Glaciation in the area of Charlie Lake, New Brunswick, has produced a granitic till very similar in appearance to weathered bedrock. Portions of weathered granite were moved intact and redeposited as imbricated rafts under basal till. The rafts vary from 0.3 to 2 m in thickness over a 10 m wide exposure and show deep weathering zones and brittle deformation, despite the fact that they are highly friable. The rafts are separated by glacigenic fault planes defined by lenses of diamict and rare clasts of distant origin. They are recognizable only in excavations where fault planes can be seen to delineate slabs of rock imbricated mainly upglacier. Surface weathering features, including core-stones, were preserved during movement over short distances.
A variety of deformation structures attributed to glacial overriding occur in rock and sediment of an intermontane valley at Hat Creek, British Columbia. Sediments exposed in vertical outcrops along Hat Creek, display contrasting styles of deformation involving fluidization, as well as brittle and ductile deformations that appear to have been formed concurrently. Typical structures include: joints, faults, infillings, and clastic dikes comprising; fluid-escape structures, glacigenic injections, as well as fluidal and viscous hydraulic expulsions. A model is presented for the glacitectonic formation of hydraulic expulsions during compression of underlying partially saturated unfrozen sediments. Bedrock exposed in excavations at higher elevations displays joints, faults and wedge fillings possibly associated with subglacial freezing during glacial advance. Orientation of the structures are correlative with directions of glacier flow as inferred from fabric, striae and geomorphology. The structures are believed to have been the product of several interrelated factors, including: glacial dynamics, engineering properties of the glacier bed material, subglacial relief, and the variation between coalescing glaciers. Correlation with directions of glacial movement, association with glacial faciès and infilling by glacial sediments, are conditions considered to be glacigenic signatures useful in differentiation of glacial from nonglacial (e.g. earthquake) origins for similar structures elsewhere.
Late Wisconsinan Fraser Glaciation retreat-phase deposits and landforms in the east-central Taseko Lakes area, British Columbia, are used to demonstrate a four-phase model of deglaciation. During phase I, at the onset of ice retreat, the Cordilleran Ice Sheet occupied much of the study area, blocking southward drainage of Fraser River. Phase II was marked by the deglaciation of uplands and plateaux. Meltwater drainage patterns were controlled by stagnating glaciers confined to valleys. Phase III commenced as remnant ice in the Fraser Valley downwasted to between 850 and 760 m elevation. At this time, interlobate glacial lakes formed in hanging valleys east of Fraser River. Drainage of glacial lakes occurred subglacially, and was accompanied by disintegration of remnant ice and an increase in mass movements in valleys. These events were followed by decreased sedimentation rates, reflecting lower meltwater volumes and exhaustion of unstable glacial debris during phase IV. Postglaciation valley fill was subject to fluvial degradation and terracing as modern drainage patterns became established.
ABSTRACT. A comparison of bedrock fra ctures with orientation of structures and fabric in the overlying late Pleistocene basal till indicates a 'sequence of common glacial origin. The deforma ti ons in bedrock and till, a nd the d eposition of the till layer, were accomplished by two glac ia l flows that were part of a mountain ice sheet: the r egional (moving south-south-east) and the local (moving south-south-west ) a long Peavine Valley.The following sequence of events is postulated from this investigation: the initial glacial advance from the north-north-west that produced conjugate low-angle shear fractures in the b edrock was followed by competition of both the regional and the Peavine Valley glacial flows which also produced low-a ngle fra cture systems. As the over-riding ice becam e thi cker, high-angl e conjugate fra ctures were form ed by both glacial flows. Subseq uently, south-east-dipping injection wedges were form ed by the regional ice, which was concurrently erodi ng the down-glacier pa rts of the wedged blocks, depositing local till, and produci ng sigmoidal deformations in this till. The main deposition of the overlying lodgement till was accomplished by an interaction of both the r egio nal a nd the Peavine Valley glacia l flows, and the lodgement was supplemented by shearing . of the till, producing fissility. Bedrock wedging, as a significant process of glacial erosion, is believed to be discussed here for the first time.R ESUME . Une sequence de diformation, d'erosion et depots glaciaires cl l'inter.face glace-roche pendant la derniere glaciation ; Cranbrook, Colombie Britannique, Canada . Un e comparaison des fa ill es du lit rocheux avec les orientations des st ruct ures et des grains dans la moraine d e fond qui recouvre to ut le Pleistocene recent, indique un e sequence d 'origine glaciaire ordinai re. Les deforma tions dans le lit roch eux et les moraines et le depot du niveau morainique ont ete accomplis par deux ecoulements glaciaires qui appartenaie nt a un e calotte glaciaire d e montagne: l'un regional (se mouvant Sud Sud-Est) et l'un local (se depla<;ant Sud Sud-Ouest) le long de la P eavine Valley.De ces investigations on deduit que la succession des evenements a ete la suivante : l'avance glaciaire initiale depuis le Nord Nord-Ouest qui produisit des cassures conjuguees a u cisaillement sou s un angle faibl e dans le lit rocheux fut suivie de la combinaison d es courants de glace regionaux et du Peavine Valley qui produisit aussi d es systemes de cassures a angles fa ibles. Comme la glace surmontante devint plus epaisse, des cassures conjuguees a angles forts furent form ees par les deux coura nts d e glace. Pa r la suite, des coins d'inj ection s'enfon<;ant vers le Sud Est furent formes p a r la glace regiona le qui erodait e n m e me temps la partie aval d es blocs en coin, d eposa it une morain e locale et produisait d es deformat ions sigmoidales dans cette moraine. La plus grande partie des depots de la moraine de cou verture se fit par une interaction des ecoulements d e...
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