7 D5. Paleontology and Paleoclimatology (Posters)

Friday, 17 March 2023
8:00 AM - 12:00 PM
Grand Ballroom A–D

THE "TAPHONOMY" OF PYRITE SUNS

Paper number: 7-3
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

  • Brielle Hunt Presenting Author
    Bloomsburg University of Pennsylvania, Bloomsburg, PA
  • Alan Gishlick
    Bloomsburg University of Pennsylvania, Bloomsburg, PA

Abstract

In 2008, Dr. Abderrazak El Albani discovered a series of structures in the 2.1-billion-year-old Franceville Basin in Gabon. The structures were described as the oldest multicellular organisms in the fossil record. However, similar shapes and patterns that led to their identification as putative “fossils” are also seen in the gross morphology of pyrite suns and nodules. The intent of this research is to test if it these fossils were pyrite concretions molded and cast by diagenetic processes leading to reduction in detail to create textures shapes comparable to those the Gabon Biota.

In order to test how the morphologies of pyrite concretions might “preserve” as “fossils,” samples of various shapes and sizes of suns and nodules were purchased. A set of 8 pyrite suns and 17 pyrite nodules were acquired. Most samples of pyrite suns were confirmed to be from Sparta, IL. 15 pyrite nodule samples from Buffalo, NY were acquired directly from the collector, while two were purchased without locality data. All samples were photographed and were sketched noting the morphological and growth patterns that produced their shapes. To test how the shapes of the concretions could preserve as molds and casts, the samples were pressed into kaolinite (pottery) clay (as a simulation of fine-grained sediment), and then cast using Plaster of Paris. When looking at the cast samples, detail loss and reduction was noted throughout the samples. This detail loss and reduction was seen more prominently in the pyrite sun samples. In samples that had secondary pyrite growth, the crystalline cubic pyrite grains were reduced to a grainy/sugary appearance in the casts. The samples with a post-dissolution primary pyrite layer exhibited a loss of detail in the grooves, giving it a ruffled appearance similar to what is seen in Gabon Biota specimens. On all pyrite sun samples, the lobe-like features were accentuated, and the fine radial features were reduced. Studying and understanding the morphology of pyrite suns and other types of pyrite concretions from a taphonomic perspective, the case can be made that the Gabon Biota are not two-billion-year-old fossilized or pyritized multi-cellular organisms but two-billion-year-old pyrite concretions that have had their original material and shapes altered through geologic processes.

Geological Society of America Abstracts with Programs. Vol. 55, No. 2

doi: 10.1130/abs/2023SE-385634

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