R. E. Taylor

Clovis and Folsom age estimates: stratigraphic context and radiocarbon calibration

The events to do with peopling the New World archaeologically represented by ‘Clovis’ and ‘Folsom’ have been — tantalizingly — beyond the range of radiocarbon calibration. Now calibration extends further, one can ask if the aburptness of Clovis, of Folsom, and of the transition between them are realities. A calibrated chronology for those sites where the stratigraphic security is best shows these in truth are rapid human affairs.

Chronometric dating in archaeology

Climatostratigraphy M.J. Aitken, S. Stokes. Dendrochronology J.S. Dean. Radiocarbon Dating R.E. Taylor. Potassium-Argon/Argon-Dating R. Walter. Fission Track Dating J. Westgate, et al. Uranium-Series Dating H.P. Schwarcz. Luminescence Dating M.J. Aitken. Electron Spin Resonance Dating R. Grun. Protein and Amino Acid Diagenesis Dating P.E. Hare, et al. Obsidian Hydration Dating I. Friedman, et al. Archaeomagnetic Dating R.S. Sternberg. Surface Dating Using Cation Ratios J.S. Schneider, P.R. Bierman. Index.

The use of radiocarbon (14C) to identify human skeletal materials of forensic science interest.

The radiocarbon (14C) method is a well-known isotopic dating technique by which age can be assigned to organic materials, including human bone. Natural and anthropogenic anomalies in 14C activity in the biosphere over the last few centuries, including the presence of artificial or “bomb” 14C after 1950, can be used as an isotopic tracer to assign human bone samples with high degrees of probability to one of three temporal periods within the recent past: a Non-modern period (before about A.D. 1650) of no forensic science interest, a Pre-modern period (A.D. 1650 to 1950) of possible or potential forensic science interest, and a Modern period (A.D. 1950 to the present) of definite forensic science interest. We illustrate the use of the 14C method to assign human bone in five forensic science cases to one of these time periods.

Development and extension of the calibration of the radiocarbon time scale: Archaeological applications

The purpose of the 14C calibration process is to convert a conventional 14C age into solar time and express the resultant transformation in a manner which accurately reflects the overall precision of the age expression. Comparisons of 14C and dendrochronological data provides a detailed calibration record for the Holocene. The results of paired uranium/thorium and 14C measurements have been used to examine the 14C/solar time offset during the terminal Pleistocene. This potential extended calibration data base permits researchers to view within a larger perspective the Holocene 14C time spectrum as well as the characteristics of the various Holocene 14C ‘time warps’. As an example of the potential effect of the extended calibration data based on the initial coral data, we compare calibrated 14C age determinations associated with the Clovis and Folsom fluted point tradition in North America prehistory.

Middle Holocene Age of the Sunnyvale Human Skeleton

A morphologically modern human skeleton from Sunnyvale, California, previously dated by aspartic acid racemization to be approximately 70,000 years old and by uranium series isotopic ratios to be 8300 and 9000 years old, appears to be younger when dated by the carbon-14 method. Four carbon-14 determinations made by both decay and direct counting on three organic fractions of postcranial bone support a middle Holocene age assignment for the skeleton, probably in the range of 3500 to 5000 carbon-14 years before the present. This dating evidence is consistent with the geologic, archeological, and anthropometric relationships of the burial as well as previously determined carbon-14 determinations on associated materials.

Radiocarbon dating organic residues at the microgram level

Relation between submilligram sample size and {sup 14}C activity for sample blanks (wood from Pliocene sediments) and a contemporary standard (oxalic acid) for catalytically reduced graphitic carbon was examined down to 20 micrograms. Mean age of the 1 mg wood sample blanks is now about 51.3 ka (0.168 pMC) while the mean for 20 microgram sample blanks is about 42.9 ka. So far, the lowest value for a 1-mg wood sample blank is about 60.5 ka (0.056 pMC). We have determined a mean {sup 14}C age of about 9.4 ka from a suite of 7 organic extracts from hair, bone, and matting from a mummified human skeleton from Spirit Cave, Nevada. These data indicate that the Spirit Cave human is the third, oldest directly-dated, human skeleton currently known from North America.

The contribution of radiocarbon dating to New World archaeology

When introduced almost five decades ago, radiocarbon ( (super 14) C) dating provided New World archaeologists with a common chronometric scale that transcended the countless site-specific and regional schemes that had been developed by four generations of field researchers employing a wide array of criteria for distinguishing relative chronological phases. A topic of long standing interest in New World studies where (super 14) C values have played an especially critical role is the temporal framework for the initial peopling of the New World. Other important issues where (super 14) C results have been of particular importance include the origins and development of New World agriculture and the determination of the relationship between the western and Mayan calendars. It has been suggested that the great success of (super 14) C was an important factor in redirecting the focus of American archaeological scholarship in the 1960s from chronology building to theory building, led to a noticeable improvement in US archaeological field methods, and provided a major catalyst that moved American archaeologists increasingly to direct attention to analytical and statistical approaches in the manipulation and evaluation of archaeological data.

Studies towards a method for radiocalcium dating of bones.

The authors made preliminary AMS measurements of [sup 41]Ca/Ca ratios in bone and limestone specimens with the Argonne Tandem-Linac Accelerator System (ATLAS). They were able to avoid pre-enrichment of [sup 41]Ca used in previous experiments due to a substantial increase in Ca-beam intensity. Most of the measured ratios lie in the 10[sup [minus]14] range, with a few values below 10[sup [minus]14]. In general, these values are higher than the ones observed by the AMS group at the University of Pennsylvania. They discuss possible implications of these results. They also present the current status of half-life measurements of [sup 41]Ca and discuss [sup 41]Ca production processes on earth.

Radiocarbon Dating of Bone Osteocalcin: Isolating and Characterizing a Non-Collagen Protein

Osteocalcin, a non-collagen bone-matrix protein, has been examined as a possible source of autochthonous 14C data in fossil bones where collagen has been seriously degraded. Extraction procedures for osteocalcin yield a wellcharacterized product that can be clearly distinguished from collagen. The Gla content indicates that osteocalcin is present in the fossil bones at levels similar to the range present in modern bone. However, it appears to be extracted primarily as proteolytic polypeptide fragments rather than as an intact protein. Concordant 14C determinations are obtained on osteocalcin and gelatin extracts from the same bone when the collagen is relatively well preserved. However, increasing discordances in the 14C values of the osteocalcin and gelatin fractions are associated with reduced concentrations of the gelatin extract in the bone.

Impact of AMS 14C determinations on considerations of the antiquity of Homo sapiens in the western hemisphere

Abstract The ability of AMS facilities to obtain direct 14C determinations on milligram amounts of organic extracts of bone has significantly advanced efforts to reexamine the validity of the dating evidence for a number of allegedly Pleistocene Homo sapiens skeletons from the Western Hemisphere previously assigned ages of from about 20000 to 70000 years. AMS 14C analysis has indicated that four of these skeletons are actually of Holocene age, i.e., less than 10000 years old. Holocene ages have previously been documented on the basis of conventional 14C analysis for six other purported Pleistocene human skeletons from the New World. These data point to the danger of accepting pre-Holocene age assignments for such skeletal materials in the absence of direct 14C evidence.