Substantial vegetation response to Early Jurassic global warming with impacts on oceanic anoxia

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Rapid global warming and oceanic oxygen deficiency during the Early Jurassic Toarcian Oceanic Anoxic Event at around 183 Ma is associated with a major turnover of marine biota linked to volcanic activity. The impact of the event on land-based ecosystems and the processes that led to oceanic anoxia remain poorly understood. Here we present analyses of spore–pollen assemblages from Pliensbachian–Toarcian rock samples that record marked changes on land during the Toarcian Oceanic Anoxic Event. Vegetation shifted from a high-diversity mixture of conifers, seed ferns, wet-adapted ferns and lycophytes to a low-diversity assemblage dominated by cheirolepid conifers, cycads and Cerebropollenites-producers, which were able to survive in warm, drought-like conditions. Despite the rapid recovery of floras after Toarcian global warming, the overall community composition remained notably different after the event. In shelf seas, eutrophication continued throughout the Toarcian event. This is reflected in the overwhelming dominance of algae, which contributed to reduced oxygen conditions and to a marked decline in dinoflagellates. The substantial initial vegetation response across the Pliensbachian/Toarcian boundary compared with the relatively minor marine response highlights that the impacts of the early stages of volcanogenic global warming were more severe for continental ecosystems than marine ecosystems.

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Fig. 1: Location of the study area and palaeogeographic maps of the early Toarcian.
Fig. 2: Palynological and palynofacies data through the T-OAE of Yorkshire, UK.
Fig. 3: nMDS plot of spore–pollen data.
Fig. 4: Schematic reconstruction of the major changes to continental and marine environments through the T-OAE.

Data availability

The authors declare that the data supporting the findings of this study are available within the article and Supplementary Information. All materials (rock samples and slides) are housed in the collections of the Natural History Museum, London.


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We are grateful to W. Foster, D. Murphy and M.-E. Clemence for their help with fieldwork. We thank P. von Knorring for artwork in Fig. 4. This research was funded by the Wenner-Gren Foundation (grant no. UPD2017-0155), the Swedish Research Council (grant no. VR 2015-04264), Lund University Carbon Cycle Centre and a Natural Environment Research Council (NERC) grant to R.J.T. (grant no. NE/I005641/1).

Author information

S.M.S., R.J.T. and V.V. conceived the project. S.D. and R.J.T. conducted the fieldwork and S.M.S. performed the data collection. All authors discussed and analysed the data and wrote the manuscript.

Correspondence to Sam M. Slater.

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Supplementary Information

Supplementary Information

Supplementary figures, tables and references

Supplementary Data 1

Raw palynological counts. ‘p’ refers to taxa that are present in slides but not in counts

Supplementary Data 2

Raw palynofacies counts

Supplementary Data 3

nMDS axis scores of samples for Fig. 3 and Supplementary Fig. 3.

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Slater, S.M., Twitchett, R.J., Danise, S. et al. Substantial vegetation response to Early Jurassic global warming with impacts on oceanic anoxia. Nat. Geosci. 12, 462–467 (2019) doi:10.1038/s41561-019-0349-z

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