Sunday, 20 December 2015

Monte Verde update - Conversion of Radiocarbon dates to calendar years suggest Monte Verde MV-I close to 40000BP


As mentioned in a previous post (see here) I have been scouring the internet for information on any further excavations of the MV-I portion of the Monte Verde site. Whilst I did not find any references to MV-I having been further excavated to confirm the 33000BP radiocarbon dates from his 1997 report1 I did come across an extremely interesting piece by Ruth Gruhn in the Mammoth Trumpet, from 2007.
 
Among other things, the piece had some pictures of the lowest levels excavated at MV-I and the actual artifacts.


Photo Credit Tom Dillehay
Original caption: Ash smear and charcoal fragments exposed on the Monte Verde I occupation level, with a lithic artifact associated. Charcoal from this occupation level was dated ca. 34,000 RCYBP.

 

Photo Credit Tom Dillehay
Original caption: A basalt core tool, 9.4 cm long, from the Monte Verde I occupation level.


 
Photo Credit Tom Dillehay
Original caption: Two hammerstones from the Monte Verde I occupation level, showing marks of use as battering tools. Each is about 13 cm in diameter.


The section of the article relating to Monte Verde read thus:

 

“The Monte Verde project involved detailed geological research in the area. Accordingly, geological test pits were excavated on a terrace of Chinchihuapi Creek ca. 20–30 m across the creek from the Monte Verde II settlement; and in a different stratum (basal MV-7), at a depth of ca. 1.5 m below the level of the Monte Verde II occupation, lithic artifacts turned up. Excavation in this area was expanded. In all, 26 lithic artifacts were recovered from a restricted zone in the compact grey sand deposit, including a basalt core tool, two hammerstones with battering marks, three percussion-struck flakes, and six utilized fractured pebbles. The basalt core tool features 10 prominent flake scars on the face, and small use-wear flakes have been detached from one acute edge. Blood residue identified as possibly proboscidean was detected on the piece.
The lithic artifacts were recovered in direct association with three small shallow clay-lined lenses with ash streaks and charcoal fragments, possibly remains of hearths.
Dates of 33,750 ± 520 RCYBP and >33,020 RCYBP from samples of burnt and charred beech wood correspond with previously published radiocarbon dates on the particular geological stratum (basal MV-7) in which the artifacts and features were found. Geomorphological reconstruction indicates that the Monte Verde I artifacts and features were situated on a promontory overlooking an ancient marsh or pond. Charred seeds of the reed Juncus sp., a wetlands plant with edible stalks and seeds, were recovered in the hearth-like features. Usually, severe critiques follow reports of really early archaeological sites; but few questions have been raised about the quality of the Monte Verde I evidence. Dillehay himself believes that some of the recovered evidence is valid, but by itself it is insufficient at the present time to establish conclusively a human occupation of the Americas this early.”


The most interesting part however was the dates ascribed to the charcoal fragments they were in Radiocarbon Years! So they convert to OLDER dates!

I therefore used the Columbia University Radiocarbon age to calendar age conversion curve3 to look at the ACTUAL date in calendar years. I adapted their graph and added lines and grids to show the Dillehay 1997 Radiocarbon age of 33750RCY.

Monte Verde MV-I Radiocarbon years before present (RCYBP) to Calendar Years Conversion. N Barden.
 

The age of the site turns out to be a stunning 39000BP or 39500BP if the upper limit of the error is added. STUNNING!

 References
 
1. Dillehay TD. Monte Verde: A Late Pleistocene Settlement in Chile. Volume II: The Archaeological Context. Washington, D.C.: Smithsonian Institution Press; 1997.
 
2. Gruhn R. The Earliest Reported Archaeological Sites in South America. The Mammoth Trumpet, Volume 22, Number 1. January, 2007 Center for the Study of the First Americans, Department of Anthropology, Texas A&M University
 
3. Chiu, T-C, R. G. Fairbanks, Li Cao, Richard A. Mortlock, 2007. Analysis of the atmospheric 14C record spanning the past 50,000 years derived from high-precision 230Th/234U/238U and 231Pa/235U and 14C dates on fossil corals. Quaternary Science Reviews, 26, 18-36


Update 29/12/15
 
Where these dates originate: Dillehay, states1 “The two ages for stratum MV-7 (33370 +/-530 B.P., Beta-6754 and greater than 33020 B.P., Beta-7825) were excavated on the unconforming plain of SCH-4 (the base of MV-7). The two samples were collected from two different, but spatially contiguous, charcoal scatters in direct association with modified stones at a depth of 2.0m below the present surface at the Monte Verde site and 8m below the top of the intact Salto Chico Formation elsewhere in the area. The age of this stratum thus represents a geologic, or possibly a cultural, event (Dillehay 1986:3362)..”
 
I will obtain the 2nd reference and report further.
 
1. Dillehay, T.D. Early Rainforest Archaeology in Southwestern South America: Research Context, Design, and Data at Monte Verde. In: Wet Site Archaeology Purdy, Barbara A. 1990 Wet Site Archaeology CRC Press
 
2. Dillehay, T. 1986 The Cultural Relationships of Monte Verde: A Late Pleistocene Settlement Site in the Sub-Antarctic Forest of South-Central Chile. In New Evidence for the Pleistocene Peopling of the Americas. Edited by A.L. Bryan Center for the Study of Early Man. University of Maine, Orono. p319-337.



No comments:

Post a Comment