Holocene Boundary Research Articles

Coastal landscape evolution in the Wilpattu National Park (NW Sri Lanka) linked to changes in sediment supply and rainfall across the Pleistocene–Holocene transition

Coastal sand dunes are sediment archives which can be used to reconstruct periods of aridity and humidity, past wind strength and variations in the sediment supply related to sea‐level changes. In this manner, the sedimentary record of fossil coastal dunes in Sri Lanka provides evidence for environmental and climatic changes during the late Pleistocene and Holocene. As yet, these environmental shifts are poorly resolved because the sedimentary facies and their depositional architecture have not been studied and only very few age constraints are available. Facies analysis of a lithological section at the Point Kurdimalai sea cliff in the Wilpattu National Park (NW Sri Lanka) reveals a striking resemblance to the stratigraphic succession associated with the Teri Sands in southeastern India, which is better dated. The reason is that deposition occurred under the same geological, climatic and geomorphological conditions in the two regions. This special situation allows for litho‐ and climate stratigraphic correlations across the Gulf of Mannar and links the landscape evolution at Point Kudrimalai to late Quaternary climatic events and sea‐level changes. Our results show that the formation of red coastal dunes (Red Beds) in Sri Lanka was a multi‐phase process across the Pleistocene–Holocene boundary and hence the differentiation between an Older Group of Plio‐Pleistocene age (including the Red Beds) and a Younger Group of Holocene age in the Quaternary stratigraphic chart for Sri Lanka is not justified.

TRANSFORMATION OF THE NEOEUXINIAN LAKE INTO THE BLACK SEA AT THE NEOPLEISTOCENE - HOLOCENE BOUNDARY ON PALEONTOLOGICAL DATA

Problem Statement and Purpose. The transformation of the Neoeuxinian Lake into the Black Sea at the Neopleistocene-Holocene boundary represents a considerable interest for Quaternary geology. The age of the boundary, the character of the transformation (gradual, gradual but with oscillations, prominent, or catastrophic), and changes in salinity are highly controversial. The main goal of the paper is to contribute to the controversial subjects using the high-resolution paleontological (foraminifera. ostracoda. and mollusks) data supplemented by palynological data and radiocarbon datings.Data & Methods. The study area is located within the northwestern (Ukrainian) and western (Bulgarian) shelf of the Black Sea. The material for micropaleontological study was obtained by the coring using the Ukrainian research vessel “Vladimir Parshin” and the Bulgarian research vessel “Academician L. Orbeli" in 2008 and 1976. respectively. All cores are located outside the isobath 100 m. The results of previous micropaleontological investigations are used for comparison. Microfauna was investigated according to the method of V. V. Yanko. Radiocarbon dating was performed by AMS (Core 38) or conventional - P-counting (Core 2345) methods on Mytilus and Dreissena shells.Results. Foraminifera are not adapted to freshwater environment. As a rule, the border between brackish and freshwater environment can be traced by their disappearance, with the exception of Allogromiida species with organic tests, which were not found in the studied material. For this reason, the presence of relatively diverse calcareous foraminifera suggests that the Neoeuxinan lake was brackish. Geochemical (salinity of pore water) and micropaleontological data are in full agreement.If there would not be inflow from the Mediterranean Sea until 7.2 ka BP or 8.4 ka BP according to the first and second catastrophic flooding scenarios of Ryan et al., no Mediterranean immigrants would be present in sediments older than 8.4 ka BP.However, they are present in sediment columns as can be seen from our and other researchers investigations. If the colonization of the Neoeuxinan lake by Mediterranean immigrants would be prominent or catastrophic, there would be a sharp increase in the species diversity and quantity of forammifera. ostracods and mollusks. However, these parameters increase gradually. The boundary between the Upper Neopleistocene and Holocene lies within 9 and 10 thousand years ago. The transformation of Neoeuxinan lake into the Black Sea was gradual: from brackish to a semi-marine, and then to a marine water body in course of the Mediterranean transgression during Holocene. The increase in salinity- occurred gradually over 3600 years, while the rate of penetration of sea water was about 0.05-1.7 cm a-1. The Holocene marine transgression was progressive in nature, intensifying with the transition from the early to late Holocene. The high-resolution micropaleontological study of Core 38 provides new data on the last pages of the development of the brackish Neoeuxinan lake that are mostly absent in other cores. Changes in the foraminiferal assemblages on the Pleistocene - Holocene boundary depend on the facies. They are more pronounced in marine facies compared to shallow ones, especially in areas affected by paleorivers. Palynological data provide evidence for cold climate at the end of the Neoeuxinian time.

The Rate of Mitochondrial Cytochrome b Gene Evolution according to the Analysis of Recent (about 12 000 Years) Isolation of Charrs Salvelinus of Lake Kronotskoe

The nucleotide substitution rate of the mitochondrial cytochrome b gene is estimated on the basis of the genetic differences of charr populations (Salvelinus) with a known time of isolation (Upper Pleistocene–Holocene boundary) as 3.11 × 10–8 substitutions/position/year (95% confidence interval: 2.59 × 10–8–3.64 × 10–8). This estimate is about five times higher than the one obtained for this gene when considering long time intervals of divergence of salmonid fishes (phylogenetic rate)—0.66 × 10–8 (0.56 × 10–8–0.77 × 10–8). Thus, the rule of decrease in mtDNA nucleotide substitution rate estimates while moving from the recent calibration dates (thousand years) to the ancient ones (millions of years) applies also to the lineage of salmonid fishes.

Taphonomic and paleoecological aspects of large mammals from Sudety Mts (Silesia, SW Poland), with particular interest to the carnivores

The rediscovery of old collections and revision of the fossil material from more than 30 Sudeten caves and rock shelters allow reconstructing the faunal changes during the Late Pleistocene and the Holocene. We found that the composition of mammalian assemblages of Sudety Mts during MIS 3 differed significantly from the Holocene and modern one, and reflected the colder climate. Mammals belonging to the Mammuthus-Coelodonta faunal complex inhabited open flattened lowlands (Bohemia, Moravia and Silesia) surrounding Sudeten area. Several large carnivores (Canis lupus spelaeus, Ursus arctos priscus, Ursus ingressus, Gulo gulo, Mustela eversmanii, Panthera spelaea spelaea, Crocuta crocuta spelaea) as well as herbivores (Mammuthus primigenius, Coleodonta antiquitatis, Megaloceros giganteus, Rangifer tarandus, large form of Equus ferus, Bison priscus, and Ovibos moschatus) made up the core of this assemblage.Our studies showed that most of these faunal elements were also present in Sudety Mts, despite the previous opinion that these mountains formed an effective natural barrier during the Late Pleistocene. Besides, it seems that during cold phases they could be refugees for forest animals, which were also present in the Mammuthus-Coelodonta faunal complex, but lower quantities. They avoided flat treeless Silesian lowlands and concentrated in mountainous and hilly regions. In this context, during the Late Pleistocene Sudety Mts were a “forested island” confined to elevated areas or river valleys. Range extensions, contractions, and continuations on different scales resulted in mammalian paleoassemblages which differed in particular from the modern ones.The analysis of the mammal faunas from Sudeten sites revealed that there were three heterochronous mammalian faunal complexes replaced each other throughout the Late Pleistocene and the Holocene. Differences between these assemblages resulted from changes in morphology, areas and extinction of several species. The existence of different faunal elements was distinguished by the chronological and geographical change in the structure of mammalian assemblages. At the end of MIS 3 most of the cold-adapted species from the Mammuthus-Coelodonta faunal complex like Ursus ingressus, Panthera spelaea spelaea, Coelodonta antiquitatis, Bison priscus, and Megaloceros giganteus disappeared.During the second phase, at the latest Pleistocene and the Holocene boundary, all the species of the Mammuthus-Coelodonta faunal complex still not became extinct. Several species from this assemblage disappeared later in the Holocene. It should be noted that the role of the human in the changes of faunal complexes and species extinctions during the Late Pleistocene and the Holocene in the Sudety Mts cannot be so far demonstrated.

Rabbits and Bergmann’s rule: how cold was Portugal during the last glaciation?

Abstract Osteometric data from > 450 modern wild rabbits, mostly from Portugal, Spain and France, show an inverse correlation between their size and the temperature of the environment, in accordance with Bergmann’s rule. Similar measurements made on some 1660 rabbit bones from 14 Portuguese late Pleistocene and Holocene archaeological sites indicate that rabbits became considerably smaller at the Pleistocene–Holocene boundary. Thus, rabbit size varies or varied with temperature both today and in the past. A direct temperature–size relationship was assumed, and the regression of modern rabbit bone size on temperature was then used to calibrate the temperature equivalent for the change of size of rabbit bones in the past. The result indicates a Last Glacial Maximum to present-day difference, Δt°, of 7 or 8 °C. An alternative interpretation that does not assume a direct temperature–size relationship would indicate that the environment in Portugal 15 000–30 000 years ago was similar to that in northern France today.

Hunter-gatherer land management in the human break from ecological sustainability

Evidence that human societies built on agricultural subsistence have been inherently ecologically unsustainable highlights the value in exploring whether any pre-agricultural subsistence approaches were ecologically sustainable or nearly so. The land management practices of some hunter-gatherer societies have been portrayed as sustainable, even beneficial. Research suggests such practices may fruitfully inform contemporary land management. As a human subsistence foundation, however, they may not have been ecologically sustainable. Figuring centrally in the late Pleistocene shift from immediate-return to delayed-return hunting and gathering, they enabled population growth, helped make possible the development of agriculture, and appear to have caused early environmental degradation. Consistent with this argument is research locating the origins of the Anthropocene near the Pleistocene–Holocene boundary, as societies were taking greater control of food production. It appears then that immediate-return hunting and gathering, which involved little or no land management, was the human lifeway most closely approaching ecological sustainability. Wider recognition of this idea would assist in understanding and addressing today’s ecological challenges.

Stable isotopic composition of rice grain organic matter marking an abrupt shift of hydroclimatic condition during the cultural transformation of Harappan civilization

Several hypotheses have been proposed to solve the conundrum of the cause of transition of Harappan civilization to a de-urbanized form in its Late Phase. In view of this, high-resolution off-site palaeoclimatic records along with archaeological findings provide strong evidence of an abrupt climate change ∼4000 yr BP (before present) that coincides with the civilization's cultural transition. The present study investigates whether this climatic shift recorded in palaeoclimate archives (speleothem, lake and marine sediments) at remote locations can be traced to the human settlements of Harappan civilization. This was accomplished by analyzing the remains of rice cereal-a highly water sensitive crop. The analysis involved measuring carbon and nitrogen isotopic compositions (δ13C, δ15N) of well-preserved rice grains recovered from archaeological sites belonging to the Harappan civilization and other contemporary regional cultures, representing the time windows between 4520 and 3400 yr BP. The parameter of intrinsic water use efficiency (WUEi) was used as an index for water availability in the rice crop's growth environment and was ascertained based on δ13C values measured in the bulk grain organic matter (OM). The observed WUEi values ranged between 49 and 69 μmol mol−1 and captured the variation in water availability. The δ15N values ranged from 5‰ to 6.5‰, thereby allowing us to confirm the role of climate in controlling δ13C variation in the archaeological grains. The present findings will extend the usage of archaeobotanical cereal remains to deduce environmental changes at human settlements and will further our understanding of the process of Harappan cultural adaptation in response to decline in southwest monsoon at the Middle-Late Holocene boundary.

TRACING ORIGIN AND COLLAPSE OF HOLOCENE BENTHIC BASELINE COMMUNITIES IN THE NORTHERN ADRIATIC SEA

The shallow northern Adriatic Sea has a long history of anthropogenic impacts that reaches back many centuries. While the effects of eutrophication, overfishing, pollution, and trawling over recent decades have been extensively studied, the major ecological turnovers during the Holocene as a whole remain poorly explored. In this study, we reconstruct ecological baselines defining benthic ecosystem composition prior to major anthropogenic changes at four stations characterized by low sedimentation and millennial-scale time averaging of molluscan assemblages. We discriminate between natural and anthropogenic drivers based on (1) stratigraphic changes in the composition of molluscan communities observed in sediment cores and (2) changes in concentrations of heavy metals, pollutants, and organic enrichment. The four 1.5-m long sediment cores reach back to the Pleistocene–Holocene boundary, allowing for a stratigraphic distinction of the major sea-level phases of the Holocene. During the transgressive phase and maximum flooding, sea-level and establishment of the modern circulation pattern determined the development of benthic communities in shallow-water, vegetated habitats with epifaunal biostromes and, in deeper waters, with bryozoan meadows. After sea-level stabilization, the composition of these baseline communities remained relatively uniform and started to change markedly only with the intensification of human impacts in the late highstand, leading to a dominance of infauna and a decline of epifauna at all sites. This profound ecological change reduced species richness, increased the abundance of infaunal suspension feeders, and led to a decline of grazers and deposit feeders. We suggest that modern soft-bottom benthic communities in the northern Adriatic Sea today do not show the high geographic heterogeneity in composition characteristic of benthos prior to anthropogenic influences.

Deglaciation history of Lake Ladoga (northwestern Russia) based on varved sediments

Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP, when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP, older than previously assumed. Varve sedimentation covers the Bølling/Allerød interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselkä II moraine north of Lake Ladoga, by c. 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c. 9.5 cal. ka BP, characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c. 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c. 4.5 cal. ka BP until present.

Coastal lake records add constraints to the age and magnitude of the Younger Dryas ice‐front oscillation along the Skagerrak coastline in southern Norway

ABSTRACTBasal records from nine lake basins, located within a small area inside the Younger Dryas Ra moraine in southern Norway, were analysed and radiocarbon dated. Six reworked shell fragments from the lowermost facies in five different basins date to the Bølling–Allerød chronozone and are interpreted to represent an ice‐free coastline before a Younger Dryas ice sheet readvance of at least 8 km. The widespread shell fragments within the Younger Dryas ice margin but pre‐dating the Younger Dryas are demonstrated using a systematic survey of the lowermost strata in a collection of lake basins. A further 13 dated samples, mostly in situ articulated bivalves found in clayey silt overlying the basal facies, yielded overlapping ages close to the Younger Dryas–Holocene boundary. The 13 shell dates, along with two additional similar ages obtained on terrestrial plant macrofossils from basal strata in two basins near the marine limit, provide a minimum‐limiting age of 11.6k cal a BP for ice sheet retreat from the Ra moraine. This suggests that the ice sheet in south‐east Norway retreated from its Younger Dryas maximum position nearly a thousand years later than previously assumed. Similar systematic approaches may lead to improved ice sheet reconstructions from other formerly glaciated coastlines.

Mid and Late Holocene sea level variations in the Canary Islands

The eastern coast of Fuerteventura (Canary Islands, Spain) hosts the most complete and representative emergent Holocene marine deposits in the middle latitudes (27°N to 30°N) of the eastern Atlantic Ocean. The deposits consist of berms of gravel and foreshore sands which form beach rocks comprising >62 bed sets, with each bed set containing dozens of individual laminations suggesting a cyclical cause as, for example, the orbital movement of the Earth. Calibrated radiocarbon ages place a group of older Holocene highstands of Fuerteventura at around the Mid-Late Holocene boundary (around 4.2 kyr B.P.), and another group of more recent highstands in the Dark Age Period (around 1.4 kyr B.P.) of the Northern Hemisphere. They have been recorded at 4 m and 3.5 m apmsl respectively. The present-day tidal amplitude is around 3 m. Assuming a similar value for the Holocene, the corresponding relative sea level rises were around 2.5 m and 2 m apmsl respectively. Moreover, terrestrial deposits intercalated between the marine deposits indicate a lowering of the sea level at ca. 3 kyr B.P. When the sea levels reached their highstands during these two periods, the sea surface temperatures (SST) at the southern tip of the cold Canary Current were, respectively, 0.5 and 1.5 °C colder than the present-day SST (21.23 °C). The fossil fauna content confirms that these highstands occurred in cold conditions. In contrast, the present SST reaches the range of temperatures of the Holocene Optimum in the area.Fuerteventura has been vertically stable since the last interglacial period, and the sedimentology of the deposits precludes an origin from tsunamis or storms. This island is in a far-field region in terms of glacial isostatic adjustment (GIA) processes. Here, we suggest that the deposits may be related to GIA and ice mass losses effects in the Southern Hemisphere.

Influence of Climate Changes in the Late Pleistocene–Holocene on Composition of Bottom Sediments of the Selenga–Buguldeika Saddle, Lake Baikal

The study of bottom sediments of Lake Baikal recovered by submarine drilling at the Selenga–Buguldeika saddle (core VER93-2 st. 24GC) allowed us to reconstruct the climatic events in the Baikal region in the last 20–25 k.y. On the basis of the data on distribution of chemical elements in the core section, the mineral composition of sediments was calculated by the physicochemical modeling method. A study of how ratios of clay minerals changed in the section allowed us to identify the Pleistocene–Holocene boundary, Bolling–Allerod postglacial warming, and Late Dryas cooling. The calculated data on mineral composition of bottom sediments from the core VER93-2 demonstrate a good fit to the X-ray diffraction analysis results. The proposed approach can be used in calculation of mineral compositions of other sedimentary sequences with known chemical composition.

A natural adaptive syndrome as a model for the origins of cereal agriculture.

A novel explanation of the origin of cereal agriculture is proposed, based on the ecology and adaptive morphology of wild cereals ancestral to our founder cereals (einkorn, emmer and barley). Wild cereals are unusually large-seeded. A natural evolutionary-ecological syndrome relates large seed, awns and monodominance (LAM). Awns bury attached seeds in the soil, protecting seed from fire; buried seed needs to be large to emerge on germination; large seeds, growing without competition from small-seeded plants, will produce monodominant vegetation. Climatic and edaphic instability at the Pleistocene-Holocene boundary would have provided an impetus for the spread of annual ruderal grasses. LAM grassland provided an obvious natural model for the origins of cereal agriculture. Subsequent field management would mimic the natural niche (MNN). The fact that monodominance is a long-standing character of the natural LAM syndrome validates cereal monocultures (now producing most of our food). An alternative explanation of crop domestication, by auditioning a great range of species for a human-constructed niche (NCT), is rejected.

Coupling of the Intertropical Convergence Zone and Southern Hemisphere mid-latitude climate during the early to mid-Holocene

Conceptual models predict a tight coupling between the Intertropical Convergence Zone (ITCZ) and the Southern Westerly Winds (SWW) in response to glacial-interglacial transitions, yet little is known about this relationship under Holocene boundary conditions. Here we present a synthesis of Holocene pollen data from the southwest Pacific mid-latitudes that tracks changes in the SWW. Comparison of our SWW paleoclimate records with data tracking the ITCZ, oceanic circulation, and insolation reveals clearly synchronous and in-phase ITCZ-SWW dynamics between 12 and 5 ka, indicating a tight coupling between the tropics and southern mid-latitudes in response to ocean circulation and insolation. An apparent decoupling of the SWW and ITCZ in the Pacific region after 5 ka is attributable to the overriding influence of the El Nino–Southern Oscillation (ENSO) over the proxy data.

Science and Poetry in Deep Time

The ice core sample that marks the beginning of the geological epoch known as the Holocene is archived in a freezer at the University of Copenhagen.1 Drilled in 2003 from the central Greenland ice sheet, the sample provided enough evidence for the International Union of Geological Sciences to endorse the proposal that the Pleistocene–Holocene boundary occurred 11,700 calendar years ago.2 In scientific terms, the 2-kilometre-long ice core exhibits ‘an abrupt shift in deuterium excess values, accompanied by more gradual changes in δ18O, dust concentration, a range of chemical species, and annual layer thickness’, marking the distinction between two geological ages. To the layperson, the climactic event is better recognised as the end of the Ice Age, and the beginning of the current warm period in which we live.3 Or, in which we believed we lived. On 29 August 2016, the International Geological Congress’s Working Group on the Anthropocene (WGA) announced the culmination of seven years’ research into the subdivision of recent geological time: humanity’s impact on the Earth – encompassing its various and interconnected ecological, biological, and geological systems – is now recognised as so momentous that the relatively young Holocene has been superseded.4 The Anthropocene has arrived.

Palaeoecology: Agriculture emerges from the calm.

New palaeoecological data from New Guinea reveal that climatic change at the Holocene boundary is unlikely to have driven early agriculture in the region. More nuanced understanding of how humans responded to past climate change could better inform our responses in the future.

Contrasting alluvial architecture of Late Pleistocene and Holocene deposits along a 120-km transect from the central Po Plain (northern Italy)

High-resolution investigation of a ~120-km-long transect along the course of the modern Po River, northern Italy, revealed marked changes in alluvial architecture across the Pleistocene–Holocene boundary. Along the whole transect, a 20- to 30-m thick sheet-like succession of Late Pleistocene fluvial sands is invariably overlain by silt and clay deposits, with isolated fluvial bodies of Holocene age (<9.4cal ka BP). The Holocene succession displays consistent downstream changes in facies architecture: well-drained floodplain deposits are transitional at distal locations to increasingly organic, poorly drained floodplain to swamp facies associations. Thick paludal facies extend continuously up to 60km landward of the Holocene maximum marine ingression, about 90km from the modern shoreline. Based on 28 radiocarbon dates, the abrupt change in lithofacies and channel stacking pattern occurred at the transition from the last glacial period to the present interglacial, under conditions of rapid sea-level rise. The architectural change from amalgamated, Late Pleistocene sand bodies to overlying, mud-dominated Holocene units represent an example of chronologically well-constrained fluvial response to combined climate and relative sea-level change. The overall aggradational stacking pattern of individual channel-belt sand bodies indicates that high subsidence rates continuously created accommodation in the Po Basin, even during phases of falling sea level and lowstand.

INTIMATE (Integration of Ice-core, Marine and Terrestrial Records) 20 Years on: Retrospect and Prospect

The INTIMATE (Integration of ice-core, marine and terrestrial records) project, the successor to the North Atlantic Seaboard Programme of International Geological Correlation Programme (IGCP-253) ‘Termination of the Pleistocene’, began in 1995 with the aim of integrating proxy climate records from around the North Atlantic during the Last Termination (18–8 ka BP). The INTIMATE remit has since expanded geographically to include the entire Atlantic basin and Australasia, while an extended temporal framework now covers the early Holocene and the Last Glacial cycle. This short paper outlines the principal achievements of the INTIMATE research community, which include the development of an event stratigraphy for the North Atlantic region; the establishment of protocols for ice–land–ocean correlation; important contributions to geochronology, most notably to tephrochronology, and to palaeoenvironmental and palaeoclimatic reconstructions; and the designation of the Greenland ice-core record as the global stratotype for the Pleistocene–Holocene boundary. Future directions of the INTIMATE programme are also briefly considered.

The Southern Divide: Testing morphological differences among bifacial points from southern and southeastern Brazil using geometric morphometrics

Bifacial points have been used to characterize the “Umbu” tradition in southern and southeastern Brazil. This archaeological tradition has been related to sites dated from the late Pleistocene-early Holocene boundary to near historical times. Such a huge temporal range and vast territory have suggested the existence of greater diversity within this tradition that has been ignored thus far due to the lack of systematic regional studies of such points. Through geometric morphometric analysis, this article aims to test the hypothesis that there are substantial differences in the Holocene bifacial points associated with the Umbu tradition in southeastern Brazil. Five landmarks were digitized in standardized photographs from 658 points from the states of São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul. The results show that points made by groups from southeastern Brazil (São Paulo state) present a very distinct morphology (size and shape) in comparison to those made by the southern groups (Paraná, Santa Catarina and Rio Grande do Sul). This would indicate a regional identity shared only by some groups from São Paulo (at least regarding the projectile points). It is possible that Umbu tradition presents a more restricted range, both in chronological and spatial terms, than the one proposed so far.

Paleobiology of sabretooth cat Smilodon populator in the Pampean Region (Buenos Aires Province, Argentina) around the Last Glacial Maximum: Insights from carbon and nitrogen stable isotopes in bone collagen

The sabretooth cat Smilodon populator was the largest felid in South America. It appears in the fossil record in the Early Pleistocene, as an immigrant from North America, and becomes extinct around the Pleistocene–Holocene boundary. The carbon and nitrogen stable isotopic values of collagen were measured for skeletal remains from Smilodon specimens ranging in age from 25 to 10kyrBP, for the first time in the Pampas region of Argentina. By comparison with similar values obtained on co-eval predators such as Protocyon (large canid) and Panthera onca (jaguar) and a range of potential prey, such as giant ground sloths, glyptodontids, Macrauchenia, Toxodon, equids, cervids, and rodents, it could be established that Smilodon consumed essentially large prey from open landscape, such as Macrauchenia and giant ground sloths during the last 15,000years of the Late Pleistocene in the Pampa region. It was possibly competing with the large canid Protocyon but the jaguar was apparently feeding on smaller size prey. A more humid climate at the beginning of the Holocene might have been unfavorable to this large predator and could have contributed to its extinction. These results also provide an important insight to understand the ecological processes involved in the Great American Biotic Interchange.