Regressive Stromatolite Reefs and Associated Facies, Middle Goulburn Group (Lower Proterozoic), in Kilohigok Basin, N.W.T.: An Example of Environmental Control of Stromatolite Form

Abstract

ABSTRACT The Goulburn Group is a thick succession of intracratonic sedimentary rocks deposited within the lower Proterozoic Kilohigok Basin, northwestern Canadian Shield, which have been correlated with strata of the Coronation Geosyncline and the Athapuscow aulacogen. The middle part of the Goulburn Group is comprised of mudstone, carbonate and stromatolitic carbonate rocks and is classified as the 'carbonate-mudstone stratigraphic interval' of the Kilohigok Basin. This interval of sedimentation can be subdivided into early and late stages. The late stage consists of a vertical succession of facies representing: basinal mudstone-dominated and carbonate-dominated environments, a shallow submarine shelf with clastic carbonate and thick mudstones, a complex stromatolite reef and associated stromatolite facies and intertidal-supratidal mudstone. These facies represent a diachronous sequence of once laterally juxtaposed environments which is interpreted to represent a major regression that affected the entire Kilohigok Basin. Stromatolite forms characterize different stratigraphic assemblages that correspond with changes in environmental conditions. Reconstruction of the lateral distribution of a now vertical succession of stromatolitic carbonates shows a basinward to landward pattern of: fore-reef clastics with subtidal stromatolite mounds, reef tract with large subtidal mounds and channeled columns, and a quiet-water back-reef with stromatolite biscuits. Stromatolite elongations are interpreted to define paleo-reef-tract trends.