Deconvolving Tectonic and Climatic Influences Within the Fluvial Record: from Example from the Late Carboniferous Succession of the Cumberland Basin, Atlantic Canada

Jonathan P. Allen¹, Christopher R. Fielding¹, Michael C. Rygel², and Martin R. Gibling^3
1Geosciences, University of Nebraska-Lincoln, Lincoln, NE
²Geology, SUNY Potsdam, Potsdam, NY
³Earth Sciences, Dalhousie University, Halifax, NS, Canada

The Late Carboniferous succession of the Cumberland Basin provides an ideal study area in which to examine the influences of both tectonic and climatic controls on fluvial style. The basin has a complex tectonic history which can be summarized by extension (Visean-Namurian), transpression-transtension with episodic downdrop along basin-bounding faults (mid-late Namurian), major halokinesis (Westphalian A-B), and finally thermal sag (Westphalian B-Permian). Research has suggested that the contrasts in fluvial architecture and tectonic conditions between formations were controlled by the manner and rate of basin subsidence. However, to date there has been little insight into what, if any, influence climate has had on fluvial styles.

Alluvial to coastal plain successions within the Cumberland Basin preserve a variety of upper flow regime structures (UFRS) such as plane bedding and antidunes. These structures record sediment accumulation under highly variable discharge regimes. 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. UFRS account for a significant proportion of the internal sedimentary structures within fluvial bodies of the Little River (Westphalian A) and Cape John (Stephanian-early Permian) Formations. The distribution of UFRS suggests that there were several pronounced, long-term changes in precipitation and runoff regime during the Late Carboniferous in the Cumberland Basin. These intervals coincide with other data including dryland paleosols, floral changes, coal occurrence, etc. that together point towards a pronounced seasonal paleotropical climate during these times. These periods also coincide with peak Gondwanan glaciation suggesting synchroneity of global climate shifts in the Late Paleozoic.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas