An official website of the United States government
This study presents preliminary results from recent bathymetric LiDAR-guided surveys of submerged archaeological landscapes in the Apalachee Bay off the coast of Florida. We show how bathymetric LiDAR can re-identify previously recorded archaeological sites and identify new cultural deposits at shallow depths and help aid SCUBA surveys of submerged environments. While most prior archaeological applications of bathymetric LiDAR have focused on shipwrecks and historic era sites, our case study demonstrates that bathymetric LiDAR is capable of detecting Holocene and Pleistocene era archaeological sites as well. Detecting and eventually characterizing these ancient deposits will greatly expand our understanding of settlement trends when sea levels were lower and may provide insights into how some of the earliest coastal populations adapted to this novel and changing environment. Our SCUBA surveys also elucidate the impact of local environmental conditions of the applicability of deploying bathymetric LiDAR; specifically, eel grass cover does not hinder LiDAR capabilities, while high rates of sedimentation greatly reduce success in identifying archaeological deposits. Overall, our results show promise in the future of applying remote sensing to study shallow submerged archaeological landscapes, which can help improve our understanding of human–environment dynamics prior to and during periods of sea level change.
more »
« less
Bathymetric LiDAR and Semi‐Automated Feature Extraction Assist Underwater Archaeological Surveys
ABSTRACT Critical data concerning key developments in global human history now lie submerged on continental shelves where investigations confront significant challenges. Whereas underwater excavations and surveys are expensive and weather dependent and require specialized training and equipment, remote sensing methods can improve chances for success offshore. A refinement in one method, a semi‐automated analysis protocol that can help to identify Pleistocene and Holocene era archaeological deposits in bathymetric LiDAR datasets, is presented here. This method employs contour mapping to identify potential archaeological features in shallow water environments in Apalachee Bay, Florida. This method successfully re‐identified multiple previously recorded archaeological sites in the study region and detected at least four previously undocumented archaeological sites. These results suggest that this procedure can expand on methods to identify and record submerged archaeological deposits in sediment‐starved, shallow‐water environments.
more »
« less
- Award ID(s):
- 2203789
- PAR ID:
- 10513867
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Archaeological Prospection
- Volume:
- 31
- Issue:
- 2
- ISSN:
- 1075-2196
- Format(s):
- Medium: X Size: p. 171-186
- Size(s):
- p. 171-186
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Evidence of ancient Maya exploitation of salt, other marine resources, settlement, and sea trade is hidden in flooded mangrove landscapes on the cays, mainland, and in shallow offshore locations on the south coast of Belize. This paper includes a discussion of the coastal economy from the Middle Preclassic through the Postclassic periods (600 B.C.-A.D. 1500). Data from sites discovered and excavated since 1982 in the coastal area of the Port Honduras and Paynes Creek National Park support a model of coastal reliance marine resources and tree crops. The need for a regular supply of coastal salt to inland cities may have expanded the market for other marine resources. Obsidian imported from volcanic highlands documents long-distance trade throughout prehistory in the area. The island of Wild Cane Cay expanded its role in long-distance coastal trade after the abandonment of inland cities in southern Belize at the end of the Classic period. Inundation of the region documented from the depths of radiocarbon-dated archaeological deposits below the water table and from a sediment core indicates sea-level rise of at least 1m that submerged the coastal sites. The waterlogged deposits provided an ideal matrix for preservation of vertebrate material at Wild Cane Cay. The red mangrove (Rhizophora mangle) peat below the sea floor in a shallow lagoon preserved wooden buildings.more » « less
-
Characterizing the degree of disturbance in archaeological deposits is critically important for archaeologists assessing foraging strategies, environmental conditions, or behavior patterns of ancient human groups. Qualitative techniques (e.g. micromorphology analysis) have previously been applied to assess the degree of disturbance (age-mixing) in archaeological sites; however, quantitative dating of material in the sites provides a more robust assessment of potential age-mixing. Unfortunately, because of budget constraints, archaeologists are frequently forced to rely on few quantitative age dates for an assemblage, thus obfuscating the signal of age-mixing of the deposit. The development of an affordable and rapid carbonate-target accelerator mass spectrometry (AMS) radiocarbon (14C) dating method provides a cost-effective way to retrieve more quantitative dates from carbonate material in archaeological assemblages to assess the degree of age-mixing in the deposit. This study tests this new technique and dates numerous harvested marine limpet shells from archaeological sites in the Canary Islands to determine whether there is multidecadal to multicentennial age-mixing. A total of 58 shells retrieved from six sites and three islands yielded uncalibrated radiocarbon ages ranging from 2265 ± 40 to 765 ± 35 BP, coinciding with the time of prehistoric human occupation in these islands. While most shells from the same stratum showed statistically equivalent ages, in some cases we detected age ranges that exceeded the imprecisions from analytical errors. This investigation is one of the first to quantitatively illustrate that shells retrieved from depth intervals without evident stratigraphic disturbance do not always contain contemporaneous remains and, therefore, dating each specimen is valuable for developing further paleoclimatic and paleoanthropological inferences. This study presents the first report of carbonate-target14C ages from archaeological shell middens, and suggests that this novel radiocarbon methodology can be applied to these sites, thus allowing the generation of a more comprehensive chronology.more » « less
-
Abstract Understanding and attributing changes to water quality is essential to the study and management of coastal ecosystems and the ecological functions they sustain (e.g., primary productivity, predation, and submerged aquatic vegetation growth). However, describing patterns of water clarity—a key aspect of water quality—over meaningful scales in space and time is challenged by high spatial and temporal variability due to natural and anthropogenic processes. Regionally tuned satellite algorithms can provide a more complete understanding of coastal water clarity changes and drivers. In this study, we used open‐access satellite data and low‐cost in situ methods to improve estimates of water clarity in an optically complex coastal water body. Specifically, we created a remote sensing water clarity product by compiling Landsat‐8 and Sentinel‐2 reflectance data with long‐term Secchi depth measurements at 12 sites over 8 years in a shallow turbid coastal lagoon system in Virginia, USA. Our satellite‐based model explained ∼33% of the variation in in situ water clarity. Our approach increases the spatiotemporal coverage of in situ water clarity data and improves estimates from bio‐optical algorithms that overpredicted water clarity. This could lead to a better understanding of water clarity changes and drivers to better predict how water quality will change in the future.more » « less
-
Abstract The obsidian dating method converts the quantity of diffused molecular water within a near‐surface hydration layer to elapsed time using an experimentally derived diffusion coefficient predicted from the structural water content of the glass. Infrared spectroscopic transmission measurements on transparent archaeological samples record vibrational responses of water bands in the near‐infrared region, permitting determination of structural water content (OH), and the amount of diffused ambient water (H2O). In this application, the H2O water band at 5200 cm−1is measured directly. The accuracy of the approach is assessed by an evaluation of the precision of each contributing variable. The new protocol is evaluated using obsidian artifacts from radiocarbon‐dated deposits at Salamanca Cave in Argentina.more » « less
