1_README.TXT
U.S. DEPARTMENT OF THE INTERIOR
U.S. GEOLOGICAL SURVEY

Geologic Map of Central (Interior) Alaska

compiled by

Frederic H. Wilson(1), James H. Dover(1), Dwight C. 
Bradley(1), Florence R. Weber(2), Thomas K. Bundtzen(3), and 
Peter J. Haeussler(1)

1998

OPEN-FILE REPORT 98-133-A
Version 1.1

U.S. DEPARTMENT OF THE INTERIOR
BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY
Charles G. Groat, Director

Prepared in cooperation with the Alaska Department of Natural 
Resources, Division of Oil and Gas and Division of Geological 
and Geophysical Surveys

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.

(1) U.S. Geological Survey, 4200 University Dr., Anchorage 
     AK 99508-4667; 
(2) U.S. Geological Survey, P.O. Box 80586, Fairbanks, 
     AK 99708-0586; 
(3) Pacific Rim Geological Consulting, P.O. Box 81906, 
     Fairbanks, AK 99708-1906

DISCLAIMERS

This Compact Disc-Read Only Memory (CD-ROM) publication was 
prepared by an agency of the United States Government. 
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nor any of their employees, makes any warranty, expressed or 
implied, or assumes any legal liability or responsibility 
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commercial product, process, or service by trade name, 
trademark, manufacturer, or otherwise does not necessarily 
constitute or imply its endorsement, recommendation, or 
favoring by the United States Government or any agency 
thereof.

Although all data and software published on this CD-ROM have 
been used by the USGS, no warranty, expressed or implied, is 
made by the USGS as to the accuracy of the data and related 
materials and (or) the functioning of the software. The act 
of distribution shall not constitute any such warranty, and 
no responsibility is assumed by the USGS in the use of this 
data, software, or related materials.

SYSTEM REQUIREMENTS

This CD-ROM (OF98_133) was produced in accordance with the 
ISO 9660 Level 2 standard and Apple ComputerŐs(1) 
hierarchical file system (HFS) standard. 
 
The data and text on this CD-ROM require either a Unix work 
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The Macintosh should have a 68030 or higher processor 
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256 colors.  The PC should have an 80486 or higher processor 
(Pentium(3) recommended), Microsoft Windows(4) 95 or higher 
(Windows 98 or NT recommended), 8 megabytes RAM (32 MB 
recommended), and a VGA color monitor that can display 256 
colors.  Both platforms require MS Word(4) 97/98 or higher to 
read the .DOC files, MS Excel(4) 4.0 or higher to read the 
.XLS files, FileMaker(5) Pro 3.0 or higher to read the .FP3 
file, and Adobe Acrobat(6) Reader 3.0 or higher (3.01 
provided on this disc) to read the .PDF files.  You will need 
GIS software such as ArcView(7) or Arc/INFO(7) to read the 
Arc graphics and related files.

To Get Started:

On a Macintosh, double-click on the CD-ROM icon and double-
click on the file 1_README.TXT.  On a PC system with Windows, 
open Notepad or a word-processing application, change to the 
CD-ROM device, and open the file 1_README.TXT.

Registered trademarks:  (1)Apple Computer and Macintosh, 
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PORTABLE DOCUMENT FORMAT (PDF) FILES 

This disc contains Portable Document Format (PDF) files for 
viewing and searching documents.  The ACROBAT directory 
contains installers for Adobe Acrobat Reader 3.01 for both 
Windows (PC directory) and Macintosh (MAC directory, Reader 
3.01 Installer).  For Windows, a 32-bit version (SETUP.EXE 
installer) is provided for Windows NT and Windows 95/98.  You 
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searching the .PDF files for words or sets of words using the 
search tool in Acrobat Reader

Introduction

This map and associated digital databases are the result of a 
compilation and reinterpretation of published and unpublished 
1:250,000- and limited 1:125,000- and 1:63,360-scale mapping.  
The map area covers approximately 416,000 sq km (134,000 sq 
mi) and encompasses 25 1:250,000-scale quadrangles in central 
Alaska.  The compilation was done as part of the U.S. 
Geological Survey National Surveys and Analysis project, 
whose goal is nationwide assemble geologic, geochemical, 
geophysical, and other data.  This map is an early product of 
an effort that will eventually encompass all of Alaska, and 
is the result of an agreement with the Alaska Department of 
Natural Resources, Division of Oil And Gas, to provide data 
on interior basins in Alaska.  A paper version of the three 
map sheets has been published as USGS Open-File Report 
98-133.  Two geophysical maps that cover the identical area 
have been published earlier:  "Bouguer gravity map of 
Interior Alaska" (Meyer and others, 1996); and "Merged 
aeromagnetic map of Interior Alaska" (Meyer and Saltus, 
1995).  These two publications are supplied in the "geophys" 
directory of this 
disc.

Compilation of this map began in September 1996, using 
published 1:250,000-scale mapping.  As the project 
progressed, published maps at other scales and unpublished 
mapping were incorporated as we built an integrated map.  
Description and correlation of geologic units to produce map 
units was an iterative process that continued through 
technical review to publication.  Digital files of the final 
compilation of each of the 25 1:250,000-scale quadrangles are 
available on a companion CD-ROM.  Cited in the text and on 
the map are the map sources we used; additional map sources 
are listed in Galloway and Laney (1994).

It takes little imagination to realize that many compromises 
have been made in strongly held beliefs to allow construction 
of this compilation.  Yet even our willingness to make 
interpretations and compromises does not allow us to resolve 
mapping conflicts in some areas.  Therefore, there are a 
number of areas on the map where it was necessary to separate 
map units by "quadrangle boundary faults."  More time and 
fieldwork may allow resolution of these conflicts.  We 
believe that this map and its problems present a very good 
argument to justify and support further work in this area and 
elsewhere in Alaska.  Nonetheless, we hope that geologists 
who have mapped in central Alaska will recognize that in 
incorporating their work, our regional correlations have 
required generalizing and lumping of units.  Lead efforts on 
the map compilation were as follows:  Cenozoic and Mesozoic 
sedimentary rocks and igneous rocks, Frederic Wilson; 
Paleozoic sedimentary rocks, Dwight Bradley; metamorphic 
rocks, James Dover; with supporting efforts for all rock 
types in the northeast and central part of the map area by 
Florence Weber; the southwest part of the map area by Tom 
Bundtzen; and the Tyonek area by Peter Haeussler.

Compiling this map was complicated because the original 
source maps were made by different generations of geologists, 
mapping with very different ideas.  A few of the older maps 
were completed before the concepts of plate tectonics or 
accreted (suspect) terranes.  On the other hand, some of the 
more recent maps were so governed by terrane analysis that 
conventional stratigraphic nomenclature was not used and is 
obscured.  For the present compilation, we adopted a 
traditional stratigraphic approach and have avoided use of 
the controversial and inconsistently defined term "terrane."  
Our decision to adopt a traditional approach is reflected in 
a map that emphasizes age and lithology of map units, rather 
than differences among fault-bounded packages of rocks.  For 
a map of the present scope and scale, the traditional 
approach seems to have more to offer to a wider variety of 
users.  It is far easier to construct a terrane map from a 
traditional geologic map than vice-versa.  One conception of 
the map area from a terrane point of view is that of 
Silberling and others (1994), shown as figure 2 on sheet 3 of 
this compilation.  Another can be found in Nokleberg and 
others (1994).  It will be apparent from examination of 
figure 2 that our lumpings of units results in a map having 
divisions only loosely similar to Silberling and others 
(1994)

Some of our groupings of map units use terms previously 
applied by other geologists to terranes.  We instead use such 
terms as "sequence" "assemblage," and "complex" for groups of 
rock units characterized by a common history or environment.  
Sequences, as used here, are groups of sedimentary rock units 
that display a coherent and consistent stratigraphy and 
association.  Assemblages consist of a mixture of 
sedimentary, igneous, and(or) metamorphic rock units within a 
still recognizable stratigraphic framework that may be 
tectonically internally disrupted.  Complexes are generally 
restricted to igneous or metamorphic rock assemblages and may 
have no apparent stratigraphic framework.  An exception, 
however is the McHugh Complex, a tectonic melange in southern 
Alaska whose name is in common use.

In general, where terminology for lithologic packages of rock 
units has come into common usage and where we could justify 
or support its continued usage, we have used that 
terminology.  An example of such a lithologic association is 
the Nixon fork sequence.  The ease with which this is done is 
in part dependent on our knowledge or perceived understanding 
of the rock units.  This packaging occurs at either extreme 
of our spectrum of knowledge.  Thus, packaging very old 
metamorphic rocks is relatively easy because we don't know 
any better.  In other cases, such as the Nixon Fork sequence, 
we have reasonably good constraints on the nature of the rock 
units and can confidently package them.

In the following descriptions, units are generally listed in 
chronological order from youngest to oldest.  In the unit 
descriptions, the age of the units, rather than their 
apparent stratigraphic position is given after the unit label 
and name.  In the text of the descriptions, lower and upper 
is used to denote stratigraphic position, whereas late and 
early indicate age.  Within each major age category, 
sequences, assemblages, and complexes are listed first, 
followed by sedimentary, igneous, and metamorphic rock units, 
listed in order of increasing age.

In general, metamorphic rock units are listed in increasing 
order of their inferred or interpreted protolith age, which 
in many cases is subject to significant uncertainty.  In the 
limited number of cases for which we cannot interpret a 
protolith age the metamorphic rocks are listed by increasing 
age of metamorphism, either known or inferred.
Acknowledgements

There is no way that a compilation on this scale could be 
done without the assistance of many geologists, far more 
knowledgeable about the geology of various regions of Alaska 
than we are.  We have benefited greatly from the opportunity 
to use unpublished mapping by and to consult with Grant 
Abbott, Robert M. Chapman, Julie A. Dumoulin, Cynthia Dusel-
Bacon, Bruce M. Gamble, Anita Harris, Marti L. Miller, 
Madelyn Millholland, Warren J. Nokleberg, Donald H. Richter, 
William W. Patton, Jr., Gary R. Winkler, and Wesley K. 
Wallace.  In addition, support and encouragement from many of 
our peers, including Donald Grybeck, Thomas D. Light, and 
Alison B. Till, have made what at times seemed an 
overwhelming task, seem more possible and desirable.

The project to produce this map had short deadlines and would 
not have been possible without the able support of Nora Shew 
and her GIS support staff.  Catherine G. Baxter, Kelly M. 
Brunt, Nathan S. Pannkuk, James D. Hall, S.M. Weems, Dolly 
Perea, and David Dempsey each made invaluable contributions 
to the project and helped us to meet our deadlines.

The Alaska Department of Natural Resources, Division of Oil 
and Gas provided strong encouragement and financial support 
to help with the preparation of this map; its assistance was 
invaluable in seeing to it that the map was completed.

In addition, organizational support from the Alaska 
Department of Natural Resources, Division of Geological and 
Geophysical Surveys is greatly appreciated.  Particularly, 
support and unpublished data made available by Ellie E. 
Harris and Rocky R. Reifenstuhl have helped to improve the 
map significantly.

Technical and editorial review of all or part of the 
manuscript by John C. Reed, Jr. and Henry C. Berg were 
greatly appreciated and have helped to improve the text and 
map.


CAKUNITS files

We have provided a series of files of the data file that 
links NSAclass codes in the coverages to specific geologic 
units in each quadrangle.  Provided here is a Filemaker Pro 
database (.FP3), a database exchange formated file (.DBF), 
and a text file using quotes and commas to separate fields 
(.CDV).

Data are in the .dbf and .csv in the following field order:

rock unit      Label from the source map
unit name      From source map
age            From source map
description    Abstracted from source map
fossil?        Abstracted from source map
radiometric    Reported on source map
source code    Keyed to source map  (add 1 to digit listed in 
                  text "list of map sources")
class code     Keyed to source map (applies only to the 
                  individual source map)
quadrangle     1:250,000 scale quadrangle
rock class     Sedimentary, Igneous, etc
NSAclass       Correlation code used for Central Alaska map
label          Label used on Central Alaska map


Files contained in OF98_133

Root directory
1_README.TXT (this file) Introduction to the CD 
     (Includes description of contents)
2_EPS files of sheets 1, 2, and 3
     dogsht1.eps (entire sheet)
     dogsht1a.eps (top half)
     dogsht1b.eps (bottom half)
     dogsht2.eps (entire sheet)
     dogsht2a.eps (top half)
     dogsht2b.eps (bottom half)
     dogsht3.eps (entire sheet)
3_PDF files of sheets 1, 2, and 3 (entire sheets for 1 and 2 
          will not fit in pdf format)
     dogsht1a.pdf (top half)
     dogsht1b.pdf (bottom half)
     dogsht2a.pdf (top half)
     dogsht2b.pdf (bottom half)
     dogsht3.pdf (entire sheet)
ACROBAT (installers for Adobe Acrobat PDF viewing software 
     for Mac, and Windows 32 computers)
ARC Graphics file of sheets 1, 2 , and 3
          dogsht1.gra
          dogsht2.gra
          dogsht3.gra
          terranes.gra
          dogstruct.gra
          dogmask.gra (shaded relief)
          wellmap.gra
          inset.gra (wells inset)
          index.gra
          sources.gra
Arc-Related files
     AMLs
          dogsht1.aml
          dogsht2.aml
          dogsht3s.aml
     Ancillary files
          disclaim.dog
          disclaim.er
          doga1.key
          dogao1.key
          dogb1.key
          dogbo1.key
          dogc1.key
          dogco1.key
          dogd1.key
          dogdo1.key
          doge1.key
          dogeo1.key
          fig2.txt
          geoline.key
          mapcred.dog
          utm4-alb.prj
          utm5-alb.prj
          utm6-alb.prj
     Lookup tables and symbolsets
          DATASTRU.DOC, MS Word97/98 version of map key 
               for digitizing of geologic maps for the 
               National Surveys and Analysis project
           DATASTRU.PDF, Acrobat PDF version of Map key for 
               digitizing of geologic maps for the National 
               Surveys and Analysis project
          fnt020
          fnt025
          fnt036
          fnt040
          geoline.lut.e00
          geology.lin.e00
          geology.mrk.e00
          geology.shd.e00
          nsakey.lut.e00
          nsakeyal.lut.e00
          nsakeyhf.lut.e00
          nsakeyo.lut.e00
CAKUNITS.CSV, A table of geologic units for central Alaska in 
     comma-delimited ASCII format that can be imported into 
     many database-management applications.
CAKUNITS.DBF, A table of geologic units for central Alaska in 
     database exchange format
CAKUNITS.FP3, A table of geologic units for central Alaska in 
     FileMaker Pro 3.0 format
covers
     1_README.TXT
     ancomp.e00        Anchorage
     bdcomp.e00        Big Delta
     cicomp.e00        Circle
     fbcomp.e00        Fairbanks
     gucomp.e00        Gulkana
     hecomp.e00        Healy
     idcomp.e00        Iditarod
     khcomp.e00        Kantishna River
     ktcomp.e00        Kateel River
     lgcomp.e00        Livengood
     lhcomp.e00        Lime Hills
     mdcomp.e00        Medfra
     mgcomp.e00        McGrath
     mhcomp.e00        Mount Hayes
     mmcomp.e00        Mount McKinley
     mzcomp.e00        Melozitna
     nlcomp.e00        Nulato
     opcomp.e00        Ophir
     rbcomp.e00        Ruby
     smcomp.e00        Sleetmute
     tkcomp.e00        Talkeetna Mountains
     tlcomp.e00        Talkeetna
     tncomp.e00        Tanana
     tycomp.e00        Tyonek
     vacomp.e00        Valdez
     dogstruct.e00     dogstruct
     bnddogne.e00      bnddogne
     bnddognw.e00      bnddognw
     bnddogse.e00      bnddogse
     bnddogsw.e00      bnddogsw
geophys (Image files and data files for USGS GP-1014 (Merged 
          Aeromagnetic Map of Interior Alaska) and USGS 
          GP-1016 (Bouguer Gravity Map of Interior Alaska))
     1_README.TXT
     AKgrav-README.TXT
     AKgrv_10km.asc
     AKgrv_int.asc
     AKmag-README.TXT
     AKmag_composite.zasc
     AKmag_merge.zasc
     intak_grv.asc
     intak_grv.exl
     intak_grv.tab
     negrav.pdf
     nemag.pdf
     nwgrav.pdf
     nwmag.pdf
     segrav.pdf
     semag.pdf
     swgrav.pdf
     swmag.pdf
INDEX (files used by the Search tool in Acrobat Reader)
INDEX.PDX (index file used by Acrobat Reader)
metadata
     ancomp.met
     bdcomp.met
     cicomp.met
     fbcomp.met
     gucomp.met
     hecomp.met
     idcomp.met
     khcomp.met
     ktcomp.met
     lgcomp.met
     lhcomp.met
     mdcomp.met
     mgcomp.met
     mhcomp.met
     mmcomp.met
     mzcomp.met
     nlcomp.met
     opcomp.met
     rbcomp.met
     smcomp.met
     tkcomp.met
     tlcomp.met
     tncomp.met
     tycomp.met
     vacomp.met
OF98_133.DOC (MS Word 97/98 file of text)
OF98_133.PDF (Acrobat PDF of text and drillhole data)
OF98_133.XLS (MS Excel file of drillhole data)