Ichnofauna record cryptic marine incursions onto a coastal floodplain at a key Lower Mississippian tetrapod site
Ichnofauna record cryptic marine incursions onto a coastal floodplain at a key Lower Mississippian tetrapod site
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DOI：
10.1016/j.palaeo.2016.12.018
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
C. Bennett;A. Howard;S. Davies;T. Kearsey;D. Millward;P. Brand;M. Browne;E. Reeves;J. Marshall
中科院分区：
文献类型：
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作者：
C. Bennett;A. Howard;S. Davies;T. Kearsey;D. Millward;P. Brand;M. Browne;E. Reeves;J. Marshall
下密西西比（图尔奈）沿海平原继承丰富的脊椎动物区系，包括早期四足动物的遗迹化石，记录重复的，短暂的海洋相互作用，影响洪泛平原湖泊的发展和生态系统。该遗迹动物群与其他泥盆纪-石炭纪四足动物遗址的更典型的Scoyenia遗迹相形成对比。在苏格兰边界的Tournaisian Ballagan组中，在500米的连续范围内的128个层位中发现了软骨组织，并与藻管虫形洞穴、Diplocraphalus、Rynocarallium和Zoophycos？的较少出现有关。Chondrites和phycosiphoniform洞穴通常发生在白云岩，解释为一个含盐-高盐湖相组合的一部分，包含一个非海洋到边缘海洋大型动物的双壳类，介形类，Spirorbis，Serpula和sarcopterygian鱼。在不同岩性的18个层位中发现了海相牙形石，其中4个与球粒陨石共生。单殖民化，单层，高遗迹组构指数和薄床（平均10厘米厚）的特点Chondriteshorizons表明：1）不利的环境条件; 2）快速殖民化的沉积物;和3）短暂的生物扰动事件。其他已鉴定的遗迹分类群是Monocraterion和Asterosoma？，它们只出现在漫滩或河流相组合中，在这里被解释为生活在淡水条件下。TheChondritestrace-makers被解释为起源于浅海沃茨，并通过风暴潮事件被运送到洪泛平原湖泊，尽管一些例子表明更重要的海侵。遗迹化石比海洋生物体化石或古齿化石更常见，因此记录了神秘的海洋入侵，否则可能无法识别。这项研究有助于我们了解复杂的镶嵌环境时，陆生四足动物首次出现。
Ichnofossils from a Lower Mississippian (Tournaisian) coastal plain succession with a rich vertebrate fauna, including early tetrapods, record repeated, short-lived marine interactions that influenced floodplain lake development and ecosystems. The ichnofauna contrasts with the more typicalScoyeniaIchnofacies of other Devonian-Carboniferous tetrapod sites. In the Tournaisian Ballagan Formation of the Scottish Borders,Chondritesis identified in 128 horizons within a 500-m succession and is associated with lesser occurrences of phycosiphoniform burrows,Diplocraterion,RhizocoralliumandZoophycos?.Chondritesand phycosiphoniform burrows commonly occur within dolostones, interpreted as part of a saline-hypersaline lake facies association, containing a non-marine to marginal marine macrofauna of bivalves, ostracods,Spirorbis,Serpulaand sarcopterygian fish. Marine scolecodonts are reported from 18 horizons of diverse lithology, four of which co-occur withChondrites. The single-colonisation, single-tier, high ichnofabric index and thin beds (mean 10 cm thick) that characteriseChondriteshorizons indicate: 1) adverse environmental conditions; 2) rapid colonisation of the sediment; and 3) short-lived bioturbation episodes. Other ichnotaxa identified areMonocraterionandAsterosoma?, which occur exclusively within the overbank or fluvial facies associations, and are here interpreted to have lived in freshwater conditions. TheChondritestrace-makers are interpreted as having originated in shallow-marine waters and were transported into floodplain lakes by storm surge events, although a few examples suggest more significant transgressions. Ichnofossils are much more common than marine body fossils or scolecodonts, and thus record cryptic marine incursions that might otherwise remain unidentified. This study contributes to our understanding of the complex mosaic of environments present when terrestrial tetrapods first appeared.