Accelerator Mass Spectrometry Dates Research Articles

Radiocarbon dates from Curaçao’s oldest Archaic site extend earliest island settlement to ca. 5700 cal BP

Due to its proximity to coastal South America and settlement during the early phase of insular Caribbean occupation, Curaçao’s archaeological record offers potential evidence for early overwater exploration and regional interaction. Here, we report new accelerator mass spectrometry (AMS) dates on charcoal from C-1426 at Saliña Sint Marie, an Archaic rockshelter site that extends Curaçao’s occupation back to 5735–5600 cal BP, some 290–850 years earlier than the established settlement chronology. This finding makes the C-1426 rockshelter Curaçao’s earliest known archaeological site and among the oldest in the insular Caribbean. We describe the site and the archaeological context of dating and conclude by considering the implications of Curaçao’s revised occupation chronology for initial Caribbean settlement.

MIGRATIONS AND CULTURAL EVOLUTION IN THE LIGHT OF RADIOCARBON DATING OF BRONZE AGE SITES IN THE SOUTHERN URALS

ABSTRACT This research aims to contribute to our knowledge of the chronology of the main cultural entities of the Bronze Age in the Southern Urals. The objectives of this work include the verification of earlier conclusions regarding individual sites, expanding the date series for the key cultures with reliable dates, and creating reference series for the Bayesian modeling of key archaeological sites. Thirty-two samples were selected from reliable contexts. They reflect seven different cultural traditions of the 2nd millennium calBC (Sintashta, Srubnaya, Alakul, Fedorovka, Cherkaskul, Final Bronze Age1, Transition to Early Iron Age2). Collagen (human and domestic animal bones), charcoal, and wood samples were used for radiocarbon dating. Pairs of different-type samples (human bone – animal bone, animal bone – charcoal) were obtained for the same undisturbed burial and the building floor at the time of its abandonment. The data and the composition of δ15N and δ13C isotopes allow the new dates to be considered reliable. Furthermore, the new results do not conflict with the previously obtained accelerator mass spectrometry (AMS) dates. Determining boundary intervals for the main cultures of the Andronovo cultural community (Alakul and Fedorovka) resulted in statistically reliable conclusions on their relationship. The Alakul culture appeared earlier than the Fedorovka culture. The latter has a migratory origin in the Southern Urals. The two traditions have a long history of interaction, but the Alakul culture ending earlier. The series of dates for the Final Bronze Age, divided into two sub-periods, has been significantly expanded. Bayesian modeling of the chronology of the stratified settlement Sintashta II (Levoberezhnoe) made it possible to determine the intervals of the main phases of its history: 2004–1852 calBC (Sintashta culture) and 1410–1170 calBC (Final Bronze Age). Intermediate Cherkaskul phase is represented by a single date (1731–1541 cal BC).

NEW HUMAN BONE RADIOCARBON DATES FROM THE ROMAN PERIOD–MIGRATION PERIOD LITHUANIAN CEMETERIES

ABSTRACTA set (n = 37) of new human bone radiocarbon accelerator mass spectrometry (14C AMS) dates from 11 Lithuanian Late Roman Period–Migration Period cemeteries is presented and discussed in the light of the established schemes of archaeological chronology. The focus of the paper is on the burials of the military and social elite, which indicate the emergence of new cultural traditions in E–S and W–Central Lithuania or the immigration that took place during this time. The 14C dates allow us to suggest corrections to the dominant chronological pattern of cultural development in the region.

THE YAKUT BRANCH OF Y-CHROMOSOME AS A PART OF THE HAPLOGROUP N-M2016

Based on the massive parallel sequencing, phylogenetic tree of the Y-chromosomal haplogroup N-M2016 was built. The branch N-M1982 of Yakut-Sakha men majority is located on the tree. The ages of tree branching nodes are estimated. Time to the most recent common ancestor (TMRCA) 970 ± 210 years BP (“present” defined as AD 1950) of one of the main Yakut male lineages N-M1991 is confirmed by accelerator mass spectrometry dating of a sample of the ancient man Yana Young [1] who died about 766 yBP. A sharp increase in the number of Yakut-Sakha ancestors observed on the Yakut branch N-M1982, began from 1320 ± 100 AD. Age of the population explosion is consistent with the radiocarbon dating of the Kulun-Atakh archaeological culture sites.

Neogene and Quaternary reef terraces of Mangaia, Rarotonga and Aitutaki (southern Cook Islands, South Pacific) revisited: gauges of sea-level change and island uplift?

New sedimentological data of facies and diagenesis as well as chronological data including strontium (87Sr/86Sr)-isotope ratios and uranium (U)-series dating, radiocarbon (14C) accelerator mass spectrometry (AMS) dating and biostratigraphy from elevated reef terraces (makatea) in the southern Cook Islands of Mangaia, Rarotonga and Aitutaki contribute to controversial discussions regarding age and sea-level relationships of these occurrences during the Neogene and Quaternary. The oldest limestones of the uplifted makatea island of Mangaia include reef-related facies which are mid-Miocene in age, based on new Sr-isotope and biostratigraphical data. In between these older deposits and the lowest coastal reef terrace of marine isotope stage (MIS) 5e, various older Pleistocene reef-related facies were identified. Based on Sr-isotope ratios, these were deposited during earlier Pleistocene highstands (as old as 2.28 Ma). Rare reef terraces on Rarotonga belong to the Plio-Pleistocene and the late Miocene, according to 87Sr/86Sr ratios. The late Miocene age is enigmatic as it exceeds the age of subaerially exposed volcanic rocks of Rarotonga island. The fossil reef could have formed on an older submarine volcanic high that was later displaced by younger volcanism to its present position, or the Sr-age could be too old due to diagenetic resetting. The Plio-Pleistocene Rarotonga reef terraces are overlain irregularly by Holocene reef deposits that are interpreted as storm rubble. Reef terraces on Aitutaki represent evidence of a higher-than-present (up to 1 m) sea-level during the late Holocene, based on 14C AMS age data. They are very similar to elevated late Holocene reefs of adjacent French Polynesia with regard to composition, elevation and age.

RADIOCARBON DATING ROZHOK I, A MIDDLE PALEOLITHIC OPEN-AIR SITE IN SOUTHERN RUSSIA

ABSTRACTSamples of bone and teeth from the Middle Paleolithic open-air site of Rozhok I, located on the Gulf of Taganrog, were dated by radiocarbon (14C). We obtained 26 accelerator mass spectrometry (AMS) dates on a large sample of nonhuman bone and teeth recovered by N. D. Praslov during 1961–1962 from 5 of the 6 occupation horizons at Rozhok I. Two rigorous pretreatment methods were applied to the samples: ultra-filtration and XAD resin. The 14C ages from the uppermost two layers (Horizons 1 and 2) are infinite with the exception of one age near the limit of the 14C method. By contrast, the dates from Horizon 3 and the two lowermost layers (Horizons 5 and 6) are all finite ages and some are less than 45,000 BP (uncalibrated). While there is evidence of some post-depositional disturbance, there is no evidence of a stratigraphic reversal of the cultural layers. The simplest explanation for the pattern is that bones and teeth in the lower layers have been contaminated by groundwater containing young carbon. We conclude that Rozhok I probably antedates 50,000 cal BP and is beyond the range of 14C dating.

Prehistoric landscapes, humans and ostriches: highlighting geoarchaeological issues in the Tapi Basin of Maharashtra (west-central India) – a multidisciplinary approach

Abstract The formal beginning of geoarchaeology in India can be traced back to 1863 when the first palaeolith was documented and collected by Robert Bruce Foote in Tamil Nadu and later described in a detailed geological context. Today, various geological tools such as geospatial analytical tools are available to provide extra mileage to geoarchaeological investigations. They supplement field evidence and enable researchers to display, manipulate, and model geological data and the associated archaeological evidence. The present paper attempts to summarize the current status of understanding of the Quaternary geoarchaeology of the Tapi River basin in west-central India. The aspects considered include geomorphology, landform evolution, morphometric parameters, relationships between climate and basin evolution and Palaeolithic and Mesolithic evidence. This present study uses Landsat imagery, locational data, Survey of India topographic sheets and Shuttle Radar Topography Mission data in ArcGIS software. The study is the first comprehensive attempt to summarize the issue of prehistoric human adaptations (dominated mainly by Late Pleistocene evidence) through changing environments, with an assumption that the two occurred in synchronization. Another assumption is that the reported lithic and fossil sites and the surrounding areas have preserved signatures of original landforms and sedimentary contexts. Through these perspectives and visual integration of topography, drainage networks and Landsat image parameters in a Geographic Information System platform, along with other variable field inputs, a testable hypothetical model of the Quaternary evolution of Central Tapi valley is proposed. Additionally, an accelerator mass spectrometry (AMS) date of 47 145 cal BP for a newly discovered ostrich eggshell fragment from Sakegaon near Bhusawal is presented and its palaeoanthropological implications are discussed. Altogether, our observations from the study area, such as an expansion of land use from the Acheulean onwards, signatures of arid phases and the oldest reported ostrich eggshell, warrant further detailed multidisciplinary research. An in-depth understanding of the first-to-last occurrences of ostriches in the region and comprehensive picture of their pan-South Asian distribution in general will help address the issue of prehistoric human adaptations through changing environments.

New AMS dates for the Middle Iron Age in the Mapungubwe landscape

Research in the Limpopo Valley has documented over 500 Middle Iron Age sites (AD 900–1320) relevant to the origins of Mapungubwe – the capital of the first indigenous state in southern Africa. Fifteen new accelerator mass spectrometry (AMS) dates from 11 of these archaeological sites establish the boundaries of the ceramic facies that form the culture-history framework for such diverse topics as land use, ethnic stratification, population dynamics and rainfall fluctuations. Mapungubwe was abandoned at about AD 1320.Significance:
 
 Because Mapungubwe developed relatively recently (circa AD 1200), it can clarify the origins of older states.
 Environmental factors such as droughts, along with agriculture and trade, played a role in the abandonment of Mapungubwe.

RADIOCARBON DATING APPLIED TO PREHISPANIC TERRITORIAL DYNAMICS AT EL MAYE, IXMIQUILPAN, HIDALGO, MEXICO

ABSTRACTEl Maye is a community located in the municipality of Ixmiquilpan, Hidalgo, in the central region of Mexico. During the late Postclassic period (1350–1521 AD), the Aztecs controlled the area through the establishment of a dual-headed system, one part belonging to the Aztec government and the other to the local government. El Maye was the local government center for the Ixmiquilpan territory under the Aztec domain. The residential units of El Maye archaeological site were constructed in 6 different occupational phases, with the presence of large rooms, stucco floors and walls, offerings, and a variety of ceramics belonging to the late Aztec III ceramic period (1400–1520 AD). The Axis Project of the Mezquital Valley (PEVM-ENAH) and the Accelerator Mass Spectrometry Laboratory (LEMA-UNAM) have undertaken a collaborative study of the El Maye site by performing absolute radiocarbon accelerator mass spectrometry (14C AMS) dating. For a better understanding of the emergence and development of El Maye, a series of AMS 14C dates of charcoal and bone samples recovered from different stratigraphic levels, was performed. This allowed us to locate the occupation of the site between 1320 and 1625 cal AD.

THE EXTERMINATION OF THE ANCIENT RUSSIAN CITY OF YAROSLAVL AT THE BEGINNING OF THE 13TH CENTURY: THE LONG JOURNEY TO EXACT DATING

ABSTRACTThis paper raises methodological issues of radiocarbon (14C) dating of historical events based on data obtained during the excavations of the Russian medieval city of Yaroslavl. The city is of special interest to our study because of the precise time of its destruction by troops of Batu Khan mentioned in chronicles—the winter of 1238. To date in Yaroslavl, researchers have discovered 9 mass burials of citizens and domestic animals buried sometime after the massacre by the Mongols. Mass burials of people alongside animals in a common grave and outside of the cemetery, in violation of Christian traditions, are not typical of medieval Russia and are a sign of a military catastrophe. To test this hypothesis, we dated a total of 65 samples representing all 9 mass burials. A Bayesian chronological model of the accelerator mass spectrometry (AMS) dates narrowed the interval to the range of 1197–1280 cal AD, with the mean age of 1239 AD, consistent with the hypothesis that the studied mass burials of citizens and livestock are related to the capture of the city by the army of Batu Khan.

New evidence for early human habitation in the Nyingchi Region, Southeast Tibetan Plateau

The lack of archaeological work has long impeded our understanding of prehistoric and historical human inhabitation and East-West interactions on the southeastern Tibetan Plateau (TP). In this study, we conducted a series of systematic archaeological investigations in the Nyingchi region, on the southeastern TP. We examined archaeological stratigraphies from 10 sites and collected charred seeds and charcoals for accelerator mass spectrometry (AMS) dating. The 26 radiocarbon dates show that the earliest inhabitation in the Nyingchi region can be traced back to as early as the fifth millennium BP. In addition, results of summed probability distribution (SPD) of radiocarbon dates suggest that intensive human activities occurred between c. 2700 and 2000 cal. yr BP. Together with the pottery net sinkers found in previous investigation, the newly identified archaeobotanical assemblages, including crops such as barley ( Hordeum vulgare), naked barley ( Hordeum vulgare var. nudum), wheat ( Triticum aestivum) and pea ( Pisum sativum), also confirm that cultivation and fishing were important subsistence strategies for people living in the prehistoric Nyingchi. The discoveries of domesticated crops from Southwest Asia also suggest that the southeastern TP, represented by the Nyingchi region, was part of the early communication network between the East and the West, predating historical Highland Silk Road.

Aragonite Fraction Dating of Vermetids in the Context of Paleo Sea-Level Curves Reconstruction

ABSTRACTIdentifying and tackling recrystallization is a critical factor in the reliable radiocarbon (14C) dating of carbonates, since exogenous carbon can be incorporated and thus mask the real age of the samples. Vermetids are among the most important bioindicators used for paleo sea-level reconstruction, and the accuracy of their chronology can significantly impact sea-level curves. Age differences larger than 1 14C kyr before and after acid etching, combined with X-ray diffraction (XRD) analysis that indicates a significant amount of calcite still remains in the shell, led us to apply the previously developed carbonate density separation protocol (CarDS). Using a solution of sodium polytungstate, with density of 2.80 g/cm3, we successfully separated different carbonate fractions for a set of 10 vermetid samples from the coast of Rio de Janeiro, southeast of Brazil. Each separation was verified by XRD analysis and the 14C concentrations of different fractions were compared. The results show that the calcite fraction in the studied vermetid samples varied from 12 to 63% and aragonite fraction ages are up to 2 14C kyr older than the raw samples, thus confirming the efficacy of CarDS in removing young carbonates and the importance of density separation to vermetids prior to accelerator mass spectrometry (AMS) dating.

New AMS Dates of Organic Microinclusions in Ice Wedges from the Lower Part of Batagay Yedoma, Yakutia

Accelerator mass spectrometry dating of organic microinclusions was performed on eight samples from the lower part of the thick Pleistocene syngenetic ice wedges exposed in the Batagay mega-slump in northern Yakutia, the upper reaches of the Yana River (67.58° N, 134.77° E). Radiocarbon dating suggests that ice wedge growth took place between 38 120 and 45 570 14C BP (42.1–49 cal ka BP). The Late Pleistocene mean January air temperatures from 42 to 49 cal ka BP have been reconstructed from the isotope data for the Batagay section and a number of reference sections in northwestern Yakutia. The lowest mean January air temperature of –51°С for this period was in Batagaika, whereas in the areas located 500–600 km to the north, it was 5–7°C higher. This is accounted for by the influence of the Yakutian anticyclone in winter during the Late Pleistocene from 42 to 49 cal ka BP, which was as pronounced at that time as it is now.

Detailed palaeomagnetic record at Rose Cottage Cave, South Africa: Implications for the Holocene geomagnetic field behaviour and chronostratigraphy

Palaeomagnetic data from a sedimentary section spanning the Holocene and terminal Pleistocene (~13 kya) from Rose Cottage Cave, eastern Free State (South Africa), are reported. The palaeomagnetic analysis took into account rock magnetism and directional analysis. The former reveals that most samples show stable single domain and superparamagnetic particles of Ti-poor magnetite and haematite. Natural remanent magnetisation directions were determined by progressive alternating field demagnetisation methodology. Directional analysis shows normal directions between samples 18 to 39 and 85 to 92; however, during the Early and Late Holocene in samples principally from RC40 to 84 ‘anomalous’ directions occurred. There is a significant westward shift in declination of ~80°, and a conspicuous fluctuating inclination in the lower part of the section during the Early Holocene at ≥9.5 kya and before ~12.0/13.0 kya. This palaeomagnetic record might become a chronostratigraphical marker for latest Pleistocene/Holocene sedimentary deposits in South Africa. Our two new accelerator mass spectrometry radiocarbon dates for the sampled deposit are 9500±50 BP and 1115±30 BP.
 Significance
 
 The study provides new accelerator mass spectrometry dates on the chronological sequence existing in Rose Cottage Cave.
 The findings contribute to the knowledge of the geomagnetic field behaviour since the terminal Pleistocene to the Late Holocene in a period spanning the last 13 000/12 000 years.
 This palaeomagnetic record might become a chronostratigraphical marker for the latest Pleistocene/ Holocene sedimentary deposits in South Africa.

Reconsidering the Chronology: Carbonized Food Residue, Accelerator Mass Spectrometry Dates, and Compositional Analysis of a Curated Collection from the Upper Great Lakes

Recent reexamination of pottery, copper objects, and glass trade beads using modern analytic methods has amended the occupational history of the Cloudman site (20CH6), once interpreted as an early “Contact” period site in Michigan. The original chronology of the site, located on northern Michigan's Drummond Island in Lake Huron, was based on an apparent association of Iroquoian pottery with European-made trade goods relatively dated to circa AD 1630. Current advances in archaeological dating methods have revealed new insights into the poorly understood settlement patterns and social interactions of various Upper Great Lakes groups between AD 1300 and 1700. Accelerator mass spectrometry dating of carbonized food residue collected from late Late Woodland and Ontario Iroquoian pottery vessels suggests some contemporaneous use of both styles and the culmination of occupation by pottery-making groups by AD 1500. Elemental analysis of glass beads indicates that the recovered trade items were likely manufactured post–AD 1650. Likewise, compositional analysis of copper-base metal artifacts clarifies how such objects were made and used over time at the site. The results demonstrate how the application of modern analytic methods to curated collections can lead to significant reinterpretation, ultimately enhancing understandings of regional chronologies, social relationships, and population movements.

Radiocarbon Dating of Medieval Buildings in the Mountainous Part of Ingushetia (Northern Caucasus, Russia)

ABSTRACTThere are hundreds of preserved medieval buildings in the mountainous part of Ingushetia, including Christian churches, crypts, temples, sanctuaries, battle towers, and living buildings. The chronology of their construction period is still questioned, as there are no radiocarbon (14C) dates published for these buildings and their dating is mainly based on architectural features, a few historical sources, and sometimes on accompanying archaeological material. The aim of this study is to assess more precisely the period of their construction. To do this, we selected the 10 most prominent medieval buildings that contain wooden construction elements and sampled these wooden elements in order to apply 14C accelerator mass-spectrometry dating (AMS) followed by wiggle-matching. From two of these buildings, plaster and mortar were also sampled for 14C AMS dating. This is the first time that these kinds of analyses have been performed for medieval buildings from the mountainous part of Ingushetia. For 6 out of 10 buildings, we acquired sufficiently precise dates that helped us to clarify their construction period. For the other 4 buildings, the acquired dates are still informative but could be refined further with additional 14C analyses. The calibrated dates obtained cover the period from AD 662 until recent time with the majority of them concentrated in 15th–17th centuries.

A High‐Resolution Geomagnetic Relative Paleointensity Record From the Arctic Ocean Deep‐Water Gateway Deposits During the Last 60 kyr

AbstractWe present a paleomagnetic and rock magnetic data set from two long sediment cores collected from Bellsund and Isfjorden contourite drifts located on the eastern side of the Fram Strait (western Spitsbergen margin). The data set gave the opportunity to define the behavior of the past geomagnetic field at high latitude and to constrain the palaeoclimatic events that occurred in a time framework spanning marine isotope stage 3 to the Holocene. A high‐resolution age model was reconstructed by coupling 26 radiocarbon ages and high‐resolution relative paleointensity and paleosecular variation of the geomagnetic field records for the last 60 kyr. We show the variation of the geomagnetic field at high latitudes, pointing out variability during periods of regular paleosecular variation (normal polarity) as well as during the most recent geomagnetic excursions, and we provide a high‐resolution record of the Laschamps excursion. Cross‐cores correlation allowed us to outline major, climate‐related, sedimentary changes in the analyzed stratigraphic sequence that includes the meltwater events MWP‐1a and MWP‐19ky, and the Heinrich‐like events H1, H2, H4, and H6. This contribution confirms that rock magnetic and paleomagnetic analysis can be successfully used as a correlation and dating tool for sedimentary successions at high latitudes, where accelerator mass spectrometry dates and oxygen isotope analyses are often difficult to obtain for the scarcity of calcareous microfossils and the uncertainties related to data calibration may be significant, as well as the complexity of water mass characteristics and dynamics through climate changes.

Modeling Kansas City Hopewell Developments and Regional Social Interactions

Abstract In the 1950s, the Kansas City Hopewell (KCH) was modeled as a phenomenon originating from a migration of people or diffusion of ideas from Middle Woodland Hopewell communities in Illinois, a model that greatly influenced subsequent research. Two lines of evidence were instrumental in the formation of this model: ceramics and chronology. This study presents the results of 24 newly obtained accelerator mass spectrometry (AMS) dates associated with a typological analysis of ceramics from three KCH sites, plus Early Woodland sherds from several regional sites. The results indicate that the KCH developed in part from local Early Woodland populations (ca. 500–1 BC) and was chronologically equivalent to Havana Hopewell in Illinois (ca. 100 BC–AD 400). Early and Middle Woodland ceramics also share affinities with types in regions to the north, south, and east of Kansas City, indicating that KCH origins and interactions were more multiregional and complex than the traditional model suggests.

Holocene Soil Evolution in South Siberia Based on Phytolith Records and Genetic Soil Analysis (Russia)

Dark, coniferous hemiboreal forests in the south of West Siberia are located in the Holocene forest-steppe ecotone, where natural environmental conditions have been quite dynamic. This dynamic environment resulted in the contrasting evolution of regional soil cover and the development of unique soil profiles with the second humus horizon. The second humus horizon is assumed to be a relic from the dark-humus soil formation stage in the mid-Holocene. This article draws conclusions about changes in regional environmental conditions by analysing data from a geochemically interrelated coevolutionary soil series, obtained by using a combination of conventional soil studies, phytolith analyses, and accelerator mass spectrometry (AMS) dating of phytolith-occluded carbon (PhytOC) and humic acids. The results showed that, in general, phytocenoses changed from mire-meadow vegetation towards forest vegetation via the meadow stage. However, these stages had different durations, depending on the soil catenary position. The topographical divergence of soil phytolith profiles reflects the relief effect on the development of specific soil type combinations, accounting for the major elements of the regional mid-Holocene soil cover. The leading elementary soil-forming processes were humus accumulation and hydrogenic accumulation of calcium carbonates. In the hilltop site of Endocalcic Stagnic Albic Luvisols, the evolutionary changes were shown by the shift from the meadow phytocenosis (Calcic Stagnic Chernozem) to the forest phytocenosis. In the midslope site, the environment was more humid from the start, favouring a phytocenosis with features of the meadow-mire type. The shift from the meadow-mire environment (with Spodic Chernic Gleysols) to the forest type environment with leading profile-forming processes, acid hydrolysis and lessivage, was gradual, occurring via the meadow stage with Calcic Stagnic Chernozem. In the toeslope site (Calcic Stagnic Greyzemic Epidystric Umbrisols), the meadow-mire stage (with Spodic Chernic Gleysols) was succeeded by the forest stage of soil formation. The AMS-dating of PhytOC estimated that the dark-humus stage of soil formation began 6.5–5.7 years calBC. Despite the observed slight translocation of phytoliths down soil profiles and phytolith solubilisation, phytolith analysis can be used to reconstruct shifts in the soil formation environment for surface Holocene palaeosols.

Wetland geomorphology and paleoecology near Akab Muclil, Rio Bravo floodplain of the Belize coastal plain

To understand wetland geomorphology and paleoecology, we collected a 2.6 m sediment core from a flooded swamp adjacent to the Maya archaeological site of Akab Muclil in the Maya Lowlands of northwestern Belize. The site of Akab Muclil has a known occupation that persisted from Early Maya Classic (1700–1350 BP) through the Terminal Maya Classic (1180–1050 BP) and into the Postclassic (1050–450 BP) and lies near a vast network of ancient Maya canal and field systems. We analyzed this core using a combination of paleoecological and geochemical techniques to determine the history of land use and natural change over time within this wetland. Accelerator Mass Spectrometry dating, pollen, charcoal analysis, micropaleontology, geochemical analysis, and magnetic susceptibility provide a suite of methods from which we interpret the geomorphic and ecological history of this wetland system. Four AMS dates from the length of the core provide us with an age model that runs from 1675 cal BP through the Maya Classic onward to the present. At the base of this system, soil composition and chemistry provide evidence that the system changed from a seasonally wet terrestrial soil to a perennially wet swamp, as the basal Mollisol soil lies buried by peats and calcareous sediments. This shift to a perennial wetland could be related to ancient Maya water management or a natural geomorphic change, though we suspect the former because of nearby ancient Maya large-scale geomorphic and hydrological manipulation in the form of intensive canalization and agriculture. Evidence of ancient Maya uses and impacts, including sedimentation, Zea mays pollen, and high charcoal counts occur from the lowest levels of the sequence through the Classic and into the Postclassic period. Above this level, the strata change to stable peats, laminated deposits of light gray/dark gray gypsum, authigenic carbonate, and layers of fibrist peat, with little evidence of human impact until recent increases in charcoal and phosphorous. This study, compared with other regional studies, indicates a later transition from terrestrial to wetland, later human impacts in the Postclassic, and a geomorphic impact record closely tied to the history of the adjacent site rather than broader land use trends.