Estimation of length distributions from outcrop datasets – application to the Upper Permian Cutler Formation, Utah

Many outcrops have partially exposed sedimentary bodies that are cut by one or both edges of the outcrop. These so-called ‘partials’ contain important information on the size distribution of the bodies under study, and should be accounted for in a proper statistical sense. A new method was proposed elsewhere, based on the theory of conditional probability. The method estimates the expected complete length along outcrop for each ‘partial’, making use of the length distribution of completely exposed bodies in the same outcrop. The estimated lengths are then added to the set of observed complete lengths to yield a new, refined length distribution. This paper illustrates the practical application of the method on an outcrop dataset from the Permian Cutler Formation in southeastern Utah that may serve as an analogue for mixed fluvial–aeolian reservoirs. Solutions are proposed for some practical problems that can be encountered when dealing with outcrop data. The estimated length distributions show that ‘partials’ add considerable information about the larger length classes.