• Radiocarbon laboratories

      McClure, Mark (Department of Geosciences, The University of Arizona, 2011-12-16)
    • Residential Chronology, Household Subsistence, and the Emergence of Socioeconomic Territories in Leeward Kohala, Hawai‘i Island

      Field, Julie S.; Ladefoged, Thegn N.; Sharp, Warren D.; Kirch, Patrick V. (Department of Geosciences, The University of Arizona, 2011-12-16)
      Previous research in leeward Kohala, Hawai'i Island, has determined that the Leeward Kohala Field System (LKFS), a vast agricultural zone covering ~60 km2, developed between the 14th and 18th centuries AD. Additional analyses have documented the establishment of traditional socioeconomic territories, known as ahupua'a, in tandem with the expansion of the field system. This article further refines the chronology of human settlement and socioeconomic development in leeward Kohala through the analysis of deposits associated with prehistoric residences. Based upon survey and excavation, we present a chronology for Hawaiian household transition and economic development in 2 study areas of leeward Kohala, spanning the field system to the coast. Forty-nine radiocarbon dates from short-lived plant materials and five 230Th dates on corals from residential and ritual features are synthesized into 3 temporal periods, which allow for comparison of residential size, distribution, number, and associated faunal materials from archaeological deposits. Changes in household composition and economy are suggested to have developed in tandem with the establishment of individual ahupua'a and land divisions within them, and the further development of agricultural production.
    • Table of Contents

      McClure, Mark (Department of Geosciences, The University of Arizona, 2011-12-16)
    • Using a Silica Substrate to Monitor the Effectiveness of Radiocarbon Pretreatment

      Dee, M. W.; Brock, F.; Bowles, A. D.; Bronk Ramsey, C. (Department of Geosciences, The University of Arizona, 2011-12-16)
      The objective of radiocarbon pretreatment is to eliminate any contaminant carbon from the sample material. Solvent washes and acid-base-acid (ABA) procedures are widely used for this purpose. However, quantitatively analyzing their effectiveness is surprisingly problematic, as it often requires large numbers of 14C measurements or high-precision compositional analysis. The technique presented here involves monitoring the impact of different forms of contamination by measuring their adherence to a non-carbonaceous substrate called Chromosorb. Firstly, the substrate was used in place of a 14C sample in order to monitor the accrual of carbon contamination during a standard solvent wash and ABA pretreatment. This produced a contamination profile against which modifications to the pretreatment procedure could be compared. Secondly, stocks were prepared of Chromosorb that had been infused with environmental contaminants and with common glues, adhesives, and preservatives. By monitoring the elimination of carbon from these stocks, the effectiveness of different pretreatment procedures could be evaluated and the most problematic of the contaminants for 14C dating could be identified.
    • Verification of an Archaic Age Occupation on Barbados, Southern Lesser Antilles

      Fitzpatrick, Scott M. (Department of Geosciences, The University of Arizona, 2011-12-16)
      The Caribbean Archaic Age (about 3000–500 BC) is thought to represent the earliest migration of humans from South America into the Lesser Antilles. However, here is a conspicuous absence of these early sites on islands south of the Guadeloupe Passage. To date, only a single radiocarbon date derived from a Queen conch (Strombus [Eustrombus] gigas) shell at the Heywoods site on Barbados was indicative of an Archaic occupation in the southern Antilles apart from a scattering of poorly reported (and mostly undated) sites. Given a number of issues associated with reliance on a single date to establish a cultural horizon, along with other problems derived from possible carbonate cement contamination and dating marine shells of a longer-lived species such as Queen conch, 2 additional samples were taken from the same unit and context at Heywoods to confirm whether the site is truly representative of an occupation during the Archaic Age. Results from a Queen conch shell adze in Context 7 dated to 2530–2200 BC (2 sigma) and overlaps with the only other Archaic date from the site dating to 2320–1750 cal BC, while a juvenile specimen of the same species from Context 8 at 3280–2940 BC (2 sigma) indicates that Barbados may have been settled even earlier. This suggests that Heywoods may be the oldest site between Trinidad and Puerto Rico. While further confirmation is required, these new dates have implications for understanding the nature of migratory ventures in the Caribbean, such as whether the Southward Route hypothesis which postulates that earlier migration events from South America during the Ceramic Age (beginning ~500 BC) initially bypassed the southern Lesser Antilles also applies to the Archaic, and if other phenomena such as active volcanism may have played a role in structuring settlement patterns. Questions also remain as to why Heywoods does not exhibit the typical lithic Archaic tool kit.
    • Water Column Profiles of Dissolved Inorganic Radiocarbon for the Kuroshio Region, Offshore of the Southern Japanese Coast

      Tsuboi, Tatsuya; Iwata, Hiroshi; Wada, Hideki; Matsuzaki, Hiroyuki; Sohrin, Rumi; Hiroe, Yutaka; Ichikawa, Tadafumi; Hidaka, Kiyotaka; Watanabe, Tomoo (Department of Geosciences, The University of Arizona, 2011-12-16)
      We present the water column profiles (surface to 2000 m depth) for dissolved inorganic radiocarbon ([delta]14CDIC) from 2 stations in the Kuroshio region including the Kuroshio large meander (LM) of 2004–2005. Surprisingly, the [delta]14CDIC value varied up to 125‰ in the intermediate layer, especially near 600 m depth. In addition, the [delta]14CDIC value was approximately -150‰ at 200 m depth at the northern station of Kuroshio in August 2005. This value is ~100‰ less than other [delta]14CDIC values for the same depth. In comparison, the [delta]14CDIC water column profiles for the southern station of Kuroshio and GEOSECS station 224 decrease down to 600 m depth and were similar below 600 m depth. Our results suggest that strong upwelling associated with the Kuroshio LM has a powerful influence on the [delta]14CDIC water column profiles in the study region.
    • Δ14C and δ13C of Seawater DIC as Tracers of Coastal Upwelling: A 5-Year Time Series from Southern California

      Santos, Guaciara M.; Ferguson, Julie; Acaylar, Kayla; Johnson, Kathleen R.; Griffin, Sheila; Druffel, Ellen (Department of Geosciences, The University of Arizona, 2011-12-16)
      Marine radiocarbon (14C) is a widely used tracer of past ocean circulation, but very few high-resolution records have been obtained. Here, we report a time series of carbon isotope abundances of dissolved inorganic carbon (DIC) in surface seawater collected from the Newport Beach pier in Orange County, within the Southern California Bight, from 2005 to 2010. Surface seawater was collected bimonthly and analyzed for 14C, 13C, and salinity. Results from May 2005 to November 2010 show no long-term changes in 13C DIC values and no consistent variability that can be attributed to upwelling. 14C DIC values have lowered from ~34 to about ~16, an 18 decrease from the beginning of this project in 2005, and is consistent with the overall 14C depletion from the atmospheric thermonuclear bomb pulse at the end of the 1950s. 14C DIC values, paired with salinity, do appear to be suitable indicators of upwelling strength with periods of upwelling characterized by more saline and lower DIC 14C values. However, a similar signal was not observed during the strong upwelling event of 2010. These results were obtained in the Southern California Bight where upwelling is fairly weak and there is a complex oceanographic circulation in comparison with the remaining western USA coastline. It is therefore likely that the link between DIC 14C, salinity, and upwelling would be even stronger at other sites. These data represent the longest time series of 14C data from a coastal Southern California site performed to date.