Seilacherian Ichnofacies have been established, to date, for characterizing relatively stable depositional settings. Environments characterized by temporally and spatially varying physico-chemical stresses, however, have languished and been described ichnologically in the context of their “departures” from the archetypal expressions of otherwise ambient environments. Correspondingly, discrimination between shoreface and marine deltaic deposits have been addressed mainly by identifying variations in the individual trace-fossil suites without an over-arching ichnological model. Based on trace-fossil suites reported from globally distributed strata throughout the Phanerozoic, the case can now be made for erecting two new temporally and geographically recurring Seilacherian Ichnofacies for marine deltaic successions—the Phycosiphon Ichnofacies for muddy prodelta environments and the Rosselia Ichnofacies for sandy delta-front settings.The Phycosiphon Ichnofacies is characterized by variable bioturbation intensities (BI 0–5), although many sandstone and mudstone beds may have very low bioturbation intensities (BI 0–1), pointing to their rapid, event-style deposition. Most biogenic structures record grazing or deposit-feeding behaviors, with subordinate horizontal dwellings that reflect deposit feeding and/or carnivory. Meiofaunal cryptic bioturbation is locally present in tempestites. Episodic deposition is accompanied by common escape structures and locally, sediment-swimming structures. The Phycosiphon Ichnofacies typically shows beds characterized by diverse, fully marine trace-fossil suites intercalated with discrete beds dominated by low-diversity, facies-crossing traces. Such bed-scale juxtaposition points to short-term but recurring alternations between stable marine conditions and physico-chemically stressed conditions.The Rosselia Ichnofacies is also characterized by variable (BI 0–5; though typically BI 0–3) bioturbation intensities and sporadically distributed burrows. Most ichnogenera record deposit-feeding behaviors, many associated with vertically and horizontally oriented permanent dwelling structures. Dwelling structures commonly display re-equilibration and escape structures are typically abundant, both characteristic of elevated sedimentation rates and sporadic deposition. Most spreitenated structures are markedly retrusive, also attesting to elevated rates of sedimentation. Cryptic bioturbation is only locally abundant, particularly associated with erosionally amalgamated tempestites lacking mudstone drapes. While many of the trace fossils constitute facies-crossing elements, fully marine (ambient) ichnogenera also occur in some suites. Associated mudstone interbeds display low BI values, sediment-swimming structures, and top-down bioturbation, consistent with their rapid deposition as fluid mud.The two ichnofacies may pass gradationally into one another vertically, associated with lobe progradation or autogenic lobe abandonment. Further, the two ichnofacies may pass along depositional strike into their non-deltaic counterparts—the Phycosiphon Ichnofacies grading into the Cruziana Ichnofacies in distal positions, and the Rosselia Ichnofacies passing into the Skolithos Ichnofacies in shallow-water locales.The erection of these new ichnofacies will enhance the reliable identification of deltaic successions, particularly in wave-dominated settings, and their differentiation from classical strandplain shoreface deposits. As well, the two ichnofacies better explain animal–substrate relations in the context of the detailed sedimentological characteristics of delta deposits, refining the overall facies characterization of shallow-marine environments.

中文翻译：

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Phycosiphon眼相和Rosselia眼相：海洋三角洲环境的两种新的眼相

迄今为止，已经建立了Seilacherian岩相，以表征相对稳定的沉积环境。然而，以时间和空间变化的物理化学应力为特征的环境，在其“背离”环境的基础上，与其他周围环境的原型表达相比，已陷入困境，并在语言学上进行了描述。相应地，主要通过识别单个痕迹化石组中的变化而没有总体的动物学模型来解决海岸面和海洋三角洲沉积之间的区别。根据整个古生代的全球分布地层报告的微量化石组，现在可以为海洋三角洲演替建立两个新的在时间和地理上重复出现的Seilacherian优势相-泥泞三角洲环境的Phycosiphon优势相和三角洲前沙质环境的Rosselia优势相。Phycosiphon优势相的特点是（可变生物扰动0-5），尽管许多砂岩和泥岩床可能具有很低的生物扰动强度（BI 0-1），这表明它们是快速的事件型沉积。大多数生物成因结构记录着放牧或沉积物进食的行为，而附属的水平住宅则反映了沉积物的进食和/或食肉动物。睑板隐生物扰动局部存在于风暴中。间歇沉积伴随着常见的逃逸结构以及局部的沉积物游动结构。Phycosiphon Ichnofacies通常显示的床具有多种多样的，完整的海洋痕迹化石套件，并插有以低多样性，相交痕迹为主的离散床。这种床规模的并置指示稳定的海洋条件和物理化学胁迫条件之间的短期但经常性的交替。Rosselia优势相的特征还在于生物扰动强度可变（BI 0-5；虽然通常为BI 0-3），并且其分布呈零星分布洞穴。大多数鱼腥草记录了沉积物的进食行为，许多行为与垂直和水平方向的永久住所结构有关。居住结构通常显示出重新平衡，逃逸结构通常很丰富，具有增加的沉积速率和零星沉积的特征。大多数有斑点的结构都具有明显的回缩性，也证明了沉降速率的提高。隐性生物扰动仅在局部存在，特别是与缺乏泥岩悬垂物的侵蚀性合并的暴风雨有关。虽然许多痕迹化石构成了相交元素，但在某些套件中也出现了完全海洋（环境）的鱼腥草。伴生的泥岩夹层显示出较低的BI值，沉积物游动结构和自上而下的生物扰动，这与它们作为流体泥浆的快速沉积相一致。这两个no相可能会垂直渐进地彼此相交，这与叶的发育或自生的叶的遗弃有关。此外，这两个鱼眼相可能会沿着沉积走向进入其非三角相对应的区域中—虹吸虫眼相在远侧位置会分级为克鲁齐亚纳河相，这些新的岩相的建立将增强对三角洲演替的可靠识别，特别是在波浪为主的地区，并将它们与经典的平原平原海岸沉积物区分开来。同样，在三角洲沉积物的详细沉积学特征的背景下，这两个鱼类相更好地解释了动物与基底的关系，从而完善了浅海环境的总体相特征。