Northwest Africa’s Ediacaran to early Cambrian fossil record, its oldest metazoans and age constraints for the basal Taroudant Group (Morocco)
| Autor: | Dominik Letsch, Stefano M. Bernasconi, Thomas M. Blattmann, Albrecht von Quadt, Simon J.E. Large, Wilfried Winkler, Christian Klug |
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| Přispěvatelé: | University of Zurich, Letsch, Dominik |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
010504 meteorology & atmospheric sciences
biology Fauna Geology 10125 Paleontological Institute and Museum 010502 geochemistry & geophysics biology.organism_classification 01 natural sciences Diagenesis Paleontology chemistry.chemical_compound chemistry 560 Fossils & prehistoric life Geochemistry and Petrology Namacalathus Geochronology Tubular microfossils Precambrian-Cambrian boundary Aspidella Ediacara biota Detrital zircons 1906 Geochemistry and Petrology Carbonate Radiometric dating 1907 Geology 0105 earth and related environmental sciences Zircon |
| Zdroj: | Precambrian Research, 320 |
| Popis: | The Anti-Atlas area in southern Morocco preserves one of the most complete latest Ediacaran to Cambrian shallow-marine carbonate records in the world and serves as a standard for global chemostratigraphic δ13Ccarb curves. Contrary to the excellent chemostratigraphic coverage, neither metazoan fossils (only stromatolites and calcified algae) nor radiometric age constraints were hitherto available for the basal part of this carbonate record, the Tifnout Member of the Adoudou Formation of the Taroudant Group. We report an Ediacara-type fauna from shallow-marine sandstones from the basal Tabia Member and microfossils from dolostones from both the Tabia and the Tifnout members of the Adoudou Formation. The former are discoidal fossils and share many characteristics with the form genus Aspidella and exhibit a peculiar style of preservation, pointing towards an early diagenetic two-stage (carbonate followed by silica) cementation history, leading to good preservation of these supposedly once soft-bodied organisms. The dolostone-hosted microfossils are preserved as sparite-filled molds enclosed by a thin opaque envelope. Despite their small size, they resemble late Ediacaran calcifying metazoans such as Namacalathus and tubular small shelly fossils. Together, these fossils constitute the oldest known direct evidence for presumably metazoan life from Northwest Africa. We also report new time constraints for the Adoudou Formation and fossils enclosed therein based on combined LA-ICP-MS and high-precision CA-ID-TIMS U-Pb zircon geochronology of detrital and volcanic zircons. Together with new chemostratigraphic (δ13Ccarb) and literature data, these new age constraints suggest a late Ediacaran age (time span between ca. 561 and 542 Ma) for the discoidal Ediacara-type fossils from the basal Tabia Member, and a latest Ediacaran to earliest Cambrian (time span between ca. 544 and 540 Ma) and an early Cambrian age (time span between ca. 528 and 523 Ma) for the two microfossil faunas from the Tifnout Member. |
| Databáze: | OpenAIRE |
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