Oxygen isotopic composition of limpet shells from Beagle Channel: implications for seasonal studies in shell middens of Tierra del Fuego (original) (raw)
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Journal of …, 2012
Shell middens distributed along the coastal areas of the Beagle Channel (Tierra del Fuego) testify the primary role of marine resources in the successful social dynamic of hunter–gatherer–fisher societies (HGF) in extreme high latitude environmental conditions. Intertidal and subtidal limpet species are frequently identified taxa of these archaeological deposits. We investigated whether shell δ18O of the limpet species Nacella deaurata is a valuable record of local sea surface temperature (SST) and ambient water δ18O (δ18Ow) fluctuations, and in turn can be used to estimate the season of its exploitation by Holocene HGF. Sequential shell δ18O of modern species track seasonal changes of SST and δ18Ow. The comparison of shell δ18O profiles of N. deaurata and Nacella magellanica (a coexisting species) suggests the occurrence of distinct growth rate and physiological adaptations between species. Shell δ18O of zooarchaeological specimens of N. deaurata from Lanashuaia II suggests that animals were exploited predominantly in winter and that experienced similar environmental conditions of present day at ∼1320 years BP. Results also indicate that N. deaurata is a valuable candidate for studying past seasonal changes in SST and δ18Ow in this southernmost part of South America.► Limpet species are frequent components of shell midden sites in the Beagle Channel. ► Shell δ18O of N. deaurata and N. magellanica track changes in SST and seawater δ18O. ► Distinct growth rate and physiology seems to be involved in shell δ18O profiles. ► Limpet exploitation at Lanashuaia II (∼1320 years ago) occurred mainly in winter. ► New evidence of limpet shell δ18O as proxy for seasonal SST oscillations.
The Journal of Island …, 2011
Shells of Nacella magellanica are abundant in archaeological shell middens distributed along the Beagle Channel. In this study we analyzed the oxygen isotopic composition of shells of this species to obtain information on its seasonal exploitation patterns by hunter-gatherer-fisher groups in this region during the nineteenth century. Oxygen isotopic data from shells recovered from Lanashuaia and from some occupations of Túnel VII (both contact sites) indicate that N. magellanica was gathered in different seasons. Our data agree with fauna-derived seasonal reconstructions, and collectively these data provide more detailed economic scenarios. Comprehensive results confirm that in the nineteenth century, Yamana people continuously occupied the coast of the Beagle Channel by means of short-lived campsites.
Limpet shells are common components of many archaeological sites in the Mediterranean. To test whether δ 18 O values from archaeological Patella caerulea shells can serve as a reliable palaeothermometer for the Mediterra-nean and a reliable archive of season of collection information, we collected live P. caerulea from eight Mediter-ranean locations in Croatia, Israel, Libya, Malta, Tunisia, and Turkey. Shell growth patterns were studied in section, and samples for oxygen isotope analysis were milled from the shells and used to calculate sea surface temperature (SST). As with other species of limpet, SST reconstructed from P. caerulea δ 18 O values were lower than expected from observational records. However, when a correction factor of −0.72‰ was applied, the shells recorded SST within the range of instrumental SST. SST calculated from δ 18 O shell values of the most recently formed shell portion of monthly-collected shells from one site in Libya were strongly and significantly correlated with instrumental SST in the region (R 2 = 0.95). Oxygen isotope curves from individual shells sampled at high resolution from each of the study sites across the Mediterranean exhibited sinusoidal patterns. Annual growth lines correlated with the lowest δ 18 O shell values and were thus formed in summer. However, shell growth rates varied markedly between the sites. Some sites with larger shells recorded less than a year of growth in broad, highly irregularly shaped increments. At other sites, medium sized shells recorded several years of growth with clear, regular growth increments. A sclerochronological approach can therefore be used to pre-screen limpet shell sections before geochemical sampling. The δ 18 O shell values from shells sampled at high-resolution recorded the full seasonal range of instrumental SST at each collection site. This reinforces the potential of this species as one of the few sub-seasonal resolution palaeoenvironmental archives in the region. Additionally, the pattern of δ 18 O shell variation from the last formed shell portion was studied to determine whether accurate season of collection information could be identified from P. caerulea shells. The correct season was interpreted N 80% of the time indicating that this species is a good candidate for seasonal shellfish foraging studies using archaeological shells.
Quaternary International, 2018
Palaeoenvironmental information collected from zooarchaeological (guanaco exploitation) and palynological (pollen and fungal remains) records from Tierra del Fuego and Isla de los Estados allowed us to reconstruct the natural scenarios during the Holocene to better understand the human behavioral patterns and cultural changes. We have seen that changes in subsistence and guanaco exploitation would not have necessarily been synchronous with climatic variations. However, there is evidence of great climatic and environmental variability in the Fuegian Archipelago during the last 6000 years that would have influenced the distribution of the huntergatherer societies. In particular, the Little Ice Age (LIA) event could have caused a reorganization of subsistence activities of the hunter-gatherer societies. The stress caused by this severe climatic episode might have changed the availability of the guanaco population over the inland and coastal areas along the Beagle Channel. Indeed, the colder conditions would have significantly impacted on both the animal population and the availability of their food sources. In summary, the guanaco availability decreased under those colder and intense winters, which is clearly reflected in the substantial drop in the zooarchaeological record.
Fishing intensification development during the Late Holocene in the Beagle Channel is recognized in zooarchaeological studies, especially in a diversification to pelagic fish, implying an expansion of fishing practices to pelagic zones. In this paper, we undertake a paleoecological framework based on stable isotope analysis (δ13C and δ15 N) of modern and archaeological fish collagen bones. In this analysis we intend to provide an independent record to investigate possible variations in the patch use in marine fishing activities by hunter-gatherer societies in southern South America. Archaeological bones of Macruronus magellanicus, Merluccius sp. and Thyrsites atun were recovered from three stratified shellmiddens located in the coast of the Beagle Channel. In addition, modern samples of Macruronus magellanicus, Merluccius hubbsi and Merluccius australis were obtained at three different locations of the Patago-nian continental shelf. Macruronus magellanicus results highlight the relative nearshore character of the archaeological specimens. No differences were found between archaeological and modern values for Merluccius sp., which indicate the offshore character of the archaeological specimens of this species. Results also show that the archaeological samples of Thyrsites atun are related to offshore ecosystems. In sum, stable isotope values of archaeological specimens agree with previous interpretations from zooarchaeological analyses of deep-water fishing during the Late Holo-cene in the Beagle Channel.
PALAIOS, 2013
In the western North Atlantic and Gulf of Mexico, isotope sclerochronology and field studies of the hard clams, Mercenaria mercenaria and M. campechiensis, collected across a latitudinal gradient show patterns in the seasonal timing of slow versus fast shell incremental growth. It is unknown, however, if similar patterns exist in the eastern North Atlantic. The European limpet, Patella vulgata, is abundant in rocky shore communities and archaeological deposits along the eastern North Atlantic. As such, it is a potentially valuable archive for paleoclimate and archaeological research. We used isotope sclerochronology to identify the seasonal timing of annual growth line formation in shells from the cold-and warm-temperate zones and at the boundary between these zones. Four shells from the cold-temperate zone (United Kingdom and Norway), five shells from the warm-temperate zone (Spain), and six shells from the boundary (near the English Channel) were analyzed. The isotopic records represent between two and eight years of growth. Cold-temperate shells formed annual lines in winter, and warm-temperate shells produced annual lines in summer. A mixed pattern was found at the boundary. This pattern in the seasonal timing of slowed growth across a latitudinal gradient is similar to that shown in studies of Mercenaria in the western North Atlantic. Thermal tolerance is the most likely mechanism for the observed changes in the timing of annual growth line formation with latitude.
Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia
Environmental Archaeology
The residents of the Canary Archipelago consumed limpets since the arrival of humans ∼2500 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This work preliminarily explores shell margin oxygen isotope composition (δ 18 O) and body size of the black limpet (Patella candei d'Orbigny, 1840) from archaeological sites in the Canary Islands to assess possible seasonal variability and intensity of shellfish collection throughout the late Holocene. The shell margin δ 18 O values of 100 shells (radiocarbon dated between ∼500 and ∼1800 cal. yr BP) were analysed to estimate sea surface temperature (SST) at time of death. Paleotemperature estimates suggest shellfish harvesting was not year-round, and was avoided in the cooler months (when SST < 20°C). This pattern differs from most higher latitude Mesolithic and Neolithic human groups, which gathered shellfish year-round, targeting winter more heavily. Preliminary body-size measurements suggest shell sizes have experienced a decline from aboriginal times to the present, which possibly resulted from increasing anthropogenic pressures. During aboriginal inhabitation, maximum adult shell size remained stable, suggesting that present-day harvesting practices are more intense than harvesting from aboriginal human groups. This intensive collection has likely diminished the average adult size of limpet populations in the islands by ∼27%.
Archaeological analysis of shell middens in the Beagle Channel, Tierra del Fuego Island
International Journal of Osteoarchaeology, 2001
An archaeological programme beginning in 1993, in the Beagle Channel, aims to describe the long-term record of maritime faunal exploitation, and relate it to the environmental record. Results from quantitative analysis of remains from a series of shell midden excavations indicate a remarkably stable and resilient marine biota over the last 6500 years. Only in the previous century have there been changes in fauna, which might correspond to recent global warming. Copyright
Revista geológica de Chile, 2008
As the Beagle Channel lies between the Atlantic and the Pacific oceans, this is a critical region for the interpretation of faunal distributions in the Magellan Region. This work proposes a paleoenvironmental interpretation of the Holocene, inferred from malacological data. The development of different local benthic paleocommunities during the mid-Holocene is associated with the diversity of habitats inside this channel. The analysis of records of Venus antiqua and Ensis macha through time and their geographic links to ecological factors showed that these taxa are typical elements of the cold-temperate seas throughout the Magellan Region, showing a similar range of distribution and paleodistribution. The presence of these taxa in life position (AMS 14 C of 6,276±41 years BP) suggests that during the mid-Holocene the Beagle Channel was a path for dispersion of these taxa between the two oceans. Whether Venus antiqua and Ensis macha are Pleistocene survivors or Holocene migrants is herein discussed. In the future, integrated cross-disciplinary studies will be necessary for a better understanding of the biogeographic relationships among magellanic mollusks.
This paper presents a systematic analysis of the shellfish assemblages recovered from Heshkaia 35, an archaeological site located in the southern tip of South America. Possible arguments concerning to environmental variations and resource depression are considered in an attempt to explain taxa composition and shell size. Results are also discussed in light of expectations based on optimal foraging models and taking into account other factors beyond biological parameters. Shellfishing activities were focused on small mussels, with statistical significant changes in mean shell size along the archaeological sequence of the site. Current knowledge about past variations in sea surface temperature does not seem to explain changes in shell size. Gathering of small mussels appears to be the corollary of resource depression at a local scale. This interpretation reinforces arguments that foraging decisions would have derived from territorial packing on the southeastern coast of Tierra del Fuego during the Late Holocene.