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Spongy-looking microfabrics in the earliest named stromatolite represent deep burial alteration and incipient metamorphism

Neuweiler, Fritz ; Mueller, Mathias; Walter, Benjamin F. 1; Landing, Ed; Beranoaguirre, Aratz 2; Sendino, Consuelo; Amati, Lisa; Kershaw, Stephen
1 Institut für Angewandte Geowissenschaften (AGW), Karlsruher Institut für Technologie (KIT)
2 Karlsruher Institut für Technologie (KIT)

Abstract:

The earliest named stromatolite Cryptozoon Hall, 1884 (Late Cambrian, ca. 490 Ma, eastern New York State), was recently re-interpreted as an interlayered microbial mat and non-spiculate (keratosan) sponge deposit. This “classic stromatolite” is prominent in a fundamental debate concerning the significance or even existence of non-spiculate sponges in carbonate rocks from the Neoproterozoic (Tonian) onwards. Cryptozoon has three types of microbially-induced carbonate layers: clotted-pelletoidal micrite with microbial filaments, clotted-pelletoidal micrite with vesicular structure, and dense microcrystalline laminae. A fourth, stratiform to patchy fabric comprises suspect sponges. Using contextual fabric analysis, elemental mapping, cathodoluminescence, fluid inclusions, electron backscatter diffraction, U–Pb dating, and burial history, the sponge interpretation is denied. Neither a distinct sponge body outline nor a canal system is identifiable. Instead, the suspect fabric is secondary in origin, and best explained as a product of Carboniferous (Mississippian) deep burial alteration associated with basement reactivation. Key petrographic observations include heterogenous recrystallization via aggrading Ostwald ripening with interfingering reaction fronts typical for partially miscible fluids, a granoblastic calcite texture (incipient metamorphism), and subsequent hypidioblastic white mica (arguably Carboniferous/Permian, Alleghenian orogeny). ... mehr

Zugehörige Institution(en) am KIT Institut für Angewandte Geowissenschaften (AGW)
Publikationstyp Zeitschriftenaufsatz
Publikationsdatum 28.12.2024
Sprache Englisch
Identifikator ISSN: 2045-2322
KITopen-ID: 1000178494
Erschienen in Scientific Reports
Verlag Nature Research
Band 14
Heft 1
Seiten Art.-Nr.: 31537
Nachgewiesen in Scopus
Web of Science
Dimensions

Verlagsausgabe §
DOI: 10.5445/IR/1000178494
Veröffentlicht am 30.01.2025
Seitenaufrufe: 16
seit 30.01.2025
Downloads: 11
seit 31.01.2025
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