The Bolsa Quartzite varies in thickness from about 50 feet to over 500 feet. It is thickest in the Huachuca Mountains, and laps out to zero thickness to the north against the Precambrian basement rocks. Sedimentary structures include parallel and cross laminations, cross bedding, color banding, and biogenic trace fossils such as Scolithos and Correphioides. We have not observed any trilobite traces as of yet. The silicaceous cement in the sandstone is very hard and so tightly bonded that it is difficult to see individual grains.
Fossils are very difficult to remove, and usually results in the rock fragmenting into splinters.
In a few localities, polygonal mud cracks have been reported, which we were able to confirm in outcrops near Sierra Vista. Image 1 Typical outcrop of Bolsa Quartzite from the Benson Area in Southern Arizona. It is normally a light brown with bands up to 12 inches thick of a lighter coloration. This is a Tidal flat and near shore deposit in shallow water since we found abundant Correphioides trace fossils at this locality. Another view of the Bolsa in the bottom of a creek in a deep canyon.