OFR 97-492: Llano Quadrangle NURE HSSR Study

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National Geochemical Database—Reformatted Data from the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) Program

By Steven M. Smith
Version 1.40 (2006)

Brief History and Description of Data

[See History of NURE HSSR Program for a summary of the entire program.]

ORGDP: Plainview, Lubbock, and Big Spring Quadrangles Wide-Spaced Uranium Geochemical Survey
Early in the NURE Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) program, personnel from the Oak Ridge Gaseous Diffusion Plant (ORGDP) sampled several areas with a wide-spaced sample coverage (Phase I sampling). Phase I samples were generally collected in stream basins averaging 250 square kilometers in area and from wells at about a 16 km spacing. The purpose of the Phase I sampling was to define uranium provinces that warranted additional sampling at a higher density (Phase II sampling). These samples were sent to the ORGDP and analyzed for uranium and other elements. For many 1:250,000-scale 2-degree quadrangles, Phase I samples were included with later Phase II samples and utilized in the individual HSSR basic data quadrangle reports. Some Phase I samples were never utilized in basic data quadrangle reporting. ORGDP issued the Wide-Spaced Uranium Geochemical Survey in the Plainview, Lubbock, and Big Spring Quadrangles, Texas GJBX-73(78) report for several of these Phase I samples. This report includes data for 287 stream-sediment, 1 rock, 529 water, and 161 botanical samples collected between July and November of 1976 in the Plainview, Lubbock, and Big Spring quadrangles. Data for one stream-sediment and three water samples collected in the Llano quadrangle were also included in this report.

ORGDP: Texas Wide-Spaced Uranium Geochemical Survey
ORGDP issued the Hydrogeochemical and Stream Sediment Wide-Spaced Sample Basic Data Release for Texas GJBX-131(81) report for several of these Phase I samples. This report includes data for 261 stream sediment and 406 water samples collected during 1976-77 in the Abilene, Austin, Brownwood, Corpus Christi, Del Rio, Eagle Pass, Houston, Llano, San Angelo, Sonora, and Waco quadrangles. The Wide-Spaced Sample Basic Data Release for Texas GJBX-131(81) report only contains data tables for Phase I samples; no explanatory text accompanies this report. The Wide-Spaced Sample Basic Data Release for Texas GJBX-131(81) report includes data records for 99 stream-sediment and 172 water samples collected within the borders of the Llano quadrangle.

Llano Texas Pilot Geochemical Survey
In 1976, a pilot geochemical survey was undertaken to sample a small but regionally and geologically representative area to prepare for a subsequent reconnaissance geochemical survey of the uranium in Central Texas. A total of 134 stream-sediment, 6 soil, 158 water, and 267 plant samples were collected between February and March of 1976 from parts of the Llano, Brownwood, and Austin quadrangles. Of these, 75 stream-sediment, 5 soil, 84 water, and 133 plant samples were collected within the borders of the Llano quadrangle. These samples were analyzed by the ORGDP for uranium and other elements and the analytical data were released as the Llano, Texas Pilot Geochemical Survey GJBX-36(76) report.

ORGDP: Llano Quadrangle
Totals of 653 stream-sediment and 161 ground-water samples were collected from the Llano quadrangle as part of the ORGDP Llano Quadrangle NURE Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) study. Field sampling was conducted between April and May of 1980. These samples were analyzed by the ORGDP for uranium and other elements. The analytical data were released as the Llano Quadrangle NURE HSSR study GJBX-39(81) report.

Summary Tables
The following is a list of NURE sample types collected in the Llano quadrangle.

Summary of Llano quadrangle sample types.
Sediment Sample Type No. of Samples Water Sample Type No. of Samples Plant Sample Type No. of Samples
Wet Streams 369 Streams 151 Deciduous Tree (6 types) 93
Dry Streams 459 Wells 257 Conifer (1 type) 37
Soils 5 Springs 9 Bush (1 type) 1
        Unspecified 2
Total Sediments 833 Total Waters 417 Total Plants 133

These Llano quadrangle samples were analyzed by one or more of the following methods:

Sediment Samples

Water Samples

Plant Samples


Discussion of the Reformatting Process for Llano Quadrangle

The Llano quadrangle sediment and water data consist of reformatted records from the Llano Area Pilot Geochemical Survey GJBX-36(76) report, the Plainview, Lubbock, and Big Spring Quadrangles Wide-Spaced Uranium Geochemical Survey GJBX-73(78) report, Texas Wide-Spaced Survey GJBX-131(81) report, and the Llano Quadrangle NURE HSSR study GJBX-39(81) report. The following problems were found and addressed during the comparison and reformatting stages for the Llano quadrangle data:

Sediment Records

  1. The Plainview, Lubbock, and Big Spring Quadrangles Wide-Spaced Uranium Geochemical Survey GJBX-73(78) report included data for one sediment sample apparently collected in the Llano quadrangle.
  2. 143 sediment records were not included in the original digital data file for the Llano quadrangle. These records were manually entered from the Llano Quadrangle HSSR Study GJBX-39(81) report.
  3. Unlikely sample collection dates were found for five samples. These dates were removed from the SAMPDAT field. For each record, the original SAMPDAT value and the most likely correct value was added as a comment to the REFORMAT field.
  4. Twenty-five stream-sediment samples in this quadrangle share the same latitude-longitude coordinates with one or two other samples (12 distinct coordinate sites). It is unclear whether this represents sets of samples collected at the same twelve sites or single samples collected at separate sites so close together that the coordinate precision was insufficient to distinguish locations.
  5. The latitude and longitude coordinates for 3 stream-sediment samples collected within the Llano quadrangle were not found in the data during the reformatting process. The records for these 3 samples cannot be retrieved on a geographical basis.

Water Records

  1. The Plainview, Lubbock, and Big Spring Quadrangles Wide-Spaced Uranium Geochemical Survey GJBX-73(78) report included data for 3 water samples apparently collected in the Llano quadrangle.
  2. Thirty water records were not included in the original digital data file for the Llano quadrangle. These records were manually entered from the Llano Quadrangle HSSR Study GJBX-39(81) report.
  3. Fifteen sample records contained an invalid value of 'G', or 'P' for the well depth confidence (WLDPTCNF). It appears that the column was miscoded with values from an adjacent field on the original field note sample sheet. The correct values were not found. These values were removed from the WLDPTCNF field and added as a comment to the REFORMAT field.
  4. One sample record contained an invalid code for the well casing (WELLCASE) of 'A'. This value was removed from the WELLCASE field and added as a comment to the REFORMAT field.
  5. Unlikely sample collection dates were found for three samples. These dates were removed from the SAMPDAT field. For each record, the original SAMPDAT value and the most likely correct value was added as a comment to the REFORMAT field.
  6. Two separate water samples in this quadrangle have the same latitude-longitude coordinates. It is unclear whether this represents a pair of samples collected at the same site or samples collected at separate sites so close together that the coordinate precision was insufficient to distinguish.
  7. Two well-water samples originally had a latitude of exactly 31°N, the dividing line between the Llano quadrangle and the Big Spring quadrangle. The coordinates for these samples were changed slightly to values found in tables on microfiche within the Llano Quadrangle HSSR Study GJBX-39(81) report or the Llano Area Pilot Geochemical Survey GJBX-36(76) report. This slight change places these samples clearly in the Llano quadrangle.
  8. The latitude and longitude coordinates for 8 water samples collected within the Llano quadrangle were not found in the data during the reformatting process. The records for these 8 samples cannot be retrieved on a geographical basis.

Plant Records

  1. The Llano Area Pilot Geochemical Survey GJBX-36(76) report includes data for 133 plant samples collected in the Llano quadrangle.
  2. At the time of this Open-File release (v. 1.41), the ORGDP plant data have not been completely reformatted and released for downloading. See the ORGDP Plant Data page for a more detailed description of the data format and plant data availability.

Download The Data

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 web sites, 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).

Llano Quadrangle Sediment Data - 830 records
Llano Quadrangle Water Data - 409 records


Notes for Data Users

The ORGDP water samples were reportedly collected in the field without any filtering or acidification. (See the SAMPTYP coding explanation in the On-Line Manual for USGS-Reformatted NURE HSSR Data Files for descriptions of different Sample Types). However, the samples were filtered later in the laboratory through a 0.45 micron membrane filter before analysis. Therefore, the samples were not true "untreated water" samples and the analytical data may not be directly comparable for other quadrangle water samples of the same SAMPTYP when collected by a different laboratory. Since this was the standard procedure for Oak Ridge, water data from other Oak Ridge quadrangles should be comparable.

Latitude-longitude coordinates were reported in the original data files, as decimal degrees, to only 3 decimal places. Therefore, the precision of these coordinates is limited to +/- 0.001 degrees or +/- 3.6 seconds. This translates to a minimum precision of +/- 364 feet (111 m) for latitude values and between +/- 317 feet (97 m) to +/- 300 feet (91 m) for longitude values (calculated at latitudes of 30° and 35°N, respectively.)

One stream-water and three stream-sediment samples collected in the Llano quadrangle were not analyzed by any method.


Other NURE Geochemical Data for the Llano Quadrangle

Llano Quadrangle NURE Summary
A summary evaluation of the Llano quadrangle was prepared by the Bendix Field Engineering Corporation [PGJ/F-122(82)]. Geochemical data were reported in tables on microfiche for 16 water samples analyzed for uranium only, and 60 rock samples analyzed for uranium plus 40 additional elements. The Town Mountain Granite is identified as favorable for pegmatite uranium deposits.


Llano Quadrangle NURE Bibliography


Links Within Open-File Report 97-492

Back to Texas NURE data
Frequently Asked Questions Concerning NURE HSSR Data
Home Page: USGS National Geochemical Database - NURE HSSR data


Page written by Bryan G. Moravec and Steven M. Smith
Contact: Steven M. Smith (smsmith@usgs.gov)
Version 1.20: August 07, 2000
Version 1.30: September 11, 2001
Version 1.41: February 23, 2006

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URL: https://pubsdata.usgs.gov/pubs/of/1997/ofr-97-0492/quad/q_llano.htm
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