Fennoscandian palaeoglaciology reconstructed using a glacial geological inversion model

Abstract

DejJarlll1m l rif P/~) ' sical Ceogm!)/~) ', Slockholm L -n i[lersi~)I, S-I0691 Stockholm, Sweden BSTRACT. The e\'oluti o n of ice-shcc t co nfig ura ti o n a nd now p a tt ern in Fe nnosca ndi a th ro ug h th e las t g lac ia l eyclc was reco n s truc tcd using a g lacia l geologica l ilwe rsi o n model, i.c. a th eo reti ca l m od el tha t fo rm a li ses the procedure o f using the la ndfo rm record to reco n struct ice shee ts. Th e m odel uses m a ppcd now traces a nd degla cial meltwa ter la nd forms, as well as rela ti ve chron ologies d e rived fro m c roSS-CUlling stri ae a nd tilllineati o n s, as input d a ta . Fl o w-trace sys te m s w e re cl ass ifi ed into fo ur typ es: (i ) timetra nsg ressi\'e w e t-bed deglac ia l fa ns, (ii ) tim e-tra n sgr essi\'e fi-oze n-bed deglacia l fa n s, ( iii ) surge fa ns, a nd (i\') synchro n o us no n-dcglae ia l (e \'e lll ) fa ns. Us ing re la ti\'c chro n o logies a nd agg rega ti o n o f fa ns into g lac io logiea ll y pl a usible p a ttcrns, a seri es ofi ec-shee t co nfi gura ti ons at difk re nttime sli ces w as e reeled. A c hro n o logy lV as co n struc ted thro ug h co n -ela ti o n w ith d a ted stra ti g ra ph ica l record s a nd prox y d a ta re n ee ti ng g lo ba l ice \ '0 1 u m e. G eological ey ide nee ex ists fo r se \'C ra l di scre tc icc'-sh ee t confi g ura tio ns ce ntred 0 \ '(' 1' th e Sea ndina \'i a n mo ullla in ra nge during th e ea rl y \\'e iehse li a n. Th e build-up of th e m a in \\'e ir hseli a n Fe nn osca ndi a n ice sh ce t sta rt ed a t a pprox im a tel y 70 k a, a nd o ur res u lts indicate tha t it was c h a rac te ri sed b y a n ice shee t with a cc ntre of m ass located O\'e r so uth e rn Norway. Thi s co nfig ura ti o n h a d a n oli' p a tte rn w hi c h is poo rl y re produced b y c urrel1l numeri ca l m o d e ls of th e Fe nn osca ndi a n ice sh ee t. Atth e L as t G lacia l M ax imum t h e m a in ice di\·ide w as loca ted 0\'Cr th e Gu lf ofBOlhni a. A m aj o r bend in th e ice di\·ide was ca u sed by o utn ow o f ice to th e no rth wcs t O\'C r th e lowes t p a rt of the Sca ndin m'ia n m o unt a in c ha in . Wides pread a reas o f preserwd pre-I a te-\\'e ic hscli a n la nd scap es indi cate th a t th e ice shee t h ad a fr oze n-b ed co r e a r ea, whi c h wa s o nl y pa rtl y dimini shed in s izc b y in wa rd-tra n sg ress in" wet-bed zon es during th e decay phase.

Formalising an inversion methodology for reconstructing ice‐sheet retreat patterns from meltwater channels: application to the British Ice Sheet

“…Lateral channels are widely used by Scandinavian researchers to indicate margin positions of cold-based ice masses (e.g. Kleman, 1992;Kleman et al, 1997;Hättestrand, 1998), whilst subglacial channels approximate former equipotential surfaces and hence ice surface slope (e.g. Sugden et al, 1991).…”

“…This is especially apparent if one compares the brevity of information defining retreat patterns of the British Ice Sheet to that for the Laurentide or Fennoscandian ice sheets where landform patterns have been used to formulate ice-sheet scale retreat patterns (Dyke and Prest, 1987;Kleman et al, 1997). Geomorphological evidence of glaciation in Britain reported in the published literature has recently been compiled, bringing together the richness of landform information relating to the last (Late Devensian) British Ice Sheet (Clark et al, 2004).…”

“…Kleman, 1992;Kleman et al, 1997). This paper develops and applies a method by which meltwater channels in the BRITICE database may be systematically categorised with regard to their role in deglaciation.…”

Neoproterozoic Glaciated Basins: A Critical Review of the Snowball Earth Hypothesis by Comparison with Phanerozoic Glaciations

“…The thick ice-sheets envisaged in Snowball Earth models are likely to have been effective at insulating the bed, and thus resisted cold-based glacial conditions; however, where ice was thin over highs in the subglacial topography (typical of dispersal centres) cold-based conditions probably existed (cf. Kleman et al, 1997;Kleman & Hättestrand, 1999). Changes in basal thermal conditions may be initiated over time by surface cooling, or increased accumulation leading to downward advection of cold surface ice (Alley et al, 1997).…”

Time perspectives on glacial landscape formation—glacial flow chronology at Lac aux Goélands, northeastern Québec, Canada

“…Details of the model used in reconstructing palaeo-ice-flows are described elsewhere (Kleman and Borgström, 1996). This approach has been used previously in similar attempts to reconstruct palaeo-ice-flow from the glacial landform record present in, for example, Scandinavia (Kleman et al, 1997) and Labrador-Ungava, Canada .…”