Hawryszko and Hamilton (ibid., v. 12, p. 623-631, 1964) assigned the Jasper Lake Member from the base of the Turner Valley Formation to the Shunda Formation, implying that the latter was Osage or older. Abnormal thinning of the Shunda Formation in the area was considered a facies change and the Jasper Lake Member, a local development rather than a younger unit. Mountjoy believes an Osage age has not been established for the Jasper Lake Member, which he would keep in the Turner Valley Formation or upper Rundle Group because of its difference in lithology from the Shunda Formation where its inclusion violates the Shunda definition and the Code of Stratigraphic Nomenclature. He thinks the Shunda's age varies throughout the basin and that its thinning is neither unusual nor a facies change. Rundle Group stratigraphy in northern Jasper Park supports his beliefs.