Extract ability of humic acid from coalified logs as a guide to temperatures in colorado plateau sediments

Coalified logs in Triassic and Jurassic sediments of the Colorado Plateau have been exposed to alkaline ground water. Extraction of humic acids under such conditions is temperature dependent. Study of residual humic acids in a suite of coalified logs has indicated that temperatures up to but not over 120° C prevailed in the sediments. This maximum temperature corresponds with that to be expected from geothermal gradient and estimated from mineralogic evidence.