Trace fossil preservation and the early evolution of animals
Trace fossil preservation and the early evolution of animals
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DOI：
10.1016/j.palaeo.2003.09.035
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发表时间：
2005-05-02
影响因子：
3
通讯作者：
Gehling, JG
中科院分区：
文献类型：
--
作者：
Jensen, S;Droser, ML;Gehling, JG
遗迹化石记录是讨论两侧对称动物出现时间的重要因素。一个保守的方法不延长这一记录超过约560-555 Ma。利用遗迹化石探测早期底栖活动的关键是在沉积物-水界面附近留下的遗迹的澄清潜力。我们对寒武纪最早期沉积物的研究表明，浅地层的保存程度比大部分古生代的典型地层要高。这可直接或间接归因于沉积物混合程度低。低水平的沉积物混合意味着薄事件床被保存。浅深度的沉积物混合也意味着泥质沉积物是坚定的接近沉积物-水界面，增加的可能性，记录浅层痕迹化石在泥质沉积物。在这种类型的设置保存survival痕迹化石仍然存在问题，但上述因素表明，也可以预期这些都留下了合理的记录。总的来说，可以预期的痕迹化石记录提供了一个良好的记录开始两侧底栖活动。缺乏令人信服的痕迹化石显着之前的寒武纪支持宏观底栖bilaterians晚出现的模式。(c)2004 Elsevier B. V.保留所有权利。
The trace fossil record is an important element in discussions of the timing of appearance of bilaterian animals. A conservative approach does not extend this record beyond about 560-555 Ma. Crucial to the utility of trace fossils in detecting early benthic activity is the preservational potential of traces made close to the sediment-water interface. Our studies on the earliest Cambrian sediments suggest that shallow tiers were preserved to a greater extent than typical for most of the Phanerozoic. This can be attributed both directly and indirectly to the low levels of sediment mixing. The low levels of sediment mixing meant that thin event beds were preserved. The shallow depth of sediment mixing also meant that muddy sediments were firm close to the sediment-water interface, increasing the likelihood of recording shallow tier trace fossils in muddy sediments.Preservation of surficial trace fossils in this type of setting remains problematic but the above factors suggest that also these can be expected to have left a reasonable record. Overall, the trace fossil record can be expected to provide a sound record of the onset of bilaterian benthic activity. The lack of convincing trace fossils significantly before the Cambrian supports models of late appearance of macroscopic benthic bilaterians. (c) 2004 Elsevier B.V. All rights reserved.