The Fluvial Reworking of Late Pleistocene Drift, Squamish River Drainage Basin, Southwestern British Colombia

Abstract

Reworked glacial sediment(s) (RGS) represents the component of paraglacial sedimentation derived from the fluvial reworking of late Pleistocene glacial deposits in the postglacial landscape. In Squamish River drainage basin, southwestern British Columbia, the primary source of the RGS transferred to Squamish Valley is fluvial incision into valley-fill deposits in the five major tributary valleys of the watershed. The total volume of RGS transferred to Squamish Valley is 415 x 106m3. The volume of RGS from the individual tributary valleys range from 6 to 130 x 106m3 with valley morphology and late Quaternary history being the important controls upon the specific amount. Geomorphic evidence indicates that the bulk of the RGS was contributed to Squamish Valley thousands of years ago. The transfer of RGS continues at a very low residual rate in the contemporary landscape. RGS appear to represent a minor portion of the Squamish valley-fill and a small component of the postglacial sediments stored in Squamish Valley.Les sédiments glaciaires remaniés sont une composante de la sédimentation périglaciaire issue du remaniement fluviatile des dépôts glaciaires dans le paysage postglaciaire. Dans le bassin versant de la Squamish River, la principale source de sédiments glaciaires remaniés provient d'un encaissement fluvial dans les matériaux de remblaiement des cinq principales vallées tributaires du bassin-versant. La quantité de matériaux transportée de ces vallées tributaires à la vallée Squamish est de 415 x 106m3. Les volumes impliqués à partir de chacune des vallées varient de 6 à 130 x 106m3, la morphologie de la vallée et le type d'évolution au Quaternaire supérieur étant les principaux facteurs intervenant dans les quantités exportées. Les données géomorphologiques démontrent que la plus grande partie de l'apport sédimentaire était déjà répartie dans la vallée Squamish il y a des milliers d'années, mais qu'il se poursuit à un taux résiduel dans le paysage actuel. Les dépôts glaciaires remaniés représentent une composante mineure de l'approvisionnement de sédiments postglaciaires dans la vallée de la Squamish River.Umgestaltete glaziale Sedimente sind ein Bestandteil der paragiazialen Sedimentierung, die aus der fluviatilen Umgestaltung glazialer Ablagerungen des spàten Pleistozâns in der postglazialen Landschaft hervorgegangen ist. Im Emahrungsbecken des Squamish River, sùdwestliches British Columbia, ist die Hauptquelle der zum Squamish-Tal transportierten umgearbeiteten glazialen Sedimente fluviatiles Ein-schneiden in die Talaufschùttungsablagerungen in den fùnf wichtigsten Nebentàlern des Flussbeckens. Das gesamte Volumen der zum Squamish-Tal transportierten umgestalteten glazialen Sedimente betràgt 415 x 106m3. Das Volumen des Materials von den einzelnen Nebentàlern reicht von 6 bis 130 x 106m3, wobei Talmorphologie und Geschichte im spàten Quaternàr die wichtigen Kontrollfaktoren fur die jeweilige Menge darstellen. Geomorphologische Daten zeigen, dass der grôsste Teil der umgestalteten glazialen Ablagerungen sc...

Postglacial topographic evolution of glaciated valleys: a stochastic landscape evolution model

“…These values represent maximum possible estimates, since the linear diffusion model neglects incision through the valley fill. The predictions from the linear diffusion model are, nevertheless, an order of magnitude lower than the depth of Holocene fill observed in formerly glaciated valleys in British Columbia (Church and Ryder, 1972;Brooks, 1994). The linear diffusion model reproduces some of the features documented to follow the retreat of valley glaciers, including the decay of upper rockslopes to a fluvial form, but it has several limitations: (i) the decay of shoulders is not rapid enough to be consistent with observed natural rates; (ii) derived material is stored in mid-slope locations in addition to reaching the valley bottom; (iii) the drainage network structure of the upper rockslopes can only be smoothed by diffusion, whereas in practice rectilinear channels are observed to develop on rockslopes.…”

“…. as much as 175 m of deposition'; p. 3063), and Brooks (1994), working in the Squamish basin of the southernmost Coast Mountains, reported subsequent fluvial degradation of 40 to 90 m in various reaches of five major tributaries. These numbers correspond broadly with the model results, although the modelled amount of deposition is lower than that observed.…”

A 14,500-year record of landscape change from Okpilak Lake, northeastern Brooks Range, northern Alaska

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