Shell Midden Sites Research Articles

Holocene climate and seasonality of shell collection at the Dundas Islands Group, northern British Columbia, Canada—A bivalve sclerochronological approach

To analyze environmental changes and the seasonality of shell collection in British Columbia during the Holocene, oxygen isotopes were measured from modern and archeological (1337–7438calyr BP) shells of the butter clam Saxidomus gigantea. 1697 discrete isotope samples were taken from two modern and 27 archeological shells with a high temporal resolution (sub-seasonal up to daily). Archeological shells were collected from five shell midden sites on the Dundas Islands Group, northern British Columbia, Canada. The oxygen isotope data reveal clear annual cycles, with the most positive δ18Oshell values occurring during the cold season (slower growth, annual growth line formation) and the most negative δ18Oshell values during the warm season (period of faster growth). Whereas the most positive δ18Oshell values remained relatively constant throughout the Holocene, the warm season δ18Oshell values reflected considerable variability. Summer values observed in the early and late Holocene became approximately 1‰ more negative around 2500–3000 and 5500–6000 BP, implying lower salinity during the Mid-Holocene. Variations in the oxygen isotopic composition of marine shells reflect changes in temperature and salinity. Such large changes in δ18Oshell are unlikely being caused by temperature changes alone. Furthermore, the large annual δ18Oshell amplitude of 3.29–6.56‰, which corresponds to a temperature range of 14.5–29.0°C, exceeds the local annual temperature range by 2.5–17.0°C (0.58–3.85‰). The shell isotope record was also compared with other proxy archives, such as pollen, lake sediments and chironomid communities. The climate changes reflected in the δ18Oshell record match well with environmental changes reported for British Columbia.In addition to the climate information outline above, details about the season of shell collection by the occupants of Dundas Islands can also be obtained from the oxygen isotope and sclerochronological analyses of shells. The oxygen isotope profiles reveal that the archeological shells were collected year-round through time, and that there is no difference in the collection pattern between small and large shell midden sites. This is indicative of a multi-seasonal shellfish harvesting as well as long-term variation in occupation patterns at the Dundas Islands. Despite changes in climate over the Holocene, people maintained a consistent pattern of year-round shellfish harvest. The Mid-Holocene transition is also characterized by a number of cultural changes ranging from technological changes to changes in settlement and subsistence practices of hunter–gatherer groups.

Changing Perspectives in Australian Archaeology, part VIII. Burins, bones and base camps: a re-analysis of Aire Shelter 2, Glenaire, southern Victoria

Archaeological studies often conclude that some sites are neatly identifiable as base camps, stopovers or tool specific locales. Task reconstruction and interpretation of on-site activities affect our understanding of mobility patterns and subsistence and our ability to distinguish reconfigured land-use and population change. A re-analysis of Aire Shelter 2 is presented here to consider the potential of usewear and residue studies for evaluating site function, in the context of coastal wetlands in southwestern Victoria. Traces of use were found on 242 stone artefacts. Identified tools include finely retouched flint scrapers and snapped flakes with burin edges associated with graving bone. The usewear and faunal analyses indicate an atypical prehistoric assemblage that implies an alternative site function to that originally proposed. Rather than a base camp, the site is an infrequently used locale associated with hunting and the manufacture of bone points. Although theoretical reconstructions of land use suggest population contraction into winter base camps situated around coastal wetlands, there is no compelling evidence that such a site has been found at Aire Shelter 2, although nearby dune shell midden sites are likely candidates.

Coastal resource intensification across the Pleistocene–Holocene transition in Northern Spain: Evidence from shell size and age distributions of marine gastropods

Evidence for the exploitation of marine resources has been identified throughout prehistory but its relative importance has varied. Knowledge for earlier periods is biased by low archaeological visibility, and so the majority of hypotheses support the occurrence of intensification in the exploitation of marine resources during the Holocene. In the Cantabrian region (northern Spain) intensification has been proposed by some authors and rejected by others and there is also debate over when it began. Marine molluscs have been one of the most studied resources to support or reject intensification, and these studies have been mainly focused on variations of shell size through time. The hypothesis supporting intensification suggests that the decrease in molluscan size during the Holocene was caused by human pressure, whilst the alternative hypothesis is that this was induced by climatic and environmental conditions. In this paper, I study change of shell size and age distributions in northern Spain leading up to and after the Pleistocene–Holocene transition (35,000–5700 cal BP) using samples of four gastropod species from 18 shell midden sites. The species studied are the most abundant in the regional shell middens: Patella vulgata Linnaeus 1758, Patella intermedia Murray in Knapp 1857, Osilinus lineatus (Da Costa, 1778) and Littorina littorea (Linnaeus, 1758). The trends observed in both shell size and age structures shows that changes during the Upper Paleolithic may be due to climatic factors, but the constant decrease in both variables during the Mesolithic and the early Neolithic was caused by human pressure.

Big Sites, Small Sites, and Coastal Settlement Patterns in the San Juan Islands, Washington, USA

ABSTRACT In this article we examine prehistoric coastal settlement patterns in the San Juan Islands, Washington by integrating dating work with erosion studies, accumulation rate analysis, and paleoenvironmental data. Dating work draws on previously published radiocarbon dates from big sites and new radiocarbon dates from both big and small sites. We find that an increase in abundance of sites at 650–300 cal BP is amplified but not created by site destruction caused by coastal erosion. We hypothesize that prehistoric peoples established more permanent settlements on the San Juan Islands after 650 cal BP during a wetter climate regime. By calculating accumulation rates for shell midden sites and considering climate change and access to freshwater, we test this hypothesis and discuss differences between temporal patterns in the San Juan Islands and southwestern British Columbia.

Marine resources exploitation by Palaeolithic hunter-fisher-gatherers and Neolithic tribal societies in the historical region of the Strait of Gibraltar

The Strait of Gibraltar is a geographic region between the south of Europe and the north of Africa. On the basis of the geological, geographical and ecological evidence, this is considered a historical region. Prehistoric societies that lived during the Pleistocene and Holocene on both sides of the Strait left behind very similar archaeological records. Marine resource exploitation is recorded in the African zone of the Strait, where malacofauna is found in the Middle Pleistocene levels at Benzú rock shelter dated at 254 ka. To the north of the strait, the Cadiz coast has shell midden sites associated with Mousterian technology. Continuity in the technological records related to the Upper Palaeolithic is present in this area and on both slopes of the Strait, as in Nerja Cave (Spain), Gibraltar caves (UK) and the caves in the Tangier area (Morocco). Although some variability in the technological and cultural sequences has been observed on both sides of the strait the marine resources exploitation suggests similar ways of life. During the Holocene, continuity appears among agricultural groups. An increase in the fishing and shellfish collection by the Neolithic societies is a further interesting aspect of this region, as is shown in Tetouan Caves (Gar Cahal and Kaf That el Ghar) and Benzú Cave (Ceuta) on the southern side of the Strait, and Embarcadero Rio Palmones and Retamar (Cádiz) on the north side. The new data collected during recent years demonstrates a deeper antiquity of the shell midden deposits and in the exploitation of marine resources in this area for hunter-gatherer societies with Mousterian technology. A new vision also emerged for the economy of the Neolithic societies of the Strait of Gibraltar, with marine resources exploitation representing as a very important activity.

Archaeological Evidence for a Double-Crested Cormorant (Phalacrocorax auritus) Colony in the Pacific Northwest, USA

Double-crested Cormorants (Phalacrocorax auritus) were not observed breeding in the inner coast of Washington and British Columbia until the 1920s and 1930s, whether the breeding was either a re-colonizing event or a new expansion was unknown. Archaeological evidence from Watmough Bay, a shell midden site on Lopez Island, San Juan Islands (Washington State), was analyzed to place the recent changes in breeding distribution in deeper historical context. The Watmough Bay faunal assemblage contains large numbers (n = 2,397) of cormorant bones. Of those specimens that could be identified to species (n = 358), 99.7% were identified as Double-crested Cormorants. The majority (97%, n = 2,336) of the cormorant remains are from juveniles or chicks, which were collected while still at the colony. Radiocarbon dating indicates the majority of the site accumulated between AD 300– 600. Evidence for a ca. 1,500-year-old Double-crested Cormorant colony near Lopez Island confirms that the species did breed in the region prior to the early 20th century. The study further documents the value of archaeological data for current wildlife management.

Investigation of amino acid δ 13C signatures in bone collagen to reconstruct human palaeodiets using liquid chromatography–isotope ratio mass spectrometry

This research presents the individual amino acid δ 13C values in bone collagen of humans ( n = 9) and animals ( n = 27) from two prehistoric shell midden sites in Korea. We obtained complete baseline separation of 16 of the 18 amino acids found in bone collagen by using liquid chromatography–isotope ratio mass spectrometry (LC–IRMS). The isotopic results reveal that the humans and animals in the two sites had similar patterns in essential amino acids (EAAs) and non-essential amino acids (NEAAs). The EAA and NEAA δ 13C values in humans are intermediate between those in marine and terrestrial animals. However, the threonine δ 13C values in humans and animals measured in this study are more highly enriched than those of other amino acids. At both sites, all amino acids in marine animals are 13C-enriched relative to those of the terrestrial animals. The isotopic evidence suggests that the Tongsamdong human had EAAs and NEAAs from marine food resources, while the Nukdo humans mainly had EAAs from terrestrial food resources but obtained NEAAs from both terrestrial and marine resources. The δ 13C isotopic differences in amino acids between marine and terrestrial animals were the largest for glycine (NEAA) and histidine (EAA) and the smallest for tyrosine (NEAA) and phenylalanine (EAA). In addition, threonine among the EAAs also had a large difference (∼8‰) in δ 13C values between marine and terrestrial animals, and has the potential to be used as an isotopic marker in palaeodietary studies. Threonine δ 13C values were used in conjunction with the established Δ 13C Glycine–phenylalanine values and produced three distinct dietary groups (terrestrial, omnivorous, and marine). In addition, threonine δ 13C values and Δ 13C Serine–phenylalanine values were discovered to separate between two dietary groups (terrestrial vs. marine), and these δ 13C values may provide a potential new indicator for investigating the distinction between marine and terrestrial protein sources in human diets.

Inland shell midden site-formation: Investigation into a late Pleistocene to early Holocene midden from Tràng An, Northern Vietnam

Over the course of the past two decades there has been growing research interest in the site formation processes of shell middens. This stands along-side and is being used to inform cultural, dietary and palaeo-environmental reconstructions. Just as midden site formation processes have turned out to be many and varied, however, the kinds of shell-bearing sites that past human communities created are likely to have been no less diverse. Subsuming such sites under a single category – shell middens – normalises that variation and may lead to the misinterpretation of site function. The greater part of research in this field also continues to focus on coastal shell middens; comparatively little attention has been paid to middens containing freshwater and especially terrestrial molluscs from hinterland locations. As a result, much of the current understanding about shell-midden sites carries a spatial as well as a functional bias. This paper hopes to contribute towards discussion on both fronts. It presents a detailed examination of the formation processes that went into the creation of a land snail-dominated late- to post-glacial midden from northern Vietnam, and considers the role that it may have played in the early settlement of this area. The data presented comes from ongoing archaeological excavations at Hang Boi, a cave located in the sub-coastal karstic uplands of Tràng An park, in the Vietnamese Province of Ninh Bình.

Use-wear analysis of obsidian artifacts from Later Stone Age shell midden sites on the Red Sea Coast of Eritrea, with experimental results

This paper presents results of use-wear study on lithic artifacts from two Later Stone Age sites (Gelalo and Misse) on the Red Sea Coast of Eritrea. The sites produced large quantities of lithic artifacts in association with mollusk shells and ostrich eggshell beads, but it is unclear if all the stone tools were required for bead and mollusk shell processing. The study involved recording of microfracture damage traces in order to infer the use-material and the manner in which the artifacts were used. A large percentage of the analyzed samples from Gelalo and Misse preserve wear patterns suggestive of human use. The diagnostic wear types include: (1) dense step, snap (crushing) and hinge fractures typically confined on the working edges, and (2) feather scars organized in a scalar manner visible on the ventral and dorsal surfaces of the active parts. The observed damage patterns suggest cutting and engraving medium to hard materials. The evidence is incomplete for more generalization about the specific activities carried out at the sites. A brief experimental study involving ostrich eggshell drilling, oak twig sawing and bark scraping, meat slicing, and mollusk shell sawing and drilling was carried out to aid interpretation of wear features observed on the archaeological specimens. Wear traces produced by sawing mollusk shell and oak wood showed close affinity to those observed on the archaeological specimens. The study contributes important information about early Holocene site use on the Red Sea Coast of Eritrea. The close association of used lithic artifacts, symbolic objects (beads) and broken shell remains indicates that the sites were habitation areas.

Micromorphological perspectives on the stratigraphical excavation of shell middens: a first approximation from the ethnohistorical site Tunel VII, Tierra del Fuego (Argentina)

Due to their problematic stratigraphy, shell middens have traditionally been excavated by artificial stratigraphical cuts. This approach has often led to the obliteration of the original depositional sequence, removing important information regarding depositional and post-depositional processes, and human frequentation. Since the 1970s, an Argentinian team has been excavating archaeological shell middens in the Beagle Channel with a detailed stratigraphical approach, based on the excavation of actual depositional units (peeling), rather than artificial cuts. In the 1980s, Spanish archaeologists joined the Argentinean team and launched a series of new projects involving the excavation of ethnohistorical Yamana fisher-hunter-gatherer sites. The first excavated midden site was Tunel VII, from which two monolith columns of about 50 cm each (C11 and C12) that spanned the whole stratigraphy were extracted. The two columns were consolidated with resin, and two series of thin sections produced to corroborate stratigraphical observations made in the field, and to verify hypotheses related to the formation of archaeological shell midden sites. We present here the first results obtained from the microscopical observation of seven thin sections from column 11 (West column), extracted from a portion of the profile originally described as corresponding to the hut entrance and associated floor. The observation of microscopical features invisible in the field has provided supplemental information about the depositional and post-depositional processes affecting shell midden sites. We have also preliminarily defined a number of micromorphological characteristics identifying human activities such as discrete shell deposition events, phases of preparation of the hut floor, and compression by repeated trampling. Finally, we have explored the possibility of establishing some guidelines to characterise the length and character of frequentation phases of the site previous to its final abandonment at the beginning of the 20th century.

The archaeology of the Port Hedland coastal plain and implications for understanding the prehistory of shell mounds and middens in northwestern Australia

AbstractThis paper reports the archaeological salvage, radiocarbon dating and analysis of seven shell midden sites located south of Port Hedland, and makes observations regarding the archaeology of the Port Hedland region and the Abydos coastal plain. The excavations revealed an almost continuous sequence of archaeological sites dating between 5250calBP and 50calBP years. These include some of the earliest and latest radiocarbon ages associated with Anadara granosa dominated middens, shell mounds and earth mounds from northwestern Australia. Where earlier researchers had suggested that Anadara exploitation in northwestern Australia, and particularly on the Abydos plain and Burrup Peninsula, was limited to between 4200 and 1600 BP, these excavations demonstrate that the exploitation of Anadara shell in the Port Hedland region was continuous from at least 4400calBP (and possibly as early as 5350calBP) until the early twentieth century. Based on a consideration of their contents and ages, it is suggested that the various forms of shell accumulations in the study area, including shell mounds, earth mounds, surface scatters and stratified lenses of shell midden, are likely to vary more as a result of site formation processes than Aboriginal people's past gathering practices. This finding has broader implications for understanding the place of Anadara shell mounds and middens in the prehistoric regional economy of northwestern Australia.

Stable isotope evidence of human diet at the Nukdo shell midden site, South Korea

Carbon and nitrogen stable isotope analysis was undertaken on bone collagen extracted from archaeological human ( n = 48) and animal ( n = 45) skeletons from the Nukdo site, Location I C, South Korea. This shell midden and grave site is dated from the late Mumun (550–300 BC) to early Iron Age (300 BC-1 AD) periods. The herbivorous mammals fell within the range of C 3 consumers, with average values of δ 13C = −21.0 ± 0.5‰ and δ 15N = 3.6 ± 0.5‰ for deer ( n = 16) and δ 13C = −20.6 ± 0.5‰ and δ 15N = 4.5 ± 2.0‰ for wild boar ( n = 17). Humans from this site averaged δ 13C = −18.3 ± 0.4‰ and δ 15N = 11.2 ± 0.7‰ for adults ( n = 15) and δ 13C = −18.7 ± 0.7‰ and δ 15N = 12.5 ± 1.1‰ for juveniles ( n = 33). These δ 13C values indicate that there was no significant input of C 4 plants in the human diets and this may be associated with the spread of rice agriculture in the Mumun period. Human bone collagen δ 13C and δ 15N values indicate that there was some consumption of marine foods, although the main protein sources were from terrestrial foods. The isotope data demonstrate that the humans at Nukdo had mixed diets that included marine and terrestrial protein, including C 3 plants such as rice. Finally, the isotope results from the juveniles indicate that weaning occurred before the age of 1.5 years in this period.

Clam growth-stage profiles as a measure of harvest intensity and resource management on the central coast of British Columbia

Examination of growth-stage profiles of shells from nine Northwest Coast shell midden sites shows a majority of senile-stage shells at longer-term residential sites and a majority of mature-stage shells at shorter-term encampments. This pattern indicates less intensive harvest in the vicinity of residential sites, which is consistent with management and conservation of resources for anticipated future needs. Consideration of environmental and taphonomic factors does not account for the observed inter-site variability. Shellfish conservation in the vicinity of residential sites is evident for the period of the past 7000 years.

OBSERVATIONS ON THE ARCHAEOLOGY, PALEOENVIRONMENT, AND GEOMORPHOLOGY OF THE PUERTO PEÑASCO AREA OF NORTHERN SONORA, MEXICO

Recent observations and archival research on the archaeology of the Puerto Peñasco area at the northern end of the Gulf of California, Sonora, Mexico, have provided additional insights into the prehistory of the region. The northern Gulf of California has long been recognized as the source of raw marine shell used in the production of shell ornaments by the Hohokam of southern and central Arizona. The most obvious archaeological manifestations in the area are the shell midden sites that occur along the margins of the ocean and estuaries of the region. Based on a small sample of diagnostic flaked stone and ceramic artifacts, a Late Archaic period through Late Ceramic period (Hohokam) use of the area is evident. A small number of independently derived radiocarbon dates appear to support this conclusion. We summarize archaeological, chronometric, environmental, and geomorphic data from the area.

Holocene palaeoecology and floodplain evolution of the Muge tributary, Lower Tagus Basin, Portugal

The lower Muge valley, a tributary of the lower Tagus River (Portugal), features an important archaeological record of Mesolithic shell midden sites. Archaeological research has long assumed that tidally influenced valley floor environments in the immediate locality of the sites provided a rich food resource, attracting Mesolithic settlement. To date there has been little attempt to use palaeoenvironmental records to reconstruct Holocene floodplain evolution in the Lower Tagus valley. The cultivated freshwater lower Muge floodplain is locally underlain by ∼11 m of homogeneous fine-grained sediments and peat, comprising buried floodplain environments contemporary with Mesolithic occupation (∼6200–4800 cal BC). Pollen and foraminifera analyses demonstrate that fine-grained deposition, forced by sea-level rise, commenced ∼6200 cal BC in an estuarine setting. The lower Muge floodplain experienced maximum tidal influence ∼5800–5500 cal BC. Subsequently, sediment supply rates overtook the decreasing rate of sea-level rise and fluvial environments expanded. The pollen record may suggest regional desiccation from ∼5000 cal BC. Estuarine environments disappeared suddenly ∼3800 cal BC when freshwater wetlands were established. Although the initiation of Mesolithic settlement is shown to coincide with the beginning of tidal influence, site abandonment does not match with any major environmental change. Sea-level still stand (∼2600 cal BC) has been linked to valley floor stabilisation and soil formation. Alder floodplain woodland developed prior to ∼230 cal BC and was cleared, probably during Roman times, for agriculture. Renewed deposition after ∼230 cal BC may relate to internal mechanisms or to human impact upon the catchment vegetation.

The palaeogeography of Mesolithic settlement-subsistence and shell midden formation in the Muge valley, Lower Tagus Basin, Portugal

This paper reports the first detailed palaeogeographical analysis of the environmental context of late Mesolithic shell midden sites in the lower Tagus area and focuses on the lower Muge valley, which contains an internationally significant Mesolithic record. The lower Muge valley fill comprises buried estuarine and fluvial environments contemporary with Mesolithic settlement. Holocene environmental and palaeogeographic changes influenced Mesolithic settlement-subsistence and midden accumulation. The sudden appearance of large late Mesolithic shell middens throughout Portugal represents a process of increased visibility and preferential preservation of the archaeological record. Prior to ~6100 cal. BC, aggrading valley floor environments did not occupy the entire width of the present lower Tagus floodplain and any sites located in the early Holocene valley are currently deeply buried. Shell midden occupation on terrace levels followed the establishment of aggrading estuarine environments, containing productive shell beds, near the mouth of the lower Muge valley at ~6100 cal. BC. The critical factors in site choice appear to have been the nearby presence of (i) rich shell resources and (ii) freshwater environments. Long-term site occupation and (semi-)sedentary behaviour was favoured by the local presence, for over 2000 years, of rich resources from estuarine, freshwater and open woodland environments. Site abandonment (~5300—4800 cal. BC) coincided with the regional establishment of an open landscape (~5000 cal. BC) and the contraction of local estuarine environments (~5555—3800 cal. BC). The associated gradual decrease in resources and cultural interaction with the expanding early Neolithic communities may have influenced Mesolithic site abandonment.

Excavations at Walaldé: new light on the settlement of the Middle Senegal Valley by iron-using peoples

Excavation of the five hectare site of Walaldé revealed an occupation by iron-using agropastoralists that began [800–550] cal BC, and continued until [400–200] cal BC. The earliest occupation phase appears to document a period of transitional iron use, with some worked stone in evidence. Smelting and forging slags and tuyeres are present in considerable quantities in the later phase. Copper with the distinctive chemical signature of the Akjoujt mines in Mauritania was also present after 550 cal BC, attesting to trade and interaction over long distances. Other important aspects of the Walaldé sequence include ceramic materials and a series of red ochre burials. Possible cultural affinities with shell midden sites in the Senegal Delta, surface material from the Lac Rkiz region, and pastoralist sites of the ‘Boudhida Culture’ around Nouakchott are discussed. The article concludes with a consideration of Walaldé’s significance to the debate over the origins of iron metallurgy in West Africa.

Spatial Relationships, Dating and Taphonomy of the Human Bone from the Mesolithic site of Cnoc Coig, Oronsay, Argyll, Scotland

This paper examines the spatial distribution of the human bone sample excavated from the Mesolithic shell midden site of Cnoc Coig on Oronsay in the Inner Hebrides, Scotland. Although no burials were recovered the information from the apparently isolated bone finds has been significant. Two types of bone group are distinguished, one that resembles the widely reported ‘loose bone’ phenomenon that is widely recognised from European Mesolithic sites. The other, represented by two bone groups at Cnoc Coig, is, at this time, restricted to western Scotland. It is dominated by hand and foot bones and appears to represent purposive behaviour. We concentrate our discussion on the latter phenomenon and place it within discussion of the nature of the later Mesolithic in western Scotland.

Water views: Water-based survey methods on Cowan Creek, New South Wales

A survey of shell midden sites within the Cowan Creek area, which lies to the north of Sydney, was conducted over a period of five months. The survey design was based upon a site location printout obtained from the New South Wales National Parks and Wildlife Service Aboriginal Heritage Information Management System. Due to the ruggedness of the terrain within the area, the sites were first identified from the water, and GPS was used to verify the coordinates. The location of the sites was then confirmed on foot. During the survey potential habitation sites were also examined, and a total of thirty-eight new sites containing middens, were identified and recorded for inclusion on the site register with National Parks. Recorded site density, as a result of the survey, has increased along Coal and Candle Creek from 0.5 sites /linear km, to 8.5 sites/linear km. Surface examinations of the midden deposits in this area suggest that Trichomya hirsuta andCrassostrea commercialis were strongly favoured by Aboriginal people in the past. The results of the survey indicate that the water-based survey method adopted for the purposes of this project was highly efficient in the location of sites containing middens in Cowan Creek, within a short period of time. The results also indicate that a great deal of this information is being rapidly degraded within the area, with the majority of sites displaying damage due to both natural and anthropogenic influence, despite the protection afforded by inclusion of all of these sites within a National Park.

Environmental change and oyster colonization within the Hudson River estuary linked to Holocene climate

Geophysical mapping and sampling data provide a record of changing environmental and faunal conditions within the Hudson River estuary during the mid- to late Holocene. On the shallow, broad marginal flats of the mesohaline Hudson, fossil oyster beds (Crassostrea virginica) are found exposed on the river bottom and buried by sediment. The shallowest beds are well imaged in chirp sub-bottom and side-scan sonar data and form discrete flow-perpendicular bands, 0.6–1.0 km wide and up to 3 km long, which cover 30% of the river bottom. Radiocarbon-dated sediment cores indicate oysters thrived within two time periods from ~500–2,400 and ~5,600–6,100 cal. years b.p. Sediment and physical property data indicate a changing depositional regime consistent with the oyster chronology. Similar changes in oyster presence are found in local shell midden sites of the Lower Hudson Valley as well as elsewhere along the Atlantic coast, and may reflect climatic controls associated with warm–cool cycles during the Holocene. Oysters flourished during the mid-Holocene warm period, disappeared with the onset of cooler climate at 4,000–5,000 cal. years b.p., and returned during warmer conditions of the late Holocene. The most recent demise of oysters within the Hudson at 500–900 cal. years b.p. may have accompanied the Little Ice Age.