S. B. Gaswirth
Department of Geological Sciences, University of Colorado, Boulder, CO
Comparisons of Neogene and Paleozoic dolomites suggest that dolomites in general undergo a maturation process as they are exposed to diagenetic alteration during both near-surface and burial processes. They evolve from a porous, friable initial dolomite (“immature”) to a hard and brittle, nonporous and impermeable dolomite (“mature”). Most studies of dolomite, and hence dolomite maturation, focus on either the Neogene or Mesozoic/Paleozoic end members of the maturation process. A more thorough understanding of the maturation process(es) is possible from the study of Paleogene dolomites from west-central Florida that are intermediate between the younger and older end members.
Mixing-zone diagenesis has a potential role in dolomite maturation, in that typical mixing-zone dolomites have a high proportion of dolomite cement added to preexisting dolomite crystals. This leads to the question of how might an initial stage of maturation in a mixing-zone affect the preexisting, replacive dolomites? Do they become dramatically less porous and permeable and is their potential for fracturing enhanced? If so, how much cement/recrystallization is needed and does that require multiple overprints by temporally oscillating mixing zones?
This study will have significant implications with respect to controls of dolomite maturation and the diagenetic importance of a regional mixing zone system. Results from this study will impact the understanding of dolomite maturation from Neogene dolomites in modern settings to multigenerational dolomites in Mesozoic and Paleozoic rocks. This research will also contribute to the debate on the origin and maturation of dolomite cements in mixing zone environments.
AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid