Englacial lake dynamics within a Pleistocene cordilleran ice sheet at Kima' Kho tuya (British Columbia, Canada)

Autor: Benjamin Edwards, James K. Russell, Marie Turnbull, Lucy Porritt
Rok vydání: 2021
Předmět:
Zdroj: Quaternary Science Reviews. 273:107247
ISSN: 0277-3791
DOI: 10.1016/j.quascirev.2021.107247
Popis: Passage zones are stratigraphic surfaces found in littoral settings separating deposits diagnostic of subaqueous environments from overlying sequences of subaerial deposits. In glaciovolcanic settings, passage zone surfaces are unequivocal records of the heights and depths of paleo-englacial lakes at a specific point in time and space, thereby, informing on the presence and nature of the enclosing ice sheet. Kima' Kho, a Pleistocene glaciovolcano (i.e. tuya) located in the northern Cordillera of British Columbia, features multiple and diverse passage zones. The basaltic volcano comprises four main stratigraphic packages: i) subaqueously and subaerially deposited lapilli tuffs (Lt1/Lt2) forming a central tephra cone and representing an explosive onset to the eruption, ii) subaqueously deposited, steeply-inclined beds of tuff breccia dominated by pillow lava fragments (Tb1-3), iii) stacked sheets of subaerial pahoehoe lavas (L1-3), and iv) dykes and sills (I) intruding all units. Stratigraphic and geochemical relationships suggest that Kima' Kho volcanism was continuous and 40Ar/39Ar geochronometry on three samples yields a mean age of 1949 ± 63 ka. Three temporally distinct passage zones record the interplay between growth of the volcanic edifice, syn-volcanic melting of the enclosing ice sheet, and fluctuations in the depth of the englacial lake. The earliest passage zone (PZ1) is expressed in two different ways marking a transition from explosive to effusive eruption: (i) within pyroclastic deposits of the tephra cone (
Databáze: OpenAIRE
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