Halleck Formation and similar sedimentary rock units

Unit symbol: Ph
Age range Permian (298.9 to 259.9 Ma)
Lithology: Sedimentary
Group name: Limestone and calcareous clastic rocks
Consists of calcareous siltstone and sandstone, silty limestone, and polymictic pebble and cobble conglomerate (Muffler, 1967; Brew and others, 1984) in the Petersburg and Port Alexander quadrangles. Conglomerate contains clasts of chert, volcanic rock, and limestone derived from the underlying Cannery Formation (Brew and others, 1984). In the Skagway quadrangle, unit consists of phyllite, slate, and metagraywacke of the informal Sitth-gha-ee Peak formation of Brew (Brew and others, 1978, written commun., 1999). Fossils in the Halleck Formation are of Cisuralian (early Permian) age and include early Permian Parafusulina and fenestrate bryozoans, brachiopods, rugose corals, and conical Conichnus? trace fossils (Muffler, 1967). Brew and Ford (1985) noted that these fossils are similar to those found in the Pybus Formation (unit Plps), also early Permian in age. Overlies Saginaw Bay Formation and is conformably overlain by Pybus Formation

Source map information

Source map Brew, D.A., Ovenshine, A.T., Karl, S.M., and Hunt, S.J., 1984, Preliminary reconnaissance geologic map of the Petersburg and parts of the Port Alexander and Sumdum 1:250,000 quadrangles, southeastern Alaska: U.S. Geological Survey Open File Report 84-405, 43 p., scale 1:250,000.
Symbol Phl
Unit name Halleck Formation siltstone, sandstone, limestone, and conglomerate
Description Halleck Formation siltstone, sandstone, limestone, and conglomerate. At Saginaw Bay, dominantly dark-gray very calcareous siltstone that grades into silty limestone, minor intercalated thin beds of fossil fragmental limestone, and very fossiliferous medium-bedded crossbedded medium-gray weathering calcareous sandstone, some small bioherms. In Keku Islets, dominantly thick-bedded polymictic pebble and cobble conglomerate with rounded clasts of chert, felsic volcanic rock, and minor limestone derived mostly from Cannery Formation; minor dark-gray calcareous siltstone and thin- to medium-bedded medium gray fine- to coarse-grained crossbedded sandstone; complexly folded locally
Lithology Sedimentary

Correlated geologic units

Label Phl
Description Halleck Formation calcareous siltstone to conglomerate
Geologic age Artinskian to Kungurian
Geologic setting Undivided
Lithology Form Importance
Siltstone < Clastic < Sedimentary Calcareous Major
Conglomerate < Clastic < Sedimentary Bed Indeterminate, major
Limestone < Carbonate < Sedimentary Calcareous Minor