CARBONATE CYCLE STACKING PATTERNS AND HIERARCHIES OF ORBITALLY FORCEDEUSTATIC SEALEVEL CHANGE

Ordered stacking of meter-scale upward-shallowing cycles, manifested a s repeated thickness hierarchies within cratonic carbonate sequences, has been considered primary evidence for causal relations between orbi tally forced climate change and eustatic sealevel variation. Explicit in this argument is the assumption that each individual cycle represen ts a single sealevel rise. Sensitivity testing of one-dimensional forw ard models incorporating a depth threshold of carbonate accumulation i ndicates that multiple upward-shallowing cycles may originate during a ny single rise in sealevel. Variation in resultant cycle stacking patt ern is sensitive to changes in sealevel amplitude, sedimentation rate, and subsidence rate, with highest stacking ratios (ratio of number of cyclic units to number of eustatic periods) produced by low sealevel amplitudes and high sedimentation and subsidence rates. These relation s indicate that direct correlation between multiple-frequency eustatic sealevel variations and meter-scale cycle stacking hierarchies is unw arranted. Thus, prevalent interpretations regarding the stacking recor d of orbital forcing in ancient carbonate rock sequences should be ree valuated.