CRUSTAL-SCALE BALANCED CROSS-SECTIONS THROUGH THE VARISCAN FOLD BELT, GERMANY - THE CENTRAL EGT-SEGMENT

被引:29
作者
BEHRMANN, J
DROZDZEWSKI, G
HEINRICHS, T
HUCH, M
MEYER, W
ONCKEN, O
机构
[1] GEOL LANDESAMT NORDRHEIN WESTFALEN,W-4150 KREFELD,GERMANY
[2] UNIV GOTTINGEN,INST GEOL & DYNAM LITHOSPHARE,W-3400 GOTTINGEN,GERMANY
[3] FREE UNIV BERLIN,INST GEOPHYS WISSENSCH,W-1000 BERLIN 33,GERMANY
[4] UNIV BONN,INST GEOL,W-5300 BONN,GERMANY
[5] UNIV WURZBURG,INST GEOL,W-8700 WURZBURG,GERMANY
关键词
D O I
10.1016/0040-1951(91)90287-3
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
This paper presents crustal-scale, geometrically isostatically balanced cross sections through the Rhenohercynian and Saxothuringian zones of the Variscan fold belt of Germany. The cross sections are based on surface geological data and on results of the DEKORP deep reflection profiles. They were constructed by means of computer-assisted, iterative forward modelling. The Rhenohercynian zone, corresponding to the Externides of the Variscan belt, developed out of a some 300 km wide rifted continental margin sedimentary prism, limited to the south by the narrow Giessen oceanic basin. During Carboniferous imbrication this shelf sequence is stripped of its basement above one or more decollements and shortened by some 150 km. Closure of the Giessen ocean and emplacement of the ophiolite bearing Giessen nappe entailed a minimum additional 200 km of crustal shortening. The structure of the model correlates well with the present outcrop pattern of rock units, their metamorphic history, the seismic and magnetotelluric architecture of the crust, and its present outcrop pattern of rock units, their metamorphic history, the seismic and magnetotelluric architecture of the crust, and its present regional distribution of thickness. The deeper crust beneath the Rhenish Massif is probably devoid of extremely weak decollement horizons and pronounced rheological stratification. In the southward adjacent Saxothuringian zone, nappe development involving the stacking of crustal slices during Middle Devonian to Visean times accounts for a further 170 km of crustal shortening above an infracrustal, partly blind thrust system with flat-ramp-geometry. Total crustal shortening in the analyzed profiles is estimated to be of the order of 520 km; this figure is a conservative value. Prominent uncertainties include the unknown importance of crustal wrenching, the state of strain within thrust units, the distribution of strain within the lower crust, and major changes in thrusting directions during the course of orogenic history.
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页码:1 / 21
页数:21
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