Phyllite and chert

Unit symbol: JTrp
Age range Lower Jurassic to Upper Triassic (235 to 174.1 Ma)
Lithology: Sedimentary
Group name: Volcanic and sedimentary rocks of southwest Alaska
Gray, green, and black phyllite, fine-grained tuff, and tuffaceous chert described as part of the Togiak-Tikchik Complex by Wilson and others (in press [SIMp 2942]; Wilson and Coonrad, 2005). Unit crops out in the southeast corner of the Bethel quadrangle near the heads of Upnuk and Chikuminuk Lakes and trends north-northeast where it continues into the adjacent Taylor Mountains quadrangle. Box and others (1993) constrained age based on underlying Triassic pillow basalt and an Early Jurassic age derived from a single radiolarian collection

Source map information

Source map Hoare, J.M., and Condon, W.H., 1969-1970, Unpublished data.
Symbol MzPzgps
Unit name Phyllite argillite, and chert
Description Gray to black phyllite or slaty argillite, occasionally calcareous or sulfide-bearing along fault zones
Lithology Sedimentary

Correlated geologic units

Label JTrp
Description Phyllite and chert, possible Talkeetna stratigraphic equivalent [Compare with 3850]
Geologic age Late-Triassic to Early-Jurassic
Geologic setting Sedimentary, slope-and-deep-water
Lithology Form Importance
Phyllite < Metaclastic < Metasedimentary < Metamorphic Indeterminate, major
Chert < Chemical < Sedimentary Bed Indeterminate, major
Chert < Chemical < Sedimentary Tuffaceous Indeterminate, major