Plugging the preservational pipeline: an integrated approach to tracking taphonomic histories of Cambrian skeletal fossil assemblages

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Not all organisms have the same likelihood of being preserved in the fossil record. There are a variety of limiting factors (biological and/or physical) operating in the environment which can filter out more vulnerable forms prone to decomposition. Typically, only the hard skeletons of animals are preserved (i.e. bones, teeth, and shells), however does this mean that the skeletal record itself is reliable? To avoid biasing our view of the history of life on our planet this project will probe the skeletal record for leaks in the 'preservational pipeline'. This project targets perhaps the most important period of geological time known as the Cambrian Period (541-488 million years ago), during which animal life as we know it evolved and diversified. This project includes a multidisciplinary group of researchers who will sample Cambrian-aged rocks and small shelly fossils from the Ikara-Flinders Ranges of South Australia to address the following questions: What proportion of the skeletal fossil record is missing? What environmental conditions were required for the preservation of these shelly animals? And how reliable are these fossil datasets in preserving particular animal groups or for subdividing geological time? To address these questions the team will use a combination of field and lab-based sedimentological, geochemical, and fossil data, as well as advanced imaging techniques (micro-CT and 3D visualization software), to reconstruct past environments and assess the impact of preservation bias on these fossilized communities. This integrated approach has the potential to fundamentally change how paleontologists analyze and track bias in the fossil record. In addition, the project will include training for university undergraduate and graduate students with practical, technical, and soft skills relevant to fields of geology, paleontology, and 3D virtualization. Educational outputs will include online hosted media in the form of virtual fieldtrips to globally significant geological sites and trails in the Ikara-Flinders Ranges of South Australia, and their associated curricular materials. The virtual fieldtrips will be made with the assistance of a Google Trekker -a backpack mounted with a 360 degree camera- to make accessible this remote and extraordinary ancient landscape. Cambrian small shelly fossil (SSF) assemblages continue to shape our understanding of early metazoan evolution with respect to phylogenetic relationships, biotic innovations (i.e. biomineralization), and the rise of Phanerozoic-style ecosystems. However, to comprehend the biological fidelity of this skeletal record requires a holistic view of the processes controlling fossilization through time and space. The Cambrian successions of South Australia -host to one of the richest SSF assemblages in the world and spanning various depositional gradients- provide a unique setting in which to investigate the link between preservational mode and paleoenvironmental variations. This project will employ a deeply integrated approach combining sedimentological, geochemical, and fossil datasets in tandem with three-dimensional volume analysis and paleoecological analyses, in order to better understand sources of bias that might skew our perceptions of this early fossil record. With a comprehensive understanding of the variables controlling select preservational modes, we can better inform previous and future interpretations of the skeletal record, not just across the Cambrian, but the entire fossil record. As such, the complimentary data afforded by this research aims to 1) compare skeletal constituents represented by different preservational modes and quantify selective bias exerted by common fossil extraction procedures as well as biological factors (morphology, composition, and affinity); 2) analyze the physical and geochemical characteristics of ancient sediments from different depositional systems to reconstruct paleoenvironment, redox conditions, nutrient flux, and sources of replacive minerals; and 3) quantify and contrast faunal composition, preservational modes, and paleoenvironment to assess the reliability and application of SSFs for regional and global dating of contemporaneous rock successions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.