Diverse and abundant Middle and Late Triassic elasmobranch ichthyoliths (microscopic shark teeth and scales) coexisting with conodonts, ammonoids, and bivalves were recovered from carbonates of the Pardonet, Baldonnel, Ludington, and Liard formations in the Peace River area of British Columbia. These faunas provide an excellent biostratigraphical framework for Triassic strata. Results from this study demonstrate that ichthyoliths can be used in basin analyses to date and correlate strata. The following summarizes the main achievements of this project. 1. Systematic description and illustration of Triassic elasmobranch ichthyoliths include seven species of teeth and nineteen new form genera and fifty-three new form species of scales. 2. Ichthyolith distributions consist of distinct faunal assemblages for the Ladinian, Upper Carnian, and Middle Norian. The Carnian/Norian boundary is marked by the disappearance of many Ladinian and Carnian elasmobranch species. In the Middle Norian, elasmobranch faunas reached a new peak of diversity and abundance. 3. A provisional ichthyolith zonation for the Middle and Upper Triassic is proposed for the Peace River area. The sequence of coeval conodonts and (or) ammonoids indicate that the Coniunctio aequirugosa ichthyolith Zone is Ladinian, the Synechodus multinodosus ichthyolith Zone is Upper Carnian, and the Synechodus incrementum ichthyolith Zone is Lower and Middle Norian. 4. New approaches to ichthyolith identification include recognizing diagnostic characteristics of scale and tooth bases, and using binomial, form, and utilitarian taxonomic systems. 5. Interpretations of histological and morphological features of elasmobranch teeth suggest that more derived neoselachian species than were originally known are present in the Triassic.
Significant advancements in understanding the complex evolution of the Tofino Basin at a convergent accretionary margin are enabled by combining contextual geologic information with new isotopic and paleontological data. A high-resolution Cenozoic chronostratigraphy of the basin is constrained by strontium isotope ages (36.9–1.3 Ma) of Late Eocene to Pleistocene foraminifers together with a revised biostratigraphy (foraminifers and ichthyoliths) from six offshore wells and outcrop samples, new specimen thermal alteration values, and existing well log data. These data are integrated with archival multichannel seismic and magnetic data to interpret offshore well positions with relation to sub-basins and structural highs of the Pacific Rim and Crescent terranes, and other accreted strata. Six regions of the Tofino Basin are defined based on structure and depositional differences during the Eocene to Holocene history of accretion and fragmentation of the Crescent terrane and it underthrusting the Pacific Rim terrane. Subsequent oceanic sediment accretions and deposition of overlying sediments up to about 4000 m thick resulted as the Juan de Fuca plate subducted beneath Vancouver Island. Observations include different fragmentations and landward movements of the Crescent and Pacific Rim terranes in the regions and two fault styles in the Ucluelet and Carmanah regions where six new sub-basins are defined. Results, especially for the Ucluelet and Carmanah sub-basins, indicate periods of deformation during the Late Eocene, Late Oligocene, Middle–Late Miocene, and post middle Pliocene, whereas the Early Oligocene and Early Miocene had periods of relatively slow and less disturbed deposition.
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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.The Micropaleontology Project., Inc. is collaborating with JSTOR to digitize, preserve and extend access to Micropaleontology This content downloaded from 137.99.31.134 on Tue, 21 Jun 2016 05:12:34 UTC All use subject to ABSTRACT: Description and illustration of diagnostic pedicle features play an important role in the identification of elasmobranch scales from the Triassic of northeastern British Columbia. Two main types of scale pedicle are recognized, truncate and tetrahedroid. Morphological changes in the scales including pedicle type, pedicle base and margins, and subcrown ornamentation are observed across the Carnian/Norian boundary. The most useful features of Middle and Late Triassic elasmobranch scales from northeastern British Columbia (B.C.) are described, illustrated, and organized into a hierarchy with divisions of part, supergroup, group, and subgroup. A key which can be used to determine scale subgroup is provided.
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