Unit Name: Prongs Creek Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Early Devonian - POSSIBLE Late Devonian (416 - 359.2 ma)
Age Justification: The two lower divisions contain numerous fossils comprising colonial and rugose corals, brachiopods, cephalopods, goniatites, ostracodes, echinoderm fragments, tentaculitids and conodonts. The upper division is largely barren of megafossils except for sparse tentaculitids.
Province/Territory: Yukon Territory
Originator: A.W. Norris, 1968.
Type Locality:
Along Royal Creek at 65 deg 02' -04'N, 135 deg 08'-10'W near the middle of its basin of deposition where the formation is thickest.
Distribution:
The formation is mainly developed in a narrow northtrending belt extending from south of latitude 65 deg N to about latitude 67 deg 34'N and coincides roughly with part of the Richardson Mountains uplift. The belt is widest in the south where it extends from Trevor and Knorr ranges in the east, to the northern end of Wernecke Mountains in the west. Thickness ranges from a maximum of 751+ m (2,464+ ft) at the type locality, to 65 m (212 ft) on lower Porcupine River.
Lithology:
A three-fold lithological division is apparent in the thicker sequences of the formation. A lower division consists mainly of dark grey to black shales with widely spaced thin interbeds of limestones and argillaceous limestones. A middle division consists of interbedded shale and limestone, in part argillaceous and slightly cherty. An upper division consists of interbedded shale and black chert. Northward the formation consists of interbedded shale and chert.
Relationship:
Transitionally overlies shales of the Road River Fm and is overlain by dark grey silty shales of thee Canol(?) and Imperial formations. On lower Porcupine River the Prongs Creek is separated by an angular unconformity from overlying conglomeratic beds of Permo-Pennsylvanian age. The lower boundary was originally tentatively drawn immediately above the highest occurrence of monograptids but in the light of more recent work this boundary is best drawn at the first appearance of prominent limestone beds. The Prongs Creek is closely comparable to the McCann Hill Chert of the Nation River area in southeastern Alaska (Churkin and Brabb, 1965). Because of the transitional lower boundary some recent workers have treated the Prongs Creek as part of the Road River Fm.
Other Citations:
Churkin and Brabb, 1965; D.E. Jackson et al., 1978; Lenz and D.E. Jackson, 1971; A.W. Norris, 1967a, 1967b, 1968; Perry, 1979; Uyeno and Mason, 1975.
Source: CSPG Lexicon of Canadian Stratigraphy, Volume 2, Yukon Territory and District of Mackenzie; L.V. Hills, E.V. Sangster and L.B. Suneby (editor)
Contributor: D.W. Morrow; A.W. Norris
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Apr 2003