Studies by the U.S. Geological Survey in Alaska, 2006

U.S. Geological Survey
Professional Paper 1739-E

A Major Unconformity Between Permian and Triassic Strata at Cape Kekurnoi, Alaska Peninsula: Old and New Observations on Stratigraphy and Hydrocarbon Potential

By Robert B. Blodgett and Bryan Sralla


Outcrop of Upper Triassic carbonates of the Kamishak Formation (light-colored rocks) 1.3 mi (2.1 km) west of Cape Kekurnoi, showing lower contact with underlying Permian volcanic agglomerate and volcaniclastic rocks (dark strata). Contact is an angular unconformity with strikingly obvious erosional cutoff of underlying bedded Permian rocks. (from Figure 2).


A major angular unconformity separates carbonates and shales of the Upper Triassic Kamishak Formation from an underlying unnamed sequence of Permian agglomerate, volcaniclastic rocks (sandstone), and limestone near Puale Bay on the Alaska Peninsula. For the first time, we photographically document the angular unconformity in outcrop, as clearly exposed in a seacliff ~1.3 mi (2.1 km) west of Cape Kekurnoi in the Karluk C–4 and C–5 1:63,360-scale quadrangles. This unconformity is also documented by examination of core chips, ditch cuttings, and (or) open-hole electrical logs in two deep oil-and-gas-exploration wells (Humble Oil & Refining Co.’s Bear Creek No. 1 and Standard Oil Co. of California’s Grammer No. 1) drilled along the Alaska Peninsula southwest of Puale Bay. A third well (Richfield Oil Corp.’s Wide Bay Unit No. 1), south of and structurally on trend with the other two wells, probed deeply into the Paleozoic basement, but Triassic strata are absent, owing to either a major unconformity or a large fault.

Here we briefly review current and newly acquired data on Permian and Triassic rocks of the Puale Bay-Becharof Lake-Wide Bay area on the basis of an examination of surface and subsurface materials. The resulting reinterpretation of the Permian and Triassic stratigraphy has important economic ramifications for oil and gas exploration on the Alaska Peninsula and in the Cook Inlet basin. We also present a history of petroleum exploration targeting Upper Triassic reservoirs in the region.

Download this report as a 13-page PDF file (pp1739e.pdf; 2.2 MB)

For questions about the content of this report, contact Robert Blodgett

Suggested citation and version history

Back to Studies by the U.S. Geological Survey in Alaska, 2006

Download a free copy of the current version of Adobe Reader.

| Help | PDF help | Western reports main page | Western Professional Papers |
| Geologic Division | Alaska Science Center | Western Energy Resources |

This report is available only on the Web

Accessibility FOIA Privacy Policies and Notices

Take Pride in America home page. logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Michael Diggles
Page Last Modified: May 5, 2008