Bedrock geologic map of the northern Alaska Peninsula area, southwestern Alaska

Scientific Investigations Map 2942
Compiled by: Frederic H. WilsonRobert B. BlodgettCharles D. BlomeSolmaz MohadjerCindi C. PrellerEdward P. KlimasauskasBruce M. Gamble, and Warren L. Coonrad



The northern Alaska Peninsula is a region of transition from the classic magmatic arc geology of the Alaska Peninsula to a Proterozoic and early Paleozoic carbonate platform and then to the poorly understood, tectonically complex sedimentary basins of southwestern Alaska. Physiographically, the region ranges from the high glaciated mountains of the Alaska-Aleutian Range to the coastal lowlands of Cook Inlet on the east and Bristol Bay on the southwest. The lower Ahklun Mountains and finger lakes on the west side of the map area show strong effects from glaciation. Structurally, a number of major faults cut the map area. Most important of these are the Bruin Bay Fault that parallels the coast of Cook Inlet, the Lake Clark Fault that cuts diagonally northeast to southwest across the eastern part of the map area, and the presently active Holitna Fault to the northwest that cuts surficial deposits.

Distinctive rock packages assigned to three provinces are overlain by younger sedimentary rocks and intruded by widely dispersed latest Cretaceous and (or) early Tertiary granitic rocks. Much of the east half of the map area lies in the Alaska-Aleutian Range province; the Jurassic to Tertiary Alaska-Aleutian Range batholith and derivative Jurassic sedimentary rocks form the core of this province, which is intruded and overlain by the Aleutian magmatic arc. The Lime Hills province, the carbonate platform, occurs in the north-central part of the map area. The Paleozoic and Mesozoic Ahklun Mountains province in the western part of the map area includes abundant chert, argillite, and graywacke and lesser limestone, basalt, and tectonic mélange. The Kuskokwim Group, an Upper Cretaceous turbidite sequence, is extensively exposed and bounds all three provinces in the west-central part of the map area.

Suggested Citation

Wilson, F.H., Blodgett, R.B., Blome, C.D., Mohadjer, S., Preller, C.C., Klimasauskas, E.P., Gamble, B.M., and Coonrad, W.L., 2017, Bedrock geologic map of the northern Alaska Peninsula area, southwestern Alaska: U.S. Geological Survey Scientific Investigations Map 2942, pamphlet 43 p., scale 1:350,000,

ISSN: 2329-132X (online)

Study Area

Table of Contents

  • Abstract
  • Introduction and Previous Work
  • Geographic, Geologic, and Physiographic Framework
  • Geologic Discussion
  • Digital Data
  • Acknowledgments
  • Description of Map Units
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Bedrock geologic map of the northern Alaska Peninsula area, southwestern Alaska
Series title Scientific Investigations Map
Series number 2942
DOI 10.3133/sim2942
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Alaska Science Center
Description Pamphlet: iv, 43 p.; 2 Sheets: 51.93 x 33.52 inches and 35.62 x 28.33 inches; Database; Metadata; ReadMe
Country United States
State Alaska
Other Geospatial Northern Alaska Peninsula Area
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details