Silica diagenesis in Eocene carbonates of the Ok¸ular Formation, Turkey: inferences from field observations and petrography

Silicification in Eocene Carbonates

Authors

  • Meryem Yeşilot Kaplan İskenderun Technical University

DOI:

https://doi.org/10.7306/gq.1803%20

Keywords:

chert, diagenesis, SEM-EDS, stylolite, carbonates

Abstract

The silica diagenesis of limestones depends on the environmental conditions and the presence of a silica source. Microstructural features, cracking, porosity, crystal/grain size and the chemical composition of the limestones and chert nodules and layers in the Okçular Formation are parameters controlling silica diagenesis. Cherts are observed in three forms (1) chert nodules with/without a rim, (2) fractured cherts, and (3) layered cherts. Authigenic quartz crystals, chertified foraminifers, microlaminations in the limestones and the chert-limestone grain size relation indicate diagenetic replacement. There is a positive correlation between the size of the microquartz crystals and the colour of the cherts, according to fluid circulation, the trace element content, and the degree of silicification. As the size of microquartz crystals increases due to all these factors, the colour changes from brown to grey-black. Crack widening due to nodule growth, the generally parallel arrangement of chert nodules in carbonates to cracks, and the presence of diagenetic stylolites indicate that both tectonic and diagenetic fractures played a role in silicification. The presence of Cl, P, Ti, Mn and Mo in the chertified zones in limestones indicates inorganic silicification in a marine environment

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Published

2025-10-21

Issue

Vol. 69 No. 3 (2025)

Section

Articles

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