292-2 Localized Views of a Global Event: Abundance and Diversity of Skeletal Animals through the Great Ordovician Biodiversification Event, Middle Ordovician Table Point Formation, Western Newfoundland

Session: Life and Environments Through Time and Space: Multi-Record Approaches to Stratigraphic Paleobiology, Part II

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Abstract:

The early Paleozoic saw a significant and dramatic increase in marine faunal biodiversity and ecospace occupation, known at the Great Ordovician Biodiversification Event (GOBE), that took place 485 to 460Ma. Here we report results from a high-resolution biodiversity study of the Middle Ordovician Table Point and Table Cove formations of the Table Head Group in western Newfoundland. This expansive 300 meter section, sampled at two-meter intervals, captures the transition from the shallow marine Table Point Formation to the deeper-water Table Cove Formation, providing a window into seafloor diversity and carbonate factory evolution across a range of depositional settings during the GOBE. Distinct meter-sized, sponge bioherm mounds occur ~110 meters above the base of the section in a series of beds. Near the top of the Table Point, a larger-scale sponge biostromal unit occurs with abundant sponges and meter-scale cephalopods are visible on bedding planes. This biostromal unit extends from meter 206 to 236, ending just below the transition to the deeper-water Table Cove Formation.

Thin sections were point counted for non-skeletal and skeletal grains, which were identified to the highest taxonomic level possible, with sponges, gastropods, and echinoderms among the most abundant fossil components. Our point count dataset reveals a few notable patterns: (1) The abundance and diversity of skeletal organisms through the Table Point Formation varies with changes in the local environment. (2) Near the top of the unit, the sponge biostrome preserves some of the highest abundance of skeletal organisms in the entire Table Point section and includes abundant sponges, the enigmatic calcifier Nuia, and Halysis, a calcareous microfossil putatively assigned to red coralline algae. (3) The deeper water Table Cove Formation contains fewer skeletal organisms than the underlying Table Point Formation, likely reflecting environmental change associated with deepening. The examination of the Table Point and Table Cove formations highlights the importance of local influences on manifestations of the diversification and increase in skeletal abundance associated with the GOBE in eastern Laurentia and are key to understanding how the GOBE both occurs in and is influenced by environmental settings across the globe.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9172

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