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Large subglacial lake beneath the Laurentide Ice Sheet inferred from sedimentary sequences

¹ Scott Polar Research Institute, University of Cambridge, Cambridge CB2 1ER, UK
² Earth and Planetary Sciences Department, University of California–Santa Cruz, Santa Cruz, California 95064, USA
³ Large Lakes Observatory and Department of Geological Sciences, University of Minnesota–Duluth, Duluth, Minnesota 55812, USA
⁴ Earth and Planetary Sciences Department, University of California–Santa Cruz, Santa Cruz, California 95064, USA
⁵ Department of Geography, University of Sheffield, Sheffield S10 2TN, UK
⁶ Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA

Subglacial lakes identified beneath the Antarctic Ice Sheet belong to a rare category of unexplored environments on Earth's surface. The key to understanding the origin and longevity of subglacial lakes is likely contained in their sedimentary sequences. Here we explore the nature of a sedimentary succession in a deep tectonic trough identified as a prime candidate for a large subglacial paleolake. The trough is the 100-km-long, 620-m-deep Christie Bay, located in the east arm of the Great Slave Lake, Canada. High-resolution seismic reflection data and short sediment cores collected in the deep trough show a 150-m-thick sequence of fine-grained sedimentary lake fill separating glacial ice-contact deposits from draped Holocene lake sediments. We interpret this sequence to consist of sediments that accumulated in a subglacial lake that covered an area larger than 130 km². The inferred presence of a subglacial paleolake is supported by results from hydrologic modeling of drainage pathways beneath the Laurentide Ice Sheet during the last glacial maximum. Our data point toward the existence of a dynamic subglacial lake environment where sediments were delivered by discharge of meltwater from a subglacial water system. A core sample of the sedimentary lake fill in Christie Bay may elucidate whether living organisms exist in subglacial lakes.

Key Words: subglacial lake • ice sheet • sediment • hydrology • basal water