ISSN 1064�2293, Eurasian Soil Science, 2010, Vol. 43, No. 13, pp. 1430–1438. © Pleiades Publishing, Ltd., 2010.

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1 INTRODUCTION

The relation between soil and landscapes consti�tutes a topic of great relevance in soil science [13]. Thehistory of a soil is related to the history of the land�scape in which it is located [1, 14]. Several soil/land�scape studies have been carried out in glacial areasaround the globe [2, 7, 12, 16, 17). However, littleresearch on soil�landscape relationships has beendone in Patagonia where glacial retreat has been rela�tively recent [8, 9, 15]. Moreover, all of that researchwas carried out on the more arid western side of theAndes Mountains, where the present climatic andgeomorphic conditions are very different from theconditions in our study area east of the Andes.

The geomorphology of the area between theNorthern and Southern Patagonian Ice Fields is dom�inated by the glacial effects on the landscape [11, 32].Although the glacial and structural geology are reason�ably well understood little is known about the proper�ties and distribution of soils in the region.

We present the results of research on soils located atthe confluence of the three sub�basins within the BRB(Baker River Basin), namely E1 Salto, E1 Manzano,

1 The article is published in the original.

and Los Ñadis, as well as the upper part of the PascuaRiver Basin (PRB) (Fig. 1). Our objectives were toinvestigate the relationships between landscape andsoil properties and to assess the extent to which soilproperties reflect the past and present soil�formingenvironments.

Physical Setting

The section of the Andes located south of 41°S isknown as the Patagonian Mountain Range, whichstarted to form in the Late Cenozoic. At the sametime, the Chile Ridge, which separates the NazcaPlate from the Antarctic Plate, was subducting [25].The Andes Mountain Range in this area is composedof the Patagonian Batholith and the pre�Jurassic base�ment. Miocene�age intrusions have been describedalong the eastern boundary of the PatagonianBatholith, e.g. at Fritz Roy (elevation 3405 m) andMount San Lorenzo (3706 m). The sub�Andean Pre�cordillera is composed mainly of Jurassic volcanicrocks [22, 27, 34].

During the last glacial maximum, the areas inwhich the BRB and PRB are located were covered bythe Patagonian Ice Sheet, which may have extendedbetween 38°S and 56°S [4, 6, 11]. Currently, there are

Soils of Chilean Patagonia in Glacial and Periglacial Environments1

M. Pfeiffera, b, C. Mascayanoc, and F. Aburtod, b

aDepartamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de ChilebDepartamento de Ingeniería y Suelos, Facultad de Ciencias Agronómicas, Universidad de Chile

cPOCH Ambiental S.A, Renato Sanchez 3838, Las Condes, Santiago de ChiledSoils and Biogeochemistry Graduate Group, University of California Davis, USA

E�mail: mpfeiffer@ug.uchile.clReceived April 16, 2010

Abstract—Previous studies have shown that the area between the present Northern and Southern PatagonianIce Fields (47°S to 48°S) was covered with ice during the Last Glacial Maximum (16000 BP). The ice retreatgenerated a typical glacial geomorphology with moraines, kettles, kame terraces, fluvioglacial terraces andfluvial terraces. Until now, there have been no detailed studies to determine the type of soils in the area. Wedescribed and classified one hundred and fifty pedons located in the Baker River Basin (47°S) and the PascuaRiver Basin (48°S), which we correlate with the respective geomorphology. The mean annual precipitation is1000 mm for the Baker River study area and 2500 mm for the Pascua River Basin area, whereas the averageannual temperature is 9°C and 7°C, respectively. Based on previous studies that described the glacial fluctu�ations of the Northern and Southern Ice Fields and considering the presence of a volcanic ash layer due tothe major Holocene eruptions of the Hudson Volcano (6700 BP), tentative soil profile ages are proposed, andthe geomorphologic and soil descriptions are presented. Soils are classified as Entisols, Inceptisols, and His�tosols, reflecting weak pedogenetic development, and consistent with the landscape age and climatic condi�tions.

DOI: 10.1134/S106422931013003X

GEOGRAPHY AND CARTOGRAPHY OF SOILS

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SOILS OF CHILEAN PATAGONIA IN GLACIAL 1431

two large relict ice masses. The North Patagonian IceField (NPI) is located between 46°30′ and 47°30′, cov�ering a total area of approximately 4200 km2, whereasthe South Patagonian Ice Field (SPI) lies between48°20′ and 51°30′S, and covers an area of approxi�mately 13000 km2. These are considered to be world’slargest terrestrial ice masses in current temperate cli�mates [11].

The present landscape in the study area has beenshaped by glacial activity during the Quaternary [10,11, 32], influenced by geologic�tectonic features [33].During the Quaternary, these ice masses may haveexpanded and contracted at different periods due toclimatic conditions, coalescing at certain periods to

form the much larger Patagonian Ice Sheet [11]. Thelast period of expansion may have occurred during theLast Glacial Maximum or LGM [4, 6, 11]. Accordingto Rabassa et al. [24] the LGM occurred between25000 and 16000 cal. yrBP, followed by subsequentmajor advances during the interglacial period (15000–1000014C yr BP).

The vegetation in the area consists of typical suban�tarctic species, dominated by species of the Nothofagusgenus including N. nitida (Phil.) Krasser, N. betuloides(Mirb.) Oerst., N. pumilio (Poepp. et Endl.) Krasser,and N. Antarctica (G.Forst.) Oerst. Other importantspecies described in the area are Pilgerodendronuviferum (D.Don) Florin, Tepualia stipularis (Hook.

Legend

Soil Study Area

Road Network

Main Road

Secondary Road

Boundaries

International

Coast line

Rivers

Icefields

Lakes and Ponds

SouthPatagonian

Icefield

48°S

73°W 72°W

Cerro Tamango

Lago

Lago

Cerro Cola de LeonCerro Teta de Leon

Cochrane

LagoCachet Dos

Lago

LagoLos Huemules

Lago

Cerro Desfiladero

Lago Juncal

Lago

Laguna Larga

Cerro Rodados

Baker River

Cerro Barrancoso

Guillermo

Chacabuco

Esmeralda

N

S

W E Beltrand

7

Colonia

LagoCochrane

NorthPatagonian

Icefield

Cerro

7

7

CerroTres Frailes

LagoLos Bergues Lago

Gabriel Quiroz

LagoO'higgins

LagoBriceno

Region de Ausen Gral.

Region de Magallanes

Carlos Ibanez del Campo

y la Artartica Chilena

Horacio

74°W

47°S

AR

GE

NT

INA

45°S

50°S

75°W 70°W

0 25 km

Region de Los Lagos

Pascua R

iver

100 km0

Fig. 1. Location of study area.

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PFEIFFER et al.

Et Arn.) Griseb., Amomyrtus luma (Molina) D. Leg�rand et Kausel, and Podocarpus nubigena Lindl. [26].

Baker River Basin (BRB)

The geology of the BRB corresponds mainly to anextensive Paleozoic sedimentary�metamorphic com�plex locally known as the Eastern Andean Metamor�phic Complex. The Jurassic volcanic sedimentary for�mations have been described locally, but there is noevidence of active volcanism in the area. In fact, thestudy area forms part of the sector called the “Patago�nian volcanic gap”. The Hudson Volcano is the closestactive volcano, located 130 km to the north of thestudy area, and is considered to be the southernmostvolcano of the Southern Volcanic Zone [28]. This vol�cano had two explosive eruptions during the Quater�nary (3600 BP and 6700 BP). According to Naranjoand Stern [20] the ashes from those eruptions mayhave reached the study area. More recent eruptions(like the one that occurred in 1991) did not deposit ashin the study area [19].

The origin of the BRB is in the General Car�rera/Buenos Aires Lake, the Patagonia Ice Field beingits major contributor. The total area of this basin is26456 km2. According to Turner et al. [32], this riveroriginated in the late Pleistocene, whereas Wenzens[33] maintains the idea that the river formed duringthe first part of the Holocene, and now separates theNPI and SPI. The ice retreat yielded a series of termi�nal moraines, which were dated in the Ness and LosÑadis River Valleys as well as in the Chacabuco andEsmeralda Lakes, with approximate ages of 12 kabased on cosmogenic nuclides of 10Be [32].

After the last glacial advance, these valleys mayhave been occupied by large lakes. The occurrence ofa large lake was probable at the confluence of the Cha�cabuco and Baker Rivers [21, 32]. Striations androches moutonnée are common on a wide array oflithologies in the valley [21]. The Baker River showsextensive fluvio�lacustrine deposits at confluences, aswell as fluvial and glaciofluvial terraces [21] withmeander relicts and wide flood plains with finerdeposits [34].

Pascua River Basin (PRB)

There is a lack of information on the high elevationportions of the PRB between the Quetru and O’Hig�gins Lakes, mainly because of the extremely difficultaccess to the area (being only possible by helicopter).

The PRB is primarily composed of Paleozoic East�ern Andean Metamorphic Complex rocks. Theserocks show dikes with a variety of compositions frombasaltic to granitic [3]. The Lautaro Volcano, located80 km to the south, is active in the area, although thereis little documentation of this activity [18, 23]. Ash

deposits were not found during this study, possibly dueto the high precipitation and steep topography thatmay affect the preservation of this kind of deposits.

The origin of PRB is in the O’Higgins/San MartinLake, its major contributor being the SPI. The PRBhas a total area of approximately 14500 km2 [3] andthe Pascua River Valley was covered by a glacier duringthe LGM. This glacier would have been part of themajor NPI flowing into the sea approximately 80 kmto the west [33]. The glacial retreat was not dated in thearea. However, it is estimated that this process mayhave occurred during the Holocene [33]. This can alsobe inferred because of the scarce vegetation and pres�ence of the unconsolidated deposits [3].

OBJECTIVES

The main objectives of this study were: 1) to inves�tigate soils of an area located within the Pascua RiverBasin (PRB) and an additional area within the BakerRiver Basin (BRB) in Patagonia, and 2) to determinerelationships between soils and the glacial geomor�phology of the area.

METHODOLOGY

The procedures used in this study were as follows:—Photo�interpretation of the landforms in the

study area using oblique aerial ortho�rectified photo�graphs at a scale of 1 : 20000;

—Mapping the landforms in ArcGIS 9.1, sup�ported by a DEM generated from contour lines every40 m. Soil areas were identified from the landformsand were checked in the field [29];

—Survey points were selected according to theidentified soil areas. Each area with a surface exceed�ing 50 ha had at least 1 soil profile. We described andclassified 150 soil profiles following the Soil SurveyStaff [30, 31] procedures. Each soil profile wasassigned to a specific soil area and, therefore, corre�lated with similar areas;

—Polygons containing soil information were gen�erated at a scale of 1 : 20000 using ArcGIS 9.1.

RESULTS AND DISCUSSION

The majority of the soils are developed in the mate�rials derived from the Eastern Andean MetamorphicComplex. A limited number of the BRB pedonsformed in Jurassic volcanic�sedimentary formationsand volcanic ash deposits. The latter probably corre�spond to the 6700 BP eruption of the Hudson Volcanodescribed by Naranjo and Stern [20].

In glacial landscapes, soil development beginssimultaneously with glacial retreat, so that one canargue that the development of the soils in our study

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SOILS OF CHILEAN PATAGONIA IN GLACIAL 1433

area started after the last ice retreat at approximately12 ka in the BRB [32]. Although there are no absoluteages registered for the PRB, the ice retreat would haveoccurred later than in the BRB [33].

BRB Area

We mapped twelve landforms in the BRB area andgrouped these landforms into three major categories:glacial (moraines, stoss and lee topography, kame ter�races, and eskers), periglacial (fluvioglacial terraces,kettles, loess and outwash plains), and postglacial(alluvial, alluvial fans, colluvial, and fluvial terraces).The glacial forms are the result of glacial retreat fromthe study area in the BRB, which occurred around12600 ka BP [32]. Simultaneously with this event, theperiglacial deposits were formed, followed by post�gla�cial fluvial deposits considered to be the youngest. Asa result, we can assume that a succession of consecu�tive landscape processes occurred in the BRB (Fig. 2),i.e. fluvial landscapes superimposed on the initial gla�cial and periglacial landscapes.

The succession of landscape�modifying agents mayexplain the predominance of Entisols on the fluvialterraces, which are the youngest soil units in this area(Fig. 3). The described Inceptisols are primarilylocated in areas where roches moutonnée dominate(stoss and lee landforms) (Fig. 3). These are the firstexposed surfaces after the ice retreat, being the domi�nant landforms left behind after the advance of largeice masses. Based on that, these can be associated withthe time during which the great Patagonian Ice Sheetwas present. Fluvioglacial terraces are the landformsthat have the highest number of soil taxonomic sub�groups in the area.

Histosols were only found in kettles (Fig. 4). Therelatively low annual precipitation along the BakerRiver does not support much organic matter accumu�lation on other landforms, but the kettle depressionsno doubt accumulate the runoff water, leading to theformation of Histosols. The two organic soilsdescribed in the BRB have a depth of more than 4 m,which may indicate the existence of an old wetlandthat might have formed after ice melting in those areas.

Fig. 2. An upstream view of the landscape of the Baker River Valley near the confluence of the Baker and Chacabuco Rivers. Dot�ted line: Glacial U�shaped valley morphology. White line: Fluvial V�shaped erosion. A: glacial shoulder. B: Stoss and lee topog�raphy C: Fluvial terrace.

AB

C

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PFEIFFER et al.

PRB Area

In the PRB we found six major landforms, two ofwhich are glacial (moraine and stoss�lee topography),one is periglacial (fluvioglacial terrace), and three are

postglacial (alluvial fan, colluvial, and fluvial terrace).Entisols and Histosols are the two soil orders found inthis basin, with Inceptisols absent in contrast to theBRB area (Fig. 5). The latter might be explained bythe following factors: First, the presumed shorter

Legend

Orders of SoilEntisolHistosolInceptisol

Road Network

Main Road

Secondary RoadHidrology

Glacier front afterTurner et al. 20054

5 cm isopach for the

volcano eruption3

BAKER RIVER BASIN

6700 BP Hudson

LagoEsmeralda

LagoJuncal

LagoChacabuco

LagunaLarga Rio D

el Salto

Los Alamos

Rio de

Rio Baker

Cochrane

12.670 BP

El Salto

5

7

12.670 BP

7El Maiten

El MazanoRio Nef

12.660 BPRio Baker

N

S

W E

la Colonia

7

5

Rio Bertrand

0 1 : 200000 10 km

47°30′S

73°0′W 72°45′W

47°15′S

Fig. 3. Baker River Basin study area with soil orders distribution.

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SOILS OF CHILEAN PATAGONIA IN GLACIAL 1435

exposure time of the land surface as compared to theBRB area (requiring confirmation by numerical dat�ing methods). Second, the absence of easily weatheredvolcanic deposits (present in BRB), which may con�tribute to the development of the necessary color andstructure for a cambic horizon [5]. The last, but not

least is the predominance of lower temperatures in thearea that presumably slowed the rate of soil formation.

The Histosols in the area cover extensive stoss andlee topography (Fig. 6). It is interesting that these soilsoccupy sites with slopes greater than 95%. Hydric Cry�ofibrists are restricted to concave microtopography on

Alluvial Fluvaquentic Dystrudept

Alluvial fan

Colluvial

Esker

Fluvioglacialterrace

Typic Dystrudept

Typic Dystrudept

Humic Lithic Dystrudept

Lithic UdorthentTypic DystrudeptTypic FragiudeptTypic Udorthent

Vitrandic Udorthent

Lithic Dystrudept

Aquertic UdifluventFluventic DystrudeptHumic Psammentic DystrudeptOxyaquic DystrudeptOxyaquic Udifluvent

Typic DystrudeptTypic Udorthent

Typic Udorthent

Typic DystrudeptTypic Endoaquent

Typic UdifluventTypic Udipsamment

Typic Fragiudept

Typic Dystrudept

Typic Dystrudept

Typic DystrudeptTypic Fragiudept

Lithic UdorthentLithic Dystrudept

Lithic UdorthentLithic Dystrudept

Terric Sulfihemist

Typic UdorthentVitrandic Udorthent

Typic Dystrudept

Typic DystrudeptTypic Udorthent

Typic UdifolistKettle

Fluvialterrace

Loess

Kame terrace

Humic Dystrudept

Oxyaquic Dystrudept

Morrain

Outwash plain

Stoss and Leetopography

GEOMORPHOLOGY SOIL SUBGROUP

Fig. 4. Geomorphology and soil subgroups for the Baker River basin.

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PFEIFFER et al.

the steep slopes where water must accumulate. In con�vex zones and steeper hillsides the main soils are LithicCryofibrists, which are generally shallower than thesoils in the depressions. The presence of Histosols inhigh�slope areas may be due to low temperatures, andhigh, uniformly distributed annual precipitation(more than 2500 mm/year) in the PRB area. The PRBarea Histosols are located in the sites that have been

exposed for longer periods of time compared to loca�tions where Entisols are predominant. Because of this,Histosols are associated with older landforms linked toglacial retreat. The Entisols are primarily located onyounger, post�glacial landforms corresponding to gla�ciofluvial and fluvial terraces, as well as colluvial andalluvial fans. Entisols and Histosols were alsodescribed on glaciofluvial terraces, which might be

Legend

Orders of SoilEntisolHistosol

Road Network

Main Road

Secondary RoadBoundaries

PASCUA RIVER BASIN

Hidrology

Coast lineIcefields

48°0′S

73°15′W 72°45′W73°0′W

48°15′S

LagoO'Higgins

Lago Gabriel Q

uires

LagoO'Higgins

Lago Bergues

Bajo Pascua

Caleta Buzeta

El Sordo

7X�906

LagoQietru

Lago Chico

Est

ero

Stee

le

SouthPatagonian

Icefield0 1 : 250000 10 km

7

N

S

W E

Rio Bravo

Michell

LagoLeal

Ventisquero Gabriel Quiroso Pascua

Rio Pascua

Fig. 5. Pascua River Basin and soil orders distribution.

EURASIAN SOIL SCIENCE Vol. 43 No. 13 2010

SOILS OF CHILEAN PATAGONIA IN GLACIAL 1437

considered as geomorphological elements of interme�diate age between the moraine forms and fluvial ter�races. This may partially explain why this area has thegreatest number of taxonomic soil subgroups, beingthe only that contains Entisols and Histosols (Fig. 6).

CONCLUSIONS

This study contributes to the available informationon soils occurring in Patagonia, which has beenscarce.

Entisols, Inceptisols and Histosols are the only soilorders found in the area. These are weakly developedsoils reflecting a combination of young landscapes anda relatively cool climate associated with the present�day Patagonia Ice Fields.

In the BRB we can assume that a succession ofconsecutive landscape modeling occurred, being thefluvial modeling superposed to the initial glacial mod�eling. This may explain the predominance of Entisolson the fluvial terraces being considered the youngestsoil unit in this area.

The Inceptisols described primarily in the areaswith stoss and lee topography domains, they can beassociated with the time at which the great PatagonianIce Sheet was present; due to these areas are the firstexposed surfaces after the ice retreat.

The predominant wetter and colder climatic con�ditions in PRB would have favored the accumulationof organic matter in areas where the surface had beenexposed sufficiently long to form Histosols rather thanInceptisols like in the BRB.

The greater variety of soil types present in the BRBin comparison with the PRB, can be explained by alarger number of different landforms. This is probably

related to its greater age and a succession of geomor�phological processes. The relationship between soiltypes and landforms in these areas requires furtherstudy.

ACKNOWLEDGMENTS

This study was supported by Hidroaysén S.A. Theauthors are also grateful to Dr. Juan J. Ibañez,Dr. Randal Southard and Dr. Jacobus Le Roux fortheir constructive reviews.

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