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.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California