Del Piero, N, Riguad, S, Takahashi, S et al. (2 more authors) (2020) Unravelling the paleoecology of flat clams: new insights from an Upper Triassic halobiid bivalve. Global and Planetary Change, 190. 103195. ISSN 0921-8181
Abstract
Flat clams are ubiquitous in marine Triassic and Jurassic deep-water environments, where they are often recovered as mono- or pauci-specific assemblages. Their abundance in deep-water facies deposited under oxygen-depleted conditions suggests a potentially unique, but nevertheless debated, paleoecology. The distribution of Halobia cordillerana in an Upper Triassic hemipelagic succession outcropping at Tsiko Lake, Vancouver Island, Canada, serves as a revealing case study. There, deep-water deposits were investigated using a multi-disciplinary approach including facies description (mineralogical, fossil and organic content), taphonomy, morphometry, microscopy (cathodoluminescence, scanning-electron microscope) and independent paleo-redox proxy constraints (framboidal pyrite distributions, Fe speciation). Overall, halobiids' taphonomy at Tsiko Lake is indicative of in situ accumulations with little or no reworking. Among the hemipelagic deposits, three major litho-biofacies (BFC 1, 2, 3) were identified; paleo-redox proxies indicate that these litho-biofacies were deposited under different oxygen conditions ranging from extreme dysoxic (BFC 1) to dominantly euxinic (BFC 3). The distribution of H. cordillerana is shown to be directly influenced by bottom water oxygenation with this organism peaking both in abundance and dimensions under extreme dysoxic to anoxic conditions (i.e. BFC 1 & 2). Conversely, under prevailing euxinic conditions (i.e. BFC 3), the population of H. cordillerana is dominated by forms at larval or post-larval stage which were presumably killed by water-column euxinia. Thus, although the species is here shown to have lived most likely as an epibenthic recliner, an early (larval) planktonic/nektonic stage is needed to explain its mode of occurrence during dominantly euxinic conditions (i.e. BFC 3), and its wide distribution and rapid expansion. Finally, this study highlights the colonizing capacity of halobiids in case of restored oxygen conditions, stressing the potential significance of flat clams for paleoenvironmental reconstruction.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 Published by Elsevier B.V. This is an author produced version of a paper published in Global and Planetary Change. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Upper Triassic; Flat clams; Halobiid bivalves; Paleoecology; Paleo-redox; Paleoenvironment |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 20 Apr 2020 13:44 |
Last Modified: | 19 Apr 2021 00:38 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.gloplacha.2020.103195 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:159646 |
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