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.

The evolution of ice-sheet configuration and flow pattern in Fennoscandia through the last glacial cycle was reconstructed using a glacial geological inversion model, i.e. a theoretical model that formalises the procedure of using the landform record to reconstruct ice sheets. The model uses mapped flow traces and deglacial melt-water landforms, as well as relative chronologies derived from cross-cutting striae and till lineations, as input data. Flow-trace systems were classified into four types: (i) time-transgressive wet-bed deglacial fans, (ii) time-transgressive frozen-bed deglacial fans, (iii) surge fans, and (iv) synchronous non-deglacial (event) fans. Using relative chronologies and aggregation of fans into glaciologically plausible patterns, a series of ice-sheet Configurations at different time slices was erected. A chronology was constructed through correlation with dated stratigraphical records and proxy data reflecting global ice volume. Geological evidence exists for several discrete ice-sheet configurations centred over the Scandinavian mountain range during the early Weichselian. The build-up of the main Weichselian Fennoscandian ice sheet started at approximately 70 Ka, and our results indicate that it was characterised by an ice sheet with a centre of mass located over southern Norway. This configuration had a flow pattern which is poorly reproduced by current numerical models of the Fennoscandian ice sheet. At the Last Glacial Maximum the main ice divide was located overthe Gulf of Bothnia. A major bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the Scandinavian mountain chain. Widespread areas of preserved pre-late-Weichselian landscapes indicate that the ice sheet had a frozen-bed core area, which was only partly diminished in size by inward-transgressive wet-bed zones during the decay phase.

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The article discusses the nature of the glacial inversion problem, which is defined as the extraction of time-slice ice-sheet flow patterns from the patchy and partly overprinted landform record present in former ice-sheet areas. A coherent inversion model for derivation of flow patterns and interior ice-sheet configuration from geomorphological data is presented. Glacial landscapes are classified according to the three criteria of internal age gradients, presence or absence of meltwater traces aligned to flow traces, and basal condition (frozen bed/thawed bed) inferred from morphology. The inversion model uses landscapes classified accordingly, spatially delineated into fans, as input data. Relative chronologies at fan intersections are used to sort fans in a relative-age stack that can be linked to stratigraphic (dating) information.