Sea-Level Rise and Subsidence Effects on Gulf Coast Archaeological Site Distributions (original) (raw)
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PloS one, 2017
The impact of changing climate on terrestrial and underwater archaeological sites, historic buildings, and cultural landscapes can be examined through quantitatively-based analyses encompassing large data samples and broad geographic and temporal scales. The Digital Index of North American Archaeology (DINAA) is a multi-institutional collaboration that allows researchers online access to linked heritage data from multiple sources and data sets. The effects of sea-level rise and concomitant human population relocation is examined using a sample from nine states encompassing much of the Gulf and Atlantic coasts of the southeastern United States. A 1 m rise in sea-level will result in the loss of over >13,000 recorded historic and prehistoric archaeological sites, as well as over 1000 locations currently eligible for inclusion on the National Register of Historic Places (NRHP), encompassing archaeological sites, standing structures, and other cultural properties. These numbers incre...
PloS one, 2017
The impact of changing climate on terrestrial and underwater archaeological sites, historic buildings, and cultural landscapes can be examined through quantitatively-based analyses encompassing large data samples and broad geographic and temporal scales. The Digital Index of North American Archaeology (DINAA) is a multi-institutional collaboration that allows researchers online access to linked heritage data from multiple sources and data sets. The effects of sea-level rise and concomitant human population relocation is examined using a sample from nine states encompassing much of the Gulf and Atlantic coasts of the southeastern United States. A 1 m rise in sea-level will result in the loss of over >13,000 recorded historic and prehistoric archaeological sites, as well as over 1000 locations currently eligible for inclusion on the National Register of Historic Places (NRHP), encompassing archaeological sites, standing structures, and other cultural properties. These numbers incre...
Low-gradient coastlines are susceptible to inundation by rising water, but they also promote marsh aggradation that has the potential to keep pace with sea-level rise. Synergies among hydrodynamics, coastal geomorphology, and marsh ecology preclude a simple linear relationship between higher water and shoreline transgression. As an archive of human use of low-gradient coastlines, archaeological data introduce additional mitigating factors, such as landscape alteration, resource extraction, and the cultural value of place. The Lower Suwannee Archaeological Survey (LSAS) is an ongoing effort to document the history of coastal dwelling since the mid-Holocene, when the rate and magnitude of sea-level rise diminished and the northern Gulf coast of Florida transitioned into an aggradational regime. Results of the first six years of the LSAS suggest that multicentury periods of relative stability were punctuated by site abandonment and relocation. Subsistence economies involving the exploitation of oyster and fish, however, were largely unaffected as communities redistributed themselves with changes in shoreline position and estuarine ecology. After A.D. 200, civic-ceremonial centers were established at several locations along the northern Gulf coast, fixing in place not only the infrastructure of daily living (villages), but also that of religious practice, notably cemeteries and ceremonial mounds. Intensified use of coastal resources at this time can be traced to a ritual economy involving large gatherings of people, terraforming, feasting, and the circulation of socially-valued goods. To the extent that religious practices buffered the risks of coastal living, large civic-ceremonial centers, like aggrading marshes, afforded opportunities to “outpace” sea-level rise. On the other hand, centers introduced a permanence to coastal land-use that proved unsustainable in the long term.
Sea Level Rise in Coastal Virginia: Understanding Impacts to Archaeological Resources
Virginia Department of Historic Resources Monograph Series, 2012
Recent and historical changes in sea level within the Chesapeake Bay and along the Atlantic sea coast of Virginia are assessed via the surface geology, the associated flora, and the condition of the vegetation upon a landscape. Alternatively, the wealth of information found at archaeological sites along the Mid Atlantic coastline also provides a means for evaluating site proximity to sea level and can be combined with geologic data to evaluate changes in sea level over the past several thousand years. However, threats to the archaeological record include erosion with site destruction, as well as geochemical alterations and instability issues. Although, erosion and land loss along the Chesapeake Bay is not reflective of sea level rise, the geochemical processes that impact the archaeological record are indicative sea level change. In tandem with field-collected site data, historic coastal survey maps can help us understand the reported magnitudes and rates of recent sea level change. In this report, we use GIS to gauge the potential negative impact to Virginia’s coastal archaeological sites via marine transgression or sea level rise. Our results indicate that 281 of Virginia’s 17,230 sites, which are currently located in the coastal plain, are presently impacted by the geologic processes associated with modern sea level. With only one-foot of additional sea level rise, nearly 500 added sites will be impacted. The resultant data help prioritize the vulnerability of archaeological sites adjacent to Virginia’s coastlines.
Geoarchaeology, 1997
Underwater geoarchaeological research in Apalachee Bay, in the northeastern Gulf of Mexico off northwest Florida, has enabled the reconstruction of portions of the karstcontrolled paleodrainage system, the discovery of several inundated prehistoric archaeological sites, and the exposure of sediments accumulated during the drowning of the continental shelf. Diagnostic artifacts discovered at the sites included chipped stone tools and debitage indicating Paleoindian, Early Archaic, and Middle Archaic occupation. A geoarchaeological model using terrestrial analogs was used to locate and investigate inundated sites. Methods employed include seismic profiling, vibracoring, diver tow surveys, diver collection transects, and induction dredge excavations. We document evidence for sea-level rise, related environmental succession and site formation processes for indundated prehistoric sites in the Apalachee Bay region from approximately 8000 to 6000 yr B.P.
(15) Geological studies of coastal change applied to archaeological settings
Sedimentological and geomorphological theories, models, and field techniques may be used to yield information on the coastal paleogeographies of archaeological sites. Surf ace and subsurf ace reconstructions of late-Quaternary coastal change may be correlated with the historical and archaeological records of an area, thereby clarifying human-environmental interaction and subsistence strategies . This chapter presents several examples of coastal geornorphological and geological studies related to archaeological site settings in the Ame rican mid-Atlantic coastal zone and Aegean Sea area. The concepts and methods can be applied to archaeological coastal-zone exploration worldwide.
Elevation and accretion dynamics at historical plots in the Biloxi Marshes, Mississippi Delta
Estuarine, Coastal and Shelf Science, 2020
The objectives of this study were to examine changes in accretion and elevation change over periods of up to 15 years for the Biloxi marsh complex (BMC) in southeastern Louisiana, part of the Mississippi Deltaic Plain, identify factors affecting accretionary dynamics, and put these findings in the context of ongoing restoration. We present elevation and accretion data from Surface Elevation Table (SET) and feldspar marker horizon sites first established in 2003. The sites were clustered in two areas (East and West) in the central BMC on the eastern edge of the Mississippi delta. Accretion markers were used in conjunction with elevation measurements to calculate shallow subsidence. These data were analyzed along with similar data from nearby Coastwide Reference Monitoring System (CRMS) sites located around the periphery of the BMC. Elevation decreased at the Western sites by − 0.35 ± 0.13 cm/yr, and increased at the Eastern and CRMS sites by 0.40 ± 0.03 cm/yr and 0.72 ± 0.09 cm/yr, respectively. The rate of accretion was similar at the Western (0.49 ± 0.14 cm/yr) and Eastern (0.64 ± 0.07 cm/yr) sites, and over twice as much (1.30 ± 0.11 cm/yr) at the CRMS sites. Shallow subsidence, calculated as the difference between vertical accretion and surface elevation change, was 0.76 ± 0.49 cm/yr at the Western sites, 0.23 ± 0.06 cm/yr at the Eastern sites, and 0.58 ± 0.11 cm/yr at the CRMS sites. These trends are consistent with the observation that sediment is brought in from Chandeleur Sound to the east and is attenuated as deposition occurs across the landscape from east to west, and that levee flank depressions associated with Bayou La Loutre, an abandoned Mississippi River distributary ridge, are causing locally high subsidence in the Western region. Without intervention, these localized areas of the Western region will be submerged within the next several decades at current rates of elevation loss and eustatic sea-level rise, while the Eastern sites and the wetlands on the periphery of the BMC are likely to keep pace with sea level rise well into the second half of this century. These results demonstrate the importance of accurate knowledge of both subsidence and accretionary dynamics in determining coastal wetland sustainability and restoration approaches.
Differential Temporal and Spatial Preservation of Archaeological Sites in a Great Lakes Coastal Zone
American Antiquity, 2012
A systematic assessment of the depositional and postdepositional processes associated with the formation and preservation of the archaeological record has attained increasing importance in regional research design. The increased attention attached to regional taphonomy of sites is largely founded on the need to understand the degree to which the preserved, and recoverable, archaeological record is representative of past site populations, as well as the need to apply the appropriate strategies necessary to discover and assess that part of the record that remains. Such an evaluation is prerequisite to the development of regional field survey strategies and consequently use of regional site data to reconstruct and make inferences about changes in Analysis of regional site taphonomy that incorporates depositional and postdepositional histories has become increasingly important in understanding the nature of preserved site populations and the strategies necessary for their discovery. We applied a systematic archival and field strategy directed at understanding such taphonomic processes in the coastal sand dunes of the northern and eastern Lake Michigan basin, and coupled these with a tactically directed program of OSL, 14C, and AMS dating. We demonstrate that long-term geological processes including lake level variation, episodic dune activation and stabilization, and the long-term effects of postglacial isostatic adjustments have markedly affected the potential for preservation of sites in coastal dune contexts over time and across subregions of the basin. Preservation potential for different time periods in coastal dunes is largely not synchronous with that of southern Michigan floodplains, posing substantial inferential problems. The archaeology of coastal dunes specifically, and coastal zones generally, must be used with extreme caution when cast against archaeological data from landforms with different formation processes and histories. While particularly true for the Great Lakes region, these results have implications for regional research broadly.
Conservation and Management of Archaeological Sites, 2018
The US Middle Atlantic region, known for its rich archaeological record and diverse topographic settings, is experiencing a range of climate change impacts, most notably: sea level rise and coastal erosion in its tidal zones. Documented palaeostratigraphic and palynological studies throughout the region provide a record of late Pleistocene/Holocene environmental response to changing climate, confirming observations from other disciplines that the magnitude of modern impacts exceeds past temporal and spatial patterns. The corresponding impact on archaeological resources is great, requiring a renewed effort to document threatened sites while also working with local and state governments to develop mitigation strategies. The Middle Atlantic Archaeological Conference (MAAC) created the Sea Level Rise and Storm Surge Committee to promote regional partnerships in site impact assessment and mitigation strategies. The network highlights the predicament of archaeology in this time of climate change: accelerated research and discovery in the face of catastrophic loss.
Geological Society of America Bulletin, 2004
Holocene relative sea-level (RSL) curves for the U.S. Gulf Coast are in mutual confl ict, with some characterized by a smooth RSL rise akin to widely accepted eustatic sea-level curves versus others, including several recent ones, that are characterized by a conspicuous "stair-step" pattern with prolonged (millennium-scale) RSL stillstands alternating with rapid (meterscale) rises. In addition, recent work in Texas and Alabama has revitalized the notion of a middle Holocene RSL highstand, estimated at 2 m above present mean sea level. An extensive sampling program in the Mississippi Delta (Louisiana) focused on the collection of basal peats that accumulated during the initial transgression of the pre-existing, consolidated Pleistocene basement. We used stable carbon isotope ratios to demonstrate that many of these samples accumulated in environments affected by frequent saltwater intrusion in the <30 cm zone between mean spring high water and mean sea level, and we selected plant macrofossils that were subjected to AMS 14 C dating. Nearly 30 sea-level index points from a ~20 km 2 study area on the eastern margin of the delta suggest that RSL rise followed a relatively smooth trend for the time interval 8000-3000 cal yr B.P., thus questioning the occurrence of major RSL stillstands alternating with abrupt rises. Given the narrow error envelope defi ned by our data set, any sea-level fl uctuations, if present, would have amplitudes of <1 m. Although a true middle Holocene highstand never occurred in the Mississippi Delta, the high level of detail of our time series enables a rigorous test of this hypothesis. Correction of our data set for a hypothetical tectonic subsidence rate of 1.1 mm yr-1 (assuming a constant subsidence rate compared to the tectonically relatively stable adjacent coast of Texas) leads to sea levels near 2 m above present during the time interval 6000-4000 cal yr B.P. However, this model also implies a RSL position near-2 m around 8000 cal yr B.P., which is inconsistent both with data of this age from Texas, as well as with widely accepted sea-level data from elsewhere. We therefore conclude that a middle Holocene highstand for the U.S. Gulf Coast is highly unlikely, and that the entire area is still responding glacio-isostatically, by means of forebulge collapse, to the melting of the Laurentide Ice Sheet.