PETROLOGY OF EOCENE ROCKS OF ANTIMONY AND DRY CANYONS, SOUTHWESTERN UTAH

Stratigraphic sections were measured and petrographic samples were analyzed from three stratigraphic units which unconformably overlie deformed Jurassic Carmel Formation. These units were previously mapped as Flagstaff Formation. The lowest unit, A, is approximately 84 m thick, is stained red by iron oxides that transect bedding planes low to midway through the unit, and consists of layers of calcareous sandstones, siltstones, and conglomerates. Sandstones low in the unit contain fine, sub-angular and sub-rounded quartz grains, with calcite cement—contrasting with the calcareous mudstones found higher in the unit. Unit B, approximately 117 m thick, has a conglomerate of varying thickness downcutting into the top of unit A. Unit B includes layers of siltstones, silty carbonates, sandstones, and conglomerates. The sandstones are fine grained, well-sorted, quartz arenites with calcite cement. The contact between unit B (a quartzite conglomerate) and the base of the uppermost unit (C) is often covered by white, sandstone talus. Unit C, of which only the lower 38 m were measured, generally coarsens towards the northwest with layers of sandy limestones, siltstones, and conglomerates. To the south, it is more carbonate-rich and locally contains fossils including the planorbid gastropod Biomphalaria sp. and the pluerocerid (?)Elimia sp. that are both common in the lower to middle Eocene. The petrology of these units are very different from those of the type area of the Flagstaff Formation but do have lithologic similarities to the lower part of the Claron Formation, which is present approximately 28 kilometers south of Antimony Canyon.