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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Ophiomorpha irregulaire, Mesozoic trace fossil that is either well understood but rare in outcrop or poorly understood but common in core
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Ophiomorpha irregulaire, Mesozoic trace fossil that is either well understood but rare in outcrop or poorly understood but common in core

机译：Ophiomorpha irregulaire，中生代痕迹化石，要么很好理解，但在露头中很少见，或者很少了解，但在核心中很常见

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摘要

The distinctive trace fossil, Ophiomorpha irregulaire, differs from other ichnospecies of Ophiomorpha in the so-called "meander maze" configuration of its horizontal course, and by the possession of unevenly distributed, elongated, tapering wall-lining pellets. The ichnospecies has been described, without doubt, from only two outcrop localities, both Late Cretaceous in age and both lying within the Cretaceous Western Interior Seaway. Only a single, almost convincing example of the trace fossil has been reported elsewhere, in a Lower Jurassic outcrop in Italy. Apart from this last occurrence, the distribution of O. irregulaire in outcrop suggests that the trace fossil has a restricted time span and geographical range. In contrast, O. irregulaire is identified more commonly in cores. and these occurrences show no clear geographical restrictions and are reported in sediments of Jurassic as well as Cretaceous age. Outcrop exposures of Jurassic and Cretaceous sediments have been extensively studied by ichnologists and if the large, eye-catching O. irregulaire were as common as is suggested by core material, then the trace fossil would not have escaped notice in outcrop. Identification of the trace fossil in core is generally made on the basis of two-dimensional, vertical sections. The characteristic meander maze form cannot be seen in this view, and the identification is thus based almost entirely on the special shape of the lining pellets. As is well known, the identification of large trace fossils in the restricted format of core lacks the security of extensively exposed trace fossils in outcrop. The discrepancy between age and geographic distribution of O. irregulaire in outcrop and core suggests that some misidentification is occurring in core analysis.
机译：独特的痕迹化石Ophiomorpha irregulaire与其他Ophiomorpha鱼类物种的不同之处在于其水平走向的所谓“曲折迷宫”构造，并且拥有不均匀分布的，细长的，逐渐变细的壁衬颗粒。毫无疑问，仅在两个露头地区描述了鱼类物种，年龄都在白垩纪晚期，并且都位于白垩纪西部内陆海道内。在意大利下侏罗纪露头的其他地方，仅报道了一个几乎令人信服的微量化石实例。除了最后一次发生以外，露头兽的分布还表明痕量化石的时间跨度和地理范围有限。相反，O。irregulaire在核心中更常见。这些事件没有明确的地理限制，据报道在侏罗纪和白垩纪的沉积物中。鱼眼学家对侏罗纪和白垩纪沉积物的露头暴露进行了广泛的研究，如果大型，引人注目的O. irregulaire与核心材料所暗示的一样普遍，那么微量化石就不会在露头中逃脱。岩心中痕量化石的鉴定通常是基于二维的垂直剖面进行的。在该视图中看不到特有的曲折迷宫形式，因此识别几乎完全基于衬丸的特殊形状。众所周知，以受限的岩心形式识别大型痕迹化石缺乏露头中广泛暴露的痕迹化石的安全性。在露头和岩心中O. irregulaire的年龄和地理分布之间的差异表明，岩心分析中发生了一些误认。

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