STATISTICAL-ANALYSIS OF BED-THICKNESS PATTERNS IN A TURBIDITE SECTIONFROM THE GREAT VALLEY SEQUENCE, CACHE CREEK, NORTHERN CALIFORNIA

This paper explores the use of a Monte Carlo adaptation of runs analys is to analyze turbidite sequences for the presence of asymmetric bed-t hickness cycles, Waldron's test can be used to identify sequences that are dominated by either upward-thickening or upward-thinning cycles, but not both, Our adaptation of runs analysis provides a robust techni que that can indicate the presence of local thickness trends that are different from those expected in random sequences, and can be used to evaluate the relative importance of upward-thickening and upward thinn ing cycles, As a case study, 236 m of the Upper Cretaceous Sites Forma tion in the Great Valley Group were measured and described in detail a long Cache Creek in northern California, This section had been previou sly interpreted as a succession of prograding submarine-fan lobe depos its marked by asymmetric upward-thickening cycles, Application of Wald ron's test indicates that the section is not dominated by upward-thick ening cycles, as previously suggested, Monte Carlo runs analysis demon strates that small-scale upward thinning cycles are as common as upwar d-thickening cycles. The simple progradation of submarine fan lobes do es not adequately explain the thickness patterns seen in the section. Application of Monte Carlo runs analysis to other turbidite sections w ould be useful for quantitative identification and comparison of turbi dite bed-thickness cycles, which should lead to development of better turbidite facies models.