Sitkalidak Formation

Unit symbol: Tsi
Age range Tertiary, Oligocene to Eocene (59.2 to 33.9 Ma)
Lithology: Sedimentary
Group name: Sitkinak and Sitkalidak Formations
Uniform sandstone and siltstone in graded beds and a few conglomerate beds for a total thickness of about 3,000 m. A fossil crab, Callianassa aff. C. porterensis, indicates an Oligocene age (Moore, 1969); Moore (1969) assigned an Eocene and Oligocene age based on this fossil and evidence from superposition; Clendenen and others (1992) report Eocene foraminifers but only report an Eocene age for the unit. Because of the reported presence of an Oligocene crab fossil in this map unit, the unit age is herein revised to conform to Moore's (1969) original age assignment

Source map information

Source map Clendenen, W.S., Sliter, W.V., and Byrne, Tim, 1992, Tectonic implications of the Albatross sedimentary sequence, Sitkinak Island, Alaska, in Bradley, D.C., and Ford, A.B., eds., Geologic studies in Alaska by the U.S. Geological Survey, 1990: U.S. Geological Survey Bulletin 1999, p. 52-70.
Unit name Sitkalidak Formation, offscraped deposits
Description More deformed interbedded sandstone and siltstone, mudstone and conglomerate, representative of deep-sea fan deposition.
Lithology Sedimentary

Correlated geologic units

Label Tsi
Description Sitkalidak Formation,
Geologic age Eocene
Geologic setting Sedimentary, slope-and-deep-water
Lithology Form Importance
Sandstone < Clastic < Sedimentary Bed Major
Siltstone < Clastic < Sedimentary Bed Major
Conglomerate < Clastic < Sedimentary Bed Incidental