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1

Effect of lithological and geotechnical characteristics on the generation of debris flows in Matmata, southeastern Tunisia

Bensalem Hassen, Amamria Soulef, Bensalem Mohamed Sadok, Meisina Claudia, Hamdi Noureddine

Studia Quaternaria

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2024

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Vol. 41, Nr 1

23--35

EN

The Matmata region, located in the south of Gabès (Tunisia), experienced significant damage during the floods of the Beni zelten wadi on November 11, 2017. These floods, exacerbated by the steep slopes and underlying soil conditions, led to the occurrence of debris flows, posing a threat to road infrastructure. The generation of debris flows is closely linked to intense rainfall events that surpass the soil capacity to retain water. To gain insights into the behaviour of the soil samples, various characteristics were analysed, including texture, clay mineralogy, grain size distribution, and Atterberg limits. The results showed that the mean liquid limit values ranged from 38% to 62%, while the mean plasticity index of the materials in the landslide-prone areas varied from 18% to 27.9%. These findings indicate presence of clay formations and highlight a significance of the increased soil clay content as contributing factors to landslide development. The X-ray Diffraction analysis revealed that gypsum, quartz, phyllosilicate and calcite minerals were the most abundant minerals identified in the soil samples. This work shows the importance of clay mineral and geotechnical parameters of the soils in the occurrence of landslides and predicting debris flows occurrences in the Matmata region.

2

A study of control scheme of debris flows and geological disasters in the Shiwei river basin

Wu Hanhui

Archives of Civil Engineering

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2024

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Vol. 70, nr 1

509--526

EN

The basic characteristics of debris flows in the Shiwei river basin are summarized through the field investigation on debris flows in the Shiwei river basin and analysis on formation conditions of debris flows from three aspects, i.e. geological environment, geological structure and neotectonic movement, as well as seismic action. Based on this, the stability of landslide in the Shiwei river basin is analyzed and calculated, and the stability coefficient of landslide is obtained. The debris flows in the Shiwei river basin will directly damage and threaten the county town, while other geological disasters such as landslide, collapse, slope sliding & collapse and potentially unstable slopes will indirectly damage and threaten the county town. The landslide form is clear, and the landslide stability calculation shows that the landslide body is generally stable – basically stable, but partially unstable – less stable. The “blocking + discharging” comprehensive control scheme is proposed according to the formation conditions and development characteristics of debris flows in the Shiwei river basin, and the study findings can be used as a reference for similar projects.

3

Conditions and morphogenetic role of the 2018 and 2021 debris flows in Starorobociański Cirque, Western Tatra Mts.

Siemek Dawid, Gorczyca Elżbieta

Landform Analysis

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2023

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Vol. 42

63--73

EN

In this study we used geomorphologic mapping, precipitation analysis and archival photomaps to study debris flows in the Starorobociański Cirque, which were renewed in 2018 and 2021. Debris flow in 2021 was most likely the largest single flow recorded in the Polish Western Tatras in the twenty first century. It reached a length of about 870 m and it covered an area of 0.62 to 0.65 ha. We set July 14, 2021, as the date of debris flow initiation and 52.1 mm·d−1 as its threshold value. This is one of the lowest values provided in the literature for such flows in the Western Tatra Mts. On the contrary, debris flow which occurred July 18, 2018 was linked to threshold value of 150.5 mm·d−1. On the basis of former debris flow occurrence as well as precipitation analysis we interpret the appearance of debris flow in 2021 as an effect of short and intense rainfall.

4

Numerical study of debris flows around bridge piers

Thai Thi Kim Chi

Roads and Bridges - Drogi i Mosty

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2022

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Vol. 21, no. 4

331--342

EN

Landslide is a natural hazard that has crucial direct impact on the socio-economic system. Among various types of landslides, debris flows are a major threat to transportation structures such as bridges in mountainous areas. Vulnerability analysis of bridges that are exposed to debris flows is an important part of risk assessment and management. In the presented study, the characteristics of debris flows around bridge piers are investigated numerically for different boundary conditions using ANSYS FLUENT software. The non-Newtonian power-law model was used to model the debris flow. Drag coefficient was also determined to quantify the vulnerability of bridge piers to debris flows with different velocities and Reynolds numbers.

PL

Osuwiska stanowią naturalne zagrożenie mające bezpośredni wpływ na środowisko, warunki społeczne i ekonomiczne. Spośród różnych typów osuwisk, spływy rumoszowe stanowią poważne zagrożenie dla konstrukcji drogowych, takich jak mosty w terenach górzystych. Analiza podatności mostów na uszkodzenia spowodowane spływem rumoszowym jest ważnym elementem oceny ryzyka i zarządzania nimi. W niniejszej pracy zbadano charakterystyki spływów rumoszowych w bezpośrednim sąsiedztwie filarów mostu, wykorzystując symulacje numeryczne, dla różnych warunków brzegowych, przy zastosowaniu oprogramowania ANSYS FLUENT. Do modelowania spływu rumoszowego użyto potęgowego modelu reologicznego cieczy nienewtonowskiej. W celu oceny ilościowej odporności filarów mostu na spływy rumoszowe charakteryzujące się różnymi prędkościami i liczbami Reynoldsa, w artykule wyznaczono także współczynnik oporu przepływu osuwiska rumoszowego.

5

Private solutions to design an innovative engineering structure for efficient debris flow control

Gavardashvili Givi, Kukhalashvili Eduard, Iremashvili Inga

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

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2022

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Vol. 11

171--180

EN

There are hardly any sections in a debris flow channel, where flow movement, except for exceptions, would have a constant hydraulic regime and typical parameters. Therefore, in order to select regulating measures, the urgent means of assessment of the flow regime to totally cover its anomaly is needed. The solution of this question is associated with the full compatibility of laws with soil mechanics and hydraulics. Recently, the engineering problems related to debris flow, based on various considerations, have been realized by integrating the obtained differential equations. Especially important are the possibilities of a debris flow moving regime in prismatic beds described by the system of differential equations of various modifications. If rheological properties are neglected in the above equations, they are completely transformed into differential equations of non-uniform motion of Newtonian fluids. By considering the above-mentioned, the paper gives the calculation methods and practical example of designing an innovative debris flow control barrage, which was realized in the bed of the Mletis Khevi river gorge.

6

Field evidence suggests that the Palaeoproterozoic Gowganda Formation in Canada is non-glacial in origin

Molén Mats O.

Geologos

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2021

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Vol. 27, No. 2

73--91

EN

During more than a century since its original identification, the Gowganda Formation in Ontario (Canada) has gradually been reinterpreted from representing mainly subglacial tillites to secondary gravity flow and glaciomarine deposits. The main pieces of geological evidence advanced in favour of glaciation in recent articles are outsized clasts that have been interpreted as dropstones and patches of diamictites in a single small-sized area at Cobalt which is still interpreted as displaying subglacial basal tillites. The present research considers field evidence in the Gowganda Formation in the light of more recent work on gravity flows linked to tectonics. Detailed studies have demonstrated that the clasts which are interpreted to be dropstones rarely penetrate laminae and are commonly draped by sediments the appearance of which is similar to lonestones in gravity flows. The “subglacial area” at Cobalt displays evidence of tectonics and gravity flows, which can be traced from the underlying bedrock, and then further in the overlying sequence of diamictites and rhythmites. The sum of geological features displays appearances at odds with a primary glaciogenic origin, and there is no unequivocal evidence present of glaciation. The data indicate deposition by non-glaciogenic gravity flows, including cohesive debris flows for the more compact units, probably triggered by tectonic displacements.

7

Debris-flow functioning and their contribution to sedimentary budgets : the Peynin subcatchment of the Guil River (Upper Queyras, Southern French Alps)

Viel V., Fort M., Lissak C., Graff K., Carlier B., Arnaud-Fassetta G., Cossart E., Madelin M.

Landform Analysis

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2018

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Vol. 36

71--84

EN

The Peynin catchment (15 km2) is prone to catastrophic floods (June 1957 – Recurrence Interval R.I.>100 yr), June 2000 (R.I.-30 yr) with serious damages to infrastructure and buildings located at the outlet. In this paper, PIT tags tracers and Vensim modelling software are used to better assess the sediment delivery unsteadiness, and more specifically to evaluate the respective role of geomorphological processes on sediment supply during flood event. For the last 20 years, our results highlight a significant variability in sediment delivery from a tributary to another one. According to our studies, we suppose that two torrential tributaries of the Peynin river, the Peyronnelle and Three Arbres subcatchments (<2 km2, representing <15% of the Peynin catchment area) are responsible of 80% of the sediments observed at the outlet of the catchment. Several processes take a part of these sediment transfers, but the efficiency of the sediment cascade in this catchment can be explained by a strong connectivity between sediment erosion area and the main channel of the catchment. Debris and torrential flows triggered during high intensity meteorological event are actually effectively coupled in space and time and guarantee an important sediment supply able to reload the downstream part of the sediment cascade. Recent climate trends, marked by extremes, suggest consequently more damaging events to come, in a context of increasing vulnerable assets.

8

Effects of cohesive mudflow on semi-cylindrical antimud structure

Kukhalashvili E., Gavardashvili G., Kupreishvili S. H., Beraia N.

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

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2018

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Vol. 7 Nr 2

33--41

EN

Counteracting the phenomenon of debris flow is implemented in various ways. As international practice has shown, hydrotechnical constructions occupy a special place among structures regulating debris flow . Despite the large variety of constructions, each of them has a strictly defined purpose. The specifics associated with the hazards of debris flow in a given area are taken into account when selecting such a construction The work indicates the expediency of applying semicylindrical open-web constructions to regulate debris flow. The methodology of selecting the design elements is presented. A specific example of the construction calculation and graphic illustrations are presented.

PL

Przeciwdziałanie zjawisku przepływu gruzowego jest realizowane na różne sposoby. Jak pokazała praktyka międzynarodowa, konstrukcje hydrotechniczne zajmują szczególne miejsce wśród struktur regulujących przepływy gruzowe. Mimo dużej różnorodności konstrukcji każda z nich ma ściśle zaznaczony cel. Specyfika związana z niebezpieczeństwem przepływu gruzowego w danym obszarze jest brana pod uwagę przy ich doborze. W pracy wskazano celowość zastosowania półcylindrycznych konstrukcji w otwartych kanałach stosowanych w celu regulowania przepływu gruzowego. Przedstawiono metodologię doboru elementów konstrukcyjnych. Przytoczono konkretny przykład obliczeń konstrukcyjnych oraz ilustracje graficzne.

9

Protection of settlements from floods and debris flow on the example of tragedy in Tbilisi on 13-14 June of 2015

Diakonidze R., Supatashvili T., Diakonidze B., Ioseliani L., Getiashvili A., Laoshvili Z.

Meteorology Hydrology and Water Management. Research and Operational Applications

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2017

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Vol. 5, Iss. 2

31--34

EN

This article presents material about the flood on the Vere River on 13-14 June, 2015. It caused significant economic and ecological damage to the country, and there were also human victims. The reasons for the ecological disaster are evaluated and appropriate hydrological calculations have been carried out. It has been particularly established that the predictable (forecasting) maximal discharges of 0,1% value for Vere River is 520 m3/sec and not 410 m3/sec, that was calculated water conduct tunnels in the entrance of city before the Mtkvari River. The flood on the 13-14 June 2015 and the connected tragedy was caused by high intensive precipitation in the catchment basin, the activation of geodynamic processes, and also anthropogenic factors. In our opinion, a reason of disaster also was a design flaw in hydrotechnical buildings (tunnels) – they are not able to manage a water flow rate of 0,1% assurance. The paper presents the recommendations necessary for us to avoid, or at least reduce, the ecological and economic problems caused by floods and debris flow. The presented recommendations against a disaster like that which affected Tbilisi, as well as the expected environmental problems on territory with similar natural conditions, will enable us to avoid or reduce damage caused by flood and debris flow.

10

The origin of upper Precambrian diamictites, northern Norway: a case study applicable to diamictites in general

Molén M. O.

Geologos

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2017

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Vol. 23, No. 3

163--181

EN

Upper Precambrian diamictites in Varangerfjorden (northern Norway) have been examined for evidence of origin, whether glaciogenic, gravity flow or polygenetic. Studies of geomorphology, sedimentology and surface microtextures on quartz sand grains are integrated to provide multiple pieces of evidence for the geological agents responsible for the origin of the diamictites. The documented sedimentary and erosional structures, formerly interpreted in a glaciogenic context (e.g., diamict structure, pavements and striations) have been reanalysed. Field and laboratory data demonstrate that, contrary to conclusions reached in many earlier studies, the diamictites and adjacent deposits did not originate from glaciogenic processes. Evidence from macrostructures may occasionally be equivocal or can be interpreted as representing reworked, glacially derived material. Evidence from surface microtextures, from outcrops which are believed to exhibit the most unequivocal signs for glaciation, display no imprint at all of glaciogenic processes, and a multicyclical origin of the deposits can be demonstrated. The geological context implies (and no geological data contradict this) an origin by gravity flows, possibly in a submarine fan environment. This reinterpretation of the diamictites in northern Norway may imply that the palaeoclimatological hypothesis of a deep frozen earth during parts of the Neoproterozoic has to be revised.

11

Deep-sea mass-flow sediments and their exotic blocks from the Ropianka Formation (Campanian-Paleocene) in the Skole Nappe : a case from the Wola Rafałowska section (SE Poland)

Łapcik P., Kowal-Kasprzyk J., Uchman A.

Geological Quarterly

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2016

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Vol. 60, No. 2

301--316

EN

Flysch deposits of the Ropianka Formation (Wiar and Leszczyny members; Skole Nappe) at Wola Rafałowska include two different sediments that contain exotic pebbles, cobbles and boulders. The first one is a graded conglomerate that contains mostly cobbles of sandstones, gneisses, Štramberk-type limestones, volcanic rocks, pegmatites and ferruginous siltstones. The second one is a pebbly mudstone that contains clasts of sandstones, stone coal, grey mudstones, volcanic rocks, schists, limestones, marls, black mudstones, conglomerates, volcaniclastic rocks and quartz gravels that are floating within a muddy matrix. Genesis of the conglomerate is unclear because it shows features typical of debris flows (poorly sorted, matrix- to clast-supported, large amount of cobble to boulder fraction) as well as high density turbiditic currents (indistinct normal gradation, small amount of cohesive material, crushed clasts that suggest interaction between grains during transportation and at least partly turbulence during flow). The pebbly mudstone represents typical debris flow deposits (large amount of cohesive material, matrix-supported, poorly sorted, lack of grain gradation and traction structures that suggest laminar flow). Limestones occurring in both exotic-bearing sediments show different Upper Jurassic–lowest Cretaceous facies of a carbonate platform, which was involved in the source area of the Skole Basin, along with its basement. They can be interpreted as deposits of: 1) platform-margin reefs and a platform slope: a) partly silicified coral boundstone, b) microbial-coral boundstone, c) silicified sponge-microbial boundstone grading into peloidal-ooidal grainstone with bioclasts, and d) strongly silicified limestone with intraclasts and bioclasts; 2) deeper, platform slope to toe-of-slope area – bioclastic wackstone; 3) inner platform, including: a) partly silicified wackstone with peloids, small intraclasts and bioclasts, and b) microbial bindstone. Moreover, some exotic clasts are built of Albian–Cenomanian wackstone with abundant sponge spicules and planktonic foraminifers, which are interpreted as deeper shelf sediments. Taking into account the geometry of thrust sheets from the site of the exotic-bearing sediments to the edge of the Skole Nappe, along the most probable transportation path, including tectonic/erosional reduction and different variants of slope inclination, the distance of the mass flows attained at least 25–97 km from the shelf edge.

12

The spatio-temporal dynamics of the Ciprnik complex landslide, Tamar Valley, Julian Alps, Slovenia

Šmuc A., Janecka K., Lempa M., Kaczka R. J.

Studia Geomorphologica Carpatho-Balcanica

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2015

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Vol. 49

35-54

EN

Mass movements represent important processes that shape relief in Alpine areas. In this article, we present the spatio-temporal dynamics of the Ciprnik landslide (Julian Alps, NW Slovenia) and interpret its triggering and evolution. In the study area, mass movement activity is characterised by two phases: normal deposition on the fluvial fans that dominated up to 2000, and a more active phase related to the triggering of the Ciprnik complex landslide and formation of an additional debris-flow fan. The Ciprnik landslide started as a translational movement over the discontinuity plane that was mobilised into a debris-flow. The triggering and slope failure resulted from a combination of tectonics (i.e. dip-slope position of the strata, and strong fracturing), lithology (alternation of thin beds of carbonates and fine-grained clastics), and accumulation of precipitation. The debris-flow fan remains active and interfingers with adjacent active fluvial fans

13

Debris-flow activity in five adjacent gullies in a limestone mountain range

Schraml K., Oismüller M., Stoffel M., Hübl J., Kaitna R.

Geochronometria

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2015

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Vol. 42, no.1

60--66

EN

Debris-flows are infrequent geomorphic phenomena that shape steep valleys and can represent a severe hazard for human settlements and infrastructure. In this study, a debris-flow event chronology has been derived at the regional scale within the Gesäuse National Park (Styria, Austria) using dendrogeomorphic techniques. Sediment sources and deposition areas were mapped by combined field investigation and aerial photography using an Unmanned Aerial Vehicle (UAV). Through the analysis of 384 trees, a total of 47 debris-flows occurring in 19 years between AD 1903 and 2008 were identified in five adjacent gullies. Our results highlight the local variability of debris-flow activity as a result of local thunderstorms and the variable availability of sediment sources.

14

Morfologiczne skutki ulewy z 31 lipca 2010 r. w Czarnej Górze (Podhale)

Hełdak D., Lizak P.

Przegląd Geologiczny

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2014

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Vol. 62, nr 5

245--249

EN

The article presents results of two-year study that included mapping of Czarna Góra (Podhale region, Carpathians), especially in local watercourses and dirt roads after the downpour of July 31, 2010. The field research shows that sudden morphological processes were induced as a result of intense rain (debris flow, which was triggered in a road cut and many shallow and small landslides in local stream valleys). The study presents results of mapping new landforms after the downpour. Because no earlier landforms of similar origin have been found in this area, it can be concluded that the event had a unique character.

15

Olistostromes in the Miocene salt-bearing folded deposits at the front of the Ukrainian Carpathian orogen

Hnylko O.

Geological Quarterly

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2014

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Vol. 58, No. 3

381--392

EN

The origin of the olistostromes at the front of the Ukrainian Carpathian orogen is related to Miocene synsedimentary thrust movements of the Carpathian accretionary prism and to erosion of uplifted areas of the Boryslav-Pokuttya Nappe in the front of the accretionary prism. There are two olistostrome complexes. The first is the Lower Miocene Polyanytsya-Vorotyshcha Olistostrome with clasts of molasse and flysch deposits formed in a piggy-back basin on the inner part of the Boryslav-Pokuttya Nappe at the top of the accretionary wedge. This olistostrome is associated with the Sloboda Conglomerate derived from the fore-bulge at the foreland of the Boryslav-Pokuttya Nappe. The second one is the Middle Miocene Lanchyn Olistostrome with olistoliths of strongly deformed molasse deposits. These olistoliths were slid from the uplifted front of the Boryslav-Pokuttya Nappe. The Lanchyn Olistostrome was deposited at front of this nappe in a foredeep basin.

16

Human-planted alder trees as a protection against debris flows (a dendrochronological study from the Moxi Basin, Southwestern China)

Malik I., Tie Y., Owczarek P., Wistuba M., Pilorz W., Woskowicz-Ślęzak B.

Geochronometria

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2013

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Vol. 40, no. 3

208--216

EN

Large debris flows have destroyed the infrastructure and caused the death of people living in the Moxi Basin (Sichuan Province, Southwestern China). Inhabitants of the Moxi Basin live on the flat surfaces of debris-flow fans, which are also attractive for farming. During the monsoon season debris flows are being formed above the fans. Debris flows can destroy the houses of any people liv-ing within the fan surfaces. In order to prevent the adverse effects of flows, people plant alder trees (Alnus nepalensis) at the mouths of debris flow gullies running above debris flow fans. Alders are able to capture the debris transported during flow events. Trees are well adapted to surviving in con-ditions of environmental stress connected with abrupt transport and deposition of sediment from de-bris flows. Numerous wounds, tilting and bending of alder trees caused by debris flows only very rarely cause the death of trees. By dating scars and dating the time of alder tilting (through the analy-sis of annual rings), we have determined the frequency of debris flows occurring at the mouth of the Daozhao valley. In 1980-2012 within the studied debris-flow fan and the Daozhao gully, 2 large de-bris flow events occurred (1996, 2005) and some smaller events were probably recorded every 2-3 years.

17

Frequency of fast geomorphological processes in high-gradient streams: case study from the Moravskoslezské Beskydy Mts (Czech Republic) using dendrogeomorphic methods

Šilhán K.

Geochronometria

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2012

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Vol. 39, no. 2

122-132

EN

High-gradient streams are localities with the most dynamic activity of geomorphological processes in medium-high mountains. This study of the frequency of floods and debris flows in a se-lected high-gradient stream in the Moravskoslezské Beskydy Mts was based on a dendrogeomorphic approach. It makes use of the most accurate methods applied in the dating of historic geomorphologi-cal processes. Individual events were reconstructed on the basis of the dating of various growth dis-turbances displayed in 99 samples taken from 56 predominantly broad-leaved trees. As for the studied area, 26 years out of the last 113 years have been identified as years of rapid geo-morphological processes. The frequency of the processes has been high above average since the 1970s. A majority of the events can be considered as flash floods. Debris flows, which can only be observed sporadically, originate due to the reactivation of old accumulation material that subsequent-ly ends up re-accumulated on the alluvial fan at the mouth of a stream. A large number of events oc-cur in connection with extreme short-term precipitation in summer months. In addition, they are af-fected by fast snow melting in spring, which has also been proved by intra-seasonal dating of selected events.

18

Dendrochronological records of debris flow and avalanche activity in a mid-mountain forest zone (Eastern Sudetes - Central Europe)

Malik I., Owczarek P.

Geochronometria

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2009

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Vol. 34

57-66

EN

Dendrochronological methods were used to determine the frequency of debris flow/avalanche events in a forest zone. A debris flow and avalanche track located in the Eastern Sudetes Mountains (Central Europe) was analysed. The length of the youngest debris flow/avalanche track is about 750 m. Three distinct sections of the debris flow can be identified along the longitudinal section: niche, gully and tongue. The dendrochronological study shows that trees started growing on the margins of the debris flow between 1908 and 1963. Hence, debris flow and/or avalanche events occurred on this slope at the turn of the 19th and 20th centuries. All trees collected from the tongue started growing between 1935 and 1964. However, a large debris flow event took place several years before, most probably during an extraordinary rainfall in June 1921. Following this event, several relatively large debris flows have occurred during the growing season, the strongest dendrochronologically confirmed events occurring in 1968, 1971-1972, 1991, 1997 and probably in 1977. Spring debris flow events induced by snow melt and/or avalanches have occurred in 1994 and 2004. The results suggest that with favourable geological conditions, debris flows can occur very frequently within entirely forested slopes.

19

Selenite-gypsum microbialite facies and sedimentary evolution of the Badenian evaporite basin of the northern Carpathian Foredeep

Bąbel M.

Acta Geologica Polonica

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2005

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Vol. 55, no. 2

187-210

EN

Facies analysis was applied to the six main facies of the Badenian (Middle Miocene) gypsum deposits exposed along the margin of the Carpathian Foredeep basin, from Moldova to the Czech Republic. These facies, recognised within primary selenite and fine-grained gypsum deposits, are: (i) selenites with vertical crystals; (ii) selenites with horizontal crystals; (iii) selenite debris flow facies; (iv) selenite debris facies; (v) gypsum microbialite facies; and (vi) alabastrine facies. The facies represent various environments (from shallow-brine to subaerial) of a giant salina-type basin without open-water connections with the sea and showing evaporite drawdown. Integration of facies analysis and event stratigraphic studies in the gypsum basin allowed reconstruction of its sedimentary history.The architecture of the gypsum facies suggests that the margin of the basin was occupied by a system of variable perennial saline pans (dominated by selenite deposition) and evaporite shoals (dominated by gypsum microbialite deposition). The basin was infilled with evaporite deposits by aggradation. After initial evaporite drawdown, the northern margin of the basin evolved from a large perennial saline pan (or system of pans) into an evaporite shoal and then back again into a perennial pan, whereas the east area of the basin was a vast evaporite shoal dominated by gypsum microbialites. Separate selenite pans of oligotrophic-type developed both at the periphery and in the interior of this shoal. Later, predominantly clastic gypsum deposition developed throughout the basin margin, presumably due to a drastic change in the chemistry and salinity of the brine. Evaporite deposition was arrested by a flood of marine waters and rapid deepening.

20

Large-scale erosional channels in the Lower Cambrian sandstones, Gieraszowice environs (Kielce Block, Holy Cross Mts.)

Mizerski W., Orłowski S., Przybycin A., Skurek-Skurczyńska K.

Kwartalnik Geologiczny

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1999

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Vol. 43, Nr 3

353-364

EN

Unique erosional channels of meridional strike have been recognized in the Lower Cambrian sandstones (Ociesęki Sandstone Formation) at Gieraszowice village within the Klimontów Anticlinorium (Kielce Block). These channels have been interpreted as "strom-cut cross-shelf channels" related to the undertow induced by strong storm waves (waves generated by a series of submarine seismic shocks) during deposition of the Cambrian sediments within a shelf zone. It is highly probable that earthquakes occurring in short time intervals generated the current which eroded the channels. After the deepest channel had been formed the earthquakes led to a sliding of partly consolidated sediments onto is floor.

PL

W okolicach Gieraszowic w antyklinorium klimontowskim (blok kielecki), w formacji piaskowców z Ociesęk, udokumentowanej tu trylobitami i śladami organicznymi, stwierdzono unikatowe rynny erozyjne o rozciągłości południkowej. Warstwy osadów wypełniających rynny są nachylone skośnie do powierzchni uławicenia, w której są wycięte, i dochodzą pod kątem około 40° do powierzchni rozdzielającej sekwencję dolną, w której wycięte są rynny, z przykrywającą ją sekwencją górną. Na spągowych powierzchniach warstw wypełniających rynny stwierdzono ślady organiczne. Na podstawie badań płytek cienkich pobranych z różnych miejsc odsłonięcia, a także na podstawie obserwacji terenowych, rynny te zinterpretowano jako utworzone w wyniku działania powrotnego prądu przydennego lub rozrywającego powstałego na skutek silnego falowania sztormowego (falowania wywołanego serią podmorskich wstrząsów tektonicznych) w trakcie sedymentacji utworów kambryjskich w strefie szelfu. Jest wielce prawdopodobne, iż przyczyną powstania prądu, który wyerodował rynny, była seria wstrząsów tektonicznych, występujących w krótkich odstępach czasu, powodujących: - spiętrzenie wód w strefie brzegu i powstanie powrotnego prądu przydennego lub rozrywającego o tak dużej energii, że wyerodował na powierzchni dna rynny o głębokości dochodzącej do 5m i przebiegu prostopadłym do linii brzegowej; omawiane formy można prawdopodobnie zaliczyć do storni-cut cross-shelf channels (W. L. Duke i in.,1991); - naruszenie stateczności osadów w sąsiedztwie najgłębszej rynny, powodujące szybki zsuw materiału częściowo skonsolidowanego na dno rynny i jej wypełnienie oraz wzburzenie chmury osadu, która opadając zapełniła pozostałe zagłębienia dna; zsuw ten odbył się ku wschodowi z obszaru na W od rynny; - niewielką rotację bloku dna morskiego, po której, po wypełnieniu rynien, sedymentacja wróciła w zasadzie do pierwotnego planu sprawiając jednak, że osady sekwencji górnej mają nieco inne położenie warstw w porównaniu do sekwencji dolnej, w której wyerodowane są rynny. Po wypełnieniu rynien zbiornik nieznacznie się pogłębił i kontynuowała się sedymentacja analogicznych utworów z podobnym zespołem śladów organicznych, do zs