We report preliminary results of a long-term systematic study intended to gather paleoclimatic records from precisely dated speleothems. The research project is limited to speleothems deposited in caves of the Cracow-Wieluń Upland, the largest and best-explored karst region in Poland, covering ca. 2900 km2 with >1000 caves. Speleothem samples were selected from collections of the Geological Museum of the Academy of Mining and Metallurgy in Cracow. Radiocarbon dates of these samples from ca. 45–20 ka bp almost exactly coincide with age range of the Interplenivistulian. A break in speleothem formation between ca. 20 and 10 ka bp may be interpreted as a result of serious climatic deterioration associated with the maximum extent of the last glaciation. We observed differences among 14C, U/Th and AAR dating results. Changes of δ13C and δ18O in speleothems that grew between ca. 30 and 20 ka bp may be interpreted as changes of paleoclimatic conditions.

Paleokarst forms in raised beach deposits of Southwest England and South Wales and generally known as “pipes” were dated by 14C and thermoluminescence (TL) methods. Current geological opinion is that these pipes are features that developed under the cover of periglacial-solifluctional deposits due to periglacial conditions prevalent in the Late Devensian. In the present study, TL was used to determine the age of quartz grains forming the raised beaches. 14C ages were obtained from carbonate cements within sandrock and on the pipe walls. TL ages measured for quartz grains separated from sandrock samples are older than 80 ka bp, whereas the corresponding TL dates obtained from the sandy material of pipe infills center around 40 ka bp. All carbonates yielded finite apparent 14C dates that range from ca. 45 ka bp to 27 ka bp for sandrock. The apparent 14C dates obtained on carbonate cements from the pipe walls fall into two groups, one ranging from 30 ka bp to 22 ka bp and the other from 15 ka bp to 7 ka bp. On the basis of geochemical considerations, we conclude that the sandrock cements formed between 35 and 25 ka bp and pipe walls cemented between 30 and 2 ka bp with a break during the climate deterioration caused by last ice sheet advance.

An important recent development in the field of geomorphology has been the application of in-situ cosmic-ray-produced nuclides to obtain model erosion rates and surface exposure ages. These concepts emerged some four decades ago in studies of cosmogenic nuclides in meteorites, but cannot generally be used analogously for terrestrial rocks. The differences in the two cases are outlined. For the case of steady-state erosional histories, the terrestrial surface exposure ages depend on the half-life of the radionuclide studied. A suggestion is made for presenting the surface exposure ages, which allows a clear definition of the meaning of the estimated exposure ages. In the case of a discrete exposure history, the meaning of “exposure age”—which should more appropriately be called “event age”—is however quite unambiguous.

High-precision measurements were completed concurrently at the University of Arizona and the Queen's University of Belfast on blind samples of Irish oak originally measured for the 1986 radiocarbon calibration curve. Subsequent single-year Sequoiadendron results were decadally averaged and compared with published results on decadal Douglas-fir samples. The results of these intercomparisons show that the Arizona high-precision results compare favorably with published values from the University of Washington, but show a systematic offset with published Belfast data.

We present the results of the 14CO2 atmospheric monitoring station at the Smilde observation station, near Groningen, the Netherlands, a typical continental station. We compared these data, for absolute values and annual variation, with data from Fruholmen, Nordkapp, Norway and Izaña, Tenerife, Canary Islands, which are situated in areas less influenced by fossil-fuel CO2. The 20-yr Smilde record shows much seasonal variation (peak-to-trough variation is ∼30‰ in contrast to ∼12‰ for Fruholmen, and ∼5‰ for Izaña) and a lower overall value due to fossil-fuel consumption, in accordance with findings from similar stations in continental Western Europe. The Fruholmen and Izaña data show fairly equal mean Δ14C levels, but differ in seasonal amplitude. This difference could be due partly to the elevation difference between the stations. The Izaña station also has a slow exchange with the ground-level air because of an inversion layer. It is speculative whether annual injection of 14C from the stratosphere also plays a role. We give the Groningen long record of tritium in precipitation, showing profound seasonality.

We present pollen diagrams and sedimentological analyses from a lake site within an extensive dune system on the Aupouri Peninsula, Northland. Five thousand years ago, a regional Agathis australis–podocarp-broadleaf forest dominated the vegetation, which manifested an increasing preponderance of conifer species. Climate was cooler and drier than at present. From ca. 3400 bp, warmth-loving species such as A. australis and drought-intolerant species, Dacrydium cupressinum and Ascarina lucida, became common, implying a warm and moist climate. The pollen record also suggests a windier climate. The most significant event in the record, however, occurred after ca. 900 bp (800 cal bp) when anthropogenic deforestation commenced. A dramatic decline in forest taxa followed, accompanied by the establishment of a Pteridium–esculentum-dominated community. Fire almost certainly caused this, evidenced by a dramatic increase of charcoal. Sedimentological evidence for this site indicates a relatively stable environment before humans arrived and an increasingly unstable environment with frequent erosional events after human contact.

We report on 69 radiocarbon dates of mollusk shells and benthic foraminifera from the upper 132 m of the marine shelf sediments of the Skagen Core (220 m total length). The dated sequence covers the Late Glacial and the Holocene (from 15 ka bp to Recent). Sedimentation rates range from 1 to 70 m ka−1. The macrofossil shell dates follow a smooth curve constituting an age model for dating the sediments. The foraminiferal dates fall into two groups: those that agree exactly with the mollusk shells and those that deviate substantially, always being older than the shells by as much as 5 ka. One mixed foraminiferal sample consisted of members from both groups, and as a result, the age deviation of the sample turned out to be some weighted average. The data indicate that the age deviations are due to admixtures of reworked older foraminifera.

Increased marine 14C reservoir ages from the surface water of the North Atlantic are documented for the Younger Dryas period. We use terrestrial and marine AMS 14C dates from the time of deposition of the Icelandic Vedde Ash to examine the marine 14C reservoir age. This changed from its modem North Atlantic value of ca. 400 yr to ca. 700 yr during the Younger Dryas climatic event. The increased marine reservoir age has implications for both comparing climatic time series dated by 14C and understanding palaeoceanographic changes that generated the increase.

We studied the structure and development of the Holocene floodplain of the Labe (Elbe) River by radiocarbon dating sections of the upper and middle courses of the river. We focused on geomorphological and sedimentological conditions, mineralogy and the chemical composition of sediments. We established the stratigraphy of the Holocene deposits of the floodplain. The results of our investigation of fluvial sediments imply that several abrupt changes in temperature and precipitation occurred during the Holocene. These changes led to intervals of hydrological disequilibrium, which caused the formation of two Holocene terraces and a contemporaneous floodplain. The lower terrace was flooded and covered with sediments upon which the recent floodplain formed. During the Holocene, there were four periods during which large tree trunks were deposited in the fluvial sediments, indicating periods of extensive flooding. The supposition that these events were of more global scale is supported by the results of investigations made on the Holocene floodplains of other regions.

I discuss a suite of 29 radiocarbon age determinations from four valleys on the islands of Mo'orea and Raiatea in the Society Archipelago. These dates provide the first sequence for the development of prehistoric agricultural production and human-induced environmental change in the Society Islands. Indirect evidence of small-scale agriculture, and by association, human occupation, dates to at least the 7th–10th centuries ad. Agricultural sites themselves date from the early 13th century ad until the late prehistoric/early historic period, with most agricultural activity clustering at the end of the temporal sequence. Valleys with the greatest arable potential were cultivated earlier than less preferred sites. Evidence for extensive landscape transformation in the Opunohu Valley, likely associated with clearing for agricultural purposes, begins soon after the earliest evidence for cultivation and continues throughout prehistory. A larger sample of 14C determinations from strati-graphic excavations in both archaeological sites and “off-site” contexts is required to address many as yet unanswered questions about the prehistoric social and economic development of the Society Islands.

Determined independently from annually laminated ice cores and lake sediments, and German pines, the calendar ages of Younger Dryas (YD) boundaries significantly disagree with one another. 14C dates, plotted vs. calendar ages for samples from different sediments, also reveal distinct offsets. The adjustment of varve chronologies to synchronize the boundaries of the YD nearly cancels the discrepancies between 14C data, and supports the synchronism of the YD cold period over the North Atlantic region. However, the exact timing of the event cannot be estimated in this way.

Recent fieldwork on the island of Faial (Azores) led to the establishment of a detailed volcanic stratigraphic sequence, which is composed of five main geological formations. One of them, the Caldeira Formation, comprising mainly pumice fall and flow deposits, was judged to be Holocene in age. Organic materials were found preserved in or below some of the pyroclastic deposits from this formation. Wood, charcoal, peat and soil samples were radiocarbon dated, permitting correlation of deposits from different sequences and the establishment of a chronological framework for the Caldeira volcanic activity. These materials yielded ages from ca. 10–1 ka bp. The average dormant interval in the Caldeira pyroclastic activity from 4–1 ka ago is ca. 400 yr, with eruptions approximately every 200–800 yr. This frequency of activity indicates that the Caldeira volcano is an active, dangerous structure that should be closely monitored.

In 373 bc a catastrophic earthquake and seismic sea wave destroyed Helike, a Greek city near Aigion on the southern shore of the Gulf of Corinth. The ruins were buried by sediments of unknown depth, leaving no trace of the city. We here discuss the radiocarbon dating of organic sediment samples recovered from seven boreholes drilled on the coastal plain in the area where ancient sources located Helike. Most of the samples apparently acquired a substantial addition of older carbon from natural sources, and hence their apparent ages are older than the true ages of sedimentation. However, if we assume that the addition is systematic, we can use the apparent ages to show that the sedimentation rate was initially rapid (about 1 cm yr-1) for the strata between 40 and 10 m below the surface, and then decreased by an order of magnitude about 6500 yr ago. A related change in the sediment deposition at about the same time has been found in many other marine deltas throughout the world, probably due to the deceleration of the global sea-level rise. We conclude that in the boreholes sampled by the present data, the horizon corresponding to ancient Helike is less than 8 m deep.

Terrestrial macrofossils selected from laminated sediment of Lake Gościąż were dated by AMS. Thus, part of the floating varve chronology (FVC) (Goslar et al. 1993) between radiocarbon ages of 4225 ± 45 and 7740 ± 85 bp can be compared and placed on the 14C calibration curve. As a result of our dating, the top of the FVC is now dated between 3120 and 3300 cal bp, i.e., 3210 ± 90 cal bp.

The Laacher Sec Tephra (LST) layer provides a unique and invaluable time marker in European sediments with increasing importance because it occurs just before the onset of the Younger Dryas (YD) cold event. As the YD begins ca. 200 calendar years after the LST was deposited, accurate determination of the radiocarbon age of this ash layer will lead to a more accurate age assignment for the beginning of the YD. On the basis of 12 terrestrial plant macrofossil 14C ages derived from sediments from Soppensee, Holzmaar and Schlakenmehrener Maar, we found an age of at least 11,230 ± 40 bp for the LST event. This is ca. 200 yr older than the often reported age of 11,000 ± 50 bp (van den Bogaard and Schmincke 1985).

More than 1000 authentic samples of ethanols were extracted by quantitative distillation from vintage wines and brandies prepared from grapes harvested in well-defined regions and years. The 13C contents of these ethanols were determined by isotope ratio mass spectrometry (IRMS) and the 14C activity of most of these samples was determined by liquid scintillation counting (LSC). We show that the 13C content of a C3 plant such as grape vine, which strongly depends on water availability, spans nearly a 10% range worldwide. The efficiency of the 14C content of grape ethanols as a tracer of the CO2 turnover after the peak of the nuclear test in the 1960s is also discussed in terms of geographical effects. Finally, the necessity of a multi-isotopic approach, including 13C and 14C isotopes, for detecting sophisticated adulterations is illustrated in the case of wines and brandies.

Although a coauthor of the paper of Kahn et al. (1995), I was not available in time to review the final copy. Consequently, I take this opportunity to make further comments and, hopefully, clarify some of the content and conclusions.

Tree rings from a section of Prumnopitys taxifolia (matai) covering the period ad 1335–1745 have been radiocarbon dated and used to generate a 14C calibration curve for southern hemisphere wood. Comparison of this curve with calibration data for northern hemisphere wood does not show a systematic difference between 14C ages measured in the northern and southern hemispheres. A floating chronology covering 270 yr and terminating at the last Taupo (New Zealand) eruption, derived from a sequence of 10-yr samples of tree rings from Phyllocladus trichomanoides (celery pine, or tanekaha), is also consistent with the absence of a systematic north-south difference, and together with the matai data, fixes the date of the Taupo eruption at ad 232 ± 15.

Radiocarbon dating of varved lake sediments shows that, during the Late Glacial (10–12 kyr bp), the offset between the 14C and the absolute time scales was ca. 1 kyr. Varve counting and accelerator mass spectrometry (AMS) dating were used to build absolute and 14C time scales of sediments from two lakes—Soppensee, Switzerland and Holzmaar, Germany. The resulting chronologies extend back to ca. 12.9 kyr cal bp (12.1 kyr bp) in the case of Soppensee and to ca. 13.8 kyr cal BP (12.6 kyr bp) in the Holzmaar record. They compare well with each other but differ significantly from the 14C-U/Th chronology of corals (Bard et al. 1993; Edwards et al. 1993).

We use a dry extraction method to obtain trapped CO2 of shallow ice cores from a blue ice area of East Antarctica. In-situ-produced 14C extracted in 14CO2 and 14CO concentrations show a mean ratio of 3.4 ± 0.4. Correction for in-situ14CO2 resulted in ice ages within 7–13 ka. The accumulation and ablation rates determined from the in-situ production of 7–20 cm yr−1 and 10–13 cm yr−1, respectively, agree with field measurements, and thus indicate close to total efficiency of extraction.