Computer models of carbonate platform cycles driven by subsidence and eustasy

Abstract

Six computer simulations of cycles developed on carbonate platforms were generated using MAPS, a BASIC program. Four simulations employed a flat platform and sinusoidal sea-level oscillations with heights ranging from 0.02 to 20 m, but a constant 25 ka period superimposed over a constant relative sea-level rise of 0.05 m/ka. The lower height oscillations might reasonably model variable subsidence rates, whereas the higher oscillations model glacioeustatic sea-level changes. Metre-thick cycles were generated in all cases. Two simulations involved variations in periods of sinusoidal sea-level variations and subsidence rates on a tilting platform. The thicknesses of cycles generated are a function of both period of sea-level oscillation and subsidence rate. In geologic applications, either the period of sea-level oscillations or the subsidence rate needs to be known to determine the other. We suggest that two end-member models need to be considered for interpreting carbonate platform cycles: (1) constant subsidence with variable sea level; (2) constant sea level with variable subsidence. Combinations of these two end members are likely.