OFR 97-492: Las Vegas Quadrangle NURE HSSR Study
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This page is currently being rewritten to the Version 1.41 format.
[See History of NURE HSSR Program for a summary of the entire program.]
The Lawrence Livermore Laboratory (LLL) was responsible for the collection and analysis of NURE samples from the Las Vegas quadrangle. Contractors were hired to collect the reconnaissance samples. Bendix Field Engineering Corporation collected sediment and surface water samples, and the University of Nevada-Desert Research Institute collected ground water samples. Between February of 1977 and January of 1978, a total of 1,576 sediment samples (1,494 reconnaissance samples, 12 site duplicate samples, 69 analytical duplicate samples, and 1 analytical split of a site duplicate sample) and 106 water samples (106 reconnaissance samples) were collected for the LLL Las Vegas Quadrangle NURE Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) study. LLL crews resampled 34 sediment sites (34 samples) as part of their quality assurance program from March - November of 1977. The corresponding quality assurance sample number was cross referenced to the original reconnaissance sample number. All of these samples were analyzed by LLL for uranium and several other elements and the analytical data were released in the LLL HSSR Las Vegas quadrangle GJBX-123(78) report.
The following is a list of all sample types (including duplicates) collected in the Las Vegas quadrangle and included in the NEW-FORMAT NURE data files.
| Sediment Sample Type | Number of Samples | Water Sample Type | Number of Samples |
|---|---|---|---|
| Wet Streams | 142 | Wells | 26 |
| Dry Streams | 1,468 | Springs | 80 |
| Total Sediments | 1,610 | Total Waters | 106 |
These Las Vegas quadrangle samples were analyzed by one or more of the following methods:
Sediment Samples
Water Samples
The data in the NEW-FORMAT NURE data files consist of records from the LLL GJBX-123(78) report. The coordinate locations for quality-assurance samples were checked against the coordinates for the cross-referenced original sites and differences were noted in the REFORMAT comment field.
Unlike data from other laboratories, the original LLL sediment data files do not indicate when elemental concentrations fall below analytical determination limits. Other laboratories usually report these values as "less than the lower analytical determination limit" (represented by a negative number). Negative values were added to the NEW-FORMAT NURE data files during the reformatting process based upon the approximate lower limits of detection given in Table 2 of the GJBX-123(78) report.
The original LLL files also contained numerical estimates of the absolute error associated with each elemental concentration. These data were not included in the NEW-FORMAT NURE data files but were placed into additional supplemental data files. The Absolute Error Extra Data Format is explained later in this document.
The NURE HSSR data are now available online in two databases: The sediment database (also includes data for soils and some rocks) at http://tin.er.usgs.gov/nure/sediment/ and the water database at http://tin.er.usgs.gov/nure/water/. From these two websites, NURE HSSR data can be selected, examined, summarized, and downloaded by political boundaries (State and County), by quadrangle (1:250,000-scale, 1:100,000-scale, and 1:63,360-scale for Alaska or 1:24,000-scale for the Lower 48 States), and by hydrologic unit (drainage region, subregion, river basin, or sub-basin). Selected data can be downloaded as a dBase file, a shapefile, an HTML table, or ASCII text (tab- or comma-delimited).
Las Vegas Quadrangle Sediment Data - 1,610 records
Las Vegas Quadrangle Water Data - 106 records
LLL Error Estimates Data for Sediment Analyses - lasvgasx.dbf.gz
LLL Error Estimates Data for Water Analyses - lasvgawx.dbf.gz
Users of past versions of the Las Vegas quadrangle sediment database have had problems with LLL data because the fields were blank when the element concentration fell below the lower analytical determination limits. This absence of the lower end of the data population was responsible for skewing the data in statistical and contouring programs to levels that were higher than expected. As described above, the NEW-NURE FORMAT attempts to solve this problem by replacing those blanks with "less than" values based on reported lower determination limits.
In 1982, Bendix Field Engineering Corporation of Grand Junction, Colorado prepared a summary evaluation of the Las Vegas quadrangle [PGJ/F-121(82)]. An additional 328 rock and 31 water samples were collected "to identify geologic environments and delineate areas that exhibit characteristics favorable for uranium deposits." All of the samples were analyzed for uranium oxide. In addition, rock samples were analyzed for equivalent K, U, and Th, and 321 were analyzed for up to 38 other elements. The water samples were analyzed for 29 constituents. These data were released only as microfiche appendices that accompany the summary report.
Explanations are only included here for fields unique to these files. For the explanation of common fields consult the On-Line Manual for New-Format NURE HSSR Data Files. After each field name is a format code. A format code of (N) means that the field is formatted as an Numeric field.
A statistical estimate of measurement uncertainty associated with quantifying the corresponding uranium concentration determined by Delayed-Neutron Counting Analysis. (expressed as a percentage of the uranium concentration found in field U_DN_PPM for sediment data or U_DN_PPB for water data in the NEW-NURE FORMAT data files).
(Where EL represents different element symbols.) A numerical estimate of the uncertainties associated with quantifying the corresponding elemental concentration determined by Neutron Activation Analysis. (expressed in the same concentration units as the element concentration found in the NEW-NURE FORMAT data files).
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Frequently Asked Questions Concerning NURE HSSR Data
Home Page: USGS National Geochemical Database - NURE HSSR data
Page written by Andrew W. Holt and Steven M. Smith
Contact: Steven M. Smith (smsmith@usgs.gov)
Version 1.10: July 29, 1999
Version 1.20: August 07, 2000
Version 1.30: September 11, 2001
Version 1.40: January 13, 2006
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