Age and Origin of Blockfields on Scottish Mountains

Autor:	Colin K. Ballantyne, Charles Hopkinson
Rok vydání:	2013
Předmět:	Frost weathering Geography Planning and Development Schist Geochemistry Weathering engineering.material Silt Blockfield Clastic rock Illite engineering Parent rock Geology Earth-Surface Processes
Zdroj:	Scottish Geographical Journal. 130:116-141
ISSN:	1751-665X 1470-2541
Popis:	Numerous researchers have proposed that blockfields on mid-latitude plateaux are frost-modified relicts formed initially by chemical weathering under warm, humid pre-Quaternary (Neogene) conditions. Others contend that they formed mainly by frost action during the Quaternary. We test these competing hypotheses for blockfields on three mountains in NW Scotland: a matrix-supported diamict blockfield (sandstone), clast-supported diamict blockfield (quartzite) and an openwork blockfield (schist). Clay concentrations in the fine fraction are low (0–6.8%) and both clay:silt ratios and secondary clay minerals (illite, kaolinite and gibbsite) are consistent with prolonged chemical weathering under periglacial conditions. There is negligible depletion of labile elements in the fine fraction relative to the parent rock. Conversely, evidence for surface and near-surface granular disaggregation, an increase in clast angularity with depth, dominantly angular sand grains, in situ detached clasts and fractured c...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::126cbde09b3b7c73a4750f7260b5a2de https://doi.org/10.1080/14702541.2013.855808 Zobrazit plný text záznamu