107 Sedimentary Geology Division/SEPM Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation

Students (at any level) may present posters of original research on any topics within sedimentary geology: carbonates, clastics, chemical sediments, ancient and/or modern systems. Posters are judged for monetary awards distributed at the reception.

Monday, 20 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Quartz in geodes in the Fort Payne Chert: Evidence for deep burial and hydrothermal conditions

Paper number: 107-7
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

  • Dustin Heese Presenting Author
    Department of Geology, Earth, Energy & Environment Center, University of Kansas, Lawrence, Kansas
  • Claire Marshall
    Department of Geology, Earth, Energy & Environment Center, University of Kansas, Lawrence, Kansas
  • Robert Goldstein
    Department of Geology, Earth, Energy & Environment Center, University of Kansas, Lawrence, Kansas

Abstract

The Mississippian Fort Payne Chert in northeastern Alabama contains megaquartz-lined geodes previously interpreted to have formed from low-temperature surface fluids [1] or during shallow burial diagenesis at ~40 °C [2, 3]. Burial history models and regional paleomagnetic data, however, suggest the area experienced temperatures significantly higher than ~40 °C during Pennsylvanian–Permian burial [4, 5]. To constrain temperature and fluid conditions of megaquartz precipitation, we conducted petrographic and fluid inclusion analyses on ten primary fluid inclusion assemblages (FIAs) from a geode sampled at the Kirbytown, Alabama locality. Fluid inclusion microthermometry included homogenization temperatures (Th), final ice melting temperatures (Tmice), and eutectic temperatures (Te). Pressure corrections were applied using a 26 °C/100 bar thermobaric gradient. Th values range from ~92 °C to ~115 °C in FIAs 1–6, increase to ~130 °C in FIA 7, drop to ~115 °C in FIA 8, and rise again through FIA 9 (~120 °C) to a measured peak of ~150 °C in FIA 10. Tmice values from –2.7 °C to –1.5 °C and Te values near –21 °C indicate low-salinity NaCl solutions (~2.6–4.5 wt.% NaCl eq.) consistent with connate marine origins. These data support an interpretation of progressive megaquartz precipitation during Pennsylvanian–Permian burial under pressure-temperature conditions of ~100 °C to ~140 °C and ~300 to 400 bars, with later-stage quartz growth influenced by localized hydrothermal heating reaching ~140 °C to ~180 °C and ~400 to ~600 bars. These results directly contradict earlier models invoking shallow burial or low-temperature diagenetic formation and instead record a history of deep burial conditions and hydrothermal influence.

 

[1] Bassler, R.S. (1908) The formation of geodes with remarks on the silicification of fossils. U.S. Museum National Proceedings. 35, 133-154.

[2] Milliken, K.L. (1979) The silicified evaporite syndrome- Two aspects of silicification history of former evaporite nodules from southern Kentucky and northern Tennessee. Journal of Sedimentary Petrology. 49, 1, 245-256.

[3] Nolte, R.A., Benson, D.J. (1998) Silica diagenesis of Mississippian carbonates of northern Alabama. Gulf Coast Association of Geological Societies Transactions. 48, 301-310.

[4] Simonis, A. F. (2014) Burial history and thermal maturity of the Chattanooga Shale, northwestern Alabama. Gulf Coast Association of Geological Societies Transactions. 64, 355-370.

[5] Hodych, J. P., Patzold, R. R., Buchan, K. L. (1985) Chemical remanent magnetization due to deep-burial diagenesis in oolitic hematite-bearing ironstones of Alabama. Physics of the Earth and Planetary Interiors. 37, 261-284.

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

doi: 10.1130/abs/2025AM-413261

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.