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Radiocarbon Dates and Early Man

Published online by Cambridge University Press:  27 June 2018

Frank H. H. Roberts Jr.
Frank H. H. Roberts Jr.*
Affiliation:
Bureau American Ethnology, Smithsonian Institution, Washington, D.C.
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Extract

The results of carbon 14 tests on materials falling within the early man category are in some respects as surprising as a few of those in other fields, but on the whole they are reasonably satisfactory. Because of the regional distribution of the samples and the number of people who sent them in, several nominally belonging in this group are discussed elsewhere. The latter include Gypsum cave, Leonard rockshelter, the early horizons in California and Oregon and the material from South America.

The age of the well-known Folsom complex caused considerable comment when the figure pertaining to the type site was released. The average of 4283 ± 250 years obtained from sample 377 was entirely too low in the opinion of many archaeologists and geologists and was completely out of line with dates for other materials known to be later stratigraphically. Because of this, Harold J. Cook, who provided the charcoal used in the test, returned to and carefully reexamined the Folsom quarry in 1950.

Type
Research Article
Information
Memoirs of the Society for American Archaeology , Volume 8: Radiocarbon Dating: A Report on the Program to Aid in the Development of the Method of Dating , 1951 , pp. 20 - 22
Copyright
Copyright © Society for American Archaeology 1951

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References

* This and other numbers constantly used or cited in these reports refer, of course, to samples as listed by number in table 1.

** Editor's Note: At about the same time the manuscript for this radiocarbon dating report reached me, I received a communication from Harold J. Cook, Agate, Nebraska, regarding the Folsom problem. It is here reproduced as a footnote.

“A widespread misunderstanding appears to have occurred, with related misinterpretation of the facts involved, since the publication of ‘Radiocarbon Dates,’ September 1, 1950 by Arnold and Libby. Since this has happened as a result of my condensing information too much on the occurrence of this charcoal which I collected, it seems important that this misunderstanding be corrected before the implications of it become more deeply rooted.

“In June, 1950, I revisited the Folsom site (where I had charge of the original excavations), for the purpose of reexamining the site. Here a condition I had suspected was clearly seen; namely, that the fire pit from which the dated charcoal came, while old, was definitely much younger than the deposit from which the original Folsom Bison and artifacts were recovered. Erosion of the past eighteen years has better exposed these beds and makes clear the following relations:

“The bones and artifacts of the original Folsom discovery were found in a light yellowish-tan, rather adobelike matrix, horizontally and rather uniformly bedded. A few yards downstream, i.e. east, from this deposit where the arroyo, deeply incised, now runs, a narrow valley had been cut through that original deposit at some later date at a sharp angle from the northwest. Still later this valley had again completely refilled to the level of the present valley floor. The matrix in this valley-fill is much darker and readily distinguished at a glance from the matrix in which the Folsom bones and artifacts occurred. This later valley cut as deep or deeper than the current arroyo bottom which is several feet lower than the level where the bones and artifacts were found.

“While erosion had removed all traces of the ‘fire-pit’ from which I collected that charcoal in 1933, I could locate the spot rather closely. It was obviously well inside the limits of this refilled, but secondary, valley. Probably a fire was made on its side or floor during the time it was being refilled. Whether it was a camp fire or not is uncertain but in size and shape the charcoal lens looked like one. So, the radiocarbon dating of 4283 ± 250 years on this charcoal merely confirms the physical data we had observed; namely, that the secondary valley is much younger than the Folsom Bison and artifacts, which were collected some hundred feet, plus or minus, to the westward.”

* Since the above was written it has been learned that the charcoal giving the 10493 ± 1500 years came from below, the occupation zone, hence the cultural material from the lowest level must be regarded as an undetermined number of years younger.