Dynamics of peat accumulation processes in the areas of the periglacial zone of the basin watershed of Tugur-Nimelen rivers

The paper considers the features of waterlogging of a flat watershed, unique in its structure and evolution, between the valley complexes of the two largest watercourses of Khabarovsk Territory. The Tugur and Nimelen rivers had rather powerful debit of water flows during the Pleistocene and were repeatedly redirected from the northern azimuth (the Sea of Okhotsk) to the southern one (the Amur catchment). This process continued partly at the early stages of the Holocene, as the stratigraphy of the peat deposits of the bogs formed indicates here.

The Drac paleo-valleys: a long-term archive of fluvial dynamics in the periglacial zone of the western French Alps

<p>The evolution of the Alpine mountain belt during the Quaternary is strongly controlled by periodic glaciations and deglaciations. The significant erosion during these glacial/interglacial cycles has left very few sedimentary archives to study the surface dynamics within the mountain belt over the last hundreds of thousands of years. Valleys within the periglacial zone are the best candidates to target long-term geological archives in the Alps because they potentially preserve ancient fluvial deposits that have been preserved from glacial abrasion. The Drac River in the French western Alps preserves the alluvial fills of three generations of paleo-valleys, which were filled in response to glacial damming of the river and subsequently re-incised during glacial retreat. Detailed 3D mapping of the paleo-valleys was carried out to constrain their geometry and reconstruct the evolution of the Drac fluvial profile over time. The age of the fills of the three paleo-valleys was constrained by measuring the luminescence signal of feldspars, targeting sandy intervals within the coarse fluvial deposits. Dating these fills allows to quantitatively constrain the alluviation and incision dynamics of the Drac paleo-valleys. The onset of alluviation of the most recent paleo-valley occurred before the Last Glacial Maximum, between 40 ka and 90 ka BP (MIS 3 -5). The fill of the intermediate paleo-valley is dated to the previous cold period at 134±20 ka BP (MIS 6). Finally, the oldest paleo-valley was filled more than 200 ka ago. The filling periods correspond to the global climatic cooling stages and are much longer than the incision phases, which took place during global warm intervals. The pattern of sedimentary filling implies it is controlled by an increase in sediment flux in the context of glacial advance, while the incision phases are due to rapid base-level lowering linked to the retreat of glaciers damming the Drac basin. Complementary luminescence dating is currently carried out on the terraces, at the tops of the fillings, and will lead to a better understanding of the control of glaciations on the dynamics of alluvial deposits in the periglacial zone.</p>

Timing and Sedimentary Record of Late Quaternary Fluvio-Aeolian Successions of the Tura-Pyshma Interfluve (SW Western Siberia, Russia)

The sedimentary record of aeolian deposits and geomorphic features of the aeolian landforms of Northern Eurasia contain important information that allows us to better understand the climate and environments of the Late Glacial and Early Holocene periods. At the same time, the degree of scientific knowledge about the timing of aeolian activity, as well as the landscapes that existed during these periods, differs significantly for different parts of this vast territory. Data on the sedimentological record and age estimations of aeolian phases are practically absent for the periglacial zone of Western Siberia, in contrast to that of Europe. This paper presents the first data on the Late Quaternary fluvio-aeolian environments of the southwestern part of Western Siberia, using two sections as examples. Our methods included field investigations, analysis of grain-size and chemical composition, quartz grain morphoscopy and infrared optically stimulated luminescence (IR-OSL) and AMS dating. The obtained results show that aeolian sands are common covering deposits within the study area. Two stages of aeolian activity were identified: the first during the Boreal period (9.2–10.2 ka BP), and the second during the Atlantic period, beginning near 7 ka BP.

Mire Development and Disappearance due to River Capture as Hydrogeological and Geomorphological Consequences of LGM Ice-Marginal Valley Evolution at the Vistula-Neman Watershed

The advances and retreats of ice sheets during Pleistocene significantly changed high- and mid-latitude landscapes and hydrological systems, albeit differently, in North America and Europe. On the southern margin of the Last Glacial Maximum (LGM) in the Baltic Sea basin, a specific type of valley has developed between glacial margins and upland or mountain slopes. We studied new geological data (boreholes, electrical resistivity imaging (ERI) from this geomorphic setting in Northeast Poland to understand: (1) how the landscape and river network evolved to eventually produce peat mires during the Holocene, and (2) the nature of groundwater recharge to fens in the upper Biebrza Valley. We present the results on a geological cross-section with hydrogeological interpretation. We also discuss regional geomorphology. In addition, we present the LGM extent derived from a spatial distribution of Vistulian (Weichselian) terminal moraines. These end moraines are also interpreted as Saalian kames. Thus, we additionally present another method of LGM extent delineation from a physicogeographical division. We link the steep slopes of the studied valley walls (kame terrace fronts) with thermokarst erosion in the periglacial zone. We then document the hydrogeological window (DISCONTINUITY in the till layer over the confined aquifer), which enables the outflow of groundwater into the peat bog. Although minerotrophic fen mire development in the study area is likely to be sustained in the near future through sufficient groundwater supply, the projected capture of the Biebrza River by the Neman River will not allow for sustaining peatland development.

First Findings of Buried Late-Glacial Paleosols within the Dune Fields of the Tomsk Priobye Region (SE Western Siberia, Russia)

Buried soils within aeolian deposits are considered an important tool for diagnosing, determining the age, and estimating the intensity of aeolian processes at the transition from the Pleistocene to the Holocene in the Northern Hemisphere. Late Pleistocene aeolian coversands and ancient inland dunes are widely distributed in the periglacial zone of Western Siberia. In contrast to the territories of Central and Eastern Europe, the paleosol archive of the aeolian sands and dunes of Western Siberia has not yet been studied. This paper presents the first findings of late Pleistocene paleosols within the ancient inland dunes in the southeast of Western Siberia (Ob–Tomsk interfluve, Tomsk region). The soils and their stratigraphic position were studied in the outcrop of the quarry, located in the junction zone of the second Tom river terraces and the ancient valley. Two types of paleosols were identified. The first one is confined to the central part of a small dune and is represented by a slightly developed Albic Arenosol with fragmentary humus horizon Ahb and a well-pronounced Eb. It can probably be considered as an analogue of the European Usselo soil. The second paleosol was found at the bottom of the interdune depression. It is represented by a brown Bwb horizon and probably corresponds to a Brunic Arenosol (Dystric). The second paleosol is characterized by a higher content of clay fraction and organic carbon, the presence of weak signs of illuviation, and richer and more diverse mineral composition. This soil is apparently an analogue of the European Finow soil. Radiocarbon dating of the charcoals found in the paleosols suggests that the first dates from the Younger Dryas (ca. 12,036 cal. yr. BP), and the second one from the Allerød (ca. 13,355 cal. yr. BP). The study results propose that the natural environment in the periglacial zone of the south of Western Siberia was generally similar to those in Central and Eastern Europe, and the activation of aeolian processes, which led to the formation of a dune relief, occurred at about the same time.

The lower altitudinal limit of the periglacial climazonal belt on Kopaonik Mountain (Serbia)

The morphostructural relief of the highest parts of the central Kopaonik Mt was altered by exogenous agents, by denudation as a primary and periglacial processes as a secondary agent. Previous geomorphological studies were mostly focused on the traces of the Pleistocene glaciation, although no reliable evidence was found for this. Recent research, in the part of the mountain above 1,700 m of absolute height, points to geomorphological phenomena resulting from more recent processes within the periglacial environment. By means of geomorphological reconnaissance, analysis and mapping of the highest part of the Kopaonik mountain massif, forms of relief were studied, the ones that according to their morphology correspond to the periglacial forms and processes described in the conditions of high latitudes and high mountains. Determining the spatial coverage of the periglacial belt, especially its lower limit on Kopaonik Mt, is important for understan-ding the distribution of this climatic morphology both in Serbia and in South East Europe. The research contributes to one of the primary aims of exploring the concept of the periglacial zone, in terms of the regional distribution of its specific relief forms.

GENETIC TYPES OF CATASTROPHIC AVALANCHE-LIKE FLOW AND DYNAMIC TYPES OF THE GLACIERS, WHICH ARE HAZARDOUS FOR THEIR MANIFESTATION

Согласно современным представлениям, все лавинообразные потоки генетически однотипны и имеют экзогенную склоново-гравитационную природу. Катастрофические события, произошедшие в последнее время на ледниках Центрального Кавказа и в сопредельных с ними районах перигляциальной зоны, показывают, однако, что такой тип лавинообразных потоков не исчерпывает всего разнообразия существующих в природе их типов. Одним из типов чрезвычайно опасных катастрофических лавинообразных потоков являются газодинамические, генетически связанные с пароксизмальными взрывоподобными направленными газодинамическими выбросами ледников, впервые установленными автором при изучении Колкинской (Геналдонской, Кармадонской) катастрофы 2002 года. К этому же генетическому типу относятся, в частности, Уаскаранские (Перу) катастрофические лавинообразные потоки 1962 и 1970 гг., а также Колкинские (Геналдонские) 1902 и 1752 гг., Девдоракские (Казбекские) 1832 и 1776 гг., Араратские 1840 г. и некоторые другие. Важнейшей особенностью катастрофических лавинообразных потоков этого типа является чрезвычайно высокоскоростное, нередко субгоризонтальное (и даже направленное вверх) движение огромных ледово-каменных масс на значительной части пути по воздуху. According to the modern concepts, all of the avalanche flows are genetically similar and have exogenous slope-gravitational nature. Catastrophic events happened in recent years on the glaciers of the Central Caucasus and the adjacent areas of periglacial zone indicate, however, that this type of avalanche flows does not exhaust the diversity of their types existing in nature. One of the extremely dangerous catastrophic avalanche types is gas-dynamic one genet-ically associated with paroxysmal explosive directional gas dynamic surge of glaciers, for the first time determined by the author during the study of Kolka (Genaldon, Karmadon) disaster of 2002. In particular, Waskaran (Peru) catastrophic avalanche flows in 1962 and 1970, as well as Kolka (Genaldon) in 1902 and 1752, Devdorak (Kazbek) in 1832 and 1776, Ararat flows in 1840 and some others are referred to the same genetic type. The most important feature of such type of catastrophic avalanche flows is extremely high speed, often sub-horizontal (and even upward) movement of huge ice-rock masses over the air on a large part of the way.