THE SNOWSLIP FORMATION OF GLACIER NATIONAL PARK AND THE BELT BASIN – RECENT OBSERVATIONS

Mesoproterozoic patterns of sedimentation at first appearance may seem monotonously repetitive. Some of the Belt Basin’s recognizable red bed mudstone formations, such as the Snowslip Formation exemplify the repetitive nature of the Belt’s extensive mudflat sediments. Fortunately, Dr. Don Winston provided us with his “Sediment Types” - a geologic Rosetta Stone, allowing us to interpret and understand the unique patterns of sedimentation found in the Proterozoic Belt Basin.

This presentation will discuss the Snowslip Formation found in Glacier National Park, its context within the eastern edge of the Belt Basin and across the Basin, and examine similarities to other Proterozoic red bed sequences, such as the Grinnell Formation. Examination of prevalent sediment types indicates these formations are best interpreted as broad, subaerial mudflats subject to shallow sheet-floods. Sheet-floods deposited significant coarse-grained oolitic sands, chaotic mud-chip rip-up clasts often including large mudballs (the Mud-Chip Breccia Sediment Type) and were capped by siltstones and mudstones as sheet-flood energy subsided. Periodic influx of coarse-grained oolitic sand deposits, seems to be a defining characteristic of most Belt strata on the eastern edge of the Basin in Glacier National Park.

The author will review previous work characterizing the Snowslip Formation, and include recent observations from geologic interpretive hikes, and personal climbs at elevation within the upper members of the Snowslip in Glacier National Park. It also seems that recent Mars explorations have suddenly brought red bed formations of the Belt Supergroup into sharper focus, worthy of comparison to processes on Mars - and not at all boring!