Sediment Inputs to Subduction Zones: Why Lithostratigraphy and Clay Mineralogy Matter
The article “Sediment Inputs to Subduction Zones: Why Lithostratigraphy and Clay Mineralogy Matter” by M. B. Underwood discusses lithostratigraphy architecture in terms of tectonic behavior and material properties. The thesis of the paper is that clay-size particles do affect sediment’s coefficient of permeability and friction. To prove his position the author conducts Seismogenic Zone Experiment as it gives an excellent opportunity to identify the effects of intrinsic strength of friction and affects of gradual increase in pore pressures.
The author provides three paradigms: stratigraphic, geotechnical and hydrogeology paradigms. Stratigraphic paradigm suggests that it is necessary to expect gradual thickening and coarsen upward of subduction-margin successions. Geotechnical paradigm stresses that surrounding wall rocks are significantly stronger than clay-rich fault gauges as their constituent mineralogy and particle size are higher. Finally, hydrogeology paradigm suggests that normal stress and fluid pressure are able to affect the shear strengths of stratigraphic interval making it dependent.
Actually, three-dimensional characterization is crucial for experiment as it is possible to get fuller picture of clay’s effect on friction and permeability. The author says that physical hydrogeology and geotechnical properties of material are influenced by mineral composition, sediment texture, and sediment structure as they working together in sedimentary section. Underwood concludes that subduction inputs are variable in space and time in Costa Rica, Cascadia, Nankai, and Barbados.
The author opposes initial claim that stratigraphic section thickens transforming into hemipelagic mud or sandy turbidities. Mainly, subduction areas are characterized by amounts of compositional heterogeneity if the strike occurs. The article contributes understanding of marine geology as the author provides in-depth analysis of lithostratigraphy architecture and clay mineralogy discussing major influences and affects. The author broadens our knowledge of subduction areas, tectonic structures and a number of researches being conduction in this sphere.