Presentation on theme: "Calico Mountains Archaeological Site Mojave Desert."— Presentation transcript:
Calico Mountains Archaeological Site Mojave Desert
Overview Region Brief History Site Type Problems Artifact Recognition Conclusions
Region Mojave Desert (Yermo, Ca) Climate was more temperate in region 10,000+ years ago. Ancient lake in region, water source for people and fauna. Arguments persist about why the lake drained or dried up, but this is a region of heavy geologic activity now and throughout the past. The mountains of the region feature Alluvial Fans.
Region - Maps
Ancient Lake in Region
Lake Manix Pleistocene Lake Manix in relation to the Calico Archaeological Site. The lake disappeared rapidly about 18,000 years ago, presumably by overflow that created Afton Canyon, south of Cave Mountain, at the eastern end of the lake.(calico website)
Alluvial Fan The Calico Mountains feature Alluvial Fans – cone shape flows from a single apex. Calico Site – the pits are within an Alluvial fan meaning that no distinctive stratigraphy exists. This makes dating difficult.
Brief History Has been a controversial archaeological site. The site, in low hills east of the Calico Mountains, displays evidence for the presence of tool-making humans in the Americas some 200,000* years ago, far earlier than any Western Hemisphere site that has been accepted by the majority of the archaeological community. The Calico site has been developed since 1964 by Ruth DeEtte Simpson with the active involvement of Louis B. Leakey, famed for his work on the African Paleolithic at Olduvai Gorge in Tanzania.
Dating of Fauna and Types Evidence of the history of Lake Manix remains in the clay, silt, sand, and gravel sequences of the Manix Formation, which contains remains of numerous Rancholabrean animals ranging in age from approximately 20,000 years to well in excess of 350,000 years before present (Jefferson 1968, 1985a, 1985b, 1987, 1989, 1991). The richest fossiliferous section has been well dated by radiocarbon dating, uranium-series techniques, and trace element correlation of a volcanic tephra to a source well dated by the potassium-argon (K/Ar) method. Among the fossils recovered are camel, horse, mammoth, ground sloth, saber-tooth cat, dire wolf, short-faced bear, coyote, flamingo, pelican, eagle, swan, geese, mallard duck, ruddy duck, canvas- backed duck, double-crested cormorant, grebe, crane, seagull and stork. This fauna would have been a bountiful resource for any humans in the vicinity of the lake.
Artifact Assemblages 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.
Lake Manix Lithic Industry 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. 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 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.
Cont Surface sites of the Lake Manix Lithic Industry have been recorded in the northern half of the Manix Basin (Simpson 1960, 1976; Alsoszatai-Petheo 1975, Binning et al. 1985). They are devoid of pottery, shell objects, and projectile points. Lithic artifacts, fashioned primarily of chalcedony, chert, and jasper, include large oval bifaces, scrapers of several forms (end, straight, concave, pointed, convex, pointed, and plano-convex), cutting tools, choppers, chopping tools, large stout picks, gravers, cutting tools, rotational tools, and flakes, as well as cores, anvils and hammerstones.
Site Type, Dating, and Types Based on a dated pollen profile at site CA-SBR-2120 and the occurrence of this assemblage above the most recent shoreline elevation of Pleistocene Lake Manix (543 m), the Lake Manix Lithic Industry is inferred to be at least 18,000 years old. The presumed eastern extension of the Yermo Fan, known as The East Rim Site (CA-SBR-2120), is a lithic workshop with bifacial and unifacial artifacts as well as debitage on and beneath a desert pavement surface to a depth of 15 cm (Alsoszatai-Petheo 1975). Recovered pinyon and juniper pollen suggests occupation 17,000 – 34,000 years ago. Unifacial artifacts include choppers and end, side, and convex-edged side scrapers. Bifacial artifacts include chopping tools, generalized bifaces, wedge-shaped bifaces, ovate bifaces, cutting tools, and utilized flakes. Unflaked artifacts include hammerstones, pecking stones, and pointed tools. Rare specimens include multiple scrapers, tortoise scrapers, gravers, pointed scrapers (borers), and keeled scrapers.
Identifying Artifacts Percussion Bulb Flake Scars Rock Types
Thermoluminescence Dating Thermoluminescence (TL) dating is the determined by measuring the accumulated radiation dose of the time elapsed since material containing crystalline minerals was either heated (lava, ceramics) or exposed to sunlight (sediments). As the material is heated, during measurements, thermoluminescence, a weak light signal, is emitted proportional to the radiation dose absorbed by the material. Used When C-14 not available – time issues, requires organics.
Conclusions The site is less controversial today after East Coast sites have been found to be older than Clovis. Also, many sites in central and South America have been found with better dating to be older. Its a good place to learn excavation. Leakey claims are false. People likely came to the Americas over 20,000 years ago, at least (I tend to think 40,000 year plus theory.)