EGU22-335, updated on 26 Mar 2022
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

An exceptionally record of microbial mats thriving in a volcanic caldera setting: The Ediacaran microbialites and mat-related structures of the Anti-Atlas, Morocco 

Ibtissam Chraiki1, El Hafid Bouougri1, Ernest Chi Fru2, Nezha Lazreq1, Nasrrddine Youbi1,3, Ahmed Boumehdi1,4, Jérémie Aubineau5,6, Claude Fontaine5, and Abderrazak El Albani5
Ibtissam Chraiki et al.
  • 1Faculty of Sciences-Semlalia, Cadi Ayyad University, MARRAKECH, Morocco
  • 2Centre for Geobiology and Geochemistry, College of Physical and Engineering Sciences, School of Earth and Ocean Sciences, Cardiff University, Cardiff, UK
  • 3Faculty of Geology and Geography, Tomsk State University, Tomsk, Russia.
  • 4Instituto Dom Luiz, University of Lisbon, Portugal.
  • 5UMR CNRS IC2MP 7285, University of Poitiers, Poitiers, France.
  • 6UMR CNRS GM 5243, University of Montpellier, Montpellier, France

The Anti-Atlas belt of Morocco preserves exceptional record of an Ediacaran microbial biosphere. The Amane Tazgart Formation of the Ouarzazate Group consist of an Ediacaran volcanic alkaline lake depositional system (ca. 571 Ma) were microbial buildups accreted in an extreme environment. These microbial accumulations are exceptional not only for their wide scope of extreme setting but also for their significance for understanding the early biosphere and earth habitability. A description of these buildups provides insights into their spatio-temporal distribution, in a 11 m-thick section. Specifically, the lower part consists mainly of thrombolitic limestone, usually displaying irregular to patchy mesoclots and occasionally arranged in dendritic pattern. The upper part dominated by clastic stromatolites, exhibit a variety of morphotypes ranging vertically from planar wrinkly laminated to large domes. The transitional morphotypes are made of linked and vertically oriented or inclined columns, grading upward to cone-shaped domes. The change from planar to columnar forms has been considered to indicate a shallowing trend, whereas the transition from columnar to domal morphotypes indicate a deepening trend. Spherulitic carbonate particles usually found within thrombolites, comprise radiating, wedge-shaped crystals. The analyses of spherulites-bearing samples using diluted acetic acids reveal the presence of microbial aggregates. They preserve spherical or globular shape and often irregular morphologies showing alignment along specific direction. Microfabric typical of Extra-polymeric substances (EPS) is preserved within these carbonate aggregates, suggesting their biological origin. The mineralogy of Amane Tazgart microbialites was studied using microscopical observation and XRD analyses. XRD show significant change in fabric composition from carbonate-dominated to clastic- and epicalstic-dominated microbialites, revealing the role of calcium carbonate saturation on microbialites genesis. Several features are preserved in the microbialites fabrics including micro-tufts and gas-bubbles and gas escape structure, forming evidence for mat growth and metabolic processes related to oxygenic photosynthesis and oxygen production.

How to cite: Chraiki, I., Bouougri, E. H., Chi Fru, E., Lazreq, N., Youbi, N., Boumehdi, A., Aubineau, J., Fontaine, C., and El Albani, A.: An exceptionally record of microbial mats thriving in a volcanic caldera setting: The Ediacaran microbialites and mat-related structures of the Anti-Atlas, Morocco , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-335,, 2022.