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Glaciation

Summary

Evidence for past glaciation exists on Calvert Island and the surrounding continental shelf, but the extent and timing of the recent Pleistocene glaciation is poorly constrained. We are working towards a better understanding of the glacial history of the Hakai region, including possible post-LGM re-advances of glaciers on(to) Calvert Island.

Progress Updates

For about the last 5,000 years of the late Pleistocene (approximately 16,500 to 11,500 years ago), climate was characterized by a ‘flickering’ signal (Menounos et al., 2009) that alternated between glacial and interglacial states. There is evidence of short-lived, localized glacial re-advances during the Older Dryas (~14,000 years ago) and Younger Dryas (~12,800 to 11,500 years ago) stadial periods and, more recently, during the Holocene. In BC, such postglacial Pleistocene re-advances have only been identified in the southwestern (e.g., Clague et al., 1997; Friele and Clague 2002a, b), north-central (e.g., Lakeman et al. 2008) and southeastern (Osborn and Gerloff, 1997) parts of the province, which makes the discovery of a post-glacial re-advance on the central BC coast of tremendous interest.

Geomorphic mapping of glacial features in the region using LiDAR and lithostratigraphic and paleoecological evidence from an exposed coastal bluff at “Foggy Cove” on northwestern Calvert Island suggests a short-lived glacial re-advance during the Bølling and Older Dryas climatic phases.  Between 15,100 and 13,800 years ago, the environment at Foggy Cove was a tidal marsh that was then overridden by glacial ice sometime after 14,200-13,800 years ago.  The ice retreated prior to 14,000-13,800 years ago, allowing a soil to develop at the top of the sequence.

These findings fill an important spatial and temporal gap in knowledge of fluctuations of the retreating Cordilleran Ice Sheet and have implications for other research at the Hakai Institute on climate and sea-level reconstructions, archaeology, and paleoecology. These findings were presented at the 2014 Geological Society of America meeting in Vancouver (Eamer et al. 2014) and a manuscript is in preparation for a peer-reviewed journal in early 2015.

Further investigation of the glacial history of Calvert Island includes continued field mapping, coring of lakes dammed or intersected by glacial moraines that are believed to contain key information on late-glacial landscape changes, and cosmogenic exposure dating of moraines and glacier-scoured bedrock surfaces to provide a chronology of ice extent and related sediment generation and/or delivery in the area.  This latter initiative is of particular interest for the new Coastal Sand Ecosystems (CSE) Program at Hakai.

 

Photograph of the Foggy Cove sedimentary sequence with key stratigraphic units labeled. Unit 1 consists of sands and gravels that potentially represent the previous glacial retreat. Unit 4 is fine-grained tidal marsh sediment dated at ~15,000 years ago. Unit 3 is a coarsening-upward glaciofluvial advance sequence that was deposited between ~15,000 and 14,000 years ago. Unit 4 is a till inferred to be ~14,000 years old, and Unit 5 is an ancient soil dated to ~ 13,800 years old. Photo by Jordan Eamer.

 

Hakai PhD student, Jordan Eamer (UVic) preparing a sedimentary exposure at Foggy Cove for analysis and sampling. The darker band consists of sediments deposited in a tidal marsh around 15,000 years ago when sea level was slightly higher than present. Photo by Dan Shugar. Marsh paleoecology analyses were conducted by Alice Telka of Paleotec Services.