Firm evidence for a post‐extinction ichnofauna: earliest CarboniferousCruziana reticulataassemblage from the Anti‐Atlas of Morocco
Firm evidence for a post‐extinction ichnofauna: earliest CarboniferousCruziana reticulataassemblage from the Anti‐Atlas of Morocco
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DOI：
10.1111/let.12345
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发表时间：
2019
期刊：
影响因子：
1.5
通讯作者：
R. Hofmann;Benjamin Gutwasser;H. Hüneke;D. Korn
中科院分区：
文献类型：
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作者：
R. Hofmann;Benjamin Gutwasser;H. Hüneke;D. Korn
Cruziana reticulatais是一个节肢动物相关的遗迹种，其特征是一个明显的网状划痕模式，其最初的形成和后来的保存需要在浅海细粒底质中存在固结基质。在两种情况下，表层至浅层底栖生物可能会接触到坚实的硅质底质：第一，在沉积柱的上部、水饱和和通常较软的部分受到侵蚀后，压实的底部暴露;第二，在没有生物沉积物混合的情况下，初级快速底质稳定。而第一种模式发生在整个中生代，后者只流行于早古生代的海底，主要是由于发育不良的底栖生物扰动。然而，通过消灭穴居生物，大规模灭绝（即二叠纪末灭绝）被称为“重置”生态空间利用的强度，这需要回到这种不合时宜的风格的痕迹化石保存在年轻的时候。来自摩洛哥的以Cruziana reticulata为主的最早石炭纪遗迹组合证明了在汉根贝格事件（泥盆纪末期的一次大灭绝）之后，坚固基质的扩散。由于侵蚀的证据是缺乏伴随的沉积岩和遗迹组合显示的营养泥质海底的机会主义开发的特点，我们赞成这个组合的解释，代表灭绝后的遗迹动物群。它表明，其他分类学上不太严重的大规模灭绝也可能在开放的海洋生态系统中表现出短暂但严重的生态影响，如重要沉积物混合的崩溃。这种灭绝后的影响可能会扭曲地层记录的看法，作为一个firmground遗迹组合往往被视为海底侵蚀的证据，是至关重要的突出层序边界。因此，我们鼓励欣赏各自遗迹动物群的宏观进化框架。
Cruziana reticulatais an arthropod-related ichnospecies that is characterized by a conspicuous net-like scratch pattern whose initial formation and later preservation require the presence of consolidated substrates in shallow marine fine-grained bottoms. There are two scenarios in which epifaunal to shallow infaunal benthic organisms may access firm siliciclastic substrates: first, by exposure of the compacted bottom after erosion of the upper, water-saturated and usually soft portion of sediment column; and, second, by primary fast substrate stabilization in the absence of biogenic sediment mixing. Whereas the first mode occurs throughout the Phanerozoic, the latter is only prevalent in marine bottoms during the Early Palaeozoic mainly as a consequence of poorly developed infaunal bioturbation. However, by eradicating burrowing organisms, mass extinctions are known (i.e. the end-Permian extinction) to ‘reset’ intensity of ecospace utilization, which entails the return to this anachronistic style of trace fossil preservation in younger times. An earliest Carboniferous ichno-assemblage dominated byCruziana reticulatafrom Morocco attests the spread of firm substrates in the aftermath of the Hangenberg Event – a major extinction at the end of the Devonian period. Since evidence for erosion is lacking in accompanying sedimentary rocks and the ichno-assemblage shows characteristics of opportunistic exploitation of the nutritious muddy seabed, we favour the interpretation of this assemblage to represent a post-extinction ichnofauna. It shows that other taxonomically less severe mass extinctions may also exhibit transient but severe ecological effects in open marine ecosystems such as the collapse of vital sediment mixing. Such post-extinction effects may distort the perception of the stratigraphical record as a firmground ichno-assemblage often taken as evidence for submarine erosion and are crucial in highlighting sequence boundaries. We, thus, encourage appreciating macroevolutionary framework of respective ichnofaunas.