Surficial Geology of Lower Comb Wash, San Juan County, Utah

By Claire I. Longpré1

Open-File Report 01-424





2001












This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

1U.S. Geological Survey, 1201 Pacific Ave. Suite 600, Tacoma, WA 98402  
clongpre@usgs.gov


U.S. DEPARTMENT OF THE INTERIOR				TO ACCOMPANY OF 01-424
U.S. GEOLOGICAL SURVEY


DIGITAL DATABASE DESCRIPTION FOR THE SURFICIAL GEOLOGIC MAP OF LOWER COMB WASH, SAN JUAN COUNTY, UTAH


By Claire I. Longpré


INTRODUCTION

This digital map database, compiled from new mapping by the author, represents the general distribution of surficial deposits in lower Comb Wash.  Together with the accompanying text file (readme.doc, readme.pdf, readme.txt, cw_pamph.doc, cw_pamph.pdf), it provides current information on the late Quaternary stratigraphy of the area covered.  The database delineates map units that are identified by general age and lithology following the spatial resolution (scale) of the database to 1:12,000 or smaller.  The content and character of the database, as well as three methods for obtaining the database, are described below.


A NOTE FOR THOSE WHO DON'T USE DIGITAL GEOLOGIC MAP DATABASES

Two sets of plotfiles containing  images of much of the information in the database are available to those who do not use an ARC/INFO compatible Geographic Information System.  Each set contains an image of a geologic map sheet and the accompanying explanatory pamphlet.  There is a set available in PostScript format, and another in Acrobat PDF format (see sections below).  Those who have computer capability can access the plotfile packages in either of the two ways described below;  however, these packages do require winzip utilities to access the plot files.  Requests for a CD copy of the digital database or plotfiles can be made by sending a blank CD-R or CD-RW with requests and return address to:  Database Coordinator, U.S. Geological Survey, 345 Middlefield Road, M/S 975, Menlo Park, CA 94025.  Plot files can also be acquired online at http://geopubs.wr.usgs.gov/open-file/of01-424.

Those without computer capability can obtain plots of the map files through USGS Plot-On-Demand service for digital geologic maps.  To obtain plots of the map sheet and accompanying pamphlet, contact the USGS Information Services office at the following address:  U.S. Geological Survey Information Services, Box 25286, Federal Center, Denver, CO 80225-0046.  Or by phone (303)202-4200, fax (303)202-4695, or by email: infoservices@usgs.gov.  Be sure to include the map reference OF 01-424.


DATABASE CONTENTS

This digital database package consists of the geologic map database and supporting data including base maps, map explanation, geologic description, and references.  A second package consists of PostScript plot files of a geologic map and geologic description.  The third package contains PDF files of a geologic map and geologic descriptions.

Digital Database Package

The first package is composed of geologic map database files for southern and northern portions of lower Comb Wash.  Files with the designation 'cwn' have the base map Bluff Northwest Quadrangle.  Files with the designation 'cws' have the base map Bluff Southwest Quadrangle.  The coverages and their associated INFO directory have been converted into ARC/INFO export files.  These export files are uncompressed and are easily handled and compatible with some Geographic Information Systems other than ARC/INFO.  The export files included are:

cwn_drain.e00		cwn_drain	Drainages and annotation
cwn_anno.e00		cwn_anno	Annotation for poly coverage
cwn_poly.e00		cwn_poly	Depositional contacts and geologic units
cwn_profile.e00		cwn_profile	Location of stratigraphic description
cwn_xsect.e00		cwn_xsect	Location of geomorphic cross-sections
cws_anno.e00		cws_anno	Annotation for poly coverage
cws_drain.e00		cws_drain 	Drainages and annotation
cws_poly.e00		cws_poly 	Depositional contacts and geologic units
cws_xsect.e00		cws_xsect 	Location of geomorphic cross-sections

The database package also contains the following export files with extraneous data used in the construct of the database:

geolin.lut.e00	geolin.lut	cwn_poly and cws_poly line lookup table
geo.lin.e00		geo.lin		lineset
cw_poly.lut.e00	cw_poly.lut	cwn_poly and cws_poly lookup table
geofont.txt.e00	geofont.txt	textset used for all annotation
color524.shd.e00	color524.shd	524 color shadeset
cw_import.aml	AML to convert all export files in the database to coverages and graphic files

Postscript Plotfile Package

The second digital data package available contains the Post Script images described below:

cw_map.eps:  Encapsulated Post Script file plottable file containing complete map composition with geology, Comb Wash and tributaries, annotation, correlation of map units and legend of symbols and lines.
cw_map.ai:  Adobe Illustrator file containing complete map composition with geology, Comb Wash and tributaries, annotation, correlation of map units and legend of symbols and lines.
cw_pamph.doc:  An MS word document file of the report containing detailed unit descriptions and geological information, plus references sited.
cw_readme.doc:  An MS word document file of this report.

PDF file Description

cw_map.pdf:  Geologic map, correlation of map units, legend of symbols and lines and key to geologic units
cw_pamph.pdf:  Report containing detailed unit descriptions and geological information.
cw_readme.pdf:  A pdf version of this report

The PDF files were created from corresponding .ps files and are compatible with Adobe Acrobat version 3.0 and higher.


ACCESSING DATABASE CONTENTS

Arc/Info Export files

Arc export files can be converted to their proper ARC/INFO format using the ARC command 'import' with the option proper for the format desired.  To ease conversion and preserve naming convention, an AML is enclosed that will convert all the export files in the database to coverages and graphic files and will also create an associated INFO directory.  From the ARC command line type:

Arc: &r cw_import.aml

Arc export files can be read by other Geographic Information Systems.  Refer to your documentation for proper procedure for retrieval of data.

Post Scripts and Portable Document Files

These files are packaged separately.  PDF files come as is and can be downloaded or copied directly to your hard drive with no conversion aside from opening the file from Adobe Acrobat.  The Post Script documents are zipped and compressed to a smaller file size.  They can be decompressed using gzip.


DATABASE SPECIFICS

Procedure Used

Stable base-maps were digitized at the USGS Flagstaff Field Center using an Altek Datatab Proline AC32 digitizer.  A tic file was created and projected into UTM zone 12.  Lines, points, polygons and annotation were edited using ARCEDIT.  ARC/INFO generated the following RMS error report after transforming the coverage from digitizer units to real world coordinates:

cwn_poly

Scale (X,Y) = (88928.188,111518.895)  Skew (degrees) = (0.000)
Rotation (degrees) = (4.486)  Translation = (11198359.674,769183.308)
RMS Error (input,output) = (0.000,1.185)
 
Affine  	X = Ax + By + C
            	Y = Dx + Ey + F
  A = 88655.719	B =  -8723.046	C = 11198359.674
  D = 6956.007	E = 111177.212	F =  769183.308

tic id
input x
input y
x error
y error
 
output x
output y
 
 
1
-109.625
37.500
1.739
-0.073
 
1152360.497
4175776.565
 
 
2
-109.625
37.459
0.361
-0.039
 
1152721.264
4171196.031
 
 
3
-109.625
37.417
-0.699
0.017
 
1153089.914
4166510.967
 
 
4
-109.625
37.375
-1.401
0.094
 
1153089.018
4161879.247
 
 
5
-109.667
37.375
1.743
-0.073
 
1149753.930
4161589.349
 
 
6
-109.667
37.417
0.354
-0.038
 
1149391.917
4166220.957
 
 
7
-109.667
37.459
-0.702
0.018
 
1149025.384
4170905.908
 
 
8
-109.667
37.500
-1.396
0.094
 
1148666.688
4175486.344
 
 



cws_poly

Scale (X,Y) = (306.792,306.432)  Skew (degrees) = (-0.025)
Rotation (degrees) = (-86.984)  Translation = (1143195.696,4161712.220)
RMS Error (input,output) = (0.010,2.936)
 
Affine  	X = Ax + By + C
        	Y = Dx + Ey + F

  A = 16.140   	B = 306.000	C = 1143195.696
  D = -306.367 	E = 16.256	F =  4161712.220
 
tic id
input  x
input y
x error
y error
 
output x
output y
 
 
1
1.234
33.457
-0.550
-1.217
 
1153454.018
4161879.247
 
 
2
16.360
33.856
1.835
4.009
 
1153817.864
4157246.395
 
 
3
31.513
34.240
0.760
-3.706
 
1154181.017
4152617.968
 
 
4
46.651
34.620
-2.047
0.914
 
1154544.434
414791.737
 
 
5
46.950
22.507
-0.123
1.755
 
1150840.753
4147692.387
 
 
6
31.815
22.130
1.565
-3.621
 
1150479.420
4152328.503
 
 
7
16.667
21.744
0.056
2.643
 
1150118.351
4756956.817
 
 
8
1.536
21.355
-1.467
-0.777
 
1149756.592
4161589.577
 
 


Map Projection

Parameter	Description
Projection	UTM
Units		meters on the ground
Zone		12
Datum		NAD27

The content of the geologic database can be described in terms of the lines and the areas that compose the map.  Descriptions of the database fields use the terms explained below

Database Fields

Parameter	Description
Item name	name of database field
Width		maximum number of characters or digits stored
Output		output width
Type	B=binary integer; F=binary floating point number; I=ASCII integer; 
C=ASCII character string

The arcs are recorded as strings of vectors and described in the arc attribute table (AAT).  They define the boundaries of the map units, map boundaries and other linear features in cwn_poly and cws_poly.  These distinctions and the geologic identities of the boundaries are stored in the LTYPE field according to their line type.

Arc Attribute Table Definitions

COLUMN
ITEM NAME
WIDTH
OUTPUT
TYPE
N. DEC
1
FNODE #
4
5
B
--
5
TNODE #
4
5
B
--
9
LPOLY #
4
5
B
--
13
RPOLY #
4
5
B
--
17
LENGTH
8
18
F
5
25
CWN_POLY#
4
5
B
--
29
CWN_POLY-ID
4
5
B
--
33
LTYPE
35
35
C
--

Description of AAT Items

  ITEM		   DESCRIPTION
FNODE #		Starting  node of an arc
TNODE #		Ending node of the arc
LPOLY #		Polygon to the left of the arc
RPOLY #		Polygon to the right of the arc
LENGTH		Length of the arc in meters
CWN_POLY #	Unique internal number
CWN_POLY-ID	Unique identification number
LTYPE		Line type

Domain of Line Types recorded in LTYPE field

cwn_poly and cws_poly
contact_certain	unit contacts mapped with certainty
contact_approx	unit contacts mapped approximately
terrace_scarp	terrace scarp; hatches point down slope
prehistoric_road	location and path of prehistoric road
cwn_drain and cws_drain
ephemeral_stream	ephemeral stream channel
perennial_stream		perennial stream channel
cwn_anno and cws_anno
leader		annotation leader
cwn_xsect and cws_xsect
cross_section	location and approximate path of surveyed geomorphic cross-section

POLYGONS

Map units (polygons) are best described in the cwn_poly and cws_poly polygon attribute tables (PAT).  This identifies the units recorded in the PTYPE  field by map label.  Individual map units are described more fully in the accompanying text.


Definition of polygon attribute table:

COLUMN
ITEM NAME
WIDTH
OUTPUT
TYPE
N. DEC
1
AREA
8
18
F
5
9
PERIMETER
8
18
F
5
17
CWN_POLY#
4
5
B
--
21
CWN_POLY-ID
4
5
B
--
25
PTYPE
6
6
C
--


Description of item name

  ITEM NAME		DESCRIPTION
AREA			Area of polygon in square metes
PERIMETER		Perimeter of polygon in meters
CWN_POLY#		Unique internal number
CWN_POLY-ID		Unique identification number
PTYPE			Unit name

Domain of PTYPE (map units)

af, ta, mct, bct, t3, t2, t1, col, Trc , Trm , Pcm, mfp, st

P represents permian strata, Tr represents triassic strata, t#  represent Quaternary terraces.  Polygons were assigned colors from the shadeset COLOR524.SHD and are related to the CWPOLY.LUT lookup table.


POINTS

Geologic point feature information (stratigraphic profile locations) is recorded as coordinate data with related information.  this information is described in the cwn_profile point attribute table (PAT).

Definition of point attribute table

COLUMN
ITEM NAME
WIDTH
OUTPUT
TYPE
N. DEC
1
AREA
8
18
F
5
9
PERIMETER
8
18
F
5
17
CWN_PROFILE#
4
5
B
--
21
CWN_PROFILE-ID
4
5
B
--
25
ID-NO
6
6
C
--

Description of item names

  ITEM		    DESCRIPTION
AREA		  Degenerate area of a point
PERIMETER	  Degenerate perimeter of a point
CWN_POINT#	  Unique internal number
CWN_POINT-ID	  Unique identification number
ID-NO




ANNOTATION

cwn_anno and cws_anno contain the annotation for the features contained in cwn_poly and cws_poly.


SPATIAL RESOLUTION

Use of this digital geologic map database should not violate the spatial resolution of the data.  Although the digital form of the data removes the constraint imposed by the scale of the paper map, the detail and accuracy inherent in map scales are also present in the digital data.  This database was created and edited at the scale of 1:12,000, which means that higher resolution data are generally not present.  Plotting at scales larger than 1:12,000 will not yield greater real detail but may reveal fine-scale irregularities below the intended resolution.

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