EUROPROBE News 9
TRANS-EUROPEAN SUTURE ZONE:
Phanerozoic Accretion and the Evolution of Contrasting
Continental Lithospheres
by Tim Pharaoh (British Geol. Survey, Keyworth) and TESZ
colleagues
The
Trans-European Suture Zone (TESZ) is the most prominent geological boundary in Europe,
separating mobile Phanerozoic terranes in the south and west from the Precambrian
East-European Craton. This complex fundamental structure crosses northwest-southeast
through central Europe, from the North Sea to the Black Sea, a distance exceeding 2000 km.
It is as clearly defined in the deep lithosphere as in the upper crust, Moho depths
increasing across the TESZ from c. 30 km beneath Phanerozoic Europe to c. 45 km beneath
the craton. Relatively high heat flow characterises Palaeozoic western Europe, in marked
contrast to the thick, relatively cold, Precambrian eastern craton.
EUROPROBE
studies of the crust and upper mantle along the TESZ and its margins are allowing new
interpretations of the thermo-mechanical processes of Phanerozoic lithosphere accretion.
The TESZ is a key enigmatic element in the evolution of the Palaeozoic orogens; together
with EUROPROBE's URALIDES project, TESZ will provide new insights into pre-Mesozoic plate
tectonics and the assembly of Pangaea.
Understanding
the contrasting signatures of European deep lithosphere requires detailed analysis of the
Phanerozoic tectonic history across the TESZ and correlation of deep and shallow crustal
structures. The Palaeozoic structures are largely obscured by Mesozoic and younger strata
of the North Sea-Danish-North German-Polish Basin; a detailed analysis of this basin
complex and its partial inversion is required to unravel the enigmatic early Phanerozoic
history of this major suture zone. Reconstruction of the Palaeozoic history is also being
much assisted by analysis of the numerous deep drillholes which penetrate the pre-Permian
basement.
Highlights of EUROPROBE's multidisciplinary TESZ project
include:
Teleseismic
and regional earthquake tomography experiments defining the complex suture in the mantle
beneath the TESZ that appears to extend through the whole lithosphere into the
asthenosphere.
Determination
of variation in Moho depth and lithospheric velocity structure across this fundamental
suture zone by seismic refraction - wide angle reflection experiments.
Correlation
of deep and shallow structures of Proterozoic and Phanerozoic lithosphere by deep seismic
reflection and magnetotelluric tomography experiments.
Deciphering
the tectonothermal history of Palaeozoic terrane accretion in central Europe by
multidisciplinary analysis of drillcores and outcrops.
Integrating
the tectonothermal history of the TESZ with that of the better exposed Palaeozoic orogens
of the Appalachians, Western Europe and the Uralides to better understand the assembly of
Pangaea.
Comparison
of Permian-Mesozoic subsidence and Cenozoic inversion of sedimentary basins overlying the
contrasting lithospheres on each side of the suture.
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