The cored Konrad 101 borehole (Cenomanian–Lower Coniacian, Lower Saxony): calibration of surface and subsurface log data for the lower Upper Cretaceous of northern Germany
The cored Konrad 101 borehole (Cenomanian–Lower Coniacian, Lower Saxony): calibration of surface and subsurface log data for the lower Upper Cretaceous of northern Germany
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DOI：
10.1006/cres.2001.0283
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发表时间：
2001-10
影响因子：
2.1
通讯作者：
B. Niebuhr;F. Wiese;M. Wilmsen
中科院分区：
文献类型：
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作者：
B. Niebuhr;F. Wiese;M. Wilmsen
北方德国下萨克森萨克森萨尔茨吉特地区Konrad 101井取芯和测井的上白垩统下部地层厚239 m，可划分为12个岩性单元。Cenomanian的基底是在从上Albian Flammenmergel向250 m深处的较软、绿色泥灰岩的相变处采集的。沉积作用开始于早期，但不是最早的，早Cenomanian（下Mantelliceras mantelli区），与ultimus/Aucellina海侵（减少到SP峰值0）。重要的标志层是SP峰3处的海绵层、SP峰7上方的密齿事件、SP峰9上方的相变化和充满层（SP峰10）。土仑阶的基底被推断为位于c。162.4米，在那里Mytiloides碎片变得常见，厚度为c。88米的Cenomanian阶段。早、中期土伦期的Rotplaner相（SP峰10至16底）显示出三重细分，其厚度超过了所有已知剖面。在这段时间内，下石灰岩单元（上土仑统）的特征是有滑塌和其他外来花岗岩，表明同沉积构造作用。重要的标志层是Weisse Grenzbank（SP峰13）、泥灰岩ME和M Echen（SP峰18的底部）以及凝灰岩TF和Micraster事件（SP峰22附近）。在Cremnoceramus ex gr. deformis（29.5 m;低于SP峰23）的第一次洪水中采集的Coniacian底部，位于Grau-Weisse Wechselfolge（泥灰岩为主的泥灰岩-石灰岩交替）的上部，福尔斯，厚度约为c。133米为Turonian阶段。识别出11个三级沉积层序。通过对北方德国和盎格鲁-巴黎盆地暴露的层序地层和事件地层进行比较，显示出显著的相关性，特别是在赛诺曼阶。地球物理测井数据的时间序列分析表明，在个别三级沉积层序内，在晚期海侵和高位条件下沉积稳定。对于这些间隔，米兰科维奇频带的周期性被识别，并可用于计算积累率。该案例研究允许对钻孔进行详细的地层细分，并将其整合到现有的地面数据相关框架中，因为地球物理测井的各个峰值可以参考大型动物区带、地层事件和沉积序列。因此，北方德国上白垩统下部的盆地历史及其构造-沉积发育的重建现在可以得到相当大的改善。
Abstract The lower Upper Cretaceous succession of the cored and geophysically logged Konrad 101 borehole (Salzgitter area, Lower Saxony, northern Germany) is 239 m thick and can be subdivided into 12 lithological units. The base of the Cenomanian is taken at a facies change from the Upper Albian Flammenmergel towards softer, greenish, marly claystones at a depth of 250 m. Sedimentation commenced in the early, but not earliest, Early Cenomanian (lower Mantelliceras mantelli Zone), correlating with the ultimus/Aucellina transgression (decrease to SP peak 0). Important marker beds are the Sponge Beds at SP peak 3, the Pycnodonte Event above SP peak 7, the Facies Change above SP peak 9, and the plenus Bed (SP peak 10). The base of the Turonian is inferred to lie at c . 162.4 m, where Mytiloides debris becomes common, giving a thickness of c . 88 m for the Cenomanian Stage. The Rotplaner facies of Early and Middle Turonian age (SP peaks 10 to base of 16) shows a threefold subdivision, and the thickness exceeds that of all known sections. Otherwise unknown in this interval, the Lower Limestone Unit (Upper Turonian) is characterized by slumps and other allochthonites indicating synsedimentary tectonism. Important marker beds are the Weisse Grenzbank (SP peak 13), marls M E and M Echen (base of SP peak 18), as well as tuff T F and the Micraster Event (around SP peak 22). The base of the Coniacian, taken at the first flood of Cremnoceramus ex gr. deformis (29.5 m; below SP peak 23), falls within the upper portion of the Grau-Weisse Wechselfolge (marl dominated marl-limestone alternation), and gives a thickness of c . 133 m for the Turonian Stage. Eleven third-order depositional sequences are recognized. Sequential and event stratigraphical comparison with exposures in northern Germany and the Anglo-Paris Basin shows, especially in the Cenomanian, remarkable correlation. Time-series analysis of geophysical log data indicates stable sedimentation during late transgressive and highstand conditions within individual third-order depositional sequences. For these intervals, periodic cyclicities of the Milankovitch frequency band are recognized and can be used to calculate accumulation rates. This case study permits a detailed stratigraphic subdivision of boreholes, and their integration into existing correlation frameworks of surface data as individual peaks of geophysical logs can be referred to macrofaunal zonations, stratigraphic events and sedimentary sequences. As a consequence, the reconstruction of the basin history and its tectono-sedimentary development can now be considerably improved for the lower Upper Cretaceous of northern Germany.