It is locally fossiliferous and includes remains of marine animals such as brachiopods[2] and conodonts.

It has a maximum thickness of about 100 metres (330 ft), and is thinner in areas where it covers carbonate buildups (reefs) in the underlying formations.

[1] The Alexo Formation is present in the central Rocky Mountains of Alberta and the adjacent foothills, extending from the Crows Nest Pass area in the south to the North Saskatchewan River in the north.

[1][5] The Alexo was originally considered to extend as far north as Jasper but was revised by McLaren and Mountjoy in 1962.

In the area between the North Saskatchewan River and Jasper, they designated the upper beds of the Alexo as the Sassenach Formation, and the lower beds as part of the upper Southesk Formation.