Slow Rates of Subduction Erosion and coastal underplating along the Andean Margin of Chile and Peru

Peter Dominic Clift, Adrian John Hartley

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

Marine seismic and drilling data from the Andean margin of Peru and northern Chile show trench retreat and tectonic erosion since at least 20 Ma. However, the onshore coastal zone has undergone modest regional uplift since ca. 2 Ma. This argues against subduction erosion of the margin by steady-state retreat, such as recognized in Tonga or South Sandwich. Instead we identify a new style of slow tectonic erosion. Uplifted forearc sediments indicate underplating of subducted material beneath the base of the coastal forearc, synchronous with tectonic erosion under the trenchward part of the forearc. These observations require slow rates of forearc crust subduction in the region during this time period, averaging no more than 13 km(3)/m.y./km since 20 Ma as the forearc wedge taper increased. Isostatic volume estimates suggest that as much as 85% of subducted material was underplated under the forearc since 330 ka and does not contribute to crustal growth under the Andes. The switch in tectonic style parallels that in the southern Andes, but cannot be triggered by increased sediment flux to the trench, as proposed for that area.

Original languageEnglish
Pages (from-to)503-506
Number of pages4
JournalGeology
Volume35
Issue number6
DOIs
Publication statusPublished - Jun 2007

Keywords

  • subduction
  • tectonics
  • subsidence
  • sedimentation
  • Andes
  • tectonic erosion
  • southern central Andes
  • northern Chile
  • fore-arc
  • Costa-Rica
  • convergent margins
  • continental-crust
  • Pacific margin
  • deformation
  • sea

Cite this

Slow Rates of Subduction Erosion and coastal underplating along the Andean Margin of Chile and Peru. / Clift, Peter Dominic; Hartley, Adrian John.

In: Geology, Vol. 35, No. 6, 06.2007, p. 503-506.

Research output: Contribution to journalArticle

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N2 - Marine seismic and drilling data from the Andean margin of Peru and northern Chile show trench retreat and tectonic erosion since at least 20 Ma. However, the onshore coastal zone has undergone modest regional uplift since ca. 2 Ma. This argues against subduction erosion of the margin by steady-state retreat, such as recognized in Tonga or South Sandwich. Instead we identify a new style of slow tectonic erosion. Uplifted forearc sediments indicate underplating of subducted material beneath the base of the coastal forearc, synchronous with tectonic erosion under the trenchward part of the forearc. These observations require slow rates of forearc crust subduction in the region during this time period, averaging no more than 13 km(3)/m.y./km since 20 Ma as the forearc wedge taper increased. Isostatic volume estimates suggest that as much as 85% of subducted material was underplated under the forearc since 330 ka and does not contribute to crustal growth under the Andes. The switch in tectonic style parallels that in the southern Andes, but cannot be triggered by increased sediment flux to the trench, as proposed for that area.

AB - Marine seismic and drilling data from the Andean margin of Peru and northern Chile show trench retreat and tectonic erosion since at least 20 Ma. However, the onshore coastal zone has undergone modest regional uplift since ca. 2 Ma. This argues against subduction erosion of the margin by steady-state retreat, such as recognized in Tonga or South Sandwich. Instead we identify a new style of slow tectonic erosion. Uplifted forearc sediments indicate underplating of subducted material beneath the base of the coastal forearc, synchronous with tectonic erosion under the trenchward part of the forearc. These observations require slow rates of forearc crust subduction in the region during this time period, averaging no more than 13 km(3)/m.y./km since 20 Ma as the forearc wedge taper increased. Isostatic volume estimates suggest that as much as 85% of subducted material was underplated under the forearc since 330 ka and does not contribute to crustal growth under the Andes. The switch in tectonic style parallels that in the southern Andes, but cannot be triggered by increased sediment flux to the trench, as proposed for that area.

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KW - subsidence

KW - sedimentation

KW - Andes

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KW - northern Chile

KW - fore-arc

KW - Costa-Rica

KW - convergent margins

KW - continental-crust

KW - Pacific margin

KW - deformation

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