A multistratigraphic approach to pinpoint the Permian-Triassic boundary in continental deposits: The Zechstein-Lower Buntsandstein transition in Germany
A multistratigraphic approach to pinpoint the Permian-Triassic boundary in continental deposits: The Zechstein-Lower Buntsandstein transition in Germany
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DOI：
10.1016/j.gloplacha.2017.03.004
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发表时间：
2017-05
影响因子：
3.9
通讯作者：
F. Scholze;Xu Wang;U. Kirscher;Johannes Kraft;J. Schneider;A. Götz;M. Joachimski;V. Bachtadse
中科院分区：
文献类型：
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作者：
F. Scholze;Xu Wang;U. Kirscher;Johannes Kraft;J. Schneider;A. Götz;M. Joachimski;V. Bachtadse
中欧盆地非常适合对晚二叠世至早三叠世大陆沉积物进行高分辨率多地层学研究。这里对德国中部岩石地层 Zechstein 和 Buntsandstein 群暴露良好的连续转变进行了同位素化学地层学（δ13Corg、δ13Ccarb、δ18Ocarb）、主量和微量元素地球化学、磁性地层学、孢粉学和壳甲虫生物地层学的研究。分析的材料取自跨越二叠纪-三叠纪边界的经典关键剖面（废弃的 Nelben 粘土矿坑、Caaschwitz 采石场、Thale 铁路切口、废弃的 Heinebach 粘土矿坑）和最近的钻芯剖面（Caaschwitz 6/2012）。德国中部的 Zechstein-Buntsandstein 过渡区由复杂的沉积相组成，包括萨布哈、普拉亚湖、风积和河流沉积物，主要为红色硅质碎屑和湖相鲕粒灰岩夹层。 δ13Corg 的新数据范围从 − 28.7 到 − 21.7 ‰，显示出多次偏移。最显着的负移与鲕粒岩和灰色粘土粉砂岩的夹层相关，而较高的 δ13Corg 值对应于古土壤叠印的开始。 δ13C 碳值范围为 − 9.7 至 − 1.3 ‰，Zechstein 群白云岩结核中记录到的变化最大。与跨越 Zechstein-Buntsandstein 边界的沉积相变化相反，用作风化条件代理的主要元素值（CIA、CIA*、CIA-K）表明气候稳定性。用于德国中部晚二叠世到早三叠世过渡的地球化学特征的微量元素数据表明，Zechstein-Buntsandstein 边界处的铷含量下降。从 Caaschwitz 采石场部分获得的新孢粉学数据揭示了下富尔达组中晚二叠世孢粉型的出现，而早三叠世元素记录在上富尔达组的上部。本研究证实了卡施维茨采石场上部富尔达地层中存在正常极化磁区，支持这一关键地层区间与其他地区海洋剖面已知的早三叠世基底正常磁极性的区域间相关性。基于多地层数据的综合，二叠纪-三叠纪边界被认为位于上富尔达组的下部，这在生物地层学上得到了早三叠世Euestheria gutta-Palaeolimnadiopsis vilujensisconchostracan动物群的首次出现日期的证实。从 Zechstein 群中下层的硅质碎屑矿床中报道的壳甲虫的罕见记录可能表明其具有对晚二叠世大陆沉积物进行进一步生物地层细分的潜力。
The Central European Basin is very suitable for high-resolution multistratigraphy of Late Permian to Early Triassic continental deposits. Here the well exposed continuous transition of the lithostratigraphic Zechstein and Buntsandstein Groups of Central Germany was studied for isotope-chemostratigraphy (δ13Corg, δ13Ccarb, δ18Ocarb), major and trace element geochemistry, magnetostratigraphy, palynology, and conchostracan biostratigraphy. The analysed material was obtained from both classical key sections (abandoned Nelben clay pit, Caaschwitz quarries, Thale railway cut, abandoned Heinebach clay pit) and a recent drill core section (Caaschwitz 6/2012) spanning the Permian-Triassic boundary. The Zechstein–Buntsandstein transition of Central Germany consists of a complex sedimentary facies comprising sabkha, playa lake, aeolian, and fluvial deposits of predominantly red-coloured siliciclastics and intercalations of lacustrine oolitic limestones. The new data on δ13Corgrange from − 28.7 to − 21.7 ‰ showing multiple excursions. Most prominent negative shifts correlate with intercalations of oolites and grey-coloured clayey siltstones, while higher δ13Corgvalues correspond to an onset of palaeosol overprint. The δ13Ccarbvalues range from − 9.7 to − 1.3 ‰ with largest variations recorded in dolomitic nodules from the Zechstein Group. In contrast to sedimentary facies shifts across the Zechstein-Buntsandstein boundary, major element values used as a proxy (CIA, CIA*, CIA-K) for weathering conditions indicate climatic stability. Trace element data used for a geochemical characterization of the Late Permian to Early Triassic transition in Central Germany indicate a decrease in Rb contents at the Zechstein-Buntsandstein boundary.New palynological data obtained from the Caaschwitz quarry section reveal occurrences of Late Permian palynomorphs in the Lower Fulda Formation, while Early Triassic elements were recorded in the upper part of the Upper Fulda Formation. The present study confirms an onset of a normal-polarized magnetozone in the Upper Fulda Formation of the Caaschwitz quarry section supporting an interregional correlation of this crucial stratigraphic interval with the normal magnetic polarity of the basal Early Triassic known from marine sections in other regions. Based on a synthesis of the multistratigraphic data, the Permian-Triassic boundary is proposed to be placed in the lower part of the Upper Fulda Formation, which is biostratigraphically confirmed by the first occurrence date of the Early TriassicEuestheria gutta-Palaeolimnadiopsis vilujensisconchostracan fauna. Rare records of conchostracans reported from the siliciclastic deposits of the lower to middle Zechstein Group may point to its potential for further biostratigraphic subdivision of the Late Permian continental deposits.