Pleistocene landscape entrenchment: A geomorphological mountain to foreland field case, the Las Tunas system, Argentina

E. Pepin, S. Carretier, G. Hérail, V. Regard, R. Charrier, M. Farías, V. García, L. Giambiagi

Resultado de la investigación: Article

14 Citas (Scopus)

Resumen

The study of the Las Tunas River incisions, located in the eastern Andean foreland front (33{ring operator}20' S in Argentina), provides new clues for the interpretation of deep piedmont entrenchments. Both the Las Tunas mountain catchment and its piedmont are strongly entrenched with maximal incision of over 100 m at the mountain front. Three main terrace levels are well exposed and are labelled T1, T2 and T3 from the youngest to the oldest. We combined geological and geomorphological field observations, kinematic GPS data, satellite data and aerial photos with geochronological 40Ar/39Ar and 10Be analysis to provide a detailed description of terrace organization and a discussion of the evolution of the Las Tunas landscape. The surprisingly constant 10Be concentrations in surface layers as deep as 1.5 m show that gently dipping alluvial surfaces can be continuously and deeply mixed. Our data show a first period of deposition (Mesones Fm) before 0.85 Myr (minimum T3 age), followed by deep erosion and a second sedimentation period (Las Tunas Fm) that includes a ca. 0.6 Myr ash deposit. T2 and T1 are inset in the Las Tunas Fm and were abandoned ca. 15-20 kyr ago. The similar ages for T2 and T1 show that post-20 kyr entrenchment occurred very rapidly. Despite Quaternary deformation in the Las Tunas piedmont, terrace entrenchment is best explained by paleo-climatic changes. The terrace organization reveals that the erosion-sedimentation phases affected the entire system from the piedmont toe to 10 km upstream of the mountain front. Finally, contrary to the neighbouring more deeply incised Diamante River system, where late Quaternary piedmont uplift is more likely to have been a factor causing incision, the more stable Las Tunas system provides an incomplete geomorphological record of Pleistocene and Holocene climate variations. We suggest that climate variations are better recorded in uplifting piedmonts than in stable ones, where the magnitude of incision and sedimentation and the fact that they occur repeatedly at the same elevation can erase a large part of the record.

Idioma originalEnglish
Páginas (desde-hasta)613-637
Número de páginas25
PublicaciónBasin Research
Volumen25
N.º6
DOI
EstadoPublished - dic 2013

Huella dactilar

piedmont
terrace
Pleistocene
mountain
climate variation
sedimentation
erosion
river system
satellite data
surface layer
ash
GPS
kinematics
uplift
Holocene
catchment
climate change
river

ASJC Scopus subject areas

  • Geology

Citar esto

Pepin, E. ; Carretier, S. ; Hérail, G. ; Regard, V. ; Charrier, R. ; Farías, M. ; García, V. ; Giambiagi, L. / Pleistocene landscape entrenchment : A geomorphological mountain to foreland field case, the Las Tunas system, Argentina. En: Basin Research. 2013 ; Vol. 25, N.º 6. pp. 613-637.
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abstract = "The study of the Las Tunas River incisions, located in the eastern Andean foreland front (33{ring operator}20' S in Argentina), provides new clues for the interpretation of deep piedmont entrenchments. Both the Las Tunas mountain catchment and its piedmont are strongly entrenched with maximal incision of over 100 m at the mountain front. Three main terrace levels are well exposed and are labelled T1, T2 and T3 from the youngest to the oldest. We combined geological and geomorphological field observations, kinematic GPS data, satellite data and aerial photos with geochronological 40Ar/39Ar and 10Be analysis to provide a detailed description of terrace organization and a discussion of the evolution of the Las Tunas landscape. The surprisingly constant 10Be concentrations in surface layers as deep as 1.5 m show that gently dipping alluvial surfaces can be continuously and deeply mixed. Our data show a first period of deposition (Mesones Fm) before 0.85 Myr (minimum T3 age), followed by deep erosion and a second sedimentation period (Las Tunas Fm) that includes a ca. 0.6 Myr ash deposit. T2 and T1 are inset in the Las Tunas Fm and were abandoned ca. 15-20 kyr ago. The similar ages for T2 and T1 show that post-20 kyr entrenchment occurred very rapidly. Despite Quaternary deformation in the Las Tunas piedmont, terrace entrenchment is best explained by paleo-climatic changes. The terrace organization reveals that the erosion-sedimentation phases affected the entire system from the piedmont toe to 10 km upstream of the mountain front. Finally, contrary to the neighbouring more deeply incised Diamante River system, where late Quaternary piedmont uplift is more likely to have been a factor causing incision, the more stable Las Tunas system provides an incomplete geomorphological record of Pleistocene and Holocene climate variations. We suggest that climate variations are better recorded in uplifting piedmonts than in stable ones, where the magnitude of incision and sedimentation and the fact that they occur repeatedly at the same elevation can erase a large part of the record.",
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Pepin, E, Carretier, S, Hérail, G, Regard, V, Charrier, R, Farías, M, García, V & Giambiagi, L 2013, 'Pleistocene landscape entrenchment: A geomorphological mountain to foreland field case, the Las Tunas system, Argentina', Basin Research, vol. 25, n.º 6, pp. 613-637. https://doi.org/10.1111/bre.12019

Pleistocene landscape entrenchment : A geomorphological mountain to foreland field case, the Las Tunas system, Argentina. / Pepin, E.; Carretier, S.; Hérail, G.; Regard, V.; Charrier, R.; Farías, M.; García, V.; Giambiagi, L.

En: Basin Research, Vol. 25, N.º 6, 12.2013, p. 613-637.

Resultado de la investigación: Article

TY - JOUR

T1 - Pleistocene landscape entrenchment

T2 - A geomorphological mountain to foreland field case, the Las Tunas system, Argentina

AU - Pepin, E.

AU - Carretier, S.

AU - Hérail, G.

AU - Regard, V.

AU - Charrier, R.

AU - Farías, M.

AU - García, V.

AU - Giambiagi, L.

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AB - The study of the Las Tunas River incisions, located in the eastern Andean foreland front (33{ring operator}20' S in Argentina), provides new clues for the interpretation of deep piedmont entrenchments. Both the Las Tunas mountain catchment and its piedmont are strongly entrenched with maximal incision of over 100 m at the mountain front. Three main terrace levels are well exposed and are labelled T1, T2 and T3 from the youngest to the oldest. We combined geological and geomorphological field observations, kinematic GPS data, satellite data and aerial photos with geochronological 40Ar/39Ar and 10Be analysis to provide a detailed description of terrace organization and a discussion of the evolution of the Las Tunas landscape. The surprisingly constant 10Be concentrations in surface layers as deep as 1.5 m show that gently dipping alluvial surfaces can be continuously and deeply mixed. Our data show a first period of deposition (Mesones Fm) before 0.85 Myr (minimum T3 age), followed by deep erosion and a second sedimentation period (Las Tunas Fm) that includes a ca. 0.6 Myr ash deposit. T2 and T1 are inset in the Las Tunas Fm and were abandoned ca. 15-20 kyr ago. The similar ages for T2 and T1 show that post-20 kyr entrenchment occurred very rapidly. Despite Quaternary deformation in the Las Tunas piedmont, terrace entrenchment is best explained by paleo-climatic changes. The terrace organization reveals that the erosion-sedimentation phases affected the entire system from the piedmont toe to 10 km upstream of the mountain front. Finally, contrary to the neighbouring more deeply incised Diamante River system, where late Quaternary piedmont uplift is more likely to have been a factor causing incision, the more stable Las Tunas system provides an incomplete geomorphological record of Pleistocene and Holocene climate variations. We suggest that climate variations are better recorded in uplifting piedmonts than in stable ones, where the magnitude of incision and sedimentation and the fact that they occur repeatedly at the same elevation can erase a large part of the record.

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