Discover Canada and Explore the Fossils and Geodiversity of Cypress Hills in Alberta and Saskatchewan
- Wayne Munday
- Oct 13
- 5 min read
Sip back and discover Canada and explore the fossils and geodiversity of Cypress Hills, spanning the border of south east Alberta and south west Saskatchewan. Standing prominently above the northern Great Plains peaking at 2,782 metres on the Head of the Mountain near Crowsnest Pass. Unlike the tectonically formed Rocky Mountains, Cypress Hills is an erosional plateau, shielded by the resistant Cypress Hills Formation, which protects the softer underlying sediments. This plateau records a remarkable geological and fossil record documenting the retreat of the Western Interior Seaway during the Late Cretaceous and early Tertiary, through to the Pleistocene glaciations. The formation, spanning roughly 42 - 16 million years ago, consists of conglomerates, sandstones and gravels deposited by ancient braided rivers flowing from the retreating Rocky Mountains, capturing a transition from lush Eocene forests to the drier Miocene grasslands. Beneath the caprock, the Cypress Hills preserve a rich fossil record. While the older Frenchman Formation contains dinosaur fossils such as Triceratops and T. rex, the Cypress Hills Formation yields an exceptional Oligocene–Miocene mammal fauna includes early horses (Mesohippus, Parahippus, Hypohippus), camels, brontotheres, entelodonts, oreodonts, and early carnivores like Hemipsalodon. Fossil sites such as Calf Creek near Eastend, Saskatchewan, also preserve a diverse herpetofauna, reflecting Lower Oligocene subtropical wetlands. Fossils are commonly concentrated in channel lag deposits, where river flooding winnowed lighter sediments and preserved durable bones, teeth and shells. During the Late Wisconsinan glaciation, advances of the Laurentide, Cordilleran, and Innuitian ice sheets sculpted surrounding landscapes, yet the plateau’s upper 100 metres remained unglaciated as a nunatak. Meltwaters carved valleys, coulees and lakes while windblown loess settled across the summit, forming fertile soils that today support lodgepole pine forests and wildflower meadows.
Cypress Hills is located in south east Alberta bordering Saskatchewan. Rising high above the southern Alberta Prairie, part of the northern Great Plains, peaking at 2,782 meters on the Head of the Mountain near Crowsnest Pass. Also part of Cypress Hills Interprovincial Park, Canada’s first park jointly managed by two provinces, located about 70 Km southeast of Medicine Hat via Highway 41. The Alberta portion of the Park is called the Elkwater Block and the Saskatchewan portion is called the West Block. This is an area of Lodgepole Pine Forests, wildflower meadows, Aspen parkland and clear freshwater lakes such as Elkwater Lake. Having a mid-continental position within the Western Canada Sedimentary Basin Cypress Hills is also designated Dark-Sky Preserve located far from sources of light pollution.
Cypress Hills is an upland shared between Alberta and Saskatchewan and is not a mountain range but a vast erosional plateau. The resilience of this plateau at Cypress Hills stands prominently today while the surrounding landscape has been stripped down to older rocks. Its flat layered summit preserves an extraordinary rock and fossil record that tells a story of the advance and retreat of the Western Interior Seaway across the vast expanse of the Great Plains between the Rocky Mountains and the Mississippi River spanning parts of the central United States and southern Canada up to the Ice Age.
Cypress Hills were not created by tectonic compression or volcanic uplift like the Rocky Mountains but are the remnants of a once-extensive upland surface preserved by a resistant caprock called the Cypress Hills Formation. This caprock protects from erosion the softer rock below that collectively records the transition of a marine to terrestrial environment spanning from the Late Cretaceous into the early Tertiary. Over tens of millions of years, the surrounding plains were gradually worn away, leaving the plateau as a towering island of ancient sedimentary rock.
The Cypress Hills Formation dates from the Late Eocene to early Miocene between 42 – 16 million years ago. Composed mainly of conglomerate, sandstone and gravel deposited by an ancient network of rivers flowing over a gentle anticline that plunges eastward across a broad semi-arid floodplain away from the rising mountains of south west Alberta and north west Montana. Spanning several North American Land Mammal Ages (NALMA) or a geologic timescale for prehistoric North American mammals based on fossil evidence from the Uintan to Hemingfordian.
This interval of 30 million years between the Uintan and Hemingfordian of North American Land Mammal Ages (NALMA) spans a critical transition from the Eocene through the Oligocene and into the Miocene epochs capturing major environmental and climate change and animal migration in North America. The region shifted from lush Eocene forests to the cooler, drier grasslands of the Miocene. Erosion from the Rocky Mountains supplied vast amounts of sediment that accumulated in extensive braided river systems.
The fossil record beneath the protective caprock of the Cypress Hills tells a story of the transition from the "Age of Dinosaurs" to the "Age of Mammals" in western Canada. This NALMA interval also marks a significant turnover in mammals with the extinction of many archaic species and the emergence of more modern groups such as early horses, camels and carnivores that adapted to an open semi-arid grassland. Whilst the older Frenchman Formation is renowned for yielding the fossil remains Triceratops and even T rex, notably "Scotty" the Cypress Hills Formation preserves an exceptional Oligocene–Miocene mammals.
These river gravels and sands have yielded woodland–grassland ecosystem fossils of early horses (Mesohippus, Parahippus, Hypohippus), camels, rhinoceros-like brontotheres known as Megacerops or "Thunder beast", entelodonts like Cypretherium coarctatum, oreodonts including Merycoidodon and early carnivores such as Hemipsalodon.
Interestingly, a Cypress Hill at Calf Creek near Eastend, Saskatchewan preserves a diverse herpetofauna fossil assemblage including salamander, frogs, turtles, crocodilians, lizards and snakes. Among the fossils are newly described genus and species of iguanid lizard and a small boid snake. This mix of herpetofauna further indicates a subtropical to tropical wetland climate during the Lower Oligocene.
Many fossil assemblages are linked to the process of winnowing during flooding and are found preserved in river channel lag deposits. When the rivers flowed during the floods the water removed the lighter sand and mud leaving behind heavier and more durable rocks, stones, plant debris as well as bones, teeth and shells. As finer sediment particles are carried away the heavier fossil-bearing material concentrated in the channel forming a lag deposit.
Below the uppermost Cypress Hills Formation is a sequence of sedimentary strata that collectively record the transition from marine to terrestrial environments across the Late Cretaceous and early Tertiary. Beneath the Cypress Hills Formation lies the Ravenscrag Formation deposited during the early Paleocene epoch recording the crucial interval immediately after the Cretaceous–Paleogene (K–Pg) mass extinction that marked the end of the dinosaurs. Below the Ravenscrag Formation are the Late Cretaceous Frenchman, Whitemud, Eastend and Bearpaw formations that track the final retreat of the Western Interior Seaway which is also told in Eastend (Saskatchewan).
During the Pleistocene Laurentide, Cordilleran and Innuitian Ice Sheet advances and retreats between approximately 30,000 to 11,700 years ago sculpted the landscapes across the North America though the ice sheets and in particularly the Etzikom, Altawan and Pakowki advances of the Late Wisconsinan Glaciation that have shaped the landscape of much of southern Alberta and Saskatchewan appears to have flowed around Cypress Hills and did not completely cover them.
The plateau’s upper 100 metres remained unglaciated forming a "nunatak" or isolated peak that projected through a continental ice sheet. Glacial meltwaters carved deep valleys and coulees such as Battle Creek and Medicine Lodge Coulee while the surrounding plains were mantled with glacial till and erratic boulders. Loess of fine windblown silt settled across the unglaciated summit of Cypress Hills creating fertile soils that support the forests we see today.
