Carbon-14 Years Research Articles

Monte Verde: Seaweed, Food, Medicine, and the Peopling of South America

The identification of human artifacts at the early archaeological site of Monte Verde in southern Chile has raised questions of when and how people reached the tip of South America without leaving much other evidence in the New World. Remains of nine species of marine algae were recovered from hearths and other features at Monte Verde II, an upper occupational layer, and were directly dated between 14,220 and 13,980 calendar years before the present ( approximately 12,310 and 12,290 carbon-14 years ago). These findings support the archaeological interpretation of the site and indicate that the site's inhabitants used seaweed from distant beaches and estuarine environments for food and medicine. These data are consistent with the ideas that an early settlement of South America was along the Pacific coast and that seaweeds were important to the diet and health of early humans in the Americas.

Four-thousand-year-old gold artifacts from the Lake Titicaca basin, southern Peru

Artifacts of cold-hammered native gold have been discovered in a secure and undisturbed Terminal Archaic burial context at Jiskairumoko, a multicomponent Late Archaic-Early Formative period site in the southwestern Lake Titicaca basin, Peru. The burial dates to 3776 to 3690 carbon-14 years before the present (2155 to 1936 calendar years B.C.), making this the earliest worked gold recovered to date not only from the Andes, but from the Americas as well. This discovery lends support to the hypothesis that the earliest metalworking in the Andes was experimentation with native gold. The presence of gold in a society of low-level food producers undergoing social and economic transformations coincident with the onset of sedentary life is an indicator of possible early social inequality and aggrandizing behavior and further shows that hereditary elites and a societal capacity to create significant agricultural surpluses are not requisite for the emergence of metalworking traditions.

Phytolith evidence for early Holocene Cucurbita domestication in southwest Ecuador.

Cucurbita (squash and gourd) phytoliths recovered from two early Holocene archaeological sites in southwestern Ecuador and directly dated to 10,130 to 9320 carbon-14 years before the present (about 12,000 to 10,000 calendar years ago) are identified as derived from domesticated plants because they are considerably larger than those from modern wild taxa. The beginnings of plant husbandry appear to have been preceded by the exploitation of a wild species of Cucurbita during the terminal Pleistocene. These data provide evidence for an independent emergence of plant food production in lowland South America that was contemporaneous with or slightly before that in highland Mesoamerica.

Mediterranean Sea surface radiocarbon reservoir age changes since the last glacial maximum.

Sea surface reservoir ages must be known to establish a common chronological framework for marine, continental, and cryospheric paleoproxies, and are crucial for understanding ocean-continent climatic relationships and the paleoventilation of the ocean. Radiocarbon dates of planktonic foraminifera and tephra contemporaneously deposited over Mediterranean marine and terrestrial regions reveal that the reservoir ages were similar to the modern one (approximately 400 years) during most of the past 18,000 carbon-14 years. However, reservoir ages increased by a factor of 2 at the beginning of the last deglaciation. This is attributed to changes of the North Atlantic thermohaline circulation during the massive ice discharge event Heinrich 1.

The earliest archaeological maize (Zea mays L.) from highland Mexico: new accelerator mass spectrometry dates and their implications.

Accelerator mass spectrometry age determinations of maize cobs (Zea mays L.) from Guilá Naquitz Cave in Oaxaca, Mexico, produced dates of 5,400 carbon-14 years before the present (about 6,250 calendar years ago), making those cobs the oldest in the Americas. Macrofossils and phytoliths characteristic of wild and domesticated Zea fruits are absent from older strata from the site, although Zea pollen has previously been identified from those levels. These results, together with the modern geographical distribution of wild Zea mays, suggest that the cultural practices that led to Zea domestication probably occurred elsewhere in Mexico. Guilá Naquitz Cave has now yielded the earliest macrofossil evidence for the domestication of two major American crop plants, squash (Cucurbita pepo) and maize.

High-resolution holocene environmental changes in the thar desert, northwestern india

Sediments from Lunkaransar dry lake in northwestern India reveal regional water table and lake level fluctuations over decades to centuries during the Holocene that are attributed to changes in the southwestern Indian monsoon rains. The lake levels were very shallow and fluctuated often in the early Holocene and then rose abruptly around 6300 carbon-14 years before the present (14C yr B.P.). The lake completely desiccated around 4800 (14)C yr B.P. The end of this 1500-year wet period coincided with a period of intense dune destabilization. The major Harrapan-Indus civilization began and flourished in this region 1000 years after desiccation of the lake during arid climate and was not synchronous with the lacustral phase.

Early Central Andean Metalworking from Mina Perdida, Peru

Copper and gold artifacts in contexts dated to approximately 3120 to 3020 carbon-14 years before the present ( approximately 1410 to 1090 calendar years B.C.) recovered in excavations at Mina Perdida, Lurin Valley, Peru, show that artisans hammered native metals into thin foils, in some cases with intermediate anneals. They gilded copper artifacts by attaching gold foil. The artifacts show that fundamental elements of the Andean metallurgical tradition were developed before the Chavin horizon, and that on the Peruvian coast the working of native copper preceded the production of smelted copper objects.

Quebrada jaguay: early south american maritime adaptations

Excavations at Quebrada Jaguay 280 (QJ-280) (16 degrees30'S) in south coastal Peru demonstrated that Paleoindian-age people of the Terminal Pleistocene (about 11,100 to 10,000 carbon-14 years before the present or about 13,000 to 11,000 calibrated years before the present) in South America relied on marine resources while resident on the coast, which extends the South American record of maritime exploitation by a millennium. This site supports recent evidence that Paleoindian-age people had diverse subsistence systems. The presence of obsidian at QJ-280 shows that the inhabitants had contact with the adjacent Andean highlands during the Terminal Pleistocene.

Early maritime economy and El Nino events at quebrada tacahuay, peru

The archaeological site of Quebrada Tacahuay, Peru, dates to 12,700 to 12,500 calibrated years before the present (10,770 to 10,530 carbon-14 years before the present). It contains some of the oldest evidence of maritime-based economic activity in the New World. Recovered materials include a hearth, lithic cutting tools and flakes, and abundant processed marine fauna, primarily seabirds and fish. Sediments below and above the occupation layer were probably generated by El Nino events, indicating that El Nino was active during the Pleistocene as well as during the early and middle Holocene.

History of atmospheric lead deposition since 12,370 (14)C yr BP from a peat bog, jura mountains, switzerland

A continuous record of atmospheric lead since 12,370 carbon-14 years before the present (14C yr BP) is preserved in a Swiss peat bog. Enhanced fluxes caused by climate changes reached their maxima 10, 590 (14)C yr BP (Younger Dryas) and 8230 (14)C yr BP. Soil erosion caused by forest clearing and agricultural tillage increased lead deposition after 5320 (14)C yr BP. Increasing lead/scandium and decreasing lead-206/lead-207 beginning 3000 (14)C yr BP indicate the beginning of lead pollution from mining and smelting, and anthropogenic sources have dominated lead emissions ever since. The greatest lead flux (15.7 milligrams per square meter per year in A.D. 1979) was 1570 times the natural, background value (0.01 milligram per square meter per year from 8030 to 5320 (14)C yr BP).

Black carbon in deep-Sea sediments

Black carbon (BC) enters the ocean through aerosol and river deposition. BC makes up 12 to 31 percent of the sedimentary organic carbon (SOC) at two deep ocean sites, and it is 2400 to 13,900 carbon-14 years older than non-BC SOC deposited concurrently. BC is likely older because it is stored in an intermediate reservoir before sedimentary deposition. Possible intermediate pools are oceanic dissolved organic carbon (DOC) and terrestrial soils. If DOC is the intermediate reservoir, then BC is 4 to 22 percent of the DOC pool. If soils are the intermediate reservoir, then the importance of riverine carbon in the ocean carbon cycle has been underestimated.

The Initial Domestication of Cucurbita pepo in the Americas 10,000 Years Ago

Squash seeds, peduncles, and fruit rind fragments from Archaic period stratigraphic zones of Guilá Naquitz cave in Oaxaca, Mexico, are assigned to Cucurbita pepo on the basis of diagnostic morphological characters and identified as representing a domesticated plant on the basis of increased seed length and peduncle diameter, as well as changes in fruit shape and color, in comparison to wild Cucurbita gourds. Nine accelerator mass spectrometer radiocarbon dates on these specimens document the cultivation of C. pepo by the inhabitants of Guilá Naquitz cave between 10,000 to 8000 calendar years ago (9000 to 7000 carbon-14 years before the present), which predates maize, beans, and other directly dated domesticates in the Americas by more than 4000 years.

Forcing of Atlantic Equatorial and Subpolar Millennial Cycles by Precession

Abundance cycles of the marine alga Florisphaera profunda centered on a period of 7600 carbon-14 years (8400 calendar years) are present in high-resolution records from the equatorial Atlantic spanning 0 to 45,000 years ago. These cycles correlate with Heinrich events 1 through 5, which document rapid changes in continental ice melting around the subpolar North Atlantic. These variations in F. profunda are a direct response to modulation in zonal wind-driven divergence produced by a precessional component of orbital variation during a time of reduced eccentricity modulation.

Climatic and Hydrologic Oscillations in the Owens Lake Basin and Adjacent Sierra Nevada, California

Oxygen isotope and total inorganic carbon values of cored sediments from the Owens Lake basin, California, indicate that Owens Lake overflowed most of the time between 52,500 and 12,500 carbon-14 ( 14 C) years before present (B.P.). Owens Lake desiccated during or after Heinrich event H1 and was hydrologically closed during Heinrich event H2. The magnetic susceptibility and organic carbon content of cored sediments indicate that about 19 Sierra Nevada glaciations occurred between 52,500 and 23,500 14 C years B.P. Most of the glacial advances were accompanied by decreases in the amount of discharge reaching Owens Lake. Comparison of the timing of glaciation with the lithic record of North Atlantic core V23-81 indicates that the number of mountain glacial cycles and the number of North Atlantic lithic events were about equal between 39,000 and 23,500 14 C years B.P.

A Revised Chronology for Mississippi River Subdeltas

Radiocarbon measurements by accelerator mass spectrometry relating to three of the four late Holocene Mississippi River subdeltas yielded consistent results and were found to differ by up to 2000 carbon-14 years from previously inferred ages. These geological data are in agreement with archaeological carbon-14 data and stratigraphic ages based on ceramic seriation and were used to develop a revised chronologic framework, which has implications for prehistoric human settlement patterns, coastal evolution and wetland loss, and sequence-stratigraphic interpretations.

Late Pleistocene Desiccation of Lake Victoria and Rapid Evolution of Cichlid Fishes

Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochromine cichlid fish. Seismic reflection profiles and piston cores show that the lake not only was at a low stand but dried up completely during the Late Pleistocene, before 12,400 carbon-14 years before the present. These results imply that the rate of speciation of cichlid fish in this tropical lake has been extremely rapid.

Interhemispheric Correlation of Late Pleistocene Glacial Events

A radiocarbon chronology shows that piedmont glacier lobes in the Chilean Andes achieved maxima during the last glaciation at 13,900 to 14,890, 21,000, 23,060, 26,940, 29,600, and >/=33,500 carbon-14 years before present ((14)C yr B.P.) in a cold and wet Subantarctic Parkland environment. The last glaciation ended with massive collapse of ice lobes close to 14,000(14)C yr B.P., accompanied by an influx of North Patagonian Rain Forest species. In the Southern Alps of New Zealand, additional glacial maxima are registered at 17,720(14)C yr B.P., and at the beginning of the Younger Dryas at 11,050 (14)C yr B. P. These glacial maxima in mid-latitude mountains rimming the South Pacific were coeval with ice-rafting pulses in the North Atlantic Ocean. Furthermore, the last termination began suddenly and simultaneously in both polar hemispheres before the resumption of the modern mode of deep-water production in the Nordic Seas. Such interhemispheric coupling implies a global atmospheric signal rather than regional climatic changes caused by North Atlantic thermohaline switches or Laurentide ice surges.

Detection of Large Prehistoric Earthquakes in the Pacific Northwest by Microfossil Analysis

Geologic and palynological evidence for rapid sea level change approximately 3400 and approximately 2000 carbon-14 years ago (3600 and 1900 calendar years ago) has been found at sites up to 110 kilometers apart in southwestern British Columbia. Submergence on southern Vancouver Island and slight emergence on the mainland during the older event are consistent with a great (magnitude M >/= 8) earthquake on the Cascadia subduction zone. The younger event is characterized by submergence throughout the region and may also record a plate-boundary earthquake or a very large crustal or intraplate earthquake. Microfossil analysis can detect small amounts of coseismic uplift and subsidence that leave little or no lithostratigraphic signature.

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.

Early Deglaciation of the Labrador Shelf

Two marine sediment cores from a basin on the southeastern Labrador Shelf penetrate a mud sequence extending back to 21,000 carbon-14 years before the present (B.P.). The benthic foraminifera are dominated by subartic nearshore species indicative of ice-free summer waters. The pollen record indicates the presence of a sedge-shrub tundra in eastern Labrador as early as 21,000 years B.P. Both sources of evidence suggest less extensive continental ice than has previously been reported for this subarctic region.