Éditions Seteun

English Abstract

Abstract : Periglacial geo­mor­pho­logy is one of the oldest bran­ches of cli­ma­tic geo­mor­pho­logy. After almost a cen­tury of research, a mor­pho­ge­nic system has been cons­truc­ted where mecha­ni­cal pro­ces­ses of wea­the­ring act as exclu­sive debris pro­du­cers. Although, over the past decade, this model has been contes­ted. Through an epis­te­mo­lo­gi­cal pers­pec­tive helped by grids bor­ro­wed from the phi­lo­so­phy of scien­ces, we show that two research pro­grams have insi­diously emer­ged with dis­tinct but com­ple­men­tary objec­ti­ves : the first one, his­to­ri­cally the oldest, deals with models of spe­ci­fic (zonal) pro­ces­ses whe­reas the second one tries to unders­tand the inte­rac­tion bet­ween spe­ci­fic and non-spe­ci­fic pro­ces­ses and builds a hie­rar­chy of wea­the­ring pro­ces­ses. Being posi­tio­ned in this second pers­pec­tive, we have stu­died the impact of bio­ge­nic (fungal) pro­ces­ses of wea­the­ring on debris pro­duc­tion in Iceland and The Faeroes. Fieldwork and labo­ra­tory expe­ri­ments show that cryp­toen­do­li­thic microor­ga­nisms are the first agents of wea­the­ring on loose sur­fa­ces (morai­nes, sandur), faci­li­ta­ting, through wea­the­ring rind pro­duc­tion, the sub­se­quent action of mecha­ni­cal pro­ces­ses. These wea­the­ring rinds appear also as a good dating tool over short time scale (less than 150 years). Finally, regio­nal pers­pec­ti­ves of che­mi­cal or bio­che­mi­cal wea­the­ring of vol­ca­nic sur­fa­ces show that these pro­ces­ses allow great migra­tions, tem­po­rary (rock coa­tings) or defi­ni­tive (ocea­nic basins), of mine­ral matter. In this way, che­mi­cal and bio­che­mi­cal ero­sion appears as one of the most impor­tant pro­ces­ses in the sha­ping of humid peri­gla­cial land­sca­pes.


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