Fluvial Instability In the Paleoequatorial Realm of Atlantic Canada during the Late Carboniferous to Early Permian. A Record of Global Climate Variation?

The Maritimes Basin of Atlantic Canada comprises a series of northeasterly trending intermontane basins that preserve an extremely thick Devonian-Permian basin fill. The late Carboniferous to early Permian alluvial to coastal plain successions within the Maritimes Basin preserve a variety of upper flow regime structures (UFRS) such as plane bedding and antidunes. Successions that preserve abundant UFRS, along with other climate-sensitive features, may point to a paleoclimate where there was a pronounced variation in precipitation and runoff. Within the basin, the distribution of UFRS varies through time. UFRS are preserved within strata during two discrete intervals from the latest Namurian-Westphalian A and from the Westphalian D-early Permian. The distribution of UFRS suggests that there were several pronounced, long-term changes in precipitation and runoff regime during the Late Carboniferous and Early Permian. These intervals coincide with other data including dryland paleosols, floral changes, coal occurrence, etc. that suggest that the paleoclimate of the Maritimes Basin consisted of alternating periods of strongly seasonal climate with pronounced drying and other periods of more ever-wet or less seasonal climate. The fact that these intervals can be correlated between several subbasins of the Maritimes Basin, each with differing tectonic regimes, suggests that these intervals record a regional climatic signal.

These new data combined with the sedimentologic and plant taphonomic data established by previous workers suggests that the paleoequatorial realm records various scales of climatic variation that may be comparable to the scales of variation seen in Gondwanan records. Furthermore, the intervals within the Maritimes Basin that record a strongly seasonal paleoclimate coincide with peak Gondwanan glaciation suggesting synchroneity of global climate shifts in the Late Paleozoic. Transitions from glacial to non glacial climate states may be expressed within the paleoequatorial realm as long-term changes in discharge and runoff in the fluvial record.