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Titolo:
The influence of rock hardness and divergent weathering on the interpretation of apatite fission-track denudation rates - Evidence from charnockites in South India and Sri Lanka
Autore:
Gunnell, Y; Louchet, A;
Indirizzi:
French Inst, Dept Ecol, Pondicherry 605001, India French Inst Pondicherry India 605001 ept Ecol, Pondicherry 605001, India Univ Paris 04, Inst Geog, F-75005 Paris, France Univ Paris 04 Paris France F-75005 04, Inst Geog, F-75005 Paris, France
Titolo Testata:
ZEITSCHRIFT FUR GEOMORPHOLOGIE
fascicolo: 1, volume: 44, anno: 2000,
pagine: 33 - 57
SICI:
0372-8854(200003)44:1<33:TIORHA>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
EVOLUTION; GONDWANA; SHIELD; ND;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Gunnell, Y French Inst, Dept Ecol, 11 St Louis St,POB 33, Pondicherry 605001, India French Inst 11 St Louis St,POB 33 Pondicherry India 605001 dia
Citazione:
Y. Gunnell e A. Louchet, "The influence of rock hardness and divergent weathering on the interpretation of apatite fission-track denudation rates - Evidence from charnockites in South India and Sri Lanka", Z GEOMORPH, 44(1), 2000, pp. 33-57

Abstract

This paper puts forward the importance of lithology in landscape development and its bearing on the interpretation of apatite fission-track data. ThePrecambrian charnockites of South India and Sri Lanka, which form some of the highest existing relief encountered in any stable shield region, are studied from several different angles and used as supporting evidence to the notion that their current elevation is the result of long-term divergent weathering. An overview of the observed rock mass properties of these granulitic rocks (texture, mineralogy, permeability, joint pattern) leads to the conclusion that rock hardness is an important parameter to consider when interpreting apatite cooling rates in terms of denudation rates. On charnockitic lithologies of the Nilgiri highlands (similar to 2,600 m), long-term cooling rates are found to be, for identical time spans, nearly half the ratesmeasured in the upland gneiss of the neighbouring Dharwar Craton (similar to 900 m). Though Vertical block-faulted uplift in the Cenozoic has been recurringly postulated for the charnockite massifs, compelling evidence for this is still lacking. The 1,200 to 2,200 m of existing relief is therefore attributed to divergent weathering. A traditional interpretation would attribute this lithological selectivity in erosion processes to an increase in the seasonality of Cenozoic climates, thereby enhancing energy expenditure and stripping of the land surface. Even if the emphasis on radiation-drivenfactors may find supporting evidence world wide, the systematic occurrenceof massive charnockites at the hightest levels of any given portion of thelandscape seems principally due to their extremely low porosity and wide joint spacing rather than to mineralogy or any other factor. This exceptional insensitivity minimizes the impact of climate change in explaining the highland scenery of South India and Sri Lanka.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/06/19 alle ore 16:59:54