Allostratigraphic interpretation of a modern coarse clastic barrier complex: Depositional facies, processes and relative sea level relationships.

摘要

This thesis presents an allostratigraphic and facies interpretation of the modern coarse clastic Flat Island barrier complex, situated on the tectonically-structured southern margin of St. George's Bay, western Newfoundland, Canada. The study is based on an integrated geological, geophysical and oceanographic dataset, including aerial photography, multibeam sonar bathymetry data, shallow reflection seismic data, seabed samples, seabed video, wave and current measurements, cores, and pit and outcrop observations.; The Flat Island barrier complex evolved under the influence of a cyclic relative sea level regime associated with post-glacial eustatic sea level rise and superimposed isostatic uplift. The stratal architecture of the barrier complex reflects the inter-relationships of eustatic rise, isostatic uplift, basin physiography, and local sediment supply variations. The barrier complex comprises a four-part stratigraphic succession (Units A--D) delineated by key bounding discontinuities (BD1--BD5).; The lower-most marine allostratigraphic unit (A) consists of aggradational, fine-grained glaciomarine sediments deposited during late-glacial ice recession, which was accompanied by marine onlap of isostatically depressed terrain. Unit A is bounded below and above by "initial" and "maximum" transgressive surfaces, respectively (bounding discontinuities BD1 and BD2).; Maximum coastal onlap (∼13.5 kyBP) was followed by forced regression, as isostatic uplift ensued and exceeded the rate of ongoing eustatic sea level rise. Forced regression led to the development of a subaerial unconformity (BD3) as fluvial channel systems sought progressively lower base levels, locally incising the maximum transgressive surface (BD2).; Isolated delta bodies (Unit B), graded to (present-day) elevations of approximately +26m to -25m, are interpreted as accretionary forced regression deposits. Delta growth occurred during periods of slow forced regression (possibly related to eustatic pulses), accompanied by high rates of glacio-fluvial sediment supply. The subaerial unconformity (BD3) truncates and incises the top of Unit B delta deposits, which downlap the marine maximum transgressive surface (BD2). (Abstract shortened by UMI.)