Marine records from the Reykjanes Ridge indicate ice sheet variations and abrupt climate changes. One of these records, ice-rafted detritus (IRD), serves as a proxy for iceberg discharges that probably indicates ice sheet fluctuations. The IRD records suggest that iceberg discharge 68,000–10,000 yr B.P. happened more frequently than the 7000- to 10,000-yr spacing of the Heinrich events. An IRD peak 67,000 to 63,000 yr B.P. further suggests that the Middle Weichselian glaciation started about 12,000 yr earlier in the North Atlantic than in the Norwegian Sea. Several later IRD events, in contrast, correlate with Norwegian Sea IRD-rich layers and imply coeval ice sheet advances in the North Atlantic and the Norwegian Sea. Coccoliths in a core from the Reykjanes Ridge show distinct peaks in species that record occasional inflow of warm surface water during the last glaciation, as previously reported from the eastern Labrador Sea. High abundances of coccoliths, together with a decrease of Neogloboquadrina pachyderma sin. and relatively low δ18O values, imply enhanced advection of the North Atlantic Current 69,000–67,000 yr B.P., 56,000–54,000 yr B.P., 35,000–33,000 yr B.P., and 26,000–23,000 yr B.P. This advection provided a regional moisture source for extension of ice sheets onto the shelf. In contrast, most of the IRD events are characterized by cold polar surface water masses indicating rapid variations in ocean surface conditions.

Paleotemperatures for the last glacial maximum (LGM) have been derived from noble gases dissolved in 14C-dated groundwater of the Ojo Alamo and the Nacimiento formations in the San Juan Basin, northwestern New Mexico. The difference in mean annual (ground) temperature between the Holocene and the LGM was determined to be 5.5 ± 0.7°C. A practically identical result, 5.2 ± 0.7°C, has been obtained previously from the Carrizo aquifer in southern Texas. This suggests that the southwestern United States was uniformly cooler during the LGM and that the mean annual temperature gradient along a transect from the Gulf of Mexico to northwestern New Mexico has been unchanged since the LGM. The noble gas paleotemperatures are supported by paleoecological evidence in the region. The Holocene/LGM temperature difference of 5.4°C indicates that a simple lapse rate calculation may be applied to convert the 1000-m glacial depression of snowlines in the Colorado Front Range into a temperature decrease. A continental temperature change of 5.4 ± 0.7°C is inconsistent with a temperature change of about 2°C determined for the surface waters of the Gulf of Mexico.

Variability of atmospheric 14C content often complicates radiocarbon-based chronologies; however, specific features such as periods of constant 14C age or steep changes in radiocarbon ages can be useful stratigraphic markers. The Younger Dryas event in the Northern Hemisphere is one of those periods, showing conspicuous 14C wiggles. Although the origin of those variations is not fully understood, we can make practical use of them and determine: (i) whether the Younger Dryas was global in extent; if so, (ii) were the initial cooling and the final warming synchronous worldwide; and (iii) what are the implications of these similarities/differences? Here we report high-resolution AMS 14C chronologies from the mid-latitudes of South America that pinpoint a cool episode between 11,400 and 10,20014C yr B.P. The onset of the final cool episode of the Late Glacial in the southern mid-latitudes, i.e., the Huelmo/Mascardi Cold Reversal, preceded the onset of the Younger Dryas cold event by ∼550 calendar years. Both events ended during a radiocarbon-age plateau at ∼10,20014C yr B.P. Thus, the Huelmo/Mascardi Cold Reversal encompasses the Younger Dryas, as well as a couple of short-term cool/warm oscillations that immediately preceded its onset in the North Atlantic region.

The pattern of climate change in the Southern Hemisphere during the Younger Dryas (YD) chronozone provides essential constraint on mechanisms of abrupt climate change only if accurate, high-precision chronologies are obtained. A climate reversal reported previously at Kaipo bog, New Zealand, had been dated between 13,600 and 12,600 cal yr B.P. and appeared to asynchronously overlap the YD chron, but the chronology, based on conventionally radiocarbon-dated bulk sediment samples, left the precise timing questionable. We report a new high-resolution AMS 14C chronology for the Kaipo record that confirms the original chronology and provides further evidence for a mid-latitude Southern Ocean cooling event dated between 13,800 and 12,400 cal yr B.P. (2σ range), roughly equivalent to the Antarctic Cold Reversal.

Sharp jumps in climate punctuate the records from borings in the Greenland ice cap during the time interval 60,000 to about 20,000 yr ago. Rapid fluctuations are also seen in foraminifera records for cores from the northern Atlantic and in a pollen record from a core from a bog in the Vosges Mountains in France. In this paper we present a new radiocarbon chronology for northern Atlantic deep-sea core V23-81 which permits comparison with the radiocarbon-dated Vosges Mountains pollen record. Because of the lack of a 14C chronology for the Greenland ice record and of distortions peculiar to each of the three records, it is not yet possible to say whether or not the events are genetically related.

Multiple stratigraphies of subtropical South Atlantic cores reveal significant stratigraphic discrepancies between the nannofossil and the foraminiferal carbonates. Variations in the stratigraphic signals carried in the nannofossil-dominated <38 μm fraction and foraminifera-dominated >38 μm fraction were measured with detailed stratigraphies of δ18O, δ13C, 14C, grain size, percentage carbonate, percentage aragonite, and taxonomic composition across the last deglaciation in INMD box core 111 No. 9. Three other cores (INMD box cores 113 and 115, and V 22–174), also from the shallow flanks of the mid-Atlantic ridge in the South Atlantic (10°–17° S), contain similar stratigraphies indicating that these cores represent regional patterns. The onset of the deglacial δ18O shift in foraminiferal carbonate occurs 6 to 20 cm deeper than the δ18O shift in the nannofossil fraction. Nineteen accelerator mass spectrometer 14C dates of various fractions (<38 μm, 38–62 μm, 62–150 μm, 150–250 μm, >355 μm, and G. ruber) from INMD Box 111 show that the components within an individual core slice may differ by up to 4900 14C years. Twelve traditional 14C dates (determined by beta counting) of the >38 and <38 μm fractions from six levels in INMD Box 111 No. 6 confirm the large offsets. The observed isotopic offsets are not explained by an individual process, and suggest that multiple causes have left a lumpy stratigraphic record. However, the variability in the data illustrates the difficulty in accurately measuring the chronology of deglaciation, reopens the question of which components of pelagic sediment best monitor surface water conditions, and complicates the direct interpretation of benthic-planktonic age differences in terms of ocean ventilation changes.

U-Th isochron ages of tufas formed on shorelines suggest that the last pluvial event in Lake Lahontan and Searles Lake was synchronous at about 16,500 cal yr B.P. (equivalent to a radiocarbon age of between 14,000 and 13,500 yr B.P.), whereas the timing of this pluvial event determined by radiocarbon dating is on the order of 1000 yr younger. The timing of seven distinct periods of near desiccation in Searles Lake during late-glacial time has been reinvestigated for U-Th age determination by mass spectrometry. U-Th dating of evaporite layers in the interbedded mud and salt unit called the Lower Salt in Searles Lake was hampered by the uncertainty in assessing the initial 230Th/232Th of the samples. The resulting ages, corrected by a conservative range of initial 230Th/232Th ratios, suggest close correlation of the abrupt changes recorded in Greenland ice cores (Dansgaard-Oeschger events) and wet–dry conditions in Searles Lake between 35,000 and 24,000 cal yr B.P.

Natural textiles provide suitable material for radiocarbon dating. Short-lived organic matter is usually involved and, if 14C dating is applied to pieces that are stylistically well dated, a better understanding of 14C dating of this type of material can be gained. This study presents some examples of dating that support the stylistic dates. Repeated analyses illustrate the robustness of the standard treatment applied to the textiles.

The remains of Vindonissa, the Roman legionary camp in Switzerland, have been the subject of extensive archaeological studies. Knowledge of the building time plays a role in reconstructions of the history of this site. We radiocarbon dated mortar samples selected from one of the Roman monuments (Westtor) as well as a nearby Medieval monastery. 14C ages obtained on the first fraction and second fraction of very short dissolution appear close to the expected Roman age of ∼2000 BP, while the monastery is dated to historic times, after AD 1308.

A detailed radiocarbon chronology has been established for the deep-sea core CT85-5 from the Tyrrhenian Sea. This chronology, which is based on the analysis of foraminifera shells, shows a set of reversed 14C ages for sediments deposited during the eruption of the Campanian Ignimbrite (∼40 ka cal BP). The anomalous young 14C ages coincide with elevated concentrations of 10Bc measured in the same core. Although reversals in 14C ages have been previously found in other records at 40 ka cal BP, such extreme changes have not been observed elsewhere. The enhancement in 14C concentration in CT85-5 sediments associated with the Campanian Ignimbrite is equivalent to an apparent age ∼15 ka younger than the age for the sediments deposited shortly before the eruption. Here, we present consistent results of repeated measurements showing no analytical problems that can explain the observed rapid changes in 14C of this particular record.

Understanding of processes that determined the expansion of farming and animal husbandry in south-western Europe is hampered by poor chronologies of the early Neolithic in this region. This paper presents new radiocarbon dates, which are used to construct such a chronological frame for a regional group of the most important culture of the early Neolithic in the western Mediterranean: the Cardial culture.

Preparation of bone material for radiocarbon dating is still a subject of investigation. In the past, the most problematic ages appeared to be the very old bones, i.e. those with ages close to the limit of the dating method. Development of preparative methods requires sufficient amounts of bone material as well as the possibility of verification of the ages. In the peat section at Niederweningen, ZH Switzerland, numerous bones of mammoth and other animals were found in the late 19th century. The first accelerator mass spectrometry (AMS) radiocarbon ages of those bones from 1890/1891 excavations placed the age between 33,000 and 35,000 BP. The excavations in 2003/2004 provided additional material for 14C dating. An age of 45,870 ± 1080 BP was obtained on base (NaOH step) cleaned gelatin from mammoth bone, which was very close to the age of 45,430 ± 1020 BP obtained for the peat layer that buried the mammoths. The 14C age of gelatin cleaned using the ultrafiltration method obtained in this study, 45,720 ± 710 BP, is in a very good agreement with the previously obtained results. Moreover, the study shows that 3 pretreatment methods (base+Longin, Longin+ultrafiltration, and base+Longin+ultrafiltration) give ages consistent with each other and with the age of the peat section.

Two independent 14C data sets of 10 tree-ring samples from the longest master chronology of the Pazyryk cultural complex were obtained and wiggle-matched to the absolute timescale. The results show very good agreement, within 10–15 calendar yr. The Ulandryk-4 burial ground (mound 1) was dated to about 320–310 cal BC, and this is consistent with wiggle-matching of the Pazyryk burial ground date series.

Progressive dissolution experiments were performed on samples of ostracode shells from lacustrine sediments from the western Great Basin to remove contamination of the surface by secondary calcite. The observed age differences between the external and residual fractions were as great as 2000 to 6000 yr. A “plateau” in ages of the last fractions was obtained only for 1 sample; however, results of repeated experiments resulted in very good agreement of the final ages. A comparison with previously published chronologies based on bulk radiocarbon ages of ostracodes from Wilson Creek (Benson et al. 1990) shows that leaching is imperative for dating samples older than 20 ka B P. This study focuses on the problem of contamination and its removal. However, the final chronology of the Wilson Creek Formation (and other late Pleistocene lacustrine sediments) will require additional dating of other sections as well as establishment of a reservoir effect correction.

Between 1984 and 1995 over 450 organic samples were collected from monuments built during the Old and Middle Kingdoms. The most suitable samples were selected for dating. The purpose was to establish a radiocarbon chronology with samples from secure context and collected with the careful techniques required for 14C samples. This chronology is compared to the historical chronology established by reconstructing written documentation.

During the last decade, several radiocarbon-dated varve chronologies have been produced. The main goal at first was the extension of the 14C calibration curve beyond 10,000 BP. This paper aims to discuss varve chronologies of Soppensee and Holzmaar Lakes. Although both chronologies encountered problems, high-resolution 14C dating and relative varve time have been obtained for events during the Late Glacial.

Accurate radiocarbon ages were obtained from terrestrial moss from two drill holes in Tern Lake deposits, Antarctica, using liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS). The results show that the lake deposits have been accumulating since the end of the last glacial epoch ca. 12,600 cal BP at the rate of 0.13–1.1 mm a-1. We discuss the validity of 14C ages of Antarctic lake deposits, with respect to the latitude effect of 14C productivity, the reservoir effect, the environment effect and the hard-water effect.

Lago Grande di Monticchio (Italy) contains long sedimentary records of >75 ka (Zolitschka and Negendank 1996). In a joint European project (Creer and Thouveny 1996), vegetation history and climatic changes for this part of the Mediterranean have been reconstructed (Watts, Allen and Huntley 1996; Watts et al. 1996). In addition to the time scale based on annual laminations and sedimentation rate, tephra layers and pollen spectra, radiocarbon dating was applied for the last 40 ka. Previous studies have shown that the age of bulk sediment from Lago Grande di Monticchio, which is a maar lake at the flanks of Mt. Vulture, was influenced by “dead carbon” of volcanic origin dissolved in the lake water. Thus, 14C dating of the record is problematic and must be limited to dating macrofossils of terrestrial origin.

From a set of sediment samples, macrofossils were selected and dated using accelerator mass spectrometry (AMS). A 14C time scale based on seven data points between 9000 and 24,000 bp is compared with other dating of the record based on varve counting and tephrochronology (Zolitschka 1996).

The distribution of bomb-produced 14C in the ocean provides a powerful constraint for circulation models of upper ocean mixing. We report 14C measurements from an east-west section of the main thermocline at 24°N latitude in the subtropical North Atlantic Ocean in summer 1992, and one profile from the Gulf of Mexico in 1993. Observed gradients reflect the transient invasion of bomb 14C into the thermocline via mixing along isopycnals from the poleward outcrop, with progressively more sluggish mixing at greater depths. A slight deepening of the profile is observed over the 20-yr period since the GEOSECS survey at one location where the comparison is possible.