Sedimentology of the lower Serpukhovian (upper Mississippian) Mabou Group in the Cumberland Basin of eastern Canada: tectonic, halokinetic, and climatic implications

Abstract

The Visean–Serpukhovian transition in Atlantic Canada was marked by a general humidification of the climate as the region drifted towards equatorial latitudes. It also corresponds to a time when ice volume was increasing on Gondwana, which marked the end of Mississippian marine incursions in the region. Glacioeustatic fluctuations of greater magnitude are thought to have increased the response of the regional climate to third-order cyclicity from orbital forcing. In the Cumberland Basin, fluvial grey beds of the lower Serpukhovian Shepody Formation were deposited in sub-humid conditions during highstands, whereas red playa deposits of the same unit were deposited under semi-arid conditions during lowstands. Basin reconstruction suggests that this unit was sourced from the fault-bounded Cobequid and Caledonia highlands and deposited in two separate salt-withdrawal minibasins. This fluvial system was seemingly discharging to the north into the broad lake that deposited the contemporaneous Hastings Formation. A disconformity separates the Shepody Formation from mid-Serpukhovian red beds of the Claremont Formation and is tentatively associated with another increase in ice volume on Gondwana followed by a recrudescence of fault activity and basin subsidence. A prolonged time of aridity, floral crisis, non-deposition, deep weathering and karstification in late Serpukhovian to early Bashkirian times is contemporaneous with abundant glacial deposits in higher latitudes, suggesting that globally low sea levels may have been at play in creating a situation of greater continentality in the study area.

A geomagnetic polarity timescale for the Carboniferous

“…The Brigantian-Pendleian boundary is within the early Serpukhovian (Savastopulo & Barham 2014), like these magnetostratigraphic correlations also suggest. Within the Serpukhovian, the relative duration and pattern of polarity changes is rather different between Tengiz and the Maritimes Basin, which is most likely due to the hiatus detected in the E. Canadian sections, which bound the Shepody and Claremont formations (Jutras et al 2015; Fig. 12).…”

“…early to mid Asbian; Poty et al 2006). Since the Lime-kiln Brook Fm is laterally transitional into the lower part of the Middleborough Fm (Jutras et al 2015), it is possible the oldest part of the magnetostratigraphy (magnetozones NN1-NN2?) may extend into the Asbian rather than be entirely Brigantian.…”

“…may extend into the Asbian rather than be entirely Brigantian. Sedimentological work suggests that the Shepody and Claremont formations (Claremont Fm = Enrage Fm in New Brunswick) are both bounded by hiatus of unknown duration (Jutras et al 2015), so the magnetostratigraphy is possibly fragmented. The magnetozone NN7n may be somewhat thicker than indicated in the polarity composite ( Fig.…”

“…Magnetic polarity data from the Cumberland Basin and Cape Breton Island sections, New Brunswick and Nova Scotia, derived from DiVenere & Opdyke (1990Opdyke ( , 1991b and Opdyke et al (2014). Lithostratigraphy and hiatus in the Cumberland Basin sections from Jutras et al (2015Jutras et al ( , 2016. Magnetozones re-labelled from Opdyke et al (2014) to NN after New Brunswick-Nova-Scotia.…”

“…Magnetozones re-labelled from Opdyke et al (2014) to NN after New Brunswick-Nova-Scotia. It is not clear how the hiatus on the basal Enragé Fm in the Maringouin Peninsula of Jutras et al (2015), relates to the Maringouin Peninsula column data. Sloping boundary on polarity composite= uncertainty in placing the biozone boundary.…”