Sedimentology and taphonomy of storm-generated shell beds from the Verulam formation (Ordovician), Lakefield and Gamebridge quarries, Southern Ontario, Canada /

The Verulam Formation (Middle Ordovician) at the Lakefield Quarry and Gamebridge Quarry, southern Ontario, is comprised of five main lithofacies. These include shoal deposits consisting of Lithofacies 1, winnowed crinoidal grainstones and, shelf deposits consisting of: Lithofacies 2, wackestones, packstones, grainstones, and rudstones; Lithofacies 3, laminated calcisiltites; Lithofacies 4, nodular wackestones and mudstones; and, Lithofacies 5, laminated mudstones and shales. The distribution of the lithofacies was influenced by variations in storm frequency and intensity during a relative sea level fall. Predominant convex-up attitudes of concavo-convex shells within shell beds suggest syndepositional reworking during storm events. The bimodal orientations of shell axes on the upper surfaces of the shell beds indicates deposition under wave-generated currents. The sedimentary features and shell orientations indicate that the shell beds were deposited during storm events and not by the gradual accumulation of shelly material. Cluster and principal component analysis of relative abundance data of the taxa in the shell beds, interbedded nodular wackestones and mudstones, and laminated mudstones and shales, indicates one biofacies comprised of three main assemblages: a strophomenid (Sowerbyelladominated) assemblage, a transitional mixed strophomenid-atrypid assemblage and an atrypid (Zygospira-dominatQd) assemblage. The occurrence of the strophomenid, the strophomenid-atrypid and atrypid assemblages were controlled by storm-driven allogenic taphonomic feedback.

Dinocyst biochronology and palynofacies : inferred systems tract character of Miocene sequences from New Jersey mid-Atlantic transect (ODP legs 174A and 174AX) /

One of the main objectives of the mid-Atlantic transect is to improve dating resolution of sequences and unconfonnity surfaces. Dinoflagellate cysts from two Ocean Drilling Program boreholes, the onshore Leg 174AX Ocean View Site and Leg 174A continental shelf Site 1071, are used to provide age estimates for sequences and unconfonnities fonned on the New Jersey continental margin during the Miocene epoch. Despite the occasional lack of dinocysts in barren and oxidized sections, dinocyst biochronology still offers greater age control than that provided by other microfossils in marginal marine environments. An early Miocene to late Miocene chronology based on ages detennined for the two study sites is presented. In addition, .palynofacies are used to unravel the systems tract character of the Miocene sequences and provide insight into the effects of taphonomy and preservation of palynomorphs in marginal marine and shelf environments under different ~ea level conditions. More precise placement of maximum flooding surfaces is possible through the identification of condensed sections and palynofacies shifts can also reveal subaerially exposed sections and surfaces not apparent in seismic or lithological analyses. The problems with the application of the pollen record in the interpretation of Miocene climate are also discussed. Palynomorphs provide evidence for a second-order lowering of sea level during the Miocene, onto which higher order sea level fluctuations are super-imposed. Correlation of sequences and unconfonnities is attempted between onshore boreholes and from the onshore Ocean View borehole to offshore Site 1071.