W sprawie poglądów na genezę skałek w masywie granitowym w Dartmoor (Anglia)

Abstract

There are wide, semispherical, hills in the south-west England. The highest, Dartmoor (621 m. asl.) is built of granites which, as a huge batholit, was formed during the Hercynian orogene. Numerous rocky forms, which can be observed on wide plateaus, slopes and lower ridges are commonly known. They make different forms: towers, crags, pillars, stacks etc. Such forms are of different origin and they can be observed in different dimatic zones. Such forms in England were described by D.L. Linton (1955), J. Palmer, R. Neilson (1962). The theory of weathering origin of granitic rocks in Dartmoor was presented by D.L. Linton (1955) and it may be called as a dassical one. He connected development of rocks, called "tors", with deep weathering during the Tertiary and, the during the Quaternary, the thick weathered cover was carried away. The cross - sections (fig, 3, 4) show that there are solifluctional covers on slopes and rocks are in different stages of development. Some of them are typical, periglacial rocky fields and there are well preserved fragments of cryoplanation surfaces, with frost diffs, on slopes. These forms are not only Tertiary horsts uncovered from the weathered material during periglacial processes but they were also modelled by frost processes. To Lintons theory abont 2 phase origin (weathering and disclosure) the third phase, of modelling in periglacial processes, should be added. Disclosure could take place in different ways: by dissecting and planation in moderately humid climate (interglacials and Holocene), by cryoplanation and solifluction in periglacial climate. Washing aut and mechanical suffosion play contemporarily an important role.