The Composite Nature of the Provo Level of Lake Bonneville, Great Basin, Western North America

a B B o f J h w w Deposits of a transgressive-phase Lake Bonneville stillstand or scillation are found just below the elevation of the regressivehase Provo shoreline at numerous exposures throughout the onneville basin. Existence of these subProvo shoreline deposits rovides a new explanation for the massive size of Provo deposiional and erosional landforms, which can no longer be explained y a long stillstand at the Provo shoreline. Provo coastal landforms re large because they are superimposed on subProvo landforms. esults also help to clarify divergent interpretations regarding the elative age of the Provo shoreline and the number of times it was ccupied by the water plane. Occupation of approximately the ame level during both the transgressive and the regressive phase f Lake Bonneville may be coincidental, or it may indicate that a edrock sill controlled outflow at subProvo as well as Provo time. ise to the Bonneville level could have occurred after massive lope failure plugged the outlet pass. © 1999 University of Washington.