Spatial variability and control on the distribution of microbialites: case study from Pavilion Lake, British Columbia, Canada
Date
2011
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Stromatolitic fossils date to 3500 million years ago (Ma) (Awramik et al.,
1983; Lowe, 1980; Walter et al., 1980), and comprise the most abundant fossil group from 2500 to 570 Ma ago. A variety of fossil stromatolite morphologies are abundant in strata deposited during the last billion years of the Proterozoic (Awramik, 1984). With advances in lake bottom mapping it has been observed that modern microbialites, which are much like the ancient stromatolites, can thrive in freshwater lake environments. Previously collected data show that a diverse community of living stromatolites are present within Pavilion Lake in British Columbia, Canada (Laval et al., 2000, Lim et al., 2009). This project builds orecently collected high-resolution geoacoustic data to perform detailed morphological analysis of microbialite patterns in modern settings as evidenced from PavilionLake. Using Autonomous Underwater Vehicles (AUVs) as exploration platforms to conduct surveys of the lake bottom, very high-resolution sonar data has been collected. By analyzing this bathymetric and backscatter sonar of the lake bottom, with respect to slope and rugosity, it is possible to map the morphological trends of the microbialites present in Pavilion Lake. DeepWorker (DW) submersibles and SCUBA divers were used to ground truth the sonar images to ensure the sonar data offered a true representation of the microbialites on the lake bottom. The sonar data collected offers nearly complete coverage of the lake bottom. The growth pattern morphology characteristics have been compiled into a full-scale map of the lake bottom. This map allows for a better understanding of the morphological characteristics of the microbialite macro-patterns found in Pavilion Lake and will aid in the interpretation of patterns in both other modern lakes and in the ancient rock record. Using multiple software packages the sonar data has been analyzed and the slope and rugosity calculated and a multivariate principal components analysis classification was applied to the sonar backscatter to generate acoustic seabed types using a commercial automated classification system. The aim of this thesis was to create a quantified classification of the largescale morphological characteristics (1-100 m) of the microbialites of Pavilion Lake. Results indicate that the microbialite features grow within specific slope and rugosity thresholds.