Thin-bedded limestone

Unit symbol: DOls
Age range Lower Devonian to Ordovician (485.4 to 393.3 Ma)
Lithology: Sedimentary
Group name: Thin-bedded limestone
“Thin-bedded to massive, fine-grained gray limestone, highly fractured and veined with white calcite, contains algal reefs and reef breccia. Locally contains interbedded tuffs and mafic volcanic rocks. Recrystallized to marble with interbedded quartzite and quartz-chlorite schist * * *” Hoare and Coonrad (1978). Algal mounds indicate shallow-water deposition (Decker and others, 1994). Unit is in scattered outcrops along a north-northeasterly trend from Goodnews Bay to the northern edge of the Goodnews Bay quadrangle. Unit thrust over Permian limestone (unit Ptls) and calcareous schist unit (unit JPs) and intruded by gabbro of Jurassic or Triassic age (included in unit J^os). Hoare and Coonrad (1978) reported sparse fossils of Middle Devonian to Early(?) Ordovician age. One sample collected by Stephen Box in northern part of the Goodnews Bay quadrangle boundary contained conodonts of Early Ordovician age (sample 89AJM60A, www.alaskafossil.org). A sample collected by J.M. Hoare contained ostracodes, echinoderms, fragments of brachiopods, algae, and small colonies of tabulate coral, possibly the genus Dania of Silurian age (A.K. Armstrong, written commun., 1975) Unit was included in the Goodnews terrane by Box (1985)

Source map information

Source map Wilson, F.H., and Hults, Chad, 2006, Unpublished data.
Symbol DOl
Unit name Limestone
Description Thin-bedded to massive, fine-grained, highly fractured limestone. Local interbedded tuffs and mafic volcanic rocks. Locally recrystallized to marble.
Lithology Sedimentary

Correlated geologic units

Label DOl
Description Thin-bedded to massive, fine-grained, limestone with local interbedded tuff and mafic volcanic rocks
Geologic age Ordovician to Early-Devonian
Geologic setting Sedimentary, carbonate
Lithology Form Importance
Limestone < Carbonate < Sedimentary Bed Major
Volcanic < Igneous Pyroclastic, tuff Incidental
Mafic-volcanic < Volcanic < Igneous Flow Incidental