An Early Pennsylvanian waterhole deposit and its fossil biota in a dryland alluvial plain setting, Joggins, Nova Scotia

• Published in: Journal of the Geological Society Vol. 161; no. 2; pp. 209 - 222
• Main Authors: Falcon-Lang, H. J, Rygel, M. C, Calder, J. H, Gibling, M. R
• Format: Journal Article
• Language: English
• Published: London Geological Society of London 01.03.2004; The Geological Society of London; Geological Society; Geological Society Publishing House
• Subjects: arid environment; Bivalvia; Canada; Carboniferous; channels; Chordata; clastic rocks; depositional environment; Earth sciences; Earth, ocean, space; Eastern Canada; Ecosystems; Exact sciences and technology; fluvial environment; Freshwater; Gastropoda; Geology; Hebert Beds; Invertebrata; Invertebrate paleontology; Joggins Formation; Joggins Nova Scotia; Lower Pennsylvanian; Lycopsida; Maritime Provinces; Mollusca; Nova Scotia; outcrops; Paleobotany; Paleoecology; paleogeography; Paleontology; Paleozoic; Pennsylvanian; Plantae; Pteridophyta; red beds; sedimentary rocks; Sphenopsida; Stratigraphy; terrestrial environment; Tetrapoda; tropical environment; Upper Carboniferous; Vertebrata; Canada; Nova Scotia; Maritime Provinces; Eastern Canada; Nova Scotia Canada; Pennsylvania; Australia; Canada, Nova Scotia, Joggins; arid environment; palaeoecology; Upper Carboniferous; terrestrial environment; alluvial plains; mollusks; Cordaites; Chordata; drainage patterns; Gastropoda; gastropods; North America; wetlands; fossil assemblages; Tetrapoda; tetrapods; gymnosperms; Plantae; Carboniferous; Pennsylvanian; bivalves; Paleozoic; Vertebrata; fires; paleoecology; channels; upper Paleozoic; ecosystems; Spermatophyta; Cordaitales; Invertebrata; Mollusca; biostratigraphy
• ISSN: 0016-7649; 2041-479X
• DOI: 10.1144/0016-764903-109

The terrestrial ecology of Pennsylvanian tropical wetlands is understood in detail, but coeval dryland ecosystems remain highly enigmatic. To fill this gap in our knowledge, a Pennsylvanian (Langsettian) continental red-bed succession was studied at the classic Joggins locality, Nova Scotia. These units represent the deposits of seasonally dry, alluvial plains traversed by anastomosed drainage networks. One channel complex informally known as the "Hebert beds" (the focus of this study) contains an unusual fossil assemblage and is interpreted as an alluvial waterhole deposit that formed following drought-induced cessation of channel flow. Adpressed and charred fossil plant remains indicate that the alluvial plain surrounding the waterhole was covered by fire-prone cordaite vegetation, with hydrophilic lycopsids and sphenopsids restricted to waterlogged riparian niches. Gigantic unionoid freshwater bivalves, locally in life position, and occurring in large numbers in the waterhole, were probably infaunal suspension feeders during periods of fluvial activity, but aestivated in channel bottom muds when flow ceased. Abundant terrestrial gastropods found clustered around fossil plant detritus may have been deposit feeders scavenging dry portions of channel floors. Common partially articulated remains of small to medium-sized tetrapods possibly represent animals drawn to the waterhole during drought when surface water was scarce elsewhere. In terms of both sedimentology and biology, the Hebert beds alluvial complex bears a very close similarity to the seasonal drainages and waterholes of present-day central and northern Australia. This unique deposit sheds significant new light on the nature of Pennsylvanian dryland tropical ecology.