Whitestripe Marble of southeast Alaska

Unit symbol: Trwm
Age range Triassic? (252.2 to 201.3 Ma)
Lithology: Sedimentary
Group name: Marble and limestone of Wrangellia
A long narrow belt of nonfossiliferous, massive to thick-bedded, white to light-gray, fine-grained marble. Composed of nearly pure calcite, but locally contains accessory chlorite, sericite, graphite, quartz, albite, and pyrite (Johnson and Karl, 1985). Plafker and others (1976) and Jones and others (1977) correlate the Whitestripe Marble with the Chitistone Limestone (unit Trcnk) in the Wrangell Mountains and therefore considered it to be a part of the Wrangellia terrane along with the Goon Dip Greenstone (unit Trn). Unit was assigned a Triassic(?) age by Loney and others (1975) on the basis of a fossil found in float. Unit also includes the informally defined marble of Nakwasina Sound (unit Trm of Karl and others, 2015), which consists of light-gray, medium- to thin-bedded metalimestone, which is locally fossiliferous and retains primary bedding structures as well as massive to banded white marble, locally interlayered with volcanic rocks. Unit ranges up to tens of meters in thickness and is associated with volcanic and volcaniclastic rocks mapped in Nakwasina Sound (unit Trvs)

Source map information

Source map Karl, S.M., Haeussler, P.J., Himmelberg, G.R., Zumsteg, C.L., Layer, P.W., Friedman, R.M., Roeske, S.M.,and Snee, L.W., 2015, Geologic map of Baranof Island: U.S. Geological Survey Scientific Investigations Map SIM-3335, pamphlet 82 p., 1 sheet, scale 1:250,000.
Symbol Trm
Unit name Metalimestone
Description Light gray, medium- to thin-bedded metalimestone, which locally contains fossils and primary bedding structures, and massive to banded white marble, locally interlayered with volcanic rocks. Unit is ranges up to tens of meters in thickness. Metalimestone unit is associated with with volcanic and volcaniclastic rocks of Trsv. Mapped in Nakwasina Sound and north of Red Bluff Bay. Unit is depositionally associated with units Trg and Trsv. This limestone is older than the Norian Chitistone Limestone of the Wrangell Mountains, but correlates in age with limestone of the Carnian age Quatsino Formation on Vancouver Island. The association of the marble with Trg and Trsv, Pza and Pzsv, and the intrusion of all five units by Jurassic diorite that correlates with the Island Intrusions that intrude Wrangellian rocks on Vancouver Island, suggests that Trm, Trg, and Trsv are upper plate rocks to the Baranof accretionary complex, and that they correlate with Triassic rocks of Wrangellia
Lithology Metamorphic

Correlated geologic units

Label Trml
Description Marble of Nakwasina Sound
Geologic age Triassic
Geologic setting Melange
Lithology Form Importance
Melange < Tectonite Melange, blocks Major