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Contents

Dewey, J. F.: Transtension in the Coso region of the central Basin and Range
Weber, J. C.: Neotectonics in the Trinidad and Tobago, West Indies segment of the Caribbean-South American plate boundary
Grenerczy, Gy.: Crustal motions from space geodesy: a review from EPN, CEGRN, and HGRN data
Fodor, L., Bada, G., Csillag, G, Horváth, E., Ruszkiczay-Rüdiger, Zs. and Síkhegyi, F.: New data on neotectonic structures and morphotectonics of the western and central Pannonian Basin
Pinter, N.: Applications of tectonic geomorphology for deciphering active deformation in the Pannonian Basin, Hungary
Jocha-Edelényi, E.: Karst hydrogeology of the Transdanubian Range, Hungary: Geological constrains and human impact on a unique karst reservoir
Fodor, L., Csillag, G, Németh, K., Budai, T., Cserny, T., Martin, U., Brezsnyánszky, K. and Dewey, J. F.: Tectonic development, morphotectonics and volcanism of the Transdanubian Range: a field guide

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Preface

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Hungarian scientists and the general public learnt of the workshop trough notices describing it as a discussion about recent development of space geodesy, tectonics and structural geology. The presentations clearly demonstrated that these rapidly growing fields are able to describe and synthesize a number of earth science problems, some of which have large societal impact.

The results of the workshop included the development of new and important research relationships and co-operation, and potential for a number of joint research projects, between Hungarian and U.S. geologists in the Balaton and Transdanubian Highlands as well as in more regional tectonic studies.

New ideas and results on the problems of neotectonics of the Pannonian Basin, and past plate tectonic reconstructions were discussed during the meeting and field trip. A general agreement was reached that the present-day plate motions are markedly different from older (Miocene) deformations. The discussions strengthen the earlier suggestions that the current style of neotectonic deformation may result in increased seismic risk. However the workshop pointed out that more precise data was still needed for thorough evaluation of any natural hazards related to tectonic movements. For example, the precise time of the onset of neotectonic phase has serious implications for the rate of subsequent motion, and thus on present-day hazard estimation.

The workshop demonstrated clearly that modern geodetic techniques have major impacts on neotectonic research. Ongoing Hungarian research projects clearly demonstrate 1.3 mm/year bulk shortening between the Lake Balaton and Budapest and considerable differential motions of Transdanubia with respect to other areas, like the Great Hungarian Plain. Similarly, preliminary GPS measurements on the terraces of the river Danube confirm earlier ideas of large-scale neotectonic deformation related to uplift of the Transdanubian Range.

Geology is a field-based science. The field trip demonstrated that new field observations, supplemented with modern measuring techniques are an essential part of geological research. Integrating data from geodesy, geophysics, geomorphology, volcanology, hydrology were all needed to understand the geology of the field area. This integrated method is the only way to answer some of the problems of Transdanubia, for example the age and origin of uplift, formation of enigmatic Transdanubian valley system (including the Danube gorge), origin of the morphological depression of the Lake Balaton, etc. During the field trip this integrated approach combined with different interpretations by different geologists offered some new hypothesis, such as a compressional origin of Lake Balaton depression, combined eolian-fluvial origin of valleys, that should be tested by future research. The American scientists were particularly impressed by the reconstruction of Pliocene volcanoes of the Balaton Highland. This reconstruction offers a powerful tool to estimate pre-volcanic early Pliocene and post-volcanic Quaternary denudation, related to the uplift.

All these scientific debates are related to general concepts for future research on fossil energy resources. Neotectonic deformation capable of creating large-scale traps for hydrocarbons (like in the southern part of the Pannonian Basin) but could also contribute to destruction of already existing traps and seals by means of recent deformation.

It is also clear that neotectonics exerts a first-order control on fluid flow via the past and active fault pattern of the area, and convincing evidences of this control is found in the Transdanubian Range. Associated regional uplift of Transdanubia could play major role in establishing the (hydrothermally influenced) fluid flow.

This volume contains short papers of the participants and an excursion guidebook of the field trip to the Transdanubian Range, particularly to the Balaton Highland area.

John F. Dewey in his paper outlines the general rule for transpressional and transtensional deformation, which can be used as theoretical background for studies of deformation of the Transdanubian Range during both older (Cretaceous, Miocene) and neotectonic phases.

John C. Weber describes a case study of application of the GPS technique in the actively deforming area of the Caribbeans, namely in Trinidad Island and its surroundings. They show that the major displacement zone occurs in the middle of the island and may trigger surface deformation as well. The precise GPS measurements could modify views of the neotectonic fault geometry and the earlier plate tectonic models of a broader area.

Gyula Grenerczy summaries the results of the Global Positioning System technique in Central Europe obtained through coordinated studies from 1991 onward. He clearly demonstrates that present-day velocity field of the Pannonian basin is highly variable, both in direction and in amount. The data also suggest that the driving force of neotectonic deformation is the northward movement of the Adriatic plate, which was absorbed mainly in the Dinarides and Southern Alps, but also in the Pannonian region.

The direct effect of neotectonic plate convergence was detailed in Fodor et al. paper. In addition to briefly describe neotectonic structures in western and central Pannonian basin, the authors suggest a simplified model for neotectonic structural evolution of the Pannonian area. The model involves gradual temporal propagation of inversion structures from SW to NE, from the direction of the Adriatic plate toward the basin interior. If valid, this model may change considerations about temporal evolution of active deformation and long-term seismic hazard evaluation.

Nicholas Pinter undersigns the importance of tectonic geomorphology as a sensitive and newly growing technique in searching for young Quaternary structural elements. He also presents the preliminary result obtained by this method in southwestern Hungary, in the Zala Hills. Geomorphic indices suggest active surface deformation of the area, corroborating earlier assumptions. Further application of similar studies may have importance for active deformation, seismic risk evaluation within the poorly outcropping Pannonian Basin.

The paper of Emőke Jocha-Edelényi exploits a very important applied aspect of recent and past deformation phases. The structural geological control upon the fluid flow system of the Transdanubian Range is of primary importance, because human impact modified seriously natural circumstances. The determination of vulnerability, preservation and maintenance of karst water reservoir system is only possible when taking into account combined geological, structural and hydrogeological data sources.

Finally the excursion guidebook (Fodor et al.) describes general structural, volcanological, geomorphological and stratigraphical features of some parts of the Transdanubian Range, classical research area of the Hungarian geological research. In addition to brief description of some published and stratigraphically important sites, the guidebook concentrates on the results of new field works and on new interpretations of the structure of the Transdanubian Range. New mapping in the Vértes Hills clearly underlies the role of late Miocene faulting, which lasted in the early Pliocene as well. The resulted fault pattern might have guided inversional neotectonic structures, as revealed by inverted normal faults of the area. The determination of precise geometry of the Cretaceous imbricate structure of the Balaton Highland may also have neotectonic importance. Gently dipping thrust planes could be reactivated during Miocene transpression, and, as a newly formulated idea, can play role in neotectonic folding as well.

Neotectonic deformation played considerable, although not exclusive role in Pliocene-Quaternary landscape evolution of the Transdanubian Range. Understanding of this tectonic control and separation from the role of exogenic forces, like wind and rivers are important for societal application of structural geological results. Volcanological research can contribute considerably in solving of these neotectonic and geomorphic questions. Precise reconstruction of volcanic landforms may help to understand landscape evolution as well as the timing and amount of post-volcanic erosion.

Dr. Károly Brezsnyánszky
Director of MÁFI
Hungarian Project Leader

Dr. László Fodor
Editor

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