Presenter Information

Kyle BrangersFollow

Presentation Type

Poster

Abstract

This study focuses on documenting and interpreting the sedimentology of a set of gravel deposits presently exposed along Snowbowl Road approximately 1.5 kilometers above the intersection of Snowbowl Road with the Grant Creek Road. The gravel deposit is exposed on the north side of the road in a series of artificial exposures which were cut in the 1950’s when the Snowbowl Road was constructed. The deposit consists of a set of discontinuous exposures along ~100 meters of the road, and roughly 6 meters of stratigraphy is exposed. The main gravel deposit is dominated by pebble-sized clasts that are typically angular and oblate. Sand is present but not ubiquitous. Much of the gravel is characterized by an open framework. Pebble imbrication is locally present in some of the beds. Bed thicknesses are generally centimeter to decimeter scale and bedding contacts include both sharp and gradational varieties. The gravel deposits are also characterized by cut and fill structures that measure up to ~ 30 meters across and ~ 4 meters in height. In addition to the main gravel deposit exposed in the road cut is a smaller fan-shaped deposit located at the thalweg of a small drainage and composed of several layers of poorly-sorted, locally matrix-supported conglomerate. The smaller fan-shaped deposit is interpreted to have formed as a result of sediment transport during large flow events and deposition onto the flat roadway. The main gravel deposit is preliminarily interpreted to represent shoreface erosion and deposition along a gravel beach associated with glacial Lake Missoula.

Category

Physical Sciences

Share

COinS
 
Apr 15th, 11:00 AM Apr 15th, 12:00 PM

Documenting the sedimentology of an unusual set of gravel deposits exposed along Snowbowl Road

This study focuses on documenting and interpreting the sedimentology of a set of gravel deposits presently exposed along Snowbowl Road approximately 1.5 kilometers above the intersection of Snowbowl Road with the Grant Creek Road. The gravel deposit is exposed on the north side of the road in a series of artificial exposures which were cut in the 1950’s when the Snowbowl Road was constructed. The deposit consists of a set of discontinuous exposures along ~100 meters of the road, and roughly 6 meters of stratigraphy is exposed. The main gravel deposit is dominated by pebble-sized clasts that are typically angular and oblate. Sand is present but not ubiquitous. Much of the gravel is characterized by an open framework. Pebble imbrication is locally present in some of the beds. Bed thicknesses are generally centimeter to decimeter scale and bedding contacts include both sharp and gradational varieties. The gravel deposits are also characterized by cut and fill structures that measure up to ~ 30 meters across and ~ 4 meters in height. In addition to the main gravel deposit exposed in the road cut is a smaller fan-shaped deposit located at the thalweg of a small drainage and composed of several layers of poorly-sorted, locally matrix-supported conglomerate. The smaller fan-shaped deposit is interpreted to have formed as a result of sediment transport during large flow events and deposition onto the flat roadway. The main gravel deposit is preliminarily interpreted to represent shoreface erosion and deposition along a gravel beach associated with glacial Lake Missoula.