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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=717152
• 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).

遗迹化石也称为痕迹化石，是动物生活行为的化石证据，例如化石洞穴或足迹。化石用于了解岩石记录中的动物（脊椎动物和无脊椎动物）分布，并用于沉积岩以更好地了解沉积物沉积环境。该提案概述了将建立化石化石特征（例如痕迹化石的大小、多样性和分布）与沉积环境参数之间关系的研究。我们将寻求为沉积参数（包括盐度、氧合和沉积速率）提供半定量和定量代理。 盐度压力：咸水代表淡水和正常海水之间的连续体。与咸水沉积物相关的遗迹化石组合具有以下特点：（1）遗迹化石形态多样性低； (2) 形态简单的洞穴结构占优势； （三）小型遗迹化石； (4) 一些物种以高密度存在。这些标准的使用在现代研究中已被反复论证和证实，但其中只有少数尝试将绝对盐度与技术特征联系起来。额外的研究对于加深我们对盐度对动物群落影响的理解至关重要。 氧应激：缺氧是深层和/或隐蔽环境中最典型的特征。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研究表明，沉积水中的低溶解氧浓度导致观察到的洞穴尺寸显着减小，并且Iichnogenera的多样性显着下降。 沉积应力：与高沉积速率引起的应力相关的条件包括高水流速度（限制滤食）和间歇沉积。在现代环境中，这些沉积挑战将生物扰动限制在活动的蠕虫生成的结构中，并且更罕见的是，海葵、甲壳类动物和强壮的双壳类动物在能量环境中占主导地位。浑浊的条件可能伴随着高沉降率，也会对滤食动物产生显着的环境压力。 为上述三个物理化学参数提供量化的技术代理是我的发现补助金的基础。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）。