Foremost Formation

Foremost Formation Stratigraphic range: Campanian, 78.5–77.5 Ma PreЄ Є O S D C P T J K Pg N ↓
Outcrops of the Foremost Formation (basal sandstone and MacKay coal zone) along the Milk River at Writing-On-Stone Provincial Park
Type	Geological formation
Unit of	Belly River Group (Judith River Group)
Underlies	Oldman Formation
Overlies	Pakowki Formation
Thickness	up to 170 metres (560 ft)
Lithology
Primary	Sandstone, siltstone, mudstone
Other	Shale, coal
Location
Region	Alberta
Country	Canada
Type section
Named for	Foremost, Alberta
Named by	D.B. Dowling, 1915

The Foremost Formation is a stratigraphic unit of Late Cretaceous (Campanian) age that underlies much of southern Alberta, Canada. It was named for outcrops in Chin Coulee near the town of Foremost and is known primarily for its dinosaur remains and other fossils.

The Foremost Formation is the basal unit of the Belly River Group (called the Judith River Group in the United States). It gradationally overlies the marine shales of the Pakowki Formation. It consists of sediments that were eroded from the mountains to the west and carried northeastward by river systems, where they gradually prograded into the Western Interior Seaway.

The bottom of the formation typically consists of a basal sandstone unit overlain by the interbedded coal seams, carbonaceous shales and mudstones of the Mackay coal zone. The center portion consists of interbedded sandstones, siltstones and mudstones, with minor carbonaceous shales. At the top are the interbedded coal seams, carbonaceous shales and mudstones of the Taber coal zone. The basal sandstones, which are commonly referred to as the Basal Belly River Sand, are a significant hydrocarbon reservoir in some parts of Alberta.

The Foremost Formation outcrops along the Milk, Oldman and Bow Rivers. It is about 168 metres (550 ft) thick near Lethbridge,107 metres (350 ft) thick near Medicine Hat, and 170 metres (560 ft) thick at Dinosaur Provincial Park.