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Proliferation of MISS-related microbial mats following the end-Permian mass extinction in the northern Paleo-Tethys: evidence from southern Qilianshan region, western China
journal contribution
posted on 2017-05-15, 00:00 authored by Y Xu, Z-Q Chen, X Feng, S Wu, Guang ShiGuang Shi, C TuAs a consequence of the end-Permian mass extinction, microbes proliferated in the post-extinction shallow marine ecosystems, in which they grew as various microbially induced sedimentary structures (MISSs) in siliciclastic settings. This paper reports, for the first time, the discovery of abundant MISSs from the lowest Triassic sandstones of shallow-water margin origin in the Zhihema sections of the southern Qilianshan region, West China. The sandstones are characterized by well-developed cross-beddings and ripple marks, and a Claraia-dominated bivalve assemblage of middle-late Griesbachian age. These sedimentary structures, together with the bivalves, suggest a high-energy peritidal zone of a shoreface setting in a clastic shallow sea environment. Seven types of MISSs are recognized and described here: pictograph-like sand cracks/crack-fills, polygonal sand crack-fills, erosional remnants, multidirectional linear grooves, sinuous crack-fills, fusiform sand cracks/crack-fills, and leveled ripple marks. Most of the newly found MISSs are morphologically comparable with their ancient and modern counterparts. Detailed optical microscope and scanning electron microscope (SEM) analyses reveal that thin clayey laminae and filamentous mica grains are aligned parallel to bedding plane, and that the matrix-supported quartz grains, overall, are oriented; both of which are interpreted to indicate biogenic origin. The biogenic origin of these MISSs is reinforced by the presence of copious putative nanoglobules and filamentous biofilm-like organic objects in the interspaces of clay minerals in laminated layers. These nanometer-scale objects are interpreted as bacterial bodies or remains that have been replaced with inorganic minerals upon fossilization. The presence of MISSs on the northern margins of Paleo-Tethys indicates that the post-extinction microbial mats had expanded their distributions from low-latitude to moderate-high latitude regions. Moreover, unlike some previously reported microbial mats that contain very rare body and trace fossils, the southern Qilianshan MISSs were found in association with abundant vertical burrows and bivalves, suggesting that the MISS-forming microbial mats may have served as oases for trace-making organisms and opportunistic bivalves to flourish in shallow-marine habitats immediately after the end-Permian mass extinction.
History
Journal
Palaeogeography, palaeoclimatology, palaeoecologyVolume
474Pagination
198 - 213Publisher
ElsevierLocation
Amsterdam, The NetherlandsPublisher DOI
ISSN
0031-0182eISSN
1872-616XLanguage
engPublication classification
C Journal article; C1 Refereed article in a scholarly journalCopyright notice
2016, ElsevierUsage metrics
Categories
Keywords
sand crackearliest Triassicshoreface environmentnorthern Paleo-Tethys Oceansouthern Qilianshanwestern ChinaScience & TechnologyPhysical SciencesLife Sciences & BiomedicineGeography, PhysicalGeosciences, MultidisciplinaryPaleontologyPhysical GeographyGeologyINDUCED SEDIMENTARY STRUCTURESEARLIEST TRIASSIC MICROBIALITESROLL-UP STRUCTURESWRINKLE STRUCTURESGEOBIOLOGIC FEATURESKIMBERLEY REGIONVINDHYAN BASINTRACE FOSSILSLUOPING AREASTROMATOLITESEvolutionary BiologyGeologyEcology
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