Taylor Haynes Stuiver ClovisandFolsomageestimates

Clovis and Folsom age estimates: stratigraphic context and radiocarbon

calibration

R.E. TAYLOR, C. VANCE HAYNES, JR & MINZE STUIVER”

The events to do with peopling the New World archaeologically represented b y ‘Clovis’ and ‘Folsom’ have been - tantalizingly - beyond the range of radiocarbon calibration. Now calibration extends further, one can ask i f the abruptness 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.

Introduction In the late 192os, the discovery of several fluted projectile points associated with skeletons of an extinct species of bison convinced the archaeological profession that human populations had entered the New World sometime between 10,000 and 25,000 years ago (Wormington 1957). This age was at least twice that previously accepted by the professional community. These fluted projectile points - given the name Folsom points after the nearest New Mexico town - had not previously been known (Meltzer 1989).

In 1932-33, larger and more robust fluted points were found in situ at the Dent site in Colorado. Their association with the skeletons of a dozen mammoths led to the idea that these Folsom-like points (they were not as yet called Clovis) were used to kill mammoths, while the more delicate Folsom points were used to kill smaller game, like bison (Wormington 1957). In 1936 and 1937, near Clovis, New Mexico, a robust fluted point was found again with mammoth bones. However, these materials were in sediments stratigraphically below a deposit containing Folsom points associated with bison skeletons. This resulted in the robust form being recognized as older than Folsom and being named Clovis points.

For over half a century, the stratigraphic separation of Clovis and Folsom has persisted, while nearly a dozen stratified Clovis sites and several dozen stratified Folsom sites have been scientifically excavated. Since the early 1950s, 14C age determinations have been obtained on a variety of materials associated with, or pur- ported to be associated with, Clovis and Folsom materials. In addition, using primarily dendrochronologically dated wood to provide known age controls, systematic anomalies in the 14C time scale over the Holocene were documented. Unfortunately, Clovis I4C and most of the Folsom 14C values lay beyond the reach of the dendrochronologically based calibration database. However, from time to time, questions were posed as to the possible effect of calibration on the Clovis and Folsom 14C Val- ues if the calibration database was ever extended (e.g. Haynes 1971; Taylor 1987; 1991; Meltzer 1995; Batt & Pollard 1996). With the availabil- ity of paired uranium/thorium (234U/230Th) and I4C samples from cores drilled into coral for- mations, a pre-dendrochronological calibration 14C data base has now been developed (Bard et al. 1993a; 1993b; Edwards et al. 1993).

The purpose of this discussion is to consider the corpus of I4C values in light of the stratigraphic contexts of Clovis and Folsom and the

* R.E. Taylor, Radiocarbon Laboratory, Department of Anthropology, Institute of Geophysics and Planetary Physics, University of California, Riverside, Riverside CA 92521, USA. C. Vance Haynes, Jr, Departments of Anthropology and Geosciences, University of Arizona, Tucson AZ 85721, USA. Minze Stuiver, Quaternary Research Center, Department of Geological Sciences, University of Washington, Seattle WA 98195, USA.

Received 22 March 1996, accepted 22 May 1996

ANTIQUITY 70 (1996): 515-25

516

FLUVIAL MODE

HISTORIC GULLYING

EPICYCLES OF

FILLING CUTTING AND

R.E. TAYLOR, C. VANCE HAYNES, JR & MINZE STUIVER

4 z 2 2

z a:

0 2

n

UNCALIBRATED RADIOCARBON AG (YEARS b.p.)

6 2 w

7000-8000

ALLUVIA1 UNIT

11,000

12,000-13,000

16,000

I

z2.

Z1' 1 1

AGGRADATION

/ TRANSITION FROM '

\ TO AGGRADATION DEGRADATION

~

A0ANDONMENT OF

COINCIDENT WITH DEGLACIATION

(NET DEGRADATION)

PLEISTOCENE TERRACE

physiochemical characteristics of the sample materials, to address issues associated with the extension of the 14C time frame for which calibration data has been made available using uranium-seriesP4C paired values, and to address what can and cannot now be confidently as- serted concerning the chronological overlap between Clovis and Folsom.

Stratigraphic contexts This discussion of Clovis/Folsom 14C data is based on the premise that the stratigraphy of most of the sites considered here can be correlated to the generalized sequence summarized in FIGURE 1 (Haynes 1984; n.d.), a view based upon the consistent stratigraphic position of fauna, flora, and archaeology from site to site (Haynes 1971; 1991; n.d.).

In FIGURE 1, alluvial unit c1 represents Pleisto- cene streams with discharges several times greater than modern streams. LJnit 13, represents terminal Pleistocene channel sedimentation following a pronounced interval of degradation represented by unconformity Z,. Along this much reduced channel, elements of Rancho- labrean fauna spent their final days as Clovis

CULTU RE5

CERAMIC / * e

/ c /

ARCHAIC - / - -

/ *

PALEO- INDIAN

CLOVIS

PRE- CLOVIS

(?)

FIGURE 1. Correlation chart cf some late Pleistocene-Holocene alluviol events in North .4merica. M0difi.d from Hayne:; f1984).

hunters pursued them some 11,000 radiocarbon years ago. Clovis Palaeoindians first appear in upper p,. The depositional contact Z,, between p, and p2, marks essentidly the end of Pleistocene extinction. Away from the p, channel Z, and Z, join to form a single erosional contact, Zl-z. Unit p2, the first significant post-pleistocene aggradation, is silty sand or fine sandy silt commonly lacking coarser c:hannel facies and is probably slope-washed eolian sand or loess. Subsequent alluvial units (y, 6, E) are de- rived from slope wash and reworking of earlier alluvial units. Radiocarbon ages of erosional in- tervals indicate the range of time during which degradation occurred. The transition from Rancho- labrean fauna to the modern fauna is represented by extinct forms of bison in unit p, as the last vestige of the Pleistocene megafauna.

Each of the 14C-dated archaeological levels being considered (TABLE 1) has come from a stratified sedimentary context which can be correlated at all but 3 of the sites (Anzick, Dent and Hanson) on the basis of an erosional contact (Z,J believed to have widespread geographic distribution and to be, in part, drought-induced (Haynes 1991). FIGURE 2 provides the location

CLOVIS AND FOLSOM AGE ESTIMATES: STRATIGRAPHIC CONTEXT AND RADIOCARBON CALIBRATION 517

Clovis sites 14C age b.p. Folsom sites I4C age b.p.

Murray Springs (8) Lehner (12) Anzick" Dentb UP Mammoth" Lange/Fergusond Colby" Domebo' Blackwater Draw (3)g Aubrey (2)l'

10,890f50 10,940+40 10,940f90 10,980k90 11,280*350 11,140k140 11,200*2 20 11,480+450 11,300+240 11,570f70

Hanson (4) Blackwater Draw (5)i Carter/Kerr McGeei LubbockLake Indian Creek/lk Owl Cave Lindenmeier (3) Agate Basin (2)' Folsom (6) Indian CreekW

10,250+90 10,290*90 10,400+600 10,540f100 10,630+280 10,640k85 10,660*60 10,700?70 10,890+50 10,980f150

Notes a Bone (glycine fraction). b c d Good association. e Bone (collagen fraction). f SM-695 and AA-823 (Elm wood] not used because of questionable association. g Clovis type site; Carbonized plant remains (corrected values): 11,630k400 (A-491), 11,170+360 (A-481) and 11,040f500

h Average of 11,540+110 (AA-5271) and 11,590+90 (AA-5274). i Good association, one of the samples used is bone (collagen fraction) and the remainder are carbonized plant remains. j Good association. k 1

TABLE 1. Selected radiocarbon dates associated with Clovis and Folsom sites. See text for explanation of basis of selection. Notes contain additional detail, explanation and commentary. When value cited in the table is an average, the number of 'T values averaged are listed in paraenthesis. The method of averaging i s taken from Long b Rippeteau (1 974).

Only bone XAD hydrolysate fraction used: other bone amino acid values are assumed to be too young. Tusk organics. Artefacts not diagnostic but probably Clovis.

(A-4901.

Indian Creek charcoal samples are from two locations several metres apart. Average of SI-3733 and SI-3732; 1-472 not used because of questionable association.

of the sites in TABLE 1. In the alluvial sites such as Murray Springs, Lehner, U p Mammoth, Colby and Domebo, Clovis artefacts occur in situ on the Zl-2 erosional surface as well as within the de- posits of small channels equivalent to unit p, of the generalized sequence. In the spring-deposited sites, the Clovis type site at Blackwater Draw, New Mexico, Lange/Ferguson in South Dakota and Aubrey, Texas, Clovis artefacts occur again on the Zl-2 surface as well as within springlaid sands at Clovis and LangeIFerguson that are tem- porally equivalent to unit p,. At the Aubrey site, Clovis artefacts occur on the surface of a Pleisto- cene colluvium and under pond sediments equivalent to unit p,. The contact is an extension of Z,-, from the camp area, which is on a buried alluvial terrace, to the pond area where the contact is deflational (Humphrey & Ferring 1994).

Folsom artefacts, when found in s i tu , occur in the lower 10-20 cm of an alluvial unit (pz) overlying the Z,-, contact at Blackwater Draw, Folsom, Lindenmeier, Agate Basin, Hell Gap, Carter/Kerr McGee, Hanson, and Indian Creek.

At Owl Cave (Miller 1982), Folsom artefacts occur within a dark organic-rich fine sand ( p ~ ) , washed in and disconformably overlying a yel- low clayey sand of late Pleistocene age, correlated here with unit a of the generalized sequence.

Fine-grained units equivalent to pz occur at seven of the Clovis sites as well, but only at the Blackwater Draw (BWD) Clovis type-site and the Carter/Kerr McGee site do Folsom artefacts occur in situ stratigraphically above the Clovis artefacts. At BWD, they occur in a diatomite equivalent to unit p2 that covers the top surfaces of mammoth bones associated with Clovis points and other Clovis artefacts in a gray sand equivalent to unit 01. Folsom artefacts, associated with bison skeletons, occur in the diatomite as high as 20 cm above the diatomite basal contact while Clovis artefacts are concentrated in the 10-15 cm below it. We should note that a pre-Clovis habitation of North America south of the Wisconsin ice border by human populations has not been conclusively demonstrated.

518 R.E. TAYLOR, C. VANCE HAYNES, JR & MINZE STUIVER

I

No Folsom occupation level has ever been found below the Zl-z contact, and no Clovis level has ever been found in unit fi, above it. Fur- thermore, the only mammoth bones found in situ above the Zz contact were at Owl Cave where they may have been deposited on Z2 before Folsom people entered the cave. (If these are contemporaneous with the Folsoni occupation, they represent, stratigraphically, the youngest mammoth remains known in North America.) Based on stratigraphic analysis, i t appears that the time difference between the latest Clovis site and earliest Folsom site is real though small.

Radiocarbon calibration Combined high-precision 14C/dendrochronological data sets based on Irish and German oaks, Douglas fir, sequoia and bristlecone pine currently document about 9800 years of dendrochronological time with 20-year (bidecadal) time-ring segments (Stuiver & Pearson 1993; Pearson & Stuiver 1993; Pearson et a]. 1993; Pearson & Qua 1993). The high-precision dendrochronologically based calibration record

FIGURE 2. Location of sites listed in TABLE 1 (Friso r7 1991 : 40; I? Wilke, pers. comm.). 1 Aglite Basin 2 Anzick 3 Aubrey 4 Bl~ckwater Draw 5 CarterKerr McGee 6 Coilby 7 Dent 8 Domebo 9 Folsom 10 Hanson 11 Indian Creek 1 2 Lange/Ferguson 13 Lehner 1 4 Lindenmeier 15 Lulibock Lake 16 Murray Springs 17 Owl Cave 18 UP Mammoth

has been provisionally extended to 11,390 BP by a proposed interlinking of the German oak and pine dendrochronological sequence (Kromer & Becker 1993; Becker 1993). This component of the calibration data-base is provisional because it currently 11996) includes a ‘floating’ tree-ring segment; future revisiclns in the overlap correlations are possible. Thus, for the period from 9840 to 11,440 BP (in radiocarbon time back to about 10,050 b.p.) calibrated values are not, as yet, absolutely fixed in time. For the late Pleistocene period before 10,050 b.p., paired coral uranium/thorium (U/Th) and 14C samples provide data on which a late Pleisto- cene 14C calibration curve has been extended to 21,950 BP (18,400 b.p. in I4C time) in 50-year increments (Bard et al. 1993a; 1!393b; Edwards e ta] . 1993).

values have evolved in response both ‘to the changes in the character of the data-base and, recently, to widespread access to the necessary mathemati- cal computational capabilities using micro-com- puters. Widely distributed computationally

The procedures used to calibrate

CLOVIS AND FOLSOM AGE ESTIMATES: STRATIGRAPHIC CONTEXT AND RADIOCARBON CALIBRATlON 519

calibrated (calendar) age BP T %

Q 5000 t l I 1 1 I I I I I I I I I I I I I I I I I I I I I I I I I I 1 . j

e 30,000 25,000 20,000 15,000 10,000 5000 0

4500

4000

3500

3000

2500

2000

1500

1000

500

O L 5 - -500

aJ u

Lf - - 1 1 1 1 " 1 1 ' 1 1 1 1 ' 1 1 1 ' ' 1 1 1

30,000 25,000 20,000 15,000 10,000 5000 [OI 4 5 Q)

M a calibrated (calendar) age BC/AD FIGURE 3. Atmospheric record: 0 to 30,000 years b.p. Design of figure adapted from Stuiver S Braziunas (1993:figure 1). See also Stuiver S Reimer (1993a:figure 2).

based calibration programs include CAL15 (Cen- tre for Isotope Research, University of Groningen, Netherlands: van der Plicht 1993), OxCal (Ox- ford Radiocarbon Accelerator Unit, Oxford Uni- versity: Ramsey 1995), and CALIB (Quaternary Research Center, University of Washington, Seattle: Stuiver & Reimer 1993a; 1993b). In this discussion, we use the most recent version and data- base of CALIB (3.0.3) to extend the calibration time-scale as applied to the corpus of Clovis and Folsom I4C determinations.

With the extension of the I4C calibration framework using the U/Th and 14C data on corals, the original 'sine-wave' characterization of the middle and late Holocene 14C calibration curve appears to have been an artefact of the limited time frame documented by the tree ring/

I4C data. As we see it now, a generalized representation of the long-term secular variation I4C anomaly over about the last 30,000 years seems characterized by a slow-decay function on which has been superimposed middle- and short-term perturbations. FIGURE 3 is a representation of that atmospheric I4C record. The data from 0 to 11,390 BP is based on dendrochronologically- dated tree-ring 14C measurements (Stuiver & Pearson 1993; Pearson & Stuiver 1993; Stuiver & Becker 1993; Pearson et al. 1993 and Kromer & Becker 1993). The solid-line curve in excess of 11,390 BP is taken from splined U/Th and I4C dates (triangles) on coral assuming a 400- year marine/atmosphere reservoir age (R) offset (Bard et al. 1993a; 1993b). We will consider below the accuracy and precision of the assumed


calibrated (calendar) age BP

13,950 12,950 11,950 10,950 9950 1 " " , " ' " " " , , " " " "

12,000 11,000 10,000 9000 8000

calibrated (calendar) age BC


FIGURE 4. Detail of atmospheric record: 9000 to 12,000 b.p. Tree-ring data the same as in FIGURE 2. See text for the basis of the data before 11,390 BP.

FIGURE 5. Summed probabilitv distri-

12,050 11.050 10.050 9050 8050 butions f o i the Clovis

(dashed) values taken from lict of values Iisted in Haynes 1992: table

are the sum of the

0 D25 [solid) rind Folsom

0 R20 24.1. Tkie distributions x .I I .I probability distribu- n tions cdibrated for

Y

OR15 each sample renormal- ized to total area equals unity with the program CALJB 3.0.3, Method B (Stuiver b Reimer 1993). Insets show cal. age ranges marked by vertical solid lines for probability levels which contain 68.3% [lo, dash-dclt line) and 95.4% (20, dotted line) of the area under the probability curves for the two datasets.

K Q) > 0 3 OD10

pf I

0 DO5

10,000 0 ROO

14,000 13,000 12,000 11,000

calibrated (calendar) age BP reservoir offset value. The dotted-line curve for the period before 23,000 BP is based on an assumed atmospheric equilibrium or steady-state value of 500% AI4C or 50% above the contem- porary standard at 30,000 BC.

FIGURE 4 focuses attention on the relationship between I4C and dendrochronological or U/Th data for the period from about 9000 to 12,000 b.p. (about 9950 to 13,950 BP), the time interval with which we are particularly con-

CLOVIS AND FOLSOM AGE ESTIMATES: STRATIGRAPHIC CONTEXT AND RADIOCARBON CALIBRATION 5 2 1

FIGURES 6a & 6b. Calibration of 14C values taken from TABLE 1 from Clovis (FIGURE 6a) and Folsom (FIGURE 6b) sites. Calibrated *4C values expressed at _+I o level (dark bands), _+20 level (light bands) with outer

m

m m

m m

Murray Spr ings

Lehner

Anzick

Dent

UP Mammoth

Lange/Ferguson

Colby

Oomebo

Blackwater Draw

Aubrey

13,000 4 12,000 11,000 10,000 9000 8000


Hanson

Blackwater Draw

C a r t e r / K e r r McGee

LubbockLake

I n d i a n C r e e k / l

O w l Cave

Lindenmeier

Agate Basin

Folsom

I n d i a n C r e e k / 2

neirner I YYXIJ, L ~ L I L )

3.0.3, Method A .

cerned. Data before 11,390 BP are based on U/ Th and I4C dates from Bard et al. 1993a (triangles) and Edwards et al. 1993 (circles). The smooth line represents the values used in the

calibration program, while the dotted line represents modifications in light of the Edwards et al. (1993) data. The maximum smoothing function (S = 25), within the limits recom-

5 2 2 R.E. ‘TAYLOR, C. VANCE HAYNES, JR & MINZE STUIVER

mended by Reisch (1967), was used with the combined Bard and Edwards data since the uncertainty in the U/Th ages is not considered in the smoothing function.

Discussion In our view, there are two major issues in the ‘real time’ temporal relationship between Clovis and Folsom. First, what is the quality of the corpus of the associated 14C age estimates? Sec- ond, is it appropriate to use the U/Th-based data to calibrate conventional 14C values in the time-period represented by the Clovis and most of the Folsom samples?

FIGURE 5 presents an earlier summary of the published Clovis and Folsom 14C dates currently available (Haynes 1992), the equivalent Cali- brated value of each sample calculated with CALIB 3.0.3, Method B (Stuiver & Reimer 1993b), and the summed probability distribution for the combined calibrated Clovis and Folsom I4C data-sets. In this representation, the overlap between Clovis and Folsom appears to be significant.

The current suite of Clovis/Folsom 14C dates have been obtained over more than three decades on a variety of sample materials of variable quality. One of us (CVH) has undertaken a careful re-examination of the corpus of Clevis/ Folsom 14C values. For another region, time period and set of problems, a somewhat simi- lar effort has been labelled ‘chronometric hygiene’ (Spriggs 1989). TABLE 1 presents Clovis and Folsom 14C determinations which fulfil two criteria: 1 a secure stratigraphic relationship between

sample and a Clovis or Folsom site context, and

2 the least problematic sample material from a physiochemical perspective.

The selected 14C values listed in TABLE 1 are taken from Haynes (1992: table 24.1) with the following revisions: Hell Gap and Mill Iron 14C determinations are removed, Aubrey (Humphrey & Ferring 1994), Owl Cave (Miller 1982) and Lubbock Lake (Holliday et al. 1983: SMU-547) 14C values are added, and the Clovis Blackwater Draw determinations have been corrected. Hell Gap 14C values (A-502, A-503, A-504) are on bulk samples, exhibit large statistical errors, and appear to have questionable association. Also, it now appears that all nine Mill Iron site I4C values derive from contexts which are not

Folsom or Midland but Plainview-Goshen. Most samples listed in TABLE 1 are charcoal

or wood. As problems with biochemically-de- gradedbone continue (Stafford ,etal. 1990; 1991; Taylor 1992), it is our view that the 14C dates on bone from this age range and these contexts, even when specific amino acids are analysed, are more likely to be minimum values. Where there are multiple 14C values on bone, the old- est has been used since this value, in our view, probably more closely represents the actual age of the site or stratigraphic level. Where there are multiple 14C measurements for a single context, the l4C value cited is an average obtained by the method of Long & Rippeteau (1974). In all, 31 14C age determinations obtained from 10 Clovis-period sites and 25 I4C age determinations obtained from nine Folsom- period sites have been selected (TABLE 1).

Using the calibration data and algorithms of Stuiver & Reimer (1993a), the calibrated ranges of the values listed in TABLE 1 are represented in FIGURES 6a (Clovis sites) and 6b (Folsom sites). The calibrated values have be2n expressed at the *lo level (dark bands) and k2o level (light bands) with outer intersectio rls being represented as lines and open rectangles. To evalu- ate the degree of overlap between these two calibrated data-sets, FIGURE 7 presents the summed probability distributions for the combined Clovis (solid line) and Folsom (dashed line) data-sets from TABLE 1 iising the same methodology that generated FIGURE 5. Neither the combined Clovis data-set nor the Folsom data-set are from a single sample population as shown by the test statistic T’ where T’ = 33.5 and 36.3 respectively, withX2(.$15) = 16.9 (Ward & Wilson 1978). Using Bayesian theory, in this case with a uniform prior probability, the in- dividual probability distributions may be summed to provide a best estimate for the chronological distribution of the items dated (Buck et al. 1991).

For all but a few of the youn,gest Folsom 14C values, calibration depends on paired U/Th and 14C data from coral samples. Because of this, there are significant limitations in the degree of temporal resolution possible with these data. Corals grow in the mixed layer of the ocean where 14C changes in the oceanic mixed layer are smoothed by attenuation of the atmospheric I4C signal. A constant average j4C offset (R) or reservoir deficiency of 400 years has been ap-

CLOVIS AND FOLSOM AGE ESTIMATES: STRATIGRAPHIC CONTEXT AND RADIOCARBON CALIBRATION 5 2 3

FIGURE 7 . Summed probability distributions for the Clovis (solid) and Folsom (dashed) datasets listed in TABLE 1 and FIGURES 6a 6.6b. The basis on which the distributions have been calculated are the same as noted for FIGURE 5.


0.025

0 020 x

P

Y .r( I .3

2 0.015

k b)

0.005

0 .ooo 14,000 13,000 12,000 11,000 10,000

calibrated (calendar) age BP

plied to the coral data. The ‘atmospheric’ data- set obtained in this manner from coral data is the smoothed oceanic version, offset by 400 years.

The assumption of a constant reservoir deficiency is a first order approximation only. The actual reservoir deficiency may differ regionally as well as over time, since the contours of the atmospheric and mixed layer signals may differ. As a world-wide general average, the 400- year offset value appears to be a reasonable estimate. For the time-period with which we are concerned, ice-layer counting yields results which come within a few centuries of that obtained from the coral data (Stuiver et al. 1995). The possibility of regional coral 14C reservoir age differences currently limits the resolution of the pre-dendrochronological calibration data.

In further considering these data, no ‘error multiplier’ factors have been applied to the calibrated I4C values used in FIGURES 5, 6 & 7. These 14C values have been obtained from a number of laboratories over a period of more than two decades. Published data do not permit a pre- cise calculation of their ‘error multiplier’ factors. If an overall ‘average’ error multiplier of 1.8 would be applied, this would widen the distributions and make the offset between the two suites of 14C

values less significant.

Conclusion On the basis of stratigraphic evidence obtained from a number of sites, the latest North Ameri- can Clovis occupation predates the earliest occurrence of Folsom. With no means of cali- brating earlier than the youngest Folsom-associated I4C values, concern has been expressed that the degree of overlap indicated by conventional 14C values may not accurately reflect the actual, ‘real-time’ situation.

The development of U/Th-based calibration allows this question now to be addressed. We have used this data-base to calibrate, using the CALIB protocols, two sets of Clovis and Folsom I4C values. The first involves a comprehensive list of published values, and the second a set of Clovis and Folsom I4C age determinations that, in our view, are least problematic in terms of sample material and most secure in terms of stratigraphic context. In both cases, summed probability distributions for the combined Clovis and Folsom values were developed. The differences between these two representations reveals the importance of critically evaluating the stratigraphic and physiochemical integrity of the Clovis/Folsom 14C data. In presenting the calibrated Clovis and Folsom values, we rec- ognize the possibility of regional coral 14C res-


ervoir age differences and variable 'error multiplier' factors that limit the interpretation of the results. These initial results are first-order approximations only. As more calibration curve detail becomes available, the representations of the probability distributions will require revision.

It appears that the transition from Clovis to Folsom may have occurred within a period of 100 years or less (Haynes 1984). In our view, the existing corpus of Clovis and Folsom I4C age-estimates does not have the precision re- quired to test this assertion (Haynes 1991). One means of critically testing this hypothesis would be a series of high-precision (<+30 yr lo vari- ance] I4C values obtained on carefully pretreated, biochemically characterized samples collected from geologically well-documented stratigraphic profiles at multi-component sites containing Clovis and Folsom levels. Once the problems with biochemically-degraded bone are resolved (Stafford et al. 1991; 1992; Taylor 1992), direct I4C determinations on bone with low and trace

References BARD, E., M. ARNOLD, R.G. FAIRBANKS & B. HAMELIN. 1993a.

z30Th-z34U and 'T ages obtained by mass spectrometry on corals, Radiocarbon 35: 191-9.

BARD, E., M. STUIVER, & N.J. SHACKLETON. 1993b. How accu- rate are our chronologies of the past?, in J.A. Eddy & H. Oescbger (ed.), Global changes in the perspective ofthe past. New York (NY): John Wiley & Sons.

BATT, C.M. &A.M. POLLARD. 1996. Radiocarbon calibration and the peopling of North America, in M.V. Orna (ed.), Ar- chaeological Chemistry: Organic, Inorganic, and Biochemi- cal Analysis: 415-33. Washington (DC): American Chemical Society.

BECKER, B. 1993. An 11,000-year German oak and pine dendrochronology for radiocarbon calibration, Radiocar- bon 35: 201-13.

BucK,C.E.,M.B. KENWOKTHY,C.D. LITTON&A.F.M. SMITH. 1991. Combining archaeological and radiocarbon information: a Bayesian approach to calibration, Antiquity 65: 808- 21.

EDWARDS, R.L. 1993. A large drop in atmospheric 'nC/'ZC and reduced melting in the Younger Dryas, documented with z30Th ages of corals, Science 260: 962-8.

FRISON, G. 1991. Prehistoric hunters of the High Ploins. 2nd edition. San Diego (CA): Academic Press.

HAYNES, C.V., JR. 1971. Time, environment and early man, Arctic Anthropology 8: 2-14.

1984. StratigraphyandlatePleistocene extinction,inP.S. Martin & R.G. Klein led.), Quaternary extinctions: a prehistoric evolution. Tucson (AZ): University of Arizona Press.

1991. Geoarchaeological and paleohydrological evidence for a Clovis-age drought in North America and its bear- ing on extinction, Quaternary Research 35: 438-50.

1992. Contributions of radiocarbon dating to the geochronology of the peopling of the New World, in R.E. Taylor et al. (ed.), Radiocarbon after four decades: an interdiscplinary perspective. New York (NY): Springer- Verlag: 355-74.

In Press. Clovis-Folsom-Midland-Plainview Geochronology, in M. Jodry (ed.], Folsom archaeology. Washington (DC]:

amount of residual organics could be included in this data-set. These values would anticipate the resolution of questions concerning the accuracy and precision of the LJITh-based values on corals andlor a sufficient extension of dendrochronologially-based calibration data to include fully the time-period of Clovis and Folsom.

Acknowledgements. The UCR Radiocarbon Laboratory is supported by the National Science Founiation, the Gabrielle 0. Vierra Memorial Fund, the Lawrence Livermore National Laboratory Accelerator Mass Spectrometry Laboratory, the Academic Senate Intermural Research Fund and the Col- lege of Humanities, Arts and Social Sziences, University of California, Riverside. The Quaternary Isotope Labora- tory of MS and the Paleoindian stratigraphic research of CVH is supported by the National Science Foundation. We very much appreciate the collaboratioii of P. Reimer (Uni- versity of Washington) who prepared the figures used in this paper, the assistance of P. Wilke (Department of An- thropology, UC Riverside) in the preparation of FIGURE 2, the helpfulness of D.V. Gokhale (Department of Statistics, UC Riverside) and the comments of anonymous review- ers. This is contribution 95/04 of the Institute of Geophys- ics and Planetary Physics, University of California, Riverside.

Smithsonian Institution. Smithsonian contributions to anthropology.

HOLLIDAY, V.T., E. JOHNSON, H. HAAS, &R. STRUCKENRATH. 1983. Radiocarbon ages from the Lubbock Lake site 1950-1980: framework for cultural and ecological change in the south- ern High Plains, Plains Anthropologist 28: 165-82.

HUMPHREY, J.D. & C.R. FERRING. 1994. Stable isotopic evidence for latest Pleistocene and Holocene climatic change in north-central Texas, Quaternary Re.;earch 41: 200-13.

KROMER, B. & B. BECKER. 1993. German o3k and pine "C calibration, 7200-9439 BC, Radiocarbon 35: 125-35.

LONG, A. & B. RIPPETEAU. 1974. Testing cmmtemporaneity and averaging radiocarbon dates, Americcin Antiquity 39: 205- 15.

MELTZER, D.J. 1989. Why don't we know when the first people came to North America?, American Antiquity 54: 471-90.

1995. Clocking the first Americans, A inual Review ofAn- thropology 24: 21-45.

MILLER, S.J. 1982. The archaeology and geology of an extinct megafauna/fluted point association at Owl Cave, the Wasden site, Idaho, in J.E. Ericson ct al. (ed.), Peopling of the New World. Los Altos (CAI: Ballena Press.

measurement of German and Irish Oaks to show the natural I4C variations from 7890 to 5000 BC, Aadiocarbon 35: 93- 104.

measurement of Irish oaks to show the natural I4C variations from AD 1840-5000 BC, a correction. Radixarbon 35: 105-23.

PEARSON, G.W. & M. STUIVER. 1993. High-precision bidecadal calibration of the radiocarbon time scale, 500-2500 BC, Radiocarbon 35: 25-33.

RAMSEY, C.B. 1995. OxCal Program 2.28. Oxford: Oxford Uni- versity Radiocarbon Accelerator Unit.

REISCH, C.H. 1967. Smoothing by spline function, Numerische Mathemotik 10: 177-83.

SPRIGGS, M. 1989. The dating of the Island Southeast Asian Neolithic: an attempt at chronometiic hygiene and lin- guistic correlation, Antiquity 63: 58'7-613.

PEARSON, G.W., B. BECKER & F. QUA. 1993. High-precision

PEARSON, G.W. & F. QUA. 1993. High-precision

CLOVE AND FOLSOM AGE ESTIMATES: STRATIGRAPHIC CONTEXT AND RADIOCARBON CALIBRATION 525

STAFFORD, T.W., P.E. HARE, L. CURRIE, A.J.T. JULL & D.J. DONAHUE. 1990. Accuracy of North American human skeleton ages, Quaternary Research 34: 111-20.

1991. Accelerator radiocarbon dating at the molecular level, Journal of Archaeological Sciences 18: 35-72.

STUIVER, M. & B. BECKER. 1993. High-precision decadal calibration of the radiocarbon time scale, AD 1950-6000 BC, Radiocarbon 35: 35-65.

STUIVER, M. & T.G. BRAZIUNAS. 1993. Modeling atmospheric I4C influences and I4C ages of marine samples to 10,000 BC, Radiocarbon 35: 137-89.

STU~VER, M., P.M. GROOTES & T.F. BRAZIUNAS. 1995. The GISPZ P O climate record of the past 16,500 years and the role of the sun, ocean, and volcanoes, Quaternary Research 44: 341-54.

STUIVER, M. & G.W. PEARSON. 1993. High-precision calibration of the radiocarbon time scale, AD 1950-500 BC and 2500- 6000 BC, Radiocarbon 35: 1-23.

STUIVER, M. & P.J. REIMER. 1993a. Extended I4C data base and revised Calib 3.0 '4C age calibration program, Radiocar-

bon 35: 215-30. 1993b. CALIB User's Guide Rev 3.0.2. University of Wash-

ington, Quaternary Isotope Laboratory. TAYLOR, R.E. 1987. Radjocarbon dating an archaeological per-

spective. San Diego (CA): Academic Press. 1991. Frameworks for dating the late Pleistocene peopling

of the Americas, in T.D. Dillehay & D. Meltzer (ed.), The first Americans: search and research: 77-111. Boca Raton (FL): CRC Press.

1992. Radiocarbon dating of bone: to collagen and beyond, in R.E. Taylor et al. (ed.), Radiocarbon after four decades A n interdisciplinnryperspective: 375-402. New York (NY): Springer-Verlag.

VAN DER PLICHT, J. 1993. The Groningen radiocarbon calibration program, Radiocarbon 35: 231-7.

WARD, G.K. & S.R. WIISON. 1978. Procedures for comparing and comgbining radiocarbon age determinations: a cri- tique, Archaeometry 20: 19-31.

WORMINGTON, H.M. 1957. Ancient man in North America. Denver (CO): Denver Museum of Natural History.

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