Stratigraphy and Lithocorrelation of the Snowslip Formation (Middle Proterozoic Belt Supergroup), Glacier National Park, Montana
Whipple JW and Johnson SN. 1988. Stratigraphy and Lithocorrelation of the Snowslip Formation (Middle Proterozoic Belt Supergroup), Glacier National Park, Montana. U.S. GEOLOGICAL SURVEY BULLETIN 1833. United States Geological Survey. Denver, Colorado
The Snowslip Formation is in the upper part of the Middle Proterozoic Belt Supergroup; it is exposed in the central and western parts of Glacier National Park and composed mostly of fine-grained, terrigenous clastic rocks that were deposited about 1,200 Ma in a paralic, mixed siliciclastic-carbonate environment. In the northern part of the Park, the Snowslip Formation contains the Purcell Lava, which is a series of thin mafic flow units that are absent from the type section in the southern part of the Park. Because of the importance of the Purcell Lava as a time line in the Belt, a reference section is established at Hole-in-the-Wall in the northern part of the Park and subdivided into six informal members. The uppermost member (member 6) encloses the Purcell Lava. Lithocorrelation of members exposed in the reference section, the type section, and two other sections of the Snowslip in Glacier National Park indicates a northward thinning of stratigraphic units. Compositional analysis of framework grains in arenite units suggests that Snowslip sediments were multicyclic and had a cratonic source. Based on changes in mineralogy and facies and limited paleocurrent measurements, sediment transport direction was northwest with minor directional components west and southwest. Deposition of the Snowslip Formation was preceded by a period of erosion, interrupted by extrusion of the Purcell Lava, and punctuated by two episodes of fluvial sedimentation. These interruptions are interpreted to be related to periods of active tectonism during sedimentation. A polarity reversal is coincident with a disconformity at the base of the Snowslip.
- Type
- Published Report
- Authors
- Whipple, James; Johnson, Sue
- Date of Issue
- 1988
- Publisher
- United States Geological Survey
- Units
- CRCO , GLAC , HIST
- Keywords
- ehistory, Formation, Glacier, Glacier National Park, History, Lithocorrelation, Montana, National Park, Proteozoic, Snowslip, Stratigraphy, Superground