Journal of Sedimentary Research, Section
A: Sedimentary Petrology and Processes
Vol. 66 (1996)No.
5. (September), Pages 900-908
Statistical Analysis of Bed-Thickness Patterns in a Turbidite Section from
the Great Valley Sequence, Cache Creek, Northern California
Christopher J. Murray (1), Donald R. Lowe, Stephan A.
Graham, Paul A. Martinez (2), Jianjun Zeng, Alan R. Carroll (3), Ronadh
Cox (4), Marc Hendrix (5), Christoph Heubeck (6), Donald Miller, Ian W.
Moxon (7), Edward Sobel (8), Johannes Wendebourg (9), Thomas Williams
ABSTRACT
This paper explores the use of a Monte Carlo adaptation of runs analysis
to analyze turbidite sequences for the presence of asymmetric bed-thickness
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 technique 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-thinning cycles. As a case study, 236 m
of the Upper Cretaceous Sites Formation in the Great Valley Group were
measured and described in detail along Cache Creek in northern California.
This section had been previously interpreted as a s ccession of prograding
submarine-fan-lobe deposits marked by asymmetric upward-thickening cycles.
Application of Waldron's test indicates that the section is not dominated
by upward-thickening cycles, as previously suggested. Monte Carlo runs
analysis demonstrates that small-scale upward-thinning cycles are as common
as upward-thickening cycles. The simple progradation of submarine fan lobes
does not adequately explain the thickness patterns seen in the section.
Application of Monte Carlo runs analysis to other turbidite sections would
be useful for quantitative identification and comparison of turbidite bed-thickness
cycles, which should lead to development of better turbidite facies models.
