A terrestrial Devonian-Carboniferous boundary section in East Greenland
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ORIGINAL PAPER
A terrestrial Devonian-Carboniferous boundary section in East Greenland John E. A. Marshall 1 Received: 20 March 2020 / Revised: 15 July 2020 / Accepted: 22 July 2020 # The Author(s) 2020
Abstract Terrestrial Devonian-Carboniferous boundary sections are present in the East Greenland Devonian Basin. The boundary section on Stensiö Bjerg developed in deep, distal lake sediments with a pair of lakes representing the boundary. A diverse spore assemblage developed as the lake flooded the basin. Previously abundant spores, notably Retispora lepidophyta, Diducites spp., Rugospora radiata and all forms with bifurcate tips (Ancyrospora and Hystricosporites), then became extinct through just over a metre of section. The spore assemblage is then lost into AOM rich very high TOC% lake sediments. There is a negative δ13CTOC excursion in the Stensiö Bjerg section interpreted to represent the upper part of the positive excursion known from marine sections. The upper lake contains the simple VI spore assemblage of the earliest Carboniferous age. The correlative section on Rebild Bakker was developed in shallow proximal facies without AOM and shows that a Devonian-Carboniferous LN* to VI spore zone boundary can be picked in the lower lake based on the last occurrence of Retispora lepidophyta in an assemblage otherwise dominated by simple spores and Grandispora cornuta. Spores in this VI spore assemblage, particularly Grandispora cornuta, show sculpture malformation that is entirely characteristic of UV-B radiation damage to their DNA prior to deposition of its protective wall layer. This palynological record showing the rapid extinction of major elements within the Late Devonian microflora can be reconciled with accounts claiming there was no mass extinction of plants and spores across the boundary. The palaeobiology of the major spore groups that became extinct is reviewed. Keywords Devonian-Carboniferous boundary . Palynology . Spores . East Greenland . Extinction . UV-B
Introduction There are a series of Devonian-Carboniferous boundary sections in the East Greenland Devonian Basin (Astin et al. 2010; Marshall et al. 1999). The East Greenland Devonian Basin was located (Torsvik and Cocks 2017) within the centre of the Old Red Sandstone (ORS) Continent that was the terrestrial land mass of Euramerica and characterised by red clastic sediments. The Greenland sections were at an estimated 1000 km from the sea (Marshall et al. 2007). This remoteness means the sedimentary system within the basin was immune This article is a contribution to the special issue “Global review of the Devonian-Carboniferous Boundary” * John E. A. Marshall [email protected] 1
School of Ocean & Earth Science, University of Southampton, National Oceanography Centre, European Way, Southampton SO14 3ZH, UK
to events at the margins of the ORS Continent unless they were of sufficient magnitude to cause significant perturbations to the Earth System. These sections are probably the only known truly terrestrial sections with a recognised DevonianCa
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