Late Miocene increase in precipitation in the Western Cordillera of the Andes between 18–19°S latitudes inferred from shifts in sedimentation patterns

Schlunegger, Fritz; Norton, Kevin P.; Delunel, Romain; Ehlers, Todd A.; Madella, Andrea (2017). Late Miocene increase in precipitation in the Western Cordillera of the Andes between 18–19°S latitudes inferred from shifts in sedimentation patterns. Earth and planetary science letters, 462, pp. 157-168. Elsevier 10.1016/j.epsl.2017.01.002

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Modern climate in the Andes is characterized by strong N–S decreasing trends in precipitation rates. Here we use stratigraphic records to show that this pattern has been established since as early as 12–11 Ma, at least on the western Andean margin of Northern Chile. The stratigraphic architecture on the western Andean margin documents a transition between 19°–20°S latitude where matrix-supported debris flow deposits shift to fluvial conglomerates between 12–11 Ma. The deposition of fluvial sediments has been maintained to the present north of 19°–20°S, while the occurrence of post 11 Ma aeolian sand, matrix-supported breccias with conglomerate interbeds south of these latitudes implies ongoing sedimentation with less water and thus under drier conditions. We relate these changes to the tectonic development of the Andes. Existing palaeoclimate models suggest that an elevated plateau deflects the Andean jet towards the south, thereby focusing moisture from the equatorial Atlantic to the northeastern flanks of the Altiplano. In addition, the formation of the eastern Andean foothills most likely intercepted moisture transport, and shifted it farther to the east, thereby keeping the western Andean margin dry south of 19°–20°S latitudes. The sedimentological data support a strong linkage between orographic precipitation and stratigraphy whereby central Andean deformation controls the distribution of available moisture on the western flank through a combination of orographic precipitation and deflection of air masses.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Schlunegger, Fritz; Delunel, Romain and Madella, Andrea

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0012-821X

Publisher:

Elsevier

Language:

English

Submitter:

Fritz Schlunegger

Date Deposited:

30 Jan 2017 17:05

Last Modified:

16 Feb 2017 11:50

Publisher DOI:

10.1016/j.epsl.2017.01.002

BORIS DOI:

10.7892/boris.94207

URI:

https://boris.unibe.ch/id/eprint/94207

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