Laura‑Ann Broom
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1st Class Honours, ERTH & BIOL
B.Sc. (Honours) Thesis
The diversity of life in braided river systems during the Late Triassic at Burntcoat
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Braided-fluvial deposits of the Late Triassic Wolfville Formation at Burntcoat Head have yielded important vertebrate bone material. The present study integrates fluvial sedimentology with paleobiology to gain a more complete understanding of the paleoenvironment and paleoecology. The Wolfville Formation was deposited within the extensional Fundy Basin during the break up of Pangaea. The 34 m studied section comprises channel bodies up to 5 m thick stacked to form three channel belt complexes with planar bases, up to 11 m thick. The channel deposits comprise thin lags of mudclast conglomerates, coarse- to fine-grained sandstones, interpreted as bedload deposits of bars and channel fills, and floodplain deposits that include pedogenically modified fine sandstones and claystones with carbonate nodules. Architectural elements include laminated sand sheets, lateral and downstream accretion macroforms, and sandy bedforms. Plane-bedded sandstones and trough cross-beds, formed by large dunes are prominent in the section. Paleoflow was near parallel to the cliff line with an average direction of 057°.
Reworked partial skeletons and bone and teeth fragments reveal a diversity of vertebrates. Collections at the NS Museum of Natural History yielded over 75 specimens from the area, some specific to the studied interval. Bone fragments of tetrapods range from a few mm to over 20 cm in length and were found as clasts within fine- to coarse-grained sandstone. Recent discoveries from the site include the partial skeleton of an archosauromorph reptile, Teraterpeton hrynewichorum, and procolophonid reptiles including Acadiella psalidodon, Haligonia bolodon, and Scoloparia glyphanodon. Trace fossils transitional between Taenidium and Planolites are locally abundant within channel sandstones and floodplain fine sandstones and claystones. Plant fossils were not observed, but possible vegetation-induced sedimentary structures were documented, and this along with the presence of herbivores suggests the presence of vegetation in the area.
The fluvial deposits formed near the paleoequator in a semi-arid climate with seasonal rainfall and high discharge, as indicated by thick plane-bedded sandstones, the abundance of scoured surfaces, and carbonate paleosols. Early calcite cements suggest a bicarbonate-charged groundwater system, and the angular nature of clasts indicates a proximal source and rapid deposition. Known localities of bone material are linked to the base of channel fills and in-channel dunes and the fragmentary and isolated nature of the specimens suggest considerable transport. Burrows indicate that invertebrates were active in channels during periods of abandonment and in floodplain deposits. The variety of specimens and biological material indicates that life flourished along these Triassic braided channels.
Keywords: Burntcoat Head, Wolfville Formation, braided rivers, taphonomy, paleoecology, diversity, semi-arid, reptile
Pages: 77
Supervisors: Martin Gibling / Tim Fedak