Consolidation Behavior and Pore Structure of Clay and Silt Sized Carbonate Sediment
Gregory Hurd
Jackson School of Geosciences, The University of Texas at Austin
Austin, Texas, United States Of America
[email protected]
Mechanical compaction of carbonate mud has been cited by a number of workers as a primary cause of rotational subsidence, synsedimentary fractures, and unconformities created by differential compaction in carbonate depositional systems. Although a number of studies have utilized porosity-depth curves as a means for quantitatively analyzing compaction in carbonate sediments, many basic questions remain unanswered, including: What is the rate of compaction in carbonate mud? What is the relationship between porosity, permeability, and overburden stress for carbonate mud? What is the Young’s modulus of carbonate mud at depth?
This study aims to answer these questions by producing reconstituted samples of modern carbonate sediment that can be tested in a laboratory. Using resedimentation techniques and pure carbonate mud from Florida Bay, I produced homogenous samples with known stress histories. We have compacted these samples using methods of incremental loading and constant rate of strain as outlined by the American Society for Testing and Materials. Our study demonstrates that carbonate mud may compact up to ~81% of its total volume within the first few thousand meters of burial. We also explore the relationships between porosity, permeability, Young’s modulus, and overburden stress for carbonate mud. Comparing these results to data from identical experiments performed on siliciclastic sediments allows important results. I hypothesize that clay and silt sized carbonate sediments compact at a more rapid rate than siliciclastic muds because carbonate minerals have a lower surface area per mass ratio than clay minerals, and thus can dewater at a more rapid rate.
AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects