解决华力斯坎基底露头的中、新生代古地理地貌发育是了解中欧地球动力学的前提。在我们的研究中,我们将磷灰石裂变径迹 (AFT) 和磷灰石 (U-Th)/He (AHe) 热年代学应用于东南波希米亚地块的地表岩石。通过 AFT 方法检查了 46 个样品。额外的 AHe 测年应用于其中的 8 个。AFT 年龄范围从 251 ± 46 到 60.2 ± 4.8 Ma。AHe 年龄范围从 25 到 525 Ma,样本内分散度相当高。在区域尺度上,AFT 年龄普遍从东北部的晚瓦力西期到西南部的晚白垩世和古新世逐渐减少。这种相对于 Weinsberg 森林的 NW-SE 趋势分水岭的区域年龄不对称既不符合单个地块的区域抬升,也不符合大规模的岩石圈隆起。沿晚期瓦力斯坎断层缺乏年龄断裂表明在白垩纪和新生代不可能发生强烈的垂直偏移。热年代学数据的逆向建模表明区域早白垩世冷却和随后的晚白垩世再加热。现代地表的岩石被加热到大约 100 摄氏度的温度。80 °C 未完全重置 AFT 系统。这一热历史与白垩纪早期大大陆的存在以及随后的沉积再掩埋相吻合,直到坎帕阶达到 1 公里的覆盖层。Weinsberg 森林北部和东北部挖掘出的部分风化基底地貌作为“密封地貌”从中白垩世时期继承而来。观察到的 AFT 数据区域不对称性最好的解释是晚白垩纪到古近纪期间北宾宁洋附近大陆断崖的发展。ca 后加速冷却的最后一集。20 Ma,如热年代学模型所示,暂时归因于阿尔卑斯山-喀尔巴阡山脉推覆岩桩与其北部前陆的碰撞耦合或东阿尔卑斯山板块分离。观察到的 AFT 数据区域不对称性最好的解释是晚白垩纪到古近纪期间北宾宁洋附近大陆断崖的发展。ca 后加速冷却的最后一集。20 Ma,如热年代学模型所示,暂时归因于阿尔卑斯山-喀尔巴阡山脉推覆岩桩与其北部前陆的碰撞耦合或东阿尔卑斯山板块分离。观察到的 AFT 数据区域不对称性最好的解释是晚白垩纪到古近纪期间北宾宁洋附近大陆断崖的发展。ca 后加速冷却的最后一集。20 Ma,如热年代学模型所示,暂时归因于阿尔卑斯山-喀尔巴阡山脉推覆岩桩与其北部前陆的碰撞耦合或东阿尔卑斯山板块分离。
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Thermochronological constraints on the post-Variscan exhumation history of the southeastern Bohemian Massif (Waldviertel and Weinsberg Forest, Austria): palaeogeographic and geomorphologic implications
Resolving the Mesozoic and Cenozoic palaeogeography and geomorphologic development of outcropping Variscan basement is a pre-condition for the understanding of central European geodynamics. For our study, we have applied apatite fission-track (AFT) and apatite (U–Th)/He (AHe) thermochronology to surface rocks of the southeastern Bohemian Massif. 46 samples were examined by the AFT method. Additional AHe dating was applied to 8 of them. The AFT ages range from 251 ± 46 to 60.2 ± 4.8 Ma. AHe ages range from 25 to 525 Ma with rather high intra-sample scatter. On a regional scale, the AFT ages generally decrease from mainly late Variscan in the NE to Late Cretaceous and Paleocene in the SW. This regional age asymmetry relative to the NW–SE trending watershed of the Weinsberg Forest is neither compatible with regional uplift of a single block nor with large-scale lithospheric updoming. The lack of age breaks along late Variscan faults demonstrates that strong vertical offset cannot have occurred in Cretaceous and Cenozoic times. Inverse modeling of thermochronological data indicates regional Early Cretaceous cooling and subsequent reheating during the Late Cretaceous. Rocks of the present-day surface were heated up to a temperature of ca. 80 °C without full reset of the AFT system. This thermal history is compatible with the existence of a large mainland in Early Cretaceous times and a subsequent sedimentary reburial until the Campanian on the order of up to 1 km overburden. Parts of the exhumed weathering basal relief to the N and NE of the Weinsberg Forest are inherited as ‘sealed relief’ from Middle Cretaceous time. The observed regional asymmetry of AFT data is best explained by the development of a continental escarpment adjacent to the North Penninic Ocean in latest Cretaceous to Paleogene times. A final episode of accelerated cooling after ca. 20 Ma, as indicated by thermochronological modeling, is tentatively ascribed to either collisional coupling of the Alpine-Carpathian nappe pile with its northern foreland or to East-Alpine slab detachment.