electron Microscopy analysis on select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board. Results are provided in this data release organized by analysis type.

Splits of samples were prepared of heavy mineral separates and bulk separates less than 2mm for analysis using X-ray diffraction (XRD) and results were interpreted to identify mineral components as part of a study examining the occurrence of chromium and natural and anthropogenic hexavalent Chromium, Cr(VI), in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). These XRD results are part of a data release including grain size distribution, photographic, and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board. Results are provided in this data release organized by analysis type.