Quaternary Glacial History of the
Chilean Andes
Presented by Calvin Wight
http://solarviews.com/cap/earth/chile.htm
Outline
• Background
• Controls on Glaciation
– Climatic
– Tectonic
– Latitudinal
• Glacial History of the Chilean Andes
– Northern
– Central
– Southern
Background
• Andes: a Mesozoic-Tertiary
orogenic belt trending from north
to south and form the spine of
South America
• Span from subpolar (56˚S) to warm
tropical (18˚S) regions Observations
of glaciation recorded since Charles
Darwin’s 1830’s circumnavigation in
the HMS Beagle
http://maps.maphill.com/chile/3d-maps/physical-map/physical-3d-map-of-chile.jpg
Time Scale
Present
0.01 Ma
1.8 Ma
http://www.kgs.ku.edu/Publications/Bulletins/TS7/gifs/fig22.gif
Controls on Glaciation
• Regional Climate
• Tectonics (Altitude)
• Latitude (Polar  Warm Temperate)
Regional Climate
• Precipitation regimes
• Westerly vs tropical wind belts
• Temperatures
http://wps.prenhall.com/wps/media/tmp/labeling/2131555_dyn.jpg
Tectonics
• Controlling factor on elevation
• Plays a large role forming in climatic barriers
(i.e. orogenic deserts)
http://goodtaste.tv/wp-content/uploads/2012/11/P10203721.jpg
Latitude
• Lower Latitudes (closer to the equator) will be
home to inherently warmer climates, so
elevation will play a greater role
• Higher latitudes (more polar) will have cooler
climates, and fewer constraints on glacial
extents
http://juliendaget.perso.sfr.fr/Clem/6100positionnement.html
Quaternary Glacial History of the
Chilean Andes
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•
•
•
Lines of evidence used in this study
Northern Andes
Central Andes
Southern Andes
Lines of Evidence for Glacial Intervals
• Morphology of glacial deposits
• Equilibrium Line Altitudes
• Dating Techniques: both quantitative and
relative
• Comparative Weathering older deposits will
have undergone more weathering
Equilibrium Line Altitudes and
Topography of the Chilean Andes
Average topography along Chilean Andes from 18˚-51˚S with estimate of modern glacial
Equilibrium Line Altitude from Clapperton, 1994.
Northern Chilean Andes
• 18˚30’S – 27˚S
• Hyper arid high elevation environment
• Separated by South American Dry Diagonal
– Northern: 18˚30’–26˚S
– Southern: 26˚-29˚S
• Lies within transition zone between tropics
and westerly wind belts
– Tropical: summer precipitation
– Westerly: winter precipitation
Just how dry is this place?
http://www.overlandexpo.com/whats-new/2015/2/20/northern-chile-the-andes-atacama
“Northern Northern” Chilean Andes
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•
•
•
18˚30’–26˚S
Comprised of individual tall volcanic cones
Most of the region glaciated in the late Pleistocene
Debate over “cool” vs “humid” hypothesis
– Reconstructed ELA below volcanic peaks indicates
humidity to be the limiting factor
• In moraines, underlying peat and overlying volcanic
debris dated to 13,500-12,040 14C years BP for last
glaciation
“Southern Northern” Chilean Andes
• 26˚-29˚S
• Large mountain ranges and deep valleys change in
glacial attributes
• Steep ELA gradient (800m) decreasing from north to
south
• Glaciation is humidity dependent, due to lowering
ELA from latitudinal position northward migration
of westerlies
Northern Chilean Glaciation
• Lateral moraines depict three stages of
glaciation in the late Pleistocene
• Glacial characteristics change with topography
from high elevation individual volcanic cones
to mountain range-valley topography
• Aridity implies that humidity is the major
limiting factor in glaciations
Central Chilean Andes
• 29˚- 33˚S
• Transitional Zone between subtropicaltemperate climates
• Topographically high regions with net
precipitation increasing from north to south
• Two basins: Rio Aconcagua and Rio Elqui basin
Central Andes
(herd of alpaca for scale)
https://en.wikipedia.org/wiki/Andes
Central Andean Glacial Indicators
• Rio Elqui Basin (30˚S): evidence of two glacial
stages exist from weathered moraines
• Rio Aconcagua basin (33˚S): at least three major
glacial stages are apparent from moraines
• ELA slopes upwards from west to east
• Suggests that glacier expansions in the region are
a product of increasing precipitation regimes
from a northward shift in the westerlies
Central Andean Glacial Chronology
• Three observed moraine stages mark glacial
intervals in Central Chilean Andes
• Ages of morainal drifts:
– Penitentes- >40,000 yr BP (230Th/232Th and Useries)
– Horocenes- late Pleistocene (unweathered till,
fresh morphology)
– Almacenes- late-glacial, farther up valley (14,00010,000 yr BP)
Southern Chilean Andes
•
•
•
•
33˚-56˚S
Much of Andean highland lies above 4000m
Undergone extensive Pleistocene glaciation
33˚-37˚S not widely studied due to Holocene
volcanism covering glacial deposits
• Region de los Lagos (39˚-42˚S) is the most
widely studied due to well exposed glacial
morphologic deposits
Region de los Lagos (Lake District)
https://sco.wikipedia.org/wiki/Los_Lagos_Region
Greatest Evidence for Pleistocene
Glaciation
• Four mappable drift sheets composed of till
and outwash within Lago Llanquihue basin
• Drifts from youngest to oldest:
– Llanhique
– Santa Maria
– Rio Llíco
– Caracol
Drift extent mapped
by Porter, 1981.
Llanqihue Drift
• Last major expansion of Andean glacial system
composed of three episodes of glacial advance
• Llanquihue I- 58,000-30,000 yr BP
• Llanqihue II- 20,000-19,000 yr BP
• Llanqihue III- 15,400- 14,200 yr BP
Santa Maria Drift
• Western extent parallels that of the Rio Llíco
Drift
• Broad piedmont glacial system
• Contains three end moraine systems depicting
a multifaceted ice advance
Rio Llíco Drift
• Greatest glacial extent recorded in the Region
de los Lagos
• Moraines exceed limitations of radiocarbon
dating
• Paleomagnetic analysis of silts depict normal
polarity, but are potentially unreliable.
Caracol Drift
• Ice spread westward as a piedmont glacier
• Rose on east slope of coastal mountains
• Less extensive than Rio Llico Drift
Drift extent
from Porter, 1981’
Region de los Lagos
https://sco.wikipedia.org/wiki/Los_Lagos_Region
Region de los Lagos
• Last Andean glaciation confined in the
mountains north of the Lake District
• Multiple glacial advances produced piedmont
lobes within the Lake District as ELA lowered
• Post Llanqihue recession has not been studied
in detail
South of Region de los Lagos
• Extensive mountain glacier system extended
out onto the continental shelf
• As the Llanqihue system receded at the end of
the Pleistocene, calving occurred potentially
similar to what is seen presently in Glacier
Bay, Alaska
Glacier Bay, Alaska
https://lightcentric.files.wordpress.com/2010/08/margerie-glacier-glacier-bay-national-park-052720100003.jpg
Summary
• Quaternary Andean glaciation is highly variable
depending on tectonics, climate, and latitude.
• Northern Andes: hyper arid high elevation, three
late Pleistocene glaciations recorded
• Central Andes: more temperate climate, still
humidity dependent, three glacial stages
recorded between two basins
• Southern Andes: extensive glaciation recorded in
drift sheets and morainal deposits, a multitude of
glacial advances at the end of the Pleistocene.
Greater Importance?
• Chilean Andes represent the most extensive
and detailed record of glaciation in the
southern hemisphere
• Spans across multiple climatic zones
• Significant for global paleoclimate
reconstructions
References
-Ammann, C.M., B. Jenny, K. Kammer, and B. Messerli, 2001: Late Quaternary Glacier response to humidity changes in the Arid
Andes of Chile (18-29°S). Palaeogeography Palaeoclimatology Palaeoecology, v. 172, p. 313-326.
-Clapperton, C.M., 1994: The quaternary glaciation of Chile: a review. Revista Chilena de Historia Natural. v. 67, p. 369-383.
-Geyh, M.A., M. Grosjean, L. Núñez, and U. Schotterer, 1998: Radiocarbon reservoir effect and the timing of the Late-Glacial/Early
Holocene humid phase in the Atacama Desert (Northern Chile). Quaternary Research, v. 52, p. 143-153.
-Gregory-Wodzicki, K.M., 2000: Uplift history of the Central and Northern Andes: A review. Geological Society of America Bulletin,
v. 112, p. 1091-1105.
-Grosjean M., M.A. Geyh, B. Messerli, H. Schreier, and H. Veit, 1998: A Alte Holocene (<2600 BP) glacial advance in the southcentral Andes (29°S) northern Chile. The Holocene, v. 8, p. 473-479.
- Heusser, C.J., 1977: Quaternary glaciations and environments of northern Isla Chiloé, Chile. Geology, v. 5, p. 305-308.
-Hirakawa, K., M. Nogami, T. Imaizumi and A. Okada, 2000: Some basic data on the quaternary glaciation in the Chilean Lake
District. Geographical Reports of Tokyo Metropolitan University, v. 35, p. 41-49.
-Hubbard, A.L., 1997: Modeling climate, topography and palaeoglacier fluctuations in the Chilean Andes. Earth Surface Proceses
and Landforms, v. 22, p. 79-92.
-Moreno, P.I., G.L. Jacobson Jr., T.V. Lowell, and G.H. Denton, 2001: Interhemispheric climate links revealed by a late-glacial cooling
episode in southern Chile. Nature, v. 409, p. 804-808.
-Porter, J.C., 1981: Pleistocene Glaciation in Chile. Quaternery Research, v. 16, p. 263-292
Thank You
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