Quaternary geology, stratigraphy and applied geomorphology in the southern Nechako Plateau, central British Columbia
| dc.contributor.author | Mate, David John | en_US |
| dc.date.accessioned | 2024-08-14T22:44:37Z | |
| dc.date.available | 2024-08-14T22:44:37Z | |
| dc.date.copyright | 2000 | en_US |
| dc.date.issued | 2000 | |
| dc.degree.department | School of Earth and Ocean Sciences | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | Erosion along the Nechako Reservoir and Skins Lake Spillway has resulted in unusually well exposed Quaternary and Holocene stratigraphy. Surficial sediments in the study area are mostly products of the Late Wisconsinan glaciation (Fraser). New evidence for pre-late Wisconsinan sedimentation has been found in a section along the shores of the Nechako Reservoir. Till of an older glaciation and organic-bearing, blue grey, lacustrine sediments of probable Middle Wisconsinan age underlie younger sediments deposited during the Fraser Glaciation. Sediments deposited in front of the ice margin were overridden during ice advance and are locally preserved in the largest valleys. Quaternary sediments cover most of the study area and large bedrock exposures are rare. The distribution of advance-phase glaciolacustrine sediments and associated deltaic deposits has shown that advance-phase lakes occurred at least up to several metres above the modem reservoir level (approximately 855 m). Till is the most common Pleistocene sediment covering approximately 80% of the area mainly as blankets greater than 1 metre thick. Retreat-phase glaciofluvial and glaciolacustrine deposits and fluvial sediments occur mainly along the Cheslatta River valley. Holocene bogs and swamps are common in low-lying areas between streamlined ridges. Crag-and-tails, flutings, and drumlinoid ridges with a generally consistent northeast trend are the dominant landforms in the study area. Most stoss-ends of these forms consist of bedrock knobs, while ridges of till occur down-ice. Crescent and comma shaped erosional depressions wrap around these forms and are often filled with bogs or standing water. They often combine to form large troughs oriented transverse to subglacial flow. It is concluded that these depressions are formed by subglacial meltwater floods. These floods have enhanced the preexisting subglacial topography and their progressive channelization is believed to have formed tunnel valleys within the region. These valleys are 1-2 km wide, flat-floored, steep sided and contain misfit streams and eskers in their bottoms. Stratigraphic and geomorphic studies were conducted at several slope failures within the study area. Translational landslides are common along the shoreline of the Nechako Reservoir, in particular, Chelaslie Arm. They are approximately 15-50 m wide and usually extend 15-30 m up slope. Typically, these slides occur on southwest facing shorelines, consist of numerous small slump blocks and have main scarps less than a metre high. Slope movements in this area are smaller and have shallower rupture surfaces than those along the Cheslatta River. Two active complex rotational-earthflow landslides were Investigated along a portion of the Cheslatta River that extends from a spillway at Ootsa Lake to Cheslatta Lake. Longitudinal profiles and detailed field observations were recorded at both slope movements. Slump 1 was approximately 34 m wide, 14 m high, has a 6 m high main scarp and one slump block. Slump 2 was approximately 230 m wide, 24 m high, had a 3 m high main scarp and three separate slump blocks. Both have amphitheatre shaped main scarps, some backward-tilted slump blocks, and earthflows and slickenside surfaces at rheir base. A small sag pond was also found at slump 2. Several factors are responsible for translational slope movements. They include removal of lateral support by wave erosion at the base of shoreline slopes and shoreline shaped erosional depressions wrap around these forms and are often filled with bogs or standing water. They often combine to form large troughs oriented transverse to subglacial flow. It is concluded that these depressions are formed by subglacial meltwater floods. These floods have enhanced the preexisting subglacial topography and their progressive channelization is believed to have formed tunnel valleys within the region. These valleys are 1-2 km wide, flat-floored, steep sided and contain misfit streams and eskers in their bottoms. | |
| dc.format.extent | 253 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/18917 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Quaternary geology, stratigraphy and applied geomorphology in the southern Nechako Plateau, central British Columbia | en_US |
| dc.type | Thesis | en_US |
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