It has long been known that there was a lake in Death Valley during the Pleistocene (Lake Manly), but, because the evidence of its presence seemed meager, its age had been put at Tahoe (early Wisconsin). Later studies have suggested that the lake may have had two major stages as did Lakes Bonneville and Lahontan: the first during Tahoe time, and the second during Tioga (late Wisconsin) time. The second stage, represented particularly by Manly Terrace, the largest terrace remnant now known in the valley, is correlated with the Provo and Dendritic Terrace stages of the above-mentioned lakes.
On Manly Terrace several hundred crude artifacts have been found, forming an integral part of the stone pavement covering the surface. These are principally scrapers, with a few gravers, drills, and rude blades. They are made of materials occurring in the vicinity: rhyolite, chert, jasper, chalcedony. Obsidian is conspicuous by its absence. The workmanship is most primitive, many are waterworn, and all are highly patinated with desert varnish as are the other stones of the desert pavement.
In the writers' opinion early man made and used these artifacts when Lake Manly stood at this lower level. This would have been during the Tiogan subage of the Wisconsin age of the Pleistocene epoch.