Last week I attended the Geological Society of America (GSA) annual meeting and 125th anniversary which was held at the Colorado Convention Center in Denver, Colorado, USA – A multitude of scientific sessions and thousands of geoscientists! As always with large conferences, it is both fantastic and confusing to have so many interesting sessions presented almost simultaneously.
The Colorado Convention Center in Denver with its Blue Bear and the Rockies in the background (view from my hotel window at the Regency Hyatt; Photo: S. Lindström).
I participated in the session T238. New insights into Triassic-Jurassic Transition events and end-Triassic Mass Extinction (blue text are links to program and abstracts). This session was graciously hosted by Rowan C. Martindale and Morgan F. Schaller who had put together an interesting programme bringing forth some of the latest research and ideas concerning TJ-boundary research. We who participated got to hear interesting talks on the carbon cycle, specifically on Late Triassic pCO2 variations by Morgan Schaller et al. and on Late Triassic ocean stability and orbital control by Sylvain Richoz et al. The pedogenic carbonate results of Schaller et al.’s research suggest a long-time (30-million-years) fall in the atmospheric CO2-content from the Carnian to the late Rhaetian prior to the eruption of the Central Atlantic Magmatic Province (CAMP). Richoz et al., on the otherhand, demonstrate a relatively stable marine C-isotope curve from the Norian to the Rhaetian, displaying only a gentle decrease, i.e. possibly an on-going input of light carbon to the atmosphere (increased CO2) during the Late Triassic prior to CAMP eruption.
Regarding the plant record, Wolfram Kürschner presented some new data indicating environmental mutagenesis in Late Triassic conifers in more equatorial areas, where a sudden size increase in Classopollis pollen may be due to whole genome doubling (polyploidy) as a consequence of environmental stress. Karen Bacon talked about the fact that many present-day plants get thicker leaves when subjected to increased levels of CO2, and especially if exposed to low O2 at the same time, and put this in relation to findings in the plant records across the TJ-boundary in East Greenland. In one of the solicited talks, Jennifer McElwain presented an extensive review of her and her co-workers palaeobotanical research on the TJ-boundary of East Greenland over the last 25 years. The impact of her research did however, receive some criticism from the next solicited speaker Spencer Lucas who meant that not only is there no palaeobotanical evidence for a global or even regional mass extinction at the end of the Triassic, but not for the terrestrial terapods either! But then Lucas did not seem to acknowledge the palynological support for a floral mass extinction. His critique does emphasize that there is a need of more thorough palaeobotanical work across the TJ-boundary from other parts of the world.
Lucas also presented major criticism on the impact of the cyclostratigraphic scheme for the Newark Basin, which he said had caused “a decade-long miscorrelation” with other TJ-boundary succession. This led to a slightly heated discussion between Lucas and the next speaker, Paul Olsen, one of the researchers behind the Newark Basin cyclostratigraphy. In his talk, Paul Olsen discussed the impact a volcanic winter due to SO2-degassing from the CAMP would have on terrestrial vertebrates.
After a short break it was finally my turn. My talk, entitled “Supraregional seismites in Triassic – Jurassic boundary strata“, presented widespread evidence of episodic seismic activity in NW Europe during the end-Triassic mass extinction interval. My co-authors and I have found evidence of at least four separate seismic events in the form of soft-sediment deformations within TJ-boundary successions from Sweden, Denmark and Germany, and the implications of these on the CAMP and the end-Triassic mass extinction where discussed during the talk, which was going as scheduled when it was interrupted by a ca 5 minute long false fire alarm. Eventually I could continue and finish my talk but unfortunately with no time for questions.
One of the most interesting talks was that on the Cotham Marble where Yadira Ibarra et al. showed that the calcified microbial mats, containing prasinophycean algal cysts (Tasmanites) and a sparse shelly fauna, must have formed in a calcium carbonate supersaturated environment. The Cotham Marble is synchronous to the so called initial C-isotope excursion. Kathleen Rittersbuch et al. presented new data on earliest Jurassic siliceous sponge dominance based on fieldwork in the Peruvian Andes. Correlations with siliceous sponge records in Nevada, the Austrian Alps and Morocco indicate that this was a globally relevant phenomena.
Aviv Bachan and Jonathan Payne presented modeling of hypothesized carbon cycle perturbation scenarios for the TJ-boundary, focusing on the large positive C-isotope excursion (CIE) following the sharp negative CIE. They found that the modelled scenario most similar to the recorded C-isotope record is that with temporary increase in pCO2 coincident with the volatile release, as well as a temporary decrease in carbonate saturation, indicating that the release of volatiles during the emplacement of the Central Atlantic Magmatic Province could have been the driver of the environmental perturbation.
The final talk of the session was that of Bas van de Schootbrugge et al. who presented our palynological reworking data that indicate increased weathering and erosion, i.e. mass-wasting, synchronous to the terrestrial deforestation during the end-Triassic mass extinction. The massive reworking registered in both Germany, Denmark and Sweden, emphasizes the severity of the environmental impact on the land environment, and it seems likely that increased input of sediment, soil and organic matter to the ocean must have played a part in the extinction scenario.
We celebrated the end of an interesting the session by having lunch at the Rock-Bottom Restaurant in downtown Denver. Good food and great company! :-)