Microbial Mats in a Lower Triassic Siliciclastic Playa Environment (Middle Buntsandstein, North Sea)
Published:January 01, 2012
Achim Wehrmann, Gisela Gerdes, Richard Höfling, 2012. "Microbial Mats in a Lower Triassic Siliciclastic Playa Environment (Middle Buntsandstein, North Sea)", Microbial Mats in Siliciclastic Depositional Systems Through Time, Nora Noffke, Henry Chafetz
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The Lower Triassic siliciclastic sequence of the Germanic Basin is predominantly composed of terrestrial sediments deposited under semiarid to arid climatic conditions. In the Lower Buntsandstein unit, (non-?) marine stromatolites and oolites occur in the central part of the basin. Here we first describe the formation of microbial mats in the Middle Buntsandstein unit (Helgoland Island, southern North Sea) in a playa paleoenvironment. Microbial mats are intercalated in a depositional sequence of reddish silt- to fine-grained sandstones. Internal sedimentary fabric is dominated by even laminites, desiccation cracks, dewatering structures, internal brecciation, mm size graded layers, and small-scale oscillation ripples. Additionally, some distinct sandstone beds point towards eolian sedimentation.
Units of variable thickness (mm to several cm) contain signatures of microbial mats, e.g., internal fine lamination. Several laminae show a wavy– crinkly character well known of modern biolaminites. Various laminae indicate internal spongy fenestrate fabrics comparable to fabrics produced by modern mats dominated by photoautotroph microbes. Elongated bulges related to polygons, and domical build-ups are microbial mat structures typical for sabkha or playa settings. In addition, heterogeneously shaped fragments showing fine laminations can be interpreted as chips released from the mats. In distinct layers, also ooids and other coated grains occur.
Prolific microbial mats are known from a variety of ancient and modern sabkha and playa environments. In such settings, a wealth of sedimentary structures develops from growth response of mat-forming microbes to environmental disturbances.
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Microbial Mats in Siliciclastic Depositional Systems Through Time
The research field on microbial mats in siliciclastic environmental settings has greatly developed since its establishment by studies of pioneering scientists such as Gisela Gerdes, Wolfgang Krumbein, Jürgen Scheiber, David Bottjer and others. This SEPM Special Publication is the result of the SEPM Research Conference on Sandy Microbial Mats (modern and ancient), which was held in May 21-23, 2010 at Dinosaur Ridge, Denver, Colorado, USA. This volume presents peer reviewed individual case studies on microbial mats and on sedimentary structures (often called “microbially induced sedimentary structures-MISS”) that occur in modern and ancient marine and terrestrial environments. The conference brought together sedimentologists, microbiologists, and paleontologists from 30 countries and all five continents.