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Multiple climatic changes around the Permian-Triassic boundary event revealed by an expanded palynological record from mid-Norway

Peter A. Hochuli, Jorunn Os Vigran, Elke Hermann and Hugo Bucher
Multiple climatic changes around the Permian-Triassic boundary event revealed by an expanded palynological record from mid-Norway
Geological Society of America Bulletin (May 2010) 122 (5-6): 884-896

Abstract

Here, we present the palynological record from two shallow core holes (6611/09-U-01 and -02) from the Trondelag Platform offshore mid-Norway consisting of 750 m of Upper Permian and Lower Triassic sediments. The relatively homogeneous assemblages recovered from the Upper Permian deposits are dominated by gymnosperm pollen, mainly pteridosperms. At the base of the Griesbachian, numerous spore species appear in the record, leading to an increased diversity. The change at this boundary is also marked by the massive reduction of one group of pteridosperm pollen (Vittatina). Together with other typical Permian elements (e.g., Lueckisporites virkkiae), this group is rare but consistently present in the lower part of the Griesbachian, and it gradually disappears in its upper part. The distribution of other groups such as taeniate and non-taeniate bisaccate gymnosperm pollen (pteridosperms and conifers) shows no significant change across the boundary, whereas spores and other gymnosperm pollen increase in diversity and abundance. These changes coincide with the formational change between the Schuchert Dal Formation (Upper Permian) and the Wordie Creek Formation (Griesbachian) equivalents. Late Permian and Griesbachian palynomorph assemblages display different patterns. The former show a homogeneous composition of low diversity, whereas the latter reflect diverse and variably composed floras. The data suggest that the arid phase of the Late Permian was followed by a humid phase at the base of the Griesbachian. In the Griesbachian section, a succession of six distinct palynological assemblages (phase II-VII) can be inferred. Comparable changes have been described from East Greenland. The variations in the palynological record are interpreted to reflect changing ecological conditions (e.g., changing humidity). Comparable variations in the distribution of delta (super 13) C isotope values reported from various sections from Greenland and China, showing stable values during the Late Permian and highly variable values during the Griesbachian, suggest common causes for the observed fluctuations. Multiphase volcanic activity of the Siberian traps seems to be the most likely candidate to have caused the variations in the delta (super 13) C isotope as well as in the palynological record. In contrast to the common claim that marine and terrestrial biota both suffered a mass extinction related to the Permian-Triassic boundary event, the studied material from the Norwegian midlatitudinal sites shows no evidence for destruction of plant ecosystems. The presence of diverse microfloras of Griesbachian age supports the idea that the climate in this area allowed most plants to survive the Permian-Triassic boundary event.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 122
Serial Issue: 5-6
Title: Multiple climatic changes around the Permian-Triassic boundary event revealed by an expanded palynological record from mid-Norway
Affiliation: University Zuerich, Paleontological Institute and Museum, Zurich, Switzerland
Pages: 884-896
Published: 201005
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 57
Accession Number: 2010-041916
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 1 table, sketch map
N63°00'00" - N65°00'00", E10°00'00" - E13°00'00"
Secondary Affiliation: SINTEF Petroleum Research, NOR, Norway
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201023
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