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Quaternary Glacial History of the Chilean Andes Quaternary Glacial History of the Chilean Andes

Quaternary Glacial History of the Chilean Andes - PowerPoint Presentation

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Quaternary Glacial History of the Chilean Andes - PPT Presentation

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

andes glacial chilean glaciation glacial andes glaciation chilean northern chile central region pleistocene los http lagos quaternary rio late

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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

http://

hqpics.org/index.php?spgmGal

=

Travel_Pictures_Part_V&spgmPic

=111&spgmFilters=