Calcareous tufa from five sites in southern Poland, representing several most typical conditions of tufa sedimentation, were chosen for 14C, 13C, and 18O measurements. These tufas were deposited in a high-energy turbulent stream (the Racławka site), in streams with moderate but variable flow (Rzerzuśnia and Trzebienice), and in semilimnic conditions (Sieradowice site). Sediments of the Gliczarów site represent spring travertines. In all but the latter site, direct comparison of 14C dates of carbonate and organic fractions was possible, leading to an estimate of initial apparent age of carbonate sediments. Clear correlation was found between the value of initial apparent age of tufas and the hydrodynamic conditions of sedimentation. Corresponding values range from ca 3900 yr (Racławka) to 910 yr for semilimnic sediments (Sieradowice). Intermediate, almost identical values, equal to 2460 ± 200 yr and 2100 ± 160 yr, were obtained for tufas from Rzerzuśnia and Trzebienice, respectively. Detailed sedimentologic classification of tufaceous deposits is presented and some primary and secondary factors affecting the accuracy of radiocarbon dates of various types of tufas are also discussed.

Evergreen trees in the tropical rain forest of the Amazonas Basin can produce growth rings which are not necessarily related to annual events. Therefore, estimation of growth rate cannot be done by dendrochronology. This report presents a technique for determining the growth rate of these trees based on radiocarbon measurements of two segments of equal radial distance from the outer part of the tree trunk. The measured 14C activity is compared to local 14C fallout and growth rates are derived from models taking into account bomb 14C effects. Eleven trees from various parts of the Amazon Basin were analyzed. The average growth rates range from ca 5 to > 40 yr per centimeter corresponding to extrapolated ages from ca 60 to > 400 yr.

The study of this core was carried out cooperatively with Bill Curry of Woods Hole Oceanographic. Our goal was to obtain benthic-planktonic age difference for the glacial section of the core (see Figs 1, 2, Table 1).

This paper presents a synthetic approach to 14C dating of calcareous tufa, based on statistical analysis of correlations betwen lithologic type of tufaceous sediment, carbon isotope composition, and apparent age. Experimental data on several profiles from southern Poland and the United Kingdom reveal either constant or systematically changing values of apparent age. Constant value of apparent age in a profile can be attributed to calcareous muds precipitated from stagnant or low-energy water, and to tufas precipitated from turbulent water (oncoids, stromatolites, moss travertines) which are characterized by lack of significant correlation between δ 13C and 14C age of tufa carbonate. It was found that the relation between the apparent age of tufaceous sediment and δ 13C value of tufa carbonate depends on lithologic type of tufa. Phenomenological equations describing the dependence of apparent age upon δ 13C are given, and applied to estimate true ages of tufas from Gliczarów (southern Poland) and Folkestone (United Kingdom).

Small sample 14C dating is tested using conventional as well as high-resolution low-level liquid scintillation (LS) spectrometers. Contrasted are the results obtained dating ∼25, 125 and 250mg of elemental carbon in standard size counting vials (3mL) and 0.3mL teflon and quartz vials. It is demonstrated that the improved performance of the 0.3mL counting vials enables just adequate resolution of 25mg and very good resolution of 100mg carbon samples both at Modern and Old age limits when the determination is made in a high-resolution low-level LS spectrometer.

A method is given for modifying the estimated radiocarbon dates of two samples when they are known to be in the wrong order.

Study of the dependence of core top ages for G menardi and G sacculifer on water depth in cores of low sedimentation rate (∼2cm/103 yr). The study was initiated by Lisa Dubois of Brown University on cores originally studied by Curry and Lohmann of Woods Hole Oceanographic (see Table 2).

Traces of uranium and radium within the 14C sample generate radon (Rn) which gets occluded during the benzene synthesis, thus generating false (extra) counts within the 14C counting window. This, if undetected, gives rise to erroneous 14C age determinations. The application of simultaneous α and β liquid scintillation spectrometry will enable a mathematical evaluation of the 14C signal unaffected by α and β particle emissions from radon decay daughters.

Three decades of archaeological excavations in Melanesia and Western Polynesia have led to a consensus among Oceanic prehistorians that the initial human colonization of the southwestern Pacific (east of the Solomons) was effected by populations of the Lapita Cultural Complex (Green, 1979; Kirch, 1982, 1984; Allen, 1984; Spriggs, 1984). Although the western Melanesian islands of New Guinea, the Bismarck Archipelago, and possibly the Solomon Islands were settled in the late Pleistocene by small hunter-gatherer populations (Downie & White, 1979; Specht, Lilley & Normu, 1981; Groube et al, 1986), discovery and occupation by humans of the more remote island chains to the east required sophisticated voyaging and colonization strategies. That the Austronesian-speaking Lapita people possessed long-distance voyaging craft is suggested both by lexical reconstructions, and by the archaeological evidence of long-distance transport of obsidian and other exotic materials over distances of up to 3700km (Ambrose & Green, 1972; Best, 1987). Lapita sites are marked by a distinctive complex of dentate-stamped earthenware ceramics, and associated shell, bone, and stone artifacts. Sites yielding such assemblages have been recorded between the Bismarck Archipelago in the west, through Melanesia, and as far east as Samoa and Tonga, a straight-line distance of ca 4500km.

Since 1984, a large multi-disciplinary archaeological team, under the direction of the author, has collected artifactual, ecofactual, and radiocarbon samples from a series of Native American sites spanning the past 9600 14C years. Occupied historically by the Chumash Indians, the Santa Barbara coast (Fig 1) has seen dramatic cultural and environmental change during the course of the Holocene. One of the goals of the research is to reconstruct patterns in the evolution of the local coastline, while examining the effects of environmental change on human adaptation along the Santa Barbara coast.

The study of these whole shell, shell fragment pairs from trigger weight cores from the western equatorial Atlantic was initiated by Alan Mix (see Table 3).

The study of this northern Atlantic core was undertaken to establish the chronology of surface water temperature changes in the northern Atlantic from 40,000 years ago to present (see Figs 3, 4; Table 4).

A re-evaluation of the Longin collagen-extraction method shows that a lower reflux temperature reduces degradation of protein (“collagen”) remnants. This allows additional purification through ultrafiltration to isolate the >30kDalton fraction of the reflux product.

This list contains the results of measurements of 172 radiocarbon samples made between January 1983 and December 1985. An additional 152 samples were measured, but these were submitted without detailed information, such as sample location and sampling depth; therefore, they were excluded from the list.

This list is part of a program of publishing our large backlog of unpublished dates. The dates listed here, from 1974 to 1979, include archaeologic samples from various cultures and countries and geologic samples related to sea-level variations, volcanism, and especially the history of paleolakes in Africa.

The study of this core was undertaken to measure the benthic-planktonic age difference for the “Boyle water” of glacial time in the Caribbean Sea (see Figs 5,6; Table 5).

Most of the 14C measurements reported here were made between October 1986 and June 1987. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36–37; 1976, v 18, p 290; 1986, v 28, no. 3, p 1111).

This list continues our program to put into print our large backlog of unpublished dates. Those listed here are not a specific block of dates but simply those ready for publication.

The study of this core was undertaken in cooperation with James Kennett. The purpose was to establish the chronology of the Mississippi River melt water record (see Figs 7,8; Table 6).