Graduate Thesis Or Dissertation
 

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8049g970w

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  • The western part of the Late Cretaceous Nanaimo Basin is exposed on Vancouver Island at Nanaimo, British Columbia. The five lowest members of the Nanaimo Group are present and represent a complete sedimentary cycle. The two lowest formations, the Comox and Haslam, represent the marine part of the cycle. The Comox rests with angular unconformity on the underlying Triassic Karmutsen volcanics, and is composed of shallow marine deposits of sandstones, conglomerates and limestones, one of the limestones being an algal type not previously reported for the Nanaimo Basin. The Haslam represents a quiet marine environment, possibly lagoonal, which grades upward into a swampy environment represented within the lower Extension Formation. The Extension Formation represents the first of the terrestrial part of the cycle. Above the Wellington Coal Member, deposited in a swampy environment, lie channel conglomerates and sandstones indicative of a braided stream environment. The Newcastle Formation onlaps the Extension Formation and is composed of sandstones, siltstones, conglomerates, and the Newcastle and Douglas Coal Seams. The environments of deposition of the Newcastle Formation are postulated to be the upper floodplain of a short headed stream. Paleocurrent data and composition of the rocks indicate sources to the west. The Protection Formation is the uppermost of the formations in the area, and is composed of thick- and thin-bedded sandstones. The sandstones indicate a barrier-beach complex, probably deposited as the paleo-shoreline migrated west during a transgression. Subsequent faulting, and fluvial and glacial erosion produced the present topography of the area.
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file details Plate_2.jpg 2017-10-25 Pubblico Scaricare