Mistaken Point Formation

Unit Name: Mistaken Point Formation
Unit Type: Lithostratigraphic
Rank: Formation
Status: Formal
Usage: Currently in use
Age Interval: Proterozoic III (900 - 541 ma)
Age Justification: The age of the formation is inferred from its stratigraphic position and fauna. Age and fauna are discussed by Anderson and Misra (1968); Misra (1969a, 1969b, 1971), Ander-son (1972), Williams and King (1979), King (1980), Anderson and King (in King, 1982), Anderson and Morris (1982), O'Brien et al., (1983). At the type section on Mistaken Point, the formation is probably fossiliferous with a variety of frond and disc-like impressions. Most of the fossils resemble Charniodiscus concentricus Ford (1958) and Cyclomedusa davidi Sprigg, a rare variety; Char-nia masoni Ford (1958), a medusoid, also occurs (in Williams and King, 1979). These are all Vendian (Late Proterozoic III) in age.
Province/Territory: Newfoundland & Labrador

Originator: Williams and King, 1979.

Type Locality:

Mistaken Point to about 1 km west in coastal cliffs of Trepassey Bay, southern Avalon Peninsula, Newfoundland (NTS 1 K/11).

Distribution:

The formation is about 400 m thick. The distribution is shown on the Avalon Peninsula map of King (1980, Figure 1). A western belt extends from Harricott (NTS 1 N/4), St. Mary's Bay, to Broad Cove (NTS 1 N/4), Carbonear. In the Trepassey area the formation is ex-posed in coastal sections of the St. Shott's (NTS 1 K/12), Biscay Bay (NTS 1 K/14), and Cape Race (NTS 1 K/11) synclines. An eastern belt is exposed in coastal headlands between Cape Race and Torbay (NTS 1 N/10). Maps showing the distribution are found in Williams and King (1979) and King (1980, 1982, 1984).

Lithology:

At its type section on Mistaken Point, red, green, and purple shale are interlayered with thinly to medium bedded, green, grey to pink siliceous sandstone, and minor tuff. In general, the base of the formation is defined by graded medium-bedded sandstone, the top by red shales. Late Proterozoic fossils are found throughout the formation but mainly towards the top, beneath dark thin tuff horizons that are less than 1 cm thick.

Relationship:

The Mistaken Point Formation overlies the Proterozoic III Briscal and Drook formations of the Conception Group, and is conformably overlain by the Proterozoic in Tre-passey Formation of the St. John's Group. At the type locality, thickly bedded grey to olive Briscal sandstones are gradationally overlain by green to red sandstones of the Mistaken Point Formation with a gradational zone of 50 to 75 m thick. In the northern Avalon Peninsula, the Briscal Formation pinches out and the Mistaken Point Formation rests directly on the Drook Formation. The Conception Group includes, in ascending order, the Mall Bay, Gaskiers, Drook, Briscal, and Mistaken Point formations.

History:

Rocks of the Mistaken Point Formation were first described by Murray in his report for 1868 (Murray and Howley, 1881b, pp. 144-145) as part of the "green, purplish or red slates" of unit "c." The first organic remains within these rocks were found by Rev. Moses Harvey (Murray and Howley, 1881b, pp. 144-145). Walcott (1899) informally introduced the name "Torbay Slate" for the upper part of unit c around Torbay. This now includes several formations. Hutchinson (1953) defined the "Hibbs Hole Formation", a 137 m thick unit, near the top of the Conception Group in central Avalon Peninsula. Misra (1971) proposed the name "Cape Cove Formation" for rocks of the upper Conception Group. Williams and King (1979) divided the "Cape Cove Formation" into three formal units (Briscal, Mistaken Point, and Trepassey formations), each mappable on a regional scale. The name Cape Cove Formation was abandoned. The Hibbs Hole Formation was considered by Williams and King (1979) as a correlative of the upper part of the Mistaken Point Formation. They believed it was impractical to map the former in the eastern Avalon Peninsula as it was too small a unit.

Other Citations:

Anderson, 1972; Anderson and Misra, 1968; Anderson and Morris, 1982; Hofmann et al., 1979; Howley and Murray, 1918; Hutchinson, 1953; King, A.F., 1980, 1982, 1984; McCartney, 1967; Misra, 1969a, 1969b, 1971; Murray and Howley, 1881a, 1881b; O'Brien et al., 1983; Walcott, 1899; Williams and King, 1979.

Source: CSPG Lexicon of Canadian Stratigraphy, Volume 6, Atlantic Canada; G.L. Williams, L.R. Fyffe, R.J. Wardle, S.P. Colman-Sadd, Boehner, R.C. (editor)
Contributor: A.F. King
Entry Reviewed: Yes
Name Set: Lithostratigraphic Lexicon
LastChange: 29 Apr 2003