Manix Basin Artifact Assemblages
Three separate assemblages of lithic artifacts can be distinguished in the Manix Basin. The youngest are Indian and Paleo-Indian, consisting of pottery sherds, spear points, arrowheads, knives, and debitage, all of which lie loose on the surface, and lack significant discoloration by iron- and manganese-rich rock varnish. Such artifacts may range in age from 200 years to a maximum of about 8,000 years.
Clearly older is the Lake Manix Lithic Industry, including artifacts found on and just below the surface at elevations above 543 m, the shoreline elevation of Pleistocene Lake Manix, which drained approximately 18,000 years ago. Artifacts of the Lake Manix Lithic Industry exhibit rock varnish patinas on both their buried and exposed surfaces and are often found embedded in desert pavements, unlike the Paleo-Indian artifact assemblage. The Lake Manix artifacts are described in more detail on the next screen.
The controversial Calico Lithic Industry artifacts are present within a severely eroded deposit that appears to be the remnant of an ancient alluvial fan that was formerly connected to the Calico Mountains, north of Yermo. The fan remnant–the so-called Yermo Fan–consisting of round-crested ridges and narrow gullies, is now well separated from its original source by uplift and erosion that has completely destroyed the original fan form, exposing the material upon which the fan was deposited. The objects identified as artifacts have been recovered from the nested Pleistocene mud and debris flows composing the original fan. The fan deposits are cemented throughout by calcium carbonate older than the limit of radiocarbon dating (~40,000 yrs), beneath a surface soil having an estimated age of 100,000 years. The deposits have been dated to 135,000 years by thermoluminescence (TL) dating and to about 200,000 years by uranium-series analysis. It is the objects found in these deposits that are in question. Are they artifacts or geofacts? If they are artifacts, they appear to be close to twenty times the age of the oldest North American artifacts that have achieved general acceptance–the Clovis tool kit.