Interactions between Microorganisms and Clay-Rich Sediments during Early Burial and Diagenesis
Abstract
The purpose of this dissertation was to understand interactions between
microorganisms and fine-grained sediments during the early stages of burial and
diagenesis. Despite the abundance of research on sediment diagenesis, there remain
many overlooked and understudied relationships between microorganisms and
sediments. We investigated interactions between (1) clay minerals and sediment pore
fluids, (2) microorganisms and fine-grained sediments, and (3) microorganisms, clay
transformations, and carbonate precipitation. We employed an integrated program of
numerical modeling as well as experimental and analytical techniques using natural
marine sediments and iron-reducing bacteria to study these interactions. We found that
clay minerals modulate sediment pore fluid pH and carbonate mineral saturation, that the
effectiveness of microorganisms at altering permeability and compression properties is
dependent on burial depth (porosity as a function of vertical effective stress) and the
grain size, pore and pore throat size, and specific surface area of a sediment, and that
microorganisms can induce clay mineral transformations (smectite to illite) and
carbonate precipitation during the early stages of diagenesis. These results are of
importance for carbon and elemental cycling throughout Earth history, fluid flow and
overpressure generation in the subsurface, friction properties on faults, and oil and gas
exploration.
Subject
early diagenesissediment diagenesis
microorganisms
biogeochemistry, clay minerals
pore fluid
permeability
compressibility
smectite-to-illite
fine-grained sediments
mudstones
carbonate diagenesis
Citation
Mills, Nicholas Tanner (2021). Interactions between Microorganisms and Clay-Rich Sediments during Early Burial and Diagenesis. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /196472.