Algal stromatolites: use in stratigraphic correlation and paleocurrent determination.

Algal stromatolites are used for detailed rock-stratigraphic correlation for a distance of 160 kilometers in the Pethei Formation, of Aphebian (Precambrian) age, in the Northwest Territories, Canada. Laterally linked stromatolites are initiated by the draping of successive laminations over intraclasts or other irregularities in the bedding surface. Stromatolite shapes and orientations are related to paleocurrent direction determined from associated sedimentary structures. Thus stromatolite geometry is at least in part environmentally controlled.