Pleistocene Glaciation in the Southern Part of the North Cascade Range, Washington Previous Studies

Pleistocene Glaciation in the Southern Part of the North Cascade Range, Washington

Previous Studies

Stratigraphic Usage

• Sediments resulting from an ice advance were collectively mapped as drift including till, erratics outwash, lacustrine sediments, and ice-contact stratified drift.
• Glacial-stratigraphic units have been used to designate the principle glacial and nonglacial episodes.
• The bulk of preserved interglacial deposits are constituted of loess, colluvium, alluvium, and landslide sediments.

Criteria Of Age

• 1)Those that are time dependent and permit relative ages to be assigned on the basis of a progressive change in degree of weathering, erosion, mass wasting, or extent of vegetation cover with increasing age of deposits

Weathering Rinds

Loess Thickness

Soils

• Soil profiles on each major drift sheet were sampled at 10 cm intervals. Subsequent laboratory determinations included grain-size analyses, pH, percentage of magnetic minerals, and moist color. Grain-size was clay-silt, pH tends to be slightly acidic (5-7), there were not significant percentages of magnetic minerals, the younger soils tend to be yellowish-brown and the older ones a reddish color.

Moraine and Terrace Relationships

Upper Yakima River Drainage Basin

Possible Pre-Thorp Drift

Thorp Drift

Kittitas Drift

Swauk Prairie Member

Indian John Member

Post-Kittitas Soil

Lakedale Drift

Bullfrog Member

Ronald Member

Domerie Member

Hyak Member

Lakedale Loess

Holocene Sediments

Post-Lakedale Soils

Drift of the Puget Lobe

Pre-Vashon Drift

Vashon Drift

Chronology and Regional Correlations