Research carried out in the Ediacaran of eastern Newfoundland focused on two projects: sedimentology of the Conception and St. John’s groups exposed on the Bonavista Peninsula; and taxonomic descriptions of the small, stemmed frondose fossils at Mistaken Point on the Avalon Peninsula. Sedimentological study of the upper Conception and lower St. John's groups at Catalina Dome on Bonavista Peninsula extends our understanding of the Conception Basin, in which the oldest known complex, deep marine organisms lived, by a factor of two. Mudstone-rich turbidites dominate the succession, and a lack of wave-generated structures or other shallow-water indicators support the interpretation that the depositional environment was deep-marine. The basal part of the succession contains seismoturbidites that show no evidence of horizontal translation, implying that deposition occurred on a flat basin plain. Strata higher in the succession exhibit horizontally slumped beds, implying a transition into slope deposition. Turbidite ripple marks show a change in paleocurrent direction from eastward to southward in the Trepassey Formation, consistent with a change from convergent to strike-slip tectonics that occurred diachronously across the basin. Volcanic ash beds are more common in the Catalina Dome succession than on the Avalon Peninsula, reflecting deposition closer to the volcanic source. These volcanic beds are associated with diverse fossil assemblages rich in rangeomorphs that locally persist into the Fermeuse Formation, in contrast with the Avalon Peninsula where the Fermeuse Formation contains only simple discoid fossils. This taphonomic window lends support to the hypothesis that the form genus Aspidella represents the holdfasts of Ediacaran fronds. Stemmed small frond fossils from Mistaken Point, Avalon Peninsula, have often been informally referred to as “featherdusters”, but due to their small size and consequent poor preservation, they have not until now been formally described. The small, stemmed fronds are more diverse than previously realized, and include representatives of taxa described from elsewhere in Newfoundland, juveniles of other Mistaken Point fronds, and two new monospecific genera. This biodiversity suggests that the basal elevated tier that the small fronds occupied was competitive, with convergent evolution of frondose taxa showing distinct architecture and constructions, but broadly similar size and shape. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2013-10-30 12:12:23.297

Rangeomorphs are a distinct group of millimeter- to meter-scale soft-bodied macrofossils that are restricted to the latter half of the late Neoproterozoic Ediacaran Period (635Ma- 542Ma). These fossils represent an extinct higher level taxon characterized by a modular construction based on a single architectural unit: the centimeter-scale, chevron-shaped rangeomorph element which displays several orders of self-similar branching. These elements could be arranged in a variety of different ways, constituting the wide array of gross morphologies found within the Group Rangeomorpha. The largest and most diverse assemblage of rangeomorph fossils in the world is found at Mistaken Point, on the Avalon Peninsula of Newfoundland, Canada, where these organisms are preserved within their original, in situ paleocommunities. Multibranched rangeomorphs are typified by bush-, comb- and network-shaped fossils which display multiple rangeomorph-bearing structures attached to an untethered basal stolon or central attachment point. Multibranched, comb-shaped rangeomorphs are endemic to Mistaken Point, and are represented by fossils displaying multiple parallel struts emerging along one side of an elongate, curved pedicle rod. Morphological and taphonomic evidence suggests that, in life, this organism had two rows of struts, each bearing a rangeomorph frondlet, arranged in an alternating pattern along the curved, tubular pedicle rod. Biometric analyses imply that the struts were added to both ends of the pedicle rod throughout the organism’s lifetime, with later inflation of the rangeomorph frondlets. Each comb-shaped rangeomorph locality likely represents a different age cohort within the organism’s lifecycle, providing rare evidence for spatfall reproduction in Ediacarans, which is similar to that found in modern macrobenthic organisms with pelagic larvae. Network-shaped multibranched rangeomorphs, represented by symmetrical to asymmetrical net-like fossils, are also endemic to Mistaken Point. This genus is reconstructed as having a symmetrical arrangement of flexible, rangeomorph-bearing leaflets that were, in part, neutrally buoyant with respect to the seawater. This flexible leaflet structure is unique, and shared only with a rare, previously undescribed, Ediacaran frond-like organism. It is suggested that the enigmatic leaflet structures shared by these two morphologically distinct taxa represent a new type of rangeomorph branching architecture, and therefore constitute a new type of rangeomorph. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2008-07-25 11:01:43.469