Late Glacial Stage Research Articles

TRANSFORMATION OF PLANT COMMUNITIES AT THE TURN OF THE PLEISTOCENE AND HOLOCENE IN THE ROSTOV LOWLAND (YAROSLAVL REGION)<a href="#FN1"><sup>1</sup></a>

The article presents the results of a multiproxy study of a sedimentary sequence located on the lacustrine-alluvial plain west of Lake Nero (Yaroslavl region). The investigated 2 m-long core made it possible to reconstruct environmental changes since the Allerød to the Late Holocene. Previously poorly studied Preboreal deposits in this area have a significant thickness in the core (0.4 m). The obtained materials help fill the gap in understanding of the vegetation history in the Rostov lowland at the turn of the Late Glacial and Holocene and during the Early Holocene. The study is based on several paleogeographic methods: spore-pollen analysis, botanical composition analysis of peat, diatom analysis, loss-on-ignition, and radiocarbon dating. It was found that after 14.3 cal. ka BP sparse spruce-birch forests were widespread, open spaces were occupied by herbaceous communities. Since 13.7 cal. ka BP, as a result of a significant cooling, the open areas expanded, sparse birch forests dominated in combination with steppe and tundra associations. About 12.1 cal. ka BP a lowland reed wetland began to form at the site. It transformed into a reed-sedge wetland after 10.9 cal. ka BP. During the interval of 12.1–11.5 cal. ka BP, the landscapes of the periglacial forest-steppe were gradually replaced by pine-birch forests. The climate was colder than today, but with the tendency to warming compared to the Late Glacial stage. Short-term cooling 11.5–11.2 cal. ka BP led to a new expansion of open herbaceous communities, but the spread of forests continued after 11.2 cal. ka BP. Starting from 9.8 cal. ka BP, the role of broadleaf species increased in the woods; mixed pine-birch forests with oak, elm, and linden dominated in the surrounding area. In the interval 7.9–5.2 cal. ka BP, climate conditions were warmer than modern ones. This led to the spread of spruce-pine forests with birch and thermophilous deciduous trees. After 5.2 cal. ka BP the vegetation cover was dominated by spruce forests with pine, birch, and broadleaf species.

Late Glacial palaeoenvironmental changes in the southern part of the Holy Cross Mountains based on the “Białe Ługi” peatland record

This paper presents the Late Glacial stage of the development of the Białe Ługi peatland in the southern Holy Cross Mountains, based on a comprehensive palaeoenvironmental data. A complex analysis of palynology, Cladocera, sed imentology, geochemistry and 14C dating were used. Organic deposition was initiated during the Oldest Dryas. The sedimentary record of the aquatic and terrestrial ecosystems reflects considerable difference between cooler (Oldest, Older and Younger Dryas) and warmer phases (Břlling and Allerřd). Periods of intensified interaction between aeolian processes and peatland are related to stages of disappearing vegetation and changes in aquatic invertebrate communities. We therefore suggest that peatlands were created as a result of local lithological-structural, tectonic, hydrogeological and morphological conditions, and the peatland development rate was largely influenced by changing climatic conditions, which determined local vegetation development, intensity of denudation processes and water level changes. The results validate significance of selection and use of several methods, as well as value of biogenic deposits from the Białe Ługi peatland as archives of past climate change in the Małopolska Upland. Relatively stable water conditions and uninter rupted biogenic sedimentation in the Late Glacial that were provided by the geological structure and relief suggest the studied peatland is a leading one in the region.

Last Glacial Maximum and Lateglacial in the Polish High Tatra Mountains - Revised deglaciation chronology based on the 10Be exposure age dating

Deglaciation chronology of the Polish High Tatra Mountains has been reconstructed based on 10Be exposure age dating. Fifty-seven rock samples were collected from boulders located on the terminal and lateral moraines that limit the horizontal extent of the LGM and the Lateglacial glaciers in the Biała Woda and Sucha Woda catchments. The uncertainty-weighted mean age of 21.5 ± 2.5 ka obtained for the maximum terminal moraine in the Sucha Woda Valley indicates that the oldest preserved moraines were formed during the global LGM. The age population ranges between 15.1 ± 1.0 and 28.3 ± 2.0 ka, and suggests that glaciers reached their maximum position (LGM I) as early as 28–25 ka and the final stabilization of the form occurred much later possibly after melting of buried dead ice. The younger glacial oscillation (LGM II) occurred no later than 20.5 ka and is represented by well-preserved termino-lateral moraine systems in the Pańszczyca Valley. The first Lateglacial stage (LG1) in the study area is documented in the Rybi Potok Valley at the RP1 moraine (1300 m a.s.l.), which was stable at around 16.6 ± 0.3 ka. The younger LG2 stage has no defined absolute age, however, it is constrained between 16.5 and 15.5 ka by the timing of the LG3 stage. This cold event is represented by well-formed moraines in the Roztoka/Pięć Stawów Polskich, Rybi Potok and Pańszczyca valleys of which exposure age indicates their deposition between 15.0 ± 0.5 and 15.6 ± 0.1 ka. The LG1, LG2 and LG3 stages likely occurred during the Oldest Dryas cold stage (Greenland Stadial 2.1a) related to the North Atlantic cooling Heinrich Event 1. The youngest glacial oscillation is evidenced by moraines in the Pusta and Pańszczyca valleys. These moraines are composed of very large granitic blocks of which exposure ages often exhibit isotope inheritance. This is reflected by the youngest P3 moraine in the Pańszczyca Valley with a mean age of deposition close to the LGM. The R4 moraine system in the Pusta Valley, however, indicates two oscillations phases that occurred at around 13 ka and correlates well with the timing of RP5 moraine formation in the Za Mnichem Valley. The LG4 stage is related to the climate cooling during the Younger Dryas (Greenland Stadial 1).LGM ELAs reconstructed for the Biała Woda and Sucha Woda/Pańszczyca glaciers were located at 1460–1480 m a.s.l. During the Oldest Dryas stages, the ELA in the High Tatras rose from 1600 to 1650 m a.s.l. in the Rybi Potok Valley and from 1700 to 1800 m a.s.l. in the Roztoka/Pięć Stawów Polskich Valley. The Younger Dryas ELA, depending on glacier's exposition, was located between 1950 and 2000 m a.s.l. Climate modelling results show that the LGM glaciers (maximum advance) could have advanced in the High Tatras when the mean annual temperature was lower than today by 11–12 °C and precipitation was reduced by 40–60%. During the Lateglacial stages the temperature decrease in the study area changed from 10 °C during the Oldest Dryas to 6 °C during the Younger Dryas and precipitation lowering decreased from −50% to −30% or even −10%, respectively compare to modern conditions.

Across the Arid Diagonal: deglaciation of the western Andean Cordillera in southwest Bolivia and northern Chile

Here we review published cosmogenic records of glaciation and deglaciation from the western cordillera of the arid subtropical Andes of northern Chile and southwest Bolivia. Specifically, we examine seven published studies describing exposure ages from moraines and glaciated bedrock spanning the glaciological Arid Diagonal, the region of the dry Andes where there is no clear evidence for glaciation over at least the last global glaciation. We also present new cosmogenic 36Cl exposure ages from two previously undated sets of moraines in the deglaciated region near 22ºS. Taken together, these records indicate that the most extensive regional glaciation occurred ca. 35-45 ka, followed by slow, punctuated retreat through the global last glacial maximum, and rapid retreat after ~15-17 ka. In the vicinity of the large Altiplanic lakes that existed during the late glacial stage, the 15-17 ka moraines overrode the earlier moraines, whereas elsewhere regionally, on both sides of the Arid Diagonal, late glacial wet periods are represented only by less-prominent moraines in more retracted positions.

ROCK GLACIERS IN THE SOUTHERN CHUKCHI PENINSULA

About 550 rock glaciers of different types were identified on the basis of remote sensing and field studies in the Southern Part of the Providenskiy mountain massif (the Chukchi Plateau). The measured occurrence frequency of rock glaciers of about 8 units/km2 is the highest in the North-East Asia. All known morphodynamic types of rock glaciers were found: tongue-shaped cirque-associated, lobate-shaped slope-associated and complex ones. Rock glaciers were found over the entire elevation range starting from the sea level. The slope-associated multi-lobate rock glaciers of abnormal sizes, as well as the ice-ground dams are the most widespread ones and they concentrate in linear zones along the sides of neotectonic grabens and fracture zones. They were distinguished as a particular type of fault-associated rock glaciers. A specific feature of rock glaciers of the Providence massif is the thawed bed that causes water infiltration under the front generations, which is similar to “warm”ˮ glaciers and rock glaciers of Europe and Central Asia, while in the Mountains of Northeast Asia within the continuous permafrost zone rock glaciers have frozen bed, and their temperatures are significantly below zero. The age of active rock glaciers of Povidenskiy massif is not more than 2–2.5 kyr. We attribute their formation to the specific features of the Last Glaciation decay under the conditions of Marine Arctic climate. The increasing role of cryogenic mass movement during the Late Glacial Stage promoted the burial of ice and frozen moraine blocks in the glacial cirques and at valley sides and predetermined their subsequent transformation into rock glaciers.

Late Glacial glacier-climate modeling in two valleys on the eastern slope of Samdainkangsang Peak, Nyaiqentanggulha Mountains

Well-preserved Late Glacial moraines in the Barenduo and Yuqiongqu valleys on the eastern slope of the Samdainkangsang Peak present an opportunity to reconstruct glacier extents and examine the character of the climate during the Late Glacial stage in the Nyaiqentanggulha Mountains. This study employs a coupled mass-balance and ice-flow model to reconstruct the glacier extents in the two valleys and assess the magnitudes of temperature and precipitation change during the Late Glacial period. Model results indicate that during the Late Glacial, the Barenduo valley contained an ice volume of 1.67×108 m3, with the equilibrium-line altitude (ELA) being ~5500 m asl; and the Yuqiongqu valley had an ice volume of 5.56×108 m3, with the ELA being ~5470 m asl. A climate scenario, temperature depression of 2.6–2.8°C and 60–70%, percent of modern (1981–2010) precipitation, can sustain both of the Late Glacial glacier extents in the two valleys. A 50% increase or decrease from modern precipitation would have been coupled with the respective Late Glacial temperature depressions of 1.6 and 3.0°C in the Barenduo valley, and 2.1 and 2.8°C in the Yuqiongqu valley.

From valley to marginal glaciation in alpine-type relief: Lateglacial glacier advances in the Pięć Stawów Polskich/Roztoka Valley, High Tatra Mountains, Poland

The Pięć Stawów Polskich-Roztoka Valley in the High Tatras (Western Carpathians) features typical alpine-type relief with a deeply incised glacial trough and large, compound trough head cirque. The prominent hypsographic maximum in the valley (1680–2000m) along with a broad cirque bottom had provided a vast space for recording glacial and periglacial landforms, specifically the most recent Lateglacial advances. The valley has been intensively studied before in the context of glacial chronology. In this paper, we re-establish the post-Last Glacial Maximum (LGM) glacial chronology of the valley via detailed geomorphologic mapping, equilibrium line altitude (ELA) reconstruction, and Schmidt hammer (SH) dating, along with a critical review of previously published cosmogenic exposure age data (36Cl) and lacustrine sediment chronology.Our results indicate that the first four of the five distinguished Lateglacial stages (Roztoka I–III, Pusta I) occurred before the Bølling/Allerød (B/A) interstadial; thus, virtually the entire valley became deglaciated in course of the Oldest Dryas cold phase. A distinct reorganization of deglacial patterns from valley-type to marginal-type occurred before B/A warming when the ELA increased above the valley hypsographic maximum concentrated at the cirque bottom elevation. It shows that noticeable deglaciation step can be caused due to topographic reason with a minimal climate forcing. This points also to an important role of glaciated valley hypsography in regulating the distribution of moraines which is rarely taken into account in paleoglaciological reconstructions. We infer that glaciers vanished in the Tatra Mountains during the B/A interstadial. Later, a renewed advance during the Younger Dryas (Pusta II) formed a nearly continuous, festoon shaped pattern of moraines and rock glaciers in close distance to cirque backwalls. Furthermore, we discus some paleoenvironmental significance of the geomorphological record in the valley, as well, the applicability of SH dating in constructing glacial chronology.

Environmental and climatic changes during the Pleistocene–Holocene in the Bor Plain, Central Anatolia, Turkey

The Bor Plain lies in a round-shaped flat basin in the southern part of the Central Anatolia. It is located at the southeastern end of the Tuzgölü Fault Zone—which is the NW trending, active normal fault zone and extends between the north of the Tuzgölü (Lake Tuz) at NW and at Kemerhisar (Niğde) SE. According to geomorphologic and geologic studies, this plain was occupied by lake during the Pleistocene. The first high lake level (terrace) and the latest high lake level (terrace) were determined at 1170–1150m and 1110–1100m, respectively. Pleistocene and Holocene alluvial and lacustrine deposits are composed of claystone, sandstone, mudstone, limestone and paleosol units. These units contain mostly calcite and clay minerals (palygorskite, smectites, illite and chlorite), and lesser amounts of quartz, phillipsite, cristobalite, feldspar, plagioclase, goethite and, muscovite. The results of this study are compared with the results of sedimentologic and dating obtained from Konya–Ereğli Plain. According to this comparison, 1—the latest high lake terraces were dated 23,000 to 17,000yrBP. The high lake level was changed, 2—sandy level with carbonate determined in stratigraphy indicates that a dry phase dominated after 17,000yrBP, and 3—black and brown muds indicate that the shallow freshwater lacustrine phases and sandy levels were formed between 12,500 and 1100yrBP during late glacial stage. Paleosols, muddy levels and shallow lake deposits were formed in the environment of the Holocene during 6000–5000yrBP. Carbonate-rich sandstone and mudstone deposits show that this period was interrupted by the second drought in the latest stage. Temperatures have increased due to hot climate conditions and salinization has begun and been still ongoing.

Thermomechanical stress–strain numerical modelling of deglaciation since the Last Glacial Maximum in the Adamello Group (Rhaetian Alps, Italy)

Deglaciated areas in the valleys of the Italian Alps have recently exhibited a high potential for geomorphologic hazards from diffuse deep-seated gravitational deformations (DSGSDs), caused by rock-mass creep processes that can evolve into rock falls and rock avalanches. A multidisciplinary approach that integrated geomorphologic surveys and stress–strain numerical simulations was used to investigate the effects of the stress release that was induced by the Last Glacial Maximum (LGM) in the Adamè Valley (Italian Alps). No evidence of DSGSDs has been found in this area; however, data are available to develop a well-constrained evolutionary model of the valley deglaciation. The extent and thickness of the southern extension of the Adamello glacier (the widest glacier in Italy) during its primary growth phases, including those of the LGM, three Late Glacial stages and the Little Ice Age (LIA) were reconstructed using glacial geological surveys and were reproduced using a finite-difference stress–strain sequential model spanning from the LGM to the present. A thermomechanical numerical configuration was developed based on geomechanical field measurements that were collected from rock outcrops and data from laboratory tests, specifically performed on intact rock samples. The numerical simulations demonstrate that thermomechanical viscous behaviour cannot be neglected because the resulting strains on the slopes are significantly higher than those resulting from conventional elastoplastic behaviour. The last major thermal effect in the rock masses reproduced using the model occurred from 11.5ka until the LIA; the resulting displacement rates are as much as several tens of mm/ka, which are consistent with the absence of DSGSDs in the Adamè Valley, as these rates are significantly lower than those previously obtained from DSGSDs and other large landslides in the Alps. Based on thermomechanical numerical solutions, these rates should persist for the next 1000years assuming that no variations in current climatic conditions occur.

The first reconstruction of the late glacial plant communities on the Yamal Peninsula based on plant macrofossils.

Strong climatic fluctuations during the Late Glacial stages of the Late Pleistocene, which resulted intransformation of vegetation in northern Eurasia, havebeen characterized in detail on the basis of numerouspaleobotanic data [1–3]. At this time, there were twointerstadial periods of warming—Bolling (12400–12000 radiocarbon years ago) and Allerod (11800–10900 radiocarbon years ago)—when the most pronounced climatic changes occurred, accompanied byexpansion of woody vegetation to the subarctic areas ofEurasia [4–6]. The time interval from 12400 to10900 years ago was often regarded as an interstadialBolling–Allerod complex interrupted by a minorshortterm cooling of the Older Dryas (12000–11800 radiocarbon years ago), which preceded a significant and strong cooling of the Younger Dryas(10900–10200 radiocarbon years ago) [2, 7, 8].Despite the extensive paleobotanic material thatcharacterizes the Late Glacial stages of the vegetationgrowth in the subarctic areas of Russian Arctic [4, 5, 9],only separate reports [10, 11] concerning the reconstructions of the Late Glacial paleovegetation in theareas north of Western Siberia are available. In thispaper, we describe the first dated complexes of plantmacrofossils from the alluvial deposits of the YuribeyRiver valley. They served as the basis for reconstructionof the plant community of the Yamal Peninsula duringinterstadial Bolling–Allerod warming.The Ngoyun crosssection lies on the west bank ofan unnamed lake 0.5 km northeast of Lake Ngoyun,on the left bank of the Yuribey River, upstream themeridional flow on the Yamal Peninsula (68°32′ N,72°06′ E) [12]. According to geobotanical zoning, theYuribey River valley lies currently in a subzone ofsouthern shrub tundra [13]. This territory is mostlyrepresented by ledum–small shrub–lichen–moss(moss–lichen) grumous, spotted grumous, and sometimes polygonal tundras. On the convex relief, there isthe shrubspotted grumous and polygonal tundras.The following plants form the basis of the herb–shrublayer of tundra:

ESR and 230Th/234U dating of speleothems from Aladağlar Mountain Range (AMR) in Turkey

Electron spin resonance (ESR) and 230Th/234U ages of speleothem samples collected from karstic caves located around 3000m elevation in the Aladağlar Mountain Range (AMR), south-central Turkey, were determined in order to provide new insight and information regarding late Pleistocene climate. ESR ages were validated with the 230Th/234U ages of test samples. The ESR ages of 21 different layers of six speleothem samples were found to range mostly between about 59 and 4ka, which cover the Marine Oxygen Isotope Stages (MIS) MIS 3 to MIS 1. Among all, only six layers appear to have deposited during MIS 8 and 5. Most of the samples dated were deposited during the late glacial stage (MIS 2). It appears that a cooler climate with a perennial and steady recharge was more conducive to speleothem development rather than a warmer climate with seasonal recharge in the AMR during the late Quaternary. This argument supports previous findings that suggest a two -fold increase in last glacial maximum mean precipitation in Turkey with respect to the present value.

Application of Schmidt hammer relative age dating to Late Pleistocene moraines and rock glaciers in the Western Tatra Mountains, Slovakia

In order to evaluate the potential of the Schmidt hammer for relative age dating of Late Pleistocene moraines and rock glaciers, rebound (R) values were collected at 38 sites in two formerly glaciated valleys in the Western Tatras in northern Slovakia. A large statistical population of measurements obtained from moraine and rock glacier surfaces was used to analyze the variability of mean R-values in the same lithology and overall southern valley exposition. Four separate sets of glacial/periglacial morphosystems are present at different positions in the Western Tatras starting from valley outlets to the highest cirques, which represent successive phases of deglaciation. R-value means and 95% confidence intervals for selected Last Glacial Maximum (LGM), and Late Glacial (LG-1, LG-2 and LG-3) stages (respectively, 40.1 ± 1.1, 46 ± 0.5, 53.5 ± 1.0 and 60.5 ± 0.3) are significantly statistically different and values for each age category are comparable for the two analyzed valleys. The results of weathering indexes used in conjunction with geomorphological relationships were taken together to reconstruct the pattern of deglaciation on southern Tatra slopes. It is stated that the Schmidt hammer technique may be successfully used as a relative age dating tool for Late Pleistocene glacial and periglacial deposits, and with this method, it is possible to differentiate between Late Glacial moraines and rock glacier systems of different age.

Recharge sources and hydrogeochemical evolution of groundwater in the coal-mining district of Jiaozuo, China

Investigations in the Jiaozuo coal-mining district (China) aim to link water-inrush aquifers with the sources of groundwater recharge. Concentrations of TDS, HCO3–, Cl– and Na+ in the groundwater samples gradually decrease with increasing depth; in contrast, the factor 1 value of the Q-mode analysis gradually increases, which indicates that the deep groundwater may upflow, recharging the aquifers near the faulted zone. Some groundwater samples (above the local meteoric water line and ‘evaporation line 1’) may originate from recharge by infiltrating local rainfall. Spring and river samples are symmetrically distributed on the regression line of the Ordovician and Carboniferous limestone aquifer groundwater (δ2H = 3.76 × δ18O – 31.77) and may, therefore, originate from groundwater recharge in the northern Taihang mountains. This mechanism is supported by the observation that groundwater levels change with rainfall. According to radiocarbon residence-time estimates, two groundwater sample sites may have been recharged during the late glacial stage.

Abrupt Younger Dryas cooling in the northern tropics recorded in lake sediments from the Venezuelan Andes

A radiocarbon dated sediment record from Laguna de Los Anteojos, a cirque lake in the Mérida Andes of Venezuela, indicates that warmer and wetter atmospheric conditions occurred in the northern tropics at the onset of the Bølling (∼ 14,600 cal yr BP), and abruptly colder and drier conditions around the time of the Younger Dryas (YD). Geochemical and clastic sediment analyses from Los Anteojos show that glaciers advanced at ∼ 12,850 cal yr BP, reached their YD maximum extent at ∼ 12,650 cal yr BP, and then retreated until complete deglaciation of the watershed at ∼ 11,750 cal yr BP. The onset of warmer conditions that ended the coldest phase of the YD occurred several hundred years earlier at Los Anteojos than in the high latitudes of the Northern Hemisphere. During the peak YD glacial advance, glacier equilibrium-line altitudes in the region were ∼ 360 to 480 m lower, and temperature was ∼ 2.2 to 2.9 °C colder than modern. Independent palynological evidence from the Los Anteojos sediment core indicates that the northern Andes were more arid and at least 2.3 °C colder during the YD. The direction and timing of glacial fluctuations in Venezuela are consistent with observations of marine sediment records from the Cariaco Basin that suggest abrupt cooling occurred at ∼ 12,850 cal yr BP, followed by a shift to higher temperature after ∼ 12,300 cal yr BP. The timing and pattern of climatic changes in northern South America are also consistent with paleoclimate records from the southern Tropical Andes that suggest a southward shift in the position of the Intertropical Convergence Zone occurred at the start of the cooling event, followed by a return to wetter conditions in northern South America during the late stages of the YD. The early warming of the tropical atmosphere and invigoration of the hydrologic cycle likely contributed to the shift to increased temperature in the higher latitudes of the Northern Hemisphere at the end of the late Glacial stage.

Present and Late Pleistocene equilibrium line altitudes in Changbai Mountains, Northeast China

According to the glacial landforms and deposits with the optically stimulated luminescence (OSL) dating results, two glacial stages of the last glacial cycle (LGC) and Late Glacial were identified. The Late Glacial stage (Meteorological Station glacier advance) took place about 11 ka (11.3±1.2 ka), and the last glacial maximum (LGM), named Black Wind Mouth glacier advance, occurred at 20 ka (20.0±2.1 ka). Based on the Ohmura’s formula in which there is a relationship between summer (JJA) atmospheric temperature (T) and the annual precipitation (P) at ELA, the present theoretical equilibrium line altitude (ELAt) in Changbai Mountains was 3380±100 m. Six methods of accumulation-area ratio (AAR), maximum elevation of lateral moraines (MELM), toe-to headwall altitude ratios (THAR), the terminal to summit altitudinal (TSAM), the altitude of cirque floor (CF), and the terminal to average elevation of the catchment area (Hofer) were used for calculation of the former ELAs in different stages. These methods provided the ELA for a range of 2250–2383 m with an average value of 2320±20 m during the LGM, which is 200 m higher than the value of previous investigation. The snowlines during the Late Glacial are 2490 m on northern slope, and 2440 m on western slope. The results show that the snowline on northern slope is 50 m higher than that on western slope during the Late Glacial, and the average snowline is 2465m. The ΔELA values were more than 1000 m during the LGM, and about 920 m lower than now during the Late Glacial stage respectively. Compared with Taiwanese and Japanese mountains in East Asia during the LGM, the effect of the uplift on ELA in Changbai Mountains during the glaciations (i.e. 20 m uplift in the LGM and 11 m in the Late Glacial) is not obvious.

A high resolution record of vegetation and environmental variation through the last ∼ 25,000 years in the western part of the Chinese Loess Plateau

We present a high-resolution reconstruction of vegetation and environmental changes from a 40-m thick section in the western part of the Chinese Loess Plateau in attempt to reveal the details of the MIS 2 and MIS 1 climate variations. Our data show that a desert steppe occupied the landscape between ∼ 24,500 and ∼ 13,600 14C yr BP. Two episodes of further vegetation deteriorations occurred between ∼ 20,000 and ∼ 17,100 14C yr BP and between ∼ 15,100 and ∼ 13,600 14C yr BP, corresponding to the Heinrich events 2 and 1. The late glacial stage between ∼ 13,600 and ∼ 9880 14C yr BP included four sub-stages that correspond chronologically and climatologically to the European deglacial sub-stages. The first sub-stage (∼ 13,600 to ∼ 12,400 14C yr BP) corresponds to the Bølling warm period; the second sub-stage (∼ 12,400 to ∼ 11,500 14C yr BP) to the Older Dryas cold period; the third sub-stage (∼ 11,500 to ∼ 10,700 14C yr BP) to the Allerød warm period; and the fourth Sub-stage (∼ 10,700 to ∼ 9880 14C yr BP) to the Younger Dryas cold period. The early–mid Holocene (∼ 9880 to ∼ 4370 14C yr BP) was a period when a forest steppe dominated the landscape under a warm and wet climate. During this period, eight cool and dry spells occurred at ∼ 9720 14C yr BP (E1), ∼ 9380 14C yr BP (E2), ∼ 8870 14C yr BP (E3), ∼ 8660 14C yr BP (E4), ∼ 8440 14C yr BP (E5), ∼ 8240 to ∼ 8060 14C yr BP (E6), ∼ 7120 to ∼ 6550 14C yr BP (E7), and ∼ 5640 to ∼ 5120 14C yr BP (E8). After a major deterioration in vegetation between ∼ 4370 to ∼ 3270 14C yr BP, the study area experienced improved moisture conditions between ∼ 3270 to ∼ 1450 14C yr BP, followed by a persistent deterioration of vegetation under a drying climate during the past ∼ 1500 years.

Vegetation and Climate Changes since Late Glacial Stage in Harukoyachi Mire, Iwate Prefecture, Northeast Japan

Vegetation and Climate Changes since Late Glacial Stage in Harukoyachi Mire, Iwate Prefecture, Northeast Japan

Glacial and Lateglacial vegetation in northeastern Spain: New data and a review

Though usually under-represented in palaeobiogeographical models, northeastern Spain is one of the regions of southern Europe with the greatest biodiversity. Strong climatic and geographic gradients and topographic contrasts have contributed to the marked physiographic heterogeneity of the region. Pollen sites from the Ebro River Basin (northeastern Spain) have been insufficiently studied, perhaps because of the scarcity of suitable sites for conventional pollen analyses (i.e. lakes, peatbogs) and the characteristic mosaic vegetation patterns. Glacial and Lateglacial pollen records from a variety of archives located along a N–S transect: Glacial lakes, periglacial screes, peatbogs, hyena coprolites and archaeological sites were analyzed. The reconstruction of full and Lateglacial landscapes in the Ebro River valley provides new insights into the vegetational history of the region: (i) the abundance of steppe formations with Artemisia, Poaceae, Chenopodiaceae, Ephedra, Asteraceae during the most intensive cold-arid episodes in both the non-glaciated mountains and the lowlands, (ii) the continuous occurrence of woody taxa even at high areas, (iii) the expansion of these woody taxa during Lateglacial climatic ameliorations, (iv) the survival of mesothermophytes in small refuge areas during full-glacial stages. There was great vegetation diversity in the northeastern Iberian landscapes during the Last Glacial and Lateglacial stages, suggesting patches of vegetation with steppic areas, Mediterranean shrubs, coniferous forest and refuges of mesothermophilous taxa.

An evaluation of climate, crustal movement and base level controls on the Middle-Late Pleistocene development of the River Severn, U.K.

AbstractThe Pleistocene development of the lower Severn valley is recorded in the fluvial sediments of the Mathon and Severn Valley Formations and their relationship to the glacigenic Wolston (Oxygen Isotope Stage 12), Ridgacre (OIS 6) and Stockport (OIS 2) Formations. The most complete stratigraphical record is that of the Severn Valley Formation, which post-dates the Anglian Wolston Formation and comprises a flight of river terraces, the highest of which is c.50 m above the present river. The terrace staircase indicates that the Severn has progressively incised its valley during the post-Anglian period. The terrace sediments are predominantly composed of fluvially deposited sands and gravels, largely the result of deposition in high-energy rivers under cold-climate conditions. Occasionally towards the base of these terrace deposits low-energy fluvial facies are preserved which contain faunal remains and yield geochronology which support their correlation with interglacial conditions. This simple stratigraphy supports a climate-driven model for the timing of terrace aggradation and incision, with the incision mode at its most effective during the cold-warm transitions and the aggradational mode at its most effective during warm-cold climate transitions. The chronology of terrace aggradation in the lower Severn seems to correspond with the Milankovitch lOOka climate cycles. The timing of incision events suggests that base level (eustatic sea-level) changes do not play a significant role i.e. incision occurs as sea-level is rising.Although climate change is significant in governing the timing of incision, the long-term incision of the River Severn appears to be driven by crustal uplift. A long-term incision rate of 0.15 m ka1, calculated using the base of the terrace deposits, is believed to closely equate with the long-term uplift rate. Superimposed on this long-term uplift are periods of complex terrace sequence development resulting from rapid incision during periods of glacio-isostatic rebound, with large incision events reflecting the rebound adjustment to late glacial stage isostatic depression. However, in no case in the Severn valley has glacial encroachment led to enhanced incision, suggesting that there has been no additional uplift resulting from isostatic compensation for glacial erosion.

日本アルプスにおける氷河の高度分布特性と類型化

Glaciations during the Last Glacial in the Japanese Alps can be classified “azonal glaciation” and “zonal glaciation”. The ELAg (geomorphological equilibrium line altitude) of each former type of glacier is determined by Hs (height of summit), and is depressed by microclimatological phenomena such as drifted snow. The vertical/horizontal distribution of this type of glacier is azonal and sporadic. On the other hand, the ELAg of the latter type of glacier remains constant with Hs, and reflects the regional air temperature. In the case, the mountain ridge is higher than the regional equilibrium-line altitude, the vertical/horizontal distribution of glaciers belonging to this type becomes zonal and continuous. Modern examples of these two types of glaciation can be found in Kamchatka Peninsula, the Altai Mountains, and the Caucasus Mountains. These facts suggest that this classification is applicable to spatial and temporal variations of glaciation. Most of the Last Glacial glaciers in the Japanese Alps are classified into the “azonal glaciation” type. The glaciers belonging to the “zonal glaciation” type are located in the Northern Japanese Alps that have high altitudes. Some of the “zonal glaciation type” that existed during the Last Glacial Maximum stage were changed to “azonal glaciation” type during the Late Glacial stage. From this point of view, the Last Glacial glaciers in the Japanese Alps existed as a spatio-temporal transition between these two types. Paying attention to the “azonal glaciation” which is controlled by local conditions, is important for reconstructing the palaeoclimate based on the glacial landforms and their ELAs.