Calcareous paleosols in the Triassic Dolores Formation, southwestern Colorado

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6594456

Blodgett, R H

Calcareous paleosols are common in the upper member of the Upper Triassic Dolores Formation in the San Juan Mountains of southwestern Colorado. These soils are best developed in the upper portion of 2 to 10m-thick beds of very fine sandstone to coarse siltstone. The sandstone/siltstone beds represent sand sheet facies deposited by eolian and aqueous processes on the margins of a large Triassic erg. Textures and structures associated with these paleosols include individual and stacked micrite and microspar nodules, downward-branching purple and green mottle in reddish brown parent rock, irregular polygonal fractures filled with sparry calcite or red mudstone, 3 to 15mm-diameter tubular meniscate burrows (striotubules of the trace fossils Scoyenia, Ancorichnus, and Muensteria), and hematite-pigmented skelsepic fabric. Cross-cutting and replacement relationships between burrows and carbonate nodules indicate that bioturbation and glaebule development were penecontemporaneous. Classification of these soils using the USDA or FAO/UNESCO systems is complicated by burial diagenesis. Clay accumulation has probably occurred both by pedogenic illuviation and intrastratal solution. The development of a calcic horizon in a loam in tropical paleolatitudes prior to the evolution of grasses constrains the classification of these soils. Possibilities include assignment of these paleosols to ustropepts, xerochrepts, or orthids, and locally to ustalfs or argids.

• Research Organization: Ohio State Univ., Columbus (USA)
• OSTI ID: 6594456
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COLORADO
SANDSTONES
SILTSTONES
SOILS
DIAGENESIS
PALEOCLIMATOLOGY
TEXTURE
CALCITE
CLASSIFICATION
FOSSILS
GEOLOGIC FORMATIONS
LITHOLOGY
STRATIGRAPHY
TRIASSIC PERIOD
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGY
MESOZOIC ERA
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PALEONTOLOGY
ROCKS
SEDIMENTARY ROCKS
USA
580100* - Geology & Hydrology- (-1989)