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Sedimentary aspects of the onset of Middle Triassic continental rifting in the western end of Neotethys; inferences from the Silica and Torna Nappes, NE Hungary: a review
Facies ( IF 1.8 ) Pub Date : 2022-04-21 , DOI: 10.1007/s10347-022-00646-3
Kinga Hips 1
Affiliation  

The initiation of continental rifting from the latest Early Triassic was reconstructed by correlation of sedimentary formations deposited in the western end of Neotethys (in the Dinaric–Alpine oceanic branch). The shallow-marine and basinal strata of the Silica Nappes and the Bódvarákó Series from the Torna Nappe (located in the southern part of the Inner Western Carpathians) were studied and compared to sedimentary successions described from the Alps, the Carpathians and the Dinarides. The depositional zonation, developed on the shelf during the Late Permian‒Early Triassic transgression, was dissected and rearranged from the latest Early Triassic. The facies pattern and the differential sedimentary evolution of the shelf domains suggest that the accelerated subsidence began in the latest Early Triassic, and was connected to the onset of continental rifting. Three stages are reconstructed in the studied time-frame. (1) Dark grey carbonates, very poor in fossils, were deposited in restricted and hypersaline intraplatform basins in many shelf domains. In the external domains, shallow-marine carbonates, depositional gaps and terrestrial deposits are typical (formations in the Southern Alps, the External Dinarides and the Serbian–Macedonian Massif). From the latest Early Triassic, this latter shelf segment formed a threshold that restricted water circulation from the intraplatform basins. (2) Shallowing-up carbonate successions mark the next stage that implies a period of tectonic quiescence on the shelf from the late Early Anisian to late Middle Anisian. A peculiar change in biota occurring in previously restricted domains was coeval in shallow-marine and deep-marine settings. The biotic change is revealed by observations that dark grey carbonates, which are very poor in fossils, are overlain by carbonate successions rich in fossils typical for normal-marine water. The biota and environmental changes indicate the opening of a passage which allowed the circulation of well-oxygenated and normal-salinity marine water towards the previously restricted depositional areas. The geodynamic setting switching from continental rifting to spreading in the southern sector of the Dinaric–Alpine oceanic branch (Hellenides and Albanides), triggered the opening of the gateway between the future continental margins, i.e., between the External Dinaridic domain (Adria) and Serbian–Macedonian Massif (Eurasia). (3) Following the biotic event in the northern sector of the shelf, subsidence accelerated and additional intraplatform basins opened from the latest Pelsonian.



中文翻译:

新特提斯洋西端中三叠世大陆裂谷开始的沉积方面;来自匈牙利东北部 Silica 和 Torna Nappes 的推论:综述

通过新特提斯洋西端(第纳纪-高山洋支)沉积地层的对比,重建了早三叠世末期大陆裂谷的起始阶段。对来自托尔纳推覆体(位于内西喀尔巴阡山脉南部)的二氧化硅推覆体和博德瓦拉科系列的浅海和盆地地层进行了研究,并与阿尔卑斯山、喀尔巴阡山脉和迪纳里德山脉描述的沉积层序进行了比较。沉积分带是在晚二叠世-早三叠世海侵期间在陆架上发育的,是从早三叠世末期开始解剖和重新排列的。陆架域的相貌和沉积演化差异表明,加速沉降始于早三叠世末期,并与大陆裂谷的发生有关。在研究的时间范围内重建了三个阶段。 (1)深灰色碳酸盐岩沉积于许多陆架域的有限台内盆地和高盐台内盆地中,化石含量极少。在外部区域,浅海碳酸盐岩、沉积间隙和陆地沉积物是典型的(南阿尔卑斯山、外部迪纳里德斯和塞尔维亚-马其顿地块的地层)。从早三叠世末期开始,后陆架部分形成了限制台内盆地水循环的门槛。 (2)浅化的碳酸盐岩层序标志着下一个阶段,这意味着陆架上从早安尼世晚期到中安尼世晚期有一个构造静止期。在以前限制的区域中发生的生物群的特殊变化在浅海和深海环境中是同时发生的。这种生物变化是通过观察深灰色碳酸盐岩(化石含量非常少)被富含正常海洋水典型化石的碳酸盐岩层覆盖而揭示的。生物群和环境的变化表明一条通道的开放,使得氧合良好且盐度正常的海水能够流向先前限制的沉积区域。地球动力学环境从大陆裂谷转变为第纳里克-阿尔卑斯海洋分支(希腊和阿尔巴尼德)南段的扩张,触发了未来大陆边缘之间门户的开放,即外部迪纳里克域(阿德里亚)和塞尔维亚之间的门户–马其顿地块(欧亚大陆)。 (3) 在陆架北段的生物事件之后,沉降加速,并且从最近的佩尔森世开始,更多的台内盆地打开。

更新日期:2022-04-21
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