Integrated modeling for stratigraphic development of the Mackenzie Trough and the Eastern Beaufort Shelf, N.W.T., Canada




Picard, Kim

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Glaciated shelves develop under the influence of a more complex suite of processes than most non-glaciated shelves. Amongst the specific processes are the glacially-influenced sediment supply and the glacial-isostatic adjustment (GIA), which is largely responsible for the complex nature of regional relative sea-levels (RSLs). This study first characterizes the impact of GIA on the Mackenzie-Beaufort region by presenting a new set of RSL curves derived from a modern gravitationally self-consistent sea level model computing the effects of glacio-hydro isostasy, geoid changes, and true polar wander. The results of the RSL model present cross-shelf variations in the order of 100 m and along-shelf of 30 m during the LGM. The model also suggests a different timing and range to the single RSL curve presently used for this region. Depending on the location, the lowstand is modeled between 14 and 12 ka BP and reached between 85 and 140 m below present sea-level. These new findings are used in the second part of the study to evaluate the impacts of GIA along with other factors on the Late Quaternary evolution of the Canadian Beaufort Shelf. SedFlux, a process-based stratigraphic simulation model is used. Uncertainties associated with post-LGM conditions create difficulties in establishing good model parameterization. Thus, simulations are first performed on the Mackenzie Trough area, where data availability permits better evaluation and constraint of parameters that are then applied to the more data poor Eastern Beaufort Shelf environment. The results of the stratigraphic simulations suggest that the ice sheet margin in the Mackenzie-Beaufort region was more extensive than previously assumed. The impact of GIA on the stratigraphy of the Mackenzie Trough is to develop more progradational than retrogradational stratigraphic features. Simulations of the Eastern Beaufort Shelf suggest that a previously dated sample from the Uviluk borehole is not a RSL indicator as previously thought and by taking this into consideration, the borehole stratigraphy can be modeled. Modeling of multiple cycles of glacial/interglacial RSL with glacial outwash deposition supports the interpretation of the Late Quaternary geology suggested by Murton (2009). Finally, glacial outburst floods funnelling through the area would have mostly bypassed the shelf and contributed to its progradation. If flood water were directed to the Mackenzie Trough, the deposits are likely found within the lower wedge.



Arctic, Eastern Beaufort Shelf, Stratigraphy, geology, stratigraphic simulation model, sedflux, glacio-isostatic adjustment, relative sea-level, Mackenzie Trough, Mackenzie River Delta, marine, Canada