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1. Human–environment interactions at Ta'ab Nuk Na, a submerged Maya salt works site in Belize

   https://doi.org/10.1017/S0956536123000196  

   Foster, Cheryl M; McKillop, Heather; Sills, E Cory (August 2023, Ancient Mesoamerica)

   Abstract Sea-level rise and settlement are investigated at Ta'ab Nuk Na, an ancient Maya salt works in Belize, by examining samples from wooden posts and marine sediment. The samples included Post 145 of Building B and the Nunavut beam, along with marine sediment columns cut from beside both wooden posts. The sediment columns were sampled at 2 cm intervals. Loss-on ignition confirmed the presence of organic material. Identifying the organic content involved removing nonorganic material from the sediment and sorting the organic material under magnification. This procedure established that most of the organic material was red mangrove (Rhizophora mangle). Red mangroves tolerate salt water, but under conditions of sea-level rise, the plants grow vertically to keep their leaves above water. Sediment, leaves, and detritus trapped in the prop roots form mangrove peat, which serves as a proxy for sea-level rise. AMS dating of fine red mangrove roots determined that the local sea levels rose at Ta'ab Nuk Na throughout the Late Classic period and continued into the Postclassic period. Radiocarbon dates obtained from the wood-post samples yielded Late Classic–period dates. Comparing the radiocarbon dates from the wooden posts and the sediment core samples determined that the site was abandoned before the rising seas flooded the area. Evidently, sea-level rise did not play a role in site abandonment. 

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2. FOCUSING ON INDIVIDUAL WOODEN BUILDINGS REVEALS CHANGES IN THE LATE TO TERMINAL CLASSIC ECONOMY AT THE PAYNES CREEK SALT WORKS

   McKillop, Heather; Sills, E Cory (June 2023, Research Reports in Belizean Archaeology)

   Preservation of wooden building posts in red mangrove (Rhizophora mangle) peat below the sea floor at the Paynes Creek Salt Works in southern Belize provides a rare opportunity to study pole and thatch buildings that were likely the dominant construction in the Maya area in prehistory. In 2020 and 2021, when field research at the salt works was not possible due to the covid pandemic, individual wooden buildings at two of the largest sites, Ek Way Nal and Ta’ab Nuk Na, were radiocarbon dated. The dates indicate that the buildings were constructed at different times. Associated artifacts reveal both residences and salt kitchens at both sites and that production began earlier at Ta’ab Nuk Na and ended later at Ek Way Nal. Identification of tree species used in building construction at Ek Way Nal indicates the salt workers selected useful trees and did not overuse the environment. 

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3. Flooded mangrove landscapes hide ancient Maya coastal sites in Belize

   https://doi.org/10.1080/15564894.2022.2163323  

   McKillop, Heather I (February 2023, The Journal of Island and Coastal Archaeology)

   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. 

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4. Sea-level rise and settlement at Ek Way Nal: Coring the past

   Foster, Cher; McKillop, Heather; Sills, E Cory (July 2023, Research reports in Belizean archaeology)

   Excavations in the spring and summer of 2022 were carried out at the underwater ancient Maya salt work of Ek Way Nal in Punta Ycacos Lagoon, Paynes Creek National Park, Belize. Ek Way Nal provided salt to the ancient Maya during the Late and Terminal Classic periods (600-900 C.E.). In additional to excavations in buildings at the site, a 1 X 2 m unit was excavated to extract a sediment column for examining the relationship between the ancient Maya settlement at Ek Way Nal and sea-level rise. In this article, the excavations, extraction of the sediment column, and processing it for laboratory analyses are described. Field observations are discussed. Fine red mangrove root (Rhizophora mangle) and charcoal samples were extracted from the sediment column for radiocarbon dating. The results from the datum core excavation indicate that sea-level rise occurred before, during, and after the ancient Maya occupation at Ek Way Nal. 

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5. IMPLICATIONS OF SINGLE-STEP GRAPHITIZATION FOR RECONSTRUCTING LATE HOLOCENE RELATIVE SEA-LEVEL USING RADIOCARBON-DATED ORGANIC COASTAL SEDIMENT

   https://doi.org/10.1017/RDC.2022.55  

   Sefton, Juliet P; Kemp, Andrew C; Elder, Kathryn L; Hansman, Roberta L; Roberts, Mark L (October 2022, Radiocarbon)

   ABSTRACT Late Holocene relative sea-level reconstructions are commonly generated using proxies preserved in salt-marsh and mangrove sediment. These depositional environments provide abundant material for radiocarbon dating in the form of identifiable macrofossils (salt marshes) and bulk organic sediment (mangroves). We explore if single-step graphitization of these samples in preparation for radiocarbon dating can increase the number and temporal resolution of relative sea-level reconstructions without a corresponding increase in cost. Dating of salt-marsh macrofossils from the northeastern United States and bulk mangrove sediment from the Federated States of Micronesia indicates that single-step graphitization generates radiocarbon ages that are indistinguishable from replicates prepared using traditional graphitization, but with a modest increase in error (mean/maximum of 6.25/15 additional 14 C yr for salt-marsh macrofossils). Low 12 C currents measured on bulk mangrove sediment following single-step graphitization likely render them unreliable despite their apparent accuracy. Simulated chronologies for six salt-marsh cores indicate that having twice as many radiocarbon dates (since single-step graphitization costs ∼50% of traditional graphitization) results in narrower confidence intervals for sample age estimated by age-depth models when the additional error from the single-step method is less than ∼50 14 C yr (∼30 14 C yr if the chronology also utilizes historical age markers). Since these thresholds are greater than our empirical estimates of the additional error, we conclude that adopting single-step graphitization for radiocarbon measurements on plant macrofossils is likely to increase precision of age-depth models by more than 20/10% (without/with historical age markers). This improvement can be implemented without additional cost. 

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