Argillic Horizon Formation in late Wisconsinan Eolian Materials in Southwest Colorado, U.S.A

Abstract

Argillic horizons with reddish hues were studied in Haplargids and Argiborolls across an elevation transect. The eolian parent materials were deposited in two, or more episodes. The younger deposit, late Wisconsinan, was 14 C dated from a buried musk ox (Symbos cavifrons) at Grass Mesa as beginning about 16,000 ybp. The late Wisconsinan soil at this site and those at lower elevations have illuviation argillans coating and bridging sand grains. Maximum clay content of the late Wisconsinan soil at Grass Mesa is 22% vs. 13% in the eolian parent material. In the bisequal Monticello pedon above Grass Mesa, the late Wisconsinan argillic horizon has common illuviation argillans in channels and voids. In higher upper parts of the transect where the deposits are thin and clay contents reach 35%, plasmic fabrics in the argillic horizons have vosepic, masepic, and skelsepic areas. In the late Wisconsinan soils, depth to carbonate corresponds to the average annual maximum depth of wetting suggesting that these soils could have formed in a climate much like that of today's.