EXAMINING THE INTERACTION OF HOLOCENE SEA LEVEL RISE, FLUVIAL AND ESTUARY PROCESSES, AND INDIGENOUS OCCUPATION AT THE GRANNIS ISLAND ARCHAEOLOGICAL SITE IN NEW HAVEN, CT

Understanding site formation processes and localized geologic stratigraphy is an essential aspect of geoarchaeological investigations. In this study, we utilize sediment vibracores to enhance the developing archaeological interpretation of late Holocene human occupation on Grannis Island in New Haven, CT. The ‘island’ sits along the southern bank of the Quinnipiac River, and serves as a relict of early post-glacial deltaic deposits that once dammed the valley. As an archaeological site, Grannis Island also demonstrates the relationship that local indigenous populations have had with Long Island Sound for millennia. Excavations and ongoing research since the 1940s produced diagnostic lithic artifacts spanning the Middle Archaic through the Late Woodland period, in addition to a diverse faunal assemblage, hearth features, and an extensive shell midden extending across the island. This year, we collected nine sediment cores between 1-6 meters in depth across the terrestrial island and adjacent estuary to better understand the landform’s transformative geomorphology throughout the Holocene. Cores were described, photographed, and continued through a sequence of pXRF for elemental analysis, LOI for organic content, grain size analysis, and radiocarbon dating. Uncalibrated results range as far back as 3,329 B.P in estuarine sediments and 10,988 B.P terrestrially. The produced suite of radiocarbon dates was used to build a calibrated age-depth model of estuarine sediment accumulation adjacent to the island. Overall, these techniques contribute to the development of interpretive models illustrating the site's formation and subsequent transformation through time. With over ten distinct units, the sediment cores showcase the diversity and sensitivity of geologic changes as a consequence of late Pleistocene deglaciation, fluvial erosion, sea level rise, and subsequent human activity.