Meadowcroft Rockshelter (Adovasio, et al. 1977; Carlisle and Adovasio 1982) is one of the few sites in North America that has produce artifacts in levels predating Clovis. Pre-Clovis sites have to have artifacts dating older than 12,500 years ago. Hot links in this document will take you to photographs or tables related to the text.
Meadowcroft Rockshelter was excavated from 1973 until 1978 with additional excavations to repair slumps and check data in the 1990s. I was a field crew member who excavated the earliest levels at Meadowcroft during the 1974 season and personally collected many of the samples that produced the early dates. I also directed excavations at the Avella Mound in 1975 as part of the general Meadowcroft program.
The early radiocarbon dates from Meadowcroft have been criticized by Haynes (1980, 1991), Kelly (1987), Mead (1980), Tankersley, Munson and Smith (1987), Tankersley and Munson (1992) and others as being the result of various types of coal contamination or incongruities concerning floral and faunal associations. According to these people, either particulate coal or soluable humates and carbon ions from coal percolated through the clays in ground water at the shelter and were embedded in the charcoal collected and radiocarbon dated. This contamination supposedly resulted in the samples producing anomalous dates. These criticisms have also been addressed by Adovasio et al. (1980), Adovasio, Donahue and Stuckenrath (1990) and Adovasio, Donahue and Stuckenrath (1992). Generally, they disagree with the view that coal contamination of the samples resulted in dates that are too old or that the floral and faunal associations do not indicate a Pleistocene occupation at the site.
I personally do not believe any of the radiocarbon dates from the early levels at Meadowcroft are erroneous. I think they properly date the samples submitted and are not contaminated by coal. However, I am hardly an unbiased observer.
The earliest remains from Meadowcroft did not come from excavations within the drip-line of the rockshelter. Most came from an area excavated beside the Old Roof Fall (an immense rock that fell from the top of the shelter prior to anyone living at the site).
Two samples I recovered were dated to ca. 19,000 years ago. Unfortunately, the two 19,000 B.P. samples were not directly associated with stone tools. One of these was some carbonized bark (possibly birch bark) about the size of a half-dollar coin. Adovasio believed it was cut by stone tools and might be a piece of a bark basket. The bark sample was composed of two separate layers or "elements" suggesting to Adovasio that it was part of a plaited basket. However, I was not totally convinced the bark was from a basket. The two "elements" may represent the inner and outer bark that separated when the piece was burned. If the bark sample was not part of a basket, it might simply represent remains from an ancient forest fire that occurred at the site (the bark was not discovered in any hearth or hearth-like feature). It is for this reason that the bark was only tentatively identified as a basket fragment in Meadowcroft reports, and the dates questioned as being associated with a Paleoindian occupation.
Even if the bark sample is not a cultural item, it is an important sample in respect to the argument concerning coal contamination at Meadowcroft. The sample dated to 19,600 B.P. +/- 2400 years or 17,650 B.C. (SI-2060, uncorrected) and was recovered in an appropriate stratigraphic location relative to the other early dates from the shelter. If it was from a Paleoindian fire and was contaminated with coal, as some have suggested, how much coal would have to be added to the sample to make it date to 19,100 B.P.? Lets presume that the bark sample should have dated to ca. 11,000 B.P. (and the artifacts recovered from the lower levels at the least demonstrate a Paleoindian presence at the site, they were stratified below Early Archaic materials) and was contaminated by coal to produce 19,000 B.P. dates. Nearly 40% of the sample must have been composed of "dead" carbon to result in this date. Particulate coal contamination would have been readily noticeable to the Smithsonian Radiocarbon lab that dated this sample. First, the sample (as were other samples from Meadowcroft) were microscopically examined for coal contamination (note: local coal does not display any cellular structure and would be easily recognizable under a microscope when compared to wood or bark). Thus, particulate coal can be eliminated as a contaminate in this and all the samples from the site. Conversely, if water soluable humates had been the contaminant, they would have been removed by pretreatment and a corresponding reduction in the size of the sample should have been noted. It was not. Thus, it is extremely difficult to justify a claim that the bark sample was contaminated. Considering its location and stratigraphic integrity of the other samples, it also suggests they were not contaminated.
Most other charcoal samples taken and dated from the earliest levels, or the "Deep Hole" as it was named by the crew, consisted of pieces of charcoal found with ash and burned earth. These were interpreted as surface hearths that had been put out (i.e., kicked out, spreading some of the ash and charcoal around). Stone tools were found in association with these samples lending support to the interpretation of them being extinguished hearths. Tools included bifaces and biface fragments (including the so-called Mungai Knives), lamellar blades and chipping debris, some of which were made from exotic heat-treated Flint Ridge Chalcedony. Flint Ridge Chalcedony had to be brought to the site from quarries located between Newark and New Concord in Ohio. There is at least one very well-defined basin-shaped hearth that was reused over a period of time. It was composed of alternating layers of charcoal and burned earth. A lanceolate projectile point, named the Miller Lanceolate, was found near this hearth.
All Paleoindian remains from Meadowcroft were found in good stratigraphic contexts below levels containing Early Archaic projectile points. In fact, I recovered a Stanley Point sitting on its edge on top of the boulder that was eventually used to step down into the Deep Hole (a ladder was initially used to get down into the Deep Hole) from the interior of the shelter. Thus, even if the criticisms about charcoal contamination are accepted, there is an indisputable Paleoindian occupation at Meadowcroft.
An extended discussion about the Meadowcroft radiocarbon dates, the Clovis First hypothesis and the Pre-Clovis remains is available at:
Clovis First and Pre-Clovis Meadowcroft Discussion
I've also made a cartoon about the Clovis First Blitzkrieg or Overkill Hypothesis, and it can be seen at:
http://people.delphiforums.com/MCCONAUGHY/meadowcroft/blitzkrieg.htm
Adovasio, J. M., J. Donahue and R.Stuckenrath
1990 The Meadowcroft Rockshelter Radiocarbon Chronology 1975-1990.
American Antiquity 55:348-354.
1991 Never Say Never Again: Some Thoughts on Could Haves and
Might Have Beens. American Antiquity 57:327-331.
Adovasio, J. M., J. D. Gunn, J. Donahue and R. Stuckenrath
1977 Meadowcroft Rocksheler: Retrospective 1976. Pennsylvania
Archaeologist 47(2-3):1-93.
Adovasio, J. M., J. D. Gunn, J. Donahue, R. Stuckenrath, J. E. Guilday and K. Volman
1980 Yes Virginia, It Really is that Old: a Reply to Haynes and Mead.
American Antiquity 45:588-595.
Carlisle, R. C. and J. M. Adovasio, eds.
1982 Meadowcroft: Collected Papers on the Archaeology of Meadowcroft
Rockshelter and the Cross Creek Drainage. Department of Anthropology,
University of Pittsburgh, Pittsburgh.
Haynes, C. V.
1980 Paleoindian Charcoal from Meadowcroft Rockshelter: Is Contamination
a Problem? American Antiquity 45:582-587.
1992 More on Meadowcroft Rockshelter Radiocarbon Chronology. The
Review of Archaeology 12(1):8-14.
Kelly, R.L.
1987 A Comment on Pre-Clovis Deposits at Meadowcroft Rockshelter.
QuaternaryResearch 27:332-334.
Mead, J. I.
1980 Is It Really that Old? A Comment about the Meadowcroft Rockshelter
"Overview." American Antiquity 45:579-582.
Tankersley, K. B. and C. A. Munson
1993 Comments on the Meadowcroft Rockshelter Radiocarbon Chronology
and the Recognition of Coal Contaminants. American Antiquity 57:
321-326.
Tankersley, K. B., C. A. Munson and D. Smith
1987 Recognition of Bituminous Coal Contaminants in Radiocarbon Samples.
American Antiquity 52:318-330.