A database of Holocene nearshore marine mollusc shell geochemistry from the Northeast Pacific

The shells of marine invertebrates can serve as high-resolution records of oceanographic and atmospheric change through time. In particular, oxygen and carbon isotope analyses of nearshore marine calcifiers that grow by accretion over their lifespans provide seasonal records of environmental and oceanographic conditions. Archaeological shell middens generated by Indigenous communities along the Northeast Pacific coast contain shells harvested over multiple seasons for millennia. These shell middens, as well as analyses of archival and modern shells, have the potential to provide multi-site, seasonal archives of nearshore conditions throughout the Holocene. A significant volume of oxygen and carbon isotope data from archaeological shells exists, yet is separately published in archaeological, geochemical, and paleoceanographic journals and has not been comprehensively analyzed to examine oceanographic change over time. Here, we compiled a database of previously published oxygen and carbon isotope data from archaeological, archival, and modern marine molluscs from the North American coast of the Northeast Pacific (32° N to 50° N). This database includes oxygen and carbon isotope data from over 550 modern, archaeological, and sub-fossil shells from 8880 years before present (BP) to the present, from which there are 4,845 total δ13C and 5,071 total δ18O measurements. Shell dating and sampling strategies vary among studies (1–118 samples per shell) and vary significantly by journal discipline. Data are from various bivalves and gastropod species, with Mytilus spp. being the most commonly analyzed taxon. This novel database can be used to investigate changes in nearshore sea surface conditions including warm-cool oscillations, heat waves, and upwelling intensity, and provides nearshore calcite δ13C and δ18O values that can be compared to the vast collections of offshore foraminifera calcite δ13C and δ18O data from marine sediment cores. By utilizing previously published geochemical data from midden and museum shells rather than sampling new specimens, future scientific research can reduce or omit the alteration or destruction of culturally valued specimens and sites. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.932671 (Palmer et al., 2021).

The Shell Midden Sites of Senegambia

There are hundreds of shell midden sites along the Senegambian coastline. The shell middens were first formed during an eustatic event known as the Nouakchottien marine transgression (6,800–4,000 bp). During that marine transgression, the sea shoreline was pushed back hundreds of miles in the interior. This engendered the flourishing of malacological fauna and several fish species. As a result of this, several natural shell midden were formed. From the Late Stone Age to the 2nd millennium ce, populations exploited the aquatic fauna, which resulted in the formation of anthropogenic shell middens. The littoral where these shell middens are found is divided into three archaeological culture areas. Archaeological excavations at some of those sites, such as Khant and Dioron Boumak, have shed light on the nature of the material culture, subsistence activities, and the cultural history in these areas. Research at Soukouta has added new data on iron technology to understanding of the shell middens culture. These findings have also called into question the division of Senegambian prehistory into four distinct cultural areas known as aires culturelles.

NEW MARINE RESERVOIR CORRECTION VALUES (ΔR) APPLICABLE TO DATES ON NEOLITHIC SHELLS FROM THE SOUTH COAST OF KOREA

ABSTRACT Shells from Neolithic shell midden sites have been routinely dated in Korea, but they have not been calibrated based on the correction values (ΔR) for the marine reservoir effect (MRE). A lack of proper calibration has left dates on shells incomparable to those on terrestrial samples, and thus unusable in building the chronological sequence of shell middens. Here, we report the two new ΔR values of a pre-bomb (pre-1950) blue mussel from the south coast. We applied the two new and the two previously reported ΔR values to the three dates on marine shells from the Bibongri shell midden in southeastern Korea. Our ΔR adjusted calibration and the comparison to dates on charcoal and bone remains clarify an ambiguity in the stratigraphy and the Early Neolithic chronology at Bibongri. Our contribution is to provide the ΔR values that can be further applied to other Neolithic shell middens along the south coast.

Shell Middens and Coastal Prehistory

Shell middens, the residues of shellfish gathering, consumption, and disposal in the past, have attracted the attention of archaeologists for more than one hundred and fifty years. Although there has been a tendency to view these sites as simply waste heaps, it is increasingly clear that this is usually not the case and that, sometimes, spatially meaningful arrangements of domestic debris of all kinds (fireplaces, artifacts, cooking and sleeping areas) are recognizable if excavations are sensitive enough. Some issues are as relevant and as intransigent as they have been from the beginning: Are they really food waste or could they be natural shell accumulations? Were people living at these sites or are they simply large piles of waste resulting from shell processing? In what ways and how fast did the middens accumulate? How are shell middens related to other archaeological sites inland, contemporary but without shell food waste? Because shell middens are found on all continents except Antarctica and throughout the Holocene time period (the last twelve thousand years), the literature on their excavation and interpretation is enormous and illustrates that archaeologists worldwide engage similarly with counting, measuring, weighing the shellfish, and associated faunal and artifactual remains from these sites. Often, the research involves developing proxies for the kinds of invisible but interesting aspects of the lives of the shellfish gatherers, such as: How many people lived here? How long did people stay at this site? Why did they come when they did and leave when they did? Where else did people live? While Holocene shell middens are ubiquitous, it is also clear that Pleistocene shell middens, while fairly widespread, are found more commonly in coastal areas where early modern humans have dispersed early in their migrations across the globe. It is likely that these traces, in Africa, in Europe, in island South-East Asia and Australia, and along the shores of western North America mark the routes whereby our earliest modern human ancestors peopled the world.

Site Context and the Spatial Organization of a Late Holocene Coastal Hunter-Gatherer Campsite in North-Central Chile, South America

We explored the site context of a late Holocene shell midden on the coast of Los Vilos in north-central Chile (31°51′ S, South America) to better understand the spatial organization of short-term, small-sized hunter-gatherer campsites. The Dunas de Agua Amarilla (LV 007) site comprises 14 separate surf clam refuse deposits. Extensive stratigraphic excavations of the shell middens and the areas free of residue allowed interpretation of potential activity areas bounded by hearths, the shell middens, and a possible dwelling space. Late Holocene campsites in the area correspond to brief occupational events framed within littoral residential mobility, in which predictable coastal resources became a staple for groups residing and circulating over long periods in the area. Data on shell midden composition and the spatial distribution of site features shed light on the organizational dynamics of dwelling and activity spaces of coastal hunter-gatherers of the South Pacific.