Ichnofossils as Environmental Proxies

化石作为环境指标

• 批准号: RGPIN-2020-05138
• 负责人: Gingras, Murray
• 金额: $ 4.44万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750896
• 关键词: Ichnofossils; Environmental; Proxies

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).

遗迹化石（英语：ichnofos化石），也称为痕迹化石，是动物生活行为的化石证据，如化石洞穴或足迹。遗迹化石用于了解动物（脊椎动物和无脊椎动物）在岩石记录中的分布，并用于沉积岩，以更好地了解沉积物沉积的环境。该提案概述了将建立遗迹化石特征（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。我们将寻求提供沉积参数，包括盐度，氧化和沉积速率的半定量和定量代理。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征：（1）遗迹化石类型多样性低;（2）以形态简单的洞穴结构为主;（3）遗迹化石小;（4）某些遗迹种密度高。这些标准的使用在现代研究中已被反复证明和证实，但只有少数研究试图将绝对盐度与遗迹学特征联系起来。进一步的研究是必不可少的，以完善我们的盐度对底栖动物群落的影响的理解。 氧气压力：缺氧是最典型的深，和/或遮蔽的环境。通常，氧胁迫伴随着细粒沉积物的缓慢积累。一些现代和许多岩石记录的研究表明，低溶解氧浓度的沉积沃茨诱导观察到的洞穴的大小和遗迹属的多样性显着减少。 沉降应力：与高沉积速率引起的应力有关的条件包括高流速（限制过滤器进料）和间歇性沉积。在现代环境中，这些沉积物的挑战限制了生物扰动运动蠕虫产生的结构，更罕见的是，anenomes，甲壳类动物和强大的双壳类动物占主导地位的充满活力的设置。浑浊的条件，可能伴随着高沉降率，也施加了重大的环境压力滤食性动物。 提供上述三个物理化学参数的量化遗迹学替代物是我的发现资助的基础。用于解决拟议研究的研究项目跨越地质时间，使用从寒武纪到现代和基于实验室的研究的数据集。提出了多种方法，包括可视化技术（X射线，CT，高光谱成像），成分评估（XRF，XRD，ICPMS，岩相学）和现场技术（露头分析，现代沉积环境）。