Stratigraphy and sedimentology of post-windsor group redbeds, Sussex area, New Brunswick

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University of New Brunswick


The area around Penobsquis, east of Sussex, New Brunswick, is an important location of natural resources for the province. In this area, strata of the Mississippian Horton Group produce natural gas whereas younger strata of the Windsor Group are host to major potash and rock salt deposits. Overlying these units are more than 1 km of poorly understood strata, mostly redbeds currently assigned to the Mississippian Mabou Group. To date, no significant marker beds have been identified in the redbeds and there has been no useful biostratigraphic recovery, despite recent extraction of close to 5 km of drill core. Research on these cores broadly identifies siltstone and sandstone at the base of the redbed succession that gradually coarsen up into conglomerate. The succession is considered the result of alluvial fan progradation from the northeast. Within this succession, in many of the cores, is a single interval of localized, horizontally laminated to cross-stratified, bluish grey sandstone, containing carbonaceous plant fragments and siltstone intraclasts. To assess the importance of this interval in the context of the redbed succession, a total of 131 samples of cores from three boreholes have been analyzed using inductively coupled plasma and inductively coupled plasma mass spectroscopy techniques to determine a chemostratigraphy. Study of various elemental ratios delineates two packages, one that corresponds to the grey interval and overlying redbeds, the other to the underlying redbeds. Changes in the elemental ratios are interpreted to mark a broader population of mineral species related to greater variation of provenance and diagenesis in the upper sediment packages. The rip-up clasts may have been produced by sediment reworking along a boundary that represents an unconformity (in cores, a disconformity).