The „Jurassica XII“ International Conference was held in the Conference Center of Smolenice, Slovakia in April 19th to 23rd, 2016
The Jurassic Period was the time interval tantalizing early history of dinosaurs development, which began since the 195- and ended 145-millions of years ago. Public heard about it especially in popular Steven Spielberg´s films. Also collectors of fossils and those interested in prehistoric life history know about the rich treasure of Jurassic fossils of dinosaurs, as well as ammonites, belemnites, bivalves, brachiopods, corals, and many other creatures that serve to geoscientists as a basis for drawing up more specific concepts of the Mesozoic time scale, revealing the character of ancient climate, ecosystems and the development of living creatures, or changes in the surface of our planet Earth, caused by the dynamics of its interior.
Knowing the character of a unique, relatively steady Jurassic climate, we can shed light on causes of the global climate change. Rock sequences hide records of countless transformations of environmental conditions over many millions of years. Their study can be used for drawing up astronomically calibrated "Calendary"of the Earth history, in which numerous variations on the planet's surface conditions are written. Strong cyclicity observed in continuous rock sequences can be used for astronomically calibrated timescales, since the periodicity of these rhythms is consistent with orbital forcing due to long Milankovich cycles. Jurassic paleoclimatic models, quite different from successive Cretaceous ones can learn us on rules of alternation between glacial (icehouse) and warm (greenhouse) conditions on the Earth.
In recent few years, eleven international scientific conferences and congresses were devoted to the Jurassic climate and paleoceanology. Projects of the International Geoscience Correlation (IGCP) of the UNESCO devoted special attention to it. Currently active Project No. 632 focuses on interactions between climate and extinction, major events and environmental changes in the Jurassic lake and marine ecosystems. The period of time which is engaged in this project has begun with a large disaster, which has affected living world 202 million years ago, just before the Triassic - Jurassic interface. It continued by Toarcian Anoxic Event 183 million years ago, and it was terminated by Jurassic – Cretaceous transition 145 millions of years ago. Dinosaurs received the dominance among land animals, first birds appeared, first primitive mammals evolved. Supercontinent Pangea was then began to fall apart, the Earth's surface was poured twice by tremendous effusion of basaltic lavas that caused increase in the CO2 level and reduce the temperature gradients in the atmosphere and ultimately led to a massive biotic change in the living nature. The Jurassic period was limited by two periods of mass extinctions of organisms.
Many aspects related to fauna, flora, and paleobiogeographic changes of the Jurassic environment remain an enigma for us. Conditions at high latitudes are particularly mysterious, as well as the effect of zonal climatic belts in the Jurassic greenhouse world or climatic events in the meridional climatic gradient.
In recent years, Polish, Slovak and Czech experts in close cooperation organized the "Jurassica"scientific conference, which has gradually become an effective platform for the exchange of scientific informations from all fields related to geological research of the Jurassic period. Organizers Dr. Anna Feldman-Olszewska (Państwowy Instytut Geologiczny, Warsaw) and Dr. Jozef Michalik (Institute of Earth Sciences of the Slovak Academy of Sciences, Bratislava) allied the Twelfth Conference with the IGCP Project 632 workshop, headed by Professor Jingeng Sha (Chinese Academy of Sciences in Nanjing), one of the leaders of the Conference. Conference started by a fieldtrip excursion across seven Jurassic localities of the Malé Karpaty Mts. Fifty participants from 11 countries in five specialized sessions heard 22 talks followed by discussion, continuing up to the evening by the poster panels.
At the first glance, the answer on the question “when the Jurassic ceased” seems to be clear. The International Stratigraphic table says that this occurred 145 million years ago. However, detailed rules of geoscientists community associated to the UNESCO IGCP projects and the International stratigraphic Commission (ICS), requires a precise detail for every boundary of time steps, supported by paleontological, geochemical and paleomagnetic indicators, as well as a specific rock section (the Global Stratotype), which can serve as an international caliber for other areas of the world. Such details will require intensive and long-term work of a community of professionals which is hardly avoidable without complex debate and often controversy. Only seven of the eleven steps on which the Jurassic Period is divided are currently managed to substantiate such a global stratotype which may bear the name of “GSSP” (Global stratotype Section and Point).
However, the Earth's surface was at the time of the transition of Jurassic and Cretaceous periods divided into several provinces inhabited by communities of different organisms which could not interact. Although few cosmic bodies have collided with the Earth´surface which gouged out impact craters (Bering- or Mjølnir craters) and Earth's ecosystems were in crisis, significant extinctions did not occurred. It is therefore necessary to find a common tool for correlation of Jurassic-Cretaceous boundary in remote areas of the world.
Work meeting of the Berriasian subgroup of the International Commission on Stratigraphy has been led by Professor William A. Wimbledon from the University of Bristol. The first part of the workshop consisted of reports on seven of major Eurasian Jurassic-Cretaceous boundary sections. The second and final part concentrated on the essential issues of defining the boundary between the Jurassic and Cretaceous periods problem: the last will be included also in the agenda of the International Geological Congress in Cape Town (Republic of South Africa) this year. The workshop in Smolenice recommends an intensive search for identifying multi-indicators of the CM18r Magnetic Zone, which would help overcome regional differences in the biostratigraphical record. We hope that the wide coooperation which started during this Conference will further evolve to be more strenght and complex in the future.
Text: J. Michalík
Photo: E. Baraboshkin, K. Fekete, V. Šimo