Radiometric Chronology Research Articles

Montane Ecoclines in Ancient Central Asia: A Preliminary Study of Agropastoral Economies in Juuku, Kyrgyzstan

In this paper, we use preliminary archaeological data spanning the Iron Age through Medieval periods (ca. 800 BCE to 1200 CE) in the Juuku Valley on the south side of Lake Issyk-Kul to model land use across vertical mountain zones. We have (1) established a radiometric chronology; (2) conducted test excavations of an Iron Age settlement at 2100 m asl and a Turkic period burial at 1934 m asl; (3) undertaken preliminary archaeobotanical research; and (4) performed pedestrian surveys. Seed remains of wheat (Triticum aestivum), barley (Hordeum vulgare), broomcorn millet (Panicum milaceum) and foxtail millet (Setaria italica), and legumes were recovered in very small quantities from both sites. We compare these preliminary archaeobotanical results with previously published data from the Talgar Iron Age settlements on the north side of the Tian Shan Mountain range in Kazakhstan. A small assemblage of faunal remains found at the Turkic period kurgan and from a profile at the upland Iron Age settlement demonstrates the practice of herding sheep/goats, cattle, and horses in the Juuku Valley. The goal of this study was to test the hypothesis that pastoral transhumance and agropastoralism were interchangeable economic strategies used by peoples in the Iron Age through Medieval periods in mountain-river valleys between 600 m to 2100 m asl. These economic strategies combined the pasturing of sheep, goats, cattle, and horses with the cultivation of cereals were adapted to different vegetational zones along a vertical gradient. This paper is based on preliminary research of upland sites of the Juuku Valley in Kyrgyzstan, and initiates a long-term research study of four millennia of settlements that ranged from pastoral transhumance and combined mountain agriculture using survey data and test excavations.

New insights into the historical translocation of the Algerian hedgehog and pine marten throughout the Balearic Islands (Western Mediterranean): refining the radiocarbon‐based chronology

AbstractIn this paper, we refine the colonisation timeframe of pine marten (Martes martes) and Algerian hedgehog (Atelerix algirus) to the Balearic Islands synthesising their occurrence records and providing an accurate chronology through new directly 14C dated archaeological bone samples. The new dates are significantly earlier than previously reported finds; therefore, both cases currently represent the earliest records for the human‐mediated translocation of these species in Europe. These new data not only provide further accurate resolution for previous historical translocation hypothesis but also expand the geographical scope throughout the archipelago. The sequence and timing of introduction events are embedded in different historical timeframes. The time of arrival of the pine marten is now established in the early Roman period, a period that supported a huge wave of introduced alien species into the Balearics. For the Algerian hedgehog, the new records further support the hypothesis that the Almohads were responsible for its introduction to these islands. Both examples illustrate how important it is to connect past translocation records to tighter radiometric chronologies through direct dating on bones of the implicated species.

Evidence for early asteroidal collisions prior to 4.15 Ga from basaltic eucrite phosphate U–Pb chronology

The late heavy bombardment (LHB) hypothesis, wherein the terrestrial planets are thought to have suffered intense collisions ca. 3.9 billion years ago, is under debate. Coupled with new dynamical calculations, re-examination of geochronological data seem to support an earlier solar system instability and a smooth monotonic decline in impacts, as opposed to a “cataclysm.” To better understand this collisional history, records from the asteroidal meteorites are required. Here, we report a uranium–lead (U–Pb) chronological dataset for eucrite meteorites thought to originate from the asteroid 4 Vesta; this dataset indicates to a continuous history of collisions prior to 4.15 Ga. Our 207Pb⁎/206Pb⁎ model ages of apatite [Ca5(PO4)3(F,Cl,OH)] and merrillite [Ca9NaMg(PO4)7] from three brecciated basaltic eucrites—Juvinas (4150.3 ± 11.6 million years ago (Ma); merrillite only), Camel Donga (disturbed around 4570–4370 Ma), and Stannern (4143.0 ± 12.5 Ma)—record multiple thermal metamorphic events during the period of ∼4.4–4.15 Ga. We interpret this to mean that Vesta or the vestoid cluster underwent multiple impacts and moderate high-temperature reheating during this time. The ages of ∼4.4–4.15 Ga are distinctly younger than the initial magmatic process on Vesta (>4.5 Ga) but are significantly older than a later “impact peak” based on some interpretations of 40Ar–39Ar chronologies (∼3.9–3.5 Ga). The intense collisions prior to 4.15 Ga on Vesta are at odds with the conventional LHB hypothesis but not inconsistent with the much earlier bombardment and monotonic decline scenario. Different radiometric chronologies of the asteroid likely represent the different stages of a continual collisional process. Conversely, the model 207Pb⁎/206Pb⁎ ages of apatite in the unbrecciated basaltic eucrite, Agoult, returned an age of 4524.8 ± 9.6 Ma. This may represent slow cooling from an earlier global reheating of the crust on Vesta at 4.55 Ga, as documented by other radiometric chronologies. The apatite in Juvinas recorded a coincident timing of 4516.9 ± 10.4 Ma, which could be due to either slow crustal cooling or impact.

The early occupation of the Eastern Pilbara revisited: New radiometric chronologies and archaeological results from Newman Rockshelter and Newman Orebody XXIX

For over 30 years, the radiometric chronologies of Newman Rockshelter and Newman Orebody XXIX have been central to archaeological discussions on the Pleistocene Aboriginal occupation of the Hamersley Plateau and greater Pilbara region. Until 2009, these two sites were heralded as having the oldest evidence of human occupation on the plateau, dating to the last glacial maximum (LGM) ∼ 26–20 ka. More recently however, the excavations at several other rockshelters have shown that ancient Aboriginal peoples occupied the Hamersley Plateau many thousands of years before the onset of the last glacial cycle, when regional climatic conditions were wetter and more amenable. This paper presents the results of our re-excavation of both Newman Rockshelter and Newman Orebody XXIX. Our research has resulted in the compilation and analysis of large lithic datasets for each of these sites and the construction of geo-chronologies using modern radiometric techniques, including AMS-radiocarbon dating and optically stimulated luminescence dating. These new radiometric chronologies and artefact data indicate that both sites were occupied between 45 and 40 ka. Despite having significant early occupational evidence, neither of the rockshelters present strong evidence for sustained or persistent site use during the LGM proper ca. 23–19 ka; however, there is substantial evidence for more routine occupation of these localities during the terminal Pleistocene and Holocene.

Coring and compaction: Best practice in blue carbon stock and burial estimations

A comparison of gouge and hammer coring techniques in intertidal wetland soils highlights a significant effect of soil compaction of up to 28% associated with the widely applied hammer coring method employed in Blue Carbon research. Hammer coring reduces the thickness of the soil profile and increases the dry bulk density, which results in an overestimation of the soil OC stock of up to 22%. In saltmarshes with multiple different soil units, we show that hammer coring is unsuitable for the calculation of OC stocks and should be avoided in favour of Russian or gouge cores. Compaction changes both soil dry bulk density and porosity and we show that resultant radiometric chronologies are compromised, almost doubling mass accumulation rates. While we show that the OC (%) content of these sediments is largely unchanged by coring method, the implication for OC burial rates are profound because of the significant effect of hammer coring on the calculation of soil mass accumlation rates.

Radiometric chronology and a morphometric analysis of a grinding stone with grooves from the Torihama shell mound

Radiometric chronology and a morphometric analysis of a grinding stone with grooves from the Torihama shell mound

Late Neandertals in central Italy. High-resolution chronicles from Grotta dei Santi (Monte Argentario - Tuscany)

Most of the Middle Palaeolithic evidence of Central Italy still lacks a reliable chrono-cultural framework mainly due to research history. In this context Grotta dei Santi, a wide cave located on Monte Argentario, on the southern coast of Tuscany, is particularly relevant as it contains a very well preserved sequence including several Mousterian layers. Research carried out at this site in the last years (2007–2017) allowed for a preliminary estimation of its chronology based on a set of radiometric determinations which place the investigated sequence in the time interval between 50 and 40 ka BP. Alongside the chronological issue, this paper mainly focuses on the geoarchaeological and zooarchaeological (micro and macro fauna) studies carried out on the materials retrieved during the 2007–2014 excavation fieldworks. The results of these studies are consistent with those from the radiometric chronology. A state of art concerning the MIS3 Italian sites is also provided in order to highlight the key role Grotta dei Santi may play in the assessment of late Neandertals’ behaviour within the framework of the Middle to Upper Palaeolithic transition of Central Italy.

A first absolute chronology for Late Neolithic to Early Bronze Age Myanmar: new AMS14C dates from Nyaung'gan and Oakaie

Abstract

A first radiometric chronology for the Khatt Shebib megalithic structure in Jordan using the luminescence dating of rock surfaces

Abstract This study presents the first instrumental radiometric date for one of the longest linear archaeological structures in southern Jordan ‘’Khatt Shebib’’. Quartz OSL profiles into the buried surfaces of two rocks from the structure near the modern village of Ayl enabled us to confirm that the surfaces had been exposed to light before burial, but to different degrees at various locations on the same rock. We identified layers as well-bleached where modelling suggested that the pre-burial signal was

L’attribution chronoculturelle des «objets arciformes» du Paléolithique supérieur. Apports de la datation directe de l’ébauche du Petit Cloup Barrat (Cabrerets, Lot, France) et discussion autour de l’hypothèse badegoulienne

Le Petit Cloup Barrat cave (Cabrerets, Lot, France) is located on the hill of Pech Merle, 800 metres from the famous Palaeolithic art cave. It opens onto the edge of a collapsed doline of 500 m2. Since 2003, the different excavations (by Castel and Chauvière, then by Castel) have revealed an important Upper Palaeolithic stratigraphy, with several archaeological assemblages. More than ten millennia have been recorded discontinuously in the various sedimentary complexes, with occupations dating from the end of the Gravettian to the Middle Magdalenian. Layer 4 of the deposit yielded an ‘ arciform object’ rough-out (so-called ‘ omega-like shape open ring’) made in antler. Until now, this morphotype was known only through the ten specimens discovered at the end of the 19th century in Le Placard cave (Vilhonneur Charente, France) and that of the so-called ‘ Cave à Endives’ archaeological collection (André David collection, Cabrerets, Lot). The direct dating of this rough-out using the AMS radiocarbon method (17720 ± 90 BP or 21770– 21122 cal. BP) was carried out in the Oxford laboratory. According to the chronological frameworks now available for south-western France, it seems to refer to the Badegoulian technical traditions. The implications of the absolute chronological positioning of this original object are important, first on the scale of Le Petit Cloup Barrat, but also for the Upper Palaeolithic ‘ arciform objects’. At Le Petit Cloup Barrat, Badegoulian occupations have been identified since 2003 inside the cave, following the discovery of lithic and osseous remains (respectively raclettes and antler flakes). They were discovered in layer c8a1. This layer has a remarkable sedimentary signature and was dated by the AMS radiocarbon method from a faunal remain (18595 ± 150 BP or 22876– 22101 cal. BP). The direct 14C dating of the open ring fills a gap in the radiometric chronology of the outer area of the main excavation sector, confirming the presence of the Badegoulian, already suspected through the recurrent demonstration of lithic “ markers” on the heart and bottom of layer 4. Moreover, the direct 14C dating of the ‘ omega-like shape open ring’ is consistent with another AMS date, in layer 4, from an antler flake produced by knapping (17800 ± 80 BP or 21838– 21292 cal. BP), technical waste characteristic of the Badegoulian. These two dates are older than one of a splinter fragment from the same layer, and produced by grooving (16,100 ± 70 BP or 19629– 19208 cal. BP). Taken together, they refer to the anteriority of the use of knapping in comparison to the groove and splinter technique, according to the general evolutionary model proposed elsewhere, without excluding, for the moment, the possible coexistence of other elements resulting from these two modes of blank production, at least on the scale of the sedimentary unit which contains them. The bone industry data are added here to other observations about typo-technological analysis of the lithic industry and radiometric data to confirm the diachrony in layer 4. The direct radiocarbon date of the ‘ omega-like shape open ring’ rough-out from Le Petit Cloup Barrat and its technical examination also provide a substantial complement to the study of this rare and original object. The results can be extended to the other ‘ arciform objects’, previously considered as Magdalenian, and constitute a first step towards their chronocultural re-contextualization. Firstly, if the attribution to the Badegoulian of the ‘ arciform object’ type were to be confirmed, it would increase a corpus constituted of elements which, for most of the currently available series, suffer from the disconnection between the production of blanks and the different typo-functional categories (eye needles, awls, chisels and projectile points). Secondly, the direct dating of the ‘ omega-like shape open ring’” rough-out from Le Petit Cloup Barrat encourages a critical re-reading of the typological assemblages yielded by Le Placard cave, according to the radiometric framework from the Badegoulian assemblages of this famous Palaeolithic site. As these assemblages served to seriate the Magdalenian periods, they need reassessment, using the AMS radiocarbon method, in addition to ‘ arciform objects’ with other morphotypes such as ‘ spiked single bevelled points’ and ‘ Lussac-Angles points’.

Atmospheric pCO2 control on speleothem stable carbon isotope compositions

The stable carbon isotope compositions of C3 plants are controlled by the carbon isotope composition of atmospheric CO2 (δ13Ca) and by the stomatal response to water stress. These relationships permit the reconstruction of ancient environments and assessment of the water use efficiency of forests. It is currently debated whether the δ13C values of C3 plants are also controlled by atmospheric pCO2. Here I show that globally-averaged speleothem δ13C values closely track atmospheric pCO2 over the past 90 kyr. After accounting for other possible effects, this coupling is best explained by a C3 plant δ13C sensitivity of −1.6±0.3‰/100 ppmV CO2 during the Quaternary. This is consistent with 20th century European forest tree ring δ13C records, providing confidence in the result and suggesting that the modest pCO2-driven increase in water use efficiency determined for those ecosystems and simulated by land surface models accurately approximates the global average response. The δ13C signal from C3 plants is transferred to speleothems relatively rapidly. Thus, the effect of atmospheric pCO2 should be subtracted from new and existing speleothem δ13C records so that residual δ13C shifts can be interpreted in light of the other factors known to control spleleothem δ13C values. Furthermore, global average speleothem δ13C shifts may be used to develop a continuous radiometric chronology for Pleistocene atmospheric pCO2 fluctuations and, by correlation, ice core climate records.

Dating results on sedimentary quartz, bones and teeth from the Middle Pleistocene archaeological site of Coudoulous I (Lot, SW France): A comparative study between TT-OSL and ESR/U-series methods

This study presents palaeodosimetric results from the Middle Pleistocene archaeological site of Coudoulous I (Lot, SW France). Nine sedimentary quartz samples (41–60 μm) have been analyzed using a multiple aliquot protocol based on the measurement of the TT-OSL signal. In addition, 7 teeth and 7 bones have been dated by combining the ESR method with U-series analyses. Both methods gave consistent age results allowing correlation of the Early Middle Paleolithic Human occupation of the site to MIS 6 and part of the Lower Paleolithic tools to MIS 7. Beyond the establishment of a radiometric chronology for the Coudoulous I sequence, this study focuses on the information extracted from the intercomparison of the methods. Our data suggest that 1) the TT-OSL signal is stable over at least the last 230 ka (considering the age range of the studied samples), 2) there are not significant problems of incomplete bleaching leading support to the applicability of the TT-OSL technique for sedimentary deposits associated with karstic contexts. This approach highlights the interest of combining luminescence and ESR/U-series methods to discuss the reliability of the dating results.

Morphometrical and geochronological constraints on the youngest eruptive activity in East-Central Europe at the Ciomadul (Csomád) lava dome complex, East Carpathians

The timing of Late Pleistocene volcanic activity of the Ciomadul (Csomád) dacitic lava dome complex, site of the youngest eruptions in the Carpathians, has been constrained by morphometric analysis and radiometric chronology. Peléan domes and asymmetric domes/coulées built up the volcano, including the central edifice that hosts the youngest twin craters of Mohoş (Mohos) peat bog and lake St. Ana (Szent Anna). A comparative digital elevation model (DEM)-based morphometric analysis of lava domes (29 worldwide examples including 5 domes from Ciomadul) shows that it is the mean slope of the upper dome flank that correlates best with age. Although the logarithmic relationship is only moderately strong (R=0.80), slope characteristics of the Ciomadul domes fit to those of 10–100ka old domes. These young ages contradict the previous K/Ar dates giving as old as 1Ma ages on a number of domes, but are supported by ongoing U–Pb and (U–Th)/He zircon dating. The latter methods constrain the whole volcanic activity to the past 250ka and the emplacement of most lava domes within the period of 150–100ka.The volcanism at Ciomadul produced alternating effusive and explosive eruptions including lava dome collapses and successive crater formations. The latest, possibly subplinian explosive event formed the well-preserved St. Ana crater. Radiocarbon dating of organic remains from a sediment core that reached 11m into the lacustrine infill of St. Ana suggests that the crater was formed prior to 26,000years BP.

Direct correlation of Chinese speleothem δ18O and South China Sea planktonic δ18O: Transferring a speleothem chronology to the benthic marine chronology

Orbital tuning of benthic δ18O is a common approach for assigning ages to ocean sediment records. Similar environmental forcing of the northern South China Sea and the southeast Asian cave regions allows for transfer of the speleothem δ18O radiometric chronology to the planktonic and benthic δ18O records from Ocean Drilling Program Site 1146, yielding a new chronology with 41 radiometrically calibrated datums, spanning the past 350 kyr. This approach also provides for an independent assessment of the accuracy of the orbitally tuned benthic δ18O chronology for the last 350 kyr. The largest differences relative to the latest chronology occur in marine isotope stages (MIS) 5.4, 5.5, 6, 7, and 9.3. Prominent suborbital‐scale structure believed to be global in nature is identified within MIS 5.4 and MIS 7.2. On the basis of the radiometrically calibrated chronology, the time constant of the ice sheet is found to be 5.4 kyr at the precession band (light δ18O lags precession minima by −55.4°) and 10.4 kyr at the obliquity band (light δ18O lags obliquity maxima by 57.4°). These values are significantly shorter than the single 17 kyr time constant originally estimated by Imbrie et al. (1984), based primarily on the timing of terminations I and II and the 15 kyr time constant used by Lisiecki and Raymo (2005).

Mid-Miocene cooling and the extinction of tundra in continental Antarctica

A major obstacle in understanding the evolution of Cenozoic climate has been the lack of well dated terrestrial evidence from high-latitude, glaciated regions. Here, we report the discovery of exceptionally well preserved fossils of lacustrine and terrestrial organisms from the McMurdo Dry Valleys sector of the Transantarctic Mountains for which we have established a precise radiometric chronology. The fossils, which include diatoms, palynomorphs, mosses, ostracodes, and insects, represent the last vestige of a tundra community that inhabited the mountains before stepped cooling that first brought a full polar climate to Antarctica. Paleoecological analyses, (40)Ar/(39)Ar analyses of associated ash fall, and climate inferences from glaciological modeling together suggest that mean summer temperatures in the region cooled by at least 8 degrees C between 14.07 +/- 0.05 Ma and 13.85 +/- 0.03 Ma. These results provide novel constraints for the timing and amplitude of middle-Miocene cooling in Antarctica and reveal the ecological legacy of this global climate transition.

Landscape Evolution and Deglaciation of the Upper Peninsula, Michigan: An Examination of Chronology and Stratigraphy in Kettle Lake Cores

We propose a radiometric chronology bracket for the last glacial advance/retreat, called the Marquette readvance, in the Upper Peninsula of Michigan (Upper Peninsula) using organic material from kettle lakes and previously published age determinations on wood buried by glaciofluvial sediments. The lakes are located both inside and outside the ice-contact margin of the Marquette readvance. Wood buried in glaciofluvial sediments from the Marquette readvance was previously dated at 10,025 ± 100 14C yr BP (Hughes and Merry 1978, Lowell et al. 1999, and Pregitzer et al. 2000). Ackerman Lake, a kettle lake located inside the ice-contact margin, yielded a basal radiocarbon date of 9,495 ± 70 14C yr BP representing the time of organic accumulation after ice retreat. These dates above and below the glacial deposit bracket the age of the Marquette readvance/retreat to 360–700 14C yr, or the midpoint of 530 14C yr. Ackerman Lake yielded multiple radiocarbon dates, including an average date of 8,811 ± 11 14C yr BP (9,736–9,913 cal yr BP) at a change in stratigraphy from red clay to gray silt. This transition along the northern Upper Peninsula is interpreted to represent ice sheet retreat into Lake Superior and the reworking of older glacial sediments by ∼8,500 14C yr BP. Organic material from the kettle lake sediments spanning multiple geomorphic locations (both inside and outside of the ice-contact margin) and previous radiocarbon dates from the entire Upper Peninsula yielded dates concentrating around 9,500 14C yr BP. We attribute this synchronous organic accumulation in the Upper Peninsula to be a result of climatic signature corresponding with the Preboreal Oscillation, so the duration of the Marquette glacial cover may have been less then implied by the Ackerman Lake basal age.

Structure of the penultimate deglaciation along the California margin and implications for Milankovitch theory

The detailed structure and timing of the penultimate deglaciation are insufficiently defined yet critical for understanding mechanisms responsible for abrupt climate change. Here we present oxygen isotope records (from planktonic and benthic foraminifera) at unprecedented resolution encompassing late marine oxygen isotope stage (MIS) 6 and Termination II (ca. 150–120 ka) from the Santa Barbara Basin, supported by additional southern California margin records, a region highly sensitive to millennial-scale climate oscillations during the last deglaciation. These records reveal millennial- and centennial-scale climate variability throughout the interval, including an interstadial immediately preceding the deglaciation, a brief warm event near the beginning of Termination II, and a Bolling-Allerod–Younger Dryas–like climate oscillation midway through the deglaciation. Recognition of these events in an oxygen isotope record from a 230Th-dated stalagmite allows the adoption of this radiometric chronology for the California margin records. This chronology supports the Milankovitch theory of deglaciation. The suborbital history of climate variability during Termination II may account for records of early deglaciation.

Orbital tuning chronology for the Vostok climate record supported by trapped gas composition

We present data on the O 2/N 2 ratios of trapped gas samples for the entire length of the Vostok climate record. As in other cores, O 2/N 2 ratios in these samples are less than the atmospheric ratio, by a small and variable amount, because O 2 is selectively excluded during the gas trapping process, and because O 2 is also preferentially lost in poorly preserved core samples. Samples younger than 150 ka have large and variable O 2 depletions. Samples older than 200 ka have O 2/N 2 ratios that replicate well and vary smoothly with depth. We plot O 2/N 2 ratios of well replicated samples older than 160 ka, using a chronology derived by matching the δ 18O of paleoatmospheric O 2 (δ 18O atm) to northern hemisphere June insolation. On this timescale, O 2/N 2 varies coherently with local (78°S) summertime insolation. Based on time series analysis of the O 2/N 2 record and the dynamics of snow metamorphism at the surface, we conclude that summertime insolation influences physical properties of ice grains that control the degree of O 2 exclusion during bubble closeoff. O 2/N 2 in Vostok is thus arguably a property that records local summertime insolation and can be used to test independent chronologies for the core. We show that the δ 18O atm chronology, supported by the coincidence of O 2/N 2 ratios with insolation, is also compatible with recent radiometric dating of corals from high sea stands. We further successfully test the δ 18O atm tuning chronology by showing that it predicts a chronology for the GISP2 core which is essentially indistinguishable from the standard GISP2 chronology and, therefore, in excellent agreement with the radiometric chronology of Hulu Cave, China. An accurate chronology for the Vostok ice core is now in place.

Evolutionary significance of cranial variation in Asian Homo erectus.

Homo erectus inhabited a wide geographic area of Asia, ranging from 40 degrees north latitude in China to 8 degrees south latitude in island Southeast Asia. Yet variation within Asian H. erectus and its relation to ecological and temporal parameters have been little studied. I synthesize the revised radiometric chronologies for hominid sites in Asia and their relation to new oxygen isotope curves (proxies for climatic fluctuations and landbridge connections). These data suggest substantial opportunities in the later Pleistocene for both regional isolation and gene flow between hominids in mainland and Southeast Asia. They also suggest that the most northerly located Chinese sites (Zhoukoudian and Nanjing) may have been occupied during sequential, interglacial periods. Probably reflecting these periods of isolation, nonmetric features and principal components analysis (PCA) of calvarial shape suggest regional differentiation between northern Asian and Southeast Asian H. erectus. The most recent Southeast Asian fossils (e.g., Ngandong) conform to the Southeast Asian pattern. Except perhaps in brain size, there is no evidence that the temporally intermediate Chinese fossils are intermediate in morphology between older and younger Indonesian fossils. In fact, northern Chinese calvaria are easier to exclude from the larger Asian H. erectus hypodigm than are the Ngandong fossils. The Chinese specimens differ from the others based on their narrower occipitals and frontals for their cranial size. The Chinese sample from Zhoukoudian alone is thus not a good proxy for the morphology and variation seen within Asian H. erectus. Both the Chinese and late Indonesian samples exhibit less variation than does the early Indonesian sample; this along with their shared morphological bauplan suggests a common origin and no more than subspecific differentiation. This shared morphology, despite regional differences, was likely maintained by the increasing intensity of multiple glaciations (and longer-lasting land bridge connections) between mainland and island Southeast Asia during the last million years.

High-resolution analyses of recent sediments from a Norwegian mountain lake and comparison with instrumental records of climate

The purpose of the palaeolimnological research project carried out at Ovre Neadalsvatn was to apply a number of physical and biological proxy-climate analyses to recent sediments and to compare the results of these analyses with instrumental records of climate. Using a radiometric chronology to match the sediment core with the calendar ages of the reconstructed instrumental record, and by time-averaging the instrumental record, the statistical significance of the relationships between each of the sediment-climate proxies and the reconstructed instrumental-climate measurements were evaluated. Acid deposition at Ovre Neadalsvatn has been low and its impact limited. Whilst there has been an overall rise in mean annual temperature of about 1 °C since 1900, the physical and biological sediment records studied appear to be insensitive to climate warming of this magnitude. On the one hand, this may be a result of the loss in temporal resolution caused by time-averaging the instrumental data; on the other hand, the lake may be insensitive to the impact of this climate change.