Open AccessThe environment in and around ice‐dammed lakes in the moderately high relief setting of the southern Canadian Cordillera
Author(s) -
JOHNSEN TIMOTHY F.,
BRENNAND TRACY A.
Publication year - 2006
Publication title -
boreas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 74
eISSN - 1502-3885
pISSN - 0300-9483
DOI - 10.1111/j.1502-3885.2006.tb01116.x
Subject(s) - geology , turbidity current , sedimentary depositional environment , glacial period , sediment , plateau (mathematics) , shelf ice , ice sheet , debris , tributary , glacial lake , geomorphology , moraine , structural basin , oceanography , ice stream , sea ice , cryosphere , mathematical analysis , mathematics , cartography , geography
During decay of the Cordilleran Ice Sheet, ˜13 000–10000 cal. yr BP, numerous ice‐dammed, ribbon‐shaped lakes developed within the moderately deep valleys of the Interior Plateau of British Columbia. We describe the pattern and characteristics of lake sediments within the Thompson Valley, propose a palaeoenvironmental model for glacial lakes Thompson and Deadman and explore their implications for the palaeogeography of Cordilleran Ice Sheet decay. Seventeen glaciolacustrine lithofacies are identified within deltas, subaqueous fans and lake‐bottom beds. Sediments accumulated at high rates and by a diversity of sediment dispersal and depositional processes: hyperpycnal and surge‐type turbidity currents, grain flows and debris flows. Megascale subaqueous failures (tens of metres thick) were facilitated by high sedimentation rates. The palaeoenvironmental model highlights: (i) high rates of basin infilling; (ii) the dominant role of tributary rivers, rather than valley‐occupying ice, in delivering water and sediment to lakes; and (iii) the role of melt cycles, jökulhlaups and hyperpycnal flows in sediment delivery. These conditions, in combination with a lack of organics and a fining upward sequence in lake sediments, suggest that glacial lakes Thompson and Deadman were coeval with dwindling plateau ice.