NORSTRAT - Environmental changes during the Norian (216-203 Ma) biotic crises: a palynological and organic geochemical approach

How does the environment changes around us? Present-day human activity causes major environmental stress for plant and animal life. There is reason to worry about the earth's diversity of species in the foreseeable future. Therefore, understanding of processes and patterns of past biotic crises is no longer just an academic question. There is growing scientific consensus that we have recently entered a period of man induced mass extinction, resulting in a loss of 50% of the global biodiversity within the next 100 years. Such high rates of diversity lost has happened only five times since complex life arose. The fossil record provides a vital deep-time perspective on factors affecting extinction, survival and recovery. In NORSTRAT research project we are studying palaeobiological and geochemical information from the sedimentary record to reconstruct past environmental changes between 230 and 200 million years ago, with focus on the Carnian crisis (Carnian Pluvial Event). Our detailed study of the Carnian crisis in the high latitudes (Svalbard) and the mid latitudes (Austria) revealed marked changes in the vegetation patterns. The semi-arid region became considerable wetter which had a major impact on the terrestrial and marine ecosystems. Plant groups that were characteristic for the vegetation in a warm-temperate / wet climate could expand from the North into the semi-arid climate belt in the South. These climate changes are likely related to a period of major volcanic activity such as Wrangellia oceanic volcanic province. The results obtained so far in this project have been published in a PhD thesis by S.J. Mueller and a series of publications in international journals. The postdoc sub-project by C.S. Miller has focused on organic geochemical proxies for perturbations in the global Carbon cycle associated with the Carnian Pluvial event. She has analyzed sedimentary successions (outcrop and core) in Devon (United Kingdom) for bulk Carbon isotopes and biomarker based C-isotopes (see special report for details). Also, she tested the sedimentary succession for Milankovitch cycles. It was possible to establish a astrochronological calibrated C isotope record. Our results show that the Carnian crisis is not only characterized by one, but by multiple (at least 4) maj

Cataclysmic impacts of celestial bolides or the internal (volcanism, continental break-up) and external (atmospheric acidification, ozone breakdown) dynamics of the Earth likely play an important role in times of major environmental upheaval and biotic cr ises. The resulting environmental stress initiates inhibition of photosynthesis and a decline in primary production, which in turn is believed to lead to widespread and collateral extinction of species. The Late Triassic biotic crisis provides an eminent case history of global turnover in the biosphere that is still not understood. A fundamental controversy exists about the nature of this mass extinction: a) whether the biotic turnover represents a singular event or a series of multiple ecological avalan ches and b) was the cause a celestial bolide impact or massive volcanism. Rather than focusing on the end Triassic mass extinction (~ 200 Ma) alone, we concentrate here on those events during the Norian (~ 216-203 Ma). The proposed research program aims at a better understanding of the timing and the causal connections between events in the terrestrial and marine realm through the integration of biological records inferred from pollen and spore analysis as well as environmental proxies based on organic g eochemistry into a concise stratigraphic framework. This project makes part of an interdisciplinary research program (funded by the International Continental Drilling Program and US National Science Foundation) with international participation (e.g. Colum bia University, Rutgers University, Berkeley Geochronology Center, Nanjing Institute of Geology & Paleontology). The aim of this interdisciplinary scientific joint venture is to solve the long-standing controversies regarding the Triassic mass extinctions , and to predict the fate of life in the future.