Ichnofossils as Environmental Proxies

遗迹化石也被称为痕迹化石，是动物生活行为的化石证据，如化石洞穴或足迹。遗迹化石被用来了解岩石记录中动物(脊椎动物和无脊椎动物)的分布，并用于沉积岩更好地了解沉积物沉积的环境。该提案概述了将确定遗迹化石特征(例如遗迹化石的大小、多样性和分布)与沉积环境参数之间关系的研究。我们将寻求提供包括盐度、含氧量和沉积速率在内的沉积参数的半定量和定量替代。 盐度胁迫：微咸水代表淡水和正常海水之间的连续体。与微咸水沉积物有关的遗迹化石组合具有以下特点：(1)遗迹化石形式多样性低；(2)形态简单的洞穴结构占优势；(3)遗迹化石较小；(4)一些遗迹物种密度较高。这些标准的使用在现代研究中得到了反复的证明和证实，但其中只有几个标准试图将绝对盐度与生物特征联系起来。额外的研究对于完善我们对盐度对底栖动物群落的影响的理解是至关重要的。 氧气压力：在深层和/或有遮挡的环境中，缺氧是最常见的特征。通常，氧气胁迫伴随着细粒沉积物的缓慢堆积。一些现代和许多岩石记录研究表明，沉积水中的低溶解氧浓度导致所观察到的洞穴的大小显著减小，遗迹属的多样性显著减少。 沉积应力：与高沉降率引起的应力有关的条件包括高流速(限制过滤进料)和间歇性沉积。在现代环境中，这些沉积挑战将生物扰动限制在能动的蠕虫生成的结构上，更罕见的是，线虫、甲壳类和健壮的双壳类主导着能量环境。混浊条件可能伴随着高沉降率，也对滤食性动物施加了显著的环境压力。 为上述三个物理化学参数提供量化的生物化学指标是我的发现基金的基础。用于处理拟议研究的研究项目使用从寒武纪到现代和基于实验室的研究的数据集，跨越地质时间。提出了多种方法，包括可视化技术(X射线、CT、高光谱成像)、成分评价(XRF、X射线衍射、ICPMS、岩石学)和现场技术(露头分析、现代沉积环境)。

An ichnofossil also referred to as trace fossil is fossil evidence, such as fossil-burrows or -tracks, of an animal's living behaviours. Ichnofossils are used to understand animal (vertebrate and invertebrate) distributions in the rock record and for sedimentary rocks to better understand environments of sediment deposition. This proposal outlines research that will establish relationships between ichnofossil characteristics (e.g. size, diversity and distributions of trace fossils) and sedimentary environment parameters. We will seek to provide semiquantitative and quantitative proxies for sedimentary parameters including salinity, oxygenation and sedimentation rate. Salinity Stress: Brackish water represents a continuum between fresh and normal marine water. Trace fossil assemblages associated with sediments deposited in brackish water are characterized by specific characteristics: (1) low diversity of trace fossil forms; (2) preponderance of morphologically simple burrow structures; (3) diminutive trace fossils; and, (4) some ichnospecies present in high densities. The use of these criteria has been repeatedly demonstrated and confirmed in modern studies, but only a few of these have attempted to associate absolute salinity with ichnological characteristics. Additional research is essential to refine our understanding of the influence of salinity on infaunal communities. Oxygen Stress: Oxygen deficiency is most characteristic in deep, and/or sheltered environments. Normally, oxygen stress is accompanied by the slow accumulation of fine-grained sediments. Some modern and many rock-record studies have shown that low dissolved-oxygen concentrations in depositional waters induce a noticeable reduction in the size of the burrows observed and the diversity of ichnogenera decreases markedly. Sedimentation Stress: Conditions related to the stresses induced by high sedimentation rates include high current velocities (limiting filter feeding) and episodic sedimentation. In modern settings, these sedimentary challenges limit bioturbation to motile worm-generated structures and, more rarely, anenomes, crustaceans and robust bivalves dominate energetic settings. Turbid conditions, which may accompany high sedimentation rates, also exert a significant environmental stress on filter-feeding animals. Providing quantified ichnological proxies for the above three physico-chemical parameters is the basis of my Discovery Grant. The research projects used to address the proposed research span geological time using datasets from the Cambrian through to modern and laboratory-based studies. Multiple methods are proposed, including visualization techniques (X-ray, CT, hyperspectral imaging), compositional assessments (XRF, XRD, ICPMS, petrography), and field techniques (outcrop analysis, modern sedimentary environments).