ABSTRACT

Raymond Canyon is an interesting geomorphic phenomenon which provided the data for a sound, detailed morphometric analysis of a fourth order superimposed drainage system. The objective of this study was to compare present and past drainage properties in order to gain insight into the evolutionary history of the canyon and to attempt to document this evolutionary history. This canyon only became adjusted to structure during major tributary development. The essence of this study was to use various drainage basin analytical techniques and apply them to Raymond Canyon Drainage Basin to see if they could be demonstrated, hence, used to document the evolutionary behavior of a superimposed Idaho-Wyoming thrust belt drainage basin.

Aspects of this unusual canyon are: 1) that it is narrow at western entrance and widens progressively to the east, with development of subsequent (strike) drainage, presumably by headward erosion; 2) that its western side contains a stream that cuts indiscriminantly across structure as units and structures are continuous north-south across the canyon; 3) that it is a singularly large and well-developed erosional feature with respect to the rest of the range north and south; 4) that its two main suborder basins exhibit different drainage patterns; and 5) that the Pliocene Sublette Conglomerate in the southern portion suggests a superposition chronology.

The apparent lack of evidence explaining the location and nature of Raymond Canyon suggested additional study. This study reveals data which show that two major geomorphic processes working in conjunction were the determining factors in canyon development. These two processes were stream capture and stream rejuvenation. Also, even though there appears to be no obvious evidence of structural control determining canyon location, structural elements did play an indirect role in canyon evolution.

The data presented in this paper will show that Raymond Canyon is a conclusive illustration of a geomorphic response to Idaho-Wyoming thrust belt compressional tectonics development, as well as Basin and Range extensional tectonics.

Measurements of present and past parameters such as number of streams, mean length of streams, and mean area and perimeter of suborder basins show a consistency through time, independent of basin morphometry, when applied graphically. Hypsometric (area-altitude), long-profile adjustment, and SL (gradient index) analyses reveal conclusive evidence that Raymond Creek is in an equilibrium (mature) stage.