Although shell middens and mounds often occupy the same intertidal spaces as coastal wetlands, biophysical interactions between these cultural features and wetlands are under-investigated. To this end, our geoarchaeological and zooarchaeological research at three coastal archaeological sites within the Tampa Bay Estuary, USA, sought to understand the interactions between shell-bearing sites, sea-level rise, storms, and migrating wetland habitats. Percussion core transects document the accretion of mangrove peat atop intact shell midden, illustrating the ability of mangrove forests to encroach shell midden and preserve cultural material below. Landward wetland deposits are thicker and muddier than those along the seaward margin of the sites, suggesting that shell-bearing sites attenuate wave energy much like other shoreline stabilization structures. Differences in sedimentology, stratigraphy, and invertebrate species compositions highlight the variability in storm impacts between sites. Storm-driven depositional events are identified by medium-to-fine sand beds with high densities of fragmented shell and small intertidal zone snails. Geospatial analyses indicate that wetland encroachment is already occurring at 247 archaeological sites within the Tampa Bay Estuary. Approximately 100 additional archaeological sites currently located in upland habitats may provide topographic relief for migrating coastal wetlands in the future. We contend that shell middens and mounds constructed by Indigenous peoples are important components within estuarine mosaics, as they have been for millennia. We advocate for further collaboration between archaeologists and estuary managers and the inclusion of descendant communities to co-manage the future of their past.
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This content will become publicly available on September 1, 2024
Geoarchaeology and Coastal Morphodynamics of Harbor Key (8MA15): Indigenous Persistence at a Partially Inundated Native Shell Mound Complex in Tampa Bay, Florida
Applying a coastal-geoarchaeological approach, we synthesize stratigraphic, sedimentological, mollusk-zooarchaeological, and radiometric datasets from recent excavations and sediment coring at Harbor Key (8MA15)—a shell-terraformed Native mound complex within Tampa Bay, on the central peninsular Gulf Coast of Florida. We significantly revise the chronological understanding of the site and place it among the relatively few early civic-ceremonial centers in the region. Analyses of submound contexts revealed that the early first millennium mound center was constructed atop a platform of sand and ex situ cultural shell deposits that were reworked during ancient storm landfalls around 2000 BP. We situate Harbor Key within a seascape-scale stratigraphic and paleoenvironmental framework and show that the shellworks comprise an artificial barrier protecting the leeward estuary basin (and productive inshore wetlands) from high-energy conditions of the open bay and swells from the Gulf of Mexico. The sedimentary and archaeological records attest to the long-term history of morphodynamic interaction between coastal processes and Indigenous shell terraforming in the region and suggest that early first millennium mound building in Tampa Bay was tied to the recognition and reuse of antecedent shellworks and the persistent management of encompassing cultural seascapes.
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- Award ID(s):
- 2024397
- NSF-PAR ID:
- 10462227
- Date Published:
- Journal Name:
- American Antiquity
- ISSN:
- 0002-7316
- Page Range / eLocation ID:
- 1 to 23
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Saltmarsh plots were located 20-25 m away from any mangrove trees and into the J. roemerianus zone (i.e., landward from the mangrove-marsh interface). Plot pairs were coarsely similar in geomorphic setting, as all were located on the Gulf of Mexico coastline, rather than within major sheltering formations like Tampa Bay, and all plot pairs fit the tide-dominated domain of the Woodroffe classification (Woodroffe, 2002, "Coasts: Form, Process and Evolution", Cambridge University Press), given their conspicuous semi-diurnal tides. There was nevertheless some geomorphic variation, as some plot pairs were directly open to the Gulf of Mexico while others sat behind keys and spits or along small tidal creeks. Our use of a plot-pair approach is intended to control for this geomorphic variation. 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