A new interpretation of the sedimentary cover in the western Siljan Ring area, central Sweden, based on seismic data
A new interpretation of the sedimentary cover in the western Siljan Ring area, central Sweden, based on seismic data
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DOI：
10.1016/j.tecto.2012.08.040
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发表时间：
2012-12-10
期刊：
影响因子：
2.9
通讯作者：
Meinhold, Guido
中科院分区：
文献类型：
--
作者：
Juhlin, Christopher;Sturkell, Erik;Meinhold, Guido
志留环碰撞构造西段古生界两条新的反射地震剖面显示出截然不同的地震特征。更偏南的约10公里长的莫拉剖面显示出一个高度扰动的结构，只观察到几公里的相对水平分层结构。然而，对资料中可与反射相关联的折射波的解释表明，志留系碎屑岩在剖面中央约有200米厚。约600米深度的微弱反射表明存在一套400米厚的奥陶系灰岩序列。该区岩心显示志留系以页岩岩性为主，奥陶系地层较薄，表明奥陶系向北快速增厚。在更北的约12公里的乌尔萨剖面上，除了最南端的几公里外，整个剖面上都可以看到来自古生代层序的清晰反射。根据对折射到达的解释，志留纪的层序似乎在这里要薄得多，在一些地方可能没有。奥陶系也被解释为该地区较薄，沿大部分剖面最大厚度约为200-300米。结晶基底内约2公里处的较深反射可能代表榴辉岩岩床。在Mora剖面上缺乏清晰的基底反射可以归因于近地表条件和采集几何形状。该地区的地震资料和最近的岩心显示，向西南方向存在一个更深的古盆地，沉积了大量的页岩，古生代层序受到严重干扰。浅层取心和地震数据将有助于为未来更深层次的钻井定位奠定基础，以研究瑞典中部的冲击过程和古生代演化。(C)2012爱思唯尔B.V.保留所有权利。
Two new reflection seismic profiles over the Paleozoic successions of the western part of the Siljan Ring impact structure show a contrasting seismic signature. The more southerly c. 10 km long Mora profile reveals a highly disturbed structure, with only a few kilometers of relatively horizontally layered structures observed. However, interpretations of refracted arrivals in the data, that can be correlated to reflections, indicate the Silurian clastic rocks to be about 200 m thick in the central part of the profile. Weak reflections from about 600 m depth suggest a 400 m thick Ordovician limestone sequence to be present. Cores from the area show a mainly shale lithology for the Silurian and only a thin sequence of Ordovician strata, suggesting a rapid thickening of the Ordovician towards the north. On the more northern c. 12 km Ursa profile clear reflections from the Paleozoic successions are seen along the entire profile, except on the southernmost few kilometers. Based on interpretations of refracted arrivals, the Silurian succession appears to be considerably thinner here, and possibly absent at some locations. The Ordovician is also interpreted to be thinner in this area, with a maximum thickness of about 200-300 m along most of the profile. A deeper reflection from about 2 km within the crystalline basement may represent a dolerite sill. The lack of clear basement reflections on the Mora profile can be attributed to near-surface conditions and the acquisition geometry. The seismic data and recent coring in the area suggest the presence of a deeper paleo-basin towards the southwest with significantly more shales being deposited and the Paleozoic successions being severely disturbed. The shallow coring and seismic data will help form the basis for locating future boreholes for deeper drilling to study impact processes and the Paleozoic evolution of central Sweden. (C) 2012 Elsevier B.V. All rights reserved.