Why is there no Coastal Cordillera at the Arica Bend (Western Central Andes)?

Madella, Andrea; Delunel, Romain; Audin, Laurence; Schlunegger, Fritz (2016). Why is there no Coastal Cordillera at the Arica Bend (Western Central Andes)? Basin research, 30, pp. 248-268. Blackwell Science 10.1111/bre.12218

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The architecture of the Western Andes is remarkably constant between southern Peru and northern Chile. An exception, however, is present near Arica at 18°S, where the Andes change their strike direction by ca. 50° and the Coastal Cordillera is absent over an along strike width of 50 km. Although this feature has been mentioned in several previous studies, no effort has been made yet to describe and explain this peculiar morphology of the Western Central Andean forearc. Here, we propose a large-scale model to explain the Myr-long low uplift rate of the Arica Bend concerning seismic coupling and continental wedge-top basin evolution. New geomorphic and sedimentologic data are integrated with seismicity and structural data from the literature to interpret the post-Oligocene pattern of uplift, erosion, and sediment transport to the trench. Results show that the Arica Bend has been marked by exceptionally low coastal uplift rates over post-Oligocene timescales. In addition, this uplift anomaly at the Arica Bend correlates with relatively high sediment discharge to the corresponding trench segment since late Oligocene time. We interpret that before 25 Ma, the forming seaward concavity of the subduction zone induced trench-parallel extension at the curvature apex of the overriding forearc. The subsequent low uplift rate would have then triggered a feedback mechanism, where the interplay between relatively-low interplate friction, low coastal uplift and relatively-high sediment discharge favored Myr-long relative subsidence at the Arica Bend, in contrast to Myr-long uplift of the Coastal Cordillera north and south of it.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Exogenous Geology

UniBE Contributor:

Madella, Andrea; Delunel, Romain and Schlunegger, Fritz

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0950-091X

Publisher:

Blackwell Science

Funders:

[4] Swiss National Science Foundation

Language:

English

Submitter:

Andrea Madella

Date Deposited:

01 Sep 2016 15:15

Last Modified:

17 Jan 2018 01:30

Publisher DOI:

10.1111/bre.12218

Uncontrolled Keywords:

Northern Chile, Coastal Cordillera, Arica Bend, Western Andes Forearc, uplift plate interface

BORIS DOI:

10.7892/boris.86302

URI:

https://boris.unibe.ch/id/eprint/86302

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