Pleistocene-Holocene Boundary Research Articles

Diet breadth and biodiversity in the pre-hispanic South-Central Andes (Western South America) during the Holocene: An exploratory analysis and review

This paper presents an exploratory study on the taxonomic diversity of pre-Hispanic archaeofaunas in the South-Central Andes (SCA; western South America) from the Pleistocene-Holocene boundary to the Late-Holocene. The SCA is a complex of diverse environments and has undergone distinct climate events for the last 13,000 years, such as the occurrence of warmer and drier conditions in the Middle-Holocene. The South-Central Andean area was part of the larger Andes interaction area, which was a primary center for animal and plant domestication and the emergence of agro-pastoralist economies. Since subsistence was key to these processes, the SCA provides a relevant case study on the interactions among environment, foodways and sociocultural evolution. Taxonomic diversity was used here as a proxy for diet breadth. A total of 268 archaeofaunal assemblages were sampled from the zooarchaeological literature. Reviewed variables included the cultural chronology and spatial coordinates of the assemblages, as well as the presence and abundance of taxa at the family rank. Taxonomic diversity covered two dimensions: composition (families present in each assemblage) and structure (quantitative relationships among taxa), which was measured through richness (NTAXA), ubiquity and relative abundance (NISP based rank-order). Despite the uneven distribution of samples, the analyses revealed the following trends: (1) a moderate relationship between NTAXA and distance from coastline for most of the Holocene; (2) a potential decrease in assemblage richness for coastal ecoregions during the Late-Holocene; and (3) a generalized increase in the relative abundance of Camelidae.

ON THE COLONISATION OF THE CENTRAL RUSSIAN PLAIN IN LATE GLACIAL AND EARLY HOLOCENE ACCORDING TO GEOARCHAEOLOGICAL DATA

Until recently, interpreting archaeological data on the colonisation of the Central Russian Plain during the last glacial epoch (Late Valdai, Vistulian) had been hampered by the prevailing view that vast areas along the ice sheet boundary were submerged by large proglacial lakes. Under the hypothesis that the Tver proglacial lake was covering Upper Volga lowlands and the Dubna depression, these territories would not be habitable until the Pleistocene-Holocene boundary when they finally dried up in the process of deglaciation. In 2018-2021, geoarchaeological investigations were carried out in Zabolotsky peatland (Moscow Region) to test this hypothesis. It was found that during the whole Late Valdai (Vistulian) glacial epoch, the prevailing environmental conditions in the Dubna Lowland were fluvial, rather than lacustrine. Thus, it is entirely plausible that large parts of the Zabolotsky area could already start to become populated at that time. AMS-dating of resin samples from the grooves of bone and hornbeam artefacts attributed to Epigravettian Resseta culture pinpoint the potential timing of this event to circa 15,500 cal BP. During Early Holocene, Zadnepilevo industry was the successor to Resseta tradition. Other populations known to exist in Central Russian Plain during late Pleistocene – early Holocene are attested from Bromme, Ahrensburg, Kultino and Purgasovo culture complexes. The identification of Elin-Bor, Butovo and Ienevo cultures in the Volga-Oka basin during the Mesolithic had been made by tampering with primary data. Therefore, any further allusion to these cultures would be unethical Seasonal migration patterns of both Resseta and Zadnepilevo populations are evidenced not only by data from the Russian Plain, but also from the Scandinavian Peninsula. Here, they are represented by the so-called "eastern pulse" industry. To piece together the cultural and historical development of Eastern and Northern Europe, a substantial increase in field research is needed.

Reconstructing the Paleoenvironmental Evolution of Lake Kolon (Hungary) through Palaeoecological, Statistical and Historical Analyses

The research utilizes an interdisciplinary approach, combining geological, ecological, and historical methods. It delves into the environmental evolution of Lake Kolon over a span of 17,700 years, shedding light on the intricate interplay between geological processes and ecological changes. The historical, statistical (PCA, DCA), and palaeoecological analyses centers on a core sequence situated in the heart of the lake, building upon previous research endeavors (pollen, malacological, macrobotanical and sedimentological analyses with radiocarbon dating). Forest fires occurred at the end of the Last Glacial Maximum (LGM); the boreal forest–steppe environment changed into temperate deciduous forest at the Pleistocene–Holocene boundary; human-induced environmental change into open parkland occurred; and from medieval times, communities used the land as pasture. This type of reconstruction is crucial for understanding how ecosystems respond to climate change over time, which has broader implications for modern-day conservation efforts and managing ecosystems in the face of ongoing climate change.

A new extinct species of Scybalophagus dung beetle supports the collateral extinction hypothesis at the Chilean South American Pleistocene–Holocene boundary

ABSTRACTThe extinction of megaherbivores (weighing over 1000 kg) at the Pleistocene–Holocene boundary caused drastic changes at multiple trophic levels. However, few examples of Pleistocene insect extinction have been reported in the literature. Here we describe a new extinct dung beetle species, Scybalophagus brellenthinae sp. nov., based on fossil remains recorded from an Upper Pleistocene sequence from Chilean Northern Patagonia (Osorno city: 40°34′S, 73°07′W) dated between ~16 400 and ~12 800 cal a bp. S. brellenthinae is shown to be a species of the genus Scybalophagus based on the following morphological characters: a bidentate clypeus, teeth separated by U‐shaped emargination; protibiae with three major denticles on the external margin, separated by minor denticles, present at the base of the protibiae; and mesotibiae with prominent transverse carinae. Additionally, this new species can be clearly distinguished from extant species of the genus by its shiny green color. Extant Scybalophagus are true dung beetle species that depend on fresh mammal dung for their nest development. Therefore, we suggest that the mass extinction of the megaherbivores during a period of drastic environmental change at the Pleistocene–Holocene boundary in southern South America induced the collateral extinction of S. brellenthinae. Thus, this study provides new insights into dung beetle diversity of the past.

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.

Reconstructing the Paleoenvironmental Evolution of Lake Kolon (Hungary) through Integrated Geochemical and Sedimentological Analyses of Quaternary Sediments

Lake Kolon (Hungary), situated in the middle of the Turjánvidék area between the saline lakes of the Danube valley and the Homokhátság, is one of the most significant natural aquatic habitats in the Danube–Tisza Interfluve region. The central question of this study is how the lake changed, and how environmental factors and human activities have influenced these paleoenvironmental changes in Lake Kolon. A multiproxy analysis of a core sequence (loss on ignition, grain size, magnetic susceptibility, and geochemistry) provided crucial insights. Notably, correlations are observed in the following relationships: (1) clay, organic matter, and elements derived from organic sources, such as Na, K, and Zn; (2) MS, sand, inorganic matter, and elements originating from inorganic sources, such as Fe, Al, Ti, Na, K, and P; and (3) carbonate content and elements originating from carbonate sources, such as Ca and Mg. The lake’s paleoenvironment underwent significant changes in the past 27,000 years. Late-Pleistocene wind-blown sand provided the bottom for an oligotrophic lake (17,700 BP), followed by a calcareous mesotrophic Chara-lake phase (13,800 BP). Peat accumulation, along with the eutrophic lake phase, began at the Pleistocene–Holocene boundary around 11,700 BP. From 10,300 BP, with the emergence of an extended peatland phase, the percentage of organic matter (peat) increased significantly. Anthropogenic changes occurred from around 9000–8000 BP due to the different emerging cultures in the Carpathian basin, and from 942–579 BP due to the Hungarian settlements and activity nearby, respectively.

Magnetic–Mineralogical Anomalies at the Pleistocene–Holocene Boundary in Lacustrine Sediments of Northeastern Russia

Magnetic–Mineralogical Anomalies at the Pleistocene–Holocene Boundary in Lacustrine Sediments of Northeastern Russia

The Stone Age Sannikov Land: human dimensions

The New Siberian Islands are one of the most remote and hardly accessible regions of the Russian Arctic. Due to that, their discovery and initial study took about 300 years. For dozens of thousand years during the Late Pleistocene, this area was a part of drained arctic shelf, a part of which still existed around 9000 years ago. In certain sense, it was the Sannikov Land of the Stone Age. In 1914, the Zhokhov Island became the last one to be discovered out of large islands of the archipelago. Fifty years afterwards, archaeological material was found on it. The Zhokhov site, studied in 1989–1990 and 2000–2005, is one of the northernmost archaeological sites in the world. Human activity at the Zhokhov site falls within the interval 8300–7750 14C years ago, with the most intense occupation spanning 8050–7900 14C BP, that is, roughly CA 9000 calendar years ago. Excavations yielded a unique collection that includes lithic material presenting microprismatic technology, polished stone tools, a variety of artefacts made of non-durable materials (diverse osseous material and wood), including hunting equipment, home utensils, basketry and birch bark products, as well as sled parts. Excavations yielded a large number of animal bone remains, almost exclusively belonging to the reindeer and polar bear. It is shown that in the reconstructed annual economic cycle of the Zhokhov dwellers in winter, the most important role was played by polar bear hunting. Mass procurement of this dangerous animal for food is a unique hunting specialization, while mass accumulation of his bone remains can not be taken as an evidence for the bear cult. It is shown, that the Zhokhov hunters widely used dog sleds and thus the land transportation system was the most important innovation of the Pleistocene-Holocene boundary. The Zhokhov site environments of 9000 years ago were quite comfortable for the Arctic regions. Open landscapes were the most important feature of their habitat providing unlimited opportunities for traveling across the region, especially in winter and spring and thus provided conditions for effective movement of people goods, and genes including long-distance transport.

Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)

Abstract. This study is based on multiproxy data gained from a 14C-dated 6.5 m long sediment core and a 210Pb-dated 23 cm short core retrieved from Lake Rauchuagytgyn in Chukotka, Arctic Russia. Our main objectives are to reconstruct the environmental history and ecological development of the lake during the last 29 kyr and to investigate the main drivers behind bioproduction shifts. The methods comprise age-modeling, accumulation rate estimation, and light microscope diatom species analysis of 74 samples, as well as organic carbon, nitrogen, and mercury analysis. Diatoms have appeared in the lake since 21.8 ka cal BP and are dominated by planktonic Lindavia ocellata and L. cyclopuncta. Around the Pleistocene–Holocene boundary, other taxa including planktonic Aulacoseira, benthic fragilarioid (Staurosira), and achnanthoid species increase in their abundance. There is strong correlation between variations of diatom valve accumulation rates (DARs; mean 176.1×109 valves m2 a1), organic carbon accumulation rates (OCARs; mean 4.6 g m−2 a−1), and mercury accumulation rates (HgARs; mean 63.4 µg m−2 a−1). We discuss the environmental forcings behind shifts in diatom species and find moderate responses of key taxa to the cold glacial period, postglacial warming, the Younger Dryas, and the Holocene Thermal Maximum. The short-core data likely suggest recent change of the diatom community at the beginning of the 20th century related to human-induced warming but only little evidence of atmospheric deposition of contaminants. Significant correlation between DAR and OCAR in the Holocene interglacial indicates within-lake bioproduction represents bulk organic carbon deposited in the lake sediment. During both glacial and interglacial episodes HgAR is mainly bound to organic matter in the lake associated with biochemical substrate conditions. There were only ambiguous signs of increased HgAR during the industrialization period. We conclude that if increased short-term emissions are neglected, pristine Arctic lake systems can potentially serve as long-term CO2 and Hg sinks during warm climate episodes driven by insolation-enhanced within-lake primary productivity. Maintaining intact natural lake ecosystems should therefore be of interest to future environmental policy.

Sedimentary facies characterization through CPTU profiles: An effective tool for subsurface investigation of modern alluvial and coastal plains

ABSTRACTCone penetration tests, a method that is typically used to determine the engineering properties of soils, can be used as an effective tool for refined subsurface stratigraphic investigations of alluvial and coastal plains, aside from the geographic location. High‐resolution calibration of piezocone penetration tests (CPTU) with 20 sediment cores enabled the detailed characterization of alluvial, deltaic and coastal depositional systems of the Po Plain. Twelve cored facies associations, typical of alluvial and coastal plain environments, were characterized based on four distinct CPTU profiles: basic cone resistance (Qc), sleeve friction (Fs), water pore pressure (U) and friction ratio (FR). Sandy facies associations (fluvial/distributary channel, bay‐head delta, transgressive barrier, delta‐front/beach‐ridge) typically have high (>4 MPa) Qc, low‐to‐negative U and low (<2%) FR. Muddy deposits (well‐drained/poorly‐drained floodplain, swamp, lagoon and prodelta) exhibit opposite trends. Heterolithic facies associations (crevasse‐levée, offshore/delta‐front transition) display characteristic seesaw profiles. Plotting of late Quaternary deposits onto the latest version of the cone penetration test typical soil behaviour chart (Robertson, 2010) enables the identification of distinctive facies associations reflecting distinctive grain size. CPTU interpretation leads to sedimentary facies recognition well beyond the simple lithological differentiation and, in particular, allows the refined characterization of clay‐rich and silt‐rich depositional units (swamp clays and peats, central‐inner and outer lagoon, proximal/distal prodelta deposits) that exhibit only subtle differences in lithology. CPTU data can also serve for the accurate detection of key stratigraphic surfaces with potential engineering applications, such as the Pleistocene–Holocene boundary. This latter, a common feature of several alluvial and coastal plain successions, is commonly marked by an abrupt upward decrease of basic cone resistance and sleeve friction from Late Pleistocene, pedogenized, stiff strata to overlying Holocene, organic‐rich, soft deposits. This study offers an updated CPTU‐facies characterization method that could be suitable for subsurface investigations of modern alluvial and coastal plains worldwide.

Late quaternary hydrological changes in the southeastern amazon basin from n-alkane molecular and isotopic records in sediments of Saci lake, Pará state (Brazil)

The molecular distributions and isotopic ratios (δ13C and δD) of n-alkanes in sediments deposited during the last 35 cal kyr BP in Saci Lake, southeastern Amazonia, have been measured and interpreted for their paleoclimate information. A terrestrial origin for the odd carbon-numbered long-chain (>C27) n-alkanes has been inferred from molecular distributions. A shift in the n-alkane δ13C values across the Pleistocene-Holocene boundary coincides with a climate-induced floral change previously deduced from palynological analyses. Dry conditions during the late Pleistocene and mid-Holocene were confirmed by several n-alkane indices used to estimate the availability of moisture and by larger δD values. High ACL values indicate relatively dry conditions from 29 to 18.2 cal kyr BP and again from 8.0 and 5.0 cal kyr BP with a decrease in precipitation and an increase of grasses. Changes in the n-alkane C-29 isotopic compositions (δD and δ13C) were observed during the Pleistocene-Holocene transition, coinciding with a floristic change induced by climatic conditions that is also observed in palynological results from the same lake. The n-alkane C-29 δ13C values remain between −33.2‰ and − 35.7‰, which is representative for n-alkanes derived from C3 vegetation. These lines of evidence suggest a continuous gallery forest cover in the Saci Lake catchment for the last ~35 cal kyr BP in contrasted with the observed palynological changes which represent the dynamics of the vegetation on the upland areas. The n-alkane C-29 δD values are less negative in the Pleistocene and more negative during the Holocene in the lake record. These characteristics suggest more humid conditions during the Holocene than in the Pleistocene, probably associated with the South American Monsoon System (SAMS). However, an increase of approximately 10‰ occurs during the late Holocene, which coincides with the forest expansion around 5 cal kyr BP that is recorded in palynological data of Saci Lake and other records of the Amazon Forest. This change suggests that the D/H ratio is also influenced by the increase of the plant biomass, which would provide an enrichment of D in the isotopic signal as a function of regional moisture recycling caused by evapotranspiration.

Late Pleistocene aeolian deposition and human occupation on the eastern edge of the deglacial corridor, northeastern Alberta, Canada

AbstractThe lower Athabasca River basin in northeastern Alberta contains one of the highest known concentrations of prehistoric archaeological sites in the boreal forests of western Canada. This is due to the combination of readily available sources of lithic raw material stone near a major travel corridor, and extensive archaeological survey conducted in advance of oil sands mining. Typological studies have proposed immediate post-glacial occupations that were contemporaneous with, or immediately followed, the catastrophic glacial Lake Agassiz flood through the area at the end of the Pleistocene. Here, we complement the typology age estimates by using stratigraphic relations and infrared stimulated luminescence (IRSL) dating of aeolian material to determine the age of initial human occupation, and reconstruct the environment encountered by early inhabitants of the region. We find that the first occupations in our study area took place near the Pleistocene-Holocene boundary (ca. 11.3 ± 0.8 ka BP), shortly after catastrophic flooding from Lake Agassiz. The post-flood environment was dominated by cold climatic conditions that supported permafrost, presumably during the late Pleistocene, and underwent significant aeolian deposition. Our results indicate that this area represents a portion of the eastern edge of the deglacial corridor into which plants, animals, and humans dispersed following retreat of the Laurentide Ice Sheet.

Environmental changes since 14 ka BP in the southernmost Kuril islands (North-Western Pacific) and regional correlation of events

• New data on climatic changes at the late Pleistocene-Holocene boundary for Kurils. • Climate fluctuations and volcanic ash-falls were mail drivers in lake-mire evolution. • The lake level was highest during warmer and humid climate of the Allerød. • Younger Dryas cooling in the Kuril Islands was less distinct than on the continent. • Pollen record vegetation changes on the land bridge at Late Glacial–early Holocene. Despite considerable progress in understanding Late Pleistocene and Holocene palaeoenvironmental changes worldwide, there are still very few such data for the Far East, and Kuril islands, in particular. Here, the sea level rise during the Late Glacial–Holocene transition was accompanied by a loss of the land connectivity culminating into the development of isolated islands. The ecosystems evolution and importance of isolation for vegetation dynamics on islands are still insufficiently understood. We investigated a unique natural record of environmental change since 14 ka has been recently discovered in lake–mire complex on Kunashir Island. The sediments include 12 tephra layers from Kunashir and Hokkaido volcanoes. The lake level was highest during warmer and humid climate of the Allerød. Diatom assemblages indicated the higher lake level between 12 730–12 160 cal yr BP. The first half of Younger Dryas was characterized by heavy snowfalls. Cooling attributed to the Younger Dryas in the Southern Kurils was less distinct than on the continent. The pollen assemblages recorded changes in vegetation on the land bridge. At the end of the Pleistocene large areas were occupied by birch forests and shrub pine. The broadleaf species first appeared at the end of Allerød. Starting from the Pleistocene-Holocene transition and during the early Holocene , the role of conifers sharply increased. In the middle Holocene the proportion of broadleaf trees in forests increased. Coniferous forests became abundant during the Little Ice Age. Short-tern climatic fluctuations correlate well with regional pattern, particularly with fluctuations of the moisture supply.

DIATOM RESPONSE TO ENVIRONMENTAL CHANGES OF THE NORTHERN OKHOTSK AREA (MAGADAN REGION) DURING LATE PLEISTOCENE-HOLOCENE FROM GRYAZEVOE LAKE

The study of diatoms from the sediments of well Gz-1 (Gryazevoe Lake, Magadan Region) allowed us to identify the response of diatom communities to environmental changes in the Late Pleistocene and Holocene and establish the main stages of the transformation of the lake ecosystem. Three diatom zones and four subzones were identified based on changes in the concentration of diatom floras in sediments, the ratio of representatives of ecological groups and dominants, reflecting the evolution trend of the lake diatom flora during the transition period from the last glacial maximum to the Holocene. This trend is similar to the changes in the lake diatom communities of the Arctic regions noted for the last millennium in terms of the change of taxonomic composition and dominants. The data of diatom studies, lithological and petrophysical characteristics of sediments indicate that the most significant changes in the natural environment occurred at the Pleistocene-Holocene boundary from 12.6 to 11.1 thousand years ago.

New human fossil from the latest Pleistocene levels of Grotta Romanelli (Apulia, southern Italy)

Grotta Romanelli can be counted among the most interesting sites for the late Upper Palaeolithic of the Mediterranean area, since returned a consistent record of lithic artefacts, faunal remains, mobiliary and parietal art, and human fossils which represent the least-known materials from the context. The resumption of the investigations in 2015, after 40 years of inactivity in the cave, provided relevant results. During the 2019 campaign, a distal phalanx of the hand was recovered in the so-called terre brune levels, providing for the first time a clear stratigraphic and chronological reference for the human fossils record of Grotta Romanelli. In addition to morphological description and age estimation, the new finding is here analyzed using 3D Micro-CT scans. The new human fossil confirms the exceptional richness of the paleoanthropological record of Grotta Romanelli, opening new avenues of investigation and posing crucial questions on the use of the cave and cultural practices at the Late Pleistocene-Holocene boundary.

RECORDS OF ENVIRONMENTAL CHANGES IN LACUSTRINE-SWAMP SEQUENCES WITHIN MOUNTAIN AREA OF THE ITURUP ISLAND SINCE THE LATE GLACIAL

We received a unique material on the natural environment development for the last 12 400 cal. yr. BP in the central part of Iturup Island. The high-resolution paleoreconstructions were based on multi-proxy study of the paleolake sediments found on the plateau (height 400–420 m) located northwest of the Baransky Volcano. For the first time, a record of paleogeographic events was obtained for the Late Glacial and the early Holocene. The age model is based on 9 radiocarbon dates. Diatom analysis allowed us to distinguish 11 stages of lake-swamp evolution. The paleolake reached its maximum depth at ~9 890–7 900 cal. yr. BP and became extinct at 1 400 cal. yr. BP. The stages of vegetation development and the factors determining the change of landscapes have been restored. The Younger Dryas cooling recorded in Iturup was characterized by humidity changes. The role of forest vegetation abruptly increased at the Pleistocene-Holocene boundary of ~11 470 cal. yr. BP) under warmer climatic conditions. Distribution of shrub pine as an indicator of stable snow cover was analyzed. Dark-coniferous forests existed in the mountainous part of the island since the Late Glacial and were most widely developed in the early Holocene. The onset of birch forest expansion at 6 200 cal. yr. BP was associated with the intensification of volcanic activity and frequent ash falls. A number of cold events were identified, whose manifestations were enhanced by the weakening of the Soya warm current. The intensive transfer of allochthonous pollen from the southern Kuril Islands and the Japanese Islands at 3 540 cal. yr. BP is a sign of cyclogenesis intensification in the Kuril Islands. Manifestations of the Holocene climatic rhythms in the landscape development of the Iturup mountainous part, as well as the influence of warm and cold currents and other regional factors, were analyzed.

Paleo-vegetation and environmental history of Natural Trap Cave based on pollen and carbon isotope analyses

Pollen and carbon isotope data from Natural Trap Cave provides insights into the environmental conditions of the Bighorn Basin, in north-central Wyoming, USA during the time intervals 151.1 to 132.2 cal ka BP, 51.8 to 17.4 cal ka BP, and 10.4 cal ka BP to present. Similarities between the buildup of the penultimate and last glacial maxima include abundant Artemisia, Amaranthaceae, Asteraceae, and Poaceae pollen, which, when combined with high δ13C values (>−25.0‰) and low plant discrimination values (18.0–19.0‰) from sedimentary organic matter, indicate steppe-like, cold-dry conditions. Between 151 and 142.5 cal ka BP, abundant Poaceae associated with much lower δ13C values (−28.0‰ to −26.0‰) and higher plant discrimination values (19.0‰–21.0‰) could be indicative of relatively wet summers. Similarly, after 25 cal ka BP increases in Poaceae may indicate wet conditions during the growing season. Holocene conditions differ from the earlier sections of the record, with greater arboreal pollen abundance (i.e., Pinus), consistent with woodland expansion in the region. Carbon isotope data from sedimentary organic matter show the Holocene was more humid than the glacial conditions of the late Pleistocene. This is especially clear at the start of the Holocene when a large negative carbon isotope excursion (CIE, < −28.0‰) occurred, providing a distinct chemostratigraphic marker defining the Pleistocene-Holocene boundary within these cave sediments. The association of this CIE with a pronounced spike in Pinus pollen supports an interpretation of a short-lived interval (<1000 years) of extremely warm, wet, forested conditions at this site.

Sedimentation and organic content in the mires and other sites of sediment accumulation in the Sydney region, eastern Australia, in the period after the Last Glacial Maximum

This research reports on a synthesis of radiocarbon (14C) dates and the organic content from a variety of depositional sites in a relatively small region in humid eastern Australia centred on Sydney. We focused on basal dates, changes in accumulation rates and the organic content of these sediment records in the period post-dating 21 thousand years ago to make inferences about past environmental conditions, or to infer the timing of past environmental change. We found that low rates of sediment and organic accumulation at the Last Glacial Maximum continued well into the late Pleistocene. The average rate of sediment deposition and organic content increased from about 14.5 calibrated kiloanni before present (cal ka BP), perhaps coincident with Meltwater Pulse 1A, but this was then checked by dry conditions during the Antarctic Climatic Reversal chronozone. An abrupt increase in the average rate of sediment accumulation coincided with the Pleistocene-Holocene boundary (at 11.7 cal ka BP), and this continued until about 9.2 cal ka BP, largely coinciding with the Antarctic thermal maximum, and probably reflecting reduced moisture availability in the Sydney region. Indication of depressed temperature and a more positive moisture availability, from about 9 to 7.6 cal ka BP, witnessed the fastest increase in the number of sites than at any other time. An overall drier early Holocene abruptly altered at about 7.5 cal ka BP and a mid-Holocene ‘optimum’ in moisture availability extended to 6.2 cal ka BP. The compilation of organic contents of the mid-late Holocene suggests environmental variability, but El Niño frequency or strength is not implicated as a driving force. Increased organic productivity, especially after 2.8 cal ka BP, corresponded to a peak in summer insolation, and associated seasonality of insolation and this is likely to have resulted in increased, or more consistent, summer rainfall and easterly air flow into the Sydney region. In contrast to previous generalisations about changes in south-eastern Australia during the Holocene, which have often relied on palaeoenvironmental records from further south, the southward migration of the intertropical convergence zone during the Holocene had vastly different synoptic outcomes in the Sydney region, with the early Holocene drier as continental air dominated, and the late Holocene wetter, as the synoptic conditions saw more tropical and easterly airflow. This work demonstrates the danger in making generalisations across regions and highlights the utility of the compilation of data at a homoclimatic, regional scale.

Molecular characterization of the spectacled caiman (Caiman crocodilus) in the upper Magdalena River basin, Colombia: Demographic and phylogeographic insights

Maintenance of high levels of genetic diversity is crucial for the recovery of overexploited species and gaining knowledge of genetic diversity of natural populations is crucial to define effective conservation strategies. Spectacled caimans (Caiman crocodilus) were unsustainably exploited for decades in Colombia causing drastic population reductions with unknown effects on genetic structure. We molecularly characterized three spectacled caiman populations from the upper Magdalena River basin (UMRB), analyzing them within the context of the trans-Andean C. c. fuscus sensu stricto lineage, assessing nucleotide and genetic diversity, demographic history, and phylogeography at different scales. Seventeen of the 23 mitochondrial haplotypes currently described for Colombia are present in the UMRB, showing high levels of genetic diversity even when compared with the trans-Andean region (uncorrected genetic distances 0.00-0.87%). Mutational steps between closest haplotypes ranged from one to four while the most differentiated haplotypes were separated by 19 mutational steps across the whole trans-Andean region. Distribution of pairwise nucleotide differences and raggedness tests showed unimodal patterns of mismatch distribution curves fitting the sudden expansion model. Average time since demographic expansion for UMRB, Colombia, and trans-Andean region were inferred as 10,540, 7,591, and 7,071 years before present, respectively, placing the latest expansion close to the Pleistocene-Holocene boundary. Intriguingly, samples from Tolima were overall more related to those collected from Panama and Costa Rica (0.34 ± 0.15%) than the ones collected across Choco (0.45 ± 0.15%), Cauca (0.70 ± 0.09%), and Nariño (0.60 ± 0.14%) departments. We discuss our genetic findings in the context of the management policies carried out in the country during the last decades (unsustainable and sustainable use, and population restocking), evaluating the implications of these events for the genetic integrity and conservation of the species.

Fossil Asiatic Brush-Tailed Porcupine Atherurus macrourus (Hystricidae, Rodentia) from Northern Vietnam (Bud Cave, Pleistocene-Holocene Transition).

The lower jaw and dental remains of the brush-tailed porcupine are described from the Pleistocene-Holocene boundary deposits of the Bud cave in northern Vietnam. In terms of the average length of the cheek teeth, this porcupine is somewhat larger than the modern Atherurus macrourus (Linnaeus, 1758), but slightly smaller than the Pleistocene A. karnuliensis Lydekker, 1886; relatively small incisors make it possible to assign the form from the Bud сave to A. macrourus. The finding is the first fossil record of this species in Vietnam.