Information About the Geology of the Pocatello 30 x 60 Minute Quadrangle
Thematic Mapping Database
Idaho Geological Survey
University of Idaho
Moscow, Idaho 83844-3014
PART 1
Using ARC/INFO
Ready-to-use ArcGIS. Coverages are included on this CD ROM. Export
files are also included, should you have trouble using theses provided files. These
data are in 2 halves: the east and west halves of the Pocatello 30 x 60 minute
quad.
Geologic Thematic Mapping Data
There are several coverages to the Pocatello 30 x 60 data:
Rocks(polygons)----------Geologic units polygons
Rocks(lines)--------------Contact segments
Faults(lines)----------------Fault line segments
Dikes(lines)------------Present for dikes too small to be digitized as
polygons
Fold axes(lines)-------Trace of axial folds
Symbols(points)
Attitudes--------symbols showing azimuth, dip and
location of planar features; strike and dip and flow foliation
symbols
Linears----------symbols showing linear trends of
rocks features; small folds, plunges, etc..
Other symbols
(See metadata--data-dic.dbf-- for more information about individual data
fields)
Metadata
Metadata is information about a data set. There are six metadata databases
included with this data set. In spirit these files meet the Federal Geographic Data
Committee's (FGDC) Content Standards for Digital Geospatial Metadata. The
Idaho Geological Survey uses a subset standard developed by the Idaho
Geographic Information Advisory Committee (IGIAC), Metadata Standard
Version 3.1. All metadata is located in the METADATA directory.
The six databases are:
Unit.dbf-------------Geologic unit descriptions; linked to
polygon(pat). You can join the unit.dbf to the Rocks coverage via
the “Unit” and “Value” items/fields respectively.
Data-dic.dbf---------Data dictionary
Identify.dbf---------Whole database information; projection etc.
Sources.dbf----------Individual sources database info; projection,
media info, etc. You can join the sources.dbf to the Rocks\arcs
coverage via the “source_ID” and “refID2” items/fields
respectively.
Access.dbf-----------Availability information, contact info, liability
FGDC-IGS.dbf-----Data dictionary for IGS Metadata
Projection: Idaho State Plane, east zone, NAD27, feet.
PART 2
Location
Pocatello 30 x 60 minute tile (in two pieces: East and West halves)
Geologic Mapping
This database represents years of work by many individuals. Field geology
involves many tasks including photo interpretation, field checking, field data
collection, drill hole interpretation, and geologic interpretation. Geologic mapping
is a highly subjective science. The geologic data presented here was compiled
from existing, published and unpublished, geology to give continuous coverage
over a large area.
A compilation geologic map is pieced together from separate geologic
maps of varying scales, emphasis, and quality. Most locations in Idaho have
original geologic mapping available but the scales vary greatly. A compilation
map is considered a “work in progress” because it can always be improved with
the addition of better mapping. To determine the quality of data within a digital
compilation it is critical to be able to track the individual geologic maps. To meet
this requirement all entities within our geologic map coverages can be linked to
metadata via a reference identifier. (For complete information about the data set,
see the metadata database files)
The geologic data presented here are intended for use at a maximum scale
of 1:24000-1:125,000 (depending on the mapping source). The data should not be
used for site-specific purposes.
PART 3
SYMBOLS USED IN Pocatello 30 x 60 DATA SET:
Symbol Name:
Attitudes:
Strike----------Strike and dip of bedding
Str-over-------Over turned bedding(over-turned strike)
Str-vert--------Vertical bedding
Strtop----------Bedding where top is known
Fol--------------Attitude of foliation
Fol-vert--------Foliation vertical
Joint------------Attitude of jointing in rock
Linears:
Crenlin--------Crenulation lineation
Smllfold-------Small fold
Plunge---------Plunge and trend fold axis
Other symbols:
Faultdir--------Fault direction of high-angle fault, located on down-drop side
Tooth-----------Thrust fault or reverse fault tooth, located on upper plate
Mylon----------Mylonite
Sedbrec--------Sedimentary breccia
(See data-dic.dbf in the Metadata directory for specific field/item information)
LINETYPES USED IN Pocatell 30 x 60 DATA SET:
Continuous: Most accurately placed geologic contact, fault, or other line feature.
USGS standard is =<+/- 80 feet at 1:24,000.
Approximate: Geologic contact, fault, or other line feature approximately
located. Greater than 80 feet at 1:24,000.
Inferred: Geologic contact, fault, or other line feature not determined from direct
observation.
Dotted: Concealed geologic fault line feature
Submerged: Geologic contact, fault, or other line feature located under water.
Hanging: Contacts added to close geologic polygons; usually between two study
areas
PART 4
Some additional notes:
T_=Triassic, since there is no character on the key board to match the geologic
symbol
P_= Pennsylvanian, ditto