University of Leeds3GP Geophysics Field Trip

Lake Balaton, HungarySeptember 1-15, 2007

geological background and logistics

Staff: Greg Houseman, Graham Stuart

The Alpine-Carpathian-Pannonian System

Elevation (m)

The Pannonian Basin

AlpsCarpathian Mts

Dinaric Alps Great Hungarian Plane

Pennines(Italy)

Adriatic Sea

ViennaBasin

Trans-DanubianRange

Lake Balaton

cover photo from: Cloetingh,S., F.Horvath, G. Bada, and A. LankreijerNeotectonic and Surface processes: The Pannonian Basin and Alpine/Carpathian System

Bohemian Massif

TransylvanianBasin

The Pannonian is an extensional Basin covered in recent sediments. In Hungary the TransDanubian

Range exposes the oldest sedimentary rocks

Pliocene­QuaternaryLate MioceneEarly to mid­MiocenePaleogenePaleo­Mesozoic

Figure from a document by Horvath, 2003

Post Mid-Miocene (younger than 10 Ma) sedimentsThe Bakony Highland is part of the TransDanubian

Figure from Sacchi and Horvath, 2003

Tertiary-Quaternary structures: shortening is indicated across the Carpathians; extension and strike-slip inside the Pannonian

Figure from Wenzel et al., 2003

Lithospheric Thickness Mapfrom: Atlas of the Geodynamics of the Pannonian Basin

http://pangea.elte.hu/index-a.html (Horvath, Bada et al.)

60 km80 km

100 km

Alpine-Carpathian system was one continuous fold belt until mid-MioceneCarpathian started to move out and overthrust East European platformCrust and lithosphere were thinned, lithosphere more so.

Conceptual models for the Development of the Pannonian

Figure from Huismans et al., 2003

Present day seismicity in the Pannonian. Database includes > 20,000 historical and instrumentally

recorded earthquakes.

Figure from Toth et al., 2003

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)

Sketch of the Gravitational Instability in 3D

Rectangular initial crustal thickness perturbation

(km above initial lithosphere base)

Surface topography (m) Moho topography (km) Topography of lithosphere base (km)

t=11 Myr

Downwelling develops faster along the long edge of the rectangular region.

Figure: Gemmer and Houseman (2006)

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

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.

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

Natural Thermal Springs in Hungary

Figure from Lenkey et al., 2003

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

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

Logistical Arrangements

Refer the 2007 Geophysical Field School Handbook for details

regarding arrangements for:

Travel

Accommodation

Food

Work groups

Reports

Safety