14C Yr BP Research Articles

Radiocarbon Chronology/Growth Rates of Ooids from Great Salt Lake, Utah

Ooids (calcium carbonate coated grains) are common in carbonate environments throughout geologic time, but the mechanism by which they form remains unclear. In particular, the rate of ooid growth remains elusive in all but a few modern marine environments. In order to investigate the rate of ooid growth in a non-marine setting, we used 14C to date ooids from Great Salt Lake, Utah, a well-known site of aragonitic ooids. Bulk ooids obtained from the northern shore of Antelope Island and the northeast shore of Great Salt Lake near Spiral Jetty were sieved into different size fractions and produced mean ages ranging between 2728±15 and 4373±20 14C yr BP. Larger ooids were older than smaller ooids, implying that larger ooids grew in the environment for a longer duration, with the caveat that bulk age dating integrates the growth history of an ooid. To better resolve growth history, ooids from the coarse fraction were sequentially dissolved, and 14C ages were obtained for each dissolution step to create a time series of ooid growth. The results of the sequential dating indicate that the coarse Great Salt Lake ooid growth began between 5800-6600 ± 60 14C yr BP while their outer cortices are nearly modern. Sequentially dated ooids from the South Arm of Great Salt Lake at Antelope Island record a nearly linear growth history (~ 10-15 µm/kyr), whereas ooids from Spiral Jetty record somewhat faster growth between ~6000 and 4000 years ago (0.03 – 0.06 µm/yr) followed by a 10x slower growth history for the remainder of their lifespan (0.003 – 0.008 µm/yr). The lifespan of Great Salt Lake aragonitic ooids is two to six times longer than those from modern marine environments, and thus provides a unique end member for understanding the mechanisms behind ooid formation. The ooid age range indicates that geochemical parameters measured from bulk ooid dissolution integrates over ~6000 years and thus does not represent a geochemical snapshot in time, as some previous studies have suggested.

New radiocarbon age constraints on the eruption history of the Quill volcano, St. Eustatius, Dutch Caribbean

Abstract The late Pleistocene to Holocene subaerial pyroclastic deposits of the Quill stratovolcano on the Caribbean island of St Eustatius form seven stratigraphic divisions. New radiocarbon ages of charcoal are presented for the second, third and seventh divisions in order to better constrain the Quill’s eruption history. Three samples from the same layer of Division 2 at two localities on the northeast coast yield ages of 18,020 ± 40 (1σ), 18,310 ± 45 and 18,490 ± 45 14C yr BP (∼19,800–20,600 yr cal BC). These are considerably younger (∼4400 yr) than a previously published result for this division. A single sample of Division 3 gave an age of 8090 14C yr BP (∼7100 yr cal BC) and overlaps with previously published 14C ages for this division. A charred root in the pyroclastic unit deposited by the last eruption of the Quill (Division 7) gave an age of 919 14C yr BP (∼1100–1200 yr cal AD). This result is ∼600 years younger than a previously published age, and its origin is attributed to human activity. The timing of the last eruption of the Quill therefore remains poorly constrained but is older than 600 AD. Terrestrial gastropods found in paleosols and organic material found in small streams that developed in Division 3 indicate that Division 4 must be younger than 6100 ± 500 yr cal BC. The oxygen and carbon isotope composition of the terrestrial gastropods derived from Division 3 paleosols indicates that the C4 and CAM-type vegetation was dominant and that the climate subsequently changed to wetter conditions. The minimum eruption frequency for the Quill volcano is one eruption every ∼1400 years during the past 22,000 years. This eruption frequency of the Quill volcano is of the same order of magnitude as other recent northern Lesser Antilles volcanoes, Soufrière Hills (Montserrat, ∼5000 years) and Mt Liamuiga (St. Kitts, ∼2500 years).

Methane-flow system within the Nyegga pockmark field, offshore mid-Norway

We investigated fluid seepage within the Nyegga pockmark field (600–900 m water depths) off mid-Norway from Remotely Operated Vehicle dives at the so-called CNE sites (CNE01 to CNE17). The seafloor morphology of some of these features corresponds to pockmarks and adjacent ridges, with the latter being the focus of present seepage activity. These structures are underlain by chimneys above a gas-charged zone with, in some cases, a substantial body of hydrate-invaded sediment (down to 1.3 s in two-way travel time at CNE03). Present-day methane-rich fluid seepage through the seabed is indicated by chemosynthetic fauna, in particular Siboglinidae polychaetes (Oligobrachia haakonmobiensis webbi and Sclerolinum contortum), microbial mats and associated Rissoidae gastropod (Alvania sp.) grazers, and confirmed by measured in situ bottom-water methane anomalies, up to 2,130 nL/L. No free-gas bubble emissions were observed or acoustically identified. The presence of authigenic carbonates reveals past seepage with very low δ13C values (down to −58‰) indicating that the major source of carbon was methane carried by the venting fluids. The ages of major periods of methane venting are provided by vesicomyid bivalve shells (Isorropodon nyeggaensis) present in two sedimentary layers, 14,930 and 15,500 14C yr BP (ca. 17,238 and 17,952 cal yr BP), respectively, corresponding to the time of Melt Water Pulse IA. The seafloor morphology and pattern of seepage -chemosynthetic fauna and microbial mat distribution and dissolved methane concentration-are remarkably heterogeneous. Pore-water chemistry profiles in a gravity core taken only 40 m from major seepage sites indicate no seepage and anaerobic methane oxidation at a sub-bottom depth of about 2 m. Present-day seepage from the studied pockmark-chimney fluid-flow system charged with gas hydrate is dominated by the advection of methane solution in pore water. Some of this methane could result from the dissolution of hydrate in the chimney, most of which would have formed during an earlier period (post-LGM times) of history of the chimney, when it was venting free gas. However, the presence of free gas beneath this chimney is probably why the water entering the chimney is already saturated with methane and the process of hydrate formation in the chimney continues today.

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

AbstractMethane (CH4) and carbon dioxide (CO2) emissions from small peatland lakes may be highly sensitive to climate warming and thermokarst expansion caused by permafrost thaw. We studied effects of thermokarst expansion on ebullitive CH4 and CO2 fluxes and diffusive CH4 fluxes from a peatland thaw lake in boreal western Canada. Ebullitive CH4 fluxes from the thaw edge (236 ± 61 mg CH4 m−2 d−1) were double and quadruple that of the stable lake edge and center, respectively. Modeled diffusive CH4 fluxes did not differ between the thawing and stable edges (~ 50 mg CH4 m−2 d−1) but were double that of the center. Radiocarbon (14C) analysis of CH4 and CO2 bubbles from the thaw edge was older (~ 1211 and 1420 14C yr BP) than from the stable edge and the center (modern to ~ 102 and 50 14C yr BP, respectively). Incubations indicated that deep, old peat sediment was more labile along the thaw edge than in the center. While our study suggested increase CH4 emissions partly derived from millennial‐aged carbon along the thaw edge, accounting for these emissions only increased the estimated total lake CH4 emissions by ~ 10%, which is a much smaller contribution than measured from thermokarst lakes in yedoma regions. Our study suggests that it is important to account for landscape history and lake types when studying the processes that govern the sensitivity of lake greenhouse gas emissions to climate change.

THE MARINE RESERVOIR EFFECT: A CASE STUDY OF ARCHAEOLOGICAL SITES AT GUANABARA BAY, RIO DE JANEIRO, BRAZIL

ABSTRACTThis study applied, radiocarbon dating to charcoal and mollusk samples from Sernambetiba and Amourins archaeological sites in the Northeast region of Guanabara Bay, in the state of Rio de Janeiro, Brazil, to assess the marine radiocarbon reservoir effect (MRE) of this area, being applied for the correction of the marine samples ages. The results for this estuarine system were ΔR = –87 ± 90 14C yr and ΔR = –244 ± 70 14C yr for 3970 ± 70 14C yr BP and 2357 ± 60 14C yr BP, respectively. Based on these findings, calibrated 14C ages were calculated for Sernambetiba and Amourins shell mound sites surrounding the bay. Marine samples from the Guapi site were analyzed and only their radiocarbon ages presented because there were no paired terrestrial samples for the MRE assessment. These results are coherent with previously published values also derived from archaeological samples for the Rio de Janeiro state coastal region and contribute to the interpretation of human occupation of the region during the Holocene.

The Naco Clovis Site: Old Excavations and New Dates

ABSTRACT Archival research demonstrates that a previously unpublished second season of excavations took place at the Naco Clovis site in 1953, more than doubling the extent of the excavated area and revealing additional bones pertaining to a second mammoth. In 2020 small pieces of charcoal were found in sediment adhering to the distal fragment of a mammoth ulna from the Naco site. The bone was part of a 2011 donation to the Arizona State Museum by David Navarrete, grandson and nephew of the original discoverers of the site. Three AMS radiocarbon dates were obtained from individual wood charcoal fragments, and two more on a sample of multiple charcoal flecks. The first three have a weighted mean of 10,985 ± 56 14C yr BP (13,067–12,767 cal yr BP), fitting within the range of Clovis ages obtained from other Clovis sites; the other two ages are younger.

Late-Holocene advances of the Greater Azau Glacier (Elbrus area, Northern Caucasus) revealed by 14C dating of paleosols

Three paleosols buried in the left lateral moraines of the Greater Azau Glacier (Northern Caucasus) were identified in an excavated outcrop (43.2658 N, 42.4766 E, 2370 m a.s.l.). When the glacier was overlying the surface of the lateral moraines at this site, the thickness of the ice was 50 m and more above the valley floor. Fragments of charcoal from the uppermost soil (S1) buried 0.6 m below the surface yielded the radiocarbon date 130 ± 20 yr BP (IGANAMS-6826) (AD 1680–1939). The middle soil (S2), buried at the depth of 13 m yielded two 14C dates 320 ± 20 yr BP (IGANAMS-8127) (bark of birch) (AD 1496–1641) and 1190 ± 20 yr BP (IGANAMS-8126) (AD 774–889) (charcoal). We suggest that the soil S2 has been formed between these dates during the Medieval Warm Period and in the early Little Ice Age. The lowermost (S3) unit lying 15 m below the surface is the thickest (0.4–0.6 m), well-developed paleosol. Charcoal collected at the top of S3, yielded the date 1300 ± 20 yr BP (IGANAMS-6826) (AD 663–773), indicating a prominent glacier advance occurred shortly before this date. Two dates from the charcoal buried at the bottom of S3 (2855 ± 20 yr BP (IGANAMS-8125) and 2880 ± 20 yr BP (IGANAMS-6827) mark the beginning of a long episode of restricted glacier extent that lasted for about 1600 years. The dates at the bottom of the S3 paleosol constrain the end of glacier advance that occurred before 2800–2900 14C yr BP. The timing of most prominent advances of the Greater Azau Glacier in the past 3500 years is in general agreement with the Late-Holocene glacial chronologies in the European Alps, Scandinavia and other regions of the Northern Hemisphere.

New Record of Terminal Pleistocene Elk/Wapiti (Cervus canadensis) from Ohio, USA

The earliest appearance of elk/wapiti (Cervus canadensis) in eastern North America is not thoroughly documented due to the small number of directly dated remains. Until recently, no absolute dates on elk bone older than 10,000 14C yr BP (11,621 to 11,306 calibrated years (cal yr) BP) were known from this region. The partial skeleton of the Tope Elk was discovered in 2017 during commercial excavation of peat deposits from a small bog in southeastern Medina County, Ohio, United States. Subsequent examination of the remains revealed the individual to be a robust male approximately 8.5 years old at death. The large size of this individual is compared with late Holocene specimens and suggests diminution of elk since the late Pleistocene. Two accelerator mass spectrometry (AMS) radiocarbon assays on bone collagen samples taken from the scapula and metacarpal of this individual returned ages of 10,270 ± 30 14C yr BP (Beta-477478) (12,154 to 11,835 cal yr BP) and 10,260 ± 30 14C yr BP (Beta-521748) (12,144 to 11,830 cal yr BP), respectively. These results place Cervus canadensis in the terminal Pleistocene of the eastern woodlands and near the establishment of the mixed deciduous forest biome over much of the region. This early temporal placement also situates this early elk as closely following the last representatives of now-extinct megafauna such as the American mastodon (Mammut americanum) and contemporary with the Late Paleoindian inhabitants of the region.

Improved pretreatment method for the isolation and decontamination of pyrogenic carbon for radiocarbon dating using hydrogen pyrolysis

Abstract Pyrogenic carbon (charcoal, black carbon, elemental carbon) is one of the most common materials used for radiocarbon dating of terrestrial samples. However, exogenous carbon contamination can compromise the accuracy of radiocarbon ages. This study presents the results of two chemical pretreatments prior to hydrogen pyrolysis (hypy) as improved protocols for the isolation and decontamination of pyrogenic carbon, i) a simple acid-oxidation step (A-Ox/hypy) and ii) acid-base-acid (ABA/hypy). The A-Ox/hypy protocol uses HNO3 and H2O2, while ABA/hypy uses HCl and NaOH. Both pretreatments remove labile and inorganic carbon before hypy, decreasing the potential for in situ production of pyrogenic carbon during the hypy reaction. The effectiveness of each protocol was directly measured on charcoal artificially produced at 350 °C, 450 °C and 550 °C from radiocarbon-free wood, and exposed to environmental contamination for 1–3 yrs. The results show a >94% reduction in carbon contamination for the 450 °C and 550 °C charcoal samples occurred using A-Ox/hypy, but this treatment was less effective for the 350 °C charcoal. A >99% reduction in carbon contamination in all charcoal samples examined occurred using ABA/hypy. The A-Ox/hypy protocol was further tested on cave guano sediments, which had previously reported erroneous dates following simple organic solvent extraction followed by ABA pretreatment. Effective decontamination was achieved using A-Ox/hypy on the guano, which corrected a radiocarbon age reversal. Overall, ABA/hypy effectively decontaminated the charcoals and was a more efficient pretreatment for charcoal than A-Ox/hypy, however resulting in larger sample mass loss. Therefore, ABA/hypy is the recommended protocol for older (>30,000 14C yr BP) charcoal or sediment samples, or where date accuracy is imperative, while A-Ox/hypy represents an improved protocol for the quick and cost-effective measurement of younger samples (

Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines

In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (14C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments.

Otoliths as indicators for fish behaviour and procurement strategies of hunter-gatherers in North Patagonia

This study evaluates the potential use of archaeological otoliths of Genidens barbus (Cuvier and Valenciennes) as a tool to study fish behavior and hunter-gatherers procurement strategies on the North Patagonian coast. The studied samples come from the San Antonio archaeological locality dated at ca. 1000-800 14C yr BP (Late Holocene). To assess whether exposure to fire significantly affects the otolith Sr:Ca and Ba:Ca ratios, burned and unburned modern lapilli otoliths have been analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry and no statistically significant differences were found between the results of both treatments. Core-to-edge chemical time series were carried out on ancient otoliths (ca. 1000 14C yr BP) in order to study the fish life history. Three amphidromous patterns were found for ancient samples. The capture environments and seasons inferred by the otolith edge chemistry and marginal increase, respectively, suggest a location in high salinity water (estuary and sea) in summer. Finally, to estimate the size of archaeological fish, a linear regression between total length and otolith length was constructed using 70 modern catfish otoliths. The size variability (358–610 mm) might indicate the use of non-selective capture techniques, probably nets, by hunter-gatherer groups.

Abrigo La Tinta: Preliminary Results of a New Late Pleistocene-Early Holocene Rockshelter from the Pampas Region (Tandilia Range), Argentina

ABSTRACT Abrigo La Tinta (La Tinta Rockshelter) is located in the Tandilia mountain range of Argentina. The excavation of two test-pits during a survey revealed buried archaeological remains, including lithic artifacts, ceramic, mineral pigments, and charcoal. A charcoal fragment recovered in the deepest section of Test-pit 2, in association with quartzite and chert flakes, was dated in 10,414 ± 32 14C yr BP (12,408 to 12,041 cal yr BP), suggesting a late Pleistocene-early Holocene human occupation.

Geoarchaeology of the Water Canyon Paleoindian site, west‐central New Mexico

AbstractWater Canyon is a rare buried, multicomponent, stratified Paleoindian site in west‐central New Mexico. This paper presents a geoarchaeological assessment of the site as part of a broader interdisciplinary investigation of its paleoenvironmental history and archaeology. The archaeology is associated with ancient wetland deposits (Stratum 6) within an alluvial fan. The fan formed initially through the late Pleistocene. Formation of the fan stopped and wetland deposition began ~11,310 14C yr BP (~13,170 cal yr BP). Stratum 6 evolved via wetland deposition and cut‐and‐fill cycles. The bulk of Stratum 6 dates <10,300 14C yr BP (<12,200 cal yr BP). One, or possibly two, beds of bison bone, likely processing‐stations, were found on the margin of the paleowetland and date to ~9,200 14C yr BP (~10,400 cal yr BP) (lower bone bed) and ~8,200 14C yr BP (~9,150 cal yr BP) (upper bone bed). Farther out in the paleo‐wetland a probable kill site was discovered with an in situ Eden projectile point dated to at least ~8,955 14C yr BP (~10,070 cal yr BP). The wetland landscape returned to an alluvial fan system <8,000 14C yr BP (<8,900 cal yr BP) with two more cycles of fan deposition by ~6,500 cal yr.

Holocene sedimentary facies in coastal plain of the Song Ma Delta, Thanh Hoa Province

The Ma river delta located in the North Central of VietNam is the third largest ones in Vietnam following the Mekong Delta and the Red River Delta. However, there are not many researches on sedimentary. This study aims to determine the Characteristics of the Holocene sedimentary facies in coastal plain of the Song Ma Delta based on observation of sedimentary structure and analysis of grain size, diatom, flora, pollen and 14C dating collected for the drill core (LKTH2 borehole) from the coastal plain of the Song Ma river delta. Research results identify 08 facies consisting 02 facies of transgression period and 06 facies of regression period. During transgression period, 02 facies of tidal flat clayish silt and bay silty clay facies were formed. Of which, tidal flat clayish silt face was formed in 7,883 ± 43 14C yr BP. After the maximum flooding of the sea, the delta was initiated and 06 facies were formed during the regression period i.e. prodelta silty clay, delta front clayish silt, tidal flat sandy - silty clay, sand ridge, lagoonal sandy silty clay, and flood plain silty clay facies. The tidal flat sandy - silty clay facies occurred in 6.951± 38 14Cyr BP caused by sea level fall and the coastline was identified around the LKTH2 bore hole at that time. Integration of sedimentary facies of the sand ridge and lagoonal sandy silty clay facies shows that the Song Ma Delta was dominated by wave process during its evolution.

The old bone project: Quality assurance on radiocarbon dating bone in the 30,000–50,000 age range at the A.E. Lalonde AMS Laboratory (Ottawa, Canada)

A quality control program was undertaken to test the merit of different techniques for the preparation of Late Pleistocene bone at the A.E. Lalonde AMS Laboratory in Ottawa (Canada). The samples studied here include a mammoth bone (S-EVA 2000) previously dated by other labs (Oxford, Kiel, Mannheim) with results ranging between 35,280 and 31,660 14C yr BP (n = 10), a bison bone (S-EVA 2001) previously dated between 47,300 and 40,200 14C yr BP (n = 9; Talamo and Richards, 2011), and our in-house background standard (Hollis Mine Mammoth, HMM). Samples were prepared in four different ways: (1) no ultrafiltration and combustion by elemental analyser (EA); (2) ultrafiltration and EA combustion; (3) no ultrafiltration and quartz tube combustion; (4) ultrafiltration and quartz tube combustion. All four methods produced dates for the S-EVA 2000 bone between 34,530 and 34,080 14C yr BP (n = 7) and consistent stable isotope data (δ13C, δ15N, C:N). Results for the HMM bone ranged from 54,600 to 46,800 14C yr BP. Further, the S-EVA 2001 was prepared without ultrafiltration and combusted on the EA, resulting in a date of 45,010 ± 460 14C yr BP. Finally, since a major challenge with dating Late Pleistocene bone is to decipher between finite and infinite ages, we report results from two years of measurement of the HMM bone, which is prepared with each bone batch. The average age of the HMM is 50,700 ± 3400 14C yr BP (n = 17) when not ultrafiltered, and 48,400 ± 2900 14C yr BP (n = 13) when ultrafiltered. Results from this study do not reinforce or negate the use of ultrafiltration, but it was determined that combustion by EA is preferred as it gives %C and %N values.

Raw-material Procurement and Landscape Use during the Pleistocene/Holocene Transition in the Eastern Tandilia Range (Buenos Aires, Argentina)

ABSTRACTThis paper analyzes the use of lithic resources by hunter-gatherer groups during the Pleistocene/Holocene transition (c. 10,000 14C yr BP) in the eastern Tandilia Mountain Range (Pampas region, Argentina). The lithic assemblages of nine archaeological sites were recovered in sedimentary sequences from caves and rockshelters. The results show that the first human groups who inhabited the micro-region had a wide knowledge of the landscape and sources, and developed a highly selective acquisition of rocks, transporting them from different sources. Among these rocks, two different sedimentary rocks (orthoquartzites) were the most used: the first locally available and the second located 100 km away from the study area. Additional raw-material sources are located 400 and 500 km away from the archaeological study area and were used with different intensities in the studied sites.

Early Holocene water well in the Pampas of Argentina: Human responses to water shortage events

Water wells are ethnographically and archaeologically described in Australia and the plains of North America. Recently, a prehistoric water well from the early Holocene was recorded in the Pampas of Argentina. The aim of this paper is to present the main characteristics of the water well, considering its form, dimension, sediment analyses (texture and chemical parameters), and material culture content. This is the first water well recorded in the Pampas of Argentina. Consequently, a discussion about natural or cultural origins of this kind of features is provided. An evaluation of similarities and differences with well-described water wells from the United States and Australia is included in order to highlight the cultural origin of the pit. Also, the meaning of the cultural response to water availability in terms of early-Holocene hunter–gatherer adaptations as well as the implications of this strategy for understanding paleoenvironmental scenarios of the Pampas of Argentina are discussed. The well seems to have mitigated an exceptional lack of surface water in the eastern Pampas or offered an alternative for the non-drinkable quality of the available surface water. The strategy of digging water wells was available in the behavioral repertoire of the Pampean hunter–gatherer populations as early as c. 8700–800014C yr BP ( c. 9700–8800 cal. yr BP), as these groups were fairly flexible and resilient in dealing with short-term shortages of water.

Geoarchaeology and taphonomy: Deciphering site formation processes for late Holocene archaeological settings in the eastern Pampa-Patagonian transition, Argentina

Assessing the integrity and resolution of archaeological sites in sandy environments is a key issue for understanding site formation processes in hunter-gatherer's contexts. A case study from the lower course of the Colorado River, at the eastern Pampa-Patagonian transition (Argentina) is presented here. The studied area is characterized by a sand dune relief that is superimposed upon ancient fluvial and marine environments. The sites date to between c. 2000 and 250 14C yr BP (late Holocene) and they are mostly located in eolian contexts. The objective of this paper is to understand environmental dynamics and the site formation processes that operated in archaeological sites of the late Holocene through the integration of geoarchaeological and taphonomic information. The obtained results allowed the identification of site formation processes related to the different environmental settings (coast, ancient delta and inland). However, general patterns that relate some taphonomic effects as root action and weathering with landscape processes such as pedogenesis at an areal scale were also recognized. Despite the varied and highly dynamic environmental conditions of this arid-semiarid area, archaeological contexts with good degrees of resolution and integrity were recognized.

The Muknal cave near Tulum, Mexico: An early-Holocene funeral site on the Yucatán peninsula

Here, we report on an incomplete human skeleton, soot patches related to anthropogenic fireplaces, and cut marks on the mandible of an extinct peccary, from the submerged Muknal cave southwest of Tulum on the Mexican Yucatán peninsula. The human individual, here named ‘Muknal Grandfather’, was identified as a male based on cranial parameters. The age at the time of death was estimated to be between 40 and 45 years. We propose that the human bones have been brought to the cave during the latest Pleistocene or early Holocene, but not later than 8600 14C yr BP (ca. 9600 cal BP), as a secondary burial of a partial skeleton. The peccary mandible was placed close to the burial site, possibly as part of the same ritual. The Muknal cave therefore served as a place for funeral rituals.

OSL and AMS 14C Age of the Most Complete Mammoth Fossil Skeleton from Northeastern China and its Paleoclimate Significance

ABSTRACTApplying radiocarbon (14C) dating using accelerator mass spectrometry (AMS) to the skeleton of a mammoth and the associated plant remains have been dated. The fossil of Zhalai Nur mammoth was dated to 43,500 +1000/–900 14C yr BP. The results of optically stimulated luminescence (OSL) dating, which show that a fluvially deposited gravel layer, from that the mammoth fossils were excavated, formed between 51,300±2100 and 26,600±1200 yr BP, place the new AMS 14C dates in a well-developed chronological framework. Through this study, it can be summarized that, firstly, using suitable sample material, it is possible to obtain reliable AMS 14C results, even when the ages of the target materials approach the upper limits of the method. Second, it reveals that a depositional hiatus exists during the Late Pleistocene, between ca. 26,000 yr BP and ca. 13,000 yr BP. Finally, large rivers and widely distributed areas of alluvial-fluvial deposits existed in this present-day desert area between ca. 51,000 and 26,000 yr BP. These results may shed new light on the study of the Mammuthus-Colelodonta-Bubalus fauna, the most important and fully developed fauna during the Late Pleistocene in northeastern China. They also deepen our understanding about the eco-environments of the region.