Glacial landforms and sediments (landsystem) of the Smoking Hills area, Northwest Territories, Canada: Implications for regional Pliocene – Pleistocene Laurentide Ice Sheet dynamics

• Main Authors: Evans, D.J.A (Author), Galloway, J.M (Author), Gosse, J.C (Author), Smith, I.R (Author)
• Format: Article
• Language: English
• Published: Elsevier Ltd 2021
• Subjects: Amundsen Gulf; Arctic Ocean; Beaufort Sea; bedrock; Canada; Canadian Arctic; Cosmogenic nuclide burial dating; Cretaceous; Deposits; diamicton; disturbance; England; Franklin Bay; geomorphology; Geomorphology; Glacial geology; glacial landform; glaciation; Glaciers; Glacitectonite; Great Bear Lake; Hill areas; Horton River; Ice; Ice stream flowset; Ice stream flowsets; Ice wedges; ice-dammed lake; interglacial; Interlobate ice-dammed lake; Isotopes; Lakes; Landforms; landscape evolution; Laurentide Ice Sheet; Laurentide ice sheets; Liverpool Bay; Mackenzie Valley; moraine; Northwest Territories; permafrost; Pliocene; Pliocene glaciation; Pliocene-Pleistocene boundary; Polythermal ice sheet marginal landsystem; sediment analysis; sedimentation; smoking; Smoking hill; Smoking Hills; Stratigraphy; United Kingdom
• Online Access: View Fulltext in Publisher

 The Smoking Hills area in the western Canadian Arctic was purported to contain a regionally rare Quaternary stratigraphic section with multiple, local ice cap-derived tills and a long chronology constrained by palaeomagnetic markers. We present a fundamental revision of previous glacial and magnetostratigraphic interpretations based on detailed sedimentological and structural analyses of the main stratigraphic section and many new exposures, cosmogenic nuclide isochron burial dating, and a systematic reconstruction of the geomorphology and landscape evolution using a glacial landsystem approach. We demonstrate that the Smoking Hills area was fully glaciated during the last (Wisconsinan) glaciation. Previously reported tills ascribed to multiple glaciations represent instead a complex facies sequence of glacitectonic thrust stacking of Laurentide Ice Sheet (LIS) sourced diamictons, glacilacustrine and glacifluvial deposits, together with previously unidentified, poorly-consolidated Cretaceous bedrock rafts and deformed intraclasts. Much of this sedimentation and glacitectonic activity dates to the last (Wisconsinan) glaciation and can be reconciled with a polythermal ice sheet marginal landsystem signature, wherein ice-cored moraine belts are developed over subglacial bedforms (flutings) arranged in discrete flowsets. The flowsets record the complex interaction of ice streams nourished by ice flowing from three main sources: Great Bear Lake to the south, Amundsen Gulf (Franklin Bay) to the east and Liverpool Bay (Mackenzie Valley) to the southwest. Decoupling of the ice margins of these three ice sources gave rise to interlobate ice-dammed lake development over the lower Horton River area during final deglaciation. A cosmogenic 26Al/10Be isochron burial age of 2.9 ± 0.3 Ma (1σ, n = 4) from the lowermost glacial diamicton and glacitectonite sequence provides evidence of perhaps the earliest continental glaciation of this region. This deposit postdates, or is perhaps a later re-advance of the same initial glaciation that produced widespread glacitectonic disturbance of bedrock in preglacial valley networks and early glacifluvial and glacilacustrine deposits containing an ice wedge pseudomorph. Subsequent glaciations have largely removed or cannibalised pre-existing records to construct complex till and glacitectonite stacks that contain reworked organics with non-finite radiocarbon ages. One site preserves buried “old” glacier ice in which prominent ice wedges had formed during an interglacial permafrost phase and were then deformed down-flow by the LIS during the Wisconsinan glaciation. © 2021