The Pannonian Basin, a major back-arc basin in the Alpine–Carpathian orogenic belt, experienced its syn-rift phase during the Early–Middle Miocene. Studying coeval sediments can provide important information on the initiation of the extension. This paper investigates syn-rift deposits in the Mecsek Mts. in SW Hungary from a tectono-sedimentary aspect, using stratigraphy, palaeontology and structural observations to constrain palaeoenvironments and their tectonic background. Our study shows that in the Mecsek area the widespread Early Miocene fluvial sedimentation was not directly followed by inundation by the Central Paratethys sea, instead, a phase of lacustrine deposition in the Karpatian–Early Badenian (late Burdigalian–early Langhian) preceded the marine flooding. The lake sediments have a low-diversity but abundant, endemic mollusc and ostracod fauna, dominated by the bivalve Congeria boeckhi and the gastropod Ferebithynia vadászi . Identical faunas at various sites indicate that “Lake Mecsek” was a single water body, covering the present-day Mecsek Mts. and their surroundings. Wedge-shaped clastic bodies along faults, fault scarp breccias and semi-soft sediment deformations suggest that extensional tectonic activity related to the rifting of the Pannonian Basin played a role in lake basin formation. The accumulation of lakes was probably also enhanced by increased precipitation during the Miocene Climatic Optimum. The Central Paratethys flooded the area in the Badenian (Langhian) and deposited normal marine sediments over the lacustrine ones. Considering the fauna, the sedimentary succession, the structural background and evolution history, the Mecsek area seems to be part of the Illyrian bioprovince and related to the Dinaride Lake System.

中文翻译：

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Mecsek山中的中新世同裂谷湖沉积物。（匈牙利西南部）

Pannonian盆地是高山-喀尔巴阡造山带的主要后弧盆地，在中新世中期至中期经历了同理裂陷阶段。研究近代沉积物可以提供有关扩展开始的重要信息。本文研究了梅切克山上的裂谷沉积物。匈牙利西南部从构造-沉积的角度出发，利用地层学，古生物学和结构性观测来限制古环境及其构造背景。我们的研究表明，在麦切克地区，中中新世河流相的广泛沉积并没有直接被中央帕拉提斯海域淹没，相反，Karpatian-Badenian早期（Burdigalian-Langhian晚期）的湖相沉积是在海洋洪水之前发生的。 。湖泊沉积物多样性低，但丰富， Congeria boeckhi 和腹足纲 Ferebithyniavadászi 。各个地点的相同动物区系表明“迈奇克湖”是一个单一的水体，覆盖了当今的迈奇克山。及其周围环境。沿断层的楔形碎屑体，断层陡角角砾岩和半软性沉积物变形表明，与盘尼诺盆地裂谷有关的伸展构造活动在湖盆形成中起作用。在中新世最佳气候期间，降水的增加也可能增加了湖泊的积累。中央Paratethys淹没了巴登尼亚（Langhian）地区，并在湖相上沉积了正常的海洋沉积物。考虑到动物区系，沉积演替，结构背景和演化历史，麦切克地区似乎是伊利里亚生物省的一部分，并与迪纳里德湖系统有关。