Ghost Rocks Formation

Unit symbol: TKm
Age range early Tertiary and latest Cretaceous (72.1 to 56 Ma)
Lithology: Tectonite
Group name: Ghost Rocks Formation and similar rocks
“Complexly deformed assemblage of sandstone and mudstone with interbedded volcanic rocks and minor pelagic limestone” (Plafker and others, 1994) metamorphosed to prehnite-pumpellyite facies on Kodiak Island; also called the wildflysch of Moore (1969). Turbiditic sandstone- and argillite-rich clastic units contain local channelized conglomerate that has chert, sandstone, limestone, and greenstone clasts (Plafker and others, 1994). “The argillite-rich units include interbedded pillow basalt, tuff, chert-rich pebble conglomerate, and minor limestone * * *” (Plafker and others, 1994). Sandstone is dominantly composed of volcanic lithic fragments and lesser quartz and feldspar in roughly equal proportion (Plafker and others, 1994). Volcanic rocks in the unit consist of both tholeiitic basalt whose composition is most consistent with an oceanic source and calc-alkaline basaltic-andesite and andesite thought to have a hybrid origin by assimilation of sediments in a basaltic magma (Plafker and others, 1994). The unit is sheared, faulted, and folded; Nilsen and Moore (1979) estimated a thickness of about 5,000 m. All contacts with other units, other than intrusive contacts, are faults. Poorly preserved planktonic foraminifers reported by Plafker and others (1994) suggest a latest Cretaceous and Paleocene age for limestone within this unit

Source map information

Source map Moore, G.W., 1969, New formations on Kodiak and adjacent islands, Alaska, in Cohee, G.V., Bates, R.G., and Wright, W.B., Changes in stratigraphic nomenclature by the U.S. Geological Survey 1967: U.S. Geological Survey Bulletin 1274-A, p. A27-A35.
Symbol Tgh
Unit name Ghost Rocks Formation
Description Consists of zeolite-bearing tuffaceous sandstone, basalt, claystone, sandstone, tuff, and graded beds (wildflysch)
Lithology Tectonite

Correlated geologic units

Label TKgh
Description Ghost Rocks
Geologic age Maastrichtian to Paleocene
Geologic setting Melange
Lithology Form Importance
Sandstone < Clastic < Sedimentary Tuffaceous Indeterminate, major
Volcanic < Igneous Pyroclastic, tuff Indeterminate, major
Basalt < Mafic-volcanic < Volcanic < Igneous Flow Indeterminate, major
Claystone < Mudstone < Clastic < Sedimentary Bed Indeterminate, major