Presented by Calvin Wight http solarviewscom capearth chilehtm Outline Background Controls on Glaciation Climatic Tectonic Latitudinal Glacial History of the Chilean Andes Northern ID: 442513
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Slide1
Quaternary Glacial History of the Chilean Andes
Presented by Calvin Wight
http://
solarviews.com
/cap/earth/
chile.htmSlide2
Outline
BackgroundControls on GlaciationClimaticTectonicLatitudinal
Glacial History of the Chilean AndesNorthernCentralSouthernSlide3
Background
Andes: a Mesozoic-Tertiary orogenic belt trending from north
to south and form the spine of South AmericaSpan 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.jpgSlide4
Time Scale
http://
www.kgs.ku.edu/Publications/Bulletins/TS7/gifs/fig22.gif
1.8 Ma
0.01 Ma
PresentSlide5
Controls on Glaciation
Regional ClimateTectonics (Altitude)Latitude (Polar Warm Temperate)Slide6
Regional Climate
Precipitation regimesWesterly vs tropical wind belts
Temperatures
http://
wps.prenhall.com
/
wps
/media/
tmp/labeling/2131555_dyn.jpgSlide7
Tectonics
Controlling factor on elevationPlays a large role forming in climatic barriers (i.e. orogenic deserts)
http://goodtaste.tv/
wp
-content/uploads/2012/11/P10203721.jpgSlide8
Latitude
Lower Latitudes (closer to the equator) will be home to inherently warmer climates, so elevation will play a greater roleHigher latitudes (more polar) will have cooler climates, and fewer constraints on glacial extents
http://
juliendaget.perso.sfr.fr
/Clem/6100positionnement.htmlSlide9
Quaternary Glacial History of the Chilean Andes
Lines of evidence used in this studyNorthern Andes Central AndesSouthern AndesSlide10
Lines of Evidence for Glacial Intervals
Morphology of glacial depositsEquilibrium Line AltitudesDating Techniques: both quantitative and relative
Comparative Weathering older deposits will have undergone more weatheringSlide11
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.Slide12
Northern Chilean Andes
18˚30’S – 27˚SHyper arid high elevation environmentSeparated by South American Dry DiagonalNorthern: 18˚30’–26˚S
Southern: 26˚-29˚SLies within transition zone between tropics and westerly wind belts Tropical: summer precipitationWesterly: winter precipitationSlide13
Just how dry is this place?
http://
www.overlandexpo.com/whats-new/2015/2/20/northern-
chile
-the-
andes
-
atacamaSlide14
“Northern Northern” Chilean Andes
18˚30’–26˚S C
omprised of individual tall volcanic conesMost of the region glaciated in the late PleistoceneDebate 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
14
C years BP for last glaciationSlide15
“Southern Northern” Chilean Andes
26˚-29˚S
Large mountain ranges and deep valleys change in glacial attributesSteep ELA gradient (800m) decreasing
from
north
to
south
Glaciation is humidity dependent, due to lowering ELA from latitudinal position northward migration of
westerliesSlide16
Northern Chilean Glaciation
Lateral moraines depict three stages of glaciation in the late PleistoceneGlacial characteristics change with topography from high elevation individual volcanic cones to mountain range-valley topographyAridity implies that humidity is the major limiting factor in glaciationsSlide17
Central Chilean Andes
29˚- 33˚STransitional Zone between subtropical-temperate climatesTopographically high regions with net precipitation increasing from north to south
Two basins: Rio Aconcagua and Rio Elqui basinSlide18
Central Andes (herd of alpaca for scale)
https://
en.wikipedia.org/wiki
/AndesSlide19
Central Andean Glacial Indicators
Rio Elqui Basin (30˚S): evidence of two glacial stages exist from weathered morainesRio Aconcagua basin (33˚S): at least three major glacial stages are apparent from moraines
ELA slopes upwards from west to eastSuggests that glacier expansions in the region are a product of increasing precipitation regimes from a northward shift in the westerliesSlide20
Central Andean Glacial Chronology
Three observed moraine stages mark glacial intervals in Central Chilean AndesAges of morainal drifts:
Penitentes- >40,000 yr BP (230Th/232
Th and U-series)
Horocenes
-
late
Pleistocene (
unweathered till, fresh morphology)Almacenes- late-glacial, farther up valley (14,000-10,000 yr BP)Slide21
Southern Chilean Andes
33˚-56˚SMuch of Andean highland lies above 4000mUndergone extensive Pleistocene glaciation33˚-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 depositsSlide22
Region de los Lagos (Lake District)
https://
sco.wikipedia.org/wiki/
Los_Lagos_RegionSlide23
Greatest Evidence for Pleistocene Glaciation
Four mappable drift sheets composed of till and outwash within Lago
Llanquihue basinDrifts from youngest to oldest:LlanhiqueSanta Maria
Rio
Llíco
CaracolSlide24
D
rift extent mapped
by Porter, 1981.Slide25
Llanqihue Drift
Last major expansion of Andean glacial system composed of three episodes of glacial advanceLlanquihue I- 58,000-30,000 y
r BPLlanqihue II- 20,000-19,000 yr BPLlanqihue
III- 15,400- 14,200
yr
BPSlide26
Santa Maria Drift
Western extent parallels that of the Rio Llíco DriftBroad piedmont glacial systemContains three end
moraine systems depicting a multifaceted ice advanceSlide27
Rio Llíco Drift
Greatest glacial extent recorded in the Region de los LagosMoraines exceed limitations of radiocarbon dating
Paleomagnetic analysis of silts depict normal polarity, but are potentially unreliable.Slide28
Caracol Drift
Ice spread westward as a piedmont glacierRose on east slope of coastal mountainsLess extensive than Rio Llico
DriftSlide29
D
rift extent
from Porter, 1981’Slide30
Region de los Lagos
https://
sco.wikipedia.org/wiki/Los_Lagos_RegionSlide31
Region de los Lagos
Last Andean glaciation confined in the mountains north of the Lake DistrictMultiple glacial advances produced piedmont lobes within the Lake District as ELA lowered Post Llanqihue
recession has not been studied in detailSlide32
South of Region de los Lagos
Extensive mountain glacier system extended out onto the continental shelfAs the Llanqihue system receded at the end of the Pleistocene, calving occurred potentially similar to what is seen presently in Glacier Bay, AlaskaSlide33
Glacier Bay, Alaska
https://
lightcentric.files.wordpress.com
/2010/08/margerie-glacier-glacier-bay-national-park-052720100003.jpgSlide34
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 basinsSouthern Andes: extensive glaciation recorded in drift sheets and morainal deposits, a multitude of glacial advances at the end of the Pleistocene.Slide35
Greater Importance?
Chilean Andes represent the most extensive and detailed record of glaciation in the southern hemisphereSpans across multiple climatic zonesSignificant for global paleoclimate
reconstructionsSlide36
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 south-central 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. 263-292Slide37
Thank You
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