Influence of Pre-Andean Crustal Structure on Cenozoic Thrust Belt

Home , Puncoviscana Formation

Inﬂ uence of pre-Andean crustal structure on Cenozoic thrust belt kinematics and shortening magnitude: Northwestern Argentina

David M. Pearson1,2,*, Paul Kapp1, Peter G. DeCelles1, Peter W. Reiners1, George E. Gehrels1, Mihai N. Ducea1,3, and Alex Pullen1 1Department of Geosciences, University of Arizona, 1040 East 4th Street, Tucson, Arizona 85721, USA 2Department of Geosciences, Idaho State University, 921 South 8th Avenue, Pocatello, Idaho 83209, USA 3Facultatea de Geologie Geoﬁ zica, Universitatea Bucuresti, Strada N. Balcescu Nr 1, Bucuresti, Romania

ABSTRACT shortening at this latitude is ~142 km, which in northernmost Argentina and Bolivia (Fig. 1; is moderate in magnitude compared to the 17–23°S), Cenozoic thin-skinned shortening The retroarc fold-and-thrust belt of the 250–350 km of shortening accommodated in within a thick Paleozoic basin exceeds 300 km Central Andes exhibits major along-strike the retroarc thrust belt of southern Bolivia (Fig. 2; e.g., McQuarrie, 2002). Southwest of variations in its pre-Cenozoic tectonic con- to the north. This work supports previous Salta, Argentina (Fig. 1; ~25°S), where this fi guration. These variations have been pro- hypotheses that the magnitude of shorten- thick Paleozoic basin was absent prior to Ceno- posed to explain the considerable southward ing decreases signifi cantly along strike away zoic time, steeply dipping reverse faults that are decrease in the observed magnitude of Ceno- from a maximum in southern Bolivia, largely locally inverted normal faults are suggested to zoic shortening. Regional mapping, a cross as a result of the distribution of pre-Ceno- have accommodated <100 km of shortening section, and U-Pb and (U-Th)/He age dating zoic basins that are able to accommodate a (Fig. 2; e.g., Allmendinger et al., 1983; Grier of apatite and zircon presented here build large magnitude of thin-skinned shortening. et al., 1991). Despite this large along-strike upon the preexisting geological framework A major implication is that variations in the variation in shortening magnitude and struc- for the region. At the latitude of the regional pre-orogenic upper-crustal architecture can tural style, a corresponding major southward transect (24–25°S), results demonstrate that infl uence the behavior of the continental lith- decrease in elevation and crustal thickness does the thrust belt propagated in an overall east- osphere during later orogenesis, a result that not accompany this transition in the Central ward direction in three distinct pulses during challenges geodynamic models that neglect Andes (e.g., Isacks, 1988), prompting specula- Cenozoic time. Each eastward jump in the upper-plate heterogeneities. tion that magmatic addition, tectonic underplat- deformation front was apparently followed ing, and/or crustal fl ow may have contributed by local westward deformation migration, INTRODUCTION signifi cantly to the crustal volume south of the likely refl ecting a subcritically tapered oro- thin-skinned Bolivian fold-and-thrust belt (Kley genic wedge. The fi rst eastward jump was at Cordilleran-style orogens form during con- and Monaldi, 1998; Husson and Sempere, 2003; ca. 40 Ma, when deformation and exhuma- vergence of oceanic and continental plates and Gerbault et al., 2005). tion were restricted to the western margin are characterized by long belts of continental Although inversion of rift faults and the dis- of the Eastern Cordillera and eastern mar- magmatism and shortening. An active example tribution of pre-orogenic basins have long been gin of the Puna Plateau. At 12–10 Ma, the of such an orogenic system is in South America, suggested to infl uence the style of deformation thrust front jumped ~75 km toward the east where shortening of the overriding plate results in the Central Andes (e.g., Allmendinger et al., to bypass the central portion of a horst block in continued growth of the Andes. In spite of the 1983), only recently have workers integrated of the Cretaceous Salta rift system, followed documentation of major along-strike variations geo-thermochronological results with structural by initiation of new faults in a subsystem in the style and magnitude of Cenozoic shorten- analysis in southern Bolivia to show that the spa- that propagated toward the west into this ing in the Andes (e.g., Allmendinger et al., 1983; tial extent of the Altiplano Plateau was largely preexisting structural high. During Pliocene Isacks, 1988; Kley and Monaldi, 1998; Kley controlled by the distribution of Mesozoic rift time, deformation again migrated >100 km et al., 1999), there is not a considerable along- faults and was established by ca. 25 Ma (Sem- eastward to a Cretaceous synrift depocenter strike difference in the relative convergence pere et al., 2002; Elger et al., 2005; Ege et al., in the Santa Bárbara Ranges. The sporadic velocity of the oceanic and continental plates 2007; Barnes et al., 2008). However, the infl u- foreland-ward propagation documented here nor in the age of the subducting oceanic Nazca ence of these pre-Cenozoic heterogeneities in may be common in basement-involved thrust plate (Oncken et al., 2006). In contrast, some infl uencing the kinematics of the thrust belt has systems where inherited weaknesses due to of the observed spatial variations in the style not been suffi ciently investigated in northwest- previous crustal deformation are preferen- and magnitude of Cenozoic retroarc shortening ern Argentina, despite the observation that early tially reactivated during later shortening. match with changes in pre-Andean stratigraphy Andean deformation spatially correlates with The minimum estimate for the magnitude of and structure of the South American plate (e.g., Cretaceous rift basins (Kley and Monaldi, 2002; Mpodozis and Ramos, 1989; Allmendinger and Carrera et al., 2006; Hongn et al., 2007; Insel *E-mail: [email protected]. Gubbels, 1996; Kley et al., 1999). For example, et al., 2012). One study at ~25.75°S, utilizing

Geosphere; December 2013; v. 9; no. 6; p. 1766–1782; doi:10.1130/GES00923.1; 11 ﬁ gures; 1 table; 2 supplemental ﬁ les. Received 1 March 2013 ♦ Revision received 30 August 2013 ♦ Accepted 31 October 2013 ♦ Published online 13 November 2013

20°SA Fig. 1B location studies, evaluating the importance of pre-orogenic crustal architecture (e.g., Allmendinger 21°S et al., 1983; Allmendinger and Gubbels, 1996; Bolivia Subandes Kley et al., 1999) is critical for understanding the main factors inﬂ uencing structural style relative to other models that largely neglect pre- Chile existing upper-plate heterogeneities and instead 21°S Puna-Altiplano Eastern Cordillera implicate climate (e.g., Lamb and Davis, 2003; Strecker et al., 2007), mantle dynamics (e.g., 25°S Argentina SB ranges Russo and Silver, 1994; Sobolev and Babeyko, 68°W 64°W 2005; Schellart et al., 2007; Husson et al., B 2012), or buoyant anomalies within the down- going plate (e.g., Jordan et al., 1983; Isacks, 22°S 1988; Ramos, 2009). Also, in spite of the hypothesized importance of shallow subduction beneath the Central Andes during Miocene time (e.g., Ramos, 2009), few workers have evalu- Bolivia ated the spatio-temporal correlation between the kinematic history of the thrust belt and an eastward migration of retroarc magmatism thought 23°S to indicate shallow subduction. This paper focuses on an E-W transect across the Eastern Cordillera tectonomorphic province Chile Lomas del Olmedo of the Andean retroarc thrust belt of northwest- Argentina ern Argentina (Fig. 1). Results presented here provide new constraints on the style, timing, kinematics, and magnitude of shortening of the 24°S fold-and-thrust belt at ~24.75°S latitude. These results: (1) indicate that the northwestern Argen- QdT tine thrust belt was deformed above a W-dipping décollement that transferred slip to a system of E-dipping back thrusts; (2) constrain the timing T Salta 050 100 km r Fig. 2

ana of eastward deformation propagation within the n L

sps u Major thrust faults Eastern Cordillera and suggest that the Creta-

25°S p r

am a c m Cenozoic sediment ceous rift architecture inﬂ uenced the evolution a ppe t a Cenozoic igneous rocks of the thrust belt at this latitude; and (3) increase e o ana R Mesozoic sed. rocks a the estimate of the magnitude of shortening at

A n Mesozoic igneous rocks g r this latitude, but they still suggest that signiﬁ - chc e h Paleozoic sed. rocks Paleozoic granitoids cantly less shortening was accommodated south Mostly Cambrian rocks of the thin-skinned Bolivian fold-and-thrust belt. This work complements existing work and 67°W 66°W 65°W 64°W 63°W underscores the importance of the preexisting Figure 1. Reference maps of study area showing (A) locations of tectonomorphic provinces tectonic framework in controlling the spatial (inset), and (B) geological map of southern Central Andes. Major along-strike changes in distribution of shortening, particularly during exposed rocks and structural style are apparent. Abbreviations: QdT—Quebrada del Toro; the nascent stages of thrust belt development. SB—Santa Bárbara Ranges. This, in turn, strongly inﬂ uenced the evolution of the orogenic system.

GEOLOGICAL BACKGROUND apatite thermochronometry of Cenozoic basin lack of infl uence of older structures on Ceno- strata that spatially correlate to a Cretaceous rift zoic thrust belt propagation (Siks and Horton, Tectonomorphic provinces of the central basin, suggests that a lack of infl uence of pre- 2011). These and similar studies are focused Andean retroarc include, from west to east (Fig. existing structures on thrust belt propagation is upon Cenozoic strata that refl ect regional depo- 1A; Jordan et al., 1983): (1) the Puna Plateau, a refl ected by a progressive eastward migration systems and evolving sediment source areas. relatively low-relief, topographically high (aver- of Cenozoic exhumation (Carrapa et al., 2011). In contrast, the approach taken here involves age elevation ~4 km) region of internal drain- Likewise, stratigraphic and detrital provenance (U-Th)/He apatite and zircon analysis of reverse age, where Paleogene thrust belt structures are analyses within a fault-bounded basin in the fault hanging walls that were uplifted and mostly buried by Cenozoic sedimentary and Eastern Cordillera at ~23.25°S record progres- exhumed during fault displacement. In addition volcanic rocks (this province is the southern sive eastward migration of the thrust belt and to resolving the potential spatial heterogeneity continuation of the broad, lower-relief Altiplano coupled foreland basin system and imply a of thrust belt kinematics implied by these prior Plateau of Bolivia); (2) the Eastern Cordillera,

Geosphere, December 2013 1767

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

20° A B collapse of a Carboniferous to Permian moun- an i r Frontal Frontal belt b tain belt (e.g., Kay et al., 1989), back-arc exten- belt + E Cord. am Carb. sion linked to subduction along the western C Devonian/Silurian o/ Upper Cenozoic rd margin of South America (e.g., Welsink et al., O 1995), or failed rifting related to opening of Revised estimate the Atlantic Ocean (e.g., Grier et al., 1991). In 24° Neoprot./Cambrianlow-grade rocks from this study northwestern Argentina, up to 5.5 km of Creta- ~150 km “deficit” ceous sediment, the Salta Group, were depos- Mz ited in concomitant rift basins (Salﬁ ty and

Foreland Basin Fill Foreland Total shortening Marquillas, 1994; Monaldi et al., 2008). Across estimate much of the transect, Cretaceous strata unconformably overlie the Puncoviscana Formation, 28° Transpampean Arch demonstrating that thick overlying Paleozoic “Predicted” Sierras magnitude of strata present in southern Bolivia were absent in South Latitude Pampeanas shortening Basement Precordillera northern Argentina prior to Andean orogenesis shortening (Salﬁ ty and Marquillas, 1994). Triassic Cuyo- Bolsones Basin Cenozoic Thrust Belt Evolution 32°

Major crustal shortening in the Central 05 km Andes began after the South American plate overrode the subduction zone during open- 0 50 100150 200 250 300 350 ing of the South Atlantic Ocean (e.g., Coney Magnitude of shortening (km) and Evenchick, 1994). Deformation propaga- Figure 2. Along-strike variations in stratigraphy and previous esti- tion has been sporadic through time, but most mates of the magnitude of retroarc shortening. (A) N-S stratigraphic authors agree that shortening in the central section across retroarc thrust belt, modifi ed from Allmendinger and Andean thrust belt began in Late Cretaceous Gubbels (1996). Mz—Mesozoic; Carb.—Carboniferous; Ordo— to early Eocene time in northern Chile (Sem- Ordovician. (B) Predicted (assuming an initially 40-km-thick crust pere et al., 1997; Arriagada et al., 2006; Jor- and local isostatic compensation; Isacks, 1988; Kley and Monaldi, dan et al., 2007) and propagated in an overall 1998) versus observed (Oncken et al., 2006) magnitudes of short- eastward direction. In northwestern Argentina, ening in retroarc thrust belt of southern Central Andes. A revised growth strata and apatite fi ssion-track data estimate of 142 km of shortening accommodated by the Eastern refl ect 40–30 Ma deformation in the eastern Cordillera at ~24.75°S is the sum of current results and existing esti- Puna Plateau and western Eastern Cordillera, mates for the Puna Plateau (Coutand et al., 2001) and Santa Bár- followed by an enhanced period of exhu- bara Ranges (Kley and Monaldi, 2002). mation from 20 to 15 Ma (Andriessen and Reutter, 1994; Coutand et al., 2001; Deeken et al., 2006; Hongn et al., 2007; Carrapa and a high-relief, topographically high (peak eleva- Paleozoic basement high (Transpampean arch; DeCelles, 2008; Bosio et al., 2009; Carrapa tions >6000 m), externally drained Cenozoic Figs. 1B and 2A; Tankard et al., 1995), thought et al., 2011). A pre–15 Ma (Reynolds et al., thrust belt with predominantly west-vergent to refl ect a remnant Ordovician (“Ocloyic”) 2000), possibly Eocene angular unconformity structures in Argentina that transition northward mountain belt (Mon and Salfi ty, 1995; Starck, across the Santa Bárbara Ranges (Salfi ty et al., into a bivergent system in Bolivia; and (3) the 1995). Poorly constrained Late Devonian to 1993) may refl ect an early phase of shortening Santa Bárbara Ranges, a region near the modern Mississippian orogenesis from central Argen- or the eastward migration of a fl exural fore- deformation front that consists of mainly east- tina to Peru (“Eohercynian/Chañic” orogenesis) bulge (DeCelles et al., 2011). dipping reverse faults, transitioning along strike eroded the original margins of the Ordovician In contrast to the 40–15 Ma evolution of the northward to the Subandes, a W-dipping thin- to Carboniferous basin (Fig. 2A; Starck, 1995). thrust belt, interpretations of the 15–0 Ma defor- skinned thrust belt in northernmost Argentina Although Ordovician rocks are prevalent on mation history in northwestern Argentina vary and southern Bolivia. the Puna Plateau west of this regional transect, signifi cantly (Carrapa et al., 2011; Hain et al., Ordovician to Devonian rocks are not exposed 2011). Some authors use regional correlations Paleozoic Architecture in the Eastern Cordillera southwest of Quebrada of sedimentary rocks interpreted in the context del Toro (Fig. 1B), indicating that this locality of a fl exural foreland basin to infer a progres- The Paleozoic geology of western Bolivia con- may approximate the northeastern boundary of sive eastward migration of the thrust belt (e.g., sisted of >10 km of sedimentary rocks deposited major Paleozoic deformation. DeCelles et al., 2011). Others suggest that an in a back-arc setting during Cambrian to Car- initially intact fl exural depositional system was boniferous time (Fig. 2; e.g., Sempere, 1995). Mesozoic Extension “broken” in mid- to late Miocene time as base- In northwestern Argentina, this Paleozoic basin ment-involved reverse faults were initiated or was shallower and more limited in extent (Fig. 2; Widespread but low-magnitude Mesozoic reactivated away from what was once a continu- e.g., Starck, 1995; Egenhoff, 2007) and formed extension affected much of western South ous, along-strike thrust front and foreland basin on the northeastern fl ank of a NNW-trending America and has been variously attributed to (e.g., Hain et al., 2011).

1768 Geosphere, December 2013

Rock Units A’ 64.25° W Cz Restored Cz

The oldest unit exposed in the retroarc of Deformed

d l

KTb n

the Central Andes is the Puncoviscana Forma-

n e

a u

i Cz l

n i

t km 025 en tion, which consists of variably metamorphosed C No Vertical No Vertical Exaggeration ЄOr

siltstone, argillite, and turbiditic sandstone, 64.5° W and it constitutes the majority of outcrop in the KTb ЄOr

mapped area (Fig. 3). In the Cachi Range, the Cz KTb westernmost mountain range in this transect, the QdT— Cz Modified from Modified from Kley and 2002 Monaldi,

Puncoviscana Formation exhibits a gradational ipt refer-

e g

ЄOr

64.75° W

R KTb

a o

ЄOr o

m t

2 n a

S 0

2 ЄOr

contact with the higher-metamorphic-grade La d l

a KTb

n Cz

g y

e R

i KTb h

c n Paya Formation (Galliski, 1983). These rocks U ЄOr e Rang Zapla Kley and ed from

have Neoproterozoic to Cambrian protoliths Cz and are correlative (Pearson et al., 2012); for Cz 20 65° W this reason and for simplicity, these rocks are Valley Lavayén Cz

collectively referred to as the Puncoviscana Valley Lavayén

Formation. In general, the Puncoviscana For- General Güemes

mation exhibits ﬁ ner grain size toward the west, Cz Cz 10

including outcrops of chert south of La Poma fault 65.25° W

Mojotoro Mojotoro

j o t o

o f a u l t

R a

o r o n t o g j e o 50 M

(Fig. 3). Locally, however, metamorphic recrys- 5 3 4 pЄp 10.4 ± 0.2 Ma ? 8 66 x x x x Єg

ЄOr 67 51 21 Ma 52 Ma 58 Ma 74 Ma tallization has increased grain size. In contrast, 3 4 9.3 Ma

3 Cz in the eastern Lampasillos Range and Quebrada 20 Ma 19 Cz Valley Lerma Salta Lerma Valley Lerma de las Capillas to the east (Fig. 3), the Punco- 18 65.5° W ЄOr

3 viscana Formation consists of 10–30-cm-thick 8 12.8 ± 0.2 Ma

fault

Lesser Lesser

r e

f a s s u e l

t L

9.0 ± 0.1 Ma 12.1 Ma 17 ﬁ ne-grained quartzites that are interbedded with 7.1 Ma

16 47

3 ЄOr

f o 6 a u n a l j t i u 6 Q

29 15 9.1 ± 0.2 Ma 8.5 Ma 10DP08 5–100-cm-thick slate beds. Closer to Quebrada 3 5.2 Ma 5

09DP15 14

f a

a u

h e g l

c n t a s

R a

P a

sch

9.7 ± 0.2 Ma

13 37

del Toro to the east, these rocks alternate on the 2

28 6

QdT 1

QT4

t l

u a f o

a 11 r t fault

o o 0 g l

l T ó 7 Gólgota e G ЄOr 4.7 Ma d 65.75° W 10DP07 53

kilometer scale with low-grade metapelitic rocks 6.3 ± 0.1 Ma a 81 3 ad 0 6

r * 5 eb

Qu 79 Solá fault Cz

s 4.4 ± 0.1 Ma

a KTb

0 ll 72 42 i

characterized by 3–20-m-thick siltite and ﬁ ne- 5 p a

ge C 9

n 4.2 Ma 4

Ra 6 fault

a 09DP47

a c l

t f Zamanca

an a

m c n

Za a

t e a Z

grained quartzite interspersed with slate. In the a

79 á a l Cz So d 09DP46

pЄp Q 8 fault

4 Capillas eastern Lampasillos Range and Quebrada de las 3

lt au 53

Capillas f

Capillas , primary depositional features are com- 1 s 6 66° W lla

pi ult

a 64 fa

a 7.3 ± 0.3 Ma C d 57 a Cz las es de 5.2 Ma M rada ueb Q

mon, including ﬂ ute casts and ripple marks (Fig.

0 6 fault

pЄp Calchaquí Calchaquí

0 x l o l s R i a n g as e p am L 9 4A), and some rocks are volcaniclastic. In the pЄp

85 09DP42

5 38 Ma* 8 uí fault 38 Ma* lchaq

a 1

C 7 77 KTb Cz

Lesser and Mojotoro Ranges (Fig. 3), the Punco- Cz

3 6

Calchaquí 7 Valley Valley 5 08DP08

Calchaquí Calchaquí 5

r fault

0 o La Poma

5 M

viscana Formation mainly consists of low-grade, e r

o Toro Muerto

f 1 a

2 u l t 6

51 66.25° W ﬁ ne-grained quartzite and metapelite. 09DP30 13.8 Ma x

e g C n a a c R

i h 2 Og 13.8 Ma Northwest of the Quebrada del Toro (Figs. Og 1 pЄp Czb pЄp 1 1

1 and 3), 526–517 Ma plutons (Hongn et al., 40 Ma

t 09DP07

a 4 f

c a 47 C 1 fault 2 Cachi Cachi

A 3

2010) intruded the Puncoviscana Formation. In Cz Cz 5 5 0 09DP06 A (km) Elevation Og 10

the Cachi Range, 485–483 Ma granitoids (Fig. 24.75° S 2; Pearson et al., 2012) also intruded the Punco- viscana Formation and are among the northernmost outcrops of the Famatinian magmatic arc. East of Quebrada del Toro (Fig. 3), the Middle to Upper Cambrian angular unconformity between highly deformed rocks of the Puncovis- cana Formation and overlying quartzite and shale of the Upper Cambrian Mesón Group (Adams et al., 2011) is exposed. Lower Ordovician shale Eroded hanging wall geometry constrained by (U-Th)/He data (Pearson et al., 2012) structure is inferred antithetic fault E-dipping structure is dominant, therefore W-dipping Pirgua Group conglomerates in the hanging wall of Cachi fault south transect are up to 3 km thick adjacent to their western fault boundary; absence the west indicates that this is an inverted normal fault at the western boundary of Salta Rift (Carrera et al., 2006). (point 4) Décollement dip constrained by structural relief in syncline Calchaquí Valley Muerto fault consists of a ~100 m wide zone intense strain that structurally overlies Toro The an overturned footwall syncline along its trend. Folding of the Puncoviscana Formation is required to overturn this contact and folds are interpreted as fault-propagation folds. Structural relief here constrains restored depth/dip of décollement locally overturned syncline in footwall of the Calchaquí fault (Hongn et al., 2007) is W-verging, likely a truncated fault-propagation fold. ~30° E-dipping back limbs against overturned footwall Reverse faults juxtaposed planar, synclines. Folding and faulting here likely represent deformation in the footwall of E-dipping Capillas fault (new name) whose displacement increases toward the north. Cenozoic sediment of possible Plio-Pleistocene age buried the E-dipping Zamanca fault (new name) that bounds the western margin of Zamanca Range. E-dipping Zamanca fault is dominant due to consistent along-strike hanging wall geometry; structure is pop-up therefore W-dipping Solá pop-up fault within a series of ~N-S Subtle growth strata in the footwall of W-dipping trending folds indicate minor pre-13 Ma shortening on the Gólgota fault and ~10 above Solá fault anticline seen to the north are eroded farther south, Cambro-Ordovican strata and the W-verging indicating a southward increase in along-strike displacement Possible 5-10° angular unconformity between Cambro-Ordovician rocks and a sliver of structurally higher Cretaceous strata Displacement along the Pascha fault increases southward, with erosion of a W-verging hanging-wall anticline to the south Strata dip more steeply here than in hanging wall of Solá fault, suggesting that these structures were rotated during later displacement on the Solá fault The Quijano fault (new name) to the east apparently branches with Pascha along-strike, but accommodated less displacement. Here, a remnant of Cretaceous strata is truncated by the Lesser fault (new name) This structure, with an open, S-plunging anticline in its footwall, is likely a lower-displacement antithetic fault that loses slip toward the south beneath Lerma Valley. Décollement depth constrained by thickness of Mojotoro fault hanging wall Regional elevation of Cretaceous Balbuena Subgroup and deeper basin structure constrained by seismic data (Kley and Monaldi, 2002) Lower detachment of Kley and Monaldi (2002) cropped for simplicity consistency with thrust belt in Eastern Cordillera. Section is thus semi-balanced 3 5 7 9 1 2 4 6 8 11 20 10 12 13 14 16 17 18 21 15 19 and quartzite of the Santa Victoria Group over- Cross section notes lie the Cambrian Mesón Group. Together, these rocks constitute the majority of the Pascha, 116 km shortening + 21 km (95 km in SB Ranges) Cordillera in Eastern Lesser, and Mojotoro Ranges (Fig. 3). 40 Ma Single grain x Quebrada del Toro; SB—Santa Bárbara Ranges. Toro; del Quebrada Figure 3. Regional map and balanced cross section, with sample locations and (U-Th)/He apatite and zircon age results. Superscr age results. section, with sample locations and (U-Th)/He apatite zircon 3. Regional map and balanced cross Figure ences: 1—Pearson et al. (2012); 2—Adams et al. (2008). Map and cross section in the Santa Bárbara Ranges are modiﬁ section in the Santa Bárbara Ranges are ences: 1—Pearson et al. (2012); 2—Adams (2008). Map and cross Abbreviations: additional information. décollement. See text for deeper interpreted we excluded their Monaldi (2002); notably, Bedding orientation Bedding parallel cleavage, facing unknown Anticline axial trace Overturned bedding Overturned anticline axial trace Syncline axial trace Overturned syncline axial trace

Up to 2 km of synrift Cretaceous nonma- 25 36 45 uncertainty; σ 10DP07 rine conglomerate and sandstone of the Pirgua 21 Ma 13.8 Ma

Subgroup disconformably overlie Paleozoic (U-Th)/He apatite age (U-Th)/He zircon age rocks in the Santa Bárbara Ranges (Salﬁ ty and > Cross section Monocline axial trace Dip of fault (triangle) and trend plunge of striae on fault surface (diamond) Reverse fault; teeth on hanging wall Lithologic contact Marquillas, 1994; Kley and Monaldi, 2002). Strike-slip fault with relative motion Mainly Upper Cambrian to Ordovician sedimentary rocks, with local Silurian to Devonian in the eastern part of map area Neoproterozoic to Middle Cambrian Puncoviscana and La Paya Formations: variably metamorphosed turbidites Lower Ordovician granitoids Cenozoic Mainly Cretaceous rocks of Pirgua and Balbuena Subgroups Quaternary basalt flows Cambrian granitoids A’ 55 Growth strata in Quebrada del Toro (DZ samples 08DP01 and 08DP03). Toro Growth strata in Quebrada del sample 08DP04 = 9.4 Ma U-Pb tuff Cenozoic exhumation thermo-chronometer closure depth * Neogene exhumation < thermo-chronometer closure depth U-Pb detrital zircon sample locality 30 Cz Єg *All (U-Th)/He apatite grains from this sample have very low eU Weighted mean (U-Th)/He apatite ages at 2 Weighted (U-Th)/He age from sample Youngest Og KTb Czb ЄOr Geo- and Thermochronology pЄp A Solid where well located, dashed poorly dotted buried Legend In several localities, synrift depocenters corre- Geological symbols

Geosphere, December 2013 1769

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

A B ~N ~S

n tio p a u m o r r Fo g a b n u a cordierite S c s porphyroblasts a i n v e o u c lb n a u B P

0 0.25 m 0 ~5 m

C D W E Toro Muerto fault

Puncoviscana Formation overturned angular unconformity

Yacoraite Formation

0 30 cm 0 ~10 m

E F W E ~SE ~NW

brian Gólgota fault Cam p Pre 12.8 Ma angular u f ro ore unconformity g gr b ou Qls nd u c S ol l u ~ a viu v n m co e n fo 1 u rm 2. lb Cambrian a 8 Ma a f bl lava B or e flowa egr Ba ou rr v nd es collu sa vium nd sto 0 ~400 m ne 0 ~15 m

Figure 4. Outcrop photos. (A) Flute casts in Puncoviscana Formation turbidites in Quebrada de las Capillas; (B) major angular unconformity (>450 m.y.) between Puncoviscana Formation and Balbuena Subgroup rocks in the Quebrada de las Capillas; (C) irregular folding of likely early Paleozoic age within Puncoviscana Formation in Lampasillos Range; (D) overturned syncline and angular unconformity in the footwall of the Toro Muerto fault in the eastern Cachi Range; (E) likely fault-propagation fold in Balbuena Subgroup rocks south of La Poma; and (F) overturned syncline in footwall of Gólgota fault and >13 Ma (K-Ar age; Mazzuoli et al., 2008) angular unconformity below Barres sandstone demonstrating subtle early growth. Qls—Quaternary landslide.

1770 Geosphere, December 2013

spond to Cenozoic reverse fault hanging walls mendinger et al., 1983). Although no volcanic bedding is transposed, and rootless isoclinal (Kley and Monaldi, 2002). Much of the mapped centers are exposed along the current transect, folds prohibit assessment of stratigraphic facing region west of the Santa Bárbara Ranges rep- tuff, volcaniclastic, and fl ow deposits of inter- direction beyond the outcrop scale. Although resents the Salta-Jujuy High, considered to be mediate composition (Mazzuoli et al., 2008) open to tight chevron folds are common across a horst block in the central part of the Salta occur as interbeds in a dominantly clastic sedi- the transect (Fig. 4C), rocks generally are less rift (Salfi ty and Marquillas, 1994). However, a mentary succession near the northern Quebrada tightly folded toward the east. Bedding, bed- minor remnant of Pirgua Subgroup is exposed del Toro; the Las Burras (Hongn et al., 2010) ding-parallel cleavage, and primary cleavage near the Pascha Range (Salfi ty and Monaldi, and Acay (Petrinovic et al., 1999) plutons likely within slate, phyllite, and quartzite generally dip 1998), and up to 3 km of strata are exposed in represent the intrusive equivalents of these moderately to steeply to the northwest or south- the southern portion of the Cachi Range (Fig. 3; rocks and are exposed just north of the current east across the transect (Figs. 3 and 5), with the Carrera et al., 2006). Overlying the Pirgua Sub- transect. Miocene magmatism was followed by exception of within the Quebrada de las Capillas group and adjacent structural highs, there is a eruption of shoshonites of likely Pleistocene age and southern Lesser Range, where foliations dip thinner but more regionally contiguous package near the northern part and eastern margin of the toward the northeast or southwest. Within the of postrift Upper Cretaceous to Lower Eocene Cachi Range (Fig. 3; Kay et al., 1994; Ducea Cachi Range, fi ne-grained metamorphic min- sandstone, limestone, and shale of the Balbuena et al., 2013). erals include ~1-mm-diameter anhedral cor- and Santa Bárbara Subgroups (Salfi ty and Mar- In the higher-elevation regions along the dierite that increases in size toward the core of quillas, 1994). In the Quebrada de las Capillas, transect, Pleistocene glacial deposits and land- the range; farther south, correlative rocks were the depositional contact between previously slides are abundant. Dark alluvial and landslide subjected to granulite-facies metamorphism and deformed Puncoviscana Formation and overly- deposits, also of likely Pleistocene age (Trauth anatexis (Pearson et al., 2012). Much of this ing Balbuena Subgroup is exposed (Figs. 3 and et al., 2000), unconformably blanket Cenozoic deformation and metamorphism is thought to 4B). Here, the angular discordance is 45°–90°, rocks and range-bounding reverse faults in be Cambrian and Ordovician in age (Mon and and overlying sandstone contains angular clasts many places at range margins. Terrace depos- Hongn, 1991; Mon and Salfi ty, 1995). N-S– of Puncoviscana Formation quartzite; minor its of likely late Pleistocene age, in turn, over- striking ductile shear zones, also likely Ordo- fault slip has also occurred along the primarily lie these sediments and are locally covered by vician in age, have also been documented in depositional contact. Holocene alluvium. For simplicity, all Cenozoic the Cachi Range (Pearson et al., 2012). East of Most workers attribute the accommodation sedimentary rocks are considered as one map the Cachi Range, rocks underwent lower-grade space within which Balbuena rocks were depos- unit (Fig. 3). peak metamorphic conditions, and cordierite ited to postrift thermal relaxation and associated porphyroblasts are rare to absent. Although the subsidence, an interpretation that is corrobo- STRUCTURAL GEOLOGY orientations of bedding, bedding parallel cleav- rated by the spatial coincidence of Paleogene ages, and primary cleavages are variable in ori- depocenters with Cretaceous grabens (e.g., Work presented here was conducted along an entation, on the scale of the transect, the Punco- Starck, 2011). Elsewhere, workers have inter- ~130-km-long E-W transect across the Eastern viscana Formation usually dips more steeply preted the Paleocene to Miocene succession as Cordillera at 24.5–25°S latitude (Figs. 1 and than younger strata and is generally NE-SW part of an eastward-advancing fl exural foreland 3). Field work involved geological mapping striking and moderately to steeply NW-SE dip- basin system (e.g., DeCelles et al., 2011). It is and structural analysis, coupled with sample ping (Fig. 5), an observation consistent with likely that the foreland basin related to growth collection for U-Pb and (U-Th)/He analysis of regional measurements of Puncoviscana Forma- of the Andes interacted in a complex way with detrital and igneous zircon and apatite. Much of tion rocks (Piñán-Llamas and Simpson, 2006). waning thermal subsidence following Creta- the fi eld work was accomplished by multiday ceous extension. foot traverses across high-elevation mountain Cenozoic Shortening The Paleocene–Lower Eocene fl uvial and ranges for which minimal published data exist. lacustrine deposits are overlain regionally by This regional transect was then linked with a Prominent Cenozoic faults consist of two Middle-Upper Eocene paleosols that transition balanced cross section across the Santa Bárbara types: (1) N-S–striking, mainly E-dipping reverse across strike to a disconformity in the eastern Ranges to the east (Kley and Monaldi, 2002) as faults that are expressed in the modern topog- part of the Eastern Cordillera (Salfi ty et al., well as thermochronological results and a bal- raphy, juxtaposed rocks of markedly differ- 1993; DeCelles et al., 2011). In turn, the paleo- anced cross section across the Puna Plateau to ent age, and are locally demonstrably inverted sols are overlain by 2–6 km of Upper Eocene to the west (Coutand et al., 2001). This work also Cretaceous normal faults; and (2) mainly NW- Lower Miocene upward-coarsening fl uvial and builds upon regional-scale mapping across the striking sinistral faults with minimal displace- eolian deposits, preserved within the current Salta province (1:500,000 scale; Salfi ty and ment that are discontinuous and often en eche- transect at the eastern side of Quebrada de las Monaldi, 1998) and west of Quebrada de las lon. These near-vertical faults have likely been Capillas (Fig. 3), and capped locally by middle Capillas (1:250,000 scale; Blasco et al., 1996), active during Holocene time. Miocene to Pliocene fl uvial, lacustrine, and and more detailed mapping in the northern Cal- Major N-S–striking reverse faults generally alluvial-fan deposits (Hernandez et al., 1996; chaquí Valley (Hongn et al., 2007), Quebrada dip 45°–60° toward the east and are character- Starck, 1996; Reynolds et al., 2000, 2001; Echa- del Toro (Marrett and Allmendinger, 1990), and ized by up to 200-m-wide zones of intense frac- varria et al., 2003; DeCelles et al., 2011). northern Cachi Range (Pearson et al., 2012). turing, with rare through-going fault surfaces or In mid- to late Miocene time, retroarc mag- fault gouge. In the footwalls of reverse faults matism migrated well east of the magmatic Paleozoic Structure where Upper Cretaceous and Paleogene rocks arc, with associated volcanic centers defi ning are preserved, overturned synclines are com- the NW-trending Calama–Olacapato–El Toro Within the study area, cleavage intensity and mon, with steeply dipping axial surfaces that are lineament that crosses the current transect near the grade of metamorphism increase to a maxi- subparallel to superjacent reverse faults (Fig. the Quebrada del Toro (Figs. 1 and 3; e.g., All- mum toward the west in the Cachi Range. Here, 3 and 4D). Corresponding hanging-wall anti-

Geosphere, December 2013 1771

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

Upper Cretaceous and Cenozoic Cambrian and Ordovician Poles to planes brada del Toro in the footwall of the Solá fault. Bedding (n=148) Bedding (n=104) Trends/plunges of fold axes Folds (n=7) Folds (n=10) Analytical details are available in the Supple- Cylindrical best fit fold axis mental File.1 Kamb contours Contour interval = 2σ Detrital zircon ages are shown on relative age- Significance level = 3σ probability diagrams (Fig. 6). In accord with Dickinson and Gehrels (2009), we constrain maximum depositional ages using the youngest age cluster in a sample deﬁ ned by three or more overlapping analyses. For the igneous sample, we attempt to minimize errors resulting from inclusion of inappropriate analytical data in age calculations by reporting a weighted mean age (Ludwig, 2001) of concordant and overlapping 206Pb/238U ages, with ﬁ nal uncertainties Puncoviscana Formation Folds (n=62) Bedding, bedding ll cleavage, that include all random and systematic errors primary cleavage (n=238) (Fig. 7).

(U-Th)/He Apatite

Apatite (U-Th)/He thermochronology is used here to constrain the timing and magnitude of rock exhumation, which we infer resulted from rock deformation. Our results supplement earlier work in the region (e.g., Coutand et al., 2001; Deeken et al., 2006; Carrapa et al., 2011) by placing ages of low-temperature thermochro- nometers in a structural context. (U-Th)/He thermochronometry of apatite generally refl ects the time since cooling of the apatite below ~70 °C Figure 5. Stereograms showing attitudes of sedimentary and metasedimentary rocks and (assuming an effective grain radius of 60 µm structures. and a cooling rate of 10 °C/m.y.; Farley, 2000). Using apatite fi ssion-track ages from vertical transects in the Cumbres de Luracatao (Fig. 1), clines were also observed in Cambrian–Ordovi- meter-scale offset of beds, brittle fault fabrics Deeken et al. (2006) obtained a Miocene geo- cian, Cretaceous, and Cenozoic rocks and are and kinematic indicators, tool marks, and NE- thermal gradient of ~18 °C/km. Using strati- consistent with fault-propagation folding being striking, antithetic dextral faults. In the Que- graphic exhumation depths and lack of com- a dominant structural style in the Eastern Cor- brada del Toro, portions of the Solá and Gólgota plete closure of the apatite fi ssion-track system, dillera at this latitude (Fig. 3E). The (U-Th)/He reverse faults (Fig. 3) that are coincident with Coutand et al. (2006) calculated a similar value zircon data obtained from the Cachi Range sug- the El Toro lineament (Salfi ty et al., 1976) are of <18 °C/km for the Angastaco Basin ~100 km gest that major antiforms in the hanging walls locally NW striking with horizontal slicken- to the south. This low geothermal gradient and of reverse faults, also interpreted to be fault- sides, demonstrating that late strike-slip faulting a mean annual surface temperature of 10 ± 5 °C propagation folds but at a more regional scale, exploited preexisting contractional structures yield a closure depth of the (U-Th)/He system accommodated the formation of up to 15 km of (Marrett et al., 1994). Despite the prevalence in apatite of 3–4 km; a more conservative gradi- structural relief (Pearson et al., 2012). See notes of these faults, none are through-going at the ent for a foreland basin (~22 °C/km; Allen and in Figure 3 for descriptions of individual Ceno- regional scale, and the more signifi cant of these Allen, 1990) yields closure depths of 2–3 km. zoic structures. faults are only characterized by tens of meters of Rock samples collected for (U-Th)/He apa- displacement (Acocella et al., 2011). tite thermochronometry consist of quartzites of Cenozoic Strike-Slip Faults the Puncoviscana Formation and Santa Victoria METHODS Group, and small Cambrian and Ordovician NW-SE-striking lineaments are visible in granitoids (two plutons in the Cachi and Mojo- aerial imagery across the southern Central U-Pb Zircon toro Ranges, and one dike in the Lampasillos Andes (Allmendinger et al., 1983) and are asso- Range; Fig. 3) that are exposed in the hanging ciated with some of the main retroarc magmatic U-Pb zircon geochronology by laser abla- walls of major reverse faults. Forty-nine individ- complexes (e.g., Riller et al., 2001). In some tion–inductively coupled plasma–mass spec- ual apatites were dated from 11 samples (eight cases, these lineaments are pre-Cenozoic in age trometry (LA-ICP-MS), following methods (Monaldi et al., 2008) and appear to segment described by Gehrels et al. (2008), was applied 1Supplemental File. PDF fi le of analytical details Cenozoic contractional structures (Coutand to eight detrital samples to better constrain prov- of U-Pb (zircon) geochronologic analyses. If you are viewing the PDF of this paper or reading it offl ine, et al., 2001). At the latitude of this study, these enance, ages of deposition, and deformation. A please visit http://dx.doi.org/10.1130/GES00923.S1 NW-SE–trending lineaments were locally con- tuff was also collected for U-Pb zircon analysis or the full-text article on www.gsapubs.org to view fi rmed as sinistral strike-slip faults based upon to constrain the age of growth strata in the Que- the Supplemental File.

1772 Geosphere, December 2013

08DP04 0.0022 Age = 9.4 ± 0.4 Ma 0.0018 Mean = 9.4 ± 0.3 Ma

U MSWD = 2.1

238 (2σ) 0.0014 17 Pb* / 0.0010 15 Map unit 206 13 11 0.0006 age 9 7 MDA: 10.5 Ma 08DP01 (n=73) 0.0002 0.00 0.04 0.08 0.12 207Pb* / 235U

MDA: 15.7* 08DP03 (n=85) Figure 7. Concordia plot and mean U-Pb zir-

Cenozoic con age of tuff within subtle growth strata in Quebrada del Toro. 2σ error includes internal and external errors. MSWD—mean square of weighted deviates.

MDA: 524 Ma 09DP15 (n=93) are better constrained than in the Lampasillos Range and intermittently along the Quebrada MDA: 543 Ma 10DP08 (n=87) de las Capillas where exposed rocks are dominantly the Puncoviscana Formation (Fig. 3). Where possible, we used along-strike constraints MDA: 536 Ma

Normalized probability 10DP07 (n=88) (i.e., down-plunge viewing) to reconstruct the geometry and style of deformation. Eroded hanging walls were also drawn with the minimal displacement required to satisfy available observations, yielding “minimum” shortening MDA: 476 Ma 09DP47 (n=47) estimates. However, along-strike preservation of likely breached fault-propagation folds east MDA: 522 Ma 09DP46 (n=88) of Quebrada de las Capillas suggests that current shortening estimates there are not greatly underestimated (Fig. 3). Although rocks younger than the Puncoviscana Formation are generally not

MDA: 556 Ma* 09DP42 (n=11) Neoproterozoic-Cambrianexposed Ordovician in the Cachi Range, (U-Th)/He zircon and apatite thermochronological results con- 0 200 400 600 800 1000 1200 1400 1800 2200 2600 3000 3400 3800 strain the geometries of eroded rocks (Pearson Age (Ma) et al., 2012). Marine-infl uenced carbonates of the Cre- Figure 6. Normalized probability plot of detrital zircon ages for samples collected from sedi- taceous Balbuena Subgroup were used as a mentary rocks across the Eastern Cordillera from 24°S to 25°S. MDA—Maximum Depo- regional reference horizon and provide a pre- sitional Age. Andean datum with which to estimate the minimum Cenozoic structural relief. The unde- formed regional elevation of these rocks is con- metasedimentary and three igneous); fi ve grains involved, locally inverted thrust system. The strained by interpretations of subsurface seismic were dated for seven of the samples, whereas method here utilized forward modeling and iter- lines at the fl anks of the Santa Bárbara Ranges four grains were dated from the other four sam- ative restorations. The thrust belt at this latitude published by Kley and Monaldi (2002). Folds ples (Table 1). involved previously deformed, strain-hardened and tilted strata in fault hanging walls suggest rocks that were subjected to pre-Cenozoic meta- shallowing fault dips in the subsurface (e.g., Balanced Cross Section morphism, behave as mechanical basement, and Grier et al., 1991; Kley and Monaldi, 2002; this commonly deform into pop-up structures. For study). This requires that slip accommodated We constructed a restorable, area-balanced these reasons, hanging-wall strain during fault on multiple faults at shallower crustal levels cross section at ~24.75°S (Fig. 3) using the soft- displacement was modeled using inclined shear is transferred at depth to fewer structures that ware LithoTect®. The main goal was to better in an orientation antithetic to faults (e.g., Gro- accommodate greater slip. This observation, constrain shortening estimates at this latitude shong, 1989). coupled with the lack of major structural relief and appraise along-strike heterogeneity in the The cross section is constrained by regional of basement rocks above their regional eleva- magnitude of retroarc shortening in the Central mapping and structural analysis. Geometries tion, precludes the presence of deep décolle- Andes. Additionally, the results better constrain of thrust sheets where Cambrian, Ordovician, ments or whole-scale crustal faulting at this lati- the subsurface structure within the basement- Cretaceous, and Cenozoic rocks are exposed tude. Although a two-décollement model, such

Geosphere, December 2013 1773

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

TABLE 1. (U-Th)/HE AGES FOR INDIVIDUAL APATITES U Th Sm eU 4He Mass Half-width Corrected age ±2σ Sample (ppm) (ppm) (ppm) (ppm) (nmol/g) (μg) (μm) FT* (Ma) (Ma) 09DP37 (24.644486°S, 66.29634°W); Ordovician granitoid grain 09DP37_ap1 1.1 2.3 178.6 1.6 0.1 4.4 58.8 0.8 15.0 0.6 09DP37_ap2 6.6 6.9 284.7 8.2 0.5 3.6 52.7 0.7 13.8 0.5 09DP37_ap3 0.7 1.8 67.8 1.1 0.0 5.6 69.3 0.8 7.5 0.6 09DP37_ap4 1.9 3.6 105.6 2.7 0.3 4.7 64.0 0.8 23.2 0.8 09DP44 (24.804378°S, 66.151696°W); granitoid of likely Cambrian age grain 09DP44_ap1 0.8 3.9 35.2 1.7 0.3 5.5 62.4 0.8 37.9 1.3 09DP44_ap2 2.2 4.4 49.7 3.3 0.7 1.6 45.9 0.7 53.5 2.0 09DP44_ap3 0.7 2.5 26.4 1.3 0.3 2.4 48.4 0.7 53.1 2.9 09DP44_ap4 1.5 5.2 44.7 2.7 0.5 1.5 40.0 0.7 49.4 2.6 09DP45 (24.714586°S, 66.048758°W); Lower Cambrian Puncoviscana Formation grain 09DP45ap1 6.0 8.3 33.1 7.9 0.2 0.7 31.8 0.6 7.9 1.0 09DP45ap2 35.0 34.6 186.2 43.2 1.2 0.5 31.0 0.6 9.0 0.4 09DP45ap3 1.4 6.8 126.2 3.0 0.1 3.3 58.3 0.8 7.3 0.5 09DP45ap4 8.3 79.7 59.2 27.0 0.4 0.5 30.8 0.6 5.2 0.5 09DP45ap5 3.4 18.3 270.4 7.7 0.2 0.7 33.9 0.6 6.6 1.0 09DP47 (24.80377°S, 65.809525°W); Lower Cambrian Puncoviscana Formation grain 09DP47ap1 80.1 67.5 296.0 96.0 1.7 5.9 63.7 0.8 4.2 0.1 09DP47ap2 2.6 9.1 365.9 4.7 7.9 9.0 79.7 0.8 342.7 10.9 09DP47ap3 6.3 27.7 533.5 12.8 0.7 1.4 42.4 0.7 14.3 0.6 09DP47ap4 24.9 72.1 177.6 41.9 0.7 1.2 43.0 0.7 4.7 0.2 09DP47ap5 3.9 20.9 438.9 8.8 1.2 0.6 34.0 0.6 42.2 1.8 10DP07 (24.536595°S, 65.756178°W); Ordovician Santa Victoria Group grain 10DP07_ap1 9.6 43.1 307.2 19.8 0.5 1.7 42.5 0.7 7.2 0.3 10DP07_ap2 9.1 59.0 81.2 23.0 0.5 1.0 35.3 0.6 6.2 0.5 10DP07_ap3 8.4 24.6 295.6 14.2 0.5 4.6 56.5 0.7 8.2 0.3 10DP07_ap4 12.0 91.8 224.7 33.6 0.6 1.5 49.1 0.7 4.7 0.2 10DP08 (24.552606°S, 65.671056°W); Ordovician Santa Victoria Group grain 10DP08ap1 12.9 11.5 96.0 15.6 0.5 1.0 34.9 0.6 10.6 0.5 10DP08ap2 27.1 7.0 158.2 28.8 1.1 0.6 31.8 0.6 12.3 0.6 10DP08ap3 14.8 13.1 560.0 17.8 0.6 0.9 36.5 0.6 9.1 0.5 10DP08ap4 19.2 56.6 224.2 32.5 0.9 0.5 31.3 0.6 9.1 0.5 10DP08ap5 18.6 10.7 244.8 21.1 0.6 1.0 33.1 0.6 8.5 0.4 09DP15 (24.670446°S, 65.64119°W); Ordovician Santa Victoria Group grain 09DP15_ap1 2.5 2.4 1.0 3.0 31.2 5.3 59.7 0.8 2102.5 61.1 09DP15_ap2 6.1 19.5 321.8 10.6 0.2 3.5 59.6 0.8 5.2 0.3 09DP15_ap3 13.5 49.7 123.5 25.1 1.5 5.7 62.0 0.8 15.0 0.4 09DP15_ap4 23.0 9.0 92.0 25.1 1.5 3.6 63.0 0.8 14.1 0.5 10DP16 (24.766301°S, 65.602217°W); Lower Cambrian Puncoviscana Formation grain 10DP16_ap1 3.7 7.9 115.0 5.6 0.2 10.5 82.8 0.8 8.5 0.3 10DP16_ap2 3.9 16.2 817.8 7.7 0.5 3.0 49.6 0.7 13.6 0.5 10DP16_ap3 4.0 5.1 175.9 5.2 0.2 7.4 72.6 0.8 10.6 0.4 10DP16_ap4 15.2 161.6 576.3 53.1 1.6 5.2 67.7 0.8 7.1 0.2 10DP16_ap5 3.8 24.5 57.9 9.6 0.6 2.1 48.5 0.7 15.4 0.6 10DP15 (24.800167°S, 65.563095°W); Lower Cambrian Puncoviscana Formation grain 10DP15_ap1 14.2 15.9 91.7 17.9 0.8 1.6 41.0 0.7 12.1 0.4 10DP15_ap2 3.3 12.3 71.4 6.2 0.5 1.1 39.3 0.6 24.8 0.9 10DP15_ap3 11.3 21.5 289.2 16.4 0.9 6.7 64.9 0.8 12.7 0.3 10DP15_ap4 1.3 9.3 19.3 3.5 0.4 1.3 37.9 0.6 33.0 1.2 10DP15_ap5 6.7 20.1 358.4 11.5 0.6 0.8 34.4 0.6 16.4 0.7 11DP01 (24.796091°S, 65.359293°W); Cambrian granitoid grain 11DP01_ap1 53.1 4.6 293.3 54.2 4.0 1.5 40.0 0.7 20.8 0.6 11DP01_ap2 36.3 5.9 326.2 37.7 8.5 2.0 49.3 0.7 58.2 1.7 11DP01_ap3 29.4 4.0 318.7 30.3 7.3 17.2 91.7 0.8 52.5 1.5 11DP01_ap4 28.2 6.1 239.9 29.6 10.0 10.4 90.7 0.8 73.6 2.1 11DP01_ap5 0.9 1.8 244.9 1.3 0.3 23.3 108.1 0.9 35.2 1.3 10DP17 (24.719877°S, 65.339544°W); Lower Cambrian Puncoviscana Formation grain 10DP17_ap1 13.3 5.7 145.4 14.7 0.5 4.1 55.8 0.7 9.3 0.3 10DP17_ap2 16.4 29.6 284.0 23.4 1.0 2.5 47.5 0.7 11.3 0.3 10DP17_ap3 0.8 10.2 36.3 3.2 0.3 6.0 68.9 0.8 18.9 0.7 10DP17_ap4 4.4 27.7 521.2 10.9 0.5 1.7 44.9 0.7 10.8 0.5 10DP17_ap5 0.2 5.3 7.2 1.5 0.2 6.0 69.8 0.8 38.0 1.6 Note: 2σ represents formal analytical error of individual runs. Gray text: Analysis rejected on the basis of very low effective uranium (eU < 5 ppm). *Alpha-ejection correction.

1774 Geosphere, December 2013

as Kley and Monaldi’s (2002) for the Santa Bár- tion west of the Quebrada del Toro (Figs. 3 establishment of a topographic high and internal bara Ranges, could provide a better explanation and 6; Pearson et al., 2012; this study). These drainage at the modern eastern margin of the for local structures and deep seismicity (up to Ordovician rocks also contain a prominent Puna Plateau (Vandervoort et al., 1995; Coutand ~25 km; Cahill et al., 1992), our work suggests Neoproterozoic population of grains similar to et al., 2006). Upper Cambrian and Ordovician that structural relief was accommodated above a the youngest age peak from a sample of Pun- zircons dominate detrital zircon populations of regional, shallowly W-dipping décollement. coviscana Formation collected by Adams et al. samples collected from the Agujas Conglomer- The back limb of the hanging-wall anticline in (2008; sample QT4 in Fig. 3) in Quebrada del ate near this tuff (Fig. 6). Although recycling the Mojotoro Range is roughly concordant with Toro (Fig. 5). One detrital zircon sample col- cannot be ruled out, this suggests that their the Mojotoro fault, providing a good constraint on lected from an outcrop of turbidites mapped as sediment source during deposition was from the décollement at 9 ± 1 km depth there (Fig. 3). Puncoviscana Formation in the Quebrada de las the east, given that the main source of Ordovi- The shallower and deeper uncertainty limits Capillas (09DP47; Fig. 3; Salfi ty and Monaldi, cian grains on the Puna Plateau to the west was represent, respectively, the décollement depth if 1998) yielded several grains with Ordovician already hydrographically isolated. the hanging wall were to deform by fl exural slip ages. Two of these Ordovician analyses are rea- and the uncertainty in dip of the Mojotoro fault, sonably concordant and have acceptable errors (U-Th)/He Apatite which may dip more steeply than hanging-wall but do not defi ne a robust population (Dickin- strata (Fig. 2). A deeper décollement is incom- son and Gehrels, 2009). We tentatively maintain Forty-seven individual apatite grains ana- patible with thrust sheet thicknesses within the that these rocks are Puncoviscana Formation but lyzed by (U-Th)/He thermochronometry yielded Lesser, Pascha, and Mojotoro Ranges. Planar suggest that additional age evaluation of turbi- mostly Miocene and early Pliocene ages, with back limbs of these thrust sheets also suggest a dites in this region is warranted. a lesser number of Paleocene to Eocene dates décollement depth of ~9 km. This décollement is Two detrital zircon samples and a tuff were (Table 1; Fig. 7). Two other grains yielded comparable to Kley and Monaldi’s (2002) shal- collected from the Miocene Agujas conglomer- Proterozoic and Paleozoic ages, with low effec- lower décollement determined independently for ate (Marrett and Strecker, 2000) exposed in the tive U (eU = U + 0.235Th) and Th concentra- the Santa Bárbara Ranges to the east. Structures western part of Quebrada del Toro. These strata tions, making it unlikely that these anomalously west of the Quebrada del Toro generally involve occur in the core of a tight ~N-S–trending syn- old ages result from radiation damage that thicker thrust sheets and require a deeper décolle- cline in the footwall of the Solá and Gólgota enhanced He retentivity; instead, these old ages ment at ~11 km. Given that Balbuena Subgroup faults, and their deposition refl ects structural may have been compromised by He implanta- rocks at lower structural levels (e.g., in the Cal- growth (Fig. 3; DeCelles et al., 2011). Consistent tion (Spiegel et al., 2009). Multiple grains that chaquí Valley) appear minimally deformed, their with the results of DeCelles et al. (2011), a U-Pb generally form well-defi ned Upper Miocene to post-Cretaceous structural relief constrains the zircon age of a tuff from this section of 9.4 ± Lower Pliocene age clusters are considered here displaced thickness of supra-décollement rocks, 1.6 Ma (Fig. 7) indicates late Miocene deposi- to represent recent exhumation and cooling of yielding a regional décollement dip of ~2° west tion (time scale used throughout this paper is rock samples (Table 1; Fig. 8). of the Quebrada de las Capillas (Fig. 3). that of Ogg et al., 2008). This is >5 m.y. after Four Eocene (U-Th)/He apatite ages from major exhumation in the Cachi Range (Pear- the Lampasillos Range may represent an early RESULTS son et al., 2012) that was concurrent with the signal of Cenozoic exhumation and cooling

U-Pb Zircon Longitude (DD) U-Pb analyses of detrital zircons and a U-Pb -66.5 -66.3 -66.1 -65.9 -65.7 -65.5 -65.3 0 zircon age on a tuff help to constrain the prov- Westward younging enance, timing of sediment source emergence, exhumation 5 and the age of deposition of sedimentary and 10 low-grade metasedimentary rocks in the region. 15 U-Pb zircon results are available in the Supple- mental Table.2 For Puncoviscana Formation 20 rocks, the youngest zircon populations domi- 25 Age (Ma) nate and vary slightly in age (Fig. 6), indicating a continuous supply of young zircons dur- 30 ing deposition, and suggesting that maximum 35 depositional ages obtained from these rocks likely approximate depositional ages (Fig. 6). 40 Cambrian zircons also dominate detrital zircon 45 populations from Ordovician rocks of the Santa 50 Victoria Group; these ages are comparable to those obtained from the Puncoviscana Forma- 55 (U-Th)/He apatite grain age 60 2 (U-Th)/He zircon grain age Supplemental Table. Excel ﬁ le of U-Pb (zircon) 65 geochronologic analyses. If you are viewing the PDF of this paper or reading it ofﬂ ine, please visit http:// Figure 8. (U-Th)/He apatite (this study) and zircon (Pearson et al., dx.doi.org/10.1130/GES00923.S2 or the full-text arti cle on www.gsapubs.org to view the Supplemen- 2012) ages (±2σ) versus longitude across the transect. Grayed ages tal Table. lie outside of clusters and are considered partially reset.

Geosphere, December 2013 1775

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

and are consistent with subtle Eocene growth by the Santa Bárbara Ranges toward the east eastward migration of the fold-and-thrust belt strata documented in the Luracatao and Cal- (21 km; Kley and Monaldi, 2002) and a rough, during Cenozoic time, with additional local chaquí Valleys (Bosio et al., 2009; Hongn et al., line-length balanced shortening estimate of the westward propagation into lesser-deformed 2007). Unfortunately, the quality of these ages Puna Plateau southwest of the current transect at regions during times of inferred subcritical oro- is questionable, given their very low eU con- ~25°S (26 km; Coutand et al., 2001) results in genic wedge taper. Cretaceous to Eocene growth centrations; these and eight other analyses with a total shortening magnitude of 142 km (26%). structures and exhumation in what is now the eU concentrations of <5 ppm are not considered This total encompasses the entire retroarc thrust forearc of northern Chile record early stages in the following age evaluations. Nonetheless, belt east of the modern magmatic arc in northern of Cenozoic shortening near the latitude of this several (U-Th)/He zircon grains in the northern Chile. Additional Cretaceous to Paleogene short- study (Maksaev and Zentilli, 1999; Arriagada Cachi Range also yielded Eocene ages (Fig. 8; ening in northern Chile (Arriagada et al., 2006; et al., 2006; Jordan et al., 2007). In northwestern Pearson et al., 2012), which may attest to sig- Jordan et al., 2007) would increase this estimate. Argentina, however, Cretaceous and Paleocene nifi cant Eocene deformation at this time. Although this work was focused in the East- time marks a period of thermal subsidence that A (U-Th)/He apatite sample collected within ern Cordillera, fi eld observations and limited refl ects waning Cretaceous rifting (e.g., Starck, the core of the Cachi Range yielded a grain mapping in the eastern Puna Plateau also sug- 2011). By late Eocene time, contractional defor- age of 13.8 ± 0.5 Ma (Fig. 3; weighted mean gest that the existing estimate of shortening mation and exhumation had begun in the eastern ages henceforth), supplementing ca. 15 Ma accommodated there may be greatly underesti- Puna Plateau (Coutand et al., 2001; Carrapa and (U-Th)/He zircon (Pearson et al., 2012) and apa- mated. Neogene volcanic and sedimentary rocks DeCelles, 2008) and westernmost Eastern Cor- tite fi ssion-track ages (Deeken et al., 2006) col- buried many structures that are likely Cenozoic dillera (e.g., Deeken et al., 2006). Constraints on lected farther south in the same range. After this in age; where exposed, Ordovician rocks clearly the eastern limit of observed Eocene exhumation time, (U-Th)/He apatite results suggest that the accommodated major shortening. Although are limited by data quality, but Eocene exhu- location of exhumation jumped ~75 km toward some of this shortening likely occurred during mation may be recorded by samples collected the east to the Lesser, Mojotoro, Pascha, and Paleozoic time, apatite fi ssion-track results and from the Luracatao and Cachi Ranges (Figs. 1 Zamanca Ranges, which record an ~60 km west- subsurface seismic data from the eastern mar- and 3; Deeken et al., 2006; Pearson et al., 2012; ward-younging progression of cooling between gin of the Puna Plateau demonstrate that sig- this study), which are prominent topographic 12.8 and 4.4 Ma toward the Quebrada de las nifi cant Cenozoic shortening and exhumation features that mark the western boundary of the Capillas (Figs. 3 and 8). Across strike ~15 km occurred locally (Coutand et al., 2001; Carrapa Cretaceous Salta rift. Eocene growth strata in west of the Zamanca fault, samples collected et al., 2005). If the Puna Plateau accommodated intervening valleys may also refl ect deforma- from the immediate footwall of the Mesada fault shortening equivalent to the Eastern Cordillera tion in the western Eastern Cordillera at this time (this study) and ~40 km along strike of there in (45%), the predicted total shortening across (Hongn et al., 2007; Bosio et al., 2009). Defor- the hanging wall of the Tin-Tin fault (Carrapa the plateau is 90 km, which would increase the mation and exhumation within the eastern Puna et al., 2011) disrupt the westward-younging retroarc estimate to 206 km. However, this is Plateau continued during late Eocene to early trend, yielding (U-Th)/He apatite ages of ca. still ~85 km less than predicted by mass balance Oligocene time (Coutand et al., 2001), progress- 7 Ma. From a regional perspective, these results estimates that assume an initially 40-km-thick ing westward into the interior of the Puna Plateau build upon and modify preexisting results in the crust and local isostatic compensation (Fig. 2; into the late Oligocene (Carrapa et al., 2005), as region and suggest a pulse of exhumation and Isacks, 1988; Kley and Monaldi, 1998). occurred in the Altiplano Plateau to the north deformation at or since Eocene time within the Time-averaged shortening rates using existing (Fig. 10; e.g., Elger et al., 2005). From 20 to Luracatao Valley, Cachi Range, and Calchaquí estimates (Coutand et al., 2001) and the balanced 15 Ma, rocks in the Luracatao and Cachi Ranges Valley, followed by a second pulse in exhuma- cross section yield a shortening rate of 1.9 mm/yr in the western Eastern Cordillera record another tion at 15–10 Ma that occurred mainly in the from 40 to 12 Ma for the entire thrust belt at period of major exhumation (≥8 km locally; Cachi, Lesser, and Mojotoro Ranges. Exhuma- 24–25°S (Fig. 9), which is probably a minimum Deeken et al., 2006; Pearson et al., 2012); by this tion then progressed ~60 km westward from the value given that shortening within the Puna Pla- time, the modern eastern extent of the Puna Pla- Mojotoro and Lesser Ranges, with additional teau is likely underestimated. This was followed teau was established (Vandervoort et al., 1995). widespread unroofi ng occurring at ca. 7 Ma in by shortening at a rate of 6.5 mm/yr in the Eastern Exhumation continued within the Cachi Range the Quebrada de las Capillas and Lampasillos Cordillera from 12 to 4 Ma, a sharp increase that until <13.8 Ma (this study). Range (Fig. 3). occurred after the location of shortening jumped At 12–10 Ma, results presented here suggest ~75 km eastward to the Mojotoro, Lesser, Pascha, that the deformation front shifted ~75 km east- Balanced Cross Section and Zamanca Ranges and Quebrada de las Capil- ward to the E-dipping Lesser and W-dipping las. A fi nal episode of shortening at a rate of 5.3 Mojotoro faults (Figs. 3, 9, and 10), which are Total Cenozoic shortening across the Eastern mm/yr occurred within the Santa Bárbara Ranges exposed within the eastern portion of the Salta- Cordillera from the area-balanced cross sec- from 4 to 0 Ma (Kley and Monaldi, 2002). The Jujuy High of the Cretaceous rift system (Salfi ty tion is 95 km (45% over an E-W distance of resultant time-averaged, long-term shortening and Marquillas, 1994). The Mojotoro Range is 211 km; Fig. 3). The magnitude of shortening is rate since ca. 40 Ma is 3.6 mm/yr. the northern continuation of the Metán Range, not grossly underestimated within the Mojotoro, which is also bounded by a major W-dipping Lesser, Pascha, Zamanca, and Cachi Ranges DISCUSSION fault and spatially correlates with a >3-km-thick (Fig. 3). However, this estimate is likely to be Cretaceous synrift depocenter (Salfi ty and Mar- a minimum in the Quebrada de las Capillas and Timing and Kinematics of Shortening quillas, 1994). Thus, ca. 10 Ma (U-Th)/He apa- Lampasillos Ranges given the lack of hanging- tite ages from the Mojotoro Range (this study) wall strata to constrain deformed thrust sheet Coupled with previously published con- support a proposed early phase of deformation geometries. Adding 95 km of shortening to area- straints, results presented here (Figs. 9 and 10) of the same age in the Metán Range (Cristal- balanced shortening estimates accommodated corroborate earlier work suggesting an overall lini et al., 1997; Hain et al., 2011). Structural

1776 Geosphere, December 2013

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Inﬂ uence of pre-Andean crustal structure on Cenozoic thrust belt kinematics and shortening magnitude d Eroded section No Vertical No Vertical Exaggeration ini et al. Late Eocene (~40 Ma) Major deformation <4 Ma 0 50 km modified from Kley and Monaldi, 2002 Pliocene to Recent (4–0 Ma) Mid to late Miocene (12–4 Ma) Santa Bárbara Ranges Late Cretaceous – early Cenozoic Supercritical wedge Supercritical Lavayén Valley Active thrust faulting e Active thrust faulting Active S. Reference abbreviations: a—Pear- abbreviations: S. Reference ° 9.3 21 Salta 12.1 7.1 71 5.2 5 8.5 4.7 del Toro apatite ages Quebrada 4.2 or since 5–4 Ma from (U-Th)/He apatite ages Greatest exhumation at ~12–8 Ma (U-Th)/He wedge Supercritical Supercritical c b 5.7 Capillas Quebrada de las 5.2 37 f Valley apatite ages Calchaquí 70 Younging (U-Th)/He Younging 15 13.8 g g 40 Cachi Range

6 0 6

Elevation (km) Elevation 6 4 2 4X Vertical Exaggeration Vertical 4X Elevation (km) (km) Elevation 37 70 Not reset a 9.3 Eocene 15.7 (U-Th)/He apatite ages f ~15–13 Ma ~40 Ma and zircon ages (U-Th)/He apatite Growth strata a Pliocene to Recent Mid to late Miocene Eocene Growth strata (U-Th)/He zircon (U-Th)/He apatite son et al. (2012); b—DeCelles et al. (2011); c—Carrapa et al. (2011); d—Kley and Monaldi (2002); e—Hain et al. (2011), Cristall d—Kley and Monaldi (2002); e—Hain et al. (2011), c—Carrapa et al. (2011); son et al. (2012); b—DeCelles (2011); (1997); f—Hongn et al. (2007); g—Bosio (2009). Figure 9. Proposed kinematic history of the Eastern Cordillera and Santa Bárbara Ranges at 24–25 9. Proposed Figure Age constraints Generalized deformation Eocene (U-Th)/He zircon ages Neoproterozoic to Middle Cambrian rocks Cretaceous syn-rift rocks of the Pirgua Subgroup Mainly Upper Cambrian to Ordovician sedimentary rocks, with local Silurian to Devonian toward the east Cretaceous rocks of the Balbuena Subgroup Cenozoic g ~40 Ma Growth strata

Geosphere, December 2013 1777

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

Age of contractional deformation 40f which are the easternmost portion of the thrust 30e Datapoint 22–15 Ma 4–0 Ma belt at this latitude. Existing constraints suggest ~10 Ma 0 Ma that a pre–15 Ma unconformity in the Santa Bár- 8–4 Ma BoliviaEocene-Oligocene deformation bara Ranges may represent an earlier phase of 1000 m Extent of deformation (Salﬁ ty et al., 1993) or the passage ′ ″ Cretaceous rift and 23°0 0 S 1000-m isopachs of a ﬂ exural forebulge (DeCelles et al., 2011), n ry 35 da followed by the main period of post–9 Ma un Rift bo (Reynolds et al., 2000), likely Pliocene uplift 10 00 m (e.g., Kley and Monaldi, 2002). This is indica- Chile tive of another (>100 km) eastward jump in the 30e location of deformation. The structural similar- ity between the Santa Bárbara and Zapla Ranges Argentina

1 and the Mojotoro, Lesser, Pascha, and Zamanca 24°0′0″S 0

0 Subcritical Ranges to the west is intriguing: Both areas

ry are bounded on the east by a major, W-dipping Salta-Jujuy m a 0 d 4? n structure, and the latter region records a west- d u 30 o m High b 0 ward migration of exhumation toward the lesser- b ift ~40 Ma jump 40 R 0 Subcritical 10 deformed Quebrada del Toro, where recent a 40 deformation has been documented (Hilley and 15j 4 10 <4 Ma jump Strecker, 2005). Progressive rotation of faults ~10 Ma jump 25°0′0″S depicted by Kley and Monaldi (2002) also hints c 0 m 40 >15?g at a westward migration of deformation from 22i the Piquete and Centinela synrift depocenters m l 0 10 0 in the Santa Bárbara Ranges westward toward m 0 2 0 m 14- 0 the minimally deformed Lavayén Valley, where 3 Ma propa 0 0 gation 1 Subcritical active seismicity is focused within the growing k k 14 6 k 1 3 000 m Zapla Range (Cahill et al., 1992). This pattern of h 2 local migration of fault subsystems away from 29 38e 000 m 26°0′0″S the foreland may be common during inversion

67°0′0″W 66°0′0″W 65°0′0″W 64°0′0″W of rift systems, as preexisting bivergent faults are reactivated, followed by new faults formed Figure 10. Location of Cenozoic deformation and exhumation in northwestern Argentina in footwalls of inverted structures as the sub- closely correlates with Cretaceous synrift depocenters, as shown by isopachs of Pirgua Sub- critical orogenic wedge gains taper (Fig. 11). group (1000 m contour interval; Sabino, 2002). Reference abbreviations: a—Hongn et al. A sporadic eastward migration of deforma- (2007); b—Carrapa and DeCelles (2008); c—Bosio et al. (2009); d—Andriessen and Reutter tion interspersed with local, in-sequence west- (1994); e—Coutand et al. (2001); f—Ege et al. (2007); g—Salfi ty et al. (1993); h—Carrapa ward-migrating faulting is a scenario that dif- et al. (2005); i—Deeken et al. (2006); j—Pearson et al. (2012); k—Carrapa et al. (2011); fers markedly from that encountered ~100 km l—Hain et al. (2011), Cristallini et al. (1997); m—Cahill et al. (1992); n—Insel et al. (2012). to the south (Carrapa et al., 2011). There, Car- Black arrows indicate rapid eastward jumps in the location of the thrust front, which rapa et al. (2011) documented a progressive occurred at ca. 40 Ma, ca. 10 Ma, and <4 Ma. Gray arrows show local westward-propa- eastward migration of deformation. The dis- gating deformation that is the likely expression of a subcritically tapered orogenic wedge. crepancy in results may refl ect the infl uence of

growth during deposition of the Agujas Con- site K-Ar age; Mazzuoli et al., 2008) angular Cretaceous glomerate (10.5–9 Ma) also occurred within the unconformity below the Barres sandstone in the rift faults? Quebrada del Toro to the west (Fig. 3; DeCelles footwall syncline of the Gólgota fault (Fig. 4F) et al., 2011; this study), indicating that faulting and ca. 10 Ma growth strata above the W-dip- occurred over a >50 km width during this time. ping Solá fault (Fig. 7) attest to an early phase After initiation of signiﬁ cant exhumation of contractional deformation here. However, above the Lesser and Mojotoro faults, defor- (U-Th)/He apatite results from hanging-wall mation propagated progressively westward rocks structurally above these localities and into the Salta-Jujuy High, within the E-dipping abundant Ordovician zircon grains likely origi- fault subsystem beneath the Lesser, Pascha, and nating from the east indicate that most exhuma- Zamanca Ranges. A westward migration of tion did not occur until after 6–4 Ma, which deformation is supported by westward-young- coincides with the timing of exhumation associ- ing (U-Th)/He apatite ages (Fig. 8) and west- ated with the Mesada and Tin-Tin faults to the ward shallowing of thrust sheet dips toward the west (Carrapa et al., 2011; this study). Figure 11. Cartoon showing hypothesized Quebrada del Toro that record rotation of pre- Poor exposure and a lack of suitable rocks for reactivation of E-dipping Cretaceous normal viously deformed rocks in the hanging walls of thermochronometry inhibit assessment of the faults, followed by local westward migration the younger, western faults. A >12.8 Ma (ande- age of deformation in the Santa Bárbara Ranges, of shortening.

1778 Geosphere, December 2013

preexisting Salta rift architecture. To the south, One possibility is that lithospheric delamina- architecture strongly infl uenced the spatio- mainly E-dipping, preexisting Cretaceous faults tion could result in enhanced magmatism due temporal evolution of the thrust belt (Figs. 2 (Grier et al., 1991; Cristallini et al., 1997) were to an infl ux of asthenosphere, which may also and 10). There is a striking correlation between progressively inverted in front of the orogenic create space beneath the upper plate for a shal- the magnitude of shortening and distribution of wedge in a roughly continuous E-W rift basin. lowing slab, in turn promoting further foreland- Paleozoic strata in the retroarc of the Central In contrast, at 24–25°S, a lack of inversion- ward propagation of the thrust belt. This model Andes, suggesting that it is not mantle fl ow or prone Cretaceous rift faults within the central may explain some aspects of the Miocene convergence parameters that control the ability portion of the horst block may have promoted kinematic history of northwestern Argentina of the upper plate to deform, but rather the pre- an eastward jump in the location of deformation whereby magmatism is followed by slab shal- orogenic architecture of the upper plate (Fig. 2; (Figs. 10 and 11). The original confi guration of lowing and an enhanced eastward propagation Allmendinger and Gubbels, 1996; Kley et al., the rift also likely infl uenced the topographic of shortening. 1999). Due to the apparent decreased ability of expression of mountains across the Eastern Several workers have documented that the the upper plate to accommodate a portion of the Cordillera. South of the present transect, where modern spatial extent of the Altiplano Plateau convergence between the South American and the rift basin is better developed, W-dipping, was already in place before 25 Ma (e.g., Horton Nazca plates, the relative convergence along antithetic pop-up structures are less common; et al., 2001), following rapid Eocene and Oligo- strike at the subduction interface would be pre- instead, rocks were deformed within a major cene advancement of the thrust front to regions dicted to increase away from the Central Andes, eastward-propagating back-thrust belt, with of preexisting rift depocenters (Sempere et al., which may explain the formation of the Boliv- subdued topography east of Cachi refl ecting 2002; Elger et al., 2005; Oncken et al., 2006; ian orocline (e.g., Isacks, 1988; Allmendinger strain accommodation by primarily E-dipping Ege et al., 2007). Additional constraints pre- and Gubbels, 1996; Kley et al., 1999; Arriagada structures. In contrast, at the latitude of the sented here refi ne the timing and kinematics of et al., 2008). Salta-Jujuy High, several W-dipping pop-up the retro arc thrust belt in northwestern Argen- Coupled with existing estimates for the Puna structures form sharp topographic boundaries tina. During shallow subduction, the upper plate Plateau (Coutand et al., 2001) and Santa Bár- on the eastern margins of ranges (Fig. 3). accommodates increasing strain. As retroarc bara Ranges (Kley and Monaldi, 2002) near the thrust belts commonly involve a craton-ward latitude of the current transect, results presented Geodynamic Model thinning wedge of sedimentary rocks, enhanced here constrain a minimum estimate of 142 km foreland-ward propagation of the deformation for the total magnitude of shortening at 24–25°S Some workers have suggested that the seg- front during shallow subduction would thus (Figs. 2A and 3). These results also suggest that mented, “broken” nature of the Laramide and be likely to encounter older basement rocks at least in the Eastern Cordillera at this latitude, Sierras Pampeanas forelands refl ects base- with less overlying strata and greater preexist- this shortening estimate is not greatly underesti- ment deformation that occurs during shallow ing heterogeneities. Plateau formation may be mated. For comparison, the ~95 km of shorten- subduction (e.g., Dickinson and Snyder, 1978; enhanced in regions of pre-orogenic foreland ing within this domain is <50% of that accom- Jordan and Allmendinger, 1986). An eastward heterogeneities because distal uplifts increase modated in the Eastern Cordillera of Bolivia sweep of magmatism across the Altiplano-Puna orography and the formation of internally (McQuarrie et al., 2008). If the kinematics of Plateau from 25 to 15 Ma (e.g., Allmendinger drained basins, in turn providing a positive feed- shortening within the Altiplano and Eastern et al., 1997) has led some researchers to suggest back for formation of an orogenic plateau (Sobel Cordillera in Bolivia were largely controlled that southward-migrating shallow subduction et al., 2003). With continued deformation in the by the distribution of Mesozoic rift basins, occurred beneath much of the Central Andes Sierras Pampeanas, the Puna Plateau may grow then the northern and southern segments of the during this time, presumably associated with southward as intramontane basins accommodate thrust belt are very similar, but differ in their oblique subduction of the Juan Fernández Ridge additional strain that follows initial reactivation magnitude of shortening. One possibility is that (Yañez et al., 2001). In the literature, shallow of preexisting heterogeneities, much like within the Cretaceous rift basin in Bolivia was wider subduction is generally thought to cause mag- the Salta rift of northwestern Argentina. (e.g., Cominguez and Ramos, 1995) and more matic lulls; the conventional model suggests favorably oriented for inversion than in north- that retroarc magmatism signals steepening of Implications of Along-Strike Variations western Argentina (Fig. 10), which allowed for the subducting slab that follows shallow sub- in Shortening a greater magnitude of distributed shortening duction (e.g., Dickinson and Snyder, 1978). during Cenozoic time. At the latitude of north- However, retroarc magmatism occurred north- A primary observation by tectonicists work- western Argentina, the basement-involved Santa west of the Quebrada del Toro at ca. 15 Ma ing in the Andes is that the maximum magnitude Bárbara Ranges also could not accommodate (Hongn et al., 2010), which predates by ~5 m.y. of crustal shortening coincides with southern the large-magnitude (>100 km), thin-skinned the interpreted location of the Juan Fernández Bolivia, with shortening decreasing signifi - shortening absorbed by the Bolivian Subandes Ridge beneath 24–25°S (Yañez et al., 2001) and cantly along strike (Fig. 2B; Isacks, 1988; Kley because such a thick, pre-orogenic Paleozoic the ~75 km eastward jump in the deformation and Monaldi, 1998). Hypotheses that seek to basin did not exist at this latitude (Fig. 2). front by the Eastern Cordillera. Similarly, in the explain the along-strike change include the ori- The shortening estimate calculated here is southern Altiplano, enhanced retroarc deforma- entation of the relative convergence (Gephart, greater than existing approximations in this tion at 19–7 Ma followed the onset of retroarc 1994), mantle fl ow beneath the long subduct- region (e.g., Grier et al., 1991; Coutand et al., magmatism by up to 8 m.y. (e.g., Allmendinger ing slab (Schellart et al., 2007), and variations 2001), but it is still ~150 km less than predicted et al., 1997; Elger et al., 2005). in the pre-orogenic stratigraphic architecture of (Fig. 2; Isacks, 1988; Kley and Monaldi, 1998). Timing constraints suggest that the inferred the overriding plate (Fig. 2A; Allmendinger and Recent studies have suggested that local existence interval of slab shallowing corresponds closely Gubbels, 1996; Kley et al., 1999). of anomalously thin crust beneath the Puna Pla- with enhanced deformation and thrust belt prop- Results from the present study suggest that teau (~42 km; e.g., Yuan et al., 2002) may indi- agation in Bolivia and northwestern Argentina. the pre-Cenozoic structural and stratigraphic cate Cenozoic crustal loss. However, at ~25°S,

Geosphere, December 2013 1779

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

most geophysical studies suggest an ~55-km- of northern Chile, and that crustal shortening Arriagada, C., Cobbold, P.R., and Roperch, P., 2006, Salar de Atacama Basin: A record of compressional tectonics thick crust across much of the Andes (Yuan et al., alone may explain the observed thick crust at in the Central Andes since the mid-Cretaceous: Tecton- 2002; Tassara et al., 2006; Wölbern et al., 2009). 24–25°S. The overall along-strike decrease in ics, v. 25, no. 1, TC1008, doi:10.1029/2004TC001770. The initial crustal thickness in the Central Andes shortening magnitude is well explained by the Arriagada, C., Roperch, P., Mpodozis, C., and Cobbold, P.R., 2008, Paleogene building of the Bolivian oro- is poorly constrained. Assuming that the Andes distribution of pre-Cenozoic basins that are able cline: Tectonic restoration of the Central Andes in 2-D are underlain by a 55-km-thick crust and had to accommodate large-magnitude thin-skinned map view: Tectonics, v. 27, no. 6, TC6014, doi:10.1029 an initial crustal thickness of 35 km, ~190 km shortening. Coupled with a likely correlation of /2008TC002269. Barnes, J.B., Ehlers, T.A., McQuarrie, N., O’Sullivan, of shortening would be required at this latitude. Cenozoic thrust belt kinematics with the spatial P.B., and Tawackoli, S., 2008, Thermochronom- This is 48 km more than the ~142 km of short- distribution of the Cretaceous rift, this suggests eter record of central Andean plateau growth, Bolivia (19.5°S): Tectonics, v. 27, no. 3, TC3003, doi:10.1029 ening documented here; given that shortening in that the pre-orogenic architecture strongly infl u- /2007TC002174. the Puna and western Cordillera may be under- enced the style, kinematics, and magnitude of Blasco, G., Zappettini, E.O., and Hongn, F., 1996, Hoja estimated, we suggest that crustal addition (e.g., shortening, which, in turn, infl uenced the geo- Geológica 2566-I, San Antonio de los Cobres: Bue- nos Aires, Argentina, Programa Nacional de Carteas by crustal fl ow, magmatic underplating, etc.) may dynamic evolution of Andean orogenesis. Geológicas de la República Argentina, Direccion not be necessary to explain the observed crustal Nacional del Servicio Geológico, scale 1:250,000. ACKNOWLEDGMENTS thickness at this latitude. Bosio, P.P., Powell, J., del Papa, C., and Hongn, F., 2009, Middle Eocene deformation-sedimentation in the This research was conducted as part of the Con- Luracatao Valley: Tracking the beginning of the fore- CONCLUSIONS vergent Orogenic Systems Analysis (COSA) project, land basin of northwestern Argentina: Journal of South in collaboration with and funded by ExxonMobil. American Earth Sciences, v. 28, no. 2, p. 142–154, National Science Foundation grant EAR-0732436 doi:10.1016 /j.jsames .2009 .06.002. Regional geological mapping, structural supported data acquisition at the Arizona LaserChron Cahill, T., Isacks, B.L., Whitman, D., Chatelain, J., Petez, analysis, and geo- and thermochronological Center. This work benefi ted from discussions with A., and Chiu, J.M., 1992, Seismicity and tectonics in many people, including M. McGroder, F. Fuentes, Jujuy Province, northwestern Argentina: Tectonics, results indicate that the northwestern Argentine v. 11, no. 5, p. 944–959, doi:10.1029 /92TC00215. thrust belt at 24–25°S was deformed above a R. Waldrip, J. Kendall, G. Gray, R. Bennett, S. Lingrey , Carrapa, B., and DeCelles, P.G., 2008, Eocene exhuma- T. Hersum, T. Becker, and R.N. Alonso. B. Ratliff W-dipping décollement that transferred slip to tion and basin development in the Puna of north- provided assistance with LithoTect® software. western Argentina: Tectonics, v. 27, no. 1, TC1015, primarily E-dipping reverse faults in a major F. Shazanee, C. Hollenbeck, A. Abbey, I. Nurmaya, doi:10.1029 /2007TC002127. back-thrust belt that propagated in an overall and M. Hearn helped with mineral separations. Con- Carrapa, B., Adelmann, D., Hilley, G.E., Mortimer, E., eastward direction during Cenozoic time. Fol- structive reviews by J. Barnes and G. Hilley improved Sobel, E.R., and Strecker, M.R., 2005, Oligocene the manuscript. range uplift and development of plateau morphology lowing rapid eastward propagation of the thrust in the southern Central Andes: Tectonics, v. 24, no. 4, belt at ca. 40 Ma, (U-Th)/He and U-Pb age dat- REFERENCES CITED TC4011, doi:10.1029 /2004TC001762. ing of apatite and zircon constrains an ~75 km Carrapa, B., Trimble, J.D., and Stockli, D.F., 2011, Pat- Acocella, V., Gioncada, A., Omarini, R., Riller, U., Maz- terns and timing of exhumation and deformation in eastward propagation event at 12–10 Ma, when zuoli, R., and Vezzoli, L., 2011, Tectonomagmatic the Eastern Cordillera of NW Argentina revealed the thrust front bypassed the central portion of characteristics of the back-arc portion of the Calama– by (U-Th)/He thermochronology: Tectonics, v. 30, TC3003, doi:10.1029 /2010TC002707. a horst block in the Cretaceous rift system, fol- Olacapato–El Toro fault zone, Central Andes: Tecton- ics, v. 30, no. 3, TC3005, doi:10.1029/2010TC002854. Carrera, N., Munoz, J.A., Sabat, F., Mon, R., and Roca, E., lowed by subsequent initiation of new faults in a Adams, C.J., Miller, H., Toselli, A.J., and Griffi n, W.L., 2006, The role of inversion tectonics in the structure of subsystem that propagated toward the west into 2008, The Puncoviscana Formation of northwest the Cordillera Oriental (NW Argentinean Andes): Jour- Argentina: U-Pb geochronology of detrital zircons and nal of Structural Geology, v. 28, no. 11, p. 1921–1932, this region. Subsequently, deformation again Rb-Sr metamorphic ages and their bearing on its strati- doi:10.1016 /j.jsg .2006 .07.006. migrated >100 km eastward to a Cretaceous graphic age, sediment provenance and tectonic set- Cominguez, A.H., and Ramos, V.A., 1995, Geometry and synrift depocenter in the Santa Bárbara Ranges, ting: Neues Jahrbuch für Geologie und Palaontologie: seismic expression of the Cretaceous Salta rift system, Abhandlungen, v. 247, no. 3, p. 341–352, doi:10.1127 northwestern Argentina, in Tankard, A.J., Suarez- likely followed by westward-migrating defor- /0077 -7749 /2008 /0247 -0341. Soruco, R., and Welsink, H.J., eds., Petroleum Basins mation to its current location in the Lavayén Val- Adams, C.J., Miller, H., Aceñolaza, F.G., Toselli, A., and of South America: American Association of Petroleum ley. Approximately 100 km to the south, defor- Griffi n, W.L., 2011, The Pacifi c Gondwana margin Geologists Memoir 62, p. 325–340. in the late Neoproterozoic–early Paleozoic: Detrital Coney, P.J., and Evenchick, C.A., 1994, Consolidation of mation migrated progressively toward the east zircon U-Pb ages from metasediments in northwest the American Cordilleras: Journal of South American through time with no local westward migration Argentina reveal their maximum age, provenance and Earth Sciences, v. 7, no. 3/4, p. 241–262, doi:10.1016 tectonic setting: Gondwana Research, v. 19, no. 1, /0895-9811 (94)90011-6. documented. This suggests that the architecture p. 71–83, doi:10.1016 /j.gr .2010 .05.002. Coutand, I., Cobbold, P.R., de Urreiztieta, M., Gautier, P., of the thrust belt was strongly infl uenced by Allen, P.A., and Allen, J.R., 1990, Basin Analysis, Principles Chauvin, A., Gapais, D., Rossello, E.A., and Lopez- the confi guration of the Cretaceous rift, which and Applications: Oxford, UK, Blackwell, 451 p. Gamundi, O., 2001, Style and history of Andean Allmendinger, R.W., and Gubbels, T., 1996, Pure and simple deformation, Puna Plateau, northwestern Argen- likely infl uenced the discontinuous nature of shear plateau uplift, Altiplano-Puna, Argentina and tina: Tectonics, v. 20, no. 2, p. 210–234, doi:10.1029 deformation propagation in an overall foreland Bolivia: Tectonophysics, v. 259, no. 1–3, p. 1–13, /2000TC900031. direction since Eocene time; these results are in doi:10.1016 /0040 -1951 (96)00024-8. Coutand, I., Carrapa, B., Deeken, A., Schmitt, A.K., Sobel, Allmendinger, R.W., Ramos, V.A., Jordan, T.E., Palma, M., E.R., and Strecker, M.R., 2006, Propagation of oro- accord with recent work in southern Bolivia. and Isacks, B.L., 1983, Paleogeography and Andean graphic barriers along an active range front: Insights A regional balanced cross section across the structural geometry, northwest-Argentina: Tectonics, from sandstone petrography and detrital apatite fi ssion- v. 2, no. 1, p. 1–16, doi:10.1029 /TC002i001p00001. track thermochronology in the intramontane Angastaco Eastern Cordillera, coupled with existing short- Allmendinger, R.W., Jordan, T.E., Kay, S.M., and Isacks, Basin, NW Argentina: Basin Research, v. 18, no. 1, ening magnitude estimates for the Santa Bárbara B.L., 1997, The evolution of the Altiplano-Puna Pla- p. 1–26, doi:10.1111 /j.1365 -2117 .2006 .00283.x. Ranges and Puna Plateau, increases the estimate teau of the Central Andes: Annual Review of Earth Cristallini, E., Cominguez, A.H., and Ramos, V.A., 1997, and Planetary Sciences, v. 25, p. 139–174, doi:10.1146 Deep structure of the Metan-Guachipas region: Tec- of the magnitude of shortening at this latitude to /annurev .earth .25 .1.139. tonic inversion in northwestern Argentina: Journal of ~142 km, but it confi rms that signifi cantly less Andriessen, P.A.M., and Reutter, K.J., 1994, K-Ar and fi s- South American Earth Sciences, v. 10, no. 5–6, p. 403– shortening was accommodated south of the thin- sion track mineral age determination of igneous rocks 421, doi:10.1016 /S0895 -9811 (97)00026-6. related to multiple magmatic arc systems along the DeCelles, P.G., Carrapa, B., Horton, B.K., and Gehrels, skinned Bolivian fold-and-thrust belt. We sug- 23°S latitude of Chile and NW Argentina, in Reutter, G.E., 2011, Cenozoic foreland basin system in the gest that greater shortening than has been previ- K.-J., Scheuber, E., and Wigger, P.J., eds., Tectonics of Central Andes of northwestern Argentina: Implica- the Southern Central Andes: Structure and Evolution of tions for Andean geodynamics and modes of defor- ously documented was probably accommodated an Active Continental Margin: Berlin, Springer-Verlag, mation: Tectonics, v. 30, no. 6, TC6013, doi:10.1029 within the Puna Plateau and ancient retroarc v. 1, p. 141–153. /2011TC002948.

1780 Geosphere, December 2013

Deeken, A., Sobel, E.R., Coutand, I., Haschke, M., Riller, U., Hernandez, R.M., Reynolds, J., and Di Salvo, A., 1996, Análi- thrust belt, northwestern Argentina: Tectonics, v. 21, and Strecker, M.R., 2006, Development of the southern sis tectosedimentario y ubicación geocronológica del no. 6, doi:10.1029 /2002TC902003. Eastern Cordillera, NW Argentina, constrained by apa- Grupo Orán en el Río Iruya: Boletín de Informaciones Kley, J., Monaldi, C.R., and Salfi ty, J.A., 1999, Along-strike tite fi ssion track thermochronology: From Early Creta- Petroleras, v. 45, p. 80–93. segmentation of the Andean foreland: Causes and con- ceous extension to middle Miocene shortening: Tecton- Hilley, G.E., and Strecker, M.R., 2005, Processes of oscil- sequences: Tectonophysics, v. 301, no. 1–2, p. 75–94, ics, v. 25, no. 6, TC6003, doi:10.1029/2005TC001894. latory basin fi lling and excavation in a tectonically doi:10.1016 /S0040 -1951 (98)90223-2. Dickinson, W.R., and Gehrels, G.E., 2009, Use of U-Pb ages active orogen: Quebrada del Toro Basin, NW Argen- Lamb, S., and Davis, P., 2003, Cenozoic climate change as a of detrital zircons to infer maximum depositional ages tina: Geological Society of America Bulletin, v. 117, possible cause for the rise of the Andes: Nature, v. 425, of strata: A test against a Colorado Plateau Mesozoic p. 887–901, doi:10.1130 /B25602.1. no. 6960, p. 792–797, doi:10.1038 /nature02049. database: Earth and Planetary Science Letters, v. 288, Hongn, F., del Papa, C., Powell, J., Petrinovic, I., Mon, R., Ludwig, K.R., 2001, Isoplot/Ex, Rev. 2.49: Berkeley Geo- no. 1–2, p. 115–125, doi:10.1016 /j.epsl.2009 .09.013. and Deraco, V., 2007, Middle Eocene deformation and chronology Center Special Publication 1a. Dickinson, W.R., and Snyder, W.S., 1978, Plate tectonics sedimentation in the Puna–Eastern Cordillera transi- Maksaev, V., and Zentilli, M., 1999, Fission track ther- of the Laramide orogeny, in Matthews, V., III, ed., tion (23°–26°S): Control by preexisting heterogene- mochronology of the Domeyko Cordillera, northern Laramide Folding Associated with Basement Block ities on the pattern of initial Andean shortening: Geol- Chile: Implications for Andean tectonics and porphyry Faulting in the Western United States: Geological Soci- ogy, v. 35, no. 3, p. 271–274, doi:10.1130 /G23189A.1. copper metallogenesis: Exploration and Mining Geol- ety of America Memoir 151, p. 355–366, doi:10.1130 Hongn, F.D., Tubia, J.M., Aranguren, A., Vegas, N., Mon, ogy, v. 8, no. 1–2, p. 65–89. /MEM151 -p355. R., and Dunning, G.R., 2010, Magmatism coeval with Marrett, R., and Allmendinger, R.W., 1990, Kinematic Ducea, M.N., Seclaman, A.C., Murray, K.E., Jianu, D., Lower Paleozoic shelf basins in NW-Argentina (Tastil analysis of fault-slip data: Journal of Structural Geol- and Schoenbohm, L.M., 2013, Mantle-drip magma- batholith): Constraints on current stratigraphic and ogy, v. 12, no. 8, p. 973–986, doi:10.1016/0191 -8141 tism beneath the Altiplano-Puna Plateau, Central tectonic interpretations: Journal of South American (90)90093-E. Andes: Geology, v. 41, no. 8, p. 915–918, doi:10.1130 Earth Sciences, v. 29, no. 2, p. 289–305, doi:10.1016 Marrett, R., and Strecker, M.R., 2000, Response of intracon- /G34509.1. /j.jsames .2009 .07.008. tinental deformation in the Central Andes to late Ceno- Echavarria, L., Hernandez, R., Allmendinger, R., and Horton, B.K., Hampton, B.A., and Waanders, G.L., 2001, zoic reorganization of South American plate motions: Reynolds, J., 2003, Subandean thrust and fold belt of Paleogene synorogenic sedimentation in the Altiplano Tectonics, v. 19, no. 3, p. 452–467, doi:10.1029 northwestern Argentina: Geometry and timing of the Plateau and implications for initial mountain building /1999TC001102. Andean evolution: The American Association of Petro- in the Central Andes: Geological Society of America Marrett, R.A., Allmendinger, R.W., Alonso, R.N., and leum Geologists Bulletin, v. 87, no. 6, p. 965–985, Bulletin, v. 113, no. 11, p. 1387–1400, doi:10.1130 Drake, R.E., 1994, Late Cenozoic tectonic evolution of doi:10.1306 /01200300196. /0016 -7606 (2001)113 <1387:PSSITA>2.0 .CO;2. the Puna Plateau and adjacent foreland, northwestern Ege, H., Sobel, E.R., Scheuber, E., and Jacobshagen, V., Husson, L., and Sempere, T., 2003, Thickening the Alti- Argentine Andes: Journal of South American Earth 2007, Exhumation history of the southern Altiplano plano crust by gravity-driven crustal channel fl ow: Sciences, v. 7, no. 2, p. 179–207, doi:10.1016 /0895 Plateau (southern Bolivia) constrained by apatite fi s- Geophysical Research Letters, v. 30, no. 5, doi:10.1029 -9811 (94)90007-8. sion track thermochronology: Tectonics, v. 26, no. 1, /2002GL016877. Mazzuoli, R., Vezzoli, L., Omarini, R., Acocella, V., doi:10.1029 /2005TC001869. Husson, L., Conrad, C.P., and Faccenna, C., 2012, Plate Gioncada, A., Matteini, M., Dini, A., Guillou, H., Egenhoff, S., 2007, Life and death of a Cambrian–Ordovician motions, Andean orogeny, and volcanism above the Hauser, N., Uttini, A., and Scaillet, S., 2008, Miocene basin: An Andean three-act play featuring Gondwana South Atlantic convection cell: Earth and Planetary magmatism and tectonics of the easternmost sector of and the Arequipa-Antofalla terrane, in Linnemann, U., Science Letters, v. 317–318, p. 126–135, doi:10.1016 the Calama–Olacapato–El Toro fault system in Cen- Nance, R.D., Kraft, P., and Zulauf, G., eds., The Evo- /j.epsl.2011 .11.040. tral Andes at 24 S: Insights into the evolution of the lution of the Rheic Ocean: From Avalonian-Cadomian Insel, N., Grove, M., Haschke, M., Barnes, J.B., Schmitt, A.K., Eastern Cordillera: Geological Society of America Active Margin to Alleghenian-Variscan Collision: and Strecker, M.R., 2012, Paleozoic to early Cenozoic Bulletin, v. 120, no. 11–12, p. 1493–1517, doi:10.1130 Geological Society of America Special Paper 423, cooling and exhumation of the basement underlying the /B26109.1. p. 511–524. eastern Puna Plateau margin prior to plateau growth: McQuarrie, N., 2002, The kinematic history of the central Elger, K., Oncken, O., and Glodny, J., 2005, Plateau- Tectonics, v. 31, TC6006, doi:10.1029 /2012TC003168. Andean fold-and-thrust belt, Bolivia: Implications for style accumulation of deformation: Southern Alti- Isacks, B.L., 1988, Uplift of the central Andean plateau and building a high plateau: Geological Society of America plano: Tectonics, v. 24, no. 4, TC4020, doi:10.1029 bending of the Bolivian orocline: Journal of Geophysi- Bulletin, v. 114, no. 8, p. 950–963, doi:10.1130 /0016 /2004TC001675. cal Research–Solid Earth, v. 93, no. B4, p. 3211–3231, -7606 (2002)114 <0950:TKHOTC>2.0 .CO;2. Farley, K., 2000, Helium diffusion from apatite: General doi:10.1029 /JB093iB04p03211. McQuarrie, N., Barnes, J.B., and Ehlers, T.A., 2008, Geo- behavior as illustrated by Durango fl uorapatite: Journal Jordan, T.E., and Allmendinger, R.W., 1986, The Sierras metric, kinematic, and erosional history of the central of Geophysical Research–Solid Earth, v. 105, no. B2, Pampeanas of Argentina: A modern analogue of Rocky Andean Plateau, Bolivia (15–17°S): Tectonics, v. 27, p. 2903–2914, doi:10.1029 /1999JB900348. Mountain foreland deformation: American Journal of no. 3, doi:10.1029 /2006TC002054. Galliski, M.A., 1983, Distrito minero El Quemado, Departa- Science, v. 286, no. 10, p. 737–764, doi:10.2475 /ajs Mon, R., and Hongn, F., 1991, The structure of the Pre- mentos La Poma y Cachi, Provincia de Salta: Revista .286 .10.737. cambrian and Lower Paleozoic basement of the Cen- de la Asociación Geológica Argentina, v. 38, no. 2, Jordan, T.E., Isacks, B.L., Allmendinger, R.W., Brewer, tral Andes between 22° and 32°S. Lat.: Geologische p. 209–224. J.A., Ramos, V.A., and Ando, C.J., 1983, Andean Rundschau, v. 80, no. 3, p. 745–758, doi:10.1007 Gehrels, G.E., Valencia, V.A., and Ruiz, J., 2008, Enhanced tectonics related to geometry of subducted Nazca /BF01803699. precision, accuracy, effi ciency, and spatial resolution of plate: Geological Society of America Bulletin, v. 94, Mon, R., and Salfi ty, J.A., 1995, Tectonic evolution of the U-Pb ages by laser ablation-multicollector-inductively no. 3, p. 341–361, doi:10.1130 /0016-7606 (1983)94 Andes of northern Argentina in Tankard, A.J., Suarez- coupled plasma-mass spectrometry: Geochemistry <341:ATRTGO>2.0 .CO;2. Soruco, R., and Welsink, H.J., eds., Petroleum Basins Geophysics Geosystems, v. 9, Q03017, doi:10.1029 Jordan, T.E., Mpodozis, C., Munoz, N., Blanco, N., Pan- of South America: American Association of Petroleum /2007GC001805. anont, P., and Gardeweg, M., 2007, Cenozoic subsur- Geologists Memoir 62, p. 269–283. Gephart, J.W., 1994, Topography and subduction geometry face stratigraphy and structure of the Salar de Atacama Monaldi, C.R., Salfi ty, J.A., and Kley, J., 2008, Preserved in the Central Andes: Clues to the mechanics of a non- Basin, northern Chile: Journal of South American extensional structures in an inverted Cretaceous rift collisional orogen: Journal of Geophysical Research– Earth Sciences, v. 23, no. 2–3, p. 122–146, doi:10.1016 basin, northwestern Argentina: Outcrop examples and Solid Earth, v. 99, no. B6, p. 12,279–12,288. /j.jsames .2006 .09.024. implications for fault reactivation: Tectonics, v. 27, Gerbault, M., Martinod, J., and Herail, G., 2005, Possible Kay, S.M., Ramos, V.A., Mpodozis, C., and Sruoga, P., 1989, no. 1, doi:10.1029 /2006TC001993. orogeny-parallel lower crustal fl ow and thickening in Late Paleozoic to Jurassic silicic magmatism at the Mpodozis, C., and Ramos, V., 1989, The Andes of Chile and the Central Andes: Tectonophysics, v. 399, no. 1–4, Gondwana margin—Analogy to the Middle Proterozoic Argentina, in Ericksen, G.E., Cañas Pinochet, M.T., p. 59–72, doi:10.1016 /j.tecto .2004 .12.015. in North America: Geology, v. 17, no. 4, p. 324–328, and Reinemund, J.A. eds., Geology of the Andes and Grier, M.E., Salfi ty, J.A., and Allmendinger, R.W., 1991, doi:10.1130 /0091 -7613 (1989)017 <0324:LPTJSM>2.3 its Relation to Hydrocarbon and Mineral Resources: Andean reactivation of the Cretaceous Salta rift, north- .CO;2. Houston, Texas, Circum-Pacifi c Council for Energy western Argentina: Journal of South American Earth Kay, S.M., Coira, B., and Viramonte, J., 1994, Young mafi c and Mineral Resources Earth Science Series, p. 59–90. Sciences, v. 4, no. 4, p. 351–372, doi:10.1016 /0895 back-arc volcanic rocks as indicators of continen- Ogg, J.G., Ogg, G., and Gradstein, F.M., 2008, Concise -9811 (91)90007-8. tal lithospheric delamination beneath the Argentine Geologic Time Scale: Cambridge, UK, Cambridge Groshong, R.H., Jr., 1989, Half-graben structures: Bal- Puna Plateau, Central Andes: Journal of Geophysi- University Press. anced models of extensional fault-bend folds: Geo- cal Research–Solid Earth, v. 99, no. B12, p. 24,323– Oncken, O., Hindle, D., Kley, J., Elger, K., Viktor, P., and logical Society of America Bulletin, v. 101, no. 1, 24,339, doi:10.1029 /94JB00896. Schemmann, K., 2006, Deformation of the central p. 96–105, doi:10.1130 /0016 -7606 (1989)101 <0096: Kley, J., and Monaldi, C.R., 1998, Tectonic shortening and Andean upper-plate system: Facts, fi ction, and con- HGSBMO>2.3.CO;2. crustal thickness in the Central Andes: How good is straints for plateau models, in Oncken, O., Chong, G., Hain, M.P., Strecker, M.R., Bookhagen, B., Alonso, R.N., the correlation?: Geology, v. 26, no. 8, p. 723–726, Franz, G., Giese, P., Götze, H., Ramos, V., Strecker, Pingel, H., and Schmitt, A.K., 2011, Neogene to Qua- doi:10.1130 /0091 -7613 (1998)026 <0723:TSACTI>2.3 M., and Wigger, P., eds., Deformation Processes of the ternary broken-foreland formation and sedimentation .CO;2. Andes: Berlin, Springer, v. 1, p. 3–28. dynamics in the Andes of NW Argentina (25°S): Tec- Kley, J., and Monaldi, C.R., 2002, Tectonic inversion in the Pearson, D.M., Kapp, P., Reiners, P.W., Gehrels, G.E., tonics, v. 30, TC2006, doi:10.1029 /2010TC002703. Santa Barbara System of the central Andean foreland Ducea, M.N., Pullen, A., Otamendi, J.E., and

Geosphere, December 2013 1781

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021 Pearson et al.

Alonso, R.N., 2012, Major Miocene exhumation by Salfi ty, J.A., Omarini, R., Baldis, B., and Gutiérrez, W.J., Visión Actual, VIII Congreso de Exploración y Desar- fault-propagation folding within a metamorphosed, 1976, Consideraciones sobre la evolución geológica rollo de Hidrocarburos: Mar del Plata, Instituto Argen- early Paleozoic thrust belt: Northwestern Argen- del Precámbrico y Paleozoico del norte Argentino, in tino del Petróleo y el Gas, p. 1–48. tina: Tectonics, v. 31, no. 4, TC4023, doi:10.1029 Actas 2nd Congreso Ibero-Americano de Geología Starck, D. and Vergani, G., 1996, Desarrollo tectosedi- /2011TC003043. Económica, v. 4, p. 341–361. mentario del Cenozoico en el sur de la Provincia de Petrinovic, I.A., Mitjavila, J., Viramonte, J.G., Martí, J., Salfi ty, J., Monaldi, C., Marquillas, R., and González, R., Salta Argentina: Congreso Geológico Argentino, v. 8, Becchio, R., Arnosio, M., and Colombo, F., 1999, 1993, La inversión tectónica del umbral de Los Gallos p. 433–452. Descripción geoquímica y geocronológica de secuen- en la cuenca del Grupo Salta durante la Fase Incaica: Strecker, M.R., Alonso, R.N., Bookhagen, B., Carrapa, B., cias volcánicas neógenas de Trasarco, en el extremo Mendoza, Argentina, XII Congreso Geológico Argen- Hilley, G.E., Sobel, E.R., and Trauth, M.H., 2007, oriental de la Cadena Volcánica Transversal del Quevar tino y Il Congreso de Exploración de Hidrocarburos, Tectonics and climate of the southern Central Andes: (Noroeste de Argentina): Acta Geologica Hispanica, v. 3, p. 200–210. Annual Review of Earth and Planetary Sciences, v. 35, v. 34, no. 2–3, p. 255–272. Schellart, W.P., Freeman, J., Stegman, D.R., Moresi, L., p. 747–787, doi:10.1146 /annurev .earth .35 .031306 Piñán-Llamas, A., and Simpson, C., 2006, Deformation and May, D., 2007, Evolution and diversity of subduc- .140158. of Gondwana margin turbidites during the Pampean tion zones controlled by slab width: Nature, v. 446, Tankard, A.J., and 17 others, 1995, Structural and tectonic orogeny, north-central Argentina: Geological Society no. 7133, p. 308–311, doi:10.1038 /nature05615. controls of basin evolution in southwestern Gondwana of America Bulletin, v. 118, no. 9/10, p. 1270–1279, Sempere, T., 1995, Phanerozoic evolution of Bolivia and during the Phanerozoic, in Tankard, A.J., Suarez- doi:10.1130 /B25915.1. adjacent regions, in Tankard, A.J., Suarez-Soruco, R., Soruco, R., and Welsink, H.J., eds., Petroleum Basins Ramos, V.A., 2009, Anatomy and global context of the and Welsink, H.J., eds., Petroleum Basins of South of South America: American Association of Petroleum Andes: Main geologic features and the Andean oro- America: American Association of Petroleum Geolo- Geologists Memoir 62, p. 5–52. genic cycle, in Kay, S.M., Ramos, V.A., and Dickin- gists Memoir 62, p. 207–230. Tassara, A., Götze, H.-J., Schmidt, S., and Hackney, R., son, W.R., eds., Backbone of the Americas: Shallow Sempere, T., Butler, R., Richards, D., Marshall, L., Sharp, W., 2006, Three-dimensional density model of the Nazca Subduction, Plateau Uplift, and Ridge and Terrane and Swisher, C., 1997, Stratigraphy and chronology of plate and the Andean continental margin: Journal of Collision: Geological Society of America Memoir 204, Upper Cretaceous–Lower Paleogene strata in Bolivia Geophysical Research–Solid Earth, v. 111, no. B9, p. 31–65–65, doi:10.1130 /2009 .1204(02). and northwest Argentina: Geological Society of Amer- B09404, doi:10.1029 /2005JB003976. Reynolds, J.H., Galli, C.I., Hernandez, R.M., Idleman, B.D., ica Bulletin, v. 109, no. 6, p. 709–727, doi:10.1130 Trauth, M.H., Alonso, R.A., Haselton, K.R., Hermanns, Kotila, J.M., Hilliard, R.V., and Naeser, C.W., 2000, /0016 -7606 (1997)109 <0709:SACOUC>2.3 .CO;2. R.L., and Strecker, M.R., 2000, Climate change and Middle Miocene tectonic development of the Transi- Sempere, T., Carlier, G., Soler, P., Fornari, M., Carlotto, mass movements in the NW Argentine Andes: Earth tion Zone, Salta Province, northwest Argentina: Mag- V., Jacay, J., Arispe, O., Néraudeau, D., Cárdenas, and Planetary Science Letters, v. 179, no. 2, p. 243– netic stratigraphy from the Metan Subgroup, Sierra de J., and Rosas, S., 2002, Late Permian–Middle Juras- 256, doi:10.1016 /S0012 -821X (00)00127-8. Gonzalez: Geological Society of America Bulletin, sic lithospheric thinning in Peru and Bolivia, and its Vandervoort, D.S., Jordan, T.E., Zeitler, P.K., and Alonso, v. 112, no. 11, p. 1736–1751, doi:10.1130 /0016 -7606 bearing on Andean-age tectonics: Tectonophysics, R.N., 1995, Chronology of internal drainage devel- (2000)112 <1736:MMTDOT>2.0 .CO;2. v. 345, no. 1–4, p. 153–181, doi:10.1016 /S0040 -1951 opment and uplift, southern Puna Plateau, Argentine Reynolds, J.H., Hernandez, R.M., Galli, C.I., and Idleman, (01)00211-6. Central Andes: Geology, v. 23, no. 2, p. 145–148, B.D., 2001, Magnetostratigraphy of the Quebrada la Siks, B.C., and Horton, B.K., 2011, Growth and fragmen- doi:10.1130 /0091 -7613 (1995)023 <0145: COIDDA>2.3 Porcelana section, Sierra de Ramos, Salta Province, tation of the Andean foreland basin during eastward .CO;2. Argentina: Age limits for the Neogene Orán Group and advance of fold-and-thrust deformation, Puna Plateau Welsink, H.J., Martinez, E., Aranibar, O., and Jarandilla, J., uplift of the southern Sierras Subandinas: Journal of and Eastern Cordillera, northern Argentina: Tectonics, 1995, Structural inversion of a Cretaceous rift basin, South American Earth Sciences, v. 14, no. 7, p. 681– v. 30, no. 6, TC6017, doi:10.1029 /2011TC002944. southern Altiplano, Bolivia, in Tankard, A.J., Suarez- 692, doi:10.1016 /S0895 -9811 (01)00069-4. Sobel, E.R., Hilley, G.E., and Strecker, M.R., 2003, For- Soruco, R., and Welsink, H.J., eds., Petroleum Basins Riller, U., Petrinovic, I., Ramelow, J., Strecker, M., and mation of internally drained contractional basins by of South America: American Association of Petroleum Oncken, O., 2001, Late Cenozoic tectonism, collapse aridity-limited bedrock incision: Journal of Geo- Geologists Memoir 62, p. 305–324. caldera and plateau formation in the Central Andes: physical Research–Solid Earth, v. 108, no. B7, 2344, Wölbern, I., Heit, B., Yuan, X., Asch, G., Kind, R., Vira- Earth and Planetary Science Letters, v. 188, no. 3–4, doi:10.1029 /2002JB001883. monte, J., Tawackoli, S., and Wilke, H., 2009, Receiver p. 299–311, doi:10.1016 /S0012 -821X (01)00333-8. Sobolev, S.V., and Babeyko, A.Y., 2005, What drives orog- function images from the Moho and the slab beneath Russo, R.M., and Silver, P.G., 1994, Trench-parallel fl ow eny in the Andes?: Geology, v. 33, no. 8, p. 617–620, the Altiplano and Puna Plateaus in the Central Andes: beneath the Nazca plate from seismic anisotropy: Sci- doi:10.1130 /G21557.1. Geophysical Journal International, v. 177, no. 1, ence, v. 263, no. 5150, p. 1105–1111, doi:10.1126 Spiegel, C., Kohn, B., Belton, D., Berner, Z., and Gleadow, p. 296–308, doi:10.1111 /j.1365 -246X .2008 .04075.x. /science.263 .5150 .1105. A., 2009, Apatite (U-Th-Sm)/He thermochronology of Yañez, G.A., Ranero, C.R., von Huene, R., and Diaz, J., Sabino, I.F., 2002, Geología del Subgrupo Pirgua (Cre- rapidly cooled samples: The effect of He implantation: 2001, Magnetic anomaly interpretation across the tácico) del noroeste argentine [PhD thesis]: Universi- Earth and Planetary Science Letters, v. 285, no. 1–2, southern Central Andes (32°–34°S): The role of the dad Nacional de Salta, Argentina, 261 p. p. 105–114, doi:10.1016 /j.epsl .2009 .05.045. Juan Fernandez Ridge in the Late Tertiary evolution Salfi ty, J.A., and Marquillas, R.A., 1994, Tectonic and Starck, D., 1995, Silurian-Jurassic stratigraphy and basin of the margin: Journal of Geophysical Research–Solid sedimentary evolution of the Cretaceous–Eocene Salta evolution of northwestern Argentina, in Tankard, A.J., Earth, v. 106, no. B4, p. 6325–6345, doi:10.1029 Group basin, Argentina, in Salfi ty, J.A., ed., Cretaceous Suarez-Soruco, R., and Welsink, H.J., eds., Petroleum /2000JB900337. Tectonics of the Andes: Wiesbaden, Vieweg Verlag, Basins of South America: American Association of Yuan, X., Sobolev, S.V., and Kind, R., 2002, Moho topog- p. 266–315. Petroleum Geologists Memoir 62, p. 251–267. raphy in the Central Andes and its geodynamic Salfi ty, J.A., and Monaldi, C.R., 1998, Mapa Geológico de la Starck, D., 2011, Cuenca Cretácica-Paleógena del Noroeste implications: Earth and Planetary Science Letters, Provincia de Salta: Buenos Aires, Secretaría de Indus- Argentino, in Kozlowski, E., Legarreta, L., Boll, A., v. 199, no. 3–4, p. 389–402, doi:10.1016/S0012 -821X tria, Comercio, y Minería, scale 1:500,000. and Marshall, P., eds., Simposio Cuencas Argentinas: (02)00589-7.

1782 Geosphere, December 2013

Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1766/3346604/1766.pdf by guest on 29 September 2021