Abstract

New results of U–Th–Pb isotopic dating of detrital zircon grains from the sandstones of the Upper Tauric Formation of the Crimean Mountains, belonging to the Lower Jurassic part of the Tauric Group, are presented. Comparison of the obtained age sets of detrital zircon grains with similar data for the clastic rocks of both lower and higher stratigraphic levels of the Cimmerides of the Crimean Mountains shows a significant difference between them. This reflects radical changes in the sources of sediment supply for the studied strata, which took place at the Triassic–Jurassic boundary and at the beginning of the Middle Jurassic. During the Late Triassic–Jurassic time, the sedimentary basins of the Crimean Mountains were formed directly on the southern (in present-day coordinates) continental margin of the East European segment of Eurasia. During the Late Triassic, the vast Scythian–Tauric megabasin was located here. Mostly shallow-water sediments accumulated in its northern part, in the Scythian sedimentary basin, and flysch deposition took place in its southern part, in the Tauric deep-water sedimentary basin. The clastic components of the flysch are dominated by the products of destruction of the crystalline basement complexes of the Sarmatian segment of the East European craton (EEC), the equivalents of the crystalline complexes exposed at present within the Ukrainian Shield and the Voronezh crystalline massif. The clastic material was supplied to the Tauric basin in transit via the Scythian basin. At the Late Triassic and Early Jurassic boundary, detrital material from the EEC ceased flowing into the Tauric sedimentary basin. But detrital material, the primary sources of which were the crystalline complexes of Gondwana and the peri-oceanic complexes of the Rheic and Paleo-Tethys oceans, started to flow into it. This means that the paleogeographic situation on the southern margin of the East European segment of Eurasia changed dramatically during the Early Jurassic. The Scythian–Tauric megabasin as it existed during the Late Triassic disappeared. The Dobrogea–Crimea Uplift emerged in its northern part (Scythian sedimentary basin). However, no significant changes in the depositional environment took place in its southern part (Tauric sedimentary basin). Deep-water flysch accumulation continued there during the Early Jurassic. This inherited sedimentary basin is hereinafter referred to as Late Tauric to emphasize the difference of its sedimentary fill from the fill of the Tauric basin. At the boundary of the Early and Middle Jurassic or at the very beginning of the Middle Jurassic, sediment accumulation ceased in the Late Tauric sedimentary basin, and the Upper Triassic and Lower Jurassic strata, successively accumulated in the Tauric and Late Tauric basins, underwent deformations. Later, the system of subbasins of the Crimean Mountains formed on the basement composed of these deformed complexes during the Middle and Late Jurassic. The clastic material that accumulated in the system of subbasins of the Crimean Mountains during the Middle and Late Jurassic was mostly of local (regional) origin, but a new source of detrital material, which supplied Permian–Triassic detrital zircon grains to these subbasins, appeared in addition.

中文翻译：

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基于碎屑锆石颗粒 U-Th-Pb 同位素测年结果的克里米亚山脉 Cimmerides 上三叠统—下侏罗统复理石和中—上侏罗统粗碎屑层序的物源

摘要

介绍了属于 Tauric 群下侏罗统的克里米亚山脉上 Tauric 组砂岩中碎屑锆石颗粒的 U-Th-Pb 同位素测年新结果。将获得的碎屑锆石颗粒年龄组与克里米亚山脉 Cimmerides 较低和较高地层水平的碎屑岩的相似数据进行比较，表明它们之间存在显着差异。这反映了所研究地层的沉积物供应来源发生了根本性变化，这发生在三叠纪-侏罗纪边界和中侏罗世初期。在晚三叠世-侏罗纪时期，克里米亚山脉的沉积盆地直接形成在欧亚大陆东欧段的南部（以现在的坐标）大陆边缘。在三叠纪晚期，广阔的斯基泰-金牛座巨型盆地位于这里。浅水沉积物主要堆积在其北部，即斯基泰沉积盆地中，而复理石沉积物则发生在其南部，即金牛座深水沉积盆地中。复理石的碎屑成分主要是破坏东欧克拉通萨尔马提亚段（EEC）结晶基底复合体的产物，即目前暴露在乌克兰地盾和沃罗涅日结晶地块内的结晶复合体的等效物。碎屑物质通过斯基泰盆地输送到金牛盆地。在晚三叠世和早侏罗世边界，来自 EEC 的碎屑物质停止流入 Tauric 沉积盆地。但碎屑，其主要来源是冈瓦纳的结晶复合体以及莱克海和古特提斯洋的近洋复合体，开始流入其中。这意味着早侏罗世欧亚大陆东欧段南缘的古地理形势发生了巨大变化。在三叠纪晚期存在的斯基泰-金牛座巨型盆地消失了。Dobrogea-Crimea 隆起出现在其北部（斯基泰沉积盆地）。但其南部（金牛沉积盆地）的沉积环境没有发生明显变化。早侏罗世期间，深水复理石堆积在那里继续。这个继承的沉积盆地以下简称为金牛晚期，以强调其沉积填充与金牛盆地填充的区别。在早、中侏罗世界线或中侏罗世初期，晚金牛沉积盆地沉积物停止堆积，金牛和晚金盆地先后堆积的上三叠统和下侏罗统地层发生变形. 后来，在侏罗纪中晚期，由这些变形杂岩组成的基底形成了克里米亚山脉次盆地体系。中晚侏罗世克里米亚山脉次盆地体系中堆积的碎屑物质多为局部（区域）成因，但出现了为这些次盆地提供二叠系—三叠系碎屑锆石颗粒的碎屑物质新来源。此外。晚金牛沉积盆地沉积物停止堆积，上三叠统和下侏罗统先后堆积在金牛和晚金牛盆地发生变形。后来，在侏罗纪中晚期，由这些变形杂岩组成的基底形成了克里米亚山脉次盆地体系。中晚侏罗世克里米亚山脉次盆地体系中堆积的碎屑物质多为局部（区域）成因，但出现了为这些次盆地提供二叠系—三叠系碎屑锆石颗粒的碎屑物质新来源。此外。晚金牛沉积盆地沉积物停止堆积，上三叠统和下侏罗统先后堆积在金牛和晚金牛盆地发生变形。后来，在侏罗纪中晚期，由这些变形杂岩组成的基底形成了克里米亚山脉次盆地体系。中晚侏罗世克里米亚山脉次盆地体系中堆积的碎屑物质多为局部（区域）成因，但出现了为这些次盆地提供二叠系—三叠系碎屑锆石颗粒的碎屑物质新来源。此外。克里米亚山脉次盆地系统在侏罗纪中晚期由这些变形的杂岩组成的基底上形成。中晚侏罗世克里米亚山脉次盆地体系中堆积的碎屑物质多为局部（区域）成因，但出现了为这些次盆地提供二叠系—三叠系碎屑锆石颗粒的碎屑物质新来源。此外。克里米亚山脉次盆地系统在侏罗纪中晚期由这些变形的杂岩组成的基底上形成。中晚侏罗世克里米亚山脉次盆地体系中堆积的碎屑物质多为局部（区域）成因，但出现了为这些次盆地提供二叠系—三叠系碎屑锆石颗粒的碎屑物质新来源。此外。