the oldest member (early pennsylvanian), the watahomigi formation is from sedimentary basins. it is composed of red mudstone, sandstone, and tan limestone. as ocean levels rose, basins filled, and the manachka formation was laid down (especially in the grand canyon). continentally aeolian sand became more widespread; the coeval weber sandstone was deposited in northeast utah (dinosaur national monument region, northeast of the uncompahgre uplift).