Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden
2013 (English)In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 42, no 1, 71-83 p.Article in journal (Refereed) Published
Internal structure, stable isotope composition and tritium concentration were measured in and around debrisbearingice at the margin of Storglaciären, where englacial debris bands have previously been inferred to form bythrusting. Two types of debris bands were distinguished: (i) an unsorted diamicton band that is laterally continuousfor more than 200 m, and (ii) well-sorted sand and gravel bands that are lenticular and discontinuous.Above-background tritium levels and enrichment of d18O and dD in ice from the diamicton band indicateentrainment by basal freeze-on since 1952. Isotopic enrichment and tritium-free ice in the sandy debris bands alsoindicate entrainment in freezing water, but prior to 1952. The lenticular cross-section, sorting and stratification ofthe sandy bands suggest that they were deposited englacially. The basally accreted diamicton band has beenelevated tens of metres above the bed and presently overlies the englacially deposited sandy bands, suggesting thatthe stratigraphy has been disrupted. Three interpretations could account for these observations: (i) thrusting offast-moving ice over slow, marginal ice uplifting recently accreted basal ice along the fault; (ii) folding near themargin, elevating young basal ice over older basal and englacial ice; and (iii) debris-band formation by anunknown mechanism and subsequent contamination of ice geochemical properties by meltwater flow throughdebris bands. Although none of these interpretations is consistent with all measurements, folding is mostcompatible with observations and local ice-flow kinematics.
Place, publisher, year, edition, pages
2013. Vol. 42, no 1, 71-83 p.
Research subject Geography, Physical Geography
IdentifiersURN: urn:nbn:se:su:diva-85250DOI: 10.1111/j.1502-3885.2012.00274.xISI: 000316342600005OAI: oai:DiVA.org:su-85250DiVA: diva2:583129