Markov chain analysis is a simple, powerful, mathematical tool for testing the presence, absence, and length of "memory" in a sequence of events. Use of this method on the Pennsylvanian carbonates of southern Nevada revealed the presence of a "memory" (X² = 32.55 with 15 df) in the thick basinal interval of the Bird Spring Group of the Arrow Canyon Mountains and a relative lack of memory (X² = 20.5 with 15 df) in the thinner, age-equivalent, shelf deposits of the Callville Limestone on Frenchman Mountain.

Covered intervals have little effect in situations

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where the number of intervals is less than 20% of the total number of identified units. Best results are obtained if coincident layers of identical lithology are treated as a unit facies rather than as multistory facies. The effect of varied identification of lithologies is critical. For example, grouping clay and shale gives markedly different results from cases in which they are distinguished. It can be concluded that (1) Markov tests support current beliefs in that they indicate relative lack of memory in shelf sediments indicating many breaks in sedimentation, and (2) consistent evaluation of facies is critical, as different labels for the same lithology cause large-scale variation in numerical results.

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