Cooperating agencies: Southern Nevada Water Authority and Virgin Valley Water District
Author or compiler: Van S. Williams
Map elements were visually checked by the author for overshoots, undershoots, duplicate features, and other errors. The report is preliminary and has not been thoroughly reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. The map was reviewed by another geologist for consistency with basic geologic principles and general conformity to USGS mapping standards.
This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Data is complete: no features were eliminated or generalized. There is no cross section and the ARC/INFO database lacks a unit properties table, although unit properties are described in the text explanation. A base map coverage is not included but is available separately.
Lines were primarily positioned by photointerpretation of aerial photographs using a PG-2 photogrammetric plotter that rectified the position and transferred it to a basemap. Lines were digitized from the basemap using a digitizer tablet with resolution of 0.001 inch. Additional lines and point observations were added in the field using positions determined by a PLGR-95 GPS unit with accuracy of about 10 meters. Most positions on the map are estimated to be accurate closer than 30 m horizontally. There is no elevation data in the database.
The Mesquite geologic database was compiled using the GSMCAD public domain program (USGS Open-File Report 96-007). It was exported to ARC/INFO using the GSMCAD export function to create ARC generate ASCII files and the gsmarc.aml program in ARC to convert the ASCII files to ARC coverages and build polygons. The gsmdraw.aml program was used in ARC to produce a graphics file of the colored map. In addition an explanation sheet was produced that includes a correlation of map units diagram, a list of map unit names and corresponding symbols, and an explanation of graphical map symbols.
The data is supplied in two formats. The first is the Microsoft-PC based native GSMCAD format and the second is a UNIX based ARC/INFO format.
DATABASE FILES - GSMCAD (DOS) ====================================
Text file of the description of map units and discussion of deposits, structure, and geologic history. Unit descriptions can be accessed by selecting map unit symbols displayed on screen.
Mesquite.lsf, .ndx, and .nod
The basic database components of line segment file, index file, and node file for the map. Units are degrees of latitude and longitude
Unitlist.lsf, .ndx, and .nod
The basic database components for the explanation sheet. Units are inches
File of plotting parameters for the map
File of plotting parameters for the explanation sheet
File of projection parameters for the Transverse Mercator projection of the 1:24,000 scale 7 1/2 ' Mesquite topographic quadrangle basemap
File of projection parameters for the Universal Transverse Mercator (zone 11) projection of a 1:100,000 scale 1 degree by 30 minute Overton sheet basemap. This can be used in GSMCAD to export UTM ground meters.
Text file listing all map unit symbols
Text file listing the explanations of the graphic symbols on the map
Text file listing all the age names, headers, and other text used on the correlation of map units diagram, except for the map unit symbols
Text file listing the names of map units
Text file containing selected field notes that are linked to the observation points in the map database (code 197)
Table of locations of selected water wells in the map area that can optionally be plotted on the map
DATABASE STRUCTURE - ARC/INFO ====================================
The database of the map consists of four coverages (root name Mesquite) and four additional info files. There are also four parallel coverages (rootname mesqexpl) that make up an explanation sheet with a correlation of map units diagram, list of map unit symbols and names, and an explanation of symbols.
Mesquitepoly coverage: Contains all contact lines and labelpoints for each polygon. The CODE item defines the significance of the lines as listed above and in the gsmcode.lut INFO file. The P1 item defines the category of polygon as listed above and in the gsmunit.lut INFO file.
Mesquiteline coverage: Contains faults, fold axis, and other non-contact lines. Faults that are contacts also appear in the Mesquitepoly coverage. The CODE item defines the significance of the lines as listed above and in the gsmcode.lut INFO file.
Mesquitesym coverage: Contains points recording observations, such as strike and dip of bedding, points for posting of dip or plunge values associated with the observation points, and arcs that draw out the symbols associated with the observation points and the symbols used to decorate certain lines. The CODE item defines the type of observation as listed above and in the gsmcode.lut INFO file. For rotational observations (CODE 200 to 299) the P1 item is the azimuth (strike) and the P2 item is the inclination (dip). The item gsmentity contains a unique number for each observation that ties together the observation point, posting point, and arcs that represent a single observation. That number is negative for the posting point to distinguish it from the observation point.
Mesquitetext coverage: Contains text points that define the position, rotation, and size of text to appear on the face of the map. Also includes arcs that draw leaders from the text to the appropriate polygons. This coverage is for cartographic purposes and does not include data critical to the database information. The P1 item defines rotation of the text, the P2 item the size of text, and the TEXT item the actual text.
Gsmrelate INFO file: Contains the information that relates the gsmcode.lut and gsmunit.lut to the pat and aat INFO files of the coverages
Gsmunit.lut INFO file: Contains the first two columns of the table above that lists the number (P1 item) assigned to each category of polygon and the corresponding text symbol used in the map explanation and on the face of the map. The database can be made more useful by expanding this file to include items listing characteristics, age, etc. of each geologic unit, and that should be done before a final version is released.
Gsmcode.lut INFO file: Contains a text definition of the meaning of the number stored in the CODE item of every entity in all the coverages.
Gsmcolor.lu INFO file: Assigns a color from shadeset CTR269.shd for each category of polygon according to the P1 item.
Gsmdraw.aml and gsmdraw.mnu files are included to constitute an ARC/INFO macro language program that will extract information from the Mesquite coverages to produce a graphics (.gra) file depicting the Mesquite geologic map. The graphics file can be viewed on screen or plotted with appropriate equipment.
The aml program calls shadeset ctr269.shd, font font003, and lineset alcwrg.lin, so these are also included in the archive file. Other files can be substituted, but special geologic characters may not plot properly with a different font.
Database root name: MESQUITE
P1 VALUE AND LETTER SYMBOLS FOR GEOLOGIC UNITS MAPPED=======
1,Qfp, Flood-plain alluvium
2,Qrm, Recent mainstream alluvium
3,Qim, Intermediate-age mainstream alluvium
4,Qom, Old mainstream alluvium
5,Trm, Tertiary mainstream alluvium
6,Trs, Tertiary sidestream alluvium
10,Qs, Channel alluvium
35,Qiz, Intermediate-age mainstream alluvium, sand and silt facies
46,af, Artificial fill and other land disturbance
47,Tms, Muddy Creek Formation
48,Tmc, Muddy Creek Formation conglomerate facies
53,Qis, Intermediate-age sidestream alluvium
54,Trs, Tertiary sidestream alluvium
56,Qos, Old sidestream alluvium
148,Trs, Tertiary sidestream alluvium (pediment on Muddy Creek Formation)
150,Qos, Old side-stream alluvium (pediment on Muddy Creek Formation)
152,Tok, Old Tertiary calcrete
153,Qe, Windblown sand
167,Ql, Landslide deposits
173,Qrs, Recent sidestream alluvium
177,Qym, Young mainstream alluvium
179,Qys, Young sidestream alluvium
193,Qok, Old Pleistocene calcrete
200,Tik, Intermediate-age Tertiary calcrete
201,Trk, Young Tertiary calcrete
218,Tb, Tertiary basalt lava flow and ash
219,Tf, Post-Muddy Creek Tertiary basin-fill sediments
FEATURES IN THE DATABASE-------------------------
CODE | FEATURE
001 | Geologic contacts
008 | Normal fault -certain
009 | Normal fault - approximately located
010 | Normal fault - concealed
011 | Basaltic ash marker bed line
020 | Fold axis lines
054 | Roads
061 | Map boundary
197 | Field observation point symbol
201 | bedding dip symbol
204 | anticline symbol
205 | syncline symbol
207 | ball & bar symbol
208 | fault dip symbol
255 | monocline - anticline symbol
256 | monocline - syncline symbol
313 | gravel pit symbol
375 | water well symbol
501 | geologic unit tag point
555 | geologic unit tag point and text label
599 | Map margin text