GEOACOUSTIC INVESTIGATIONS OF MICROBIALITE PATTERNS AND DISTRIBUTION IN PAVILION LAKE, BRITISH COLUMBIA

Stromatolitic fossils date to 3500 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 stromatolite morphologies are abundant in strata deposited during the last billion years of the Proterozoic (Awramik, 1984). Advances in lake bottom mapping have revealed that modern microbialites, much like the ancient stromatolites, thrive in freshwater lake environments. Previously collected data shows that a diverse community of living stromatolites are present within Pavilion Lake (Laval et al., 2000, Lim et al., 2009). This presentation builds on recently collected high-resolution geoacoustic data to perform detailed morphological analysis of microbialite patterns in modern settings as evidenced from Pavilion Lake.

Autonomous Underwater Vehicles (AUVs) were used as an exploration platform to conduct high resolution sonar surveys of the lake bottom. Multiple software packages (e.g. MatLab, Fledermaus, ArcGIS, SonarWIZ) were utilized to process the resultant data. A classification scheme, based on observed slope and rugosity values, was applied to the lake floor. Analysis of lake bottom data collected with a phase measuring bathymetric sonar in terms of slope and rugosity, resulted in a map of microbialite morphological trends. The bathymetric data was compiled to create a base map of the lake floor and then gridded at a very high resolution, 25cm. The bathymetry data allows for analysis of bed forms within Pavilion Lake, as well as any erosional episodes that may affect the growth of microbialites. Backscatter data was also collected and processed. After processing the data it was draped over the bathymetric map. The backscatter data shows the strength of the sonar return, and in turn the density of the base material. The combination of backscatter and bathymetry allows for a further understanding of bedforms and microbialite growth patterns