Vertebrate remains and conodonts in the upper Silurian Hamra and Sundre formations of Gotland, Sweden
Vertebrate remains and conodonts in the upper Silurian Hamra and Sundre formations of Gotland, Sweden
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DOI：
10.1080/11035897.2019.1655790
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发表时间：
2019-09
期刊：
影响因子：
1
通讯作者：
Oskar Bremer;E. Jarochowska;T. Märss
中科院分区：
文献类型：
--
作者：
Oskar Bremer;E. Jarochowska;T. Märss
摘要 瑞典哥特兰岛的地质研究历史悠久，已经得出了基于哥特兰沉积层序牙形刺的详细生物地层学，但哈姆拉地层和桑德雷地层（哥特兰岛南部最年轻的地层）之间的关系仍然没有得到很好的解决。与该系列的其他部分相比，这些构造在脊椎动物方面的描述仍然相对较少。对博物馆藏品和新采样材料的调查表明，与底层的布尔斯维克砂岩和鲕粒岩成员相比，脊椎动物群的分类组成和丰富度仍然相似。然而，各个类群的相对丰度发生了变化：Paralogania ludlowiensis 和罕见的 Tahulaspis sp. 骨甲纲残骸。仅出现在哈姆拉组下部的样本中，而 Thelodus sculptilis 在 Sundre 组的样本中更为常见。牙形刺和同位素数据支持了之前的建议，即哈姆拉和桑德雷地层可能在很大程度上是同步的，并且观察到的脊椎动物区系差异可能反映了沉积环境的变化。哥特兰岛的这一区间被认为代表了东波罗的海部分的中断，其中较年轻的地层显示棘皮动物在脊椎动物群中的重要性增加。因此，哥特兰可以深入了解志留世晚期颚口类动物多样化的早期阶段。然而，这必须结合其他地区的数据，以及对波罗的海盆地志留纪棘皮动物基于尺度的分类法的审查和修订。
ABSTRACT A long history of geological research on the island of Gotland, Sweden, has resulted in a detailed biostratigraphy based on conodonts for the Gotland sedimentary succession, but the relation between the Hamra and Sundre formations, the youngest strata on southern Gotland, has remained poorly resolved. These formations have also remained relatively poorly described in terms of vertebrates compared to other parts of the succession. A survey of museum collections and newly sampled material reveal that the taxonomical compositions and richness of vertebrate faunas remain similar compared to the underlying Burgsvik Sandstone and Oolite members. However, the relative abundance of the respective groups changes: Paralogania ludlowiensis and rare osteostracan remains of Tahulaspis sp. only occur in samples from the lower Hamra Formation, while Thelodus sculptilis becomes more common in samples from Sundre Formation. Conodont and isotope data give support to previous suggestions that the Hamra and Sundre formations may be largely isochronous, and it is possible that the observed differences in vertebrate faunas reflect changes in depositional setting. This interval on Gotland has been suggested to represent a hiatus in the East Baltic sections, where younger strata show an increased importance of acanthodians in the vertebrate faunas. Gotland could therefore give insights into the early stages of this diversification of gnathostomes during late Silurian times. However, this has to be done in combination with data from other areas, as well as with a review and revision of the scale-based taxonomy of Silurian acanthodians from the Baltic Basin.