Cover-beds as relative-dating tools - examples from the western USA

Cover-beds (colluvium that may contain admired loess) are usually not regar ded of use for relative dating. Three examples from the western USA, where intervening soil forming episodes provide a stratigraphic framework of such deposits, demonstrate otherwise. The stratigraphic value of cover-bed and soil sequences was tested on a river terrace chronosequence in southeastern Utah, on ice-wedge casts in south-central Wyoming, and on till and affilia ted outwash in northeastern Nevada. There is indication that Mt. St. Helens -derived cummingtonite can serve as a stratigraphic marker mineral in the a rea. When relative-dating relief by overlying cover-beds, care must be take n of erosion hiatuses and of tectonically induced processes out of phase wi th those driven by climate. Because cover-beds are widespread and cover lar ge areas, similar approaches are encouraged to test their stratigraphic val ue elsewhere.