ABSTRACT

New seismic profiles located within the Bornholm Gat in the SW Baltic Sea area image Late Cretaceous-Paleogene inversion and exhumation of a previously poorly characterized narrow crustal zone in the southern end of the Sorgenfrei–Tornquist Zone (STZ), a long pre-Alpine tectonic lineament in Europe. Thrusts and pop-up structures developed along the inversion axis accompanied by subsidence troughs on its sides. Stratigraphic analysis of chalk deposits indicates that structural shortening and inversion resulted from compressional deformation. Marginal troughs formed synchronously to inversion and adjacent to the tectonically active slope, where sediment redeposition was focused. Deposition of chalk units, composed predominantly of contourites and gravity-driven sedimentation were largely controlled by inversion tectonics and influenced by intensification of bottom currents. We find that allochthonous chalk has been buried in horizontally deposited autochthonous (pelagic) chalk. An erosional unconformity represents the base of the Maastrichtian and marks the onset of along slope deposition due to a more hydrodynamic environment. The revealed asymmetric inversion across the STZ with fold tightening and superposition of NE-NW folds attest to more than one pulse during the Late Cretaceous-Cenozoic inversion. The STZ may belong to the end-member mode of intraplate foreland basins resulting from a far-field NE-SW compression transmitted from the Africa-Iberia-Europe convergence. The intraplate stress associated with the following Maastrichtian enhanced collisional coupling between the Alpine-Carpathian orogen and its foreland, which is widely recognized (e.g., the Mid-Polish Trough, the Bohemian Massif and the Central Graben), may also have had its maximum extent to the northeast in southern Sweden.

摘要

位于波罗的海西南地区 Bornholm Gat 内的新地震剖面图像晚白垩纪-古近纪反转和在 Sorgenfrei-Tornquist 带 (STZ) 南端的一个先前特征不佳的狭窄地壳带的折返和折返，这是一个长的前高山构造欧洲的血统。逆冲和弹出结构沿反转轴发育，两侧有沉降槽。白垩沉积的地层分析表明，构造缩短和倒置是压缩变形的结果。边缘槽与反转同步形成，靠近构造活动斜坡，沉积物再沉积集中。粉笔单元的沉积，主要由等高岩组成，重力驱动的沉积主要受反转构造控制，并受底流增强的影响。我们发现异地粉笔已被水平沉积的本土（远洋）粉笔掩埋。侵蚀不整合面代表了马斯特里赫特河的底部，标志着由于更加水动力环境而沿斜坡沉积的开始。所揭示的跨 STZ 的不对称反转与褶皱收紧和 NE-NW 褶皱的叠加证明了在晚白垩世-新生代反转期间不止一个脉冲。STZ可能属于由非洲-伊比利亚-欧洲辐合传递的远场NE-SW压缩产生的板内前陆盆地的端元模态。