Paweł Kroh

Abstract

The origins of talus slopes origin are connected with both weathering and the transport of rock grain. Slope formation in these landforms reflects many climatological, morphological and geological factors, with grain-size dsitributions characterising the surface of talus slopes able to offer some information on means of transport and deposition mechanisms. The main aim of the work detailed here has thus been to present disparate processes of talus-slope formation in two mountain locations – in zones of Arctic periglacial and semi-arid Continental periglacial climate.

Results for the two study sites are presented. The first is located on Spitsbergen, on its SW coast, near the Polish Polar Station. The climate there is Arctic and periglacial, the average annual temperature being -3.2°C and mean annual precipitation 494.6 mm. The slope here has a western exposure, with the rock face and talus slope built of gneiss and crystalline shales with marble intrusions. There is permafrost as well as an active layer noted at this study site. The second study site is in the Fann Mountains, which form part of the Pamiro-Allay Massif in Tajikistan. Annual temperature there is of about 1‑2°C (nearby Stations reporting 6.6°C at Iskanderkul at 2204 m a.s.l., and 0.7°C at the Shahristan Pass at 3143 m a.s.l.), while annual precipitation is some 300 mm. The slope has a southerly exposure, while the rock material is a massive Devonian limestone. No permafrost is to be observed in this area.

Similar methods were used at both study sites, as Profiles featuring four measurement points were designated. At these points, 0.5 x 0.5 m squares were marked, and perpendicular photographs taken at a distance of 1.5 m. Composition as regards grain-size was analysed using BaseGRAIN software.

Structure as regards grain-size is seen to differ strongly between the two talus slopes. On Spitsbergen, grain-size is steadily greater at higher points up the slope. Close to the rock cliff it is boulders and large stones that dominate, while on the lowest parts it is grain-sizes classifiable as sand and silt that account for the greater part of the deposit. In the semi-arid climate of Asia, grain size proves to be sorted in the opposite way, with the largest debris fragments characterising the lowest parts of the talus slope. Close to the rock cliff, at the highest elevations, grains are of the smallest size, and are mostly assignable to the gravel and small stone categories. It is at the foot of the slope that rock sizes are the largest.

The most important factor underpinning the disparate formation of these two talus slopes is permafrost. Talus-slope structure in the Arctic reflects mutually-interrelated processes. Those concerning gravity related to the melting of permafrost with larger stones dislocated to the surface. Additionally, melting of the active layer and the presence of a roof of permafrost allows flowing water deriving from rain and snowmelt to bring about the intensive transport of particles of sand and silt sizes down to the lower part of the slope.

In the periglacial high-mountain conditions noted in Asia, the lack of permafrost combined with the low level of precipitation to minimise the factor of water here. The dominance of gravitational processes in the sorting material ensures that heaviest rock fragments are transported for longer, and end up being deposited in lower positions on the slope.

Keywords: talus slopes, grain size, Spitsbergen, Fann Mountains, periglacial zone

Piotr Dolnicki [piotr.dolnicki@up.krakow.pl], Uniwersytet Pedagogiczny, Instytut Geografii
Paweł Kroh [pawel.kroh@up.krakow.pl], Uniwersytet Pedagogiczny, Instytut Geografii

Citation

APA: Dolnicki, P., & Kroh, P. (2022). Skład frakcjonalny stożków gruzowych w kontekście zróżnicowanego klimatu peryglacjalnych stoków górskich (na przykładzie Spitsbergenu i środkowej Azji). Przegląd Geograficzny, 94(4), 437-450. https://doi.org/10.7163/PrzG.2022.4.2
MLA: Dolnicki, Piotr, and Kroh, Paweł. "Skład frakcjonalny stożków gruzowych w kontekście zróżnicowanego klimatu peryglacjalnych stoków górskich (na przykładzie Spitsbergenu i środkowej Azji)". Przegląd Geograficzny, vol. 94, no. 4, 2022, pp. 437-450. https://doi.org/10.7163/PrzG.2022.4.2
Chicago: Dolnicki, Piotr, and Kroh, Paweł. "Skład frakcjonalny stożków gruzowych w kontekście zróżnicowanego klimatu peryglacjalnych stoków górskich (na przykładzie Spitsbergenu i środkowej Azji)". Przegląd Geograficzny 94, no. 4 (2022): 437-450. https://doi.org/10.7163/PrzG.2022.4.2
Harvard: Dolnicki, P., & Kroh, P. 2022. "Skład frakcjonalny stożków gruzowych w kontekście zróżnicowanego klimatu peryglacjalnych stoków górskich (na przykładzie Spitsbergenu i środkowej Azji)". Przegląd Geograficzny, vol. 94, no. 4, pp. 437-450. https://doi.org/10.7163/PrzG.2022.4.2