68-1 New high-resolution chemo- and bio- stratigraphic records through the Ordovician – Devonian Cape Phillips and Bathurst Island formations (Bathurst Island, Nunavut, Canada)

Session: Climate Transitions in the Paleozoic (Posters)

Poster Booth No.: 157

Presenting Author:

Emily Ellefson

Authors:

Ellefson, Emily¹, Melchin, Michael Jerome², Dewing, Keith³, Arnold, Paige⁴, Haeri Ardakani, Omid⁵, Riemer, Sydney⁶, Gill, Benjamin Charles⁷, Gouwy, Sofie⁸, Leslie, Andrew⁹, Tarhan, Lidya¹⁰, Sperling, Erik A.¹¹

(1) Earth and Planetary Science, Stanford University, Stanford, CA, USA, (2) St. Francis Xavier University, Earth Sciences, Antigonish, NS, Canada, (3) Geological Survey of Canada, Calgary, AB, Canada, (4) Amherst College, Amherst, MA, USA; Earth and Planetary Science, Stanford University, Stanford, CA, USA, (5) Natural Resources CanadaGeological Sur, Calgary, AB, Canada, (6) Yale University, New Haven, CT, USA, (7) Virginia Tech, Blacksburg, VA, USA, (8) Geological Survey of Canada, Calgary, AB, Canada, (9) Stanford University, Stanford, CA, USA, (10) Yale University, New Haven, CT, USA, (11) Stanford University, Stanford, CA, USA,

Abstract:

The Silurian – Devonian transition is a critical interval in Earth history and a time of profound change. To generate new integrated stratigraphic and paleontological records across the Silurian – Devonian transition, deep-water slope sediments comprising the shale-rich Silurian – Devonian Cape Phillips and Bathurst Island formations (Grant Point, Bathurst Island, Nunavut, Canada) were studied. This section has received little previous attention but based on regional biostratigraphic and thermal maturity studies was expected to have a relatively complete graptolite record and be relatively thermally immature. Here we present new graptolite biostratigraphy and the occurrences of other fossil organisms, carbon isotope chemostratigraphy and total organic carbon (TOC), and programmed pyrolysis data from Grant Point.

Starting in the Katian (Upper Ordovician) almost all Ordovician – Devonian global graptolite biozones are recorded in the Grant Point succession, providing excellent biostratigraphic age control in the section. The only exceptions to this are the intervals of the Hirnantian – Aeronian and upper Telychian stages that are likely covered intervals of this section. Most major Silurian – Devonian carbon isotope excursions have also been identified in the section allowing for comparison of chemostratigraphic and biostratigraphic data and correlation to other successions. Preliminary TOC abundances appear to co-vary with positive organic carbon isotope excursions. Programmed pyrolysis data indicate that the section falls primarily within the window of peak oil generation. Beyond graptolites, brachiopods, fish, eurypterids, orthocerids, tentaculitids, and plant macrofossils were also documented in the section. This marks the second locality on Bathurst Island where Lower Devonian plant macrofossils have been recorded. The plant fossils in the Grant Point section are associated with turbidite and slump deposits as well as some of the highest measured TOC values in the succession. Ultimately, this section will allow for direct integration of paleoenvironmental and geochemical data and represents an unparalleled opportunity to study the early and mid-Paleozoic Earth system.

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

doi: 10.1130/abs/2025AM-9498

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