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

Abstract

Deposits of a transgressive-phase Lake Bonneville stillstand or oscillation are found just below the elevation of the regressive-phase Provo shoreline at numerous exposures throughout the Bonneville basin. Existence of these subProvo shoreline deposits provides a new explanation for the massive size of Provo depositional and erosional landforms, which can no longer be explained by a long stillstand at the Provo shoreline. Provo coastal landforms are large because they are superimposed on subProvo landforms. Results also help to clarify divergent interpretations regarding the relative age of the Provo shoreline and the number of times it was occupied by the water plane. Occupation of approximately the same level during both the transgressive and the regressive phase of Lake Bonneville may be coincidental, or it may indicate that a bedrock sill controlled outflow at subProvo as well as Provo time. Rise to the Bonneville level could have occurred after massive slope failure plugged the outlet pass.

Chronology of latest Pleistocene lake‐level fluctuations in the pluvial Lake Chewaucan basin, Oregon, USA

“…1310 m shoreline. This scenario is similar, though not strictly analogous, to the stabilising influence of the bedrock sill at Red Rock Pass, which may have resulted in reoccupation of the Provo shoreline of Lake Bonneville during the latest deep-lake cycle (Sack, 1999).…”

Transgressive stratigraphic record and possible oscillations of late Pleistocene Lake Bonneville, Northern Hogup Mountains, Utah, U.S.A.

“…He termed these shorelines "Intermediate shore lines," which this paper refers to as "Intermediate shorelines." Even though other researchers mention the existence of these less prominent features (Scott et al, 1983;Scott, 1988;Burr and Currey, 1992;Oviatt et al, 1994;Sack, 1999) and periodically included them in regional geologic maps (Miller and Oviatt, 1994;Miller and McCarthy, 2002), the literature does not describe their relevance in much detail. The Intermediate shorelines are important because they record smaller-scale lake level changes or oscillations superimposed on the broader transgressive phase (rise) of the lake and are related to the lake's response to regional climatic drivers during the Last Glacial Maximum.…”

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“…All of these factors, plus the possibility that some shorelines assigned to the Provo level formed during pauses in the initial Bonneville transgression (Sack, 1999), make it critical to correctly identify shorelines and correlate them laterally (Fig. 3).…”