John William Dawson

Bio: John William Dawson is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 96 citations.

The Carboniferous evolution of Nova Scotia

Abstract: Abstract Nova Scotia during the Carboniferous lay at the heart of palaeoequatorial Euramerica in a broadly intermontane palaeoequatorial setting, the Maritimes-West-European province; to the west rose the orographic barrier imposed by the Appalachian Mountains, and to the south and east the Mauritanide-Hercynide belt. The geological affinity of Nova Scotia to Europe, reflected in elements of the Carboniferous flora and fauna, was mirrored in the evolution of geological thought even before the epochal visits of Sir Charles Lyell. The Maritimes Basin of eastern Canada, born of the Acadian-Caledonian orogeny that witnessed the suture of Iapetus in the Devonian, and shaped thereafter by the inexorable closing of Gondwana and Laurasia, comprises a near complete stratal sequence as great as 12 km thick which spans the Middle Devonian to the Lower Permian. Across the southern Maritimes Basin, in northern Nova Scotia, deep depocentres developed en echelon adjacent to a transform platelet boundary between terranes of Avalon and Gondwanan affinity. The subsequent history of the basins can be summarized as distension and rifting attended by bimodal volcanism waning through the Dinantian, with marked transpression in the Namurian and subsequent persistence of transcurrent movement linking Variscan deformation with Mauritainide-Appalachian convergence and Alleghenian thrusting. This Mid-Carboniferous event is pivotal in the Carboniferous evolution of Nova Scotia. Rapid subsidence adjacent to transcurrent faults in the early Westphalian was succeeded by thermal sag in the later Westphalian and ultimately by basin inversion and unroofing after the early Permian as equatorial Pangaea finally assembled and subsequently rifted again in the Triassic. The component Carboniferous basins have provided Nova Scotia with its most important source of mineral and energy resources for three centuries. Their combined basin-fill sequence preserves an exceptional record of the Carboniferous terrestrial ecosystems of palaeoequatorial Euramerica, interrupted only in the mid-late Viséan by the widespread marine deposits of the hypersaline Windsor gulf; their fossil record is here compiled for the first time. Stratal cycles in the marine Windsor, schizohaline Mabou and coastal plain to piedmont coal measures ‘cyclothems’ record Nova Scotia’s palaeogeographic evolution and progressively waning marine influence. The semiarid palaeoclimate of the late Dinantian grew abruptly more seasonally humid after the Namurian and gradually recurred by the Lower Permian, mimicking a general Euramerican trend. Generally more continental and seasonal conditions prevailed than in contemporary basins to the west of the Appalachians and, until the mid-Westphalian, to the east in Europe. Palaeogeographic, paleoflow and faunal trends point to the existence of a Mid-Euramerican Sea between the Maritimes and Europe which persisted through the Carboniferous. The faunal record suggests that cryptic expressions of its most landward transgressions can be recognized within the predominantly continental strata of Nova Scotia.

The Pennsylvanian tropical biome reconstructed from the Joggins Formation of Nova Scotia, Canada

Abstract: The Pennsylvanian (Langsettian) Joggins Formation contains a diverse fossil assemblage, first made famous by Lyell and Dawson in the mid-19th century. Collector curves based on c . 150 years of observation suggest that the Joggins fossil record is relatively complete. A key feature of the site is that fossils occur in (par)autochthonous assemblages within a narrow time interval (

Vegetation‐induced sedimentary structures from fossil forests in the Pennsylvanian Joggins Formation, Nova Scotia

Abstract: Vegetation-induced sedimentary structures (VISS) are primary structures formed by the interaction of detrital sediment with in situ plants. VISS provide physical evidence of vegetation's fundamental role in mediating sediment accumulation and erosion in clastic depositional systems. Despite the abundance of modern VISS, descriptions from the ancient record are surprisingly rare. Analysis of fossil forests in floodplain strata of the Pennsylvanian Joggins Formation has identified seven types of VISS. Five hydrodynamic types comprise simple forms developed around a single plant (centroclinal cross-strata, scratch circles, upturned beds) and complex forms where structures have amalgamated between several plants (coalesced scour fills, scour-and-mound beds). Two types (mudstone-filled hollows, downturned beds) form by the decay of an entombed plant and represent infilling of an empty hollow and/or soft-sediment deformation. Hydrodynamic types are present in both dryland and wetland settings, whereas decay-related types occur only in dryland settings where the water table was perennially or periodically low. VISS represent significant accumulations of sediment and are present in a high proportion of Joggins Formation strata. The paucity of descriptions from the ancient record suggests that these structures have been overlooked or misinterpreted as strictly hydrodynamic. Recognition of VISS in early to middle Palaeozoic strata may provide an important insight into the distribution of early land plants in oxidizing environments where organic material was not preserved.

Carboniferous nonmarine invertebrate ichnocoenoses from southern New Brunswick, eastern Canada

Abstract: Nonmarine strata of the Lower Carboniferous Albert Formation of southern New Brunswick, eastern Canada, contain relatively diverse and abundant invertebrate trace fossils comprising twelve ichnogenera, fourteen ichnospecies, and one vernacular ichnotaxon. These traces occur in two mutually exclusive, spatially and temporally recurrent ichnocoenoses, each related to specific paleoenvironments. The Rusophycus ichnocoenosis characterizes upper portions of upward‐fining fluvial channels and comprises ichnotaxa reflecting different behavioral activities of arthropods. The Palaeophycus ichnocoenosis characterizes shallow lacustrine sequences and comprises ichnotaxa produced essentially by deposit‐feeding invertebrates, possibly annelids (?oligochaetes). Exclusion of ichnofaunas from strata of additional and similarly intergradational paleo‐environmental regimes within the sequence (alluvial fan, alluvial plain, algal swamp, deep lacustrine, evaporitic lacustrine) is suggested to reflect several physical environ...