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2011 Mass wasting as a geologic hazard in the of , William J. Wayne University of Nebraska-Lincoln, [email protected]

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Wayne, William J., "Mass wasting as a geologic hazard in the Province of Salta, Argentina" (2011). Papers in the Earth and Atmospheric Sciences. 561. https://digitalcommons.unl.edu/geosciencefacpub/561

This Article is brought to you for free and open access by the Earth and Atmospheric Sciences, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Papers in the Earth and Atmospheric Sciences by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. CENOZOIC of the CENTRAL of ARGENTINA CENOZOIC GEOLOGY of the CENTRAL ANDES of ARGENTINA

Edited by

José A. Salfity and Rosa A. Marquillas

SCS PUBLISHER Salta, Argentina Cenozoic Geology of the Central Andes of Argentina / dirigido por José A. Salfity y Marquillas Rosa A. - 1a ed. - Salta : SCS Publisher, 2011. 458 p. : il. ; 27x21 cm.

ISBN 978-987-26890-0-1

1. Geología. I. José A. Salfity, dir. II. Rosa A., Marquillas, dir. CDD 558

It is suggested that references to this book and their chapters are written in the following way: Salfity, J.A., and Marquillas, R.A., eds., 2011, Cenozoic geology of the Central Andes of Argentina: Salta, SCS Publisher, 458 p. Folguera, A., and Zárate, M., 2011, Neogene sedimentation in the Argentine foreland between 34°30’S and 41°S and its relation to the Andes evolution, in Salfity, J.A., and Marquillas, R.A., eds., Cenozoic geology of the Central Andes of Argentina: Salta, SCS Publisher, p. 123-134.

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ISBN: 978-987-26890-0-1 Copyrighted according to 11.723 Printed at Artes Gráficas S.A., Salta, Argentina Printed in Argentina The editors would like to thank the referees whose opinions and constructive criticism have improved the quality of all contributions and thus of the entire volume. They are: Ricardo Alonso Universidad Nacional de Salta-CONICET Luis Álvarez Universidad Nacional de Salta Pablo Caffe Universidad Nacional de Jujuy-CONICET Esperanza Cerdeño Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales-CONICET Alberto Cione Universidad Nacional de -CONICET Carlos Costa Universidad Nacional de San Luis-CONICET Cecilia del Papa Universidad Nacional de Salta-CONICET Luis Fauqué Universidad de Igor J.C. Gavriloff Universidad Nacional de Tucumán-CONICET Klaus Heine University of Regensburg Rafael Herbst Universidad Nacional de Tucumán-CONICET Fernando Hongn Universidad Nacional de Salta-CONICET Jonas Kley Institut für Geowissenschaften, Univerität Jena Alejandro Kramarz Museo Argentino de Ciencias Naturales «Bernardino Rivadavia» Carlos Oscar Limarino Universidad de Buenos Aires-CONICET Vera Markgraf Institute of Arctic and Alpine Research, University of Colorado at Boulder Claudia Montalvo Universidad Nacional de La Pampa André Nel Muséum national d’histoire naturelle, Paris Silvio Peralta Universidad Nacional de San Juan-CONICET Mirtha Quattrocchio Universidad Nacional del Sur-CONICET Víctor Ramos Universidad de Buenos Aires-CONICET Augusto Ernesto Rapalini Universidad de Buenos Aire-CONICET Marcelo A. Reguero Universidad Nacional de La Plata José Luís Silvestro Dezzi YPF, Buenos Aires Luís Spalletti Universidad Nacional de La Plata-CONICET Pablo Teta Universidad de Buenos Aires Alejandro J. Toselli Universidad Nacional de Tucumán-CONICET Daniel Udrizar Sauthier Centro Nacional Patagónico-CONICET Gonzalo Veiga Universidad Nacional de La Plata-CONICET Gustavo Vergani Repsol-YPF, Buenos Aires José Germán Viramonte Universidad Nacional de Salta-CONICET Haroldo Vizán Universidad de Buenos Aires Guiomar Vucetich Universidad Nacional de La Plata-CONICET Juvenal J. Zambrano Universidad Nacional de San Juan Roland Zech University of Bern, Institute of Geography and two referees who chose not to disclose their names. Contents

Contributing Authors ...... 13 Preface...... 21

Paleogeographic, magmatic and paleoenvironmental scenarios at 30ºS during the Andean : Cross sections from the volcanic-arc to the orogenic front (San Juan, Argentina) ...... 23 María Susana Alonso, Carlos Oscar Limarino, Vanesa Dafne Litvak, Stella Maris Poma, Julieta Suriano, and Marcela Beatriz Remesal

High-T , crustal melts, and a large igneous province: The Paleozoic to Cenozoic margin of the Central Andes, N and NW Argentina ...... 47 Raúl Becchio, Friedrich Lucassen, and Gerhard Franz

Stratigraphy and sedimentology of the Neogene deposits of Puchuzum, San Juan, Argentina ...... 65 Adriana Bracco, Laura León, Mercedes Prámparo, Esperanza Cerdeño, and Víctor Contreras

Miocene- of the , Argentina ...... 75 Jorge O. Chiesa, Alberto C. Basaez, Juan J. Navío, Natalia P. Lucero, Guillermo E. Ojeda, and Edgardo N. Strasser

Tectosedimentary evolution of the La Troya and Vinchina depocenters (northern Bermejo Basin, Tertiary), La Rioja, Argentina...... 91 Patricia Lucía Ciccioli, Carlos Oscar Limarino, Sergio Alfredo Marenssi, Ana María Tedesco, and Alfonsina Tripaldi

Calibration of the - stages boundary (Neogene), San Juan, western Argentina ...... 111 Víctor Hugo Contreras and Juan Alberto Baraldo

Neogene sedimentation in the Argentine foreland between 34°30’S and 41°S and its relation to the Andes evolution ...... 123 Alicia Folguera and Marcelo Zárate

Paleontology and stratigraphy of the Aisol Formation (Neogene), San Rafael, Mendoza ...... 135 Analía M. Forasiepi, Agustín G. Martinelli, Marcelo S. de la Fuente, Sergio Dieguez, and Mariano Bond

Structural setting and diachronism in the Central Andean Eocene to Miocene volcano- tectonic basins ...... 155 Estanislao Godoy

Cenozoic Geology of the Central Andes of Argentina / 9 Contents

Geology and metal ore deposits in the Argentine Puna...... 169 Sergio A. Gorustovich, César R. Monaldi, and José A. Salfity

Fragmented Paleogene in the Valles Calchaquíes, NW of Argentina ...... 189 Fernando Hongn, Cecilia del Papa, Jaime Powell, Patricio Payrola, Ivan Petrinovic, and Ricardo Mon

New Miocene mammal assemblages from Neogene Manantiales basin, Cordillera Frontal, San Juan, Argentina ...... 211 Guillermo Marcos López, María Guiomar Vucetich, Alfredo Armando Carlini, Mariano Bond, María Encarnación Pérez, Martín Ricardo Ciancio, Daniel José Pérez, Michelle Arnal, and Adriana Itatí Olivares

U-Pb zircon age of the and its significance to the -Tertiary boundary in the , Argentina...... 227 Rosa A. Marquillas, José A. Salfity, Stephen J. Matthews, Massimo Matteini, and Elton Dantas

Quaternary environmental and climate changes in the Central Andes ...... 247 Jan-Hendrik May, Roland Zech, Andreas Schellenberger, Christoph Kull, and Heinz Veit

Clustering of Pleistocene in the Central Andes (Mendoza, Argentina) ...... 265 Stella M. Moreiras

Palynostratigraphy and paleoclimatic inferences of the Balbuena and Santa Bárbara Subgroups (Salta Group Basin, Cretaceous-Paleogene): correlation with Patagonian basins ...... 283 Paula Liliana Narváez and Wolfgang Volkheimer

Fossil sigmodontine rodents of northwestern Argentina: Taxonomy and paleoenvironmental meaning ...... 301 Pablo E. Ortiz, J. Pablo Jayat, and Ulyses F. J. Pardiñas

Quaternary tectonic activity in the piedmont of Cordillera Frontal (33°S-34°S), Mendoza ...... 317 Laura Perucca, Marcelo A. Zárate, and Adriana E. Mehl

Quaternary active transpression in the north of Western Precordillera (San Juan and La Rioja, Argentina) ...... 329 Laura Perucca and Hugo Bastías

Paleogene insects from Maíz Gordo Formation, northwest Argentina: Taphonomy, diversity and paleobiogeography ...... 337 Julián Fernando PPetrulevietrulevič ius

Eocene vertebrates of northwestern Argentina: annotated list ...... 349 Jaime E. Powell, M. Judith Babot, Daniel A. García López, M. Virginia Deraco, and Claudia Herrera

10 / Cenozoic Geology of the Central Andes of Argentina Contents

The southern Central Andes paleomagnetic data base revisited ...... 371 Claudia B. Prezzi

Altiplano-Puna elevation budget ...... 383 Claudia B. Prezzi, Hans-Jürgen Götze, and Sabine Schmidt

The Central Andes lithospheric structure from 3d gravity modeling ...... 395 Claudia B. Prezzi, Hans-Jürgen Götze, and Sabine Schmidt

Late Cenozoic mammals from the northwest of Argentina ...... 411 Marcelo A. Reguero and Adriana M. Candela

Late Cenozoic geology and geomorphology of the Loma de Las Tapias area, San Juan, west central Argentina ...... 427 Graciela M. Suvires and Víctor Hugo Contreras

Mass wasting as a geologic hazard in the Province of Salta, Argentina...... 437 William J. Wayne

Formations index ...... 455

Cenozoic Geology of the Central Andes of Argentina / 11 Mass wasting as a geologic hazard m the Province of Salta, Argentina

William J. Wayne 1

ABSTRACT

The north-south orient ation ofthe mo unta inous part ofthe Province ofSalta form s a massive barrier to easy communication between the more populate d region in the central pan ofthe provin ce and the com m unities to the west. Routes follow deeply entrenched valleys th at are frequ entl y th e sites ofdebris flows that cause disruptions in th e flow oftraffic during the months of December through M arch , wh en m ost ofthe of the region is recorded. The steep topography and the tectonic settings have resulted in nearly 150 large and debris flows most ofwhich were identified through stereo scopic study of airphoros, scale 1/50,000 and l/70,00 0. M ore than 100 ofthese are in the Cordillera Oriental and Calchaq uenia, more than 30 were noted in the Pu na, a smaller number in the Sierras Su bandinas. Several clusters of large landslides in each of th ese rnorphos truc tural regions undoub tedly were triggered by earthquak es that may have had a magnitude (Richter Scale) of5.0 or greater; thus their locations provide additional information on the probable epicenters ofpreh isto ric earthq uakes. M ost ofthe landslides ident ified do not in themselves present any hazard or risk at thi s time. Their locat ion s and geo logic setting indicate locations where un stable slopes have failed , wh ich provides a warn ing that add itional slides co uld take place in similar setti ngs. Their identificat ion and location also serves as a guide to lan d- use planners of th e pr ovince, so that if new construction is undertaken, measures to avoid reactiva ting old and no w stable slide masses can be avoided. Keywords: Salta - Escoipe - landslides - deb ris flows - rockslides -

RESUMEN

Laorientacion meridional de la parte rno ntafiosa de la Provincia de Salta ha generado una barrera que no favorece una Hcil y fluida comunicaci6n entre las regiones pobladas de la pane central de la provin cia y los pueblos del oeste. Las ru tas siguen los valles profundos donde los flujos densos y los der rum bes de roca interrum pen con frecuencia eI rrafico entre diciembre y rnarzo , cuando se registra la mayorfa de las precipitaciones. La ropografia empinada y el marco tectoni co dieron como resulrado casi 150 deslizamientos y flujos de escombro s qu e fueron identificados a rraves del exame n de foros aereas, escalas 1/50.000 y 1/70 .00 0. De los mo vimienros en masa registrado s, mas de 100 oc urrieron en la Co rdi llera Oriental y Calchaquenia, mas de 30 en la Puna, y algunos cua ntos en las Sie rras Suba nd inas/Sistema Santa Barbara. En cada una de las regio nes rnorfoestructurales se ubican grupos de grandes de rru mbes que deben haber sido causados por terremoros con una mag ni tu d (Richte r) de 5.0 0 mayor. La ubi cacion de esros rasgos distinriv os prove e la informacion necesari a para facilitar la identi ficacion de epiceritros de terremoros prehistoricos. La mayoria de los derrum bes localizados no indican riesgo alguno en la acrualidad. Mas bien, los sitios geologicos seleccionados ind ican lugares donde ocurr en pend ienres inestables que advierten sobre evenruales deslizamienros que pudieran ocurrir en esros lugares. La localizaci6n de esros sitios servira de gu{a para quienes planifican el uso del suelo y para evitar dafiosa obras civiles, accesos viales y, au n, la vida de las personas. Palabras clave: Salta - Escoip e - de rru m bes - flujos de escombros - deslizarnientos - sism os

I University of Ne braska.

Cenozo ic G eology o f the Ce ntral Andes of Argentina, 437 -453 / 437 Wayne

and a bri ef co mme n t about each slide and earth flow recogn ized is available and is archived in a Data Re­ -- ~ east ern slopes of the An des in northern Argen­ posito ry, along with maps sh owing the location of th e ~ >1 th e source areas for de bris flows as landslides and de bris flows recorded. - - ~ ~ rorrn of m ass was ting through out the Pleis­ "A is the m ovement of a m ass of rock , . _ tr.ese pr ocesses contin ue to take place regularly. earth, or debris d own a slope» (C ru den 1991 ), and th e ~ - ia t occur in unpopulated an d isolated sites are term includes virtu ally all form s ofrap id downslop e move­ s - :;': normal geo morphic processes, but those th at me nt of eart h mat erials. Many classifications of mass act om rnunities, highways, and railro ad lines, where movem ent p rocesses exist, but the ones in mo st exten­ ~-.:-:" can result in seri ous damage and economic losses sive use are th ose of Varn es (1978) and of C arson and , ove! 198 9; Schuster and Flemi ng 1986), can be con­ Kirkby (1972).T he classificat ion presented by Varnes is . ' de red geo logic ha zards. The debris flows, earth flows, the basis for the classificat ion adopted by C omm issio n a.. rock slid es are a resu lt of a co mbination of facto rs on Landslides of the International Association of Engi­ - at includes hig h topographic relief, rock eype, tectonic neering Geology (IAEG Com m ission on Landslides set ing, clim ate, and vege tation cove r (Polans ki 1966 ; 1990 ; UNESCO Working Party o n World Landslide Alo nso an d Wayn e 1992 ; Wayne and Alonso 1992 ). Inventory 1990; C ru den and Varnes 1996) . Two criteria Ericksen et al, (l 989) and Schuster et .11. (20 02) pointed for m the basis for this classification-type of mo vement our the po tential and actua l destructi ve nature of land­ and materi al involved. To the five eypes of movem ents, slides in the so uth ern Andes, along with exa m ples of falls, to pples, slides , spread s, and flows, one addi tional some of th e mo st damaging of dec ades. group exists for those complex slides in wh ich two or T he purp ose of th is st udy has been to prepa re an more kinds of movem ent have taken place. The mate­ invento ry of the recog nizable slope failures in the Prov­ rial is either rock or un con solidated materials (soi l in ince of Salta, Arg entina, as a first stage in the evaluation the eng ineering concept). C arson and Kir kb y (l972) of th e haza rd p otential of landsl ides in the province an d emphasized th e way the m ovement s are related w ith re­ as a co ntribution to th e Internation al Decade of H azard spec t £0 speed and quality of water involved . Red uction (Bra bb 1991, 1993). M ost of the project was Falls of de bris or rock take p lace on very steep to done by means of stereoscopic st ud y of airp hotos; al­ vertical slo pes, where the m aterial is unsupported, and though many of the landslid es an d deb ris flows that were it br eak s away, ge nera Jly alo ng an ex isting frac tu re. ident ified on th e airphot os were exa mi ned in the field . Topples are a kind of movement in which blocks of rock .Airphotos used were th ose taken for the Instituto C eo­ or debris fall over with th e base rem aining in place but gd.flco M ilirar ofArgentin a during th e 196 0 's. T he ph o­ th e top rota ting outward. Slides are movem ents in which ros of the part of th e province west of 65° 30'W are a an upper m ass of rock or debris m oves along a di screte cale of about 1/50,000 and wer e taken in 1966: those plane over a lower m ass that ha s rem aine d in place. 0 - th e eastern pa rt of the province are ab out 1/70, 000 Slid es m ay be eith er rot at ional (the slide plane spoon ­ an d we re taken in 196 3. The 1/ 50,000 scale airpho ros sha ped), or plan ar (slide plane a smooth surface). were ma de available by the Direcci6n de Mineda de la Planar slides take place where bedding or foliat ion rovincia de Salta. T he sm aller scale photos were ob ­ plane s dip ste ep ly and are unsupported. Eith er layers of tai ed fro m the offic es ofth e Insrituto Nacional de Tecn o­ weak rock, such as shale, or a zo ne of high er m oisture logia Agropecuaria (INTA) an d fro m th e D irecci 6n de content gen erally exists along th e failu re plane. La rge n ursos N aturales Ren ovables of the province. A ch art slides may take place spo ntaneously but m any are trig ­ - a, provides latitu de and longitude, airphoto number, gered by som e kin d of vib ration , suc h as seismic trem­ ors. The rocks involved gen era lly have been wea kened by . Ro tational slides, or slum ps, move along a cu rved ta reposi to ry plane of failure w ith little deformat ion. They are a co m­ . -r: tee readers will find (he following com plementary m on eype of slide in fine -grained sedim entary materials, • -­ - ' - on rhis chapter in the website of the Institute del parti cularly th ose th at are thi ck, massive, and un con­ ~ co ww. unsa.ed u.ar / incc): . esand debris flows identified in the Province solida ted . The sur face of th e upperm ost d ispl aced block of mos t slu m ps rotates bac k, forming a sh allow close d ca tio n mer me Institute C eografico M ilirar depression. Very commonly the material at the base of a or rotatio nal slide is de formed and becomes a flow

:: '- ", Ce-v -cl j,nde s of Argentino Moss wasting a s a ge ologic hazard in the Province of Sollo, Argentino of earth or rock. Some rotational slides become retro­ movement in the valley of rio Mendoza. Many slop es gressive, in that they begin at a steep slope and enlarge in on relative ly im permeable are blanketed with a direction opposite to the movement (Varnes 1978). loose weathered rock debris or so il, which beco mes Flows are movem ents in whic h materials are highly unstable on steep surfaces , particularly if moisture within defor med and move as a viscous fluid . M ost flows that the weat hered material red uces its . Rib involve unconsolida ted materials are readi ly recogniz­ and Liang (1978) pointed out that landslides can t ake able, may be either wet or dr y, and move at rates that place in almost any if slope , moisture content, ran ge fro m slow to very fast. Rock flow is generally a and vegetation cover are in the right combination. Aer ial very slow process that results in bul gin g or bending plas­ photographs at scales of 1:50,000 and smaller are ad­ tically, pro bably wit h many mi crofracrures, but without eq uate for recognition of large land slides, but are not mo vem ent along a distinct plane (Varnes 1978) suitable for the identification of the small landslides that Flows of unconsolidat ed ma terials are more read ily are likely to cause pro blems in eng ineeri ng projects. In recognized than rock flows because the material behaves this study, the airphotos were studied carefully in several more obviously like a fluid . Mud flows and debr is flows locations where roc kslides were known to exist along contain enough water to cause the -water mix­ . Because of th eir size and the photo scale, they ture to move as a slur ry, with sufficient density to carry were difficu lt to recognize even where they had been iden­ part icles ofvarious sizes in suspensio n (Pierson 1986; tified in the field. The smallest landsl ides recognizable in Pierson and Cos ta 1987). is used for those this stu dy are about 200 m in smallest dimension. flows of earth th at cont ain more than 50% san d, and Adequate aerial photograp hy to identify existing and -sized particles. D ebris flow is a ma terial that con­ potent ial areas of small but po tentially da maging land­ tains high percentage of coarse fragments, from pebbles slides should be of 1:10,000 or 1:5000 scale. T his study, to boulders. differ from debris flows in that wi th much smaller scale photos, was able to identify they move slowly. T hey, too, take place when a large mass areas ofpreviously unstable slopes, where additional land­ of rock and on a mo derate to steep slope becomes slide or debris-flow activ ity can be expec ted in the fu­ oversaturated and moves as a viscous mass downward. ture. It also loca tes a large number of existing slides that Vibrations, includ ing seismic activity, have triggered earth could be react ivated if they wer e to be dis tu rbed by con­ flows. So me earth flows undergo a single movement, str uc tion. then beco me stabilized; others are period ically active whenever the mo isture content within and along the base SIGNIFICANT MASS WASTI NG IN THE of the dis turbed mass becomes high enough to reduce MORPHOSTRUCTURAL REGIONS OF the ang le of internal . W here lateral extension of blocks, generally of frac­ tured rock, takes place on surfaces of only moderate Introduction incli nation, th e term spread (or lateral spread) is em ­ ployed (Varn es 197 8). These movem ents are most likely Slope movements take place with variable frequency to take place where thick bed s of firm roc k overlie a in five of the six major morphostrucrural regions in the layer tha t is more readily defor mable. Spreads that do Province of Salta, th e Pu na, the Cordillera Oriental, no t involve liquification of the underlying material may Calchaqueriia, the Sierr as Subandinas, an d the Santa requ ire an shock for mobilizat ion . Because Barbara System (Fig. 1). The sixth region, the Chaco most spreads invo lve more than one kind of movement, Plain , has little relief, and except for the collapse of bank they could be regarded as complex slides. material along rivers, mass movements are unlikely to Complex land slides are those in which more than take place or to present a hazard . T he geomorphic char­ one of the several kinds of movements are involved, acteristics of these regions have been described recently often in sequence as the mass continu es to move. Earth­ by Mon (1979), Igarzabal (1991), Marcuzzi et al. (1994), flow-slump, for exam ple, is a com mon com bination, with and Salfiry (2006). the slump taking place after an earrhflow failure on the Most slope movements involve water, and in north­ slope has removed support, or wit h the taking west Argentina they take place during the season ofgreat­ place as the lower part of the slump movem ent deforms. est precipit at ion , mid-Decem ber through mi d-March . Moisture content is a major contribut ing factor in D uri ng the remai nder of the year, preci pita tion rates nearl y all landslides. Moreiras (2004) pointed out that are much lower, and in the western part of the provinc e, precipitation is the principal triggering factor for slope conditio ns become arid. The Sierras Subandinas and

Cenozoic Geology of the Ce ntral Andes of Argentina / 439 Wayne

o r" the Co rdillera Oriental are covered main in a periglacial environment. trooical for est, becau se the prevailing easterly Mass-wa st ing features in the Puna include debris ;' :-.g warm Atlantic Ocean air masses inlan d flows, m ostly in the region underlain by the Puncoviscan a ate spring an d sum m er. Although they lose some Formation, lah ars that descend the slopes of volcano es ._-e rossing the lower Sierras Subandi nas ro th e (Alonso and Wayne 1992); with rotational rock slides/ - __, of it rem ains, The average annual precip ira­ earthflows the dominant type of mass movement in th e - a a .. ::1e Ci ty of Salta, altitude 1187 rn, was approxi­ rest of the region. In addition, fearu res of slope instabil­ - aze:: - 00 mm for the period 1934-1990 (Bianch i an d ity that ch aracterize regions of pe rmafro st are common ':==.e7. . 992); at Ca mpo Quijan o, alt itud e 1520 rn, where on the m ountain slopes. Among th e m ore dist in cti ve -:-0-0 em erges from th e C ordi llera, during the short are both active and inactive rock , stone stripes, ? e::od of reco rd available (1 97 3-1978) an average of and gelifluc tion lobes. These landform s are esp ecially ~ J - _ m m per year was registered . Most of the m oisture common in th e sierra de los Pasros Grandes and the is .0St, however, as the air m asses rise over the Cordi l­ sierra de C achi. The Puna is a large area that is sparsely .era, th e altitude of which exceed s 4000 m. Dry wind populated; except for the rail line , national highway 51 escend s the wes tern side of the Cordi llera, where desert from San An tonio de los C o bres ro C hil e, and pr ovin­ co ndirions exist. At Cachi in the Ca lcha q ui valley, fo r cial high wa ys 25 , 17 and 129 th at co n nect the small exam ple, precipitation averaged 163 mm/year for th e communities along them, th er e a re few places where period of reco rd, 1973-1 990. With few exception s, all geologic processes of mass wast ing can represent a haz­ was reco rded during the months of December, Febru­ ard to the population or to routes of communication . ary, and M arch . Unfortunately, no airphotos of the area west of GrW Intens e frost action at higher altitudes, especially and south of 25°S were availab le d ur ing the course of abo ve 4000 rn, breaks down expo sed rock , making small er this study, so no lan dslides were recorded for the south­ fragment s readil y available for downslope movements. A west quarter of th e Puna of Salta. few smal l rock glaciers, masses of frozen rock debris th at W est of the Cal chaqui valley only 33 landslides we re move slowly down slope, are present along the sierra de recogn izab le on airphotos (scale approximately 1/50,000). C hafii, and an inactive or stable one is in a cirque on Although th ey are distributed throughout the Puna, m ore the east side of cerro Malcante, Al though these features were noted in th e north part, where th e altitude is greater, present no d irect threat ro infrastructure or buildings, than elsewhere in the region (Fig. 1). Intensive frost ac­ rh ev can be a so urce of sedim en t for debris flows. tion is im po rta nt in shattering th e low grade phyllites and slates of the Puncoviscana Fo rmation into fragments P U NA in a silt and matrix that acc um ula tes on slopes and in swales where it can become so urce materials for de­ The h igh plateau (3500-3800 m) that makes up th e bris flows at times of intense pr ecip itation. Mass-w ast­ western pa rt of the Province of Salta (Fig. 1), the Puna, ing features tha t seem to be who lly per m afrost-rel ated is d istinguished by its arid climate and interior d rain­ include gelifluc tio n lobes, sto ne stri pes, and rock gla­ age. G eologically young, with man y features of Late Ter­ cie rs, are abunda nt in the northern part of th e Puna of riarv an d Q ua tern ary age. The n orthern part and the Salta , but because nearly all of them are rem o te fro m Chilean frontier are marked by volcanoes. Three of th ese, structur es, th ey we re not considered a risk. ocom pa, , and Antofalla, have been acti ve Most of the features recorded are roc k falls; some, re end)', and probably should be cons idered dormant at though, involve an entire slope and resemble a huge flow thi s time (C lapperro n 1993, p . 125 -130; de Silva 1989); of rock and soil. O ne of the se late ral sp read movements, man y o thers are extinct no w, but volcano es th ou ght ro in the Serra n ia del Barreal east of Sa n ta Rosa de los ;:> e ext in ct have been known ro become active again. Pasros G randes, covers a slo pe th at is 2000 m from crown The ma jor haz ards relat ed to volca noes are and to roe and m ore th an 7000 m across. G ull ies have : ;:o ~ ra accum ulations. Blo ck -fau lted ra ng es inro the north part of this mass, but th e so uth part is JO_n ed bv high-angle reverse fau lts t hat separate closed uneroded. Only an ea rt h q uake of m agn itude 5.0 or . s. m an y of th em the sites of salares at salt lak es, greater (Kee fer 1984), co uld ha ve tr igge red a mass move­ - ccerize mos t of the region. Although Paleo zoi c, ment so large. Four ot hers, all large rock falls th at surely zo i • an d C enozoic rocks are ptesent in the Puna, m ark the ep icenter of ano t he r sign ifica nt earthquake, .- L" per C enozoic age do m inate. T he volcanic are clustered toge ther near th e west side of the Puna

I en glaciated and the ir upper slop es re­ alo ng longirude 68 °W and between 24 °24'S and 25°00'5

_:-- -:-: eo ~ :) ! . e Ce ntral Andes of Argentina Moss wasting as a geologic hazard in the Pro vince 01Salta, Argentino

-,

26°

Figure 1. Map showing morphostrucru ral regions of northwestern Argentina (Salta and Jujuy). Black dots show the d istribution of landslides in the Provinc e of Salt a (because ofscale, not all landslides are shown) , and circles show volcanoes.

In latitude. Even though non e of the Puna landslides CORDILLERA ORIENTAL AND recognized and located through this airphoto study rep­ CALCHAQUENIA resents a risk in itself, their existence pro vides evidence not previously available on probable epicenters of large The Cordillera Oriental, a region of faulted rocks earthquakes in the region during the past few thousand that has great relief, borders the east side of the Puna years. north of the El Toro lineament. It, together with Calcha­ The Puna is arid, and landforms are altered very quenia, th e rnorphostructural region south of the El Toro slowly in dry regions. It is difficult, therefore, to evalu­ lineament, has the greatest number of landslides recog­ ate from an airphoto study of the morphology of any nized in this study. The rocks that form the crests of feature how long it may have existed. The fresh-looking both the Cordillera Oriental and Calchaquenia are slates, landslides in the Puna, therefore, could have form ed as ph yllites, and graywackes of th e Upper Prec amb rian­ recently as a few hundred to a few thousand years ago or Lower Cambrian (Turner and they may be several tens of thousands ofyears old . Those Mon 1979; Salfiry 20 06) . N orth of the El Toro linea­ with mu ted features may have taken place as long ago as ment the Puncoviscana Fo rmation is overlain by Or­ the last major glaciation (25,000-15,000 years B.P.). dovician mari ne sedi ments. Sou th of the El Toro linea­ ment, Ordovician rocks are missing and tho se of the Cretaceous-Paleogene Salta Group overlie the rnerarnor-

Cenozoic G ology of the Ce ntral Andes of Argentino / 441 Wayne

Figure 2, Small debris flows produced by an intense rainfall on -filled hollows in the headwarers of rio Escoipe,

phic rocks of the Puncoviscana Form ation, The eastern wer e treated as a single unit, the Cordillera Oriental, at edge of the Cordillera O riental is the eastwa rd sloping the time this study was made, they are dealt with to­ O cloyoco thrust . South of the £1 Toro lineament, gether in this report. the Sant a Barbara System and the Aconquija lineament Altogether, more than 100 landslides large enough mark the eastern and southern lim its of Calchaquenia to recognize on the airphoros used this study were iden­ (Salfiry 2006). tified . Ridge crests in the mounrains range from 5000 Tectonically folded and faulted , the low grade meta­ to 6000 m in altitude and the piedmont plain that ex­ morphic rocks of the Pun coviscana Formation in both tends eastward from the mountain front is about 1250m, the Cordillera Oriental and Calch aquenia weather readi ly This diffe rence produces a total relief of more than 37 00 in the frost-dominated clim ate that exists abo ve 3500 m in a distance of 12 to 14 km. Stream s that flow east­ m. Although rocks of the Puncoviscana Formation are ward from the crests of bo th the Cordillera Oriental the sourc e of most of the landslides and debris flows and Calchaquenia have high gradients, as much as 0.10 recogni zed in these two morphosrructural , or greater in their upper reaches. They have cut steep­ some of the mass movements in the Cordillera Oriental walled gorges in which local relief exceeds 2200 m in 5 involve O rdovician Santa Barbara Form at ion ; shales and km. Debris-covered slopes that stand at ang les of 30° rocks of the Salta G roup are involved in some of the are common. mass movements in Ca lchaquenia, These two , then, are he morphosrrucrural provinces that contain the great­ Debris Flows es number of landslides ident ified in thi s study as well as the grea test nu mber of potentially hazardous condi­ Most of the roc ks tha t form the upper slopes and . ' 0 resulting from landslides (Fig. 1), Because they crests of the Cordillera O riental and Calchaquenia are

:::,,- .:: : .:: .:: Ge og ; one Cen ral ,A. des of Arg entino r'v1os s wasting os a geo logic hozord in the Province o f Salta, Argentino slates, phyllites and graywackes of the Upper Precam ­ no rt heastern Uni ted States (Kochel 1987) . brian/Lower Cambrian Puncoviscana Formation and Years of higher than normal precipitati on in sum­ related igneous rocks (Salfity et al. 1998). These low mer (january and February) are those duri ng wh ich de­ grade metamorphic rocks have been folded and faulted; bris flows have caused signi ficant damage to roads, str uc­ thus the y are highly fractu red. In the fros t-dominated tures," and cu ltivated field s, and notable inconvenience climate above 3500 m. they weath er readily to ang ular to th e communities. For example, January 197 6, when roc k fragments in a matrix of silt and sand-sized par­ San Fernando in the Escoipe valley was destroyed, 20 7 ticles. This rock debris covers most of the slopes and mm were recorded for th at mo nt h at Cachi; Chicoana , moves slowly downward into swa les at the heads of ra­ on the eastern bo rder of Calchaquenia, recorded 3 13 vines, where it beco mes mobilized into d eb ris flows mm for the same month, more th an double the January du ring episodes of heavy precipitation in early summer. average for that station from 19 34 -1976. Two deeply Airphoto review and field ob servations indicate the ex­ entrenched valleys that serve as the main routes west­ istence of many coll uvium-filled ho llows in the higher ward through the Cordillera are most at risk from the parts of both the Cordillera Oriental and Calchaquenia hazard of debris flows: the quebrada del Toro (Igarzabal th at are underlain by the Punco viscana Formation. T hese 1971) and the quebrada de Escoipe (Igarzabal 1979; th ick acc um ulations that result from creep and solifluc­ Wayne 1993) (Fig. 1). tion of frost-shattered rock (Fig. 2) provide source ma­ The quebrada del To ro is the route through th e Co r­ ter ial for po tentially des truc tive de bris flows. di llera Oriental for both rou te 51 an d the railway from Several studies relat ing the amount and intensity of the Valle de Lerma an d the city of Salta ro the Puna and rain fall to the generation of debris flows have pointed Chile. The h ighway is closed each summer because of out that few debris flows develop unl ess the soil has be­ rock falls from th e steep cuts and debris flows th at come satura ted from rainfall during the previous week emerge from the sm all bu t steep valleys that have built or lon ger, and th at a threshold intensity gen erally m ust alluvial cones that the route cro sses. T he railroad is less be exceeded during a particular . The «th reshold» affected th an the h ighway, because it crosses most of intensity not ed by Neary an d Swift (1987) for the sou th­ the fans on bridges h igh enough to allow the passage of ern Appalachians in the U. S. was 125 mm in one day. s, an d chutes car ry debris over the railway Wieczorek (J 98 7) established the need for a minimum where it passes beneath the sm all steep water courses amount of previous rainfall (28 cm in sou thern Califor­ that drain the slopes of th e quebrada. nia). Before debris flows would take place and an inten­ Berween Ingeniero Maury and El Mollar, near th e sity-duration relationsh ip for sever e th at produce mouth of the quebrada del Toro, th e hig hway crosses a debris flows . Hauser (J 985) noted that a precipitation series of steep alluvia l co nes bu ilt by the streams that rate that exceeded 60 mm in 24 hours in a high prob­ drain southwestward into do Rosario. Downstream from ability ofde bris flows on the western slopes of the Andes the railroad bridge (Puente del Toro), route 5 1 is perched in central Chile. Churc h and M iles (1987) foun d th at along the northeast side of the quebra da. Only a few debris flows in British Columbia took place following small ravines flush across the road surface in this reach, varying amounts of rainfall, but they we re dealing wi th but the y do sometimes leave a cone of debris that must an area where hig h snowfall and th awing offrozen gro und be cleaned off to allow traffi c movement. Roc kfalls fro m were contributing facto rs. the cliffs of highly fractured me tamorphic roc ks that Alth ough large debris flows that inco rpo rate thou ­ stand above th e road, h owever, are a detriment to traf­ of cubic meters of debris are both spectacular and fic movement. especial ly destr uctive, most of them take place at decad e­ From EI Mollar to El Alisal the highway crosses four long int ervals or longer. An nually th ough , smaller masses steep alluvial cones that undoubtedly cover the route with of debris become detached during sto rm s to become a debris that m ust be rem oved regul arly. Hyperconcentrated dense fluid th at follows a ch an nel downstream. St udi es flow carried by these channels also erodes the downstream in Cal iforn ia (D ietr ich et al. 1986; Reneau an d Dietrich edge of the roa d sur face, whi ch m ust then be rebuilt. 1987) and in N ew Zealand (Crozier er al. 199 0) have The h ighway cross es the river to the west sid e of the em phasized the significance of accu m u lation of collu­ quebrada about 500 m upstream from the junction with vium in upl and swales for the initiation of debris flows. quebrada de C ap illas, and for several kilometers it is on T he soil/rock interface, where pore pressure is grea test, a bench cut into the valley wall. Through much of this was the mo st frequently observed detachment plane in reach the metamorphic rock s appear to high ly fractured, deb ris flows stud ied in the Appalachian of as though this were a zone whe re faulting had taken

Cenozoic Geology of the Ce ntral Andes of Argentino / 44 3 Wayne

~ ae roa surface is nar row and sma ll cones of from their characteristics whether, at that parti cular place, , ::~ _mulare on it at the base of the cuts . Through deposition rook place at the head or tail of the flow. reac . the largest streams that bring flows of debris Dietrich and others (19 86) wo rked out a relation­ tne uebrada are on the east side; the railway crosses ship betwee n undrained hollow length and gradient for _ 0 :1 b ridges. Swales in th e headwater areas of some holl ows that had failed, and th ey arrived at a regression ont ain accumulatio ns of loose debris weat h­ equation for hollows in southern California of L = 87 .75 ' ~ - ~ rrorn th e rocks in the slopes above them that is 0 67, where L = length (rn) and S = slope (rn/ rn) . O ther -ce material for th e gene ration of future dense flows studies have suggested tha t the great est potential dam age c _;- :ng times of un usually high precipitation. from hign flow velocity is in second-order streams fed by Two large ancient landslides near ln geni ero M aury many firsr-order streams with undrained hollows. Jack­ arn med the valley and produced lakes. Freshwater snai ls son et al.(1987) plotted basin ruggedn ess against fan slope. ~ overed from the lake sed iments and dated by radio­ And found a relationship that helps distinguish between -ar bon indicate that th e upper and larger slide took place fluvial and debris-flow fans. Basin ru ggedness (R) is a ) ) more than 26 ,000 years B.P. an d the lower one more function of basin height (H b and basin area (Ab in th e 0 m an 30 ,000 years (Trauth and Strecker 1999; foll owing eq ua tion: H A · 5. Flu vial fan s have a B.P. Trauth R = b b er al. 20 03). slop e of less than 2.5° and R of <0.3; fans wit h a major Debris flows in th e que brada de Escoipe originate debris-flow com ponent nave slopes of more than 4° and in steep colluvium-frlled hollows (Wayne 1993 ) th at be­ basins with R values >0.25 to 0.3. For comparison, the come gullied during storms (Fig. 2), part icularly after lower par t of the fan of arro yo del Media no rth of Jujuy, th e material has been saturated by several weeks of low a debris-flow fan, has a 4° slope and the upper part has intensity rainfall. Where im permeable rock lies ben eat h a slop e of 9° (Gonzalez Diaz and Fauque 1987). a th ick accumulation of colluvium, such precipitation In addition to the debris flows th at originate on the raises th e seasonal perched water table with in the se sedi­ higner slopes of the Cordillera Oriental, small but pote n­ ments, causing them to lose shear strength and become tially vety destructive soil slips on the lower eastern slopes a de nse fluid . of the range take place from time to time during episodes A low clay content is typical of th e debris weath­ of unu sually high precipitation. Debris flows of this kind , ered from the siliceous metasedime nts of the Puncovis­ such as the on e that dam aged Chicoan a in February cana For mation in the Cordillera O rient al and Cal cha­ (Amengual 1992), occur as a result of precipitation tha t qu enia. Dry, these colluvia l materials nave a high effec­ acco m pa nies the orographic rise of moi st Atlantic air. tive angle of intern al friction (0) ; saturated, though, 0 is Tree -covered slopes from 10° to 20° that have mo de rate likely to be as low as half of the unsat urated value, an d soil cover over impermeable rock are most suscep tible may be less than the surface slope of the ma terials. Cro­ to thi s kind of mass movement, in whi ch masses ofsatu ­ zier et al. (I990) have de term ined for N ew Zealand a rated earth , rocks, and trees flush downslope on to allu­ relationship between slope angle (in deg rees) and th e vial fans at the base of the m ountain front. critical thi ckness in meters of co llu vial frll in swales, M ajo r roads th at follow valleys, route 51 along que­ both with an d without forest cover. Nearly all the sur­ brada del Taro, route 33 along qu eb rada de Escoipe , races in these two rno rphostructural regions where large route 68 from Salta to alon g rio de las Co nchas debris flows origi na te are treeless, so if th e relat ion ship and route 40 northward from Cafayate through th e Ca l­ th ey determ ined should hol d, a colluvial accumulation chaqui valley, are affected dur ing each rainstorm by man y less th an two meters in thic kness in swale slopes of 25 °­ small debris flows an d/or hyperconcentrated flows that 30° wou ld be sufficien t ro be debris-flow source ma te­ emerge fro m the ravines that descend the slop es along rial whe n it becomes saturated. th ese valleys. At the se times acc umulations of stream Id entificatio n o f source areas for deb ris flows in­ sedi ment and occasionally debris-flow co nes bu ry the vokes the mapping of steep colluvium-filled ho llows at road beneath deposits from a few centimeters to more J1e heads of first ord er streams, the recognition of chan ­ than a me ter thick tha t block traffic until th ey can be n is through which rapidly moving surges of debris will scrap ed away. On un surfa ced roads an d -sur faced _ -. and the delineation of the deposition zones, wh ere roads with fords at the strea m crossings , the hypercon­ oci ties are lower bu t objects can become bu ried (H ungr cen trared flow such streams prod uce some times erodes . 19 " ). \XThere debris-flow accu m ulate the scream bed at the ford to make it im passable . Grad­ ·ial fans. it is ofte n possible to distinguish flows ing equi pment is sta tioned nearby whe re such flows make e lirnen r record (Wayne 1990) and determine fords impassable so th at traffic can be maintained.

= e "' : : ~ :: Geo 9 ! ·'le Ce ntrol Andes of Argen tino Mass wasting as a geologic hazard in the Province of Salta, Argentina

-, .."...... " , , , ,, , , ' . , _ 1 _ ~(. , ... - .. ~ " ~, ~ ~:; - -t,' ~ ~ # ",''-......

,,~ , . f, ...... ~\

" , . "\, ,,-... , '-':::;. .... , ,

'/c , /- --'- (' J:" -"'/-- - ...... "

o 2km I !

Figure 3. Map of the basin of the Quebrada de Escoipe, show ing the large nu m ber of mass wasting features in the basin. Specific mass wasting features ind icated by lett ers: A, D ebris flow 19 January 1976; destroyed San Ferna ndo de Esco ipe . B, Active slump/ean hflow; cuts highw ay that climbs C uesta del Obispo below Piedra de Molino and requ ires constant mai nt enance during rainy season. C, Active slump/eanhflow at head of arroyo Ma1cante. D , T hree ear thflow sheets on headwater slopes of arroyo Malcanre. E, Stab le slump/ rockslide trenched by arro yo Ma rai; san dstone of C arahuasi For mati on an d shal e of Santa Barbara Subgroup dammed d o Escoipe, lake now drained . F, Large rock block slid e, 5000 m by 3000 m, Carahuasi Sandsto ne slid over cru shed Santa Barbara Subgroup shales . G, Stable slum p/ rockslide at Las Zanjas; ponds on top su rface. H , Recen t slump/ roc kslide. Carahuasi Formation over Santa Barbara shales; flar surfaces between ridges are farmed. I, SIum p/rockslide at San M artin ranch, featu res muted by erosio n. J, Relict rock in sourheasr-rrend ing cirque of cerro Mal canre.

Cenozoic Geology of the Central Andes of Argentino / 445 Wayne

Figure 4. Slump blocks at the top of the active slump/earrhflow that is crossed by rhe Chicoana-Cachi highway.

M ore than 10 translational rock spreads or flow slides Earthflows have taken place on slopes of 10°-15 ° un derlain by sand­ stone beds of the Tertiary Jujuy Sub group in sierra de Two large activ e ear th flows are in th e headwaters Vaqueros, between 20 and 30 km directly north of the of rio Escoipe, where st ructurally shattered limes tone city ofSalta.The largest of these, 3 km north ofLa Caldera, along the thrust-fault zone beneath the Pu ncoviscana is a chaot ically-tumbled sou th- facing slope, 1500 m from Formation has beco me saturated an d has flowed, gla­ headscarp to toe and 30 00 m across. A second one, nearly cier-like, down stee p ravines at th e west end ofthe C uesta as large, covers a south-facing slope abou t 1000 m farther del Obispo (Polanski 196 6; Igarzab al 1979; Wayne 1993). north. Eight additional sim ilar, though smaller, slides are The slum p blocks of the large r of these are crosse d re­ withi n a dista nce of 10 km to the north and east of these pea ted ly by th e Chicoana-Cachi highway (Figs. 3 and two. All are now completely tree -covered; their surface ), and heavy equipme nt is maintained in the reach to features, relatively unmodified by , suggest that keep the road traversabl e. To relocate th e road wo uld be all may have taken place about the same time, probably impractical, tho ugh, because any other route tha t rises within th e past few th ousand yea rs. T hese slopes ordi ­ to th e to p of [he C uesta del Obispo probably would narily should be stable, so the existence ofso many large di stu rb the land and result in addi tional slope failure. flow-slides of th is kind suggests that this area also may The smal ler of these active flows occupies a similar po­ have been nea r th e ep icenter of a preh isto ric earthq uake sicion on the op posite side of the Cuesta del O bispo. of 5.0 or greater magnitud e. mall ear hflows are ab undant on slopes of abou t 20° or g-ea-er abo ve 3000 m whe re the Puncoviscana Forma- Rockfa lls and Rockslides CIO resent .

C e~oz c eo og 0 1 he Centra l Andes of Arg entino I\;\OSS wasting as a geologic hozord in the Province of Salta, Arge ntino

Two areas of massive exist along do de las Planar rock slides, in which dipping blocks of sedi­ Conchas between Alemania and Cafayate (Frenguelli mentary rocks have slid downward along bedding sur­ 1936). Both blocked the valley long enough for strati­ faces, are especially notable along the quebrada de Es­ fled silt and clay to accumulate in the lake that formed coipe, where eastward-dipping sedimentary rocks have upstream from the dam. The larger and older of these moved downslope as translational rock slides into the slope failures is in the south end of the valley, about 25 valley (Wayne 1993). The largest of these slides, mapped km north of Cafayate. In this location huge masses of originally as a thrust fault (Ruiz Huidobro 1960), ex­ rock evidently fell from both the east and south faces of tends from do Escoipe on the south to arroyo Malcante cerro Zorrito, at the south end ofsierra del Leon Muerto. on the north, a distance of 5000 m (Fig. 3). It is about Composed of thick bedded Lower Tertiary conglomer­ 3000m from the mountain slope to its disral end along ate, the masses came to rest at Casa de los Loros and La the Escoipe river; and probably is between 50 and 100 Yesera (Alonso and Wayne 1992). A study by Gallardo m thick, thus it incorporates between 0.75 and 1.5 x (1988) indicates that three such movements must have 109m of rock. This mass of chaotic rock, mostly sand­ taken place. The earliest one dammed the valley and stone, has been further cut by at least two younger slides, created a deep lake in which many tens of meters of both of which moved as slump blocks. The larger one silty clay accumulated. Mollusks recovered from these rises above the village of Las Zanjas, and, although it lake sediments, dated by 14C, indicate an age of 25,820 still has some ponds on its upper surface, the small lake and 29,790 years ago (Trauth et al. 2000; Bookhagen et on the reversed surface of the dropped block has been al. 2001). The last one, which contains huge blocks of drained. This slide probably is only a few thousand years conglomerate from cerro El Zorrito, buried the lake old. The smaller slump just east of the village shows very sediments at La Yesera.The second and younger of these fresh topographic features and may be little older than a failures is a large mass of crumbled and crushed sand­ few hundred years. stone that fell from the cliffs 2,5 km south of Alemania Two other large translational rock slides are present (Ruiz Huidobro 1949; Wayne 1999). This rockfall pro­ in the Escoipe valley. One, at Finca San Martin, is rela­ duced a dam 2000 m long that blocked do de las Conchas tively old and its form has been muted by erosion. The long enough for several meters of stratifled silt and clay other, at arroyo Maray, is so young that a fracture pat­ to accumulate in a lake that was at least 9 km long. Both tern across the surface, formed as the block came to of these huge surely were generated by earth­ rest, is still very evident (Wayne 1993). This slide, which quakes, the first took place during the late Pleistocene dammed the valley briefly, incorporated about 50 x 106 (Trauth et al. 2000), the second much more recently. It m of rock, and may have occurred at the same time as has been dated at about 5000 years ago (Wayne 1999; the slump above Las Zanjas. At this time, the river flows Trauth er al. 2000). The debris that blocked the river at through a narrow gorge around the toe of the slide. both sites filled the valley and spread both upstream and Rock slides of this magnitude are unlikely to have downstream; thus they were Type III ofCosta and Schuster taken place without some triggering event, although weath­ (1988). When the outlet to landslide-dam lakes of these ering and high moisture content along the slide plane surely dimensions is breached by erosion, the lake generally weakened the slide area. Other geomorphic evidence sug­ drains rapidly, producing carastrophic flooding down­ gests that the cumbre del Obispo has continued to rise in stream (Costa and Schuster 1988). the past 10,000-15,000 years, undoubtedly generating Rockfalls and rockslides can take place at anytime earthquakes. Keefer (1984, 1994) pointed out that earth­ along the road cuts that follow rivers into the mountains quakes of magnitude less than 5.0 evidently have not but are especially common during the rainy season. The caused rock slides in historic time, so it seems reason­ steep road cuts along quebrada del Toro are the sites of able to conclude that the Escoipe valley may have been frequent rockfalls. Several places along roure 68 between the epicenter of at least three earthquakes of magnitude Alemania and Cafayate have been partially blocked by 5.0 or greater in the past 10,000 years. small slides. One at Alemania that has kept the highway Small slump slides can be found along the steep surface broken results from unsupported dip-slope beds slopes of nearly all of the valleys that are eroded into the ofYacoraite Formation in the cut made for the highway Puncoviscana Formation. The surfaces of those that are and from the fracturing of rock along a fault that runs low on the slopes and accessible provide relatively level through the exposure (Balderrana 1989). Small rockfalls sites for small cultivated fields, are common along route 9 where it winds from Abra de One additional large area of landslide activity is at la Sierra to the border with Jujuy. the north end ofsierra Santa Victoria, and involves sedi-

Cenozo ic Geology of the Central Andes of Arqentino / 44 7 Wayne

Figure -5. Retrogressive slump block s along a stream flowin g th rough rocks ofthe Santa Victo ­ ria Group, about 15 km north of the Arge nt ina­ border.

me rits of I he Ordovician Santa Victori a Group. Mul­ Soi l slips, some of which have generated small de­ tiple reuogressive rotational slides have broken an area bris flows, are common in the headwater slopes of si­ 2000 m wide along quebrada Tres Lagun as that exten ds erra de Vaqueros during episodes of precipitation that r oo m east from the stream. An even larger area of is heavier than normal. Within few decades, howe ver, retrogressive slumps or rotational slides begins about 7 th e scars th ey produce become muted and vegetati on­ krn no rth of the frontier with Bolivia (Fig. 5). The large covered and may be difficult to identify. Few show up nu mber of m ultiple slumps in this slide complex m ust on the airphotos that were taken in 1966, bur at this have been started by earthqu ake vibrations. The highest time (1994), one can see many fresh scarps on the slopes, arps in th e com plex are somewhat rounded, others wh ere colluvial debris or weakened rock has broken away are more sharp, suggesting tha t at least two episode s of and slid dow nwa rd recen tly. overnenr have tak en place. T he overall freshness of Construction of roads and residenc es on the lower . eir appearance, however, suggests that they took place slopes of cerro San Bernardo in Sa lta has resul ted in • e t ... perhaps no more than a few hund red years ago. small slides, particularly where the activity has involved

~ - ~ ? : G e::J og 0 : 'he Cen rol Andes of Argentino A10ss wasting as a geologic hazard in the Province 01 Salta, Argentino steeply dipping beds of the Ordovician rocks (Sastre streams that drain these mountains are evidence that 1999). No large scale slides have taken place, but the debris flows have occurred. Soil slips, scarcely detect­ many small movements pose a risk to future construc­ able on photos of the scale available, take place during tion on these slopes. times of high precipitation, producing small debris flows that inundate segments of roads and cultivated fields SIERRAS SUBANDINAS AND SANTh along their paths. BARBARA SYSTEM Mass-wasting processes on the slopes in the Carapa­ ri-ltiyuro river basin north ofTartagal, on the eastern flank Recent studies (Kley and Monaldi 1999,2002) show of the Serrania de Itau near the Bolivian frontier, filled that the Sierras Subandinas are structurally distinct from the reservoir along the river with sediment much faster the Santa Barbara System, which was described by Rolleri than had been expected (Amengual 1991). In the same (975). Nevertheless, I have grouped the two together region, the severe storms of March 1984 produced dam­ for discussion of landslides. aging mass wasting processes on the eastern slopes and Only a few landslides were detected in the course the piedmont of the sierra de Aguarague (GonzaIez Diaz ofan airphoro survey ofthe Sierras Subandinas and Santa and Malagnino 1990). and debris flows gener­ Barbara System in the Province of Salta. The only air­ ated by this and other intense rainfalls of the early 1980's photos available for this region are relatively small scale extended fans across the railroad and highway at General (about 1:70,000); as Rib and Liang (978) point out, Mosconi and approached the power plant ofTartagal. large landslides may be recognizable at this scale, but small landslides, such as the one described near Rosario ACTIVE FAUlTS de la Frontera described by Abascal and Gonzalez (2006) are difficult to detect on photos at scales smaller than Earthquakes of (Richter) magnitude 5.0 and greater 1:10,000. Some of the largest landslides observed on have triggered landslides in many parts of the world, but the airphotos used are on the slopes of cerro Ceibal, few historic slides have been recorded for earthquakes along the Salta-Jujuy provincial boundary in sierra de of lesser magnitude (Keefer 1984, 1994). Completely Centinela (Fig. 1). The largest of a group of 3 is a slump­ sound rock is unlikely to be disturbed by an earthquake, earth flow 1700 m across and 2000 m from crown to but weathered rock, rock with higher than normal mois­ toe. The second largest in this group is on the Jujuy side ture content, and rock that contains significant struc­ of the same peak. Another large slump-earthHow about tural zones or planes of weakness will be seriously af­ 1800 m across and more than 3000 m from crown to fected. Historic earthquakes in the Province of Salta toe is 10 km SSE of the junction of rio EI Tunel with rio include some near the city of Salta and in a seismic belt jurarnento, in sierra de . Lake sediments in that runs through the Santa Barbara System and the Si­ the displaced block beneath the main scarp are still erras Subandinas from south of Rosario de la Frontera undissected but the stream draining from that surface through Meran and Oran to the north limit of the prov­ has eroded deeply into the earrhflow beneath it. A sec­ ince (Marcuzzi et al. 1994). Two factors of concern need ond slide just east of the large slump-earthHow resembles to be considered with respect to earthquakes in this zone. a lateral spread. The first is the existence of recently active faults, some The succession of anticlines and synclines in the of which were observed in the airphoto study of land­ Sierras Subandinas has resulted in many rock escarp­ slides; the second is the presence in the Sierras Suban­ ments. Rock falls from the cliffs undoubtedly take place dinas and the east of the Cordillera Oriental and Cal­ regularly, producing a talus of below the fall face, chaquenia of basins filled with unconsolidated sediments although few talus accumulations were recognizable on of Quaternary age. the small scale airphotos, Sierra Malz Gordo is an anti­ Amos and others (981) mentioned 3 faults in the clinal mountain range, with thick-bedded sandstone sup­ Province of Salta, citing maps by Ruiz Huidobro 0960, porting the crest and upper slopes. The sandstone has 1968) as the source. A fault east of cerro San Miguel formed cliffs at the top of steep-walled canyons eroded near Cerrillos and 15 km south of Salta and a second by the small streams that hear on· the crest of the range. one 45 km east of Salta (Los Nogales fault) cut Quater­ All the Sierras Subandinas are highly dissected. Most nary alluvial sediments; thus they were presumed to be of the slopes that dominate them are forested, so small active. The third, along arroyo La Yesera on the west mass-wasting features are obscured by vegetation. Nev­ side of cerro Agua de Castilla, 20 km southwest of Chi­ ertheless, stee p fans that emerge from the mouths of coana, cuts sediments of alluvial fans.

Cenozoic G eology of the Central Andes of Argentina / 449 Wayne

Fresh fau lt sca rps offset the lower pan of upper and s in 1986 (C hayle and Wayne 1995). Where a Pleistocene/ H olocene alluv ial fans on both sides of th e raised roadbed is on an above the valley sierra de La Candelaria south of Rosar de la Frontera. floo r adequate drai nage must be provided beneath it to The fau lt scarp along the west side is 19 ,5 km lo ng an d avoi d ponding on the up slope side. m ikes about N 7 0 E from 10 km northeast of La Ca n­ N earl y all non-volcanic debris flows originate in dela ria ro 22 km so uth of Rosario de la Frontera . This steep colluvium -filled hollows at the heads of first-order scarp is very fresh looking an d th e st reams emerging streams; th erefore , repeated surveys by both large scale from the m ountains have eroded tren ches through the air photograp hy an d field che cking of these sites in the up lifted lower pan of the fan . The fault scarp along the basins of the stream most frequently affec ted by debris east side of the sierra de La C andelaria also has offset flows would provide useful for predict ions. N o hazards upward the lower part of the fans, bu t the most recent exist unless comm unities or strucrures have been built movement on it took place lon ger ago . The fault is di ffi­ alon g the ro utes foll owed by debris flows, so these ki nds cult to tra ce across the Holocene fan surfaces, but is of monitoring methods nee d not be em ployed except evide nt where remnants of an older fan surface rem ain. where something can be dam ageJ. Canad ian eng ineer­ Three faults strik e N 45 °E cross th e alluvial fans along ing geologists have co m piled a wide range of defensive the southeast side of rio Guachipas, northeast of the vil­ me asures to mitigate damage from debris flows (H ungr lage of Guach ipas (Way ne 1999, Fig. 3) . Two of these et al. 1987 ; Eisbac her and C lague 1984). faults bound the margin of a horst that has risen across Two act ive earthflows were recognized in th is study; the distal part of the bajada. T he thi rd is nearly parallel both are on th e slopes of the C uesta del Obispo, but with them but is a very low scarp higher on the fan that only one crosse d repeat edl y by route 33 cons titut es a can be traced across the Holocene sur face. An other zone hazard. This eanhflow is stable during the dry months of Q uaternary faulting mar ked by a belt of low h ills un­ bu t moves slowly in summer. Ra infall saturates th e gravel derl ain by Upper Tertiary an d Lower Quatern ary sedi ­ in the slump ed sur face at th e to p of th e earr hflow and ments strikes about N40° E across the middle of the allu­ the water is transmitted downward th rough the perme­ vial fans from near C oronel M oldes to west of La Vifia. abl e material to the highl y br oken sed imentary rocks Up per Quaternary sediments have not been disturbed by beneath. D rainage of water fro m the surface of the up­ these faults, though, so they may no lon ger be active. per disp laced block wo uld reduce the amount available

(0 infiltrat e the flow, and em placeme nt of ho rizontal CONCLUSIONS conduits in the flow ing mass beneath the top may re­ du ce the wa ter co nten t to slow the flowage sign ificantly, Rapid slope failures have caused significa nt da m­ perhaps even stabilize it, thus reducing the annual costs age to properry and to highways in the Province of Salt a. of maintenance of the road (G edney and Weber 1978). Rout es of comm u nica tion - roads and railroads- must Effective methods to reduce rockfal l damage to high ­ be located along lines oflow to moderate gradient; th ere­ ways include use ofwire mesh (Pireau and Peckover 1978, fore, those that provide pathways into and th rou gh the p 2 19-220), benches, and ditches beneath the vertical Cord illera O riental and Calcha q ue nia follow valleys. slope. Space is not available for relocat ion of the highway Because many of th e valleys th at em erge from the rising along quebrada del Toro where rockfall is a hazard, and mount ain s are narrow with steep valley sides, the poten­ space is inadeq uate at th is time to co nstruct a ditch be­ tial for slope failures that block or dest roy segme nts of tween the roadbed an d the vertical rockwall. Benching the routes in them is always pr esen t. The only way (0 may be possible to reduce the height of the verti cal face avoid major da mage from large debris flows that follow above the road surface, but a wire mesh may be the least th e mai n channel is to bu ild a railroad or roa d h igh expens ive way to prevent rockfalls on to the sur face. enough to be com pletely clear of a flowing m ass of de­ Most of the rock slides and slumps identified in bris in th ose valleys, such as Escoi pe and Toro, where thi s study are now stable and probably will not become th e upper part of th e basin is un de rlain by large am ounts rea ct ivated un less co ns truct ion activity should make of loose rock de bris weathered from slates and phyllites them unstable again. T he great est adva ntage to thi s part of the Puncovisca na Forma tio n. This was done along of the inventory is to recognize thei r existence and the route 33 following the destruction of San Fernando de conditions th at probably caused the slope failure. By Es oipe in 1976 . Sim ilar reconstruc tion was done for ide nt ifyin g the locat ing the sites of past landslides, a both the hig hway and railroad along the rio G rande valley fou ndation is established fo r de termi ning wh ere addi­ if: the province of Ju juy followi ng disastrous debris flows tional geotechnical study is called for if construction is

r:e'1 zo c Geo 09 , of he Central And es of Arge ntina Moss wasting as a geologic hazard in the Province of Salta, Argentino planned near rhem . A major concern is the failu re to Balderrama, CA., 1989, Estudio geologico-gcorecnico aplicado a recognize older slides and, in the course of construction esrabilidad de raludes: ruta nacional no 68-km 79.5 [Tesis work, reactivati ng them. M eth ods have been developed Profesional]: Salta, Universidad Nacional de Salta, Facul­ tad de Cienc ias Naturales, 99 p. to prevent reactivat ion of slides, provided they are rec­ Bianch i, A.R., and Yanez, CE., 1992, Las precipiraciones en el ognized (Ge dney and Weber 1978; Leighton 1966). The noroeste Argentina: Salra, Inst itute Nacional de Tecnolo­ identificat ion of clusters of large landslides in thi s in­ giaAgropecuaria, Estaciori Experimental Agropecuaria Salta, ventory provides additional data on probable epicenters 50 p. of high (»5.0) magnitude seism ic events that have taken Bookhagen , B., Haselron, K., and Trauth, M.H ., 200 I, Hydro­ logical modeling of a Pleistocene landslide-dammed lake in place in the province d uring the past few th ousand years. the Santa Maria Basin, NW Argentina: Paleogeography, Paleoclimaro logy, Paleoecology, v. 169, p. 113-127. ACKN OWLED GEMEN TS Brabb, E.E., 1991, The world landslide probl em: Episodes, v.14, no. 1, p. 52-61. Financial suppOrt for the field work that was done in Brabb, E.E., 1993 , Pro posal for worldwide landslide hazard maps, preparation of this report was provided by the National in Novosad, S., and Wagner, P., eds., Landslides, Inte rna­ tional Conference and Field Workshop on Landslides, 7tn, Geographic Socie ty (Grant No. 34 38-86) and by the Proceedings, p. 15-24. Fulbright C om mission (Council for the International Carson , M.A., and Kirkby, M.J., 1972, Hillslope form and pro­ Exchange of Scholars), Am erican Republics Research cess: Cambridge, Cambridge University Press, 475 p. Program (1993-4). An administrative leave from my teach­ Cha yle, w. ,and Wayne, \X1.J., 1995, Impact of erosion, mass wast­ ing responsibil ities at the University of Nebraska allowed ing, and sedimentation on human activiti es in the Rio me to und ertake the 1987 work. Ricardo N . Alonso, Gra nde basin, , Argentina: Environm enrral and Engineering Geoscience, v. 1, p. 403-4 16. National University ofSalta, provided helpful background C hurch, M., and Mi les, M.j., 1987, Meteoro logical antecedents and introduced me to the stratigraphic units exposed in to debris flow is southwestern British Co lumbia: some case the province. D r. Jose A. Salfiry helped obtain maps of studies, in Cosra, J.E., and Wieszorek, G.E , eds., Debris the province, both topographi c and geologic.The Di recci6n flowsl Avalanches: Process, Recognition, and Mitigation: de M inerfa de la Provincia de Salta, the lnstiruto N acional GeologicalSociety ofAmerica, Reviews in Engineering Geol­ de Tecnologfa (INTA), and the Di recci6n de Recu rsos ogy, v. 7, p. 63-79. Clapperron , C , 1993, Qua ternary geology and geomorphology of N atu rales Renovables of the province permitted me to : Amsterdam, Elsevier,779 p. borrow stereo coverage of air ph otos from their files. My Costa, J.E., and Schuster, R.L., 1988, The formation and failure of wife, Naomi L. Wayne was my field assistant and typist natur al dams: Geological Society of America Bulletin. v. throughout all ph ases of the project. 100, p. [054 -1068. Crozier, M.J., Vaughan , E.E., and Tippett, J.M ., 1990, Relative instability of colluvium-filled bedrock depressions: Earth REFEREN CES CITED Surface Processes and Landforms, v. 15, p. 329-339. C ruden, D.M., 1991, A simple definition of a landslide: Interna­ Abascal, L. del v. , and Go nzalez Bonorino , G., 2006 , Kinematics tional Association of Engineering Geology, v. 43, 27-29. of a translarional/rorational landslidc, central Andes, north ­ C ruden, D.M., and Varnes, D.J., 1996, Landslide types and pro­ western Argent ina: Environm ental and Engineering Geo l­ cesses, in Turner, A.K., and Shuster, R.j., eds., Landslides, ogy, v. 12, no. 4, p. 369-376 . investigation and mitigation: Transportation Research Board, Alonso, R.N ., and Wayne, w.J., 1992, Riesgos geol6gicos en el National Research Coun cil, Special Report 247, p. 36-90. none argentino, in Resurnenes y Programas, Congreso Geo­ de Silva, S.L., 1989, -Puna volcanic complex of the cen­ 16gico Boliviano, l Orh, : La Paz, Sociedad Geo16gica rral Andes: Geology, v, 17, P: 112-1 106. Boliviana, Boletin , v. 27, p, 213-21 6. Dietrich, W.E., Wilson, C J., and Reneau, S.L., 1986, Holl ows, Amengual, R.E., 199 1, Fen6meno s de rem ocio ri en masa en la colluvium , and landslides in soil-manrled landscapes, in cuenca del rio Caraparf-Iriyuro: Revisra de Geologia Apli­ Abrahams, A.D" ed. Hillslope Processes: Binghamton Sym­ cada a la Ingenierla y al Arnbienre , Buenos Aires, Asocia­ posium Series in Geomorphology, Winchesrer, MA, Allen cion Argenti na de Geologia Aplicada a la Ingenieria, v. 6, p. and Unwin, Inc" v. 16, p. 36 1-388. 94-102. Eisbacher, G,H ., and Clague, J,J., 1984, Destructive mass move­ Amengual, R.E., 1992, Esrudio de las avalanchas de derriros (vol­ ments in high moun tains: hazard and managem ent: Geo­ canes de barro) en los alrededo res de la localidad de Chico ­ logical Survey of Canada, Paper 84- 16, 230 p. ana: Salta, Adrninistracion General de Aguas de Salta, 25 Ericksen, G.E., Ramirez, C F., Concha, J.E, Tisnado, G., and p., map, 50 phoros (unpublished). Urquidi , B.F., 1989, Landslide hazards in the cent ral and Amos, A., Caligari, R., and Siches, C, 1981, Las fallas activas de la southern Andes, in Brabb, E.E., and Harrod, B.L., eds., Republica Argentina, in Aetas, Congreso GeologicoArgen­ Landslides: extent and economic significance: Rotterd am, tino, Sth, San Luis: Buenos Aires, Asociacion Geologica Balkerna, p. 111-117. Argentina, v. 2, p. 233-242. Frenguelli, J., 1936, Invesrigaciones geologicas en la zona saltefia

Ce no zo G eo logy of the Centra l Andes of Arge ntino / 45 1 Wayne

ce va.ie d Santa Maria: La Plata, O bra del C incuenrena rio and Mitigation: Geo logical Society ofAmerica, Reviews in -'e. Museo de la Plata, v, 2, 572 p. Engineering Geology, v, 7, p. 15-12 4. G '-..:;':co. E. E. 1988, Geologia del Cuarernario en la confluencia Keefer, O .K., 1984, Landslides caused by earrhq uakes: Geological de los rios Calchaquf y Santa Maria (Salta): Revista de la Society ofAme rica Bulletin, v. 95 , p. 406-42 1. Asociac ion G eologica Argentina, v. 43 , p. 43 5-444. Keefer, D .K.••1994, T he imporrance of earthquake-induced land­ Gedn e~', 0 .5., and Webe t jr, W.G ., 1978 , De sign and construe­ slides to long-term slope erosion and slope-fail ure hazards tion of soil slop es, in Schuster, R.L. , and Krizek, R.j. , eds., in seismically active regions: Geo mo rphology, v. 10, p. 265 ­ Landslides, analysis and cont rol: Nation al Research Co un­ 284 . cil, Transportatio n Research Report 176, C hap ter 8, p. Kley, J , and Mo na ldi , C R., 1999, Esrr ucrura de las Sierras 172-1 9 1. Subandinas y del Sistema de Sant a Barbara, in Geologia del Gonzales D faz, E.F., and Fauq ue, L.E., 198 7, Proveniencia del noroeste arge nt ino, Relarorio, Congreso Geologico Argen ­ material cornponenral del torrerire de barro de "EIVolcan» tin o, l-i th, Salta: Buenos Aires, Asociac ion Geologica Ar­ -Quebrada de Humahu aca (Iujuy}- Republica Argentina, gentina, v, 1, p. 415-425. in Aetas, Congreso Geologico Argentino, l Orh, Tucurnan: Kley, J. ,an d Monaldi, C R., 2002, Tectonic inversion in the Santa Buenos Aires, Asociacion Geologica Argentina, v. 3, p. 309­ Barbara System of the cenrral Andean foreland thru st belt , 312. nor thw estern Arge ntina: Tecronics, v. 2 1, no . 6, p. 1-18. Gonzalez Dtaz, E.F., and Malagn ino, E.e., 1990 , EI proceso de la Kochel, R.e., 1987, H olocene debris flows in cent ral Virginia, in rernoc ion en masa: su incidencia co mo riesgo natu ral en el COS ta, J.E., and Wieszorek, G.P. , eds., De bris flows/Ava­ feno rneno del 29- 3- 1984 en el suresre de la Sierra de Agua­ lanches: Process, Recogni tion, and Mi tigation: Geolo gical rague, Salta (Repu blica Argentina): Revista de Geo logia Sociery of America, Reviews in Engineering Geology, v. 7, Aplicada a la Ingen ierfa y al Ambiente, Buenos Aires, Aso­ p. 139-1 55. ciacion Argentina de Geo logia Aplicada a la Ingen ierfa, v. Leighton, F.B., 196 6, Landslides and hillside development, in En­ 5, p. 7-18. gineering Geology in Southern California: Los Angeles, Hansen, M.]., 1984, St rategies for classification of landslides, in Association of Engineering Geologists, Special Publication, Bru nsden , D ., and Prior, D .B., eds., Slope instability: p. 149-207. C hichester, John Wi ley & So ns, p. 1-25. Marcuzzi, ].] ., Wayne, W.]., and Alonso, R.N ., 1994, Geo logical Hauser, Ar turo, 1985, Flujos de bar ro en la zona preand ina de la hazards of Salta Province, Argent ina, in Proceedings, In­ Region Metropolirana: caracreristicas, causas, efecros, ries­ ternational Association of En gineering Geology Con gress, gos y med idas preventivas: Revista Geol ogica de Chile, no. 7'h: Ro tte rdam , Balkema, p . 2039 -2048 . 24, p. 75- 92 . Mon, R., 1979, Esquema rectonico de los Andes del norte argen­ Hermanns, R.L., and Srrecker , M. R., 1999, Structu ral and litho­ tino: Revisra de la Asociacion Geologica Argenti na, v. 34, logic conrrols on lar ge Q uatern ary ro ck ava lanches, no . I, p. 53-60. sturzstrorns , in arid north western Argentina: Geological Mon, R., 1999, Cordillera O rient al, in GeologIa del noro este Sociery of Ame rica Bulletin , v. 111, no. 6, p. 934-948. argent ino, Relaror io, Co ngreso Geologico Arge nti no. 14th, Herman ns, R.L., Trauth, M .H ., McWill iams , M ., and Strecker, Salta: Buenos Aires, Asociac ion Geo logica Argentina, v. 1, M. R., 2000, Tephr och ron ologic con straints on tem poral p. 426-43 1. distribution of large landslides in NW-Argentina: Journal Moreiras, S.M ., 2004, Landslide incidence zonation in th e rio of Geo logy, v. 108 , p. 35-52. Mendoza valley, Mendoza pro vince, Argentina: Earth Sur­ Hungr, 0. , Morgan, G.C, VanDi ne, D.F., and Lister, D .R., 1987, face Processes and Landforms, v, 29, p. 255 -266. Debris flow defenses in British Columbia, in Cos ta, J.E., and Neary, D .G ., and Swift, L.W., ] r., 1987, Rainfall thres holds for Wieszorek, G.F., eds., Debris flows/Avalan ches: Process, rriggering a debris avalanching event in the sou thern Appa­ Recogn itio n, and Mitigation: Geo logical Society of Amer ica, lachian Mountains in Co sta, J.E., and Wieszorek, G .F., Reviews in Engineering Geology, v. 7, p. 201-222. eds., De bris flows/Avalanches: Process, Recog nitio n, and IAEG Commission on Lan dslides, 1990 , Suggested nom enclarure M itigation : Geo logical Society of America, Reviews in En­ for landslides. Internat ional Assoc iarion of Eng ineer ing gineering Geology, v. 7, p. 8 1-92 . Geology, Bulletin, v, 4 1, p. 13-16. Pierson , T.C , 1986, Flow behavior of channelized debris flows, Igarzabal, A.P. , 197 1, Rerno cion en rnasa en la Qu ebrada del Toro M ou nt Sr. Helens, Washington, in Abrahams, A.D ., ed., (Salta): Tucurnan, Universidad Nacional de Tucurnan, Opera Hillsl ope Processes: Binghamton Symposium Series in Geo­ Lilloana, v. 21 , 70 p. morphology, Winchester, MA, Allen and Unwin, Inc ., v. Igarzabal, A.P., 1979, Los flujos densos de la Quebrada de Escoipe, 16, p. 269 -296. in Aetas , Congreso Geo logico Argenti no, 7th, N euquen Pierson, T.e., and Costa, J.E., 1987 , A rheologi c classification of (1978): Buenos Aires, Asociacion Geologica Argentina, v, subaerial sediment-water flows, in Cos ta, J.E., and W ieszorek, 2, p. 109-11 7. G .F., eds., Debri s flows/Avalanches: Process, Recogn ition, Igarzabal, A.P. , 199 1, Mo rfologia de las provi ncias de Salta yJujuy: and M itigatio n: Geological Sociery of America , Reviews in Juju y, Un iversidad Na ciona l de Jujuy, Revista del Insriruto Engineering Geology, v. 7, p. 1-12 . de G eologia y Minerfa, v, 8, p. 97-12 1. Piteau, D .R., and Peckham, F.L., 1978, Engineering ofrock slopes, Jackson. L.R., Jr., Kosraschuk , R.A., and MacDonald, G.M., 1987 , in Schuster, R.L., and Krysek, R.J., eds., Landslides: Analy­ Ide ntification of debr is-flow hazard on alluvial fans in the sis and contro l: Transportation Research Board, National Canadian Rocky Mounta ins, in Costa, lE., and Wi eszorek, Research Council, Special Report 176, Chapter 9, p. 192­ G. F., eds., Debris flows/Avalanches: Process, Recognition, 225.

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Polanski, J., 1966, Flujos rapidos de escombros rocosos: Buenos of catastrophic landslides of South America in the twenti­ Aires, Editorial Universitaria de Buenos Air ess, Manuales, eth century, in Evans, S.G., and De Graff, J.V, eds., Cara­ 67 p. serophic landslides: Effects, occurrence, and mechanisms: Reneau, S.L., and Dietrich , W.E., 1987, The importance of hol­ Boulder, Colorado, Geological Society ofAmerica Reviews lows in debris flow scud ies. Examples from Marin County, in Engineering Geology, v. 15, p. 1-34. California, in Costa, J.E., and Wieszorek, G.E, eds., De­ Trauth, M.H., and Strecker, M.R., 1999, Formation of landslide­ bris flows/Avalanches: Process, Recognition, and Miciga­ dammed lakes during a wet period between 40.000-25,000 cion: GeologicaJ Society of America, Reviews in Engineer­ yr B.P. in northwestern Argentina: Paleogeography, Paleo­ Lng Geology, v. 7, p. 165-180. climatology, Paleoecology, v. 153, no. 1-4, p. 277-287. Rib, H.T., and Liang, T., [978, Recognicion and identification, in Trauch, M.H., Alonso, R.A, Haselton, K.R., Herrmans, R.L., Schuster, R.L., and Krizek, R.]., eds., Landslides, analysis and Serecker, M.R., 2000, Climate change and mass move­ and control: National Research Council, Transportation ments in the northwest Argentine Andes: Earth and Plan­ Research Report 176, Chapter 3, p. 34-80. etary Science Letters, v. 179, p. 243-256. Rolleri, E.O., 1975, Sistema de Santa Barbara: una nueva provin­ Trauth, M.H., Bookhagen, B., Marwan, N., and Strecker, M.R., cia geologica argencina, in Aetas, Congreso Geologico Ar­ 2003, Multiple landslide clusrers record late Pleistocene gencino, 6ch, Bahia Blanca: Buenos Aires, Asociacion Geo­ climate changes in the NW Argentine Andes: Paleogeogra­ logica Argencina, v, 1, p. 239-255. phy, Paleoclimatology, Paleoecology, v. 194, p. 109-121. Ruiz Huidobro, O. J., 1949, Escudio geologico de la region de los Turner, ].C.M., and Mon, R., 1979, Cordillera Oriental, in Turner, cerros Quitilipi y Pirgua: Revisca de la Ascciacion Geologi­ J .C.M., coord., Geologia regional argentina, Segundo Sim­ ca Argencina, v. 4, no. 1, p. 40-75. posio: Academia Nacional de Ciencias de Cordoba, v. 1, p. Ruiz Huidobro, O.J., 1960, Descripcion geologica de la Hoja 8e 57-94. Chicoana, provincia de Salca: Buenos Aires, Direcciori UNESCO Working Party on World Landslide Inventory, 1990, A Nacional de Geologia y Mineria, Bolecfn 89, 46 p. suggesred method for reporting a landslide: International Ruiz Huidobro, O.J., 1968, Descripcion geologica de la Hoja 7e, Association of Engineering Geology, v. 41, p. 5-12. Salta, provincias de Salta y Jujuy: Buenos Aires, Insrituto Varnes, D.G. 1978, Slope movement types and processes, in Nacional Geologia Mineria, Bolecfn 109, 48 p. Schuster, R.L., and Krizek, R.J., eds., Landslides, analysis Salfiry, J.A., 2006, Geologia regional del valle Calchaqui: Buenos and control: National Research Council, Transportarion Aires, Academia Nacional de Ciencias Exactas, Fisicas, y Research Report 176, Chapter 2, p. 11-33. Naturales, Anales, v. 56 (2004), p. 133-150. Wayne, W.]., 1990, The diamicroris of the Rio Blanco basin, Salfiry, J.A., Monaldi, C.R., Guidi, E, and Salas, R.]., 1998, Mapa Cordon del Plata, Mendoza, in ].Rabassa, ed., Quarernary geologico de la Provincia de Salta, escala 1:500,000: Bue­ ofSouth America and Antarctic Peninsula: Rotterdam, AA nos Aires, Servicio Geologico Minero Argentino, 2 sheets. Balkema, v. 6, p. 2-31. Same, J.E., 1999, Geologia urbana de la ciudad de Salta, in Geo­ Wayne, W.J., 1993, Escoipe valley and the Cuesta del Obispo: a logia del noroeste argentino, Relarorio, Congreso Geolo­ classic region of slide movement: National Geographic gica Argentino, 14th, Salta: Buenos Aires, Asociacion Geo­ Society, Committee for Research and Exploration, Final logica Argentina, v. 2, p. 99-111. Report of projecr: 3438-86, 53 p. (unpublished). Schuster, R.L., 1996, Socio-economic significance of landslides, Wayne, W]., 1999, The Alemania rockfall dam: A record ofa mid­ in Turner, AX., and Shuster, R.J., eds., Landslides, investi­ Holocene earthquake and catastrophic flood in northwest­ gation and mitigation: Transportation Research Board, ern Argentina: Geomorphology, v. 27, p. 295-306. Nacional Research Council, Special Report 247, p. 12-35. Wayne, WJ., and Alonso, R.N., 1992, Catastrophic debris flows, Schuster, R.L., and Fleming, R.W, 1986, Economic losses and eastern slope of rhe Andes, northern Argentina: Geological fatalities due to landslides: Association of Engineering Ge­ Society of America, Abstracrs with Programs, v. 24, no. 7, ologists, Bulletin v. 23, p. 11-28 p.165-166. Schuster, R.L., and Kockelman, W.J., 1996, Principles of land­ Wieczorek, G.E., 1987, Effecr of rainfall intensity and duration slide hazard reduction, in Turner, AK., and Shuster, R.J., on debris flows in central Santa Cruz Mountains, Califor­ eds., Landslides, investigation and micigation: Transporta­ nia, in Costa, J.E., and Wieszorek, G.F., eds., Debris flows/ tion Research Board, National Research Council, Special Avalanches: Process, Recognition, and Micigation: Geo­ Report 247, Chapter 5, p. 91-105. logical Society of America, Reviews in Engineering Geol­ Schuster, R.L. Salcedo, D.A, and Valenzuela, L., 2002, Overview ogy, v. 7, p. 93-114.

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