Radiocarbon Age Determinations Research Articles

A Middle Weichselian interstadial lake deposit on Sejerø, Denmark: macrofossil studies and dating

AbstractStudies of lake sediments on Sejerø in southern Kattegat indicate a treeless arctic environment with the dwarf shrub Salix polaris, herbs and wetland mosses. The mean July temperature was around 8 to 10°C. An AMS radiocarbon age determination of a Salix twig yielded an age of around 36 000 14C yr BP, which is in accordance with previous conventional dating of bulk sediment samples. Copyright © 2006 John Wiley & Sons, Ltd.

Holocene aeolian morphogenetic phases in Southern Italy: Problems in 14C age determinations using terrestrial gastropods

Radiocarbon age determination is one of the most important methods for dating Holocene events. In particular, it has been used to reconstruct the sequence of aeolian morphogenetic phases along the Apulia and Basilicata coasts (Southern Italy). In these areas, three main Holocene morphogenetic phases have been recognized using radiocarbon data obtained from sub-fossil terrestrial gastropods, archaeological data and OSL analyses: those of the Middle Holocene period, of the Greek–Roman time and of the Middle Ages. Sub-fossil terrestrial gastropods have been considered suitable indicators in the detecting Holocene climate–environmental changes. However, it is well-known that they could show problems as chronological indicators mainly due to aging effects induced by: (i) micro-particles of calcite/aragonite in the shell structure, derived from the local substratum and (ii) a variation of CO 2 content in the plants eaten. In order to verify these hypotheses, living terrestrial gastropods were collected from coastal areas and analysed using AMS. The results indicate that many living gastropods gave ages of 1500 years older than those expected, thus confirming the aging effect. As 14C ages of Middle and Late Holocene aeolian morphogenetic phases, obtained from terrestrial gastropods, seem to be confirmed by archaeological data and OSL analyses. The aim of this work is to verify if the age anomalies obtained from modern gastropods could be extended to the entire Holocene period.

Boulder accumulations produced by the 20th of February, 1743 tsunami along the coast of southeastern Salento (Apulia region, Italy)

The detachment of large boulders in the nearshore zone and their deposition farther inland are the main morphological effects of tsunamis on rocky coasts. Along the Otranto–Leuca coast (southeastern Apulia, Italy), two boulder accumulations have been recognized and studied. At the Torre Sasso locality, boulders weighing up to 31 t are scattered from sea level to about 5 m of elevation and clustered in groups of several imbricated elements. At Torre S. Emiliano an impressive accumulation made of large boulders has been recognized and studied. The accumulation is about 30 m wide and follows the present coastline for about 2.5 km at a variable distance of 15 to 40 m. Looking closer, it is compounded by two ridges. The ridge closer to the coastline shows a very steep slope seaward made of very large boulders emplaced in a vertical position; its top reaches about 11 m above m.s.l. The inner belt is lower than the outer one and consists of smaller boulders; it partly covers a 2 m thick colluvial deposit made of reddish sands. Huge blocks, weighing up to 70 t, cover the carved surface stretching from the coastline to the front of the first ridge. Analysis of the imbrication axes indicates that the catastrophic waves responsible for the development of the boulder accumulations most likely propagated from SSE to NNW direction. Karstic features occurring on the surface of the innermost boulders indicate a very recent age for their deposition as no differences have been found between the aerial-exposed surface and the soil-covered one. Three AMS radiocarbon age determinations performed on marine shells found landward the boulders have accumulated recently, i.e. within the last three centuries. Moreover, archeological remains in the top layers of the colluvial deposits covered by the boulders can be referenced to 16th–17th centuries. This evidence suggests that the 20th of February, 1743 earthquake was responsible for the generation of two large tsunami waves which caused the boulder accumulations to deposit. This earthquake was particularly violent in the Salento region where it reached grade IX on the MCS scale. Interestingly, chronicles of this event record a withdrawal of the sea in the Brindisi harbour, north of the study area. This study highlights the tsunamigenic potential offshore the southeastern Salento coast requiring that further strategies be devoted to mitigate the tsunami risk.

Three detailed, radiocarbon-dated, Holocene tufa and alluvial fan mollusc successions from southern Ontario: The first in northeastern North America

Fossil mollusc remains, particularly those of land snails, provide a wealth of detailed information concerning local Quaternary paleoenvironments and regional paleoclimatic conditions. However, this important resource is generally overlooked in North America and consequently quantitative, well-dated terrestrial mollusc successions are extremely rare here. In an attempt to redress this imbalance, a project examining the Holocene molluscan faunal history of northeastern North America has been initiated. Thus far, detailed mollusc successions and associated radiocarbon age determinations have been obtained from three sites in southern Ontario; two alluvial fans (Chine Drive Fan and Cudia Park Fan, both from the Scarborough Bluffs east of Toronto) and a tufa (West River Road, near Cambridge). The observed land snail successions to provide an initial view of the molluscan faunal history of this region during the period from the late glacial to the mid Holocene, between approximately 10,500 and 5000 radiocarbon years BP (yr BP). The molluscan data have also been used to reconstruct the paleoenvironmental history of southern Ontario during this time, documenting the progression from exposed, open habitats characterised by species such as Vertigo modesta, Vallonia albula, Columella columella and Vitrina angelicae limpida, to closed woodland biotopes indicated by the presence of taxa including Carychium nannodes, Nesovitrea binneyana, Paravitrea multidenta and Helicodiscus parallelus. This study has already demonstrated the potential of this technique in the study of Quaternary climatic and environmental change in eastern North America and represents a strong foundation for extending the analysis of fossil land snail successions to other sites throughout this region. It has also provided new and important insights into the establishment of the modern molluscan fauna, which are essential to the understanding of present day distributional patterns and environmental associations.

Occurrence of the Mytilus edulis complex on Nordaustlandet, Svalbard: radiocarbon ages and climatic implications

Fragments of the blue mussel (Mytilus edulis complex) are present on raised beaches in the vicinity of Langgrunnodden and Kinnvika, northwestern Nordaustlandet, Svalbard. Both of these localities are north of 80° N. New radiocarbon age determinations, together with earlier results, show that Mytilus colonies were present in this area for much of the fi rst half of Holocene time—from approximately 9000 to 5800 14C yr BP. Mytilus has also been recorded farther south in Nordaustlandet, at three localities in Wahlenbergfjorden. Age determinations of shells at two of these sites have yielded results in the range of 7400 to 6900 14C yr BP. The arrival of Mytilus to Nordaustlandet coincided with the early Holocene infl ux of warm North Atlantic Water off the west coast of Spitsbergen. The drastic warming in early Holocene time, which resulted in the rapid melt-off of glaciers and ice caps in Svalbard, also facilitated the establishment and perserverance of Mytilus colonies at this high latitude.

Occurrence of the Mytilus edulis complex on Nordaustlandet, Svalbard: radiocarbon ages and climatic implications

Fragments of the blue mussel (Mytilus edulis complex) are present on raised beaches in the vicinity of Langgrunnodden and Kinnvika, northwestern Nordaustlandet, Svalbard. Both of these localities are north of 80° N. New radiocarbon age determinations, together with earlier results, show that Mytilus colonies were present in this area for much of the fi rst half of Holocene time—from approximately 9000 to 5800 14C yr BP. Mytilus has also been recorded farther south in Nordaustlandet, at three localities in Wahlenbergfjorden. Age determinations of shells at two of these sites have yielded results in the range of 7400 to 6900 14C yr BP. The arrival of Mytilus to Nordaustlandet coincided with the early Holocene infl ux of warm North Atlantic Water off the west coast of Spitsbergen. The drastic warming in early Holocene time, which resulted in the rapid melt-off of glaciers and ice caps in Svalbard, also facilitated the establishment and perserverance of Mytilus colonies at this high latitude.

Society Islands (Central Eastern Polynesia) Chronology: 11 Radiocarbon Dates for the Late Prehistoric Expansion and Proto-Historic Periods in the ‘Opunohu Valley, Mo'Orea

The chronology of residential site construction and occupation in the upper reaches of the ‘Opunohu Valley, Mo'orea, Central Eastern Polynesia, has been debated over the last 15 yr. This paper reports a suite of 11 radiocarbon age determinations from excavations at 5 house sites and a simple temple structure (marae). Direct accelerator mass spectrometry (AMS) dating of wood charcoal identified to short-lived taxa confirms site construction and occupation during the mid-15th to 17th centuries, supporting that maximal population density was in the centuries immediately prior to European contact. The study demonstrates that targeted dating of multiple structures within residential complexes allows for multiple phases of site construction and use to be discriminated. These data are critical for adequately assessing site contemporaneity and the development, maintenance, and expansion of residential groups and their house clusters through time.

A Keith Phase Burial on the High Plains of Kansas

A flexed adult male burial was excavated from the cut bank of a dry tributary of Museum Creek, Sheridan County, Kansas. Associated artifacts include a well-worn grinding stone and a bone tool of indeterminate function. Analysis of sediment from the grinding stone led to the identification of diagnostic opal phytoliths from hackberry fruits. The geographic location of the burial and a radiocarbon age determination of 1370 ± 70 RCYBP are sufficient to place the burial site in the Keith phase taxon. A summary of Keith phase burials shows a great degree of variation in burial practices. The location of the solitary 14SD351 burial suggests that it is far from a settlement.

Multiarchive paleoseismic record of late Pleistocene and Holocene strong earthquakes in Switzerland

A multiarchive approach has been applied to the investigation of the late Pleistocene and Holocene record of strong earthquakes in Switzerland. The geological archives used for this study include active faults, lake deposits, slope instabilities, and caves. In the Basle area, eight trenches were opened across the Basle–Reinach fault, nearby rockfall deposits were systematically investigated, sediment cores were taken from two lakes, and nine caves were studied. In Central Switzerland, five lakes were investigated by means of high-resolution seismic lines and sediment cores. Furthermore, three caves were studied in Central Switzerland. Altogether, the investigations are based on more than 350 km of high-resolution reflection seismic lines, 450 m of core samples, 260 m of trenches, and 245 radiocarbon age determinations. The measured co-seismic displacements along the Basle–Reinach fault supply independent information for the magnitude of the AD 1356 Basle earthquake exclusively based on geological evidence. Deformation features related to three well-documented strong historic earthquake shocks were identified. Deformation features of the AD 1774 Altdorf and AD 1601 Unterwalden earthquakes can be used to calibrate paleoseismic evidence in Central Switzerland. Altogether, traces of 13 earthquakes could be found in the two study areas, all of them with magnitudes M w ∼ 6 or greater. For the first time, the earthquake catalogue for Switzerland can be extended back beyond historic records, into the late Pleistocene, spanning 15,000 years.

An Assessment of Radiocarbon Dates from Palau, Western Micronesia

Archaeological investigations in the Republic of Palau, Micronesia, have produced 409 radiocarbon age determinations from cultural contexts, indicating a range of Palauan occupation from about 3000 yr ago into the modern era. However, these dates are scattered among numerous sources (many difficult to obtain) and are presented in a number of different formats and calibrations. The goal of this paper is to compile a usable, systematic database of all of these Palauan cultural 14C assays. This database will be suitable for developing and evaluating chronological models, an effort being undertaken as a separate paper. Prior to constructing prehistoric colonization and cultural chronologies for Palau, the validity of each assay and the relative adequacy in sample size per cultural and environmental zones must be examined. After systematic recalibration, the reliability of the dates is evaluated in light of sample material, cultural context, and site formation processes. A method for dating monumental earthwork complexes through site formation analysis is presented. Sets of 237 valid and 58 potentially valid 14C dates remain to develop chronological models. The representation of Palau's environmental zones, site types, and regions within the dating pool is examined and compared to ensure meaningfulness in these chronological models. Newly obtained 14C age determinations are also provided.

Potential role of humoral immunity in cardiac dysfunction of patients suffering from dilated cardiomyopathy

A record of geomagnetic secular variation for the last 7500 years has been obtained from three cores of lake sediment from Sorø Sø in Denmark. The time-scale has been derived from six radiocarbon age determinations on one of the cores. Variations in geomagnetic declination and inclination agree well with those found in a previous study using sediments from another Danish lake, Skanderborg Sø, some 120 km from Sorø Sø. A correlation with the record from the U.K. has been made, but with age differences of up to 1000 years, which are attributed to the dating errors inherent in the radiocarbon method when applied to lake sediments in both the U.K. and Danish sediments. The virtual geomagnetic pole path since 7500 BP appears to have had periods of both clockwise and anticlockwise motion of 1000-year duration, where the looping is open, interspaced with shorter periods of ∼ 500 years in which the geomagnetic behaviour is more irregular. It is suggested that this indicates a possible regularity in the pattern of field behaviour during the Post Glacial.

Preliminary 14C Dates on Bulk Soil Organic Matter from the Black Creek Megafauna Fossil Site, Rocky River, Kangaroo Island, South Australia

Radiocarbon age determinations and stratigraphy suggest that the deposits in Black Creek Swamp on Kangaroo Island record 3 phases of deposition and associated soil development which spanned at least the last 20,000 yr. Four new 14C age determinations on bulk soil organic matter and their stratigraphic context are presented in this paper. Three of these age determinations (FP6: 15,687 ± 110 BP [WK11487]; FP7: 16,326 ± 385 BP [WK11488]; and FP8: 17,618 ± 447 BP [WK11489]), are from the organic-rich fossil layer located 45–75 cm below the current floodplain surface. The fourth, a much younger date, FP5: 5589 ± 259 BP (WK11486), was obtained from the base of the overlying modern soil. The dates for the fossil layer increase systematically with depth and correlate well with 5 previous 14C dates (Hope et al., unpublished), ranging between 15,040 ± 120 BP and 19,000 ± 310 BP. This suggests that the data set represents a possible minimum age of the bulk organic matter, and considering the high organic matter contents of approximately 8%, has implications for the age of the megafauna buried in this layer. The overlying modern soil, with its much younger date, contains lower levels of organic matter (3–7%) and gastropods not seen in the fossil layer. This suggests a substantial change in environmental conditions probably due to an alteration in the floodplain drainage conditions. This chronological and sedimentalogical discontinuity indicates that 2 distinct depositional regimes existed and were separated by up to 10,000 14C yr. A calcareous, sandy silt deposit underlying the fossil layer is a calcarenite deposit with low total organic content and is considered the base of the section; it suggests a third separate depositional episode. As such, the Black Creek Swamp in the southwest corner of Kangaroo Island formed intermittently over at least the last 20,000 yr during 3 distinct depositional phases, one of which was the formation of the fossil-laden, organic-rich floodplain surface, which has a possible minimum age of approximately 15,000 to 19,000 BP.

Large boulder accumulations by extreme waves along the Adriatic coast of southern Apulia (Italy)

The Adriatic coast of southern Apulia (Italy) is marked by the presence of large boulder accumulations. Boulders are up to 8 t in weight and arranged either in small groups or rows composed of a few imbricated elements. The lower surface of some of the boulders is covered by biogenic encrustation which suggests that they were possibly carved from the mid or sublittoral zone and that they capsized during their transport. Other boulders, detached from the supratidal zone, have their surface affected by tilted rock pools. New horizontal solution pans are continually forming. A detailed survey of a large boulder accumulation was carried out at Torre Santa Sabina. Direct observations were also made concerning the carving out and transportation of one single boulder during the severe storms in that area on January 4th, 2002 and on January 12th, 2003. Collated data from both the survey and the direct observations including some radiocarbon age determinations and hydrodynamic calculations suggest that the studied accumulation was due to the superimposed effects of one or two tsunami as well as of storm waves. Tsunami would be responsible for the detachment and transportation of the largest boulders, while storm waves may have been responsible for the carving out and transportation of the newer, smaller blocks and for moving once again the largest boulders. It was in this way that a typical boulder accumulation was produced. The collated data suggest that two tsunami may have recently struck the Adriatic coast of southern Apulia. The first possibly took place on the Dalmatian coast as a result of the earthquake on April 6, 1667 which destroyed Ragusa (modern day Dubrovnik). The second tsunami would have accompanied the strong earthquake which took place in southern Apulia on February 20, 1743.

Very high resolution paleosecular variation record for the last ∼1200 years from the Aral Sea

A record of geomagnetic paleosecular variation (PSV) spanning the last ∼1200 years has been obtained from two lacustrine sediment cores from the north part of Aral Sea (Kazakhstan). Magnetic susceptibility and NRM intensity have been used for correlating between cores and reconstructing composite core data. The main swings and fine details of declination and inclination records correlate well between both cores. A very high sedimentation rate (up to 25 mm per year) due to recent tectonic activity of the region provides a very high resolution PSV record for the interval from 450 ± 100 years BP to 655 ± 65 years BP. The results which have been dated by eight AMS radiocarbon age determinations, suggest that a 200–400 years secular variation period with amplitudes in declination and inclination up to 10–15° existed regularly during the time interval 0–1200 BP. Amplitudes of the PSV record from Aral Sea are not reduced and smoothed by postdetrital magnetization processes. They adjoin to the historical data model and are considered to represent a reliable paleosecular variation record for the Aral Sea region for the last ∼1200 years.

Floodplain aggradation and pedogenesis in a semiarid environment

Alluvial valley fills in the upper Republican River basin, southwestern Nebraska, provide evidence for processes of aggradation and pedogenesis on semiarid cut-and-fill floodplains. Sheetflow deposition on unchanneled valley floors represents an important mechanism of valley aggradation. Sheetflow deposits contain parallel to sub-parallel laminae and discontinuous lobate sedimentary structures. Rates of sediment deposition on cut-and-fill floodplains strongly determine the degree to which pedogenic features develop within aggrading alluvium. Three pedofacies common to semiarid alluvial deposits correspond with increasing aggradation rates: (1) cumulic soils; (2) multiple buried soils; and (3) no pedogenic features. Radiocarbon age determinations from alluvial fills indicate that floodplain aggradation greater than approximately 0.5 cm year −1 limits soil formation: this represents a threshold rate of pedogenic assimilation. Floodplain soils formed under aggradation rates lower than this exhibit a strong positive relationship between aggradation rate and total CaCO 3 percent, and a negative relationship between aggradation rate and organic carbon percent. Recognizing the associations between pedogenic/sedimentologic features and floodplain aggradation rates can help interpret past rates of sediment transport, storage and deposition.

Alternative chronologies for Late Quaternary (Last Interglacial–Holocene) deep sea sediments via optical dating of silt-sized quartz

We summarize the results of a test on the potential of optical dating for the age assessment of Late Quaternary deep-sea sediments. Our approach combines a single aliquot regeneration (SAR) protocol for equivalent dose ( D e) estimation on fine silt-sized quartz with a time-dependent evaluation of supported and unsupported long-lived radioisotopes within the deposited sediment matrix. For this purpose nine samples from two independently dated deep-sea cores from the Indian Ocean were obtained. The SAR analysis resulted in mean D e estimates with precisions ranging from 0.9% to 3.7%. Combination of these data with measured radioisotope concentrations resulted in stratigraphically sensible ages ranging from ca 7 to 120 ka. These ages exhibit good agreement with existing chronologies for the cores based on radiocarbon age determinations and correlation of key volcanic, palaeoecological and isotopic events. Optical dating may provide an important additional dating method for Late Quaternary deep-sea sediments.

Ages of periods of sand movement in Hungary determined through luminescence measurements

The Late Glacial and Holocene climatic oscillations in Hungary are manifested by changing fluvial and aeolian sand deposition, as well as by intercalated soil formations. The sand-blown territories have special interest since the buried fossil soils provide detailed information about climate and environment changes. During the past two decades the time of the sand-moving periods was studied exclusively by radiocarbon age determination, but by now, thanks to the latest investigations, these results have been controlled and completed by the thermoluminescence and infrared optically stimulated luminescence dating methods. These techniques have been applied to provide a more detailed chronological framework for Late Pleistocene and Holocene sand accumulation periods. Five aeolian sand accumulation periods can be recognized covering the Late Glacial and Holocene time period at 14.0±2.3, 12.0±1.9, 9.2±1.7, 6.0±0.5 and 0.6±0.07 ka. The sand-blown formations are intercalated by soil horizons. The radiocarbon age estimates provide evidence for Late Glacial (Bölling, Alleröd) and Lower-Atlantic soil-forming periods.

The Mangarevan Sequence and Dating of the Geographic Expansion into Southeast Polynesia

A recently published archaeological sequence supported by information from six sites excavated in the Mangarevan group in 1959 is summarized in the context of additional data and current interpretations of the prehistory of southeastern Polynesia. The known part of the Mangareva sequence covers the period from ca. a.d. 1200 to the time of early nineteenth-century contact with Europeans, with its datingen hanced by four new radiocarbon age determinations plus four previous ones, all on samples collected in 1959. More recent information from archaeological investigations on nearby Pitcairn and Henderson islands, showing they formed part of a long-term interaction sphere with Mangareva, indicate that while the early part of the Mangareva sequence from ca. a.d. 800–1200 remains undocumented, buried cultural deposits for this interval probably exist within Rikitea village on the main island of Mangareva. An a.d. 700–800 settlement for the Mangareva group is consistent with a similar age and origin for the first inhabitants of Easter Island, as aspects of the thirteenthcentury assemblages from both places are comparable. A similar age is also supported by several dates for an initial colonization of Henderson Island in this period. Recent linguistic reworkingof the early subgroupingof Eastern Polynesian suggests Easter Island, Original Mangarevan, and probably the extinct Polynesian languages of Henderson and Pitcairn were the first in the region, placing the age of that subgroup around a.d. 700–800. A major secondary contact with Marquesan speakers who may have settled in Mangareva at a.d. 1100–1300, seems to have been the basis for changing it into a Marquesic language, of a form then taken to Rapa. The archaeology, biological relationships, and linguistic history of the region now provides a robust and consistent outline for the geographic expansion into Southeast Polynesia.

Preliminary optical and radiocarbon age determinations for Upper Pleistocene alluvial sediments in the southern Anti Atlas Mountains, Morocco

Abstract This paper presents the first results of a 14 C and optical luminescence dating project on extensive alluvial silt formations in the southern Anti Atlas Mountains in southern Morocco. The silts comprise three members: basal silts, an inter-silt fluvial gravel member and a top silt member and are incised by the rivers. Top silt dates are: 11 340–11 940, 12 670–13 130 cal. yr BP, and 10.6±0.7 ka (OSL). OSL dates for the inter-silt gravels are 29.6±2.0 ka and for the bottom silts is 45.0±3.7 ka. The sediments correlate with Soltanian stratigraphies known elsewhere in Morocco. To cite this article: M. Thorp et al., C. R. Geoscience 334 (2002) 903–908.

Determining the age of the mid-Holocene Tsuga cana densis (hemlock) decline, eastern North America

Pollen counts and radiocarbon age determinations from 60 sites in eastern North America are used to determine the age of the mid-Holocene T.ugai canadensis decline, and to analyse the errors associated with such age estimation. The age is determined as 4750 14C yr BP with a standard error of the mean of about 50 years. Despite the quantity of data available, large uncertainties in the choice of age-depth model make it impossible to determine a more precise age for this event. It is likely that there are similar problems, or worse, with attempts to determine the age of other Holocene events. Within the limitations of the available data set, the Tsuga canadensis decline was synchronous across the whole of its range.