Use of Soils to Identify Glacial Deposits of Various Ages East of Glacier National Park, Montana, U.S.A.

Abstract

Degree of soil development increases with age of parent materials in the zone of confluence of continental and alpine piedmont glaciers east of Glacier National Park, Montana. Surficial deposits are assigned to three, possibly four, glacial events on the basis geomorphic and pedologic evidence. Based on over 100 profiles examined, soils in late Wisconsin till and outwash are typically Cryoborolls and Cryochrepts with 0- to 62-cm-thick, brown cambic (Bw) horizons and 50+- cm-thick calcic (Bk) horizons with Stage II to II+ carbonate morphology. Soils in late Illinoian or early Wisconsin sediments are Argiborolls or Argic Cryoborolls with 34- to 92-cm-thick, dark yellowish brown argillic (Bt) horizons and those in Illinoian sediments are strongly developed Paleudolls with 51- to 54-cm-thick, yellowish red argillic horizons. Soils on Number 1 and 2 Bench remnants (considered Pliocene to early Pleistocene in age) are very strongly developed Paleudolls with about 2.5-m-thick, leached, yellowish red argillic horizons. Properties which best reflect relative soil age include thickness of argillic horizon, depth of leaching, depth of oxidation, Harden profile index, Harden rubification index, and clay accumulation index.