Климат, лед, вода, ландшафты

Climate, ice, water, landscapes

Рудой Алексей Николаевич

Early Holocene (8.6 ka) rock avalanche deposits, Obernberg valley (Eastern Alps): Landform interpretation and kinematics of rapid mass movement

Cover image

Early Holocene (8.6 ka) rock avalanche deposits, Obernberg valley (Eastern Alps): Landform interpretation and kinematics of rapid mass movement

Geomorphology

Copyright © 2012 Elsevier B.V. All rights reserved


  • Marc Ostermanna, Corresponding author contact information, Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript ,
  • Diethard Sandersa,
  • Susan Ivy-Ochsb, c,
  • Vasily Alfimovc,
  • Manfred Rockenschaubd,
  • Alexander Römerd
  • a Institute for Geology and Palaeontology, University of Innsbruck, A-6020 Innsbruck, Austria
  • b Department of Geography, University of Zurich, CH-8057 Zurich, Switzerland
  • c Laboratory of Ion Beam Physics, ETH Zurich, CH-8093 Zurich, Switzerland
  • d Geological Survey of Austria, A-1030 Vienna, Austria

Abstract

 

In the Obernberg valley, the Eastern Alps, landforms recently interpreted as moraines are re-interpreted as rock avalanche deposits. The catastrophic slope failure involved an initial rock volume of about 45 million m³, with a runout of 7.2 km over a total vertical distance of 1330 m (fahrböschung 10°). 36Cl surface-exposure dating of boulders of the avalanche mass indicates an event age of 8.6 ± 0.6 ka. A 14C age of 7785 ± 190 cal yr BP of a palaeosoil within an alluvial fan downlapping the rock avalanche is consistent with the event age. The distal 2 km of the rock-avalanche deposit is characterized by a highly regular array of transverse ridges that were previously interpreted as terminal moraines of Late-Glacial. ‘Jigsaw-puzzle structure’ of gravel to boulder-size clasts in the ridges and a matrix of cataclastic gouge indicate a rock avalanche origin. For a wide altitude range the avalanche deposit is preserved, and the event age of mass-wasting precludes both runout over glacial ice and subsequent glacial overprint. The regularly arrayed transverse ridges thus were formed during freezing of the rock avalanche deposits.

Geomorphology,

Vol. 171-172, 15 October 2012, Pages 83–93

 

Highlights

► Deposits of purported glacial origin have been re-interpreted as rock avalanche. ► The age of the rock avalanche is dated to 8.6 ± 0.6 ka. ► Regularly-spaced transversal ridges record mechanic waves in the rock avalanche.

 

1. Introduction

Rockslides and rock avalanches include gravity-driven, rapid slope failures that are larger than about 105 to 106 m3 in volume (Evans et al., 2006). Most rock avalanches post-dating the Last Glacial Maximum (LGM) in the Alps are readily recognized by their shape and size as well as by an extremely poorly sorted composition ranging from cataclastic gouge to megablocks ( [Pollet and Schneider, 2004] and [Crosta et al., 2007]). At a few locations, however, the interpretation of landforms composed of very poorly sorted deposits remains controversial. For instance, transverse and lateral ridges of rock avalanches may appear similar to terminal and lateral moraines of glaciers. Diamicts of fine-grained matrix hosting polished and striated rock fragments may, either, represent basal till, or may form in rock avalanches. In addition, rock avalanches can flow out over long distances, which may promote confusion with glacial sediments (cf. Hewitt, 1999).

In the Obernberg valley, Austria, the character of a rock avalanche deposit led to diverse interpretations for more than a hundred years. In its distal part, which is about 2 km in length, the avalanche mass shows a regular arrangement of ridges and hillocks that are roughly transversal to valley axis. Frech (1903), who first investigated these deposits, interpreted their entirety as a rock avalanche. Paschinger (1953) agreed, but interpreted the ridges as a result of decay of underlying glacial ice. Later, based solely on the morphology of ridges and hillocks, the landforms were thought to be terminal moraines and kames ( [Magiera, 2000][Ebner et al., 2003] and [Wastl, 2007]). Herein, we present a survey based on field investigations, volume estimation using airborne laser scanning image, a digital elevation model and electrical tomography, and proxy event ages produced by radiocarbon and cosmic ray-exposure dating. Our results indicate that the purported glacial landforms accumulated from a rock avalanche 8.6 ± 0.6 ka ago. We discuss: (a) a potential relation of rock avalanching with the 8.2-ka climatic phase in the Alps, and (b) the significance of transversal ridges with respect to rock avalanche kinematics.

2. The study area

The SW–NE trending Obernberg valley is a 9-km-long tributary of the Wipp valley, about 25 km south of Innsbruck (Fig. 1). Over most of its extent, the Wipp valley follows the Brenner extensional fault. The hangingwall of the Brenner fault consists of the Oetztal–Stubai basement complex with an overlying, parautochthonous Mesozoic succession and two superposed thrust nappes (Blaser and Steinach nappes); the footwall is comprised of variegated metamorphic successions of a different tectonostratigraphic unit (Fig. 1) (Fügenschuh et al., 1997). Neogene fission-track cooling ages in the footwall adjacent to the Brenner fault, and fault plane solutions of historical earthquakes suggest that the Brenner fault may still be active at a low rate (cf. [Fügenschuh et al., 1997][Fügenschuh et al., 2000][Fügenschuh and Mancktelow, 2003] and [Reiter et al., 2003]). The Obernberg rock avalanche detached from an isoclinally folded, Mesozoic series of calcitic to dolomitic marbles, calcitic phyllites and, subordinately, phyllites and quartzites (Fig. 2) (Rockenschaub et al., 2003). The dip/dip azimuth of schistosity in the isoclinally-folded series ranges from horizontal to 270–320°/10–20° (Reiser et al., 2010). The detachment scarp of the rock avalanche is located about 500 m west, and in the footwall of, an N–S striking normal fault (Portjoch fault) with a vertical throw of at least a few hundred meters. East of the Portjoch fault, the right flank of the See valley and that of the upper Obernberg valley consist mainly of quartz phyllite and mica schist of the Steinach nappe (Fig. 2 and Fig. 3). Whereas the mentioned Mesozoic series is deeply incised by many gullies, and the toes of slopes are covered with talus aprons, there is nearly no fluvial incision and talus formation within the Steinach nappe. The quartz phyllites there tend to form numerous slow moving, shallow to deep, mass movements (Fig. 3).

Full-size image (243 K)

Fig. 1. The Obernberg rock avalanche and rockslides/rock avalanches (red areas) nearby, displayed on the tectonic map of Schmid et al. (2004), with a digital elevation model in the background. Earthquakes in this region according to the NEIC dataset (http://earthquake.usgs.gov/earthquakes) are indicated with multicolored and multi-sized dots. Dot size corresponds to earthquake magnitude, and dot color corresponds to the depth of the epicenters. GS: Gschnitz Stadial locus typicus.

08.10.2012 22:10 1131 24 Комментарии
 

Deepening of inner gorges through subglacial meltwater — An example from the UNESCO Entlebuch area, Switzerland Mirjam Dürst Stuck., Fritz Schlunegger, Fabian Christener, Jan-Christoph Otto, Joachim Götz

Новая интересная работа об интенсивности, механизмах и геоморфологии подледниковых стоков в ПЛМ в Альпах.
Deepening of inner gorges through subglacial meltwater — An example from the UNESCO Entlebuch area, Switzerland

Geomorphology

Copyright © 2012 Elsevier B.V. All rights reserved
Mirjam Dürst Stucki a,⁎, Fritz Schlunegger a, Fabian Christener a, Jan-Christoph Otto b, Joachim Götz b
a Institute of Geological Sciences, University of Berne, Baltzerstrasse 3, CH-3012 Bern, Switzerland
b Department ‘Geography and Geology’, University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria
A b s t r a c t
This paper explores the mechanisms by which inner gorges in the Alps were formed. It focuses on the ca. 1.5-km-long, 80-m-deep, and a few hundred meter wide Lammschlucht located in the northern foothills of the central Alps.We reconstructed the glacial cover using lateral moraines and hanging talus cones that record the elevation of the ice surface at the deglaciation stage of the LGM(Last GlacialMaximum). We used the reconstructed ice thickness patterns to calculate the erosional potential of the subglacialmeltwater. The applied model is based on the principle of energy conservation and yields the pattern of downstream changes of the dynamic pressure, which is considered a measure for erosion potential. The model results suggest a maximum of the dynamic pressure at the end of the inner gorge. We interpret, therefore, that the subglacial meltwater scoured the reach toward the end of the Lammschlucht because of the enhanced dynamic pressure, whichwas ultimately controlled by the ice overburden. Post-glacial fluvial erosion then resulted in a readjustment through a regressive shift of the erosional front along the inner gorge farther upstream. The current location of this front lies almost in the middle of the Lammschlucht inner gorge where a step-pool channel changes into a straight plane-bed channel flowing on a deeply scoured bedrock.
Swiz1
Fig. 1. (A) Overview figure illustrating the location of the Lammschlucht inner gorge in the UNESCO Entlebuch area, at the northern border of the Swiss Alps (black solid line). (B) The Lammschlucht inner gorge with its four segments: (i) upstream of the gorge, (ii) step-pool channel geometries, (iii) straight part with plane-bed channel morphologies, and (iv) downstream of the gorge where the Waldemme River represents a plane-bed geometry. The black circle represents the location of a borehole, where an overdeepening of 7.1 m was documented by the consulting company TerrBohr.

1. Introduction
Inner bedrock gorges have a distinct (valley-in-valley) cross section and may occur in rock and debris slope (Kelsey, 1988; Korup and Schlunegger, 2007; Ouimet et al., 2008; Montgomery and Korup, 2011). They form a convex break in hillslope gradient and are lined by hillslope toes steeper than those of upper valley flanks (Kelsey, 1988; Korup and Schlunegger, 2007). They have been recognized in many parts of the European Alps but preferentially occur at the orogen border such as in proximal Molasse deposits, Penninic Schists Lustrés, Flysch sandstone–mudstone alternations, and Helvetic limestones (Korup and Schlunegger, 2007). The formation of inner gorges requires special conditions, including continued base-level fall, predominance of debris slides, lack of sediment storage in the channel reach, and a topography that is characterized by an initially low relief (Kelsey, 1988). The mechanisms leading to the formation of inner gorges and the timing of their origin are highly debated. Their genesis is probably related to multiple glacial–interglacial phases (Korup and Schlunegger, 2007). For instance, Montgomery and Korup (2011) suggested that inner gorges in the Swiss Alps progressively formed through multiple glacial stages and were thus robust to repeated glaciations. In particular, local evidence for remnant deposits of indurated and weathered glaciofluvial sediment or till within a number of Alpine gorges implies a pre-LGM (Last Glacial Maximum) origin (Cadisch, 1926; De Graaff, 1996; Montgomery and Korup, 2011). Based on erosion rate calculations, Montgomery and Korup (2011) also proposed that the incision of inner gorges in the Swiss Alps began probably before the LGM because the implied average erosion rates for an exclusively postglacial gorge formation are inconsistent with long-term exhumation rates in the Alps. The origin of the inner gorges is likewise partially unresolved. Multiple mechanisms have been used to explain their genesis (Korup and Schlunegger, 2007), including relief rejuvenation by fluvial incision in response to rapid base-level drop (Ahnert, 1988; Kelsey, 1988; Densmore et al., 1997; Bonnet et al., 2001; Stock et al., 2005; Ouimet et al., 2008), repeated glaciations (Mitchell et al., 1999), landsliding focused at hillslope toes (Kelsey, 1988; Densmore and Hovius, 2000), and catastrophic outburst flows from natural dam failures (Knudsen and Marren, 2002; Rudoy, 2002). Despite clear evidence for fluvial downcutting and incision in many places (Valla et al., 2009), an origin related to glacial and subglacial fluvial erosion cannot be completely excluded as they may exhibit undulating longitudinal profiles and contain sections that slope upward. Sharpe and Shaw (1989) described linear hollows and depressions cut into bedrock near Quebec, Canada, that they related to subglacial fluvial erosion. Likewise, in the Molasse foreland basin on the northern side of the Alps, elongated, straight erosional scars that slope upward were assigned to a tunnel valley origin where subglacial meltwater under pressure substantially contributed to the incisions  (Dürst Stucki et al., 2010; Jordan, 2010; Preusser et al., 2010).
As many inner gorges in the Alps contain overdeepened segments (Pfiffner et al., 1997), a subglacial meltwater origin cannot be completely excluded.
19.09.2012 20:38 945 5 Комментарии
 

Kirill V. Chistyakov, Dmitry A. Ganyushkin, Igor G. Moskalenko, Wolf-Christian Dullo THE GLACIER COMPLEXES OF THE MOUNTAIN MASSIFS OF THE NORTH

Группа талантливых исследователй продолжает работы в особенно суровых высокогорных условиях Южного Алтая и Западной Тувы,Chistyak исследования,  которые многие десятилетия вёл их учитель, руководитель, 10 лет назад ушедший от нас, Президент РГО профессор Юрий Петрович Селиверстов. Коллектив кафедры физической и эволюционной географии, которую принял после Ю.П. Селиверстова, возглавил его ученик, многолетний вице-президент Русского географического общества, профессор К.В. Чистяков (на фото справа). Полевой отряд этой кафедры работал в поле и в этом, сложном в погодном отношении, году. Примечательно, что в отряде на равных принимали участие и седые доценты, и совсем юные студенты (наша группа случайно встретила эту экспедицию в Курае 13 июля 2012 года).
No.02 [v. 04] 2011. PP. 4-23
GEOGRAPHY ENVIRONMENT SUSTAINABILITY

Kirill V. Chistyakov1, Dmitry A. Ganyushkin2*, Igor G. Moskalenko3,Wolf-Christian Dullo4

Faculty of Geography and Geoecology, St. Petersburg State University,St. Petersburg 199178, 10 line Vasilievsky Ostrov, 33/35, tel. 8 911 2180499,e-mail: Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript ;2*Faculty of Geography and Geoecology, St. Petersburg State University,St. Petersburg 199178, 10 line Vasilievsky Ostrov, 33/35, tel. 8 921 3314598,e-mail: Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript (Corresponding author);3Faculty of Geography and Geoecology, St. Petersburg State University,St. Petersburg 199178, 10 line Vasilievsky Ostrov, 33/35, tel. 8 921 5882929;4GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, Germany, 24148 Kiel,Wischhofstr. 1–3, tel.: +49 431 6002215, +49 171) 7355865,e-mail: cdullo@ifm-geomap

THE GLACIER COMPLEXES OF THE MOUNTAIN MASSIFSOF THE NORTH<WEST OF INNER ASIA AND THEIR DYNAMICS
Kirill V. Chistyakov, Dmitry A. Ganyushkin, Igor G. Moskalenko, Wolf-Christian Dullo 
Tabin 
Inner Asia is the presence of relatively isolated mountain massifs that are the centers of modern glaciation. Mountain glaciers of the North-West of Inner Asia has been a subject of studies of the geographers of St. Petersburg State University for several decades. The first researcher of the glaciation of Western Tuva since 1964 was President of the Russian Geographical Society, Professor Yu. P. Seliverstov (1929– 2002). The study of the glaciers includes monitoring of their current state in order to obtain information about the area, length, morphology, and the altitudinal glaciological levels, delineation and surveying of glaciers edges, and meteorological and balance observations. The main glaciological work is associated with the massifs Mongun-Taiga, Tavan-Boghd-Ola, Turgeni-Nuru, and Harhira- Nuru (Fig. 1).
The glaciers of these massifs exist in arid and sharp continental climatic conditions. Annual rainfall in the highlands is 250– 400 mm with about 35–50% in the summer. The glaciers exist due to low temperatures (at an altitude of 3200 m, the average summer temperatures range from 2° to 4°C) and high concentration of snow on the downwind north-eastern slopes. The coefficient of snowdrift and avalanche sediment concentration on glaciers is between 2 and 3 with 6 to 8 at the cirque glaciers. These values are close to the ratio of the glaciers of the Severnaya Zemlya archipelago. Low energy of the glaciation  of the North-West of Inner Asia determines its response to significant changes in the  mass balance.
 

Mid-late Holocene environmental history of Kulunda, southern West Siberia: vegetation, climate and humans

Mid-late Holocene environmental history of Kulunda, southern West Siberia:vegetation, climate and humans

Natalia Rudaya a,*, Larisa Nazarova b,d, Danis Nourgaliev b, Olga Palagushkina b, Dmitry Papin c, Larisa Frolova b 
a Institute of Archaeology and Ethnography SB RAS, Ak. Lavrentieva 17, 630090 Novosibirsk, Russia
b Kazan Federal University, Kremlevskaya St., 18, 420008 Kazan, Russia
c Altai State University, Lenina Av., 61, 656049 Barnaul, Russia
d Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Telegrafenberg A43, 14473 Potsdam, Germany
A b s t r a c t
An environmental reconstruction of mid-late Holocene vegetation, climate and lake dynamics was inferred fromKulun pollen and diatom records of Lake Big Yarovoe in Kulunda, southern West Siberia. The reconstruction suggests a general prevalence of steppe during the last 4.4 ka. Under a relatively warm and dry climate, open semi-desert and dry steppes with patchy birch forest spread between 4.4 and 3.75 ka BP. The largest development of conifer forest started in Kulunda after 3.75 ka BP. The onset of theLate Holocene is characterised by the dominance of steppe with birch and pine forests in the lowlands and river valleys. After AD 1860, oen steppe and semi-desert vegetation with fragmentary birch forest have been dominant in Kulunda, along with a sharp reduction of conifers. These results are in agreement with the general pattern of the Holocene environmental history of the surrounding areas, including the Baraba forest-steppe, Kazakh Upland and Altai Mountains. The penetration of coniferous forest into theKulunda steppe after 3.75 ka BP was related to its geographical location northwest of the Altai Mountains.
The economic activities of the ancient population of Kulunda depended on the environmental changes during the Holocene.
2012 Elsevier Ltd. All rights reserved.
06.09.2012 10:28 1281 31 Комментарии
 

Holocene glacier fluctuations and climate changes in the southeastern part of the Russian Altai (South Siberia) based on a radiocarbon chronology A.R. Agatova , A.N. Nazarov, R.K. Nepop, H. Rodnight

Статья очень активно работающей интернациональной группы исследователей. Работа насыщена новым фактическим материалом, приведены данные полевых и камеральных исследований авторов последних лет. Представляю эту работу о колебаниях голоценовых ледников Алтая на сайте. Такие статьи часто труднодоступны российским ученым, особенно тем, кто работает в небольших городах и в экспедиционных поселках. Подобные статьи, откровенно говоря, вообще - редкость и в т.н. рейтинговых журналах. Мусора, мелкотемья полно и в западных изданиях, хороших работ не так уж и много. Предлагаемая - одна из них. Потому, статья, несомненно будет востребована. 

 

Holocene glacier fluctuations and climate changes in the southeastern part of the 
Russian Altai (South Siberia) based on a radiocarbon chronology

A.R. Agatova a,*, A.N. Nazarov b, R.K. Nepop a, H. Rodnight c

a Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia

b Siberian Federal University, Krasnoyarsk, Russia

c Institute for Geology and Paleontology, University of Innsbruck, Austria

Corresponding author. Tel.: +7 383 3304080; fax: þ7 383 3332792.
E-mail address: Этот e-mail адрес защищен от спам-ботов, для его просмотра у Вас должен быть включен Javascript (A.R. Agatova).

A b s t r a c t

This study investigates glacier dynamic and climatic variations in the southeastern part of the Russian 
Altai (SE Altai) during the last 7000 years. Recent glacier retreats and ice melting in moraines has led to 
exhumation of organic material allowing the possibility of radiocarbon dating. We report here 57 new 
radiocarbon dates from wood remains buried by moraines and from proglacial forefields, from peat 
layers and lacustrine sediments that cover moraines, from dead trees at the upper tree limit, and from 
rock glaciers on trough slopes from six glacial valleys in the North Chuya Range, SE Altai. Such 
a numerous dataset for the vast but unified in neotectonic and climatic conditions area is presented for 
the first time the history of research in the Altai. 
Together with 62 previously published radiocarbon ages, mainly of fossil soils and peat layers in the 
foot of the ranges in SE Altai, they form the basis for understanding the relative magnitudes and timing of 
the most important glacial and climatic events of SE Altai. New data refute the traditional concept of the 
Russian Altai Holocene glaciations as a consecutive retreat of the late Wuerm glaciers and argue their 
complete degradation at the head of trough valleys at least 7000 cal. years BP. Moraine complexes of 
three Holocene glacial stages are morphologically expressed in trough valleys of the North Chuya range.

They correlate with three identified periods of glacial advances: from 4900 to 4200 cal. years BP (Akkem 
stage), from 2300 to 1700 cal. years BP (Historical stage) and in the 13the19th centuries (Little Ice Age 
(LIA) or Aktru stage). The coincident extremes of lowering temperature and increasing precipitation 
during the Akkem stage led to abrupt glacier advances and forming of the most remote moraine 
complexes downstream in the valleys. Following glacier advances had distinctly smaller magnitudes. In 
addition to the radiocarbon data, the time limits of the Historical stage were defined more precisely using 
dendrochronological and archaeological data from Scythian burials of Pazyryk culture in SE Altai. 
Repeated forest regrowth in the presently glaciatiated area indicates significant retreat or even complete 
glacier degradation during interstage warming. The decreases of glacier length in the following stages 
argues for intensification of aridity in the SE Altai during the second half of the Holocene. The thermal 
minimum in the middle of 19th century, the greatest in the last millennium, did not positively influence 
the mass balance of glaciers, which also supports this conclusion.



© 2012 Elsevier Ltd. All rights reserved
02.06.2012 21:05 3255 383 Комментарии
 
Еще статьи...
<< Первая < Предыдущая 1 2 3 4 5 6 7 8 9 Следующая > Последняя >>

Страница 2 из 9
Прощай мой дом

JavaScript is disabled!
To display this content, you need a JavaScript capable browser.

О проекте

Всё об удивительном и загадочном мире льда и ледников, ландшафтов и людей и их жизни. Всё о планете Земля и о других планетах.

Интересы: снег, вода, горы, лед, катастрофы, все, климат, рельеф, ледники, приледниковые озёра, геоморфология, гляциология, новые теории и проекты в гляциологии, геологии и геоморфологии, а также качественная музыка и всё интересное и в науке, и в экспедициях, что сочтут для себя важным участники проекта, в природе и в жизни.. ....в общем всё.

Наши новости
Текущая информация для студентов
Ключевые слова
Авторизация



logotipЧитателям, слушателям и просто прохожим: сайт и все материалы, опубликованные на нём -  интеллектуальная собственность владельца сайта, и/или авторов соответствующих материалов. Ссылки на сайт, а также ссылки на авторов публикаций,

trudovaslava.info

(и фотографий, разумеется, тоже) обязательны. Соответствующие законы РФ и других стран известны, лицензии - на месте. Воруют, конечно, и не взирая на копирайты, но мы создали сайт для порядочных людей. Не хочется об этом напоминать, но факт любой недобросовестной ссылки-цитирования или пересказа, во- первых, будет предан широчайшей огласке через сеть всеми популярными научными каналами. А далее, возможно, последует и во-вторых..... Спасибо.

Контакты: ran@mail.tomsknet.ru