The Dachstein platform was an extensive carbonate platform developed on the westernmost shelf of the Neotethys during the Late Triassic, now preserved in various tectonic units disrupted during the Alpine orogeny. Despite being the focus of a multitude of sedimentological, paleontological and other studies, the demise of this platform remains controversial, with contrasting views on the timing and causes of cessation of its growth, the duration of the gap above, which at many places includes the Triassic-Jurassic boundary (TJB), and the depositional environment of overlying strata.

Here we present new carbonate sedimentological, stable isotope and cyclostratigraphic data from sections in the Transdanubian Range (Hungary) which capture the termination of uppermost Triassic Dachstein Limestone and the onset of Hettangian (Early Jurassic) sedimentation following a hiatus. Previously, the TJB in the Transdanubian Range was regarded as a textbook case of a tectonically-driven platform drowning event or, alternatively, cessation of carbonate production due to emergence caused by a significant sea level fall at the TJB. However, recognition of global biotic change and environmental perturbations at the TJB calls for an assessment of their possible role in the demise of the Dachstein platform.

Oxygen and carbon isotopic composition of bulk carbonates were measured in sections at Kőris-hegy (Bakony Mts.), Tata (Tata Horst), and Vöröshíd (Gerecse Mts.) Paleogeographically, these three sections represent a proximal to distal platform transect. Other sections at Pisznice and Tölgyhát (Gerecse Mts.) yielded additional sedimentological data. The sharp surface separating the Dachstein Limestone from the overlying Jurassic formations carries no or only minimal relief at outcrop scale. Thin section studies reveal small-scale irregularities, stylolites, microborings with ferruginous filling, or a thin clay-rich layer at the TJB, indicative of a submarine, or perhaps polygenetic, hardground. In the first meters of the lowermost Jurassic beds abundant ooids occur, and crinoids become common. In each of the studied sections, an abrupt negative carbon isotope shift is recorded at the TJB, and a gradual rebound to more positive values characterizes the lowermost Jurassic strata. Chemostratigraphy allows correlation with sections elsewhere. In the Transdanubian Range, the initial carbon isotope excursion and at least the first part of the purported main carbon isotope excursion are not preserved due to the gap at the TJB. Combined bio- and cyclostratigraphy of lowermost Jurassic strata permits an astrochronologic duration estimate of the early Hettangian hiatus that was not longer than a few hundreds of thousand years.

Our results highlight the role of submarine erosion, perhaps partly related to acidification, and point to an abrupt change in carbonate production related to the end-Triassic extinction of several groups in the platform system. “Unreefing”, the ecological collapse of reefs, led to a regime shift, the transformation of the rimmed platform to a carbonate ramp, with a significant gap in production and preservation of carbonate sediment. This model is not uniformly applicable to Late Triassic platforms as several of them, unlike the Dachstein platform, survived with unrimmed architecture in the Early Jurassic elsewhere on the Neotethyan shelf. However, the model may explain features of the carbonate platform sedimentary record across other events with reef collapse.

Dachstein平台是三叠纪晚期在新特提斯最西端的陆架上发育的一个广泛的碳酸盐台地，现在被保存在高山造山运动中被破坏的各种构造单元中。尽管该平台是众多沉积学，古生物学和其他研究的重点，但该平台的灭亡仍然存在争议，就其增长的时间和原因，上述差距的持续时间（在许多地方包括三叠纪-侏罗纪边界（TJB）和上覆地层的沉积环境。

在这里，我们从跨丹布努山脉（匈牙利）的剖面中呈现了新的碳酸盐岩沉积学，稳定的同位素和环地层数据，这些数据捕获了最高三叠纪达赫斯坦石灰岩的终止和裂隙后黑唐古纪（早侏罗世）沉积的开始。以前，跨丹布尼山脉的TJB被认为是构造驱动的平台溺水事件或由于TJB的海平面下降引起的涌现而停止碳酸盐生产的教科书案例。然而，TJB对全球生物变化和环境扰动的认识要求评估它们在Dachstein平台灭亡中的可能作用。

在古地理上的Kőris-hegy（Bakony Mts。），Tata（Tata Horst）和Vöröshíd（Gerecse Mt.）的剖面中测量了大块碳酸盐的氧气和碳同位素组成，这三个剖面代表了从近到远的平台断面。皮什尼采（Pisznice）和托格哈特（Tölgyhát）（格里塞斯山（Gerecse Mt.））的其他部分也提供了更多的沉积学数据。将Dachstein石灰岩与上覆的侏罗系地层分开的锋利表面在露头尺度上没有或只有很少的起伏。薄断面研究表明，小规模的不规则性，花岗石，带有铁质填充物的微孔或TJB处富含粘土的薄层，表明有海底或多基因的硬地层。在侏罗纪最下层的前几米，出现了丰富的卵母质，并且卵母质也很常见。在每个研究的部分中 在TJB处记录到一个突然的负碳同位素位移，逐渐回弹到更正的值是最侏罗纪地层的特征。化学地层学允许与其他部分相关。在Transdanubian范围内，由于TJB处的间隙，未保留初始碳同位素偏移和至少第一部分声称的主要碳同位素偏移。最下面的侏罗纪地层的生物地层和旋回地层学相结合，使得Hettangian早期裂隙的天文年限估计不超过几十万年。由于TJB处的间隙，最初的碳同位素偏移和至少第一部分声称的主碳同位素偏移无法保留。最下面的侏罗纪地层的生物地层和旋回地层学相结合，使得Hettangian早期裂隙的天文年限估计不超过几十万年。由于TJB处的间隙，最初的碳同位素偏移和至少第一部分声称的主碳同位素偏移无法保留。最下面的侏罗纪地层的生物地层和旋回地层学相结合，使得Hettangian早期裂隙的天文年限估计不超过几十万年。

我们的结果强调了海底侵蚀的作用，可能部分与酸化有关，并指出与平台系统中几类三叠纪末期灭绝有关的碳酸盐生产突然改变。“未礁”是礁石的生态崩溃，导致了政权转移，有边缘平台向碳酸盐岩坡道的转变，在碳酸盐沉积物的生产和保存方面存在巨大差距。该模型不适用于三叠纪晚期平台，因为其中的几个与Dachstein平台不同，在Neotethyan架子上其他地方的侏罗纪早期以无边缘的架构幸存下来。但是，该模型可能解释了其他与礁石塌陷有关的事件中碳酸盐台地沉积记录的特征。