Abstract Peritidal carbonate-evaporite successions, since they are developed in the transition between continental and marine realms, provide essential keys for palaeobathymetric and palaeoclimatic interpretations. As a result, several facies models have been proposed to assist on the interpretation of ancient tidal flat deposits, and peritidal successions have been extensively used for cyclicity analyses. In this study, well-exposed, Lower Cretaceous peritidal deposits (Oncala Group, Cameros Basin, N Spain) are analysed and compared with the most commonly-used present-day analogues (from Shark Bay, the Arabian Gulf and the Bahamas) and with ancient peritidal successions, providing their palaeoenvironmental and palaeoclimatic interpretation, assessing the usefulness and limitations of the facies models, and evaluating the suitability of these deposits for analysis of decimetre to metre-scale cycles. The studied peritidal deposits consist of thinly-bedded to laminated dolostones, dolomitic stromatolites, stromatolite breccias, flat-pebble and edgewise breccias, and calcite and quartz pseudomorphs after anhydrite nodules. Abundant resemblances of the peritidal deposits of the Oncala Group with those of Shark Bay, including that they are largely composed of microbialites and intraclasts, makes the peritidal deposits of the Oncala Group one of the best fossil analogues of this present-day setting. However, the presence of anhydrite nodules indicates pervasive evaporite precipitation in the supratidal zone, which is a feature that does not occur in supratidal flats of Shark Bay, but is characteristic of arid sabkhas of the Arabian Gulf. Nevertheless, the fact that carbonate-evaporite tidal flats of the Oncala Group were laterally related with siliciclastic tidal flats with large freshwater input and broadly inhabited by dinosaurs, suggests that anhydrites precipitated under less arid climates than those of the Arabian Gulf nowadays, pointing to semiarid climatic conditions during deposition. Moreover, the fact that peritidal deposits with anhydrite nodules were exclusively formed in a low-subsidence area of the Cameros Basin suggests that the rate of accommodation space creation also played an important role in their development. Regarding the comparison with other fossil peritidal sediments, the studied deposits show more abundant similarities with Proterozoic and Cambrian successions, composed mainly of stromatolites, microbial laminites, and intraclasts, than with other Mesozoic peritidal deposits, in which bioclasts and burrowing are usually more abundant. This highlights the difficulties for assigning specific features to certain geological ages. Finally, peritidal facies of the Oncala Group may change laterally and vertically to any other facies, showing a patchy lateral distribution of facies and an unsystematic vertical stacking pattern. The sedimentary features of the stromatolite, breccia and thinly-bedded to laminated carbonate facies do not allow their assignment to a unique tidal zone. Moreover, sedimentary features indicative of subaerial exposure, such as anhydrite nodules formed in the capillary zone, occur within any of the carbonate facies and show limited lateral extent. This results in a succession that cannot be clearly subdivided into subsequent shallowing-upward cycles not even by using erosive surfaces or the anhydrite nodule layers as marker horizons of the upper part of the cycles, because their limited lateral extent prevents reliable correlations. Similar composite lateral and vertical facies relationships have been documented both in the present-day analogues and in ancient successions, which suggests that this kind of facies relationships may be common in peritidal successions and highlights the caution that must be taken when trying to perform cyclicity analysis on them.

中文翻译：

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对碳酸盐蒸发岩周波岩相模型和循环的挑战：来自下白垩纪叠层石矿床的见解（Oncala Group，N西班牙）

摘要 周缘碳酸盐岩-蒸发岩层序发育于大陆界和海洋界之间的过渡地带，为古水深测量和古气候解释提供了重要的关键。因此，已经提出了几种相模型来帮助解释古代潮滩沉积物，并且潮汐序列已被广泛用于周期性分析。在这项研究中，对出露良好的下白垩纪周边沉积物（Oncala Group，Cameros Basin，N西班牙）进行了分析，并与当今最常用的类似物（来自鲨鱼湾、阿拉伯湾和巴哈马）进行了比较，并与古代潮汐序列，提供古环境和古气候解释，评估相模型的有用性和局限性，并评估这些沉积物对分米到米尺度循环分析的适用性。研究的周缘沉积物包括薄层至层状白云岩、白云质叠层石、叠层石角砾岩、扁平卵石和边缘角砾岩，以及硬石膏结核后的方解石和石英假形。Oncala Group 的潮汐沉积物与 Shark Ba​​y 的沉积物有很多相似之处，包括它们主要由微生物岩和碎屑内组成，这使 Oncala Group 的潮汐沉积物成为当今环境中最好的化石类似物之一。然而，硬石膏结核的存在表明在潮上带普遍存在蒸发岩沉淀，这是鲨鱼湾潮上平坦地带不存在的特征，而是阿拉伯湾干旱沙布哈的特征。尽管如此，Oncala 群的碳酸盐蒸发岩潮滩与具有大量淡水输入的硅质碎屑潮滩横向相关并且广泛栖息着恐龙，这一事实表明硬石膏在比当今阿拉伯湾气候更干旱的气候下沉淀，指向半干旱气候条件沉积过程中。此外，带有硬石膏结核的周向沉积物完全形成于 Cameros 盆地的低沉降区域，这一事实表明，容纳空间的形成速度也在其发展中发挥了重要作用。与其他化石周缘沉积物相比，所研究的沉积物与元古界和寒武纪序列的相似性更为丰富，主要由叠层石、微生物层理岩和碎屑组成，与其他中生代潮汐沉积物相比，其中生物碎屑和洞穴通常更丰富。这突出了将特定特征分配给某些地质时代的困难。最后，Oncala 群的潮汐相可能会横向和垂直地转变为任何其他相，显示出不规则的横向分布和不系统的垂直堆叠模式。叠层石、角砾岩和薄层至层状碳酸盐岩相的沉积特征不允许将它们分配到一个独特的潮汐带。此外，表明地下暴露的沉积特征，例如在毛细管带中形成的硬石膏结核，出现在任何碳酸盐相内，并显示出有限的横向范围。这导致无法清楚地细分为后续的向上变浅循环的连续序列，即使使用侵蚀表面或硬石膏结核层作为循环上部的标记层也不行，因为它们有限的横向范围阻止了可靠的相关性。类似的复合横向和垂直相关系在现代类似物和古代序列中都有记录，这表明这种相关系可能在周缘序列中很常见，并强调了在尝试进行周期性分析时必须采取的谨慎措施在他们。