Deformation And Fluidization During Early Diagenesis PDF Download

Gas and fluid vents are being observed with increasing frequency in a variety of depositional settings in the modern day deep-sea. In some cases, these sedimentary features are a result of the destabilization of gas clathrate hydrates below the sediment water interface. However, documented evidence of sedimentary structures related to these processes in the ancient rock record is limited. This study finds evidence for fluidized sediment injection in a succession of fine-grained sedimentary rocks that outcrops in the Basin and Range Province of the south-western United States. These rocks are interpreted to have been deposited in a fault controlled embayment, or half-graben, that formed on the continental shelf of the paleocontinent Laurentia. In this embayment, event deposits comprising sediment gravity flows and carbonate biosomes punctuate thinly bedded muddy to fine-grained sediments interpreted to have been deposited by suspension settling and traction. Unique to the biosomes are features that indicate syn-depositional deformation triggered by seismic activity. Seismic activity is also responsible for increasing pore-pressure of the sediments constrained by the dense, micritic biosomes resulting in fluid injection from sediments below the sediment-water interface. Petrographic and geochemical analyses of these preserved fluidization structures indicates that these fluids may have contained liquid or gaseous carbon dioxide. While these features indicate that fluidized sediment injection was an important process in the early diagenetic history of these sediments, clear evidence for the presence of gas clathrate hydrates has not been found.