Skład frakcjonalny stożków gruzowych w kontekście zróżnicowanego klimatu peryglacjalnych stoków górskich (na przykładzie Spitsbergenu i środkowej Azji) = Grain-Size Composition on Talus Slopes in the context of disparate climatic conditions of periglacial mountain zones (exemplified by Spitsbergen and Central Asia)

Abstract

Talus slopes origin is connected both with weathering and transport of the rock grain. The formation of these landforms is an effect of many climatological, morphological and geological factors. The grain size of the surface of the talus slope brings some information about the way of transport and deposition mechanisms. The main aim of the paper is to present different talus slope formation in two mountain locations - in arctic periglacial and semi-arid continental periglacial climate zones. Results from two study sites are presented. The first one was located on Spitsbergen Island, on its SW coast, near Polish Polar Station. The climate is arctic and periglacial, the average annual temperature is -3,2°C, annual precipitation is 494,6 mm. The slope is exposed to the west, rock face and talus slope are built with gneiss, crystalline shales with marbles intrusions. There is permafrost as well as an active layer noted on this study site. The second study site is in the Fann Mountains, part of Pamiro-Alay massive in Tajikistan. The annual temperature is about 1-2°C (meteo stations nearby: 6,6°C Iskanderkul 2204 m.a.s.l., 0,7°C Shahristan Pass 3143 m.a.s.l.), annual precipitation is about 300 mm. Slope is exposed to the south, rock material is a Devonian massive limestone. No permafrost was observed in this area. On both study sites, similar methods were used. Profiles with four measuring points were designated. On these points, 0,5 x 0,5 m square were marked and perpendicular photographs from a 1,5 m distance were made. Grain sizes were analyzed in BaseGRAIN software. In Asian periglacial high-mountain conditions lack of permafrost and low precipitation causes, that there is no factor of water. Domination of gravitational processes is sorting material when the heaviest rock fragments are transported longer and are deposited on lower positions on the slope.