Fluvial response to paleo-equatorial climate fluctuations during the late Paleozoic ice age

Abstract

The Maritimes Basin of Atlantic Canada preserves a 12-km-thick stratigraphic succession deposited within a low-latitude, predominantly continental setting during the late Paleozoic. This paper examines the utility of using such successions for paleoclimate analysis, with specifi c reference to changes in fl uvial style. 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 fl ow conditions and the presence of in situ vegetation growing within the channel environment. This fl uvial style is indicative of prolonged low-fl ow conditions punctuated by intense precipitation events in a strongly seasonal climatic setting. Fluvial channel bodies within the Maritimes Basin preserve a remarkably similar style compared with these modern systems, suggesting that a subhumid, strongly seasonal paleoclimate was the dominant imprint on parts of the preserved successions.Strongly seasonal deposits are concentrated within four discrete stratigraphic intervals (E1-E4), ranging in duration from 2 to 6 m.y. These intervals are correlated across the entire basin and between basins characterized by markedly different tectonic regimes, which suggests 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 fl uvial styles implies that several pronounced, long-term changes in precipitation and runoff regimes occurred during the Carboniferous within the 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 Pennsylvanian Springhill Mines Formation: sedimentological framework for a portion of the Joggins Fossil Cliffs UNESCO World Heritage Site

“…In an overview of the regional fluvial sedimentology, Allen et al (2011Allen et al ( , 2013 supported Rust et al's (1984) interpretation of the Springhill Mines Formation as recording a progressive shift from fixed-to meandering-channel bodies. They interpreted fluvial architecture and geometry as being compatible with prevailing interpretations of a (sub)humid seasonal climate during deposition of this unit (Calder 1994(Calder , 1998Falcon-Lang and Scott 2000;Utting et al 2010).…”

“…During relatively dry periods, flora and fauna may have been concentrated close to active channels in a situation similar to the waterhole model described by Falcon-Lang et al (2004). The presence of silicified cordaitalean logs in other Pennsylvanian units has been interpreted as recording increased aridity and/or a shift to better drained inland conditions Allen et al 2011;Ielpi et al 2014).…”

The Joggins Fossil Cliffs UNESCO World Heritage site: a review of recent research

“…A recent study has also reported such structures in the Boss Point and Little River formations (Allen et al 2011). Rygel and Gibling (2006) explored the numerous Joggins Formation channel bodies and their development in terms of intrinsic and extrinsic controls.…”

Impact of continental motion and dynamic glaciations on low-latitude climate during the Carboniferous: The record of the Wyoming Shelf (Western United States)

“…Those intervals of global cooling and warming, fluctuating on time scales of 1 to 10 Myr, are thought to have been controlled by fluctuations in pCO 2 . Several recent studies have investigated the imprint of these dynamic changes of global climate on the low-paleolatitude record (e.g., Feldman et al, 2005;Bishop et al, 2010;Allen et al, 2011;Koch and Frank, 2011;Eros et al, 2012;Martin et al, 2012). In doing so, they noted the challenges entailed in deconvolving the effects of global climate change from those caused by the latitudinal drift of continental masses (Roscher and Schneider, 2006;.…”