Evolution of the thermal and dehydration state of sediments entering the North Sumatra Subduction Zone
Evolution of the thermal and dehydration state of sediments entering the North Sumatra Subduction Zone
Shallow slip on the plate-boundary fault during the 2004 Mw 9.2 Aceh-Andaman Earthquake, offshore North Sumatra, has been linked to thick incoming sediments on the oceanic plate with advanced diagenetic and sediment property changes at the depths of plate boundary fault development. We couple age control, physical, and thermal property measurements from International Ocean Discovery Program (IODP) drilling with multichannel seismic reflection data to reconstruct the thermal structure and evolution of the incoming sediment column, up to the point of accretion/subduction. Lithospheric thermal rejuvenation around 58 Ma is required to explain anomalously high heat flux at IODP Site U1480, and heat flux within the trench is suppressed by very high sediment accumulation rates during the development of a thick trench wedge. Accumulation of up to ∼4.5 km of thick Nicobar Fan and trench wedge sediments produces temperatures >150°C within the basal sediments where the décollement develops, resulting in total pre-subduction diagenetic dehydration of basal sediments. The smectite-illite transformation within these basal sediments produces sufficient fluid to explain a polarity reversal on a pre-décollement reflector. We suggest that the boundary between basal-pelagic and siliciclastic-fan sediments has trapped fluid over the last ∼1 Myr, as a result of primary lithological properties, diagenetic fluid release, and cementation, controlling décollement formation at this weakened level. Pre-subduction dehydration of large portions of the accreted sediment column strengthens the décollement beneath the prism, extending co-seismic velocity-weakening behavior close to the trench, which may occur at other subduction zones with similar sediment compositions, thicknesses, and/or temperatures.
IODP, Seismic reflection, Subduction, thermal modeling
Stevens, Duncan Eliott
d8a1aedd-186d-47d5-a849-6c39fc9f0a1d
Henstock, Timothy
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Mcneill, Lisa
1fe6a1e0-ca1a-4b6f-8469-309d0f9de0cf
April 2021
Stevens, Duncan Eliott
d8a1aedd-186d-47d5-a849-6c39fc9f0a1d
Henstock, Timothy
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Mcneill, Lisa
1fe6a1e0-ca1a-4b6f-8469-309d0f9de0cf
Stevens, Duncan Eliott, Henstock, Timothy and Mcneill, Lisa
(2021)
Evolution of the thermal and dehydration state of sediments entering the North Sumatra Subduction Zone.
G3: Geochemistry, Geophysics, Geosystems, 22 (4), [e2020GC009306].
(doi:10.1029/2020GC009306).
Abstract
Shallow slip on the plate-boundary fault during the 2004 Mw 9.2 Aceh-Andaman Earthquake, offshore North Sumatra, has been linked to thick incoming sediments on the oceanic plate with advanced diagenetic and sediment property changes at the depths of plate boundary fault development. We couple age control, physical, and thermal property measurements from International Ocean Discovery Program (IODP) drilling with multichannel seismic reflection data to reconstruct the thermal structure and evolution of the incoming sediment column, up to the point of accretion/subduction. Lithospheric thermal rejuvenation around 58 Ma is required to explain anomalously high heat flux at IODP Site U1480, and heat flux within the trench is suppressed by very high sediment accumulation rates during the development of a thick trench wedge. Accumulation of up to ∼4.5 km of thick Nicobar Fan and trench wedge sediments produces temperatures >150°C within the basal sediments where the décollement develops, resulting in total pre-subduction diagenetic dehydration of basal sediments. The smectite-illite transformation within these basal sediments produces sufficient fluid to explain a polarity reversal on a pre-décollement reflector. We suggest that the boundary between basal-pelagic and siliciclastic-fan sediments has trapped fluid over the last ∼1 Myr, as a result of primary lithological properties, diagenetic fluid release, and cementation, controlling décollement formation at this weakened level. Pre-subduction dehydration of large portions of the accreted sediment column strengthens the décollement beneath the prism, extending co-seismic velocity-weakening behavior close to the trench, which may occur at other subduction zones with similar sediment compositions, thicknesses, and/or temperatures.
Text
Stevens_et_al-2021-G-Cubed
- Accepted Manuscript
More information
Accepted/In Press date: 15 March 2021
e-pub ahead of print date: 22 March 2021
Published date: April 2021
Additional Information:
Funding Information:
Funding for this research was provided by the Natural Environmental Research Council (grant numbers NE/P012140/1, NE/P012817/1 and NE/L002531/1). The authors thank the JOIDES Resolution crew, IODP technical team, and science party for their contributions during Expedition 362. In addition, we thank the two anonymous reviewers, associate editor and the editor Whitney Behr for their useful comments, which helped to improve this manuscript.
Publisher Copyright:
© 2021. The Authors.
Keywords:
IODP, Seismic reflection, Subduction, thermal modeling
Identifiers
Local EPrints ID: 448102
URI: http://eprints.soton.ac.uk/id/eprint/448102
ISSN: 1525-2027
PURE UUID: ec86e4d8-90d5-49e8-9215-fbfaf8d6c713
Catalogue record
Date deposited: 01 Apr 2021 15:58
Last modified: 17 Mar 2024 02:52
Export record
Altmetrics
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
