Calcareous mudstone

Unit symbol: Kcm
Age range Lower Cretaceous (132.9 to 125 Ma)
Lithology: Sedimentary
Group name: Coquina and calcarenite
Dark-gray, fossiliferous, calcareous mudstone that has lenses of aragonitic fossil hash and limestone concretions as large as 20 cm, and contains subordinate beds of calcareous wacke (Johnson and Karl, 1985). Unit restricted to a small area of outcrop east of Chichagof Island and is significant in southeast Alaska on the basis of its unique lithology and fossil assemblages. Fossils included Hauterivian to Barremian belemnites, and Inoceramus prisms (W.P. Elder, written commun., 1998, to S.M. Karl)

Source map information

Source map Karl, S.M., 2013, Unpublished data.
Symbol Ksm
Unit name Calcareous mudstone, siltstone, and sandstone
Description Emmons Is, fore arc basin, early K, dark gray, calcareous fossiliferous mudstone with lenses of aragonitic fossil hash, and limestone concretions to 20 cm, and subordinate beds of calcareous wacke. Associated with pillow basalt and breccia
Lithology Sedimentary

Correlated geologic units

Label Kcm
Description Fossiliferous calcareous mudstone in southeast Alaska
Geologic age Hauterivian to Barremian
Geologic setting Sedimentary, deltaic-and-nearshore
Lithology Form Importance
Mudstone < Clastic < Sedimentary Calcareous Major
Graywacke < Sandstone < Clastic < Sedimentary Calcareous Indeterminate, major