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Seamount chain-subduction zone interactions; implications for accretionary and erosive subduction zone behavior

Alexander P. Clarke, Paola Vannucchi and Jason Morgan
Seamount chain-subduction zone interactions; implications for accretionary and erosive subduction zone behavior
Geology (Boulder) (April 2018) 46 (4): 367-370


Sediment volume at the trench and topographic highs on the incoming plate are two of the main factors controlling whether a forearc will undergo subduction erosion or accretion. On oceanic plates, topographic highs such as large seamount complexes are commonly associated with significant volumes of flanking volcaniclastic sediments in the form of >100-km-wide debris aprons, with the largest deposits found in flexural moat basins. We propose that subduction of these sediment accumulations promotes localized frontal accretion, even in otherwise non-accretionary margins. The Osa melange in southwestern Costa Rica is a field example that provides new insights into the nature and occurrence of this interaction. The southwestern margin of Central America is punctuated by accreted Late Cretaceous-middle Eocene seamounts that formed at the Galapagos hotspot and accreted throughout the late Miocene. In contrast to most accreted seamounts along this margin, which retained their overall structure, the Osa melange is a chaotic mixture of seamount lithologies. It consists of basalt, chert, and carbonate blocks in a fine-grained pelitic matrix composed predominantly of feldspar and pyroxene grains with rare quartz. This lithology is consistent with sediment from a seamount chain's debris apron, such as the Hawaiian moat sampled during Ocean Drilling Program (ODP) Leg 136 and the Canary Islands moat sampled by ODP Leg 157. Subduction of seamounts and their debris aprons promotes concurrent accretion and erosion over short distances along the trench. This introduces heterogeneity into the subduction channel, with implications for deformation within the subduction zone plate interface.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 46
Serial Issue: 4
Title: Seamount chain-subduction zone interactions; implications for accretionary and erosive subduction zone behavior
Affiliation: Royal Holloway-University of London, Department of Earth Science, Egham, United Kingdom
Pages: 367-370
Published: 201804
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 30
Accession Number: 2018-043948
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2018109
Illustration Description: illus. incl. geol. sketch maps
N00°00'00" - N09°00'00", W92°30'00" - W83°00'00"
N08°00'00" - N11°15'00", W86°00'00" - W82°30'00"
S01°30'00" - N01°00'00", W92°00'00" - W89°00'00"
N19°00'00" - N28°30'00", W179°00'00" - W155°00'00"
N19°20'10" - N19°20'42", W159°05'44" - W159°05'19"
N27°19'33" - N32°01'54", W25°36'00" - W15°08'41"
N00°00'00" - N75°00'00", W80°00'00" - E20°00'00"
Secondary Affiliation: University of Florence, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 2018
Program Name: ODPOcean Drilling Program
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