Ogilvie Formation

Unit symbol: Dof
Age range Middle to Lower Devonian (419.2 to 382.7 Ma)
Lithology: Sedimentary
Group name: Shallow-marine, carbonate-dominated rocks
Massive, medium-gray, bioclastic limestone contains coral-stromatoporoid buildups. Thickness ranges from 60 to 1,100 m (Clough and Blodgett, 1984, cited by Dover, 1992; see also Clough and Blodgett, 1987). Unit has a similar distribution to the shallow-marine carbonate rocks of unit DSld above, but its upper limit may be slightly older than DSld. Unit was originally defined in Yukon of Canada by Norris (1967) and “Consists of medium-brown to grey, fine-grained, in part skeletal and reefal, thin-bedded to massive, resistant, cliff-forming limestones generally weathering light grey. Scattered argillaceous material and silt and chert are present in some beds. Dolomite is present in the lower part of the formation in the Nahoni Range area and in some sections east of the Blackstone River.” It contains a “moderately abundant fauna [that] includes sponges, stromatoporoids, tabulate corals, brachiopods, cephalopods, gastropods, pelecypods, goniatites, cricoconarids, ostracodes, trilobites, echinoderm fragments and conodonts” (Norris, 1967). Also included here is the Schwatka unit of Weber and others (1992), which consists of slightly recrystallized, dark-gray, sparsely fossiliferous, medium-bedded to massive lime mudstone or wackestone. Conodonts and two-holed crinoid ossicles constrain age to Emsian to Eifelian (Weber and others, 1992). Interfingers with volcanic rocks of unit Dvec. Weber and others (1992) interpreted the depositional environment as shallow marine. North of the Tinitna Fault, the unit crops out in the Charley River quadrangle and in the Yukon; south of the Tintina Fault, it occurs in the Circle and Livengood quadrangles

Source map information

Source map Brabb, E.E., and Churkin, Michael, Jr., 1969, Geologic map of the Charley River quadrangle, east-central Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-573, 1 sheet, scale 1:250,000.
Symbol Dwl
Unit name Woodchopper Volcanics, limestone
Description Dark-gray bioclastic limestone with brachiopods, corals and other fossils of Middle Devonian age. The relation of the limestone to the volcanic rocks is uncertain. A few hundred feet thick
Lithology Sedimentary

Correlated geologic units

Label Ds
Description Schwatka unit -- Limestone and Ogilvie Formation of Clough (1980), Middle and Early Dev.
Geologic age Devonian to Middle-Devonian
Geologic setting Sedimentary, carbonate
Lithology Form Importance
Limestone < Carbonate < Sedimentary Bed Major
Dolostone < Carbonate < Sedimentary Bed Minor
Shale < Mudstone < Clastic < Sedimentary Bed Incidental