Modeled tephra ages from lake sediments,base of Redoubt Volcano,Alaska

A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS ¹⁴C ages, along with the ¹³⁷Cs and ²¹⁰Pb activities of recent sediment, we evaluated different models to determine the age–depth relation of the core, and to determine the age of each tephra deposit. The selected age model is based on a mixed-effect regression that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages ±105 yr (95% confidence intervals). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7/500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500–3500, 4500–5000, and 7000–7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000–2000 yr) of increased tephra fall separated by shorter periods (500–1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of one every 130 yr.     

OSL chronology for lacustrine sediments recording high stands of Gahai Lake in Qaidam Basin,northeastern Qinghai–Tibetan Plateau

The Qaidam Basin in the northeastern Qinghai–Tibetan Plateau (QTP) is one of the largest hyper-arid intermontane basins in the northern hemisphere, and has abundant records for the study on palaeo-lake level fluctuations and palaeoclimatic changes. Significant efforts have been invested to define the timing of shoreline deposits using radiocarbon dating. However, due to the dating limit, the absence of organic materials and carbon reservoir effects for radiocarbon dating in arid areas, it is difficult to establish a reliable chronology for shoreline deposits. Therefore, controversy exists regarding the chronology for the high lake level in the Qaidam Basin, as well in the QTP. Some proposed that high lake levels occurred during late Marine Isotope Stage (MIS) 3, while others recently argued that the highest lake level in the QTP and adjacent regions existed in MIS 5. In Gahai Lake (now a salt lake), we investigated a section comprising lacustrine and shoreline deposits, which was about 25 m above the present lake level. Seven samples were collected for quartz optically stimulated luminescence (OSL) dating. A sample collected from a fine sand layer (the bottom of the section, and 12 m above the present lake level), which was assumed to have been deposited underwater, gave an OSL age of 82 ± 8 ka. It suggested that the lake level was at least 12 m higher than present in late MIS 5. The high lake level could maintain till about 73 ± 6 ka, and then decreased. This lake level decrease resulted in a gravel layer deposit between 73 ± 6 and 63 ± 6 ka (roughly during MIS 4). The lake level rose again (about 24 m above the present lake level) between 63 ± 6 and 55 ± 5 ka (roughly in early MIS 3). No lacustrine or shoreline deposits higher than the top of the current section were found around Gahai Lake. Thus, higher than present lake levels in Gahai Lake occurred in both late MIS 5 and early MIS 3.     

Quartz OSL dating of sand dunes of Late Pleistocene in the Mu Us Desert in northern China

The Mu Us Desert, located in the northwestern fringe of the East Asian monsoon region, is sensitive to climate variability. The desert is characterized by mobile, semi-fixed and fixed sand dunes. Alternating units of dune sands and sandy palaeosols in the Mu Us Desert imply multiple episodes of dune building and stabilization, in response to the ebb and flow of the East Asian monsoon. Desert evolution and climatic change of high-resolution in the Mu Us Desert are still poorly understood due to limited numerical dating results. In the present study, 19 samples collected from five sand dune sections along a northwest–southeast transect in the Mu Us Desert were dated using quartz optically stimulated luminescence (OSL) and single aliquot regenerative-dose (SAR) protocol. Internal checks of the OSL dating indicate that the SAR protocol is appropriate for equivalent dose (D_e) determination for the samples under study. Combined with the lithologic stratigraphy and the luminescence chronology, the sand dune development in the Mu Us Desert during the Late Pleistocene is discussed. Our results indicate that the sand was mobilized approximately at 91 ka, 71 ka, 48–22 ka, 5 ka, 1 ka, and 0.44 ka; the sand was fixed approximately at 65 ka and Holocene Optimum period in the interior Mu Us Desert. The Mu Us Desert formed at least before ～144 ka, and has shown increasing aridity in the Late Pleistocene.     

New paleomagnetic data from Upper Oligocene–Lower Miocene rocks of the Northern Argentine Puna–Southern Bolivian Altiplano: Constraining the age of vertical axis rotations

Along the Central Andes a pattern of vertical axis rotations has been paleomagnetically identified. Such rotations are counterclockwise north of Arica Deflection (∼19° S) and clockwise to the south. Different hypothesis and models have been proposed to explain the Central Andean Rotation Pattern (CARP). However, the origin of the CARP is a subject of ongoing debate. Recently, different authors have proposed the possible existence of a close correlation between the time–space distribution of deformation and the amount of registered vertical axis rotations in the Southern Central Andes. In order to further investigate such relationship, new paleomagnetic studies were carried out in Upper Oligocene–Lower Miocene rocks of the Northern Argentine Puna and the Southern Bolivian Altiplano. Our results indicate that while one of the sampled localities did not undergo significant vertical axis rotations, the other two recorded clockwise vertical axis rotations larger than 30°. These results suggest the occurrence of small-block rotations in the Southern Bolivian Altiplano–Northern Argentine Puna prior to 15 Ma, which would correspond to the local accommodation of the regional deformation field.     

The radiocarbon reservoir effect in proglacial lakes: Examples from Antarctica

We studied the apparently old radiocarbon ages from lakes in the dry valleys of Antarctica. The radiocarbon reservoir effect in these lakes results from two components: the inherited age and the residence age. The inherited age is derived from input of old carbon, primarily from subsurface melt of adjacent glaciers. The residence age comes from in situ aging of lake water in an environment sealed from the atmosphere. Our results indicate that surface melt of glaciers introduces little ancient carbon to the lake system, because of rapid gas equilibration with the atmosphere. Subsurface melt in lakes with large glacier cross-sectional areas at the grounding line, however, can contribute a significant amount of ancient carbon, leading to lake-bottom reservoir effects in excess of ∼ 2700 yr. This value can increase to ∼ 20,000 yr immediately at the grounding line. In most lakes, however, surface melt far exceeds that from the subsurface and dilutes the effect of ancient carbon, making the inherited age relatively low. Residence ages generally are on the order of a few thousand years, but can be as much as ∼ 10,000 yr. Because a residence age is reset when the lake loses its ice cover and is exposed to wind-driven mixing, its magnitude can provide important information about lake history.     

Spatial–temporal changes in Andean plateau climate and elevation from stable isotopes of mammal teeth

Paleoelevation constraints from fossil leaf physiognomy and stable isotopes of sedimentary carbonate suggest that significant surface uplift of the northern Andean plateau, on the order of 2.5 ± 1 km, occurred between ～ 10.3 and 6.4 Ma. Independent spatial and temporal constraints on paleoelevation and paleoclimate of both the northern and southern plateau are important for understanding the distribution of rapid surface uplift and its relation to climate evolution across the plateau. This study focuses on teeth from modern and extinct mammal taxa (including notoungulates, pyrotheres, and litopterns) spanning ～ 29 Ma to present, collected from the Altiplano and Eastern Cordillera of Bolivia (16.2°S to 21.4°S), and lowland Brazil. Tooth enamel of large, water-dependent mammals preserves a record of surface water isotopes and the type of plants that animals ingested while their teeth were mineralizing. Previous studies have shown that the δ¹⁸O of modern precipitation and surface waters decrease systematically with increasing elevations across the central Andes. Our results from high elevation sites between 3600 and 4100 m show substantially more positive δ¹⁸O values for late Oligocene tooth samples compared to < 10 Ma tooth δ¹⁸O values. Late Oligocene teeth collected from low elevation sites in southeast Brazil show δ¹⁸O values similar (within 2‰) to contemporaneous teeth collected at high elevation in the Eastern Cordillera. This affirms that the Andean plateau was at a very low elevation during the late Oligocene. Late Oligocene teeth from the northern Eastern Cordillera also yield consistent δ¹³C values of about ? 9‰, indicating that the environment was semi-arid at that time. Latitudinal gradients in δ¹⁸O values of late Miocene to Pliocene fossil teeth are similar to modern values for large mammals, suggesting that by ～ 8 Ma in the northern Altiplano and by ～ 3.6 Ma in the southern Altiplano, both regions had reached high elevation and established a latitudinal rainfall gradient similar to modern.     

GPS constraints on the deformation of Azerbaijan and surrounding regions

In this study, we present new GPS observations in Azerbaijan to provide an improved basis for determining the distribution of crustal deformation throughout the country and surrounding areas. The deformation field in the region has been analyzed with a dense GPS network configuration and a reliable quantification of the ongoing deformation was achieved. Results show that while contraction is dominant over the whole region, it is mostly concentrated on the middle and eastern parts of Caucasus Thrust Fault reaching up to 6.4 ± 0.2 mm/yr and Lesser Caucasus Fault does no accommodate more than 1–2 mm/yr of contraction. New network also clearly substantiates that the West Caspian Fault, which is a continuation of Caucasus Thrust Fault in the south, accommodates right-lateral slip rates of 7.1 ± 0.3 mm/yr in addition to 5.5 ± 0.3 mm/yr contraction rates.     

Linking human-biophysical interactions with the trophic status of Dal Lake,Kashmir Himalaya,India

The study analyses the long-term biophysical and demographic changes in Dal lake, located in the heart of Srinagar city, Kashmir India, using a repository of historical, remote sensing, socio-economic and water quality data supported by the extensive field observations. The lake faces multiple pressures from the unplanned urbanization, high population growth, nutrient load from intensive agriculture and tourism. The data showed that the lake has shrunk from 31 km² in 1859–24 km² in 2013. Significant changes were observed in the land use and land cover (LULC) within the lake (1859–2013) and in the vicinity of the lake (1962–2013). Analysis of the demographic data indicates that the human population within the lake has shown more than double the national growth rate. Additionally, 7 important water quality parameters from 82 well distributed sites across the lake were analyzed and compared with the past data to determine the historical changes in the water quality from 1971 to 2014. The changes in the LULC and demography have adversely affected the pollution status of this pristine lake. Ortho-phosphate phosphorous concentration has increased from 16.75 μg L⁻¹ in 1977–45.78 μg L⁻¹ in 2014 and that of the nitrate-nitrogen from 365 μg L⁻¹ to 557 μg L⁻¹, indicating nutrient enrichment of the lake over the years. Built-up area within the lake has increased 40 times since 1859, which, together with the changes in the population and settlements, have led to the high discharge of untreated nutrient-rich sewage into the lake. Similarly the expansion of floating gardens within the lake and agriculture lands in the catchment has contributed to the increased nutrient load into the lake due to the increasing use of fertilizers. The information about the existing land cover, demography and water quality was integrated and analyzed in GIS environment to identify the trophic status of the lake. The analysis indicated that 32% of the lake falls under sever degradation, 48% under medium degradation while as 20% of the lake waters are relatively clean. It is believed that the results provide improved knowledge and insights about the lake health and causal factors of its degradation necessary for effectively restoring its ecological and hydrological functionality.     

Optical luminescence dating of a loess section containing a critical tephra marker horizon,SW North Island of New Zealand

A new IRSL dataset is presented for the age and setting of a critical Late Glacial Maximum tephra isochron marker. The rhyolitic tephra, known as the Kawakawa Tephra, occurs as a 14 cm thick layer within a 5.9 m thick loess section overlying alluvial gravels in the Rangitikei River valley, SW North Island of New Zealand. Ages range from 21 at the base to 5 ka near the top of the loess and bracket an age of 17.0 ± 2.2 for the tephra. The new IRSL ages are in agreement with published and unpublished luminescence ages from other localities of loess, sand and ash above and below the tephra and of the tephra itself, that indicate an age of ca. 19 ka for the Kawakawa Tephra. This age is considerably younger than the generally accepted ¹⁴C 27.1 ka cal yrs BP age of the Kawakawa Tephra and highlights an unresolved discrepancy between the two dating systems.     

Quartz OSL dating of archaeological sites in Xiao Qaidam Lake of the NE Qinghai–Tibetan Plateau and its implications for palaeoenvironmental changes

In the past decades, archaeologists have found evidences for prehistorical human activity in the Qinghai–Tibetan Plateau (QTP). In 1982, some Paleolithic stone tools were found in a section from a terrace of the Xiao Qaidam Lake in the Qaidam Basin, NE of the QTP. The age of this Paleolithic site has remained unknown by far. Some believed that the age of human inhabitation in this Paleolithic site was about 30 ka. In this study, quartz optically stimulated luminescence was used to date 10 samples collected from four sections in the Xiao Qaidam Lake, using the single-aliquot regeneration-dose protocol. The two samples from section XCDH2, which is from a lake terrace about ～7–8 m above the present lake level and in which the top gravel layer contains stone tools, were not well-bleached before deposition. Their ages (>101 and >159 ka) determined by SAR should be considered minimums. OSL dating results of six samples from two sections (XCDH1 and XCDH3) of an adjacent lake terrace, which is ～12 m above the present lake level, suggest two possibilities for the age of the tool-bearing gravel layer: (1) younger than ～3 ka if the lake terrace of XCDH2 is younger than the terrace represented by XCDH1 and XCDH3; or (2) between ～3 and 11 ka if these two terraces are part of the deposit of the same time period. In either case, the age of the archaeological layer should be much younger than the previously proposed ～30 ka. As the climate in the early Holocene after 11 ka was increasingly warm and the Xiao Qaidam Lake area could be suitable for human inhabitation then, we deduce that the age range of ～3–11 ka is more likely the time frame for this archaeological site. The age of 3.1 ± 0.3 ka for the surface of terrace XCDH1/XCDH3 suggests a significant lake level decrease after this time and a corresponding arid event at ～3 ka; the lake level did not reach this level again after that time. Section XCDH4 is more than 40 m above the present lake level, and two samples gave ages of 37 ± 4 and 51 ± 4 ka. These two dates and the dates from the other sections demonstrate that two lake levels higher than present existed for Xiao Qaidam Lake, one at ～12 m and dated ～3–11 ka and the another at >40 m and dated ～37–51 ka.     

Timing for high lake levels of Qinghai Lake in the Qinghai-Tibetan Plateau since the Last Interglaciation based on quartz OSL dating

Qinghai Lake is situated in the northeast of the Qinghai-Tibetan Plateau (QTP). Its size and proximity to the junction of three major climate systems make it sensitive to climate changes. Some investigations on shorelines of Qinghai Lake suggested highstands during MIS 3, but to what extent the lake level was higher than today is yet undetermined. Others proposed that the maximum highstands probably dated to MIS 5. It has also been shown that the lake level 120 m higher than today occurred at around 12 ka. Most of these previous ages were obtained using ¹⁴C dating or multiple-aliquot IRSL/OSL dating. For ¹⁴C dating, because of the dating limit (<40 ka) and the lack of suitable dating materials in this arid area, it is difficult to establish reliable chronological control. In the present study, seven samples collected from lacustrine deposits (five samples) and sand wedges (two samples) were dated using quartz optically stimulated luminescence (OSL) with the single aliquot regenerative-dose (SAR) protocol. OSL dating results showed that (1) the lake had experienced two high lake levels, one was in MIS 5 and another in early to middle MIS 3; (2) no evidence of high lake levels in MIS 4 has been found; (3) the alluvial gravels, whose surface is at an elevation of ～3246 m, were formed at least 28.8 ± 2.3 ka ago, and the widespread sand wedges within the alluvial gravels were formed during the period of 15.1–28.8 ka, which implied that the lake level had not reached an elevation of ～3240 m after 28.8 ± 2.3 ka.     

Rapid late Miocene rise of the Bolivian Altiplano: Evidence for removal of mantle lithosphere

The oxygen isotopic compositions of carbonates deposited in the northern Altiplano demonstrate a rapid change in late Miocene time, which we attribute to an increase in elevation. Rainfall samples over an elevation transect adjacent to the Altiplano of northern Bolivia display a systematic decrease in mean annual δ¹⁸O values and define a local δ¹⁸O vs. altitude gradient [R. Gonfiantini, M.-A. Roche, J.-C. Olivry, J.-C. Fontes, G.M. Zuppi, The altitude effect on the isotopic composition of tropical rains, Chem. Geol. 181 (2001) 147-167.], which we apply to paleo-meteoric water values determined from carbonates. Age constraints from magnetostragraphy and paleoelevation estimates suggest surface uplift of ∼2.5 to 3.5 km occurred between ∼10.3 Ma and 6.8 ± 0.4 Ma, when the Altiplano rose to its current elevation. Only the removal of dense eclogitic lower crust and mantle lithosphere can generate a change of this magnitude and rapidity. This change coincides with an ∼30% decrease in the rate of convergence between the South America and Nazca plates and the propagation of deformation into the eastern Subandean zone, which we infer to have resulted from the increase in the force per unit length applied by the elevated Andean plateau to the surrounding lowlands.     

GPR to constrain ERT data inversion in cavity searching: Theoretical and practical applications in archeology

I used theoretical forward models to show that a cavity embedded in a stratified sedimentary sequence can induce an equivalence problem in the ERT data inversion. Conductive top soil increases the misfit between the ground feature and the ERT model. The misfit depends on array and stratigraphy sequences. The latter induce an equivalence problem that manifests itself as wrong cavity depth positioning. The misfit is greater in the data acquired with Schlumberger array than with dipole–dipole.The ambiguity of ERT data inversion problems was tested in the detection of cavities linked to an 8th–6th century B.C. Sabine tomb, 3 m wide × 3 m long × 2 m high, excavated from a shaly gray volcanic ash (cinerite) layer covered by semi-lithoid tuff and top soil layers. In the real study I reduced the ambiguity in the inverse problem of ERT data using a priori information on geometry and resistivity of the cavity. The constrains were carried out from georadar data acquired with 80 and 200 MHz antenna. I demonstrate that this procedure has a practical application in cavity detection, and is a key to the reduction of the uncertainty inherent in the inversion process of ERT data.     

OSL dating of sediments from the Gobi Desert,Southern Mongolia

The present study focuses on the chronological relationship between alternating dune sand and silty water-lain sediments in the central part of the Khongoryn Els dune field in the Gobi Desert, Southern Mongolia. The 23 m high section evolved from the construction of a natural dam by west–east moving sand dunes and fluvial inundation by a river system from the mountain ranges in the south. To resolve the chronology of events, optically stimulated luminescence (OSL) dating was applied and from sedimentological and geochemical analysis the depositional processes could be characterised. Quartz OSL dating of these sediments is hindered by feldspar contamination. Thus, dating of coarse-grain K-feldspars is applied to provide a more reliable chronostratigraphy. As this fraction might be influenced by signal loss over geological time scales, the extent of fading is measured and corrected for. The resulting ages fit well in a supraregional reconstruction of Central Asian palaeoclimate. The data imply that the basal aeolian sediments were deposited 27 ka ago, while the major part of the profile was accumulated in a rather short period of time around ～15 ka. The temporal differentiation implies that the stratification of aeolian and fluvial sediments is not caused by long term climatic variations. It rather represents arid conditions with episodical fluvial activity. Samples between 20 and 15 m depth could not be taken, but it is assumed that this part of the section represents an extremely arid time period with an intensive remobilisation of sand around LGM. A dune overlying the section was deposited during the Late Holocene and represents the ongoing aridity in this region.     

Balancing the global oceanic neodymium budget: Evaluating the role of groundwater

The distinctly different, ε_Nd(0) values of the Atlantic, Indian, and Pacific Oceans requires that the residence time of Nd in the ocean (i.e., τ_Nd) be on the order of, or less than, the ocean mixing time of ∼ 500–1500 yr. However, estimates of τ_Nd, based on river influxes, range from 4000 to 15,000 yr, thus exceeding the ocean mixing time. In order to reconcile the oceanic Nd budget and lower the residence time by roughly a factor of 10, an additional, as yet unidentified, and hence “missing Nd flux” to the ocean is necessary. Dissolution of materials deposited on continental margins has previously been proposed as a source of the missing flux. In this contribution, submarine groundwater discharge (SGD) is examined as a possible source of the missing Nd flux. Neodymium concentrations (n = 730) and ε_Nd(0) values (n = 58) for groundwaters were obtained from the literature in order to establish representative groundwater values. Mean groundwater Nd concentrations and ε_Nd(0) values were used along with recent estimates of the terrestrial (freshwater) component of SGD (6% of river discharge on a global basis) to test whether groundwater discharge to the coastal oceans could account for the missing flux. Employing mean Nd concentrations of the compiled data base (i.e., 31.8 nmol/kg for all 730 analyses and 11.3 nmol/kg for 141 groundwater samples from a coastal aquifer), the global, terrestrial-derived SGD flux of Nd is estimated to range between 2.9 × 10⁷ and 8.1 × 10⁷ mol/yr. These estimates are of the same order of magnitude, and within a factor of 2, of the missing Nd flux (i.e., 5.4 × 10⁷ mol/yr). Applying the SGD Nd flux estimates, the global average ε_Nd(0) of SGD is predicted to be − 9.1, which is similar to our estimate for the missing Nd flux (− 9.2), and in agreement with the mean (± S.D.) ε_Nd(0) measured in groundwaters (i.e., ε_Nd(0) = −8.9 ± 4.2). The similarities in the estimated SGD Nd flux and corresponding ε_Nd(0) values to the magnitude and isotope composition of the missing Nd flux are compelling, and suggest that discharge of groundwater to the oceans could account for the missing Nd flux. Future investigations should focus on quantifying the Nd concentrations and isotope compositions of groundwater from coastal aquifers from a variety of coastal settings, as well as the important geochemical reactions that effect Nd concentrations in subterranean estuaries in order to better constrain contributions of SGD to the oceanic Nd budget.     

Luminescence dating of baked earth and sediments from the Qujialing archaeological site,China

The Qujialing site is a representative Neolithic archaeological site in the middle reaches of the Yangtze River, China. Absence of suitable material for radiocarbon dating in this region makes the timing of the similar sites difficult. Here we applied optically stimulated luminescence (OSL–SAR) and thermoluminescence (TL–SAR) techniques to date the archaeological and natural deposits from the Qujialing site with known age, testing the techniques on samples at archaeological sites in this region. The results showed that the luminescence properties of quartz from sediment and baked earth samples are very similar. The quartz OSL ages obtained for a sediment sample and a baked earth sample from the cultural layer are 5.4 ± 0.3 and 5.1 ± 0.3 ka, respectively. The quartz TL age of the baked earth sample is 5.6 ± 0.5 ka. These dates are consistent with the calibrated radiocarbon ages (4.9 ± 0.1 and 5.1 ± 0.1 ka cal BP (±1σ)) of the two charcoal samples from the cultural layer at a nearby locality, and are also in agreement with the age of Qujialing culture period. The results indicate that the OSL dating techniques can be applied to date similar archaeological sites in the middle reaches of the Yangtze River, China.     

Solar activity imprints in tree ring width from Chile (1610–1991)

We have investigated the solar activity signal in tree ring data from two locations in Chile. The tree ring time series extended over a period of ∼400 yr. Spectral and wavelet analysis techniques were employed. We have found evidence for the presence of the solar activity Schwabe (∼11 yr), Hale (∼22 yr), fourth-harmonic of the 208-yr Suess cycle (∼52 yr) and Gleissberg (∼80 yr) cycles. The Gleissberg cycle of tree ring data is in anti-phase with solar activity. Wavelet and cross-wavelet techniques revealed that the periods found are intermittent, possibly because solar activity signals observed in tree rings are mostly due to solar influence on local climate (rainfall, temperature, and cloud cover) where trees grow up. Further, cross-wavelet analysis between sunspot and tree ring time series showed that the cross power around the 11 yr solar cycle is more significant during periods of high solar activity (grand maximum) than during periods of low solar activity (grand minimum). As Glaciar Pio XI is practically at the Pacific Ocean level, the tree-ring response may be stronger due to the heating of the Pacific Ocean water following an increase of the solar radiation incidence rather than at the higher altitudes of Osorno region.     

Changes in ice phenology on polish lakes from 1961 to 2010 related to location and morphometry

Observations of lake ice at the shore, complete ice cover, ice duration, ice thickness and other measures for 18 Polish lakes were collected for the 50 year period (1961–2010). Average ice dates in early winter became later: first appearance of ice along shore 2.3 days decade⁻¹ and complete ice cover 1.2 days decade⁻¹ while complete ice cover disappeared earlier (5.6 days decade⁻¹) as did last ice at the shore (4.3 days decade⁻¹). The duration of ice cover decreased by 5.6 days decade⁻¹ and average ice thickness declined by 6.1 cm decade⁻¹. The magnitude of these values for individual lakes decreased from eastern to western Poland. This geographic gradient is likely related to regional atmospheric circulation because in winter this part of Europe is strongly affected by continental air, an influence that is greater in the east. A multivariate redundancy analysis (RDA), used in order to examine the dependence of ice measures on lake physical properties and location, indicated longitude and altitude as key factors explaining lake ice dynamics such as the disappearance of ice and ice cover, ice cover duration and thickness. Lake volume and average depth influenced mostly the appearance of ice and ice cover.     

OSL-dating the Quaternary landscape evolution in the Vértes Hills forelands (Hungary)

Fluvial, colluvial, and aeolian sediments were dated by optically stimulated luminescence (OSL) on quartz to improve the chronological framework for Quaternary sedimentation and landscape evolution in the forelands of the Vértes Hills (central Hungary). The separated quartz was suitable for age determination based on an OSL SAR protocol. Most samples have asymmetric equivalent dose distributions and OSL ages were calculated by the mean, central, and minimum D_e values. Considering geomorphology and earlier age data from the area, the central D_e values seem most appropriate for age calculation. A fan on the geomorphological level QV in the western foreland of the Vértes Hills was deposited 79–75 (±8) ka ago. In the south-eastern foreland an alluvial fan on level QIIb is at most 42 ± 4 ka old. Fluvial incision and aggradation occurred 16–10 (±1) ka ago on the geomorphic surface QIIa. Loess is 14 ± 1 ka old, and slope sedimentation was active 11–9 (±1) ka ago. Our OSL data demonstrate that in the north-western foreland of the Vértes Hills wind remained an important agent after the last glacial times, into the early Holocene (9–8 ± 1 ka) and was able to accumulate large aeolian dunes.     

Drainage migration and out of sequence thrusting in Bhalukpong,Western Arunachal Himalaya,India

In the foreland regions of the Western Arunachal Himalaya (WAH), geological studies along the Kameng river (between Tipi village and the Himalayan Frontal Thrust (HFT)) reveal four levels of unpaired terraces and a paired terrace. In WAH, wrench deformation of HFT zone resulted in a SE propagation of the Balipara anticline and it is suggested that the Mikir high basement controls its orientation. Ages of terrace surfaces from Siwaliks suggest that since the Late Pleistocene, Kameng River migrated at a rate varying between ∼7.5 cm/yr in upper reaches and ∼13.5 cm/yr towards northeast due to HFT related uplift. In the Brahmaputra plains, luminescence ages of abandoned paleochannel deposits suggest eastward shifting of the Kameng river at an average rate of ∼1 m/yr. Field evidences between Bhalukpong and Tipi villages show Pliocene strath and Quaternary terrace surfaces, displaced by faults that do not correspond to the mapped faults in the foreland region. We interpret them as out-of-sequence thrusts (OOSTs). This is the first such report of OOST in the NE Himalaya. Presence of active OOST is inferred by similar age (∼1 ka) and differing incision rates of the surface of same terrace (T_2b) in adjacent locations. This suggests that OOSTs in the western Arunachal Siwalik are <1 ka. Average slip rate and horizontal shortening rate on OOST during the Holocene, are calculated as ∼12 mm/yr and 7 mm/yr respectively. Thus any estimation of Holocene shortening in the Siwalik therefore, needs to incorporate slip along the OOSTs given that it accommodates a significant amount of N-S compression of the Himalayan fold-and-thrust belt. The reason for OOST in the WAH Siwalik foreland is discussed in terms of the critical wedge dynamics arising from erosion via tectonics-climate interaction. We estimate a minimum slip rate of Siwalik as ∼27 mm/yr during the Holocene and suggest acceleration in shortening rates east of Bhutan.