Abstract: Evidence for Solution Compaction in Lime Grainstones
A detailed petrographic study has shown the effects of solution compaction on two oolitic grainstones in the Wolfcampian Laborcita Formation of the Sacramento Mountains, New Mexico. Solution compaction (a term first used by R. J. Dunham) is the process of early compaction of a lime grainstone resulting from solution by meteoric water at grain contacts with little or no effect of overburden pressure. The resultant grainstone fabric is characterized by overpacking of grains with sutured grain contacts in extreme cases. Although the effects of solution compaction are widespread in the geologic record, very little has been written concerning the process.
The two oolitic grainstones were deposited at the top of regressive cycles and were exposed to subaerial diagenesis soon after deposition. The grainstones demonstrate an increased packing density in a landward direction as well as upward within each unit. This pattern supports solution compaction as the cause of overcompaction, as the effects of pressure solution would be relatively uniform throughout each unit. The permeability of the sediment also controlled the degree of solution compaction on a microscale. The grains immediately surrounding keystone vugs (areas of increased permeability) exhibit increased packing density, whereas patches cemented by early syntaxial overgrowth cement on echinoderm fragments (areas of decreased permeability) show decreased effects of solution compaction.
Solution compaction is significant in three ways. (1) It is a porosity-destroying process. (2) It indicates early subaerial diagenesis. (3) The patterns of packing density can be used in reconstructing paleotopographic relations.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC