Crustal structure along the EGT profile across the Tornquist Fan interpreted from seismic, gravity and magnetic data

被引:87
作者
Thybo, H [1 ]
机构
[1] Univ Copenhagen, Inst Geol, DK-1350 Copenhagen K, Denmark
关键词
Tornquist Fan; crustal structure; Caledonian orogeny; basin formation; magmatic intrusions; inversion tectonics;
D O I
10.1016/S0040-1951(01)00055-5
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The Tornquist Fan is a northwestward widening splay of late Carboniferous to early Permian fault tunes in the Danish area which emanates from the Teisseyre-Tornquist Zone in the Baltic Sea. It is located over an area of deep sedimentary basins around Denmark in the southwestern corner of the former Baltica plate. This paper presents an integrated model of seismic velocity, density, and magnetic properties along the EGT profile across the Tornquist Fan between southern Sweden and northern Germany. The model shows distinct features that may be related to the main tectonic events in the area. The Caledonian crustal suture between Baltica and Eastern Avalonia is interpreted from changes in physical parameters at all crustal levels; most noticeable as an abrupt, lateral change in seismic velocity in the lowest crust at Moho level from 6.9 km/s in Baltica to only 6.4 km/s in Eastern Avalonia. Thick sedimentary successions beneath the Mesozoic sequence are interpreted as Palaeozoic sedimentary rocks, which may have been deposited on the southern margin of the Baltica plate, in a deep Caledonian foreland basin, and in late Carboniferous-early Permian rifts and extensional basins. Rift related magmatism is indicated by the presence of zones of high velocity, density and magnetic susceptibility as well as strong remanent magnetization. Thermal subsidence following the emplacement of these bodies may be the origin of regional subsidence of the Danish and North German basins of late Paleozoic and Mesozoic age. Late Cretaceous to early Cenozoic inversion of basin structures is detected at the Sorgenfrrei-Tornquist Zone (STZ) in the transition between shield and basin areas. The STZ coincides with a pronounced change in crustal thickness and the southwestern edge of a major magmatic intra-crustal body. Significant, abrupt changes in Moho depth exist along the profile: 26-30 km beneath the deep basins, ca. 35 km beneath the Ringkobing-Fyn basement High, and its km beneath the Baltic Shield around the Sorgenfrei-Tomquist inversion Zone. The basement in the Tornquist Fan area is of Proterozoic age. The Moho topography indicates strong thinning of the crust during its Phanerozoic evolution. The model supports the hypothesis that existing tectonic structures and weakness zones are continuously being reactivated during subsequent tectonic activity. (C) 2001 Elsevier Science B.V. All rights reserved.
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页码:155 / 190
页数:36
相关论文
共 68 条
[1]   Seismic structure across the Caledonian Deformation Front along MONA LISA profile 1 in the southeastern North Sea [J].
Abramovitz, T ;
Thybo, H .
TECTONOPHYSICS, 1998, 288 (1-4) :153-176
[2]  
Abramovitz T, 1997, TECTONOPHYSICS, V269, P1
[3]   Seismic images of Caledonian, lithosphere-scale collision structures in the southeastern North Sea along Mona Lisa Profile 2 [J].
Abramovitz, T ;
Thybo, H .
TECTONOPHYSICS, 2000, 317 (1-2) :27-54
[4]   CRUSTAL STRUCTURE ALONG THE CENTRAL SEGMENT OF THE EGT FROM SEISMIC-REFRACTION STUDIES [J].
AICHROTH, B ;
PRODEHL, C ;
THYBO, H .
TECTONOPHYSICS, 1992, 207 (1-2) :43-64
[5]  
*BABEL WORK GROUP, 1994, GEOLOGIACHE RUNDSCHA, V83, P186
[6]  
Bachmann GH, 1999, GEOLOGY, V27, P55
[7]   THE RELATIONSHIP BETWEEN SEISMIC VELOCITY AND DENSITY IN THE CONTINENTAL-CRUST - A USEFUL CONSTRAINT [J].
BARTON, PJ .
GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1986, 87 (01) :195-208
[8]   An integrated study of the NE German Basin [J].
Bayer, U ;
Scheck, M ;
Rabbel, W ;
Krawczyk, CM ;
Götze, HJ ;
Stiller, M ;
Beilecke, T ;
Marotta, AM ;
Barrio-Alvers, L ;
Kuder, J .
TECTONOPHYSICS, 1999, 314 (1-3) :285-307
[9]  
BAYER U, IN PRESS SO MARGIN E
[10]   Permo-carboniferous magmatism of the Northeast German Basin [J].
Benek, R ;
Kramer, W ;
McCann, T ;
Scheck, M ;
Negendank, JFW ;
Korich, D ;
Huebscher, HD ;
Bayer, U .
TECTONOPHYSICS, 1996, 266 (1-4) :379-&