Gehouden op 19 maart 1997
De symposiumcommissie van het Geologisch College Miölnir is er wederom in geslaagd om een bijzonder interessant symposium te organiseren. Dit jaar wordt de tektoniek van Europa besproken, met een nadruk op gebieden in Oost-Europa. Uiteraard gebeurd dit niet zonder buitenlandse vertegenwoordiging.
Op deze pagina vindt U informatie over het programma en de lezingen.
Zoals ieder jaar is het symposium voor iedereen bedoelt en de toegang is gratis. Voor diegene die het symposium hebben bezocht, organiseert Miölnir tevens een borrel op Unitas S.R. om alles te laten bezinken.
De symposiumcommissie 1997:
Almar A. de Ronde Praeses
Hester E. van de Kasteele Ab-actis
Femke M. Roos Fiscus
Douwe G. van der Meer Vice Ab-actis
Bouko B.S.A. Vogelaar Assessor I
Martine G.C. Vernooy Assessor II
Program:
13:00 Opening Symposium.
13:10 Dr. Svetlana V. Bogdanova (Department of Geology, University of Lund, Sweden) :
“A new image of the old East European Craton”
13:55 Dr. Randell Stephenson (Netherlands Research School of Sedimentary Geology, Vrije Universiteit, Amsterdam):
“EUROPROBE studies of the intracratonic Pripyat-Dniepr-Donets Basin, Belarus and Ukraine”
14:40 Dr. Hanneke Paulssen (Faculty of Earth Sciences, Utrecht University):
“Structure beneath Europe from seismological research at Utrecht University”
15:25 Coffee break
15:55 Prof.dr. M.J.R Wortel (Faculty of Earth Sciences, Utrecht University):
“Arc migration, basin development and orogenic processes in the Alpine-Mediterranean region”
16:40 Prof.dr. S.A.P.L. Cloetingh (Netherlands Research School of Sedimentary Geology, Vrije Universiteit, Amsterdam):
“Tectonics and orogenic processes:towards integrated models”
17:25 End of the symposium followed by a drink at studentsociety “Symposion”,
Lucas Bolwerk 8.
For information, tel:030-2871931/6952654, fax:030-2535030, e-mail:miolnir@geof.ruu.nl
A new image of the old East European Craton
The East European Craton occupies the entire northeastern half of Europe. It is the “UR-EUROPA” of Stille (1924) and the “FENNOSARMATIA” of Bubnoff (1935). From the 19th century onwards, this craton has been a target of geological investigations. Surrounded by Phanerozoic orogenic belts of different ages, it served as a test area for many hypotheses and concepts that concerned the overall geology and tectonics of Europe. The relationships between orogeny in western Europe and the formation of synchronous sedimentary basins in the East European Craton have long been and still are a high research priority. In the East European Craton, the crystalline Precambrian crust is exposed only in the Baltic and the Ukrainian Shields, while the largest part of the territory is covered by platformal sediments. The understanding of the crustal structure of the craton developed during four major stages of research:
In the second half of the 19th and the beginning of this century, mostly petrographical research was conducted on the crystalline rocks in the shield areas. First attempts were made to assess the affinity between the crystalline rock units of the Baltic and Ukrainian Shields, and the Voronezh Massif. Some beginnings, mostly guesswise, were made in the study of the structures between the exposed shield areas.
In the thirties and the forties of our century, the first aeromagnetic surveys were carried out. These demonstrated the outlines of the magnetic anomaly patterns in the entire East European Craton, and the continuation into the platform basement of some structures known from the exposed crust of the shields. The concepts and ideas in regard to the ages and tectonic significance of the revealed magnetic anomalies were still extremely unclear and contradictory, even to the point of considering some of these structure to be Caledonian or Variscan in origin.
Between the forties and the nineties, an ever increasing number of deep drillings penetrated the basement in the interior of the East European Craton. In general, these drillings showed that the basement rock units are similar to those of the shields. Geophysically, a distinction was made between areas of isometric patterns of weak magnetic anomalies and belts of strong, aligned, linear, often positive anomalies. For a few decades, the former were ascribed to stable Archaean blocks and massives, while the latter were assumed to represent Proterozoic folded belts. As depicted in the 1981 edition of the “International Tectonic Map of Europe and Adjacent Areas” (UNESCO/IUGS), and in the paper of Khain of 1977 (cf. also Goodwin, 1991), the whole structure of the craton was at that time seen as a mosaic of numerous Archaean blocks of limited size set in an intervening matrix of Proterozoic orogenic belts.
In the beginning of the present decade, international cooperation accelerated by “Perestroyka” triggered the advancement of an essentially different model of the lithospheric structure of the European Precambrian craton. The current model is based on the applications of actualistic, plate-tectonic approaches also to the Precambrian. It implies that the East European craton, similarly to most Precambrian cratons worldwide, is an amalgamation of once autonomous large crustal segments representing fragments of late Archaean megacontinents joined along Proterozoic belts of collisional orogeny. In addition, there exist wide belts of juvenile Palaeoproterozoic crust formed along one-time interfaces between continents and oceans.
As formulated by this author (Bogdanova, 1993), the East European Craton is made up of three segments with different internal tectonic grain and independent Archaean and particularly Palaeoproterozoic histories. These three segments have been named Fennoscandia, Sarmatia and Volgo-Uralia. The segment outlines coincide closely with three MAGSAT mega-anomalies. In the later half of the Palaeoproterozoic and the earliest Mesoproterozoic, after ca. 2.0 Ga, Fennoscandia grew toward the present west by gradual accretion of new juvenile crust. This process continued until ca. 1.55 Ga and was preceded by rifting of the Archaean proto-craton in northeastern Fennoscandia and even its dispersal during the earliest Palaeoproterozoic, ca 2.5-2.0 Ga ago. The rifted Archaean domains were partly reassembled during collisional orogeny that affected NE Fennoscandia between 1.95 and 1.85 Ga. This orogeny defined the NNW to NW regional trends of crustal discontinuities and deformational zones within the Archaean crust. Fennoscandia thus comprises two distinct Palaeoproterozoic orogens, an accretional, long-lived one in the southwest and a shorter, collisional one in the northeast. Volgo-Uralia, in contrast, underwent a thorough reorganization of its Archaean crust into a system of giant late Archaean – Palaeoproterozoic dome-like structures. The Palaeoproterozoic rifting and collision sutures prominent in northeastern Fennoscandia do not appear to continue into Volgo-Uralia across the juncture zone between these two crustal segments. At least, they are not seen in the Volgo-Uralian patterns of magnetic anomalies.
Sarmatia is the oldest and most “exotic” amongst the three crustal segments. It resembles more the Precambrian of the present southern hemisphere than that of the North Atlantic cratons. Sarmatia was formed by the welding together of several Archaean terranes with ages ranging from ca. 3.7 Ga to 2.8 Ga. The aggregation of these terranes into the Sarmatian continental segment began in the late Archaean but mostly took place in the Palaeoproterozoic, between 2.3 and 2.1 Ga ago.
Palaeomagnetically, Fennoscandia and Sarmatia were separated from each other before ca. 1.85 Ga. At that date, the amalgamation of most component parts of the East European Craton into a single entity appears to have occurred.
The three crustal segments of the East European Craton are separated by the Meso- to Neoproterozoic (Riphean) transcratonic rift systems (aulacogens) which follow the Palaeoproterozoic collisional sutures. The Central-Russian rift system that continues toward the southwest into the Volhyn-Orsha depression separates Fennoscandia from the other two segments all the way from the Timan uplift in the northeast to the Trans-European-suture zone (“Tornquist zone”) in the southwest. The Pachelma rift system marks the boundary between Sarmatia and Volgo-Uralia. It passes into the Peri-Caspian depression in the southeasternmost part of the craton. The junction zones between the crustal segments represent a variety of Palaeoproterozoic collisional processes and relationships with the subsequent Riphean aulacogens. The latter much influenced the development of the platformal basins within the craton.
References:
Bogdanova, S., 1993. Segments of the East European Craton. In: D. G. Gee and M. Beckholmen (Editors), EUROPROBE in Jablonna 1991. Institute of Geophysics, Polish Academy of Sciences – European Science Foundation, Warsaw, pp. 33-38.
Goodwin, A.M., 1991. Precambrian Geology. Academic Press Limited, London, 666 pp. International Tectonic Map of Europe and Adjacent Areas, 2nd Edition. Scale 1:2 500 000. Peive, A. V.., Bogdanov, A. A. and Khain, V. E. (Editors), 1981, CGMW / UNESCO/IUGS, 20 sheets.
Khain, V. E.., 1977. The new International Tectonic Map of Europe and some problems of structure and tectonic history of the continent. In: D. V. Ager and M. Brooks (Editors), Europe from Crust to Core. John Wiley & Sons, Ltd., London, pp. 19-40.
Further reading:
Bogdanova, S.V., Pashkevich, I.K., Gorbatschev, R., Orlyuk, M.I. 1997. Riphean rifting and major Palaeoproterozoic crustal boundaries in the basement of the East European Craton: geology and geophysics. Tectonophysics, 268: 1-22
Gal, G. and Gorbatschev, R., 1987. An outline of the Precambrian evolution of the Baltic Shield. Precambrian Research, 35: 15-52.
Gorbatschev, R. and Bogdanova, S., 1993. Frontiers in the Baltic Shield. Precambrian Research, 64: 3-21.
Nikishin, A.M., Ziegler, P.A., R.A. Stephenson, Cloetingh, S.A.P.L., Furne, A.V., Fokin, P.A., Ershov, A.V., Bolotov, S.N., Korotaev, M.V., Alekseev, A.S., Gorbachev, V.I., Shipilov, E.V., Lankreijer, A., Bembinova, E.Yu., Shalimov, I.V. 1997. Late Precambrian to Triassic history of the East-European Craton: dynamics of sedimentary basin evolution. Tectonophysics, 268, 23-64
Shchipansky, A. A. and Bogdanova, S. V., 1997. The Sarmatian crustal segment: Precambrian correlation between the Voronezh Massif and the Ukrainian Shield across the Dniepr-Donets Aulacogen. Tectonophysics, 268: 109-126
Dr.Sc. Svetlana V. Bogdanova
Mineralogy and Petrology
Department of Geology
Lund University
EUROPROBE studies of the intracratonic Pripyat-Dniepr- Donets Basin, Belarus and Ukraine
This presentation draws upon a widely ranging set of multidisciplinary studies of the Pripyat-Dniepr-Donets rift system in Belarus and Ukraine carried out as part of EUROPROBE in collaboration with Earth scientists from Belarus, England, France, Netherlands, Russia, Sweden, Switzerland, and Ukraine. The highlights of a number of different techniques of studying this complex Late Palaeozoic intracratonic rift, based on deep and shallow seismic reflection studies, potential field data, cyclostratigraphy and sedimentology, geochemical analysis, and paleogeographic reconstructions, are described and it will be shown how all or some of these are utilised in several different approaches to modelling the tectonic history of the rift basin. The key issues receiving attention include the timing and volume of magmatism versus the rate and magnitude of faulting in the rift zone, the relationship of pre-existing structure and basement rheology (composition and temperature) to the locus and style of rifting, the significance of regional platform uplift and subsidence to the mechanism of rifting, and the causes and effects of structural reactivations within the rift zone. It is concluded that fundamental processes occur in the lower crust and subcrustal lithosphere during and after rifting that are not fully appreciable within a conventional sedimentary basin tectonic modelling framework.
R.A. Stephenson
(Netherlands Research School of Sedimentary Geology, Vrije
Universiteit, Amsterdam)
Structure beneath Europe from seismological research at Utrecht University
The upper mantle structure down to a depth of 660 km is one of the main research objectives of seismological research at Utrecht University. The seismology group has a strong background in the theory of wave propagation and inversion techniques, but major contributions to our image of the upper mantle structure strongly rely on the recordings of our 14 seismic stations of the Network of Autonomously Recording Seismographs (NARS).
The history of NARS now spans nearly 15 years and the stations have been deployed in different places:
along a line from South Sweden to southern Spain,
in Iberia
in the Netherlands and its immediate vicinity.
Currently stations are deployed in the former Soviet Union and in Finland. Altogether the data recorded by these stations provide a wealth of information about the upper mantle structure beneath Europe. I will show some of our research on upper mantle imaging and how this relates to the tectonics of Western and Eastern Europe. Furthermore I will show how we can determine the type of movement during an earthquake using NARS seismograms of the 1992 Roermond earthquake. It illustrates how the fault movement fits into the local tectonics of the region.
Dr. Hanneke Paulssen
Faculty of Earth Sciences
Utrecht University