LE3 .A278 2016

2016

Kristie, David

Acadia University

Master of Science

Masters

Geology

Earth & Environmental Sciences

Subzone B of the middle Viséan Windsor Group (ca. 345Ma), Maritimes Basin, Canada, consists of brining - upward peritidal cycles that accumulated in an intracratonic basin under icehouse conditions. Lithofacies stacking patterns indicate Subzone B records deposition during a sea level lowstand at the onset of transgression. Superimposed, higher - order fluctuations in relative sea level produced nine stacked parasequences that are interpreted to reflect high frequency glacioeusta ticoscillations that punctuated the Late Paleozoic Ice Age. These decameter - scale, aggradational peritidal cycles are composed of up to ten lithofacies whose stacking records increased restriction and salinity during deposition. Cycles are defined by flooding surfaces overlain by subtidal fossiliferous or evaporite - rich lime mudstone that brine upwards into massive anhydrite or layered halite. Evaporite beds are overlain by flaser - bed ded sandstone, microbialite, and nodular anhydrite. Cycles terminate with terrestrial red beds or a karst diastem developed in underlying anhydrite. Each parasequence reflects progradation of intertidal and sabkha environments over subtidal carbonate and evaporite deposits. Dissimilarities in cycle composition between sub-basins implies the development of contrasting brine chemistries as a consequence of differing recharge rates with the Rheic Ocean. These aerially restricted peritidal evaporites of Sequence 2 are markedly different than the underlying basinwide evaporites of Sequence 1. What Subzone B reveals is that evaporite type is dire ctly linked to the amplitude and frequency of sea level rise and fall during deposition. True saline giants apparently require low amplitude, long frequency changes in sea level, whereas platform evaporites with more complex facies relationships are the result of high amplitude, short frequency variability in sea level.

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https://scholar.acadiau.ca/islandora/object/theses:1390