Accelerator Mass Spectrometry Radiocarbon Research Articles

CHRONOLOGICAL STUDY OF COLLECTIVE BURIALS IN THE NORTHERN IBERIAN PLATEAU: ANALYSIS OF RADIOCARBON DATES ON HUMAN BONES FROM THE MEGALITHIC COMPLEX OF LA LORA (BURGOS, SPAIN)

ABSTRACTThis paper offers a temporal analysis of the megalithic group of La Lora in the context of northern Iberian Plateau megalithism. For this purpose, 67 accelerator mass spectrometry radiocarbon (AMS 14C) dates were obtained on human bone from the minimum number of individuals recovered from nine tombs. This is the first systematic dating project carried out in this dolmen group and has enabled the chronology of the main funerary series to be updated. The results reveal that the actual funerary use dates mainly to the 4th millennium BC, although, as deduced from the archaeological material, some tombs were reused in later periods. Additionally, the significant architectural polymorphism of the group, consisting mainly of simple dolmens and large corridor tombs, suggested a temporal evolution to monumentality. However, the dating shows a more complex reality, since it is likely that the large tombs functioned as funerary pantheons during the 4th millennium BC, characterized by a cyclical and recurrent use. In contrast, the simpler structures were preferred to be of shorter use and restricted to the first half of the 4th millennium.

AMS 14C DATING AND STABLE ISOTOPE ANALYSIS ON AN 8-KYR OYSTER SHELL FROM TAIPEI BASIN: SEA LEVEL AND SST CHANGES

ABSTRACT Seven accelerator mass spectrometry radiocarbon (AMS 14C) dates (7260±106∼7607±95 BP averaged 7444±103 BP) on a giant oyster shell, collected from an ancient shore of the Taipei Basin, are similar to the LSC (liquid scintillation counting) 14C age (7260±46 BP) of a grass sample inside the shell. The calibrated 14C ages of the C. gigas by Marine20 are 7490±240∼7805±230 cal BP (average 7660±96 cal BP), generally agreed with the calibrated LSC 14C ages of the grass and the oyster shell. Combined with other 14C ages of shoreline samples in the Taipei Basin, it is evident that sea level rose from 8600 to 7600 cal BP and reached a stand higher than modern sea level. During this marine transgression, the sedimentation rate along the shoreline was very high because 14C dating was not able to detect age differences for 4–5 m thick sediment sequences. Sixty-nine analyses of δ18O and δ13C from the oldest part of the shell exhibit clear seasonal cycles, with a 4-year period of growth in the 5.5-cm section. According to the δ18O values, the ancient oyster grew in a warmer-than-present shoreline environment, suggesting that the current absence of the giant oyster in Taiwan is not due to warming conditions.

STABLE ISOTOPE AND RADIOCARBON DATING OF HUMAN SKELETAL REMAINS FROM ISLAMIC SETTLEMENT, KHIRBET AL-SHEIKH HUMAID, NABLUS, PALESTINE

ABSTRACTKhirbet Al-Sheikh Humaid is found 615 m above sea level in the central highlands of Palestine, northwest of the city of Nablus. During rescue excavations carried out at the site, part of a male human skull with a tooth attached was discovered. Accelerator mass spectrometry radiocarbon (AMS 14C) dating and stable isotope analysis were performed on the tooth at the Hertelendi Laboratory in Debrecen, Hungary. Dating revealed the individual had lived in the time frame 900–1030 AD, which is within the Abbasid period (750–1258 AD). Dietary analysis gave information on the daily life of the inhabitants of the settlement, showing local agriculture provided a diet of legumes and vegetables.

A SUMMARY OF RADIOCARBON MEASUREMENTS OF FLUVIAL AND COLLUVIAL DEPOSITS IN CATCHMENTS OF SOUTH-CENTRAL ONTARIO, CANADA

ABSTRACTFluvial and colluvial deposits of Late Holocene age in South-Central Ontario catchments have provided few 14C dates, most by conventional methods registering century-old ages. Other young deposits, dated by conventional and accelerator mass spectrometry radiocarbon (AMS 14C), have yielded bomb-affected post-1950 ages over variable time limits. Attempts to date the base of Ah and lower-in-section soil horizons, in Early to Late Holocene stream terrace deposits, have yielded atomic bomb effects. Comparing bomb contamination in Late Holocene fluvial deposits, using both conventional and AMS methods, identifies a mix of bomb-affected beds juxtaposed with dated beds, the latter yielding ages with narrow standard deviations. Colluvial deposits overlying key glacial sections in the Rouge Catchment, while rare, yield bracketed AMS ages for an Ahbk horizon that refines weathering times relative to previously obtained conventional 14C dates. Bomb-affected sediment appears variably distributed within floodplain soils and in the ground soil of a colluvial section. Mass wasted deposits, with AMS 14C ages spread over the last few centuries, appear related to Little Ice Age (LIA) changes in climate, corroborated by pollen records. Further, these AMS-14C dated beds calibrate weathering of secondary Fe-Al oxihydroxides over the first half a millennium of weathering time.

Radiocarbon (14C) accelerator mass spectrometry as a convenient tool for differentiation of flavor chemicals of synthetic origin from biobased sources and their in-vivo toxicity assessment

Plants are known to be the natural factory for the production of flavor chemicals. Essential oils comprised of aldehyde as a functional group are potent in deciphering flavor effects in beverages and fresh and prepared food products. In the majority, these are manufactured through synthetic routes, resulting in high product carbon footprints or CO2 equivalents in total greenhouse gas emission. FDA has banned some of the synthetic flavor chemicals due to the health hazards associated with them. However, consumer's preference for natural is at stake due to the absence of quantitative traceability tools. The accelerator mass spectrometer (AMS) analysis revealed a distinction between natural and fossil-derived citral and its blends in Cymbopogon essential oils. The plant-derived citral contained a percent modern carbon (pMC) value in the range of 99–100 %. In contrast, the fossil fuel-derived citral showed zero pMC. Similarly, blends of Cymbopogon oils with 30–50 % (w/w) of fossil origin citral contained pMC equivalent to the proportions of modern carbon. These results showed the usefulness of AMS in quantifying the amount of 14C associated with flavor ingredients. Besides, acute oral toxicity data revealed Cymbopogon oils as the safe flavoring substance at the highest 2000 mg/kg body weight dose in Swiss albino mice.

BAYESIAN MODELING OF A PERIPHERAL MIDDLE BRONZE AGE SETTLEMENT AT ZAHRAT ADH-DHRA‘ 1, JORDAN

ABSTRACTAnalysis of 20 calibrated accelerator mass spectrometry radiocarbon (AMS 14C) ages reveals a chronology for the habitation of a unique peripheral settlement at Zahrat adh-Dhra‘ 1 (ZAD 1), Jordan during the Middle Bronze Age of the Southern Levant. Bayesian modeling distinguishes three phases of occupation between the first settlement at ZAD 1, perhaps as early as about 2050 cal BCE, and its abandonment by 1700 cal BCE. ZAD 1 represents a marginal community, both environmentally and culturally, on the hyperarid Dead Sea Plain, and exemplifies the peripheral settlements that are envisioned as important elements of Bronze Age Levantine society. Most importantly for this study, it is the only peripheral site in the Southern Levant that provides a Bayesian model for its habitation during the growth of Middle Bronze Age urbanized society. The timing of ZAD 1’s constituent phases, early in Middle Bronze I, across the Middle Bronze I/II transition and in Middle Bronze II, correspond well with emerging chronologies for the Middle Bronze Age, thereby contributing to an ongoing reassessment of regional social and settlement dynamics.

BONE POINTS IN TIME: DATING HUNTER-GATHERER BONE POINTS IN THE TERRITORY OF LITHUANIA

ABSTRACTBone points were one of the major hunting implements in northern European hunter-gatherer societies. They differ in shapes, types, and manufacturing techniques. In this paper, we investigate 22 bone points from the territory of Lithuania, by studying their morpho-technological characteristics, direct dates, and adhesive residues. The majority are isolated finds, but four points were selected from excavated archaeological sites dated between the 5th and 3rd millennia cal BC. Most of the points belong to the barbed points category, but six slotted points were also studied. Of the 22, 16 previously undated points were sampled for accelerator mass spectrometry radiocarbon (AMS 14C) dating. The results of 10 successfully dated samples are discussed together with previously published 14C dates of bone points from the same region. ATR-FTIR analysis of adhesive residues from six points suggest that birch bark tar was used to haft barbed points and lithic inserts. The results reveal the diversity of types of Early Holocene bone points in the territory of Lithuania, while the slotted and Kunda-type bone points fall into narrow timeframes.

Permafrost development in northern Fennoscandian peatlands since the mid-Holocene

ABSTRACT Increased permafrost temperatures have been reported in the circum-Arctic, and widespread degradation of permafrost peatlands has occurred in recent decades. The timing of permafrost aggradation in these ecosystems could have implications for the soil carbon lability upon thawing, and an increased understanding of the permafrost history is therefore needed to better project future carbon feedbacks. In this study, we have conducted high-resolution plant macrofossil and geochemical analyses and accelerator mass spectrometry radiocarbon dating of active layer cores from four permafrost peatlands in northern Sweden and Norway. In the mid-Holocene, all four sites were wet fens, and at least three of them remained permafrost-free until a shift in vegetation toward bog species was recorded around 800 to 400 cal. BP, suggesting permafrost aggradation during the Little Ice Age. At one site, Karlebotn, the plant macrofossil record also indicated a period of dry bog conditions between 3300 and 2900 cal. BP, followed by a rapid shift toward species growing in waterlogged fens or open pools, suggesting that permafrost possibly was present around 3000 cal. BP but thawed and was replaced by thermokarst.

First occurrence of planktonic foraminiferal species Boliella adamsii as a marker for the Pleistocene-Holocene Boundary in the sea around Sumba Island

The expensive cost of Accelerator Mass Spectrometry radiocarbon dating (AMS 14C), the main tool for geochronology in Late Pleistocene-Holocene paleoclimate and paleoceanography study using marine sediment cores, hinders Indonesian researchers to produce competing research outputs. The first occurrences of planktonic foraminiferal species which have been applied as Pleistocene-Holocene Boundary markers in previous Quarternary marine sediment studies in the Indonesian region need to be confirmed as these species might actually occur since the Late Pleistocene. Quantitative foraminifera determination and oxygen isotope (δ18O) analysis of planktonic foraminiferal species Globigerinoides (Gs.) ruber have been carried out in marine sediment cores ST10 (off south Sumba) and ST14 (Sumba strait). δ18O of Gs. ruber was correlated to North Greenland Ice Core Project (NGRIP) Greenland Ice Core Chronology 2005 (GICC05) δ18O to determine the depth of the Pleistocene-Holocene Boundary (11653 BP) in core ST10 and ST14. Pleistocene-Holocene Boundary depth in core ST10 (31 cm) and ST14 (28 cm) are nearly coeval with the First occurrence (FO) of planktonic foraminifera Boliella adamsii, which at 34-35 cm depth interval in core ST10 and at 26-27 cm depth interval in core ST14. This indicated the practicality of Boliella adamsii FO as a Pleistocene-Holocene Boundary marker in the sea around Sumba Island, in case radiocarbon ages and proper planktonic foraminiferal δ18O data are not available. Future studies using a similar method in other Indonesian regions are needed to confirm the practicality of Boliella adamsii FO as a Pleistocene-Holocene Boundary marker in the Indonesian region.

LASER ABLATION SYSTEM WITH A DIODE LASER FOR AMS 14C MEASUREMENT OF ORGANIC MATERIALS

ABSTRACT We constructed a laser ablation (LA) system using a diode laser for the accelerator mass spectrometry radiocarbon (AMS 14C) measurement of organic materials. The system could extract adequate CO2 to analyze small masses (0.1 mg C) at a resolution of 250 µm by a 5.5 W diode laser. The LA system was assessed using standard materials (IAEA-C1, IAEA-C2, IAEA-C3, IAEA-C6, and Ox II) and applied to natural tree ring samples. For the LA sampling of organic samples, which generally results in incomplete combustion, tungsten (VI) oxide was used as an oxidant to achieve complete burning. The results of the measurement of standard materials showed a low 14C background of F14C 0.0085 ± 0.0005 and reasonable reproduction of 14C values. Finally, we applied this system to a single-year analysis of tree-ringed spruce timber in Alaska. It was observed to have a detectable background for the 14C bomb peak.

NEW RADIOCARBON DATES FROM POLISH INLAND DUNES POINT TO PREVALENCE OF HUMAN IMPACT ON DUNE MOBILITY

ABSTRACTThe timeframes of Holocene anthropogenic dune remobilization in Central Europe remain less studied compared to those of Late Glacial climatically controlled dune formation. The present contribution aims to reinforce existing knowledge on the chronology of Late Glacial–Holocene dune activity and stability, as well as to reveal the scale of human impact on dune remobilization. Accelerator mass spectrometry radiocarbon (AMS 14C) dating and calibration of the results are reported from paleosol horizons buried in inland dune deposits that occur in Central and Eastern Poland. Twenty-three new dates are based on charcoal samples collected at 13 sites. From each of the investigated sites, at least one AD date is obtained, indicating that buried paleosols of such young age are far more widespread in Polish dunes than reflected in previous studies. The widespread preservation of these paleosols under cover of aeolian sand reflects the extent of the anthropogenic dune formation phase that peaked during the Medieval and Early Modern periods.

THE FIRST COMBINED RADIOCARBON AND ARCHAEOLOGICAL DATING OF THE GREAT MIGRATION PERIOD MATERIALS IN NORTHERN ALTAI: THE NECROPOLIS OF KARBAN-I

ABSTRACT The lack of systematic chronologies is a key problem for the archaeological sites of Altai and adjacent territories during the Great Migration Period. Here we present an attempt to establish the chronology of the Bulan-Koby culture objects of the Karban-I necropolis by correlation of accelerator mass spectrometry radiocarbon (AMS 14C) data from human remains with data from archaeological dating methods. This is the first application of such a combined targeted 14C and archaeological approach to the chronology of the Great Migration Period materials of northern Altai, and in particular the Bulan-Koby culture. Systematic analysis of the mutual occurrence of dated types of certain grave goods and 14C dating of a series of samples supports a predominant period of use for the site that spans the 2nd–3rd c. AD, which corresponds to the early Xianbei period. This study demonstrates strong agreement between the indicators obtained by archaeological and radiocarbon methods, suggesting chronological consistency of the necropolis which functioned at the beginning of the Great Migration Period. The very combination of the two techniques will allow more precise and detailed chronologies for other archaeological complexes of Altai and adjacent territories from the first centuries of the 1st mil. AD, which is the basis of historical reconstructions.

Magnetic and grain-size properties of the Weihe River sediments reveal runoff changes in the Holocene

Abstract Detailed and systematic analyses of the magnetic and grain-size properties of the Weihe River sediments were conducted to explore effective proxies that could reflect variations in the runoff. Ultimately, the magnetic parameter χARM/χlf was considered a reliable proxy owing to the close relationship with grain-size fraction larger than 63 μm, with a correlation coefficient of 0.90. By combining accelerator mass spectrometry radiocarbon (AMS 14C) dating, a timescale ranging from 12,900 year BP to the present was established for the section. Accordingly, the reconstructed runoff variations showed that, from 12,900 to 9,600 year BP, the hydrodynamic force of the river was relatively strong, and the runoff was large. From 9,600 to 7,500 year BP, these two parameters varied from weak to strong, and the trend continued to increase from 7,500 to 5,300 year BP. At 5,300 year BP, the sediments shifted from the fluvial to the continental environment, indicating a marked decrease in the runoff. Although the resolution and pattern of this reconstruction were rough, this is a significant analysis among the historical runoff studies based on floodplain sediments, and the results showed trends that to some extent coincide with the variations in the intensity of the East Asian Summer Monsoon.

RADIOCARBON ANALYSIS AND STATUS REPORT FROM TÜRKIYE: 1MV NATIONAL AMS LABORATORY (TUBITAK-AMS)

ABSTRACTIn autumn of 2016, the National 1MV Accelerator Mass Spectrometry (AMS) Laboratory at The Scientific and Technological Research Council of Türkiye (TÜBİTAK), Marmara Research Center (MRC), Türkiye (Turkey), started to offer radiocarbon (14C) analysis service internationally. In this article, the process from sample acceptance to reporting and the primary procedures implemented and applied for 14C analysis at the TÜBİTAK AMS Radiocarbon Dating Laboratory are described. The service provided by the laboratory includes sample evaluation for 14C analysis, sample preparation, graphite production, AMS measurement, data supervision, calendar date calculations, and consultancy. For commercial testing and analysis, a one-page official report which shows the 14C age and uncertainty is provided for each sample. In addition to a dedicated wet chemistry laboratory to process samples before measurement with AMS, there are two systems for the conversion of CO2 to elemental carbon process; an automated graphitization system (AGE III) and a manual graphitization system based on a glass high vacuum line. A 1MV UAMS NEC Pelletron system installed in the laboratory is used for natural level 14C samples needed to be analyzed for archeological, geological, geographical, and environmental and forensic science applications. In addition to commercial 14C testing and analysis activities, national and international research projects can be developed or contributed to within the scope of project management or partnership.

A 55,000-Year Reconstruction of Vegetation in the Los Angeles Basin: Insights into Future Change and a Better Guide for the Present

The California Floristic Province is a biodiversity hotspot. Endemic flora is threatened by climate change, habitat fragmentation and destruction. It is also host to the La Brea Tar Pits (LBTP), which in addition to its famous megafauna, preserves a rare long-term plant macrofossil record with taxonomic resolution to genus and species. The LBTP flora has the potential to provide a comprehensive vegetational history for the Los Angeles Basin and a dynamic baseline for modern conservation efforts. We used accelerator mass spectrometry (AMS) radiocarbon dating to establish a 55 ka timeline of plant presence in Los Angeles, California. We identified and radiocarbon dated 188 plant macrofossils from the La Brea Tar Pits collections. Eight distinct phases of vegetation were identified based on the loss or appearance of key taxa in the timeline. Pairwise similarity was calculated between each identified phase to compare changes to phase species makeup through time. The transition periods between phases were compared to existing climate proxy records to better understand forcings behind vegetation shifts. Two transition periods in the record are of interest to modern conservation efforts. First, fog-dependent closed cone pine species, Pinus muricata and Pinus radiata, become extirpated from the Los Angeles Basin at 48 ka. This disappearance corresponds with a period of extended drought. Second, repeated patterns of juniper species replacement during periods of megadrought, and their eventual extirpation at 12.8 ka, indicate the importance of land management choices in the ability of juniper populations to rebound after drought-induced die-off. Understanding the long-term dynamics of plant community structure in a region is crucial to managing landscapes in the context of global change, and these data are now being leveraged to inform local conservation efforts in the city of Los Angeles.

New radiocarbon dates and the prehistoric human occupation at the Lake Qinghai Basin, northeast Tibetan Plateau

The Tibetan Plateau is known as the rooftop of the planet. Its hypoxic atmosphere in low oxygen partial pressure, extreme seasonal climate variation, and aridity poses severe challenges as harsh living environments for prehistoric human to occupy in such high-altitude niches. However, the Lake Qinghai is the largest lake on the Tibetan Plateau and the basin has rich water, mineral, and wild food resources, and prehistoric human occupied the Lake Qinghai Basin long before local farming was in practice. In this paper we present results of faunal assemblages associated with variable stone artifacts and pottery shards with bone collagen accelerator mass spectrometry radiocarbon (AMS 14C) dates from 3 new archaeological sites to investigate human occupation history in the southern Lake Qinghai Basin. The AMS 14C dating results reveal that the occupation occurs intermittently from the late Glacial to entire Holocene. Through compilation and synthesis of regional archaeological records, we found that prehistoric humans went through 3 phases of subsistence strategies: 1) hunting large and medium ungulates; 2) hunting medium ungulates; 3) foraging small size mammals with birds and fish diets. At the end, prehistoric humans increasingly adapted to forage and consume caprinaes species (goat), which represents a precursor of domestication or semi-domestication of wild animals in the Lake Qinghai Basin. We further attribute the utilization of caprinaes animal resources to the lower limbs of toe and phalange bones with low nutritious values to advanced social organization that implied prehistoric humans separated hunting activity from protein processing practices. Our investigation of zooarchaeology with reliable bone collagen AMS 14C dates could become a novel approach to study adaptation strategy and social structure changes of prehistorical Tibetan humans.

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.

AMS 14C ages determination of the late Holocene Pilas, Mula and Cabeza de Vaca monogenetic volcanoes, Nicaragua

Here we present six new 14C ages using the accelerator mass spectrometry (AMS) technique for five samples of paleosol and one charcoal collected from the central part of the Maribios volcanic mountain range, located in the northwestern part of Nicaragua. This region is part of the Nicaraguan active volcanic arc characterized by the occurrence of a historic eruption that gave rise to the “birth” of the Cerro Negro volcano in 1850 CE. The young relief and the new 14C ages obtained in this work reveal that three other Holocene eruptions had recently occurred before the growth of the Cerro Negro volcano in this region. These volcanic events were independently established from an emission vent with simultaneous Strombolian explosions to dominantly effusive eruptions, forming extensive lava flows and associated scoria cones of the Cabeza de Vaca, Mula, and Pilas monogenetic volcanoes. AMS radiocarbon dating from charcoal and paleosols underlying these deposits yielded maximum ages of 1050 ± 30 years BP for Cabeza de Vaca volcano, 860 ± 30 yrs BP for Mula volcano, and 520 ± 15 yrs BP for Pilas volcano. These results of AMS 14C analyses provide reliable age ranges of 990–1025 cal yr AD for Cabeza de Vaca volcano, 1166–1220 cal yrs AD for Mula volcano, and 1410–1424 cal yrs AD for Pilas volcano.

Technical Carbon Black and Green Technology

Abstract Carbon black (CB) is produced through the incomplete combustion of biomass or thermal decomposition in an oxygen-deprived environment. Technical carbon black (TCB) primarily consists of elemental carbon and comes in various grades distinguished by surface area and nanostructure morphologies. However, TCB production raises sustainability concerns due to its reliance on non-renewable feedstock, significant CO2 emissions and high energy consumption. TCBs find extensive use as reinforcing fillers in the tire and rubber industries. Recent studies underscore the importance of eco-friendly alternatives. This research was carried out to monitor the renewability of the TCB samples by determining the 14C isotope concentration. Liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) radiocarbon techniques were employed for measuring the 14C isotope concentration, while isotope ratio mass spectrometry (IRMS) corrected standardised isotope fractionation correction. The investigation revealed that the examined TCB samples contain extremely low 14C concentrations, measuring <1 per cent modern carbon (pMC). This finding raises concerns regarding potential environmental ramifications.

Late Glacial development of lakes and wetland vegetation in a dune area in Central Poland

This study investigated the history of the development of six, paleo-lakes, which are at present filled with sediments, in a dune area in Central Poland, based on multiproxy paleoecological analyses and accelerator mass spectrometry radiocarbon dating. The aims of the paleoecological studies were: i) to determine the initial age of lakes development, ii) to reconstruct the local and regional plant succession, as well as iii) to reconstruct the environmental conditions during the initial stage of the development of lakes and peatlands. The obtained results indicated that: the former lakes in dune depressions were developed during the Bølling and Allerød when sparse vegetation allowed strong aeolian activity. Climate warming in Bølling led to the development of a denser plant cover, inhibition of sand transportation and the formation of mid-dune reservoirs with the accumulation of organic sediments. As indicated by 14C dating, mid-dunes basins were formed between 14 686 ± 60 cal. yr BP and 13 421 ± 60 cal. yr BP. The results of the paleobotanical analysis suggested that the reservoirs were shallow, oligo-mesotrophic, inhabited by pioneer calcicole vascular plant species such as: Chara sp., Hippuris vulgaris, Potamogeton natans, Potamogeton fresii, Potamogeton alpinus and Potamogeton filiformis, and mosses such as: Pseudocalliergon trifarium, Calliergon sp. and Calliergonella cordifolium. The area next to the reservoirs was covered with sparse pine forests combined with birch, which is typical of the Late Glacial period. The open areas were dominated by psammophilic and steppe vegetation, including Poaceae, Artemisia and Hippophae rhamnoides. Geochemical analysis revealed that Ca2+ and Fe3+ were in high concentrations, which could have influenced the presence of taxa preferring soil with high Ca2+ content. The accumulation of calcium in sediments confirms that the reservoirs were fed by groundwater originating from the progressive degradation of permafrost associated with thermal changes.