Self-Organization in Carbonate Diagenesis

Budd, David A.¹, Anthony J. Park² (1) University of Colorado, Boulder, CO (2) Sienna Geodynamics & Consulting Inc, Boston, MA

Self-organization creates pattern from interactions between the components of a dynamic system. The patterns are produced without external influences or a pre-existing template. Self-organizing diagenetic phenomena posited to date include oscillatory zoning in crystals, chemical banding, karst conduits, stylolites, zebra textures in burial dolomites, limestone-marl alterations, and various attributes of massive dolostones.

Self-organization requires disequilibrium and nonlinear feedbacks. The nonlinearity means a range of possible stable configurations. Changing boundary conditions trigger the system's evolution to a specific pattern. In carbonate diagenesis, changes in physiochemical regime change boundary conditions and create disequilibrium. Nonlinear feedbacks arise between fluid flow, changing petrophysics, and the system's evolving chemistry. The question is not, are there self-organizing phenomena in carbonate diagenesis, but how do we recognize them and determine their origin?

The simplest way to identify self-organizing phenomena is to detect patterns in diagenetic products. This is straightforward at handsample or smaller scales. At larger scales, patterns can only be detected with regularly spaced samples, and this has only been done in a few dolostones. We will only know what self-organizing phenomena exist if we first adjust our sampling strategies and systematically look for it in the attributes of carbonate rocks.

Recognizing patterns, however, will not explain how self-organizing diagenetic systems function. Due to the complexity of the systems and the range of possible outcomes, understanding self-organizational mechanisms requires numerical simulations. Our coupled reaction-transport and fabric-evolution model of dolomitization illustrates how self-organized patterns develop with fluid type, flow rates, and rock fabric influencing the patterns.