Pedmar Formation

Unit symbol: Kpf
Age range Lower Cretaceous, Albian (113 to 100.5 Ma)
Lithology: Sedimentary
Group name: Pedmar Formation
Thin sequence (82 m thick) of thick-bedded, fine- to medium-grained, gray to olive-gray sandstone named by Detterman and others (1996) and exposed along coast of Katmai Bay near Mount Pedmar in Mount Katmai quadrangle. Carbonaceous debris is present throughout, and pebbles as large as 4 cm in diameter are found in tabular crossbedded sandstone in middle part of formation. Clasts are typically quartz; volcanic rock clasts are conspicuously absent. Two poorly exposed siltstone and shale intervals are present in upper part of formation; siltstone is much more common locally. Abundant ammonite and Aucellina sp. fossils help to establish well-controlled Albian age for formation. Upper contact of formation is disconformity with overlying by Kaguyak Formation (unit Khk). In type section, lower contact is a fault that juxtaposes Pedmar and Naknek (Jn) Formations. Locally, formation disconformably overlies Herendeen Formation (Khe). This is the only Albian-aged unit known from the Alaska Peninsula

Source map information

Source map Riehle, J.R., Detterman, R.L., Yount, M.E., and Miller, J.W., 1993, Geologic map of the Mount Katmai quadrangle and adjacent parts of the Naknek and Afognak quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-2204, 1 sheet, scale 1:250,000.
Symbol Kp
Unit name Pedmar Formation
Description Thick-bedded gray sandstone and minor siltstone and shale containing ammonites of Albian age exposed along coast of Katmai Bay near Mount Pedmar in Mount Katmai A-3 1:63,360-scale quadrangle. Carbonaceous debris is present throughout, and pebbles as large as 4 cm in diameter are found in tabular crossbedded sandstone in middle part of formation. Clasts are typically quartz; volcanic clasts are conspicuously absent. Two poorly exposed siltstone and shale intervals are present in upper part of formation; siltstone is much more common in a measured section east of Ikagluik Creek, 42 km north of type section in Mount Katmai B-3 1:63,360-scale quadrangle.
Lithology Sedimentary

Correlated geologic units

Label Kp
Description Pedmar Formation, Albian
Geologic age Albian
Geologic setting Sedimentary, shallow-marine-siliciclastic
Lithology Form Importance
Sandstone < Clastic < Sedimentary Carbonaceous Major