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Palynostratigraphy at the Permian-Triassic boundary of the Amb section, Salt Range, Pakistan

2014; Taylor & Francis; Volume: 39; Issue: 1 Linguagem: Inglês

10.1080/01916122.2014.921648

1558-9188

Elke Schneebeli‐Hermann, Hugo Bucher,

Evolution and Paleontology Studies

AbstractPalynostratigraphy across the Permian–Triassic of the Salt Range and Surghar Range area remains poorly known because of the predominance of unsuitable facies and preservation (Nammal, Chhidru, Chitta-Landu and Narmia). Dolomite and limestone in the basal Mianwali Formation prevented the establishment of a palynostratigraphic scheme for the basal Early Triassic (Hermann et al. Citation2012). Based on the study of a new Permian–Triassic section in the Amb valley where siltstone layers are intercalated in the basal Mianwali Formation (Kathwai Member), we describe a new record of palynological assemblages from the uppermost Permian Chhidru Formation and the lowermost part of the Early Triassic Mianwali Formation. The latest Permian Chhidru 2 sporomorph association occurs in the uppermost part of the Chhidru Formation, the so-called 'white sandstone unit'. It is marked by the dominance of bisaccate pollen grains (mainly Protohaploxypinus spp.) and cavate trilete spores (mainly Kraeuselisporites spp.). Here, the previously described lowermost Triassic palynozone PTr 1 is subdivided into two subzones. PTr 1a assemblages are described from the Griesbachian Kathwai Member. They are characterized by continued high bisaccate pollen grain abundances and the presence of the lycopod genera Lundbladispora spp. and Densoisporites spp. In these assemblages, typical 'Permian taxa' and typical 'Triassic taxa' are mixed. The composition of the middle Dienerian PTr 1b assemblages corresponds to the previously described PTr 1 assemblage from Nammal and Chitta-Landu. Lundbladispora spp. and Densoisporites spp. account for ca. 80% of the total assemblage in PTr 1b. Although the Griesbachian assemblages record a decrease in diversity, the middle Dienerian assemblages represent the poorest assemblages of the studied Permian–Triassic interval. Reduviasporonites occurs only sporadically throughout the Amb succession.Keywords: PakistanPermian–Triassic boundarypalynostratigraphyextinction AcknowledgementsThis work was supported by the Swiss National Science Foundation under Grant No. PBZHP2-135955. We thank Peter A. Hochuli for discussion and constructive criticism as well as Annette E. Götz, Susanne Feist-Burkhardt and James B. Riding for their careful review and helpful comments that greatly improved the manuscript. David Ware and Nicolas Goudemand are thanked for providing biostratigraphical data (ammonoids and conodonts).Additional informationNotes on contributorsElke Schneebeli-HermannELKE SCHNEEBELI is a research associate at the University of Zurich and lecturer of Palaeobotany at University and Swiss Federal Institute of Technology, Zurich, Switzerland. Her PhD at Zurich and the following postdoc at Utrecht University included research on mainly Permian to Middle Triassic palynology and stable carbon isotopes. Elke is interested in the reconstruction of ancient terrestrial ecosystems and climate using plant fossil and geochemical data.Hugo BucherHUGO BUCHER is professor of Palaeontology at the University of Zurich and Swiss Federal Institute of Technology, Zurich, Switzerland. His research interests range from the morphogenesis of biological shapes (e.g. molluscs) to the role of mass extinctions and recoveries (e.g. the Permian Triassic crisis) in evolution and diversity of marine clades, with emphasis on biotic-abiotic interactions.