Sadie Fischer HBESc thesis abstract

There have been many studies investigating microbial mat colonies in carbonate environments, yet few have been completed for siliciclastic settings.  This thesis presents research of microbially induced sedimentary structures from the siliciclastic portion of the Paleoproterozoic Gunflint and Rove Formations, Animikie Group, northwestern Ontario.  Four outcrops were chosen for investigation in the Thunder Bay area based on their depositional environments.  The first of the 3 sites was in the Rove Formation, where the physical features resemble a submarine fan environment with turbidity current deposits.  The other two Rove Formation sites were comprised of fine, parallel laminated black shale near its base.  These 3 sites did not show evidence of microbial communities, while the fourth site in the Gunflint Formation at Current River did.  The outcrop is located north of the famous Gunflint stromatolites on the Eastern River bank of Current River.  Multiple microbially induced sedimentary structures (MISS) were located on the bedding surfaces and were recorded by photograph.  These include:  (a) bulges of mat growth due to repeated wetting of the area, (b) preserved mat chips, (c) Kinneyia wrinkle structures, (d) ripple patches, and (e) similar textures on multiple sand layers indicating extracellular polymeric substances (EPS).  Further inspection using a petrographic microscope revealed (f) wavy-crinkly biolamination and (g) redeposited roll-up structures from the rock samples.  None of these examples can be indisputably proven as microbially induced sedimentary structures, yet these features should be considered as indicators of microbial mats in the siliciclastic sediments of the Gunflint Formation.