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Gething Alluvial Plain

Deposition was resumed in Gething time, following the supposed
Kootenay emergence, and a wide alluvial plain, with, at times, coal swamps
and temporary ponds or ‘playas’, occupied the site of the Rocky Mountains,
Foothills, and Plains as far north as Pocketknife River in northeastern
British Columbia and far to the east into Alberta. It was coextensive with
the Luscar alluvial plain, with its coal swamps, in the central Canadian
Foothills, with the Lower Blairmore alluvial plain of southwestern Alberta,
and, perhaps, with the ‘Varicoloured’ alluvial plain in southern Alberta. Itis
not known whether the Gething plain continued into eastern Alberta.
In 1932, McLearn mapped this plain as marginal to an early stage of the
Clearwater or Lemuroceras sea. In 1944, it was mapped as coextensive
with the McMurray alluvial plain. More exact correlation of the Peace
River with the Athabasca River section is required before this palzogeo-
graphic problem can be settled.

Luscar Sea

No marine fossils have yet been found in the Gething formation in the
Foothills. Farther east, however, in the Pouce Coupé area, beds encoun-
tered in the section of the Guardian well, and correlated by Allan and
Stelck with the Gething, contain not only coal and plant remains, but
glauconite, thus recording marine or brackish water as well as non-marine
environments. McLearn (1944) has shown that evidence of marine or
brackish water habitat is recorded in places by the Luscar formation and
its correlatives, and that a sea at this time lay somewhere in the interior
Yen (1949) considers that the Lower Blairmore and Luscar formations
are partly of marine or estuarine origin. This sea may have been of
Aptian or very early Albian (late Lower Cretaceous) age and perhaps
older than the Lemuroceras or Clearwater sea.

Marine Invasions from the North

The seas recorded by the marine beds of the late Lower Cretaceous
(Albian) Fort St. John group spread not only over the Foothills and Plains
of northeastern British Columbia, but over large areas on the site of northern
and central Alberta as well, and at times may have extended far to the
south, even into southern Alberta and Saskatchewan.

They were northern seas, inundations from the Arctic Ocean (McLearn,
1932, 1944) southward across the site of Mackenzie River Valley. They
did not extend west of the Trench, being separated from the Pacific Ocean
by a land barrier. Nor did they extend far enough south to join the late
Lower Cretaceous seas that spread northward from the Gulf of Mexico.

These Fort St. John seas included the Lemuroceras, Gastroplites,
(Haplophragmoides gigas), and N eogastroplites inundations. The exact age
of the H. gigas sea, named for a species of foraminifera, is not known, but
may be later than the Gastroplites sea. It appears to have had the maxi-
mum southern expansion to the International Boundary in Saskatchewan,
where it has been recorded by Wickenden (1932). The Lemuroceras
fauna has not yet been recorded south of Athabasca, River, nor the Gas-
troplites fauna south of the Pine, at least not in print.