In the hyperarid eastern Sahara, west of the Nile River in Egypt, areas with vegetated eolian mounds have attracted people and animals because of shallow groundwater that at times of high water tables may be reached by hand digging shallow wells. An eolian phreatophytic mound with a living arak bush (Silvadora persica L.) on top, one of three known from this region of SW Egypt, provided a stratigraphic record of its growth. The geochronology of the mounds aggradation and that of a nearby tarfa mound (Tamarix nilatica Bunge) was determined by radiocarbon dating plant macrofossils within the stratigraphic succession. Eolian aggradation of the mound postdates deflation that eroded playa sediments of the Neolithic pluvial that ended ca. 5000 BP and appears to be due to a resurgence of the shallow aquifer. Subsequent deflation of the mounds is apparently due to post-1500 BP aridity. Regional vegetation is described in the Appendix I.

Archaeologists have long subjected Clovis megafauna kill/scavenge sites to the highest level of scrutiny. In 1987, a Columbian mammoth (Mammuthus columbi) was found in spatial association with a small artifact assemblage in Converse County, Wyoming. However, due to the small tool assemblage, limited nature of the excavations, and questions about the security of the association between the artifacts and mammoth remains, the site was never included in summaries of human-killed/scavenged megafauna in North America. Here we present the results of four field seasons of new excavations at the La Prele Mammoth site that confirm the presence of an associated cultural occupation based on geologic context, artifact attributes, spatial distributions, protein residue analysis, and lithic microwear analysis. This new work identified a more extensive cultural occupation including the presence of multiple discrete artifact clusters in close proximity to the mammoth bone bed. This study confirms the presence of a second Clovis mammoth kill/scavenge site in Wyoming and shows the value in revisiting proposed terminal Pleistocene kill/scavenge sites.

At the Murray Springs Clovis site in southeastern Arizona, stratigraphic and geomorphic evidence indicates that an abnormally low water table 10,900 yr B.P. was followed soon thereafter by a water-table rise accompanied by the deposition of an algal mat (the “black mat”) that buried mammoth tracks, Clovis artifacts, and a well. This water-table fluctuation correlates with pluvial lake fluctuations in the Great Basin during and immediately following Clovis occupation of that region. Many elements of Pleistocene megafauna in North America became extinct during the dry period. Oxygen isotope records show a marked decrease in δ18O correlated with the Younger Dryas cold-dry event of northern Europe which ended 10,750 yr B.P., essentially the same time as the water table began to rise in southeastern Arizona. Clovis hunters may have found large game animals easier prey when concentrated at water holes and under stress. If so, both climate and human predation contributed to Pleistocene extinction in America.

The discovery, identification, and radiocarbon dating of the large achatinid land snail Limicolaria kambeul chudeaui at six places in northwestern Sudan, north of the 100-mm isohyet, provide convincing evidence that at least 300 mm annual rainfall existed there 6000 yr ago. Since then the rainfall north of ca. 20°N lat in the eastern Sahara has certainly been <300 mm and probably <200 mm. Accelerator mass spectrometry has allowed the organic fraction, presumably conchiolin, to be accurately radiocarbon dated whereas carbonate fractions are ca. 600 yr too old. Comparative studies show the subfossil form, L. k. chudeaui, to be the most primitive in its species complex and to occupy a narrow east-west belt across Africa north of 15°N and west of 35°E. The northern limit of living forms lies within the southern part of the Sahelian zone in forest or forest-savanna. They cannot live in open grassland. Therefore, the distribution of L. k. chudeaui marks the former northern position of this zone during the middle Holocene, indicating a latitudinal shift of at least 5° (500 km).

The Miami site, excavated in 1937, is in a small "playa" basin on the High Plains surface. The site is one of the earliest documented co-occurrences of Clovis points and mammoth. Reinvestigation of the site and related collections was undertaken to better understand the stratigraphy, geochronology, and archaeology. The basin, 23 m diameter × 1.6 m deep, filled with (1) dark gray silty clay, and (2) near the top of the section, a lens of well-sorted silt or loess. The basin started to fill ca. 13,700 yr B.P., the loess dates to ca. 11,400 yr B.P., and the bone bed probably dates to ca. 11,400-10,500 yr B.P. The loess may be the local manifestation of a "Clovis drought." The partial remains of five mammoths (three adults and two juveniles) were recovered in 1937; no other animal remains are known. The bone is heavily weathered and there are no clear indications of human modification. Artifacts found at the site include three Clovis points and a scraper found among the bones and two flakes and a scraper found on the surface near the playa. The origins of the bone and stone assemblage are uncertain but four scenarios are offered: a successful mammoth kill, an unsuccessful kill with wounded animals dying at the watering hole, opportunistic scavenging following natural deaths, or a palimpsest of multiple deaths following both natural and human causes.

Discovery in 1980 of Camp 18 of the 1930 Bagnold expedition in northwestern Sudan has resulted in an exceptionally long record of barchan movement from which an average rate of 7.5 m/yr has been calculated. Measurements of the rate of dune advance since 1980 have not varied significantly, indicating a state of quasiequilibrium exists. The dune field is moving over an undulating sand sheet exhibiting various stages of Holocene pedogenesis and containing Neolithic sites. The sand sheet overlies Pleistocene alluvium with stronger stages of pedogenesis. All of these deposits may be a significant source of dune sand. Wind-blown grass fragments trapped by advancing slipfaces mark former slipface positions and indicate late Holocene rainfall events, which can be radiocarbon dated. Parabolic forms (revealed by SPOT images) at the windward ends of the dune fields are transitional to barchans, suggesting sand accumulation in vegetation germinated during a Holocene wet period. In addition, sand streaks from sand-sheet undulations suggest that active eolian erosion of sand sheets contributes to the sand supply of dune fields. Pedogenesis during pluvial periods contributes to silt and clay fractions of bimodal sand sheet sediments. From wind streaks on LANDSAT images and an estimated average rate of dune advance, positions of dune fields during past hyperarid periods can be estimated.

Sandia Cave generated much interest when in the 1940s extinct Pleistocene megafauna were reported in association with what appeared to be a pre-Folsom Paleoindian component. By the 1950s a series of controversies regarding the stratigraphy and dating began to push the site into obscurity. The human occupation at the site has never been directly dated beyond 2250 ± 50 BP, and nonartifactual associated bone will not provide reliable age estimates because of extensive bioturbation, poor provenience, and the fact that the majority of fossils were accumulated by carnivores and rodents, rather than humans. However, a small number of mineralized fragments display human modification, suggesting occasional human activity of some antiquity at the site. One bone tool, one burned bone, and four bones bearing butchery marks were subjected to direct Accelerator Mass Spectrometry (AMS) 14C dating. Unfortunately, mineralized bones did not preserve sufficient collagen to be dated. Two unmineralized specimens (the burned bone and the bone tool) push the direct Chronometric ages for the human occupation at Sandia Cave back to 3447 ± 96 BP. An older Folsom occupation is suggested by associated dates on breccia, but all lines of evidence taken together provide no support for a pre-Folsom human occupation.

Radiocarbon dating of charcoal samples and a re-examination of the artifacts from the Volcanic Debris layer in Ventana Cave were conducted in 1992-1994. The goal of this research was to better understand the chronological position and cultural affinities of the Ventana Complex, the name applied to the assemblage recovered from the Volcanic Debris. Ten new Accelerator Mass Spectrometry (AMS) 14C ages suggest that the Volcanic Debris accumulated between approximately 8800 B.P. and 10,500 B.P., and the lack of stratigraphic ordering of the dates indicates that the Volcanic Debris was subjected to considerable turbation as it accumulated. This turbation may have led to the incorporation of bones of extinct fauna from an underlying conglomerate deposit rich in horse remains, creating the impression of their association with artifacts. The artifacts are probably the product of episodic, special-purpose occupations spanning centuries or millennia. Technological and morphological studies of the stone tools indicate few similarities with classic Paleoindian industries, and greater similarities to early Holocene Archaic occupations in the Great Basin and Southwest. Correlations of the Ventana Cave stratigraphy with that of southeastern Arizona and with the late Pleistocene and Holocene record of Northern Hemisphere climate are explored.

Radiocarbon measurements have been obtained on contemporary plant samples collected at the site of Monte Verde, Chile, to examine the possibility that a local l4C reservoir effect impinges on the accuracy of the l4C values obtained on previously recovered archaeological samples. The l4C activity of the modern plants do not reveal any offset from expected contemporary l4C values and thus provide no support for a major postulated reservoir effect at least for the recent past. Although there is, at present, no direct means of measuring potential l4C reservoir offsets in the late Pleistocene for this region, we are not aware of any current data that would indicate that there have been major changes during geologically recent times.

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.

F. E. Green has corrected errors regarding the provenience and prior determination of the artifactual nature of the ivory semifabricate reported by Saunders et al. (1990) and has brought forth new information regarding the spring deposits of the north bank of the gravel pit at the Clovis site. This statement addresses the contemporaneity of Clovis occupation with deposition of the gray sand and the relation of the gray sand to spring deposits. We offer it in expectation that a better understanding of north-bank stratigraphy and geochronology might result regardless of which of two views of the archaeology of the gray sand eventually prevails.

A carved segment of mammoth ivory recently recognized in a faunal collection from the Clovis type site at Blackwater Draw, New Mexico, reveals for the first time techniques employed by Clovis Paleoindians for working ivory and adds a new trait element shared between the archaeological cultures of the Eurasian Upper Paleolithic and the late Pleistocene Clovis complex of North America.

Infrared (IR) spectrophotometry and X-ray diffraction (XRD) were conducted on modern and fossil bone material from archaeological sites in the U S to determine post-mortem changes in bone apatite and to evaluate the effect of these changes on radiocarbon dating. IR absorption bands, XRD peak-broadening parameters, and XRD unit cell measurements indicated that during fossilization, bone apatite, a mineral similar to dahllite, was partially or completely recrystallized to francolite. Post-mortem changes involved then removal of some of the endogenous crystal carbonate both at surfaces and at internal OH-sites and introduction of exogenous carbonate into internal crystal PO4 sites. Increased fluorine content accompanied carbonate substitution.

Both the carbon isotopic composition and the amount of exogenous carbonate introduced into the apatite structure will affect the radiocarbon dating of bone apatite. Special sample pre-treatment may remove most of the substituted carbonate in some cases. Simulated experiments are suggested for a better understanding of the nature and mechanism of carbonate substitution in bone apatite for the removal of the exogenously substituted carbon and the improvement of radiocarbon dates.

The carbon isotopic analyses reported here covers the period since the last list (Haynes et al., 1967) until summer 1969. All results relating to secular C14 fluctuations in atmospheric CO2 are now published separately (Damon et al., 1970). Sample preparation and counting procedures remain essentially unchanged since completion of our conversion to CO2 in 1960. All δC13 values are reported relative to PDB and all C14 dates, unless otherwise noted, are based on the 5568 year half-life, but are not corrected for C13 content. 0.95 NBS oxalic acid activity is our routine standard periodically monitored for isotopic fractionation.

The C14 measurements reported here were madein this laboratory between November 15, 1965 andJune 15, 1966. Sample descriptions are classified asfollows:

1. I. GeochemicalSamples

2. II. Geologic-PaleoclimaticSamples

3. III. EarlyMan-Alluvial StratigraphySamples

4. IV. ArchaeologicSamples

Geologic investigation and radiocarbon dating of a newly exposed stratigraphic section at the famous Early Man site of Blackwater No. 1 (Clovis) in eastern New Mexico show the Brown Sand Wedge to be in part a contemporaneous facies of the Diatomaceous Earth (10,000 to 11,000 years old) and in part older (11,000 to 11,500 years old). The Gray Sand is probably more than 12,000 years old. Artifacts contained therein are concentrated in the upper 6 in. and are believed to have intruded the sand via the tramplings of the surface by man and animals.

The discovery of ancient spring-feeder conduits confirms the springhead origin for the Brown Sand Wedge and the Gray Sand suggested by Sellards and Evans (1960). In addition to well-sorted, nearly spherical, graded, quartz grains the conduits contained Clovis, Folsom, and Agate Basin artifacts bearing an extremely high polish. Some Agate Basin points appear to have been coeval with Folsom points; others are younger. Deposition of the Carbonaceous Silt containing Scottsbluff points, Frederick points, and points of the Portales complex began as early as 9,800 years ago, and possibly continued as late as 7,000 years ago.

Two bone objects from the Tule Springs site, possibly tools, occurred in ancient sedimentary fill of a small spring outlet-channel remnant. The ancient spring was active more than 40,000 years ago and again 12,000 to 13,000 years ago. The fill and the bone contained therein could be of either age. Chemical and X-ray analysis on bone of the known ages and bone from the fill showed no significant or systematic differences in fluorine, uranium, nitrogen, or phosphate content. On geological grounds, it is concluded that the bone objects are 12,000 to 13,000 years old.

The C14 measurements reported here were made in this laboratory between November 1, 1963 and November 15, 1965. Sample descriptions are classified as follows:

1. I. Geochemical Samples

2. II. Geologic-Paleoclimatic Samples

3. III. Early Man-Alluvial Stratigraphy Samples

4. IV. Archaeologic Samples

Fossil pollen is directly associated with a radiocarbon date, mammoth bones, and the same stratigraphic units in which mammoth, bison, tapir, and horse bones and Clovis artifacts were recovered at the Lehner site. The pollen evidence indicates that desert grassland occupied the San Pedro Valley of southeastern Arizona about 9000 B.C.