141 New Advances in Geobiology
This session will focus on new research at the intersection between geologic and biologic processes with special emphasis on novel materials and methods, new field sites, and advances at the intersections of scientific fields.
Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 305
Problematic cylindrical microbially-influenced sedimentary structures of the Tonian Chichkan Formation, Kishi (Lesser) Karatau, Kazakhstan
Paper number: 141-2
Program: Technical Sessions
Time: 1:50 PM – 2:05 PM
Authors
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Sezim MustapayevaSatbayev University, Almaty
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Yerkhozha MamanovSatbayev University, Almaty
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Aibolat TalgatbekovSatbayev University, Almaty
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Sabrina KhanJohns Hopkins University, Baltimore, MD
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Emily SmithJohns Hopkins University, Baltimore, MD
Abstract
The late Tonian Chichkan Formation of southern Kazakhstan is remarkable for its well-preserved chert-permineralized microfossil assemblage, but it also hosts interesting macro-scale bio-sedimentary features. These include silicified, putatively microbially-influenced sedimentary structures of a unique and problematic laminated cylindrical morphology. In this study, we perform a critical examination of these structures and associated sedimentary features, using sedimentological and stratigraphic observations from outcrop to micro-scales to constrain their depositional context and test hypotheses about their origin and paleoenvironmental meaning. Ultimately, we find that the presence of bent (flexibly deformed) and broken (brittlely deformed) silicified laminae and intraclasts, combined with intercalated silts and fine sands, imply an intertidal-to-peritidal depositional setting. We find that the problematic structures’ 3D and cross-sectional geometry, grouping, orientation, and size distribution are inconsistent with their interpretation as stromatolites, roll-up structures, or oncoids. We instead propose a formation mechanism wherein cohesive microbial mats in an intertidal marine environment, characterized by variable siliciclastic sediment input and episodic changes in wave energy and water depth, accreted sediment and organic material around cylindrical masses whose shoreline-parallel orientation and shoreline-perpendicular motion was maintained by bidirectional flows (tides). We also suggest an alternative nomenclature consistent with this formation model: spitcake structures, named for the coaxially laminated dessert.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-412436
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