There is no apparent reason why microbial mats should not also have colonized mud bottoms of other Precambrian basins, as well as those of Phanerozoic basins under certain circumstances.
Photos are low resolution for faster loading.
Click on the image to get a larger, high resolution picture. The lighter layers may show grading with silt laminae and lenses at the base and clays at the top. The irregular carbonaceous laminae are considered internal laminae of microbial mats. Scale bar is 0.5 mm long . Flakes are contorted and contain more silt than the surrounding shale matrix.