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 - 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。遗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）分布以及沉积岩。该提案概述了将建立化石特征（例如痕迹化石的大小、多样性和分布）与沉积之间关系的研究。我们将寻求提供沉积参数的半定量和定量代理，包括盐度、氧合和沉积速率：咸水代表淡水和正常海水之间的连续体，其特征是与咸水中沉积物相关的痕量化石组合。按具体特征：（1）痕迹化石形式多样性低；（2）形态简单的洞穴结构占主导地位；（3）小型痕迹；化石；（4）一些高密度存在的物种在现代研究中已被反复证明和证实，但其中只有少数尝试将绝对盐度与物种特征联系起来。加深我们对盐度对动物群落影响的理解：缺氧是深层和/或庇护环境中最典型的现象，通常，氧应激伴随着氧气的缓慢积累。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，并且沉积物的多样性显着降低：与沉积应力相关的条件。高沉降率引起的应力包括高流速（限制滤食）和间歇性沉降，在现代环境中，这些沉积挑战限制了蠕虫产生的活动结构的生物扰动。而且，更罕见的是，海葵、甲壳类动物和强壮的双壳类动物在高沉降率的情况下占主导地位，也对滤食性动物产生了显着的环境压力。我的发现补助金的基础是用于解决所提出的研究跨越地质时间的数据集，并提出了多种方法，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）。