UNIVERSIDAD NACIONAL DE SAN JUAN Facultad ...

Stella M. Moreiras Geomorphology Group IANIGLA – CCT Mendoza ARGENTINA

Number of Slides Introduction to the Study area

1

Tectonic of The Andes (32ºS)

5

Active orogenic front in the Andes piedmont (32ºS)

3

Brief explanation of climate

2

Glacial Geomorphology of the Mendoza River valley

5

Huge landslides in the Central Andes

3

New findings

17

Final remarks

2

39

Indroduction to The Central Andes

Mendoza

Santiago 70º 33º Mendoza Mendoza

Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center

Tectonic Framework of Central Andes

Tectonic Framework

Andean Orogeny (18 Ma) Aconcagua Thrust Fault Belt

Tectonic Framework

Tectonic Framework

Tectonic framework of Andes 32 S

MAIN CORDILLERA

FRONTAL CORDILLERA

PRECORDILLERA

Mendoza

Aconcagua 6958 m

Plata 6200 m Precordillera 3500 m

Topography

Moreiras et al, Andean Geology 2015

Neotectonic activity

Pliocene deposits

Tr Quaternary Moreiras et al, Andean Geology 2015

Seismic hazard Maximum regional Ms 8.2 Maximum local Ms 7.2

Moreiras & Páez, GSL 2014

Environmental phenomena associated to historical earthquakes

Moreiras & Páez, GSL 2014

Climate

Pacific Anticyclone

Atlantic Anticyclone

Arid climate

Mean Monthly Precipitations ACONCAGUA 6058 m

Villavicencio Uspallata

Guido Puente del Inca Punta de Vacas

Geomorphology of the Mendoza River valley


Uspallata Glaciation MIS 10? Ash layers (sourroundings U moraine) Fission track 170±50 ky (Espizúa and Bigazzi, 1998)



Punta de Vacas Glaciation MIS 6 Ash layers (overlapping PV moraine) Fission track 134±32 ky 260±150 ky (Espizúa, 1993)



Penitentes Glaciation MIS 4 Travertine layer (overlapping P outwash terraces) U/Th series 31±3,1ky (Espizúa, 1993)



Uspallata Glaciation MIS 10? Ash layers (sourroundings U moraine) Fission track

Horcones Glaciation MIS 2 Organic Matter of a dammed lake deposits

170±50 ky (Espizúa and Bigazzi, 1998)

Radiocarbon 9,9+/- 5 ky 15+/- 2ky (Espizúa, 1993)

Penitentes Glaciation MIS 4 Travertine layer (overlapping P outwash terraces) U/Th series 31±3,1ky (Espizúa, 1993)


Huge Landslides in the Central Andes: Horcones rock avalanches

New age of Paleo-lake 14,798 – 13,886 years BP (14C) Younger fluvial deposits 13,543 – 12,098 y BP Cosmogenic ages rock avalanches 11,110±760 – 8,170±1220 Fauqué et al, 2008

Huge Landslides in the Central Andes: El abuelo – Mario Ardito rock avalanche

Cosmogenic age 10,270±1060 and 15,200±1540 y (2ə ) Fauqué et al, 2008

Huge Landslides in the Central Andes Negro rock avalanche and Amarillo Slide

Radiocarbon age of dammed paleolake 18,660± 330 y BP (Negro) Radiocarbon age of dammed paleolake 8,640±200 y BP (Amarillo) Fauqué et al, 2008

Moreiras et al, QSR 2015

Huge Landslides in the Central Andes Tigre Dormido Rock avalanche

Velocity: 100 m/s

Area actual del depósito ~ 5.1 km2 Area original ~ 8.7 km2

Volumen ~ 1.7 x 109 m3 Run out: 10 km Run up: 1850 m a.s.l. (250 m sobre el lecho del Rio Mendoza) H/D = 1.55/10

Huge Landslides in the Central Andes Tigre Dormido Rock avalanche

Huge Landslides in the Central Andes Tigre Dormido Rock avalanche Dammed lake deposits related to Tigre Dormido RA 1804 m. asl. (altura max. del paleolago) Relit Uspallata outwash terraces (1793 m asl.)

*OSL lake 43,950±3,895

Lake Volume: 1,600 x 10 6 m 3 máx (Q) 10,300 m 3/sec. Di Tommaso & Fauqué, 2005 Moreiras (Q Int, 2006)

Huge Landslides in the Central Andes Placetas Amarillas rock avalanches

Uspallata Morein deposits

Huge Landslides in the Central Andes: Placetas Amarillas rock avalanches

Placetas Amarillas I

Volumen original ~ 1.6 x 109 m3 Area actual del depósito ~ 5 km2 Area original del depósito ~ 6.8 km2 Run out: 9 km H/D = 2/9 = 0.22

*OSL lake 47,440 ± 3,700 Species identified in diatomitic levels: Amphora sp., Achnantes longipes, Central, Cymbella af. cistula cymbiformis, Cymbella ventricosa, Denticula, Fragilaria brevistriata var. Trigona, Gomphonema sp., Navicula sp., Neidium sp.?, Nitzschia sp.

Lake sequence Thickness 32 m Max Elevation 2238 m asl. Covered Area ~ 0.12 km2 Volumen ~ 4x106 m3

Min Elevation 2206 m asl. Original Area ~ 0.28 km2 Original Lake Volumen 9x106 m3

Ar39/Ar40

biotite

350 + 80 Ka

Moreiras (Qt Int, 2006

Huge Landslides in the Central Andes Piedras Blancas rock avalanches

Huge Landslides in the Central Andes Piedras Blancas rock avalanches PB I and PB II

Avalancha de rocasHuge Piedras Blancas in the Central Andes Landslides Piedras Blancas rock avalanches: PB I and II

Piedras Blancas rock avalanche II – dammed paleolake Secuencia lacustre deformada

2660 m a.s.l.

2650 m a.s.l.

Huge Landslides in the Central Andes

Piedras Blancas rock avalanche III – dammed paleolake

1677 m a.s.l. 1648 m a.s.l.


NO PALINOLOGICAL CONTENT No Organic Matter

Thickness 30 m máx. Elevation 2648 m asl. Area ~ 0.075 km2 Volumen ~ 2.25x106 m3

Min Elevation min. 2677 m asl. Original Area ~ 0.75 km2 Original Volumen ~ 2.4x107 m3


Cerdeño et al MCN 2008

Hippidion devielli (Orden Perissodactyla; Familia Equidae)

Hippidion distribution during Pleistocene in South America

Piedras Blancas rock avalanche III

Ash levels

PA2 52.30±6.57 47.09 ±6.07 49,695±6,320

Late Pleistocene

PA3 112.87±14.07

PB3 74.21±10.94# 104.57±22.61 112.54 ±23.83 128.90±25.32 115,336±23,920 # sample omitted ** Hippidion devillei PB1 109.90 ±15.89 138.46 ±17.3 124,180±16,595 *10Be 102,944 ±4,177

36 Cl -14 samples 10 Be – 4 samples OSL dating of paleolakes (2 samples)

Middle Pleistocene

Cosmogenic datings

TD 46.71±2.7 46.42±3.78 46,565±3,265 *OSL lake 43,950±3,895

PA1 163.90 ±21.86 155.05 ± 13.53 159,475±17,695 *OSL lake 47,440 ± 3,700

Moreiras et al, Quaternary Science Review 2015

PB2 208.36 ±47.58 175.54 ±37.11 191,950±42,345

FACT: New numerical datings of huge landslides in the Central Andes contrast with traditional glacial chronology

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