Late Holocene history of Squamish River north of Brackendale, British Columbia

Laminated silt, organic-rich silt, and peat exposed in the banks of Squamish River north of Brackendale, British Columbia, provide evidence for a lake impounded behind Cheekye Fan during the late Holocene. The lake gradually filled with sediment as Squamish River advanced its delta and floodplain southward toward the fan. Radiocarbon ages on detrital and growth-position plant fossils provide evidence that the lake reached up to 9 km upstream of Cheekye Fan about 3400 years ago and persisted until about 2300 years ago. Geomorphic observations and the distribution of fine-grained facies indicate that both Cheakamus and Squamish rivers contributed sediment to the lake; consequently, different depositional environments existed near Cheekye Fan than farther upstream. Debris flows that travelled down Cheekye River to Cheakamus River provided fine-grained sediment that accumulated in the deepest part of the lake just north of the fan. Farther upstream, organic-rich silt was deposited in fens and marshes surrounding the lake. Squamish River is confined by steep banks of cobble-boulder gravel 1.5–2 km north of the present Cheakamus-Squamish confluence, suggesting that coarse sediment transported by Cheakamus River controlled the lake outlet and, accordingly, lake level. As sediment delivery from Cheakamus and Cheekye rivers declined through the late Holocene, the lake outlet was progressively lowered and the lake drained. Sedimentation in Squamish Valley upstream of Cheekye Fan is also influenced by landslides at Mt. Cayley, 45 km upstream. A large landslide at Mt. Cayley about 1100 years ago produced a sediment pulse that propagated downstream and caused the floodplain above Cheekye Fan to aggrade. Sand buried the remaining fens that covered part of the low-gradient floodplain, leading to their replacement by coniferous and riparian forest. The model that I use to interpret Squamish River sedimentary environments can be applied to other low-gradient floodplains influenced by alluvial fans

Influence of a large debris flow fan on the late Holocene evolution of Squamish River, southwest British Columbia, Canada

Cheekye Fan is a large paraglacial debris flow fan in southwest British Columbia. It owes its origin to the collapse of Mount Garibaldi, a volcano that erupted in contact with glacier ice near the end of the Pleistocene Epoch. The fan extended across Howe Sound, isolating a freshwater lake upstream of the fan from a fjord downstream of it. Squamish River built a delta into this lake during the Holocene. We use 28 radiocarbon dates to describe the final infilling of the lake and the subsequent evolution of the Squamish River floodplain over the past 3300 years. These events are recorded in fine-grained lacustrine, wetland, river channel and overbank sediments exposed in the banks of Squamish River over a distance of more than 10 km upstream of the fan. We link these deposits to construction, persistence, and eventual degradation of the dam formed by Cheekye Fan and a smaller inset fan formed by Cheakamus River, into which Cheekye River flows. The coupled Cheekye Fan â Squamish River floodplain system is similar to the low-gradient valley floors upstream of fans in California and the Canadian Rocky Mountains. Future debris flows and landslides in the headwaters of Cheekye River are likely to continue to affect base level along lower Squamish River. We speculate that future aggradation of Cheekye Fan would cause increased flooding and sediment deposition upstream of this barrier. These landscape linkages should be included in future land-use planning in lower Squamish River valley.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Mid-cretaceous high arctic stratigraphy, climate, and oceanic anoxic events

Over the past decades, much research has focused on the mid-Cretaceous greenhouse climate, the formation of widespread organic-rich black shales, and cooling intervals from low- to mid-latitude sections. Data from the High Arctic, however, are limited. In this paper, we present high-resolution geochemical records for an ~1.8-km-thick sedimentary succession exposed on Axel Heiberg Island in the Canadian Arctic Archipelago at a paleolatitude of ~71°N. For the first time, we have da