The Bichordites ichnofabric in the Pleistocene ocean current-generated sand ridge complex
The Bichordites ichnofabric in the Pleistocene ocean current-generated sand ridge complex
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更新世洋流生成的沙岭复合体中的双绳石结构
DOI：
10.7203/sjp.29.2.17801
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Masakazu Nara
中科院分区：
文献类型：
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作者：
Masakazu Nara
以 Bichordites monastiriensis 为特征的地层结构首次报道于日本房总半岛中更新世市地组洋流生成的陆架沙脊复合体的大型水下沙丘（沙波）沉积物中，Bichordites monastiriensis 是一种棘心类海胆化石洞穴。它由占主导地位的 B. monastiriensis 和相关的 Alcyonidiopsis、大型 Macaronichnus、Piscichnus、Scolicia、Skolithos 和未命名的逃逸结构组成。从新近纪到第四纪，类似的以双斜纹藻为主的沉积物已被报道，这些沉积物是由各种因素（如潮汐流、风暴诱发流或好天气波浪产生的流）形成的，其沉积环境范围从深海底到浅陆架。尽管沙波系统通常以快速沉积和高度移动的基质为特征，阻止了大多数底栖动物的定殖，但无论主要的沉积介质或栖息地的水深如何，棘心虫等快速穴居动物很可能能够栖息在这些地区。比索石的化石记录可以追溯到渐新世，尽管痕迹化石在中新世变得特别常见，并且已知的痕迹化石（即棘心化石和马雷蒂化石）出现在始新世。此外，现在描述的这些追踪器可以用作高度移动基质的指示器，例如新生代沙波系统中发现的基质
The ichnofabric characterised by Bichordites monastiriensis, a fossil burrow of the echinocardiid spatangoid echinoid, is first reported from the large-scale subaqueous dune (sand wave) deposits of the ocean current-generated shelf sand ridge complex of the middle Pleistocene Ichijiku Formation of the Boso peninsula, Japan. It consists of dominant B. monastiriensis and associated Alcyonidiopsis, large Macaronichnus, Piscichnus, Scolicia, Skolithos and unnamed escapes structures. Similar Bichordites-dominant ichnofabrics have been reported from Neogene to Quaternary sand wave deposits formed by various agents (such as tidal currents, storm-induced currents, or fair-weather wave-generated currents) whose depositional environments range from the deep sea floor to the shallow shelf. Although sand wave systems are commonly characterised by rapid sedimentation and highly shifting substrates, preventing colonisation by most benthic animals, rapid burrowers such as the echinocardiids were likely able to inhabit these regions regardless of the dominant depositional agents or the water depths of the habitats. The fossils record of Bichordites dates back to the Oligocene, although the trace fossil became particularly common in the Miocene and the known tracemakers (i.e., the echinocardiids and the maretiids) appeared in the Eocene. Moreover, these tracemakers now described here may be used as an indicator of highly shifting substrates, such as those found in sand wave systems, in the Cenozoic