28

They are included in Williams’ ‘Silurian and Devonian’ unit, and
comprise about 50 feet of limy shale, with worm burrows, below, and coral
reef limestone, above, on the west side of Muncho Lake; brown weathering
fine-grained quartzite, overlain by interbedded blue limestone and quartzite
and a 50-foot coral-reef limestone, on McDonnell Creek; and limestone,
partly coralline, and sandstones, a few to 70 feet thick, on Mount St. Paul
and west of this mountain.

Laudon and Chronic place these Middle Silurian strata in the Ronning
formation, on the assumption that this formation of the lower Mackenzie
River Valley extends this far south. They state that it consists of more
than 1,200 feet of massive, grey, dolomitic limestone, thin-bedded, black,
shaly limestone, and some chert. The Middle Silurian age is based on
corals in the coralline limestones.

UNFOSSILIFEROUS DEVONIAN (?) LIMESTONES
Alaska Highway

Williams (1944) notes that light grey limestone, apparently unfos-
siliferous, lies between the coral-reef limestones of Middle Silurian and
Middle Devonian age, on the Alaska Highway. Laudon and Chronic
(1947, 1949) recognize three, unfossiliferous, lithological units between the
Middle Silurian and Middle Devonian coralline limestones. The lowest
unit, called the McConnell formation, consists of about 680 feet of grey
and black, hard limestone and some shale, and has disconformable relations
with beds above and below. Above this hard limestone they record a
second unit, called the Muncho formation, consisting of about 600 feet of
grey and black, hard, laminated, silty, shaly limestone, and massive lime-
stone with, in places, a thin conglomerate at the base. Each of these
unfossiliferous units is included in the Devonian. <A third unfossiliferous
unit is recognized by Laudon and Chronic, and is assigned by them to the
Ramparts formation of lower Mackenzie River Valley. It consists of
about 500 feet of thin-bedded, yellow to tan siltstones and silty and sandy
limestones. It rests unconformably on the beds of the second unfossil-
iferous unit, noted above, and is conformable with the overlying Middle
Devonian, fossiliferous limestones, also included by Laudon and Chronic
in the Ramparts formation.

DEVONIAN
Peace River Valley

Black limestone occurs on a small, rocky island in the channel of
Peace River, about 3 miles above the mouth of Clearwater Creek. Fossils
include corals, brachiopods, and gastropods of late Middle Devonian age
(Williams and Bocock, 1932).

_ Rocks similar to the above are found on the north bank of Peace
River, 1 mile below the mouth of Wicked River. Massive, white lime-
stones on the east slope of Wicked River Valley are also thought by Williams
and Bocock to be of Devonian age.

Pine River Valley

Williams and Bocock describe Devonian beds from Pine River Valley,
where possibly as much as 2,000 feet of limestones outcrop on the west slope