Date of Award

8-1998

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

Supervisor

Roger G. Walker

Abstract

This study was undertaken to further understand the interrelationships between the endobenthos and sedimentation. Quantification of ichnospecies abundance and diversity are used to interpret their significanceand the ecologicalconditions two sedimentologically different incised valleyfills. This study is based on cores from two incised valley-fills from the Cretaceous Western Interior Seaway (Alberta). The first, the Waskahigan Channel (Shingle Dl) in the Dunvegan Allofonnation (Cenomanian) interpreted as a migrating delta, contains mud and fine-grained sand. The second, the South Willesden Green Channel (Allomember C) in the Viking Allofonnation (Albian) interpreted as a straight incised valley-fill, contains coarser, reworked marine sand and conglomerates. These differences provide a comparative test for the innovative techniques used herein. TInsresearch provided a tool to interpret changes in sea level and the depositional environment by subtle changes observed in the abundance and diversity of ichnofossil communities and ichnofacies. ill the Waskahigan Bottleneck Channel (7-13-64-24W5), estuarine sand flats are distinguished by the such changes. The assemblages' abundance and diversity increased, then decreased and increased again as the channel infilled. In the South Willesden Green Channel, core IO-35-40-7W5 is interpreted as estuarine bay fill deposit. Without quantitative ichnology, the five successive fills recognized herein would be considered one deposit. In both channels, shells and shell fragments are absent as a result of physical weathering and chemical dissolution. This study contributes methods of ichnological quantification and comparison in subsurface core. TI,e subtle details reveal more information about the ecological conditions during the infilling of these Cretaceous depositional environments.

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