The Carboniferous evolution of the Maritimes Basin complex, Atlantic Canada

The Maritimes Basin complex of Atlantic Canada preserves a thick stratigraphic succession deposited within a low-latitude, predominantly continental setting during the Late Paleozoic. This study examines the utility of using such successions for paleoclimate analysis, with specific reference to changes in fluvial style. Traditionally, studies concerning the paleoclimate of continental strata have been limited to analyses of paleopedologic, geochemical proxy, and floral data. The Carboniferous succession of Atlantic Canada is excellently exposed in coastal cliffs and intertidal platforms allowing for a detailed examination of fluvial style and paleoclimate variation. Modern rivers in the subhumid and semiarid tropics preserve a suite of features that are distinct from those in humid and arid environments. These features include an abundance of sedimentary structures formed under Froude transcritical to supercritical flow conditions and the presence of in situ vegetation growing within the channel environment. This fluvial style is indicative of prolonged low-flow conditions punctuated by intense precipitation events in a strongly seasonal climatic setting. Fluvial channel bodies within the Maritimes Basin complex preserve a remarkably similar style compared with these modern systems suggesting that a subhumid, strongly seasonal paleoclimate was the dominant imprint on the preserved successions. Strongly seasonal deposits are concentrated within four discrete stratigraphic intervals (E1-E4), ranging in duration from 2-6 m.y. These intervals are correlated across the entire basin complex and between basins characterized by markedly different tectonic regimes, which indicates that a coherent regional climate signal is recorded. Intervals are separated by deposits characteristic of humid and arid river systems, and the alternation between these different fluvial styles implies that several pronounced, long-term changes in precipitation and runoff regimes occurred during the Carboniferous within region. Furthermore, these intervals broadly coincide with major periods of southern hemisphere glaciation, which suggests that glaciation had a profound and controlling effect on paleotropical climate. The recognition of punctuated periods of strongly seasonal paleoclimate represented by the newly described fluvial style may aid in refining the paleoclimate evolution of similar successions elsewhere in the paleotropics