University of Leeds 3GP Geophysics Field Trip Lake Balaton, Hungary

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1 University of Leeds 3GP Geophysics Field Trip Lake Balaton, Hungary September 1-15, 2007 geological background and logistics Staff: Greg Houseman, Graham Stuart

2 The Alpine-Carpathian-Pannonian System Elevation (m)

3 Bohemian Massif The Pannonian Basin TransDanubian Range Vienna Basin Carpathian Mts Alps Transylvanian Basin Lake Balaton Pennines (Italy) Adriatic Sea Dinaric Alps Great Hungarian Plane cover photo from: Cloetingh,S., F.Horvath, G. Bada, and A. Lankreijer Neotectonic and Surface processes: The Pannonian Basin and Alpine/Carpathian System

4 The Pannonian is an extensional Basin covered in recent sediments. In Hungary the TransDanubian Range exposes the oldest sedimentary rocks Pliocene Quaternary Late Miocene Early to mid Miocene Paleogene Paleo Mesozoic Figure from a document by Horvath, 2003

5 Post Mid-Miocene (younger than 10 Ma) sediments The Bakony Highland is part of the TransDanubian Figure from Sacchi and Horvath, 2003

6 Tertiary-Quaternary structures: shortening is indicated across the Carpathians; extension and strike-slip inside the Pannonian Figure from Wenzel et al., 2003

7 Lithospheric Thickness Map from: Atlas of the Geodynamics of the Pannonian Basin (Horvath, Bada et al.) 100 km 60 km 80 km

8 Conceptual models for the Development of the Pannonian Alpine-Carpathian system was one continuous fold belt until mid-miocene Carpathian started to move out and overthrust East European platform Crust and lithosphere were thinned, lithosphere more so. Figure from Huismans et al., 2003

9 Present day seismicity in the Pannonian. Database includes > 20,000 historical and instrumentally recorded earthquakes. Figure from Toth et al., 2003

10 Seismic tomography shows unusually slow (or hot) upper mantle beneath the Pannonian Basin, and unusually fast (or cold) material in the transition zone beneath. Major seismicity is found in a narrow cold structure beneath the eastern Carpathians (Vrancea) Figure: Wortel and Spakman (2000)

11 Sketch of the Gravitational Instability in 3D

12 Rectangular initial crustal thickness perturbation Surface topography (m) Moho topography (km) Topography of lithosphere base (km) (km above initial lithosphere base) t=11 Myr Downwelling develops faster along the long edge of the rectangular region. Figure: Gemmer and Houseman (2006)

13 CBP-HST: High-Resolution Seismic Tomography Array (April 06 July 07) CBP-RBB: Regional Broadband Array (Sept 05 Oct 07) sensors loaned by SEIS-UK, NERC Geophysical Equipment Facility

14 Ages of Volcanic Activity in the Pannonian Volcanism (calc-alkaline) started at about 20 Ma and has continued throughout. Increasing alkaline volcanism indicates a lithospheric source region for magma.

15 Theoretical stratigraphic column along north side of Lake Balaton Pannonian silts, sands and gravels unconformably overlie mid-miocene sediments, punctuated by basalts. The major unconformity between upper Triassic reef and mid-miocene sediments represents the Alpine orogeny. Paleozoic sediments are found beneath the Triassic Figure from Geological Map of Lake Balaton

16 Natural Thermal Springs in Hungary Figure from Lenkey et al., 2003

17 Possible Geophysical Targets in Balaton Region Miocene stratigraphy and structure of sediments in particular: Depth to basement unconformities, structure Normal, Thrust and Strike-slip structures are all present from the multi-phase tectonic history (extension followed by convergence) Ground water - including thermal springs

18 Measurement Techniques Seismic: Reflection / Refraction (marine and land) High Resolution Reflection Seismic Gravity Magnetics Total Field / vertical Gradient Electrical VLF (induction) Resistivity Tomography Radar Surveying Techniques, including EDM, and GPS

19 Logistical Arrangements Refer the 2007 Geophysical Field School Handbook for details regarding arrangements for: Travel Accommodation Food Work groups Reports Safety