Untangling the Quaternary Period—A Legacy of Stephen C. Porter
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Stephen C. Porter was an international leader in Quaternary science for several decades, having worked on most of the world’s continents and having led international organizations and a prominent interdisciplinary journal. His work influenced many individuals, and he played an essential role in linking Chinese Quaternary science with the broader international scientific community. This volume brings together nineteen papers of interdisciplinary Quaternary science honoring Porter. Special Paper 548 features papers from six continents, on wide-ranging topics including glaciation, paleoecology, landscape evolution, megafloods, and loess. The topical and geographical range of the papers, as well as their interdisciplinary nature, honor Porter’s distinct approach to Quaternary science and leadership that influences the field to this day.
Glaciers, isostasy, and eustasy in the Fraser Lowland: A new interpretation of late Pleistocene glaciation across the International Boundary
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Published:April 07, 2021
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CiteCitation
Douglas H. Clark, John J. Clague, 2021. "Glaciers, isostasy, and eustasy in the Fraser Lowland: A new interpretation of late Pleistocene glaciation across the International Boundary", Untangling the Quaternary Period—A Legacy of Stephen C. Porter, Richard B. Waitt, Glenn D. Thackray, Alan R. Gillespie
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ABSTRACT
High-resolution light detection and ranging (lidar) data and new stratigraphic, lake sediment, and radiocarbon constraints help to resolve a long-standing dispute regarding the timing and nature of the Everson interstade and the Sumas stade, the last major events of the Cordilleran ice sheet in the Fraser Lowland. The new data indicate that: (1) an early, maximum Sumas advance occurred roughly 14,500 cal yr B.P. (calibrated 14C years before 1950), extending into the Salish Sea near Bellingham, Washington; (2) ice retreated north of the International Boundary long enough for forests to establish in deglaciated lowland sites; (3) a rapid, short-lived rise in local relative sea level (RSL) of ~20–30 m, possibly related to meltwater pulse 1A or the collapse of a glacio-isostatic forebulge, inundated the U.S. portion of the lowlands up to ~130 m above modern sea level; and (4) directly following this transgression at ca. 14,000 cal yr B.P., ice readvanced across the border to nearly the same limit as reached during the early Sumas period. Distinct crosscutting marine strandlines (erosional and depositional remains of emerged marine shorelines), subaerial moraines, and till plains imaged in lidar data indicate that following the maximum extent of the second Sumas advance, local RSL progressively lowered as the glacier fluctuated and gradually thinned. By ca. 13,000 cal yr B.P., ice had retreated north of the border, and local RSL had fallen to within ~4 m of modern.
A layer of possible loess in sediments in Squalicum Lake suggests a possible third and final Sumas readvance between 13,000 and 11,150 cal yr B.P., at which time a moraine was constructed ~8 km south of the border near the town of Sumas, Washington. Together, our results suggest that the concept of a distinct Everson interstade and Sumas stade should be abandoned in favor of a more nuanced “Sumas episode” that encompasses the sequence of events recorded in the Fraser Lowland.
- British Columbia
- C-14
- Canada
- carbon
- Cenozoic
- clastic sediments
- Cordilleran ice sheet
- cores
- deglaciation
- eustasy
- Fraser River
- glacial environment
- glacial sedimentation
- glaciation
- glaciers
- glaciomarine environment
- glaciomarine sedimentation
- ice
- isostasy
- isotopes
- laser methods
- lidar methods
- loess
- lowlands
- marine environment
- marine sedimentation
- moraines
- paleoclimatology
- Pleistocene
- Quaternary
- radioactive isotopes
- remote sensing
- sea-level changes
- sedimentation
- sediments
- Shuttle Imaging Radar
- transgression
- United States
- upper Pleistocene
- Washington
- Western Canada
- Whatcom County Washington
- Fraser Lowland