科研之友
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摘要
We show that the structure related to formation and development of the Precambrian basement had profound influence on the Palaeozoic and Mesozoic evolution of the Danish area. We present maps of depth to the "near" top-crystalline basement reflector, thickness of the middle to lower Palaeozoic sedimentary interval, depth to Moho, and thickness of the crystalline crust based on commercial reflection seismic data complemented by wide-angle seismic and normal-incidence deep reflection seismic profiles, potential field data and borehole information. The maps show a generally strongly faulted Precambrian basement surface below several thick pre-Permian basins, most notably on the East North Sea High. In addition to the Caledonian, Variscan and younger tectonic events the sub-Permian structure of SW Scandinavia shows evidence for Ediacaran extension, which may have initiated the main structures of the Trans European Suture Zone (TESZ). Due to variations in seismic impedance contrast between the Precambrian basement and the overlying sediments, the "basement" reflection is not identified directly in large parts of the study area. Instead a pronounced seismic interface from sandstone to shale is usually imaged similar to 300 m above the crystalline basement proper. Rift sequences of inferred late Ediacaran to early Cambrian ages are interpreted in Kattegat (up to similar to 800 m thick), in the SW Baltic Sea (up to similar to 2000 m thick), as well as in the North Sea on the East North Sea High and in the Horn Graben (up to similar to 1000 m thick). We suggest that the Ringkobing-Fyn High (RFH) and its thick crust were initiated by the development of the Iapetus and Tornquist rifts during the Rodinia break-up. The entire study area, including the RFH, is more complex at basement level than at the top pre-Zechstein level. This may reflect differential subsidence and extension of the SW Baltica foreland during the Caledonian orogeny and the post Variscan extension and magmatism.
- 出版日期2012-5
