The Late Glacial and Early Holocene palaeoenvironmental changes recorded in landslide peat bog (landslide fen) deposits in the northern parts of the Polish Outer Carpathians (Southern Poland)

In the northern part of the Polish Outer Carpathians, the Beskid Makowski Mts., four landslides formed during the Late Glacial have been identified so far. The landslide peat bogs  formed within landslide depressions represent specific type of minerogenic mires filled down by organic-minerogenic deposit. Within the depositional sequences of these peats, palaeoenvironmental changes of the Late Glacial and the Holocene are recorded. The oldest of the studied fens started to form in the Oldest Dryas, the younger ones – in the Bolling  (two peat bogs), Older Dryas and the Younger Dryas (Margielewski, 2003; Margielewski, 2006). In the sediments of the four landslide fens of the thickness varying from 4.5 m to 1.5 m, several logs were cored using the Instorf sampler. The laboratory study of the logs, reaching the deepest parts of the fens, included: palynological analysis, peat analysis (microscopic examination of organic deposits), grain-size (aerometric) analysis and content of minerogenic material (loss on ignition) analysis for 2.5 cm long intervals. Over 50 radiocarbon datings made in the studied logs (7-14 ones for each log), enable to date the horizons of lithological and pollen change

Palaeoenvironmental changes of Orawa-Nowy Targ Basin in the Late Glacial and Holocene recorded in sediments of Grel raised bog

The Grel raised peat bog is located in the Ludźmierz village vicinity in the Orawa-Nowy Targ Basin. This raised bog, has heavily degraded peat dome covered with numerous post excavation pits which are the results of peat extraction for local purposes. Peat bog is overgrown with birch and pine forests and typical vegetation for raised bog. First palynological study of the peat depositional sequence was performed by Koperowa (1962). The beginning of the peat bog formation was then attributed to the Oldest Dryas. Consequently the Grel is the oldest peat bog in the peatland of the Orawa-Nowy Targ Basi

Gravitationally induced non-karst caves: Tectonic and morphological constrains, classification, and dating; Polish Flysch Carpathians case study

Analysis of non-karst caves in the Flysch Carpathians confirms the connection between the tectonic evolution of this orogen and the initial phase of cave formation. The compressional-extensional regime during the tectonic stages of the evolution of the Carpathians is the foundation of subsequent gravitational stresses within the slopes, which brought about various deformations of rock massifs, producing diverse types of subsurface cavities – caves. Therefore, most caves that occur in the Carpathians, represent forms of the opening and widening of joints and stress zones originated much earlier. Classification based on the chronology and mechanisms of these caves is proposed. A chronological approach requires understanding the relationship of cave development to the stages of slope evolution and enables the construction of the morphogenetic classification, whereas consideration of the processes affecting the rock massif structure allows geomechanic classification. Using the morphogenetic criterion, three categories of caves can be distinguished: initial caves developed during slope deformations preceding the principal slope failures (landslides), subsequent caves formed during the main slope failure, and intermediate caves related to the main scarp formation. On the basis of the geomechanic criterion the following types of caves can be distinguished: dilational caves formed due to tensional fractures widening, dilatancy caves formed due to the fissure macrodilatancy, and boulder caves, which represent chaotic cavities. In order to illustrate this classification, type localities of the various cave types are presented. The radiocarbon dating of secondary formations (speleothems) occurring in the caves indicate that they initially formed in the Weichselian (Upper Plenivistulian), Late Glacial and Early Holocene and underwent various transformations

Crevice-type caves as initial forms of rock landslide development in the Flysch Carpathians

Crevice-type caves, formed along joints, are very common in the Polish Flysch Carpathians (more than 600 have been recorded). The caves represent accessible parts of the widened cracks, which are basic, initial forms of development of deep-seated rock landslides. Structural features of four selected caves (situated in different parts of the Carpathians) were studied in order to determine relations between joint systems and landslide formation. The studies prove that the main rock scarps often represent effects of earlier propagation of the cracks (=cutting surfaces) due to loading and unloading shearing stress. The cracks are structural forms developed along joints or faults. The cutting surfaces represented by cracks (caves) develop a long time before the main gravitational mass movements, whereas the sliding surfaces (shearing zones) are formed or significantly modified ad hoc during the gravitational transport of rock masses. Occurrence of the deep initial cracks causes modification of shape of the sliding surfaces, which are noncircular. The mountain slopes cut by many cracks are permanently developed. Thus, the periodic increase of activity of external factors (floods, downpours, earthquakes, etc.) leads to common formation of the landslides earlier prepared by crack development. This model of slope evolution enables us to interpret the occurrence of the landslide phases (in the Holocene) during which increasing of frequency of the landslides is observed

Recent landform evolution in the Polish Carpathians

The key drivers of relief transformation in the Polish Carpathians (the best studied region of the Carpathians) have been local downpours, continuous rainfalls, and rapid snowmelt. Threshold values are quickly exceeded during such events and powerful morphological processes are initiated. However, due to human activities, geomorphic processes are often accelerated and intensified with serious consequences. Thus, increased human impact is a key factor in the recent geomorphic evolution of the Polish Carpathians. Over the last two centuries deforestation, intensive agriculture, mining, housing developments on slopes, channelization of streams, and construction of reservoirs all have contributed to changes in the rate of the particular geomorphic processes. The intensity of sheet erosion depends on vegetation cover, land use, and cultivation techniques (terracing, contour tillage, crop rotation, etc.). Slopes bearing poorly constructed infrastructure have become susceptible to mass movements. At higher elevations debris flows, dirty avalanches, and extreme floods are crucial in slope evolution. Over the last 20 years the ratio of agricultural land and the rate of sheet erosion and deflation have decreased, while gully erosion on slopes and the incision of river channels have intensified and the reactivation of shallow landslides has become more common. Increasingly frequent extreme weather events may reverse the stabilizing trend of landform evolution

Dendrogeomorphological analysis of the Sawicki Landslide in the Beskid Niski Mountains (S Poland)

We applied dendrochronological analysis to study an extensive (~2.5 km long) complex-type landslide in the Beskid Niski Mountains (Polish Flysch Carpathians), which was rejuvenated in historical time (the earliest transformation occurred in 1913). We used three complementary methods (dating of eccentricity of annual growth rings, eccentricity indices, and analysis of reaction wood), based on seven species of deciduous and coniferous trees. A total of 204 trees were sampled and 408 cores collected using a Pressler increment borer. Based on the dendrochronological analysis, the activity of various parts of the landslide in the past century is presented, which appears to have been diverse and influenced mostly by precipitation. The upper part of the landslide was active from the 1920s until the 1940s. In the middle section of the landslide, intensifications of gravitational movement were repeatedly recorded after intense rainfalls throughout the entirety of the last century. The highest landslide activity was dendrochronologically detected in the 1980s and 1990s. Increasing landslide activity during so-called “dry years” may have been related to quick drying of the bedrock, resulting in changes in rock strength parameters. Our results indicate significant susceptibility of this particular slope-valley geosystem in response to even slight hydrogeological changes (including dryness), which can trigger ground movement