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





PRELIMINARY GEOLOGIC MAP OF THE OAT MOUNTAIN 7.5' QUADRANGLE, SOUTHERN CALIFORNIA:  
A DIGITAL DATABASE


Compiled by R. F. Yerkes1  and R. H. Campbell2


Open - File Report 95-89








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, product, or firm names is for 
descriptive purposes only and does not imply endorsement by the U. S. Government. 
 
This database, identified as "Preliminary Geologic Map of the Oat Mountain 7.5' Quadrangle, southern 
California:  A Digital Database," has been approved for release and publication by the Director of the 
USGS.  Although this database has been reviewed and is substantially complete, the USGS reserves the 
right to revise the data pursuant to further analysis and review.  This database is released on condition that 
neither the USGS nor the U. S. Government may be held liable for any damages resulting from its use. 




1997








1 Menlo Park, CA 94025
2Reston, VA 20192



















INTRODUCTION

This Open-File report is a digital geologic map database.  This pamphlet serves to introduce 
and describe the digital data.  There is no paper map included in the Open-File report.  

This digital map database is compiled from previously published sources combined with 
some new mapping and modifications in nomenclature. The geologic map database 
delineates map units that are identified by general age and lithology following the 
stratigraphic nomenclature of the U. S. Geological Survey.  For detailed descriptions of the 
units, their stratigraphic relations and sources of geologic mapping consult Yerkes and 
Campbell (1993).  More specific information about the units may be available in the 
original sources.  

The content and character of the database and methods of obtaining it are described herein.  
The geologic map  database itself, consisting of three ARC coverages and  one base layer, 
can be obtained over the Internet or by magnetic tape copy as described below.  The 
processes of extracting the geologic map database from the tar file, and importing the ARC 
export coverages (procedure described herein), will result in the creation of an ARC 
workspace (directory) called 'oatmtn.' 

The database was compiled using ARC/INFO version 7.0.3, a commercial Geographic 
Information System (Environmental Systems Research Institute, Redlands, California), 
with  version 3.0 of the menu interface ALACARTE (Fitzgibbon and Wentworth, 1991, 
Fitzgibbon, 1991, Wentworth and Fitzgibbon, 1991).  It is stored in uncompressed ARC 
export format (ARC/INFO version 7.x) in a compressed UNIX tar (tape archive) file.  The 
tar file was compressed with gzip, and may be uncompressed with  gzip, which is available 
free of charge via the Internet from the gzip Home Page (http://w3.teaser.fr/~jlgailly/gzip). 
A tar  utility is required to extract the database from  the  tar file.  This utility is included in 
most  UNIX  systems,  and  can be  obtained free of  charge  via  the  Internet  from   
Internet Literacy's Common Internet File Formats Webpage 
(http://www.matisse.net/files/formats.html).  ARC/INFO export files (files with the .e00 
extension) can be converted into ARC/INFO coverages in ARC/INFO (see below) and can 
be read by some other Geographic Information Systems, such as MapInfo via ArcLink and 
ESRI's ArcView (version 1.0 for Windows 3.1 to 3.11 is available for free from ESRI's 
web site:  http://www.esri.com).

This document replaces the original digital database description published in 1995.  
Changes in this release include the following:

1.  Different base layer - The original digital database included separates clipped out of the 
Los Angeles 1:100,000 sheet.  This release includes a vectorized scan of a scale-stable 
negative of the Oat Mountain 7.5 minute quadrangle.

2.  Map projection - The files in the original release were in polyconic projection.  The 
projection used in this release is state plane, which allows for the tiling of adjacent 
quadrangles.

3.  File compression -  The files in the original release were compressed with UNIX 
compression.  The files in this release are compressed with gzip.  




OBTAINING THE DIGITAL DATA

The digital database package can be obtained in any of three ways:

1.  Sending a tape with request
	
A 25 MB compressed tar file of the geologic map database and related files can be obtained 
by sending a tape with request and return address to:

		Oat Mountain, CA 7.5' Geologic Database
		c/o Database Coordinator
		U.S. Geological Survey
		345 Middlefield Road, M/S 975
		Menlo Park, CA 94025

The compressed tar file will be returned on the tape.  The acceptable tape types are:

	1/4 inch, 150 MB cartridge tape
	2.3 or 5.0 GB, 8mm Exabyte tape.


2.  Anonymous ftp over the Internet

To obtain the tar file by anonymous ftp do the following:

cd local_directory		go to a directory to receive the tar file
ftp wrgis.wr.usgs.gov		make ftp connection with the USGS 
				computer WRGIS
Name: anonymous			use 'anonymous' as your user name
Password: your email address	use your email address as a password
cd pub/geologic			go  down to the pub/geologic directory
cd ca/of95-89			go down to the open file directory
type binary			change transfer type to binary
get oatmtn.tar.gz		copy the compressed tar file across 
				Internet to the receiving directory
quit				close the ftp connection

3.  From the Western Region Geologic Information Web Page.

To obtain the tar file via the World Wide Web:

The U.S. Geological Survey now supports a set of graphical pages on the World Wide 
Web. Digital geologic publications (including this one) can be accessed via these pages.  
The web page for digital geologic publications from the Western Region (including this 
one) is  http://wrgis.wr.usgs.gov.  Once at the main page, click on 'Geologic Map 
Databases' under the heading 'Data Online'; next click on 'California.'  Scroll down  
to get to the listing for this database.  Set your web browser to save to a local disk and click 
on the link labeled 'oatmtn.tar.gz' to download the compressed tar file that contains the Oat 
Mountain geologic map database.


EXTRACTING THE GEOLOGIC MAP DATABASE FROM THE TAR FILE

If you obtained the database package on tape:

	put the tape in your tape drive
	cd local_directory		-go to a directory to receive the
					tar file
	tar xvfb /dev/rstn 20		-/dev/rstn is the tape device with
 					n an integer, this puts the tar file 
					in local_directory; 20 is the block
					size of the tar file
	gzip -d  oatmtn.tar.gz		-makes a 105 MB uncompressed 
					tar file oatmtn.tar
	cd local_directory2		-go to the directory that will hold 
					the directory oatmtn (if different 
					from local_directory)
	tar xvfb {path to tar 
	file}/oatmtn.tar 20		-extract the oatmtn directory from 
                                        the tar file; 20 is the block size of
					the tar file.


If you obtained the database package by anonymous ftp or from the web page:

	gzip -d oatmtn.tar.gz		-makes a 105 MB uncompressed 
					tar file oatmtn.tar
	cd local_directory2		-go to the directory that will hold 
					the directory oatmtn (if different 
					from local_directory)
	tar xvfb {path to tar 
	file}/oatmtn.tar 20		-extract the oatmtn directory from 
					the tar file.

Each of the  processes described above will create a directory "oatmtn" that contains the 
ARC export  files and  supporting  files as  described below.  The directory structure at this
point will look like this:

	oatmtn/
		om-geol.e00
		om-strc.e00
		om-wells.e00
		om-topo.e00
		oatmtn.ps
		oatmtn.txt
		import.aml


GEOLOGIC MAP DATABASE CONTENTS

The geologic map database consists of three separate layers and one base layer.  Each of 
these layers (coverages) has been converted to uncompressed ARC/INFO export files.  The 
ARC export files and the associated ARC/INFO coverages, as well as the additional digital 
material included in the database package, are described below:


ARC/INFO		Resultant 		Description of Coverage
export file		Coverage
--------------		------------		-----------------------------
om-geol.e00		om-geol	      		Depositional contacts, faults, and unit labels

om-strc.e00		om-strc			Strike and dip information, fold axes

om-wells.e00		om-wells		Well localities, supporting data given in 
						Yerkes and Campbell (1993), and Yerkes
						and Showalter (1990)

om-topo.e00		om-topo			Topographic base map taken from a scan  of
						a composite negative of the Oat Mountain 7.5
						minute quadrangle (contour interval = 25 ft.)



ASCII text files and PostScript plot files:

	oatmtn.txt	This file.

	oatmtn.ps	A file containing a formatted version of oatmtn.txt

	import.aml	ASCII text file in ARC Macro Language to convert these ARC 
			export files to ARC coverages in ARC/INFO.


The following directory is produced in the process of converting the export files into ARC 
coverages:

	info/		INFO directory containing the database files that accompany each 
			ARC/INFO layer (coverage).

Once the ARC export coverages have been imported (see discussion below), the Oat 
Mountain (oatmtn) directory, or ARC workspace, will look like this:

	oatmtn/
		info/
		om-geol/
		om-strc/
		om-topo/
		om-wells/
		oatmtn.ps
		oatmtn.txt
		import.aml


CONVERTING ARC EXPORT FILES

ARC export files are converted to ARC coverages using the ARC command IMPORT with 
the option COVER.  In order to ease conversion and to maintain naming conventions, we 
have included an ASCII text file in ARC Macro Language that will convert all of the export 
files in the database into coverages and create the associated INFO directory.  Change 
directories to the oatmtn/ directory.  From the ARC command line type:

Arc:  &run import.aml

ARC export files can also be read by some other Geographic Information Systems.  Please 
consult your GIS documentation to see if you can use ARC export files and the procedure 
to import them. 


DIGITAL COMPILATION

The geologic map information was digitized from stable originals of the geologic maps at 
1:24,000 scale.  The author manuscripts (pencil on mylar) were scanned using a  
monochrome scanner with a resolution of 800 dots per inch.  The scanned images were 
vectorized and transformed from scanner coordinates to projection coordinates with  digital
tics placed by hand at quadrangle corners.  The scanned lines were edited interactively by 
hand using graphical user interface ALACARTE (Fitzgibbon, 1991, Fitzgibbon and 
Wentworth, 1991, Wentworth and Fitzgibbon, 1991).  Scanning artifacts significant for 
display at a scale of 1:24,000 were corrected.


BASE MAPS

The base map layer (om-topo) was prepared by scanning a scale-stable composite negative 
image of the Oat Mountain 7.5 minute topographic map (1969 edition).  The negative was 
scanned using a monochrome scanner with a resolution of 400 dots per inch.  The raster 
scan was converted to a GRID in ARC/INFO.  The GRID  was then vectorized and 
reprojected into State Plane Projection using the four corner tics as reference points.  The 
arcs in the base layer have not been attributed.  The base map is provided for reference 
only.


SPATIAL RESOLUTION

Uses of this digital geologic map should not violate the spatial resolution of the data.  
Although the digital form of the data removes the constraint imposed by the scale of a paper 
map, the detail and accuracy inherent in map scale are also present in the digital data.  The 
fact that this database was edited at a scale of 1:24,000 means that higher resolution 
information is not present in the dataset.  Plotting at scales larger than 1:24,000 will not 
yield greater real detail, although it may reveal fine-scale irregularities below the intended 
resolution of the database.  Similarly, where this database is used in combination with other 
data of higher resolution, the resolution of the combined output will be limited by the lower 
resolution of these data.  


FAULTS AND LANDSLIDES

This database is not sufficiently detailed or comprehensive to identify or characterize site-
specific hazards represented by faults or landslides shown;  the faults shown do not take 
the place of fault-rupture hazard zones designated by the California State Geologist (see 
Hart, 1988).


DATABASE SPECIFICS

The map databases consist of ARC coverages which are stored in State Plane (California 
coordinate system) projection (Table 1).  Digital tics define a 2.5 minute grid of latitude and 
longitude in the geologic coverages corresponding with quadrangle corners and internal 
tics.  In the base map layer, the tics define a 7.5 minute grid, corresponding with 
quadrangle corners.


Table 1 - Map Projection
The map is stored in State Plane projection

PROJECTION STATE PLANE	
UNITS METERS			-on the ground
ZONE 3426			-Arc/Info State Plane zone 
                                corresponding to California
                                coordinate system zone 7  
DATUM NAD27
PARAMETERS			-none

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 in Table 2.

Table 2 - Field Definition Terms

ITEM NAME	name of the database field (item)
WIDTH		maximum number of digits or characters stored
OUTPUT		output width
TYPE		B-binary integer, F-binary floating point number, 
 		I-ASCII integer, C-ASCII character string
N. DEC. 	number of decimal places maintained for 
		floating point numbers 


LINES  

The lines (arcs) are recorded as strings of vectors and are described in the arc attribute table 
(Table 3).  They define the boundaries of the map units, the boundaries of open bodies of 
water, and the map boundaries.  These distinctions, including the geologic identities of the 
unit boundaries, are recorded in the LTYPE field according to the line types listed in Tables 
4 and 5.



Table 3 - Content of the Arc Attribute Tables  (OM-GEOL.AAT, OM-STRC.AAT)

ITEM NAME	WIDTH	OUTPUT	TYPE	N. DEC	

FNODE#		4	5	B		starting node of arc (from node)   
TNODE#		4	5	B		ending node of arc (to node)
LPOLY#		4	5	B		polygon to the left of the arc
RPOLY#		4	5	B		polygon to the right of the arc
LENGTH		4	12	F	3	length of arc in meters 
<coverage>#	4	5	B		unique internal control number
<coverage>-ID	4	5	B		unique identification number
LTYPE		35	35	C		line type (see Tables 4 and 5) 
SEL		1	1	I		user defined field used     
						to save a selected set
SYMB		3	3	I		user defined field used    
						to save symbol assignments 
						(such as color) 		


Table 4 - Line Types Recorded in the LTYPE Field  (OM-GEOL)

				contact, approx. located
				contact, certain
				fault, approx. located
				fault, concealed
				map boundary, certain
				thrust fault, approx. located
	

Table 5 - Line Types Recorded in the LTYPE Field  (OM-STRC)

				f.a., anticline, approx. located
				f.a., anticline, concealed
				f.a., anticline, overturned
				f.a., syncline, approx. located
				f.a., syncline, concealed
				f.a., syncline, overturned

				
AREAS  

Map units (polygons) are described in the polygon attribute table (Table 6)  The identities of 
the map units from compilation sources are recorded in the PTYPE field by map label 
(Table 7).  For a full description of the map units see Yerkes and Campbell (1993).  


Table 6 - Content of the Polygon Attribute Tables  (OM-GEOL.PAT)

ITEM NAME	WIDTH	OUTPUT	TYPE	N. DEC	
	
AREA		4	12	F	3	area of polygon in square meters
PERIMETER	4	12	F	3	length of perimeter in meters
<coverage>#	4	5	B		unique internal control	number
<coverage>-ID	4	5	B		unique identification number 
PTYPE		35	35	C		unit label (see Table 7)
SEL		1	1	I		user defined field used to save 
						a selected set
SYMB		3	3	I		user defined field used to save 
						symbol assignments (such as 
						color)


Table 7 - Map Units  (OM-GEOL)

Kc				Qsw				Tp			Tt4
Qal				Qt				Tp?			Ttb	
Qao				Qto				Tpc			Tw
Qay				Tl				Tps			Twc	
Qay1				Tlc				Tsc1			Tws
Qay2				Tm				Tsc2			acf
Qc				Tm1				Tsc3			af
Qls				Tm2				Tss			res
Qp				Tm3				Tt			rf
Qs				Tm4				Tt1
Qsm				Tmd				Tt2
Qsu				Tms				Tt3

	

POINTS 

Point information (strikes and dips, well localities) is recorded as coordinate and related 
information and is described in the Point Attribute Table (Tables 8, 10).  The identities of 
point types recorded in the PTTYPE field of the OM-STRC.PAT table are shown in Table 
9.  



Table 8 - Content of the Point Attribute Tables  (OM-STRC.PAT)

ITEM NAME	WIDTH	OUTPUT	TYPE	N. DEC	
	
AREA		4	12	F	3	not used 
PERIMETER	4	12	F	3	not used
<coverage>#	4	5	B		unique internal control	number
<coverage>-ID	4	5	B		unique identification number
PTTYPE		35	35	C		point type (see Table 9)
DIP		3	3	I		dip angle in degrees
STRIKE		3	3	I		strike angle in degrees
SEL		1	1	I		user defined field used to 
						save a selected set
SYMB		3	3	I		user defined field used to
						save symbol assignments
						(such as color)
								

Table 9 - Point Types  (OM-STRC)

					bedding
					flat bedding
					ot bedding
					vert bedding


Table 10 - Content of the Point Attribute Tables  (OM-WELLS.PAT)

ITEM NAME	WIDTH	OUTPUT 	TYPE	N. DEC	
	
AREA		4	12	F	3	not used 
PERIMETER	4	12	F	3	not used
<coverage>#	4	5	B		unique internal control number
<coverage>-ID	4	5	B		unique identification number
PTTYPE		35	35	C		point type
SAMNO		35	35	C		sample number
SEL		1	1	I		user defined field used 
						to save a selected set
SYMB		3	3	I		user defined field used to 
						save symbol assignments
						(such as color)

					

ACKNOWLEDGMENTS

R. H. Campbell, Reston, VA assisted in field interpretations and compilation;  P. K. 
Showalter and C. M. Wentworth supplied critical custom programming;  and S. E. Graham
updated supporting files for completeness and consistency and prepared this report.


REFERENCES

Fitzgibbon, T.T., 1991, ALACARTE installation and system manual (version 1.0): U.S. 
	Geological Survey, Open-File Report 91-587B.

Fitzgibbon, T.T., and Wentworth, C.M., 1991, ALACARTE user interface - AML code 
	and demonstration maps (version 1.0):  U.S. Geological Survey, Open-File Report 
	91-587A.

Hart, E.W., 1988, Fault-rupture hazard zones in California; Alquist-Priolo Special Studies 
	Zones Act of 1972 with index to special studies zones maps:  California Division of 
	Mines and Geology Special Publication 42.

Wentworth, C. M., and Fitzgibbon, T. T., 1991, ALACARTE user manual (version 1.0):  
	U. S. Geological Survey Open-File Report 91-587C.

Yerkes, R. F., and Campbell, R. H., 1993, Preliminary geologic map of the Oat Mountain 
	7.5 minute quadrangle, southern California:  U. S. Geological Survey Open-File 
	Report 93-525.

Yerkes, R. F., and Showalter, 1990, Exploratory wells drilled in the Los Angeles, 
	California 1:100,000 quadrangle, southern California: U. S. Geological Survey 
	Open-File Report 90-627.