Abstract

Mississippian dolowackestones contain periodic oscillations in the lateral distribution of trace-element concentrations, porosity, and permeability. Random variations at ≤30 cm spacing account for 50%–70% of the total variability. The remainder of the variability occurs in short- and long-range oscillatory patterns with periods of 1.2–7.6 m, which can only be resolved by high-resolution sampling of an ∼150 m lateral transect. Possible origins for these patterns are: (1) inheritance from the depositional precursor, (2) formation by self-organizing processes during dolomitization, or (3) overprinting by late diagenesis. These oscillatory patterns have up to now been unrecognized, and addressing their origin and meaning(s) represents a new approach to the study of dolomites. Understanding the lateral distribution of petrophysical properties can also improve models of fluid flow in dolomite petroleum reservoirs and contaminant transport between matrix and conduits in dolomite aquifers. Further, if 30%–50% of the variability in a geochemical attribute in any bed is due to lateral periodicity, one must ask if that variability is too great to assume a spot sample will be a suitable proxy for ancient geologic processes and conditions.

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