The impact of rapid sediment accumulation on pore pressure development and dehydration reactions during shallow subduction in the Gulf of Alaska

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doi: 10.1002/2016GC006693
Author(s): Meridth, Lanie N.; Screaton, Elizabeth J.; Jaeger, John M.; James, Stephanie R.; Villaseñor, Tania
Author Affiliation(s): Primary:
University of Florida, Department of Geological Sciences, Gainesville, FL, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 18(1), p.189-203. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 58 refs.; illus., incl. 2 tables, sketch map
Summary: In the Gulf of Alaska region, sediment has rapidly accumulated (>1 km/my) in the trench sourced from intensified glaciation in the past ∼1.2 million years. This rapid sediment accumulation increases overburden and should accelerate dehydration of hydrous minerals by insulating the underlying sediment column. These processes have the potential to generate fluid overpressures in the low permeability sediments entering the subduction zone. A 1-D model was developed to simulate dehydration reaction progress and investigate excess pore pressures as sediments approach the trench and are subducted. At the deformation front, simulated temperatures increase by ∼30°C due to the insulating effect of trench sediments. As a result, opal-A begins to react to form quartz while smectite remains mostly unreacted. Loading due to the trench sediments elevates excess pore pressures to ∼30% of lithostatic pressure at the deformation front; however, deformation front excess pore pressures are sensitive to assumptions about the permeability of outer wedge sediments. If the outer wedge sediments are coarse-grained and high-permeability rather than mud-dominated, excess pore pressures are lower but still have an insulating effect. During early subduction, simulated pore pressures continue to rise and reach ∼70% of lithostatic by 60 km landward. The 1-D modeling results suggest that the elevated pore pressures are primarily due to loading and that dehydration reactions are not a significant component of excess pore pressure generation at this margin. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2017
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; 07 Marine Geology and Oceanography; Accretionary wedges; Aleutian Trench; Cenozoic; DSDP Site 178; DSDP Site 180; DSDP Site 182; Deep Sea Drilling Project; Dehydration; East Pacific; Expedition 341; Glaciation; Gulf of Alaska; IODP Site U1417; Integrated Ocean Drilling Program; Leg 18; Marine sedimentation; North Pacific; Northeast Pacific; Ocean floors; Pacific Ocean; Pore pressure; Quaternary; Sedimentation; Sedimentation rates; Subduction; Trenches
Coordinates: N540000 N611500 W1350000 W1630000
Record ID: 2017048090
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union