Carrapa, B., Adelmann, D., Hilley, G., Mortimer, E., Strecker, M.R.
Transcription
Carrapa, B., Adelmann, D., Hilley, G., Mortimer, E., Strecker, M.R.
TECTONICS, VOL. 24, TC4011, doi:10.1029/2004TC001762, 2005 Oligocene range uplift and development of plateau morphology in the southern central Andes B. Carrapa,1 D. Adelmann,2 G. E. Hilley,3 E. Mortimer,1 E. R. Sobel,1 and M. R. Strecker1 Received 26 October 2004; revised 14 February 2005; accepted 11 April 2005; published 13 August 2005. [1] The Puna-Altiplano plateau in South America is a high-elevation, low internal relief landform that is characterized by internal drainage and hyperaridity. Thermochronologic and sedimentologic observations from the Sierra de Calalaste region in the southwestern Puna plateau, Argentina, place new constraints on early plateau evolution by resolving the timing of uplift of mountain ranges that bound present-day basins and the filling pattern of these basins during late Eocene-Miocene time. Paleocurrent indicators, sedimentary provenance analyses, and apatite fission track thermochronology indicate that the original paleodrainage setting was disrupted by exhumation and uplift of the Sierra de Calalaste range between 24 and 29 Ma. This event was responsible for basin reorganization and the disruption of the regional fluvial system that has ultimately led to the formation of internal drainage conditions, which, in the Salar de Antofalla, were established not later than late Miocene. Upper Eocene-Oligocene sedimentary rocks flanking the range contain features that suggest an arid environment existed prior to and during its uplift. Provenance data indicate a common similar source located to the west for both the southern Puna and the Altiplano of Bolivia during the late EoceneOligocene with sporadic local sources. This suggests the existence of an extensive, longitudinally oriented foreland basin along the central Andes during this time. Citation: Carrapa, B., D. Adelmann, G. E. Hilley, E. Mortimer, E. R. Sobel, and M. R. Strecker (2005), Oligocene range uplift and development of plateau morphology in the southern central Andes, Tectonics, 24, TC4011, doi:10.1029/ 2004TC001762. 1. Introduction [2] The central Andean Altiplano-Puna plateau is a hyperarid, low internal relief, high-elevation region with 1 Institut für Geowissenschaften, Universität Potsdam, Potsdam, Germany. 2 Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena, Jena, Germany. 3 Department of Earth and Planetary Science, University of California, Berkeley, California, USA. Copyright 2005 by the American Geophysical Union. 0278-7407/05/2004TC001762$12.00 average and peak elevations greater than 3700 and 6000 m, respectively. Uplift of this high-elevation region has been ascribed to processes such as lithospheric thinning [Isacks, 1988] following delamination [Kay et al., 1994], distributed crustal shortening [Allmendinger et al., 1997], emplacement of regional basement thrust sheets [Kley et al., 1997; McQuarrie and DeCelles, 2001], and underthrusting of the Brazilian craton [Isacks, 1988]. Whereas these processes may have created much of the surface uplift in the area, the low-relief morphology, typical of continental orogenic plateaus, may result from simultaneous erosion of high peaks and deposition within basins, as the incising power of regional drainage systems is lost in such arid environments [e.g., Sobel et al., 2003; Hilley and Strecker, 2005]. Despite the importance of internal drainage conditions in many of the world’s large continental plateaus and the potential impact of sediment storage on their evolution as well as adjacent foreland areas [Vandervoort et al., 1995; Métivier et al., 1998; Tapponnier et al., 2001; Horton et al., 2002; Sobel et al., 2003], the controls on their establishment remain elusive. [3] The clastic fill preserved in intramontane basins within the plateau contains the unique record of the timing and pattern of orogenic evolution and its relationship to tectonics and climate. By constraining the sedimentary evolution of such basins and the uplift of related ranges, a better understanding of the processes leading to final internal drainage can be achieved. [4] Clastic sediments preserved in the Puna plateau suggest that sedimentation within the plateau started in the late Eocene in a broad foreland basin sourced from the west [Jordan and Alonso, 1987]. However, detailed sedimentological investigations which could assess this hypothesis are still limited and therefore its validity must be further tested. During the Miocene, and possibly Oligocene, the appearance of evaporites in northern Argentina documents the onset of hyperarid conditions and has been directly related to the establishment of internal drainage in the area [e.g., Vandervoort et al., 1995; Alonso et al., 1991]. Thermochronologic and provenance data from the eastern Puna margin suggest that some topography may have formed as early as the late Eocene – early Oligocene [Muruaga, 2001; Coutand et al., 2001; Deeken et al., 2004]. The eastern ranges constituted a topographic high at least by middle Miocene time [e.g., Strecker, 1987; Strecker et al., 1989; Grier and Dallmeyer, 1990; Marrett and Strecker, 2000; Kleinert and Strecker, 2001; Hilley and Strecker, 2005]. However, the relationships between range exhumation and uplift, sediment dispersal and final internal drainage development remain unclear. TC4011 1 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 plateau or from climate conditions that may be largely independent of plateau formation [e.g., Hartley, 2003; Sobel et al., 2003]. [7] Combined apatite fission track thermochronology (AFTT) and sedimentologic investigations in the southwestern Puna plateau (Figure 1) provide information on the timing of exhumation and related uplift of basinbounding ranges, the sedimentary dynamics within adjacent basins, and climatic conditions during the tectonic events that preceded plateau uplift. In the southern Puna, sedimentary basins that contain upper Eocene to Quaternary sedimentary rocks are bounded by high-angle reverse faults whose hanging wall rocks form bedrock-cored mountain ranges (Figure 2). By constraining the timing of exhumation and related uplift of a bounding range and changes in the sedimentary dynamics of the basins, we suggest that exhumation and uplift of ranges might have been the trigger for basin compartmentalization which eventually led to internal drainage development. Our results support the hypothesis that the deformation driving range uplift started at least by Oligocene time, contributing to the establishment of internal drainage and to the characteristic high elevation, low internal relief observed today within the Puna plateau. 2. Regional Setting 2.1. Tectonic Evolution of the Central Southern Andes Figure 1. General map of the central Andes including different morphotectonic domains and area over 3 km elevation (gray) (modified after Horton et al. [2001]). [5] In addition, constraints on the timing of initiation of deformation related to range uplift and basin compartmentalization within the present plateau area in northwestern Argentina are limited. At present, a widely accepted model proposes that deformation leading to crustal thickening and subsequent uplift occurred during the middle-late Miocene [e.g., Allmendinger, 1986; Isacks, 1988; Allmendinger et al., 1997; Jordan et al., 1997, 2001]. However, subsequent studies document pre-Miocene deformation in the present plateau of Argentina [e.g., Coutand et al., 2001] and Bolivia [McQuarrie and DeCelles, 2001; Horton et al., 2001, 2002; DeCelles and Horton, 2003; Ege, 2004; Elger, 2004]. [6] Extensive studies exist for the Altiplano and Eastern Cordillera of Bolivia documenting an initial pattern of foreland basin development, followed by structural disruption, drainage internalization and compartmentalization of sediment basins during Eocene through early Miocene time [e.g., Horton et al., 2001; Horton et al., 2002; Ege, 2004]. Comparable comprehensive investigations that document the timing and pattern of such processes are scarce in the Puna region. In particular, it remains unclear if deformation driving marginal range uplift, basin compartmentalization and subsequent infill of related sedimentary basins result from tectonic processes that form the [8] The Puna-Altiplano plateau is part of the central Andes and represents the second largest plateau on Earth after Tibet. The southern Puna of northwestern Argentina constitutes the southern end of the intraorogenic plateau. It is bounded to the west by a magmatic arc and to the northeast by the Eastern Cordillera fold-and-thrust belt, while the eastern border is transitional to the high-angle reverse-fault bounded Sierra Pampeanas basement blocks (Figure 1). The 3700-m-high southern Puna plateau is characterized by Neogene contraction [Alonso, 1986; Allmendinger et al., 1997; Coutand et al., 2001; Ege, 2004], meridionally trending mountain ranges (often in excess of 6000 m elevation), and internally draining sedimentary basins. [9] During the late Eocene, contractional to transpressional deformation (‘‘Incaic phase’’ [Steinmann, 1929]) involved Upper Cretaceous to Paleogene rocks of the present Western Cordillera [Günther et al., 1998]. Deformation and uplift of this belt is inferred to have triggered deposition of the earliest clastic sequences in an extensive foreland basin spanning both the present-day plateau and regions to the east [e.g., Jordan and Alonso, 1987; Horton et al., 2001; DeCelles and Horton, 2003]. This model is supported by apatite fission track thermochronology in the Chilean cordillera, indicating considerable exhumation between 50 and 30 Ma [Maksaev and Zentilli, 2000] and by sedimentological data indicating westerly sourced late Eocene-Oligocene sedimentary rocks in the Altiplano [Horton et al., 2002] and possibly in the Puna [Jordan and Alonso, 1987]. Sedimentation continued in isolated intramontane basins that received sediments from more local 2 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 Figure 2. (a) Shaded relief map of the central Andes, based on GTOPO30 data (USGS). AB, Arizaro Basin; AD, Atacama Desert; CA, Campo Arenal; HM, Salar de Hombre Muerto; QT, Quebrada del Toro; H, Humahuaca; SA, Salar de Antofalla; SC, Sierra de Calalaste; Scu, Siete Curvas; Spg, Salar de Pastos Grande; TC, Tres Cruces; VC, Valles Calchaquı́es basin. Faults are modified after Reutter et al. [1994], Urreiztieta et al. [1996], and Coutand et al. [2001]. Dots indicate volcanoes. Star denotes 30.3 ± 3 Ma apatite fission track (AFT) age, after Andriessen and Reutter [1994]; triangle marks AFT ages between 30 ± 2 Ma and 38 ± 3 Ma from Coutand et al. [2001]. (b) Simplified geological map of the central Andes modified after McQuarrie [2002a]. For a more detailed geological map of the study area we refer to Figure 3. sources from at least Miocene until present time [e.g., Jordan and Alonso, 1987; Vandervoort, 1993; Horton et al., 2001; DeCelles and Horton, 2003]. [10] Basins within the plateau contain thick sequences of continental evaporites and clastic deposits that yield fundamental information as to the cooling/exhumation history of hinterland sources, sediment dispersal, and provenance. These basins are bounded structurally by high-angle reverse faults [e.g., Jordan et al., 1997]. The timing of clastic sedimentation in basins within the plateau and along the eastern Puna border is relatively well known based on magnetostratigraphy and 40Ar/39Ar dating on ash layers in synorogenic deposits [Coira et al., 1993; Kay et al., 1994; Marrett and Strecker, 2000; Coutand et al., 2001]. 2.2. Geology of the Sierra de Calalaste Area [11] The study area is located in the southern Puna between the Salar de Antofalla and the Sierra de Calalaste (Figures 2 and 3). Tertiary E-W to WNW-ESE shortening produced a series of east and west vergent reverse and thrust faults striking parallel to the present Salar de Antofalla (Figure 4) [Voss, 2000; Adelmann, 2001]. The Sierra de Calalaste constitutes low-grade metamorphic basement rocks that were deformed during and after late Eocene time [Adelmann, 2001]. Within the Sierra de Calalaste, Paleozoic sedimentary rocks are thrust over Tertiary sedimentary rocks along west and east verging reverse faults (Figure 3). Crystalline basement rocks, including migmatitic gneisses, metabasites, granitoids and aplites, as well as Tertiary volcanics rocks crop out to the west and southwest of the present-day Salar de Antofalla area [e.g., Kraemer et al., 1999, and references therein] (Figures 2 and 3). In contrast, Precambrian sedimentary and low-grade metamorphic rocks are more widespread to the east (Figures 2 and 3). [12] In the study area, sedimentation started in late Eocene – early Oligocene time with the deposition of the Quiñoas Formation during the Incaic deformation phase [e.g., Kraemer et al., 1999; Adelmann, 2001; Voss, 2002]. During the late Oligocene, thick-skinned compressive deformation [Adelmann and Görler, 1998] triggered sedimentation of syntectonic coarse-grained alluvial fans constituting the Chacras Formation (Figure 4). This phase of 3 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 3. Detailed geologic map of the Antofalla area [see Kraemer et al., 1999] with location of the analyzed samples and sedimentological logs. 4 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 Figure 4. Overview of the tectonostratigraphic and magmatic development of the Salar de Antofalla area in the southern Puna modified after Kraemer et al. [1999], Voss [2000], and Adelmann [2001]. Undulated lines represent angular unconformities of regional significance separating main lithostratigraphic units present in the Salar de Antofalla area. early deformation is also marked by an angular unconformity between the Quiñoas and the Chacras formations. Immediately beneath the unconformity, a tuff layer yields an 40Ar/39Ar age of 28.9 ± 0.8 Ma (ID-51) [Adelmann and Görler, 1998]. The oldest strata of the overlying Chacras Formation have been dated at 24.2 ± 0.9 Ma (ID-86) and 22.5 ± 0.6 Ma (ID-18) [Kraemer et al., 1999]. [13] During the early Miocene (20– 17 Ma), renewed E-W to WNW-ESE shortening [Adelmann and Görler, 1998] reactivated the west vergent fault system that was active during the preceding deformation phase. Additionally, Miocene shortening produced new east and westward directed basement thrusts onto tilted alluvial fan sediments of the Potrero Grande Formation [Adelmann, 2001]. In the middle Miocene, west vergent thrusts affected Lower Paleozoic, Permian and Tertiary rocks [Adelmann, 1997; Voss, 2000; Adelmann, 2001]. This deformation triggered deposition of the syntectonic Juncalito Formation (middle Miocene-Pliocene) which is characterized by thick evaporites (dated as late Miocene [Kraemer et al., 1999]) typical of a hyperarid internal drainage environment [Kraemer et al., 1999]. 3. Methods [14] Sediment logging, facies interpretation, paleocurrent and provenance analyses were carried out on upper Eocene – lower Miocene sedimentary rocks (Quiñoas and Chacras formations) to reveal changes in sediment source and sedimentary environments (Figures 5 and 6 and Table 1). Fifteen thin sections were analyzed using the Gazzi-Dickinson method [Dickinson, 1970; Gazzi et al., 1973]. An average of 400 framework grains per thin section was counted on unstained thin sections. Petrographic counting parameters and recalculated detrital modes are reported in Table 2. Paleocurrent direction was determined by measuring at least 5 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 Figure 5. Correlation panel of the investigated sedimentological logs indicated in Figure 3. For more details, refer to Figure 6. 50 imbricated pebbles of clast-supported channelized streamflow and proximal sheet flood units in alluvial fan deposits. [15] AFTT was conducted on six samples collected along a vertical transect through the Sierra de Calalaste between elevations of 3729 and 4455 m to constrain the cooling and exhumation history of the central part of the range. Samples were separated and analyzed following the procedure described by Sobel and Strecker [2003] (Table 3). Raw data were reduced using the Trackkey program (I. Dunkl, Trackkey: Windows program for calculation and graphical presentation of EDM fission track data, version 4.2, 2002, available at http://www.sediment.uni-goettingen.de/staff/ dunkl/software/trackkey.html). Measurements of fission track etch pits were made to assess annealing kinetic variability [Donelick et al., 1999]. Length measurements were attempted on all samples in order to gain information on the degree of annealing [e.g., Wagner and Van der Haute, 1992]. Exhumation rate was calculated using the inverse slope of weighted least squares regression of the AFT elevation versus ages. 4. Sedimentology 4.1. Quiñoas Formation [16] The Quiñoas Formation records the onset of sedimentation in the study area in the late Eocene as determined by an 40Ar/39Ar age of 37.6 ± 0.3 obtained from an ash layer in the basal part of the formation [Kraemer et al., 1999]. The Quiñoas Formation is divided into two members based on facies associations and a change in the interpreted depositional environments [Kraemer et al., 1999]. 6 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 6. Detailed sedimentological logs: (a) log R; (b) log U; (c) log G; (d) log H/I; (e) log S. Ages indicated in log U are from Kraemer et al. [1999]. For legend, refer to Figure 5. The most typical facies are indicated in italics. For a description of the facies we refer to Table 1. 7 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 6. (continued) 8 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 6. (continued) 9 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 6. (continued) 10 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 6. (continued) 11 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 Table 1. Lithofacies Description and Interpretation Based on Work by Miall [1996] Facies Codes Gm Lithofacies Fl conglomerates, matrix supported conglomerates, clast supported conglomerates, clast supported conglomerates, clast supported sand, fine to coarse sand, fine to very coarse, may be pebbly sand, fine to very coarse, may be pebbly sand, fine to very coarse, may be pebbly sand, very fine to coarse sand, fine to medium, well sorted sand, silt, mud Fsm/m P silt, mud paleosol carbonate Gc Gh Gt/p Sm St Sp Sh/l Sr Seod Sedimentary Structures Interpretation massive, faint gradation high-strength (cohesive) debris flow massive, faint horizontal laminations, imbrications horizontal laminations, imbrications high-strength or low-strength (noncohesive) debris flow longitudinal gravel banks, lag deposits trough and planar cross beds minor channel fills, transverse bed forms massive or faint lamination trough cross beds distal debris flow subaqueous 3-D dunes, Transition or upper part of a flow regime subaqueous 2-D dunes planar cross beds horizontal laminations/low-angle (<15) cross beds ripple, cross lamination large-scale cross lamination (>25) fine laminations, very small ripples massive, desiccation cracks pedogenic features: nodules filaments 4.1.1. Quiñoas I [17] This member is deposited above an erosional unconformity with the underlying Permo-Carboniferous rocks. At its maximum recorded thickness, this member reaches 840 m. It is characterized by fine-grained, gypsiferous siltstones and mudstones (Fsm/m, Fl) intercalated with massive, horizontally stratified and imbricated conglomerates with undulating basal contacts (Gc); lenticular clastsupported conglomerates (Gt/p); and interbedded massive and laminated sandstones (Sh/l, Sm) (Table 1). Combined thicknesses of conglomerate units can exceed 250 m (Figure 5). In the farthest sections to the west (logs U and R), these fine grained facies dominate the sections, while more proximal to the Sierra de Calalaste the section is coarser and dominated by the conglomeratic facies, though still with intercalated finer horizons (Figure 5). [18] We interpret the gypsiferous siltstones and mudstones (Fsm/m, Fl) as being deposited in a playa mudflat [e.g., Flint, 1985; Hartley et al., 1992]. The presence of fine grained, laminated sediments, often bioturbated and with rooting and soil remnants and gypsum, is indicative of an arid, or at least episodically dry environment [e.g., Hardie et al., 1978]. The coarse-grained lenticular conglomerates (Gt/p) are interpreted as having been deposited in fluvial channels [e.g., Hartley et al., 1992; Miall, 1996]. Massive, bedded and imbricated conglomerates (Gc) are interpreted to have been deposited under tractive flow [Rasmussen, 2000]. Horizontally stratified conglomerates (Gh) might reflect discontinuous discharge and accretion during high-density flows and sheet floods [Nemec and Steel, 1984]. The interbedded, laminated and massive sandstones (Sh/l, Sm) which occur both within the conglomerates and throughout the finer-grained section represent waning flow conditions and are probably distal derivatives of debris flows on the alluvial fan [e.g., Lowe, 1979; Nemec and Steel, 1984]. This scour fills ripples (lower flow regime) aeolian dunes overbank, abandoned channel or waning flood deposits overbank, abandoned or drape deposits soil with chemical precipitation facies association is typical of ephemeral discharge in semiarid to arid alluvial fan environment [e.g., Flint and Turner, 1988; Sohn, 1997; Rasmussen, 2000]. Paleocurrent data from member I, on the west side of the present-day Sierra de Calalaste, suggest a provenance mainly from the N-NE and S-SW (Figure 3). 4.1.2. Quiñoas II [19] This member reaches a thickness of about 500 m adjacent to the Sierra de Calalaste (Figures 5 and 6; log G) and conformably overlies the underlying member. It comprises fine to very coarse-grained, trough cross-bedded sandstones and pebbly sandstones (St). These occur in beds between 0.5 and 5.0 m thickness. Vertically stacked beds of this facies can combine to form significant thicknesses of more than 100 m (e.g., log G, U). Alternating with these larger coarse-grained units are finer-grained sandstones (decimeter-scale beds) with scoured bases and occasional climbing ripples occurring in many of the sandstone units (Sr) and mudstones (Fsm/m, Fl) (Table 1). These mudstones often contain desiccation cracks, and are bioturbated (e.g., Figure 6b, log U). [20] We interpret the trough cross-bedded sandstones as being derived from the migration of dune bed forms within sand bed channels of a fluvial depositional environment [Miall, 1996]. Scour based sandstones with climbing ripples represent a lower flow regime within a fluvial environment [e.g., Allen, 1963]. The mudstones represent the finest component of the system, and are likely to have been deposited onto a floodplain environment, possibly through crevasse splay deposition. The close vertical association between channel and floodplain deposits suggests deposition onto a fluvial plain [Miall, 1996]. Such a facies association might be representative of either meandering or braided river systems [Miall, 1978; Smith, 1987]. However, because of the significant thicknesses of trough cross- 12 of 19 13 of 19 Quiñoas Quiñoas Quiñoas Quiñoas Quiñoas Quiñoas Quiñoas Quiñoas Fm Fm Fm Fm Fm Fm Fm Fm I I I I I I I I log log log log log log log log S S R R H/I H/I H/I H/I G H/I H/I S S log log log log log II II II II II Quiñoas Quiñoas Quiñoas Quiñoas Quiñoas Fm Fm Fm Fm Fm log G log G mS mS mS mS mS mS mS mS mS/cS mS mS mS mS mS mS Qp 21.8 39 22.5 19.1 18.4 16.3 18.4 28.3 26.7 21.0 25.7 42.8 30.0 29.1 14.0 6.9 6.9 6.1 11.9 9.6 19.5 9.9 13.6 13.5 13.9 11.8 20.5 5.6 15.6 11.5 Mean Locationb Grain Sizec Qm Chacras Fm Chacras Fm Stratigraphy 3.8 5.8 5.1 9.1 5.9 4.2 4.3 1.9 6.3 3.2 6.1 3.9 5.8 4.5 4.9 16.0 11.6 14.4 17.7 23.5 22.2 12.0 9.3 20.2 13.6 16.6 13.1 11.3 16.5 29.2 Plag K-Feldspar Lv 2.6 3.6 2.9 1.7 2.7 2.9 12.8 11.3 0 6.4 1.1 1.9 3.2 4.4 2.4 6.7 6.7 5.1 8.6 2.9 1.9 9.3 1.7 11.0 1.7 0.0 0.2 0.0 0.8 0.9 0.8 0.6 4.1 5.0 7.6 8.4 4.3 7.9 3.2 1.7 3.7 2.1 4.4 4.2 5 2.7 1.9 0.9 1.1 0.5 1.0 1.9 4.0 1.3 0.8 2.3 0.8 1.4 0.3 0.5 0.8 1.9 0 0.8 0 0.5 0 1.1 0.5 1.9 0.6 0.5 1.4 0.3 0 1.1 0.8 4.1 3.6 14.7 16.7 9.3 7.3 6.1 5.2 2.6 7.2 4.1 2.2 8.4 6.9 4.4 9.6 12.7 17.6 10.0 15.5 10.1 20.0 6.9 3.4 9.4 7.5 14.2 18.2 8.8 0.6 32 29 31 2 40 42 46 68 57 51 12 60 65 44 36 33 36 39 56 46 12 Chert Minor Lp Fragments Constituents Mica Cement Matrix Q 6.7 0.5 7.7 0 Lm 2.6 14.8 5.1 2.0 1.3 10.6 13.3 3.7 6.9 5.0 6.1 1.4 1.7 0.8 1.9 0.8 3.4 1.6 3.2 0.8 11.2 14.4 4.1 17.5 Ls 25 37 31 8 29 20 26 20 24 24 4 23 21 29 37 40 34 22 13 27 9 F 43 34 39 6 31 38 28 11 19 25 11 17 14 27 27 27 30 39 31 27 8 L 25 17 21 6 29 25 30 52 41 35 11 26 47 34 27 25 21 25 33 30 8 Qm 25 37 31 8 29 20 26 20 24 24 4 23 21 29 37 40 34 23 13 28 9 F 50 46 48 3 42 54 43 28 35 40 10 51 32 37 36 35 45 52 54 43 9 24 38 31 10 44 57 60 88 77 65 17 93 80 70 79 53 63 47 62 68 15 43 50 47 5 48 38 17 4 7 23 19 0 5 16 12 34 28 7 5 13 12 33 12 23 15 8 5 23 8 16 12 7 7 15 14 9 13 9 47 33 18 14 Lt Qp Lvm Lsm a Recalculated detrital modes are reported for QFL, Qm, monocrystalline quartz; Qp, polycrystalline quartz; Plag, plagioclase; Ls, sedimentary rock fragments; Lv, volcanic rock fragments; Lm, metamorphic rock fragments; Lp, plutonic rock fragments. Q, F, L, Lt, Lvm, and Lsm are parameters based on the classification of Dickinson [1970] and Graham et al. [1976]. SD, standard deviation. b Location is given in Figures 5 and 6. c Here mS is middle sandstone and cS is coarse sandstone. A091 A092 Average SD A075 A081 A082 A443 A444 Average SD A442 A441 A412 A411 A090 A100 A103 A108 Average SD Sample Table 2. Sandstone Petrography Parameters Based Methods Described by Ingersoll et al. [1984] and Dickinson [1985]a TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 a 0.2 0.1 0.2 0.1 0.1 0.1 2.2 2.0 2.0 2.1 1.9 2.0 67.4215 67.4819 67.4516 67.4527 67.4606 67.4609 metasediments metasediments metasediments metasediments metasediments metasediments SCAD9 SCAD5 SCAD6 SCAD2 SCAD4 SCAD3 3729 3978 4248 4328 4335 4455 26.1436 26.1618 26.1356 26.1356 26.1526 26.1501 19 6 9 20 20 20 5.176 4.206 3.196 4.519 3.227 2.500 327 57 67 300 252 175 46.711 36.232 31.678 38.528 26.699 22.843 2951 491 664 2558 2085 1599 88 82 62 82 100 46 12.493 12.821 12.739 13.076 12.903 12.985 5166 5166 5166 5166 5166 5166 25.8 27.7 23.9 28.5 29.0 26.5 1.6 3.9 3.1 1.8 2.0 2.2 47 34 30 36 26 23 SD Dpar, mm U, ppm ±1s Age, Ma NDg Rho-D,f 105 P(c)2,e % NId Rho-I,c 105 NSd Rho-S,c 105 Number of Xlsb Longitude, decimal degrees Latitude, decimal degrees Elevation, m Lithology Sample Table 3. AFT Dataa Samples are analyzed with a Leica DMRM microscope with drawing tube located above a digitizing tablet and a Kinetek computer-controlled stage driven by the FTStage program [Dumitru, 1993]. Analysis is performed with reflected and transmitted light at 1250X magnification. Samples were irradiated at Oregon State University. Samples were etched in 5.5 molar nitric acid at 21C for 20 s. Following irradiation, the mica external detectors were etched with 21C, 40% hydrofluoric acid for 45 min. The pooled age is reported for all samples as they pass the c2 test. Error is one sigma, calculated using the zeta calibration method [Hurford and Green, 1983] with zeta of 373.2 ± 6.1 for apatite (B. Carrapa). Dpar, fission track etch pit measurements; SD, the related standard deviation. b Number of Xls is the number of individual crystals dated. c Rho-S and Rho-I are the spontaneous and induced track density measured, respectively (tracks/cm2). d NS and NI are the number of spontaneous and induced tracks counted, respectively. e P(c)2 is the chi-square probability [Galbraith, 1981; Green, 1981]. Values greater than 5% are considered to pass this test and represent a single population of ages. f Rho-D is the induced track density in external detector adjacent to CN5 dosimetry glass (tracks/cm2). g ND is the number of tracks counted in determining Rho-D. CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 TC4011 bedded sandstones, climbing ripples and minor interbedded mud silt components we interpret this association as typical of sheet flood and distal braided environments [Miall, 1978]. 4.2. Chacras Formation [21] Separated locally by an erosional unconformity, the Quiñoas Formation is overlain by the 24.2 ± 0.9 to 22.5 ± 0.6 Ma Chacras Formation [Kraemer et al., 1999] that is deposited to the west and east of the Sierra de Calalaste (Figures 5 and 6). At its maximum recorded thickness, this member reaches 650 m. At the southern end of Sierra de Calalaste, the Chacras Formation is missing. [22] The Chacras Formation is dominated by laterally continuous, massive, stratified and imbricated conglomerates (Gc, Gh) and lenticular conglomerates (Gt/p). Clasts within the conglomerates are angular to subangular, and there are frequently boulders throughout. These conglomerates are interbedded with medium to coarse-grained crossbedded, and planar-bedded sandstones (St, Sp), and massive sandstones (Sm) (Table 1). In the upper 150 m of log U (Figure 6b) large-scale (5 – 10 m) cross sets of mediumgrained sandstones are preserved with foreset dips of 15– 25 that reach a combined thickness of up to 50 m. [23] We interpret the lenticular conglomerates (Gt/p) as resulting from deposition in shallow, gravely, bed load channels, with planar stratification and imbrication (Gc, Gh) occurring due to tractional flow at the channel bases [e.g., Nemec and Steel, 1984]. Planar bedded conglomerates also probably result from high-density flows during highdischarge events [Smith, 1987; Flint and Turner, 1988; Adelmann, 2001] and variations in the amount of accumulation [Nemec and Steel, 1984]. The interbedded sandstones are deposited from high-density flows during waning conditions [Rasmussen, 2000]. Such a close spatial relationship between lenticular and planar conglomerates, and interbedded sandstones is typical of deposition through changing flow regimes on a shallow gravel braided streams on an alluvial fan [Miall, 1996]. The subangular clasts and presence of boulders indicate a proximal source for these deposits. The large-scale, cross-bedded sandstones are interpreted as eolian dunes and exhibit geometries that are typical of modern day examples [e.g., Hunter, 1977; Reading, 1996], suggesting that at this time deposition occurred in an arid environment. Paleocurrent data from these sediments, on the east side of the present-day Sierra de Calalaste, suggest a provenance mainly from the W-NW (Figure 3). 4.3. Potrero Grande Formation [24] The lower to middle Miocene Potrero Grande Formation unconformably overlies the Chacras Formation. There are a series of interbedded tuffs that occur within this formation, and the oldest tuff has a 40Ar/39Ar age of 18.0 ± 0.9 Ma [Kraemer et al., 1999]. A maximum thickness of 300 m was estimated west of the Salar de Antofalla [Adelmann, 2001]. Adjacent to the Sierra de Calalaste, the Potrero Grande Formation consists of 150 m of conglomerates, conglomeratic sandstones, and sandstones that are interpreted as having been deposited in an 14 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES alluvial fan environment [Kraemer et al., 1999]. Paleoflow indicators within this formation show large variations in direction with a scattered pattern (Figure 5) [Kraemer et al., 1999]. Here, we focus on the early evolution of the Sierra de Calalaste region. The Potrero Formation documents the later evolution, and as such we do not document it in detail here but refer the reader to Kraemer et al. [1999] for further discussion. 5. Provenance [25] Sandstone petrography for members I and II of the Quiñoas Formation show a lithic-feldspatic to feldspaticlithic composition (Figure 7a) with an increase in quartz fragments, shown in the QFL and QmFLt diagrams, an up sequence typical of an evolution toward a more crystalline source. The Qp, Lvm, Lsm diagram shows a generally quartz rich composition for these sediments (Figure 7c). [26] The only two samples available for the Chacras Formation have a lithic-feldspatic composition suggesting a different composition compared to the Quiñoas sediments (Figures 7a and 7b). Despite the limited number of samples available, the greater contribution from volcanic and sedimentary-metamorphic rocks typical of the Sierra de Calalaste range (Figure 7c) expressed by these two samples, is consistent with paleocurrent data measured east of Sierra de Calalaste, indicating an eastward direction and in turn a source located in this range (Figure 3). 6. AFTT Data [27] All analyzed fission track samples show comparable results within one standard deviation, with ages ranging between 24 ± 3 and 29 ± 1 Ma (Figure 8 and Table 3). Only limited lengths were available in sample SCAD3 (Table 3), giving a mean length of 12.98 ± 0.56 mm and suggesting that partial annealing was not significant. Etch pit measurements indicate that the samples are monocompositional, suggesting a homogeneous closure temperature. The ageelevation pattern of the Sierra de Calalaste vertical profile points to an exhumation rate of 0.3mm/yr, which is consistent with rates obtained in neighboring ranges to the north [Deeken et al., 2004]. 7. Discussion and Conclusions [28] Our multiple data sets show that sedimentation commenced during the late Eocene – early Oligocene with the deposition of the Quiñoas sediments in a partially segmented foreland basin with sediments derived mainly from the west, and with contribution from proximal sources. The general trend in the petrographical data for the Quiñoas Formation indicates an increase in Qz up sequence (Figure 7). This could be explained by an evolution of the source toward more crystalline inputs. Crystalline sources are generally typical of areas to the west (Figure 7c). Also, the timing of the deposition of the Quiñoas formation corresponds to the end of the exhuma- TC4011 tion episode in the Domeyko Cordillera in northern Chile, composed of granite and granodiorite, between 50 and 30 Ma [Maksaev and Zentilli, 2000]. This clear association between the onset of exhumation of the Chilean Cordillera and the deposition of the Quiñoas Formation, and the sandstone provenance data would indicate that the dominant input to sedimentation was from the west. However, the presence of coarse grained clastic sediments with more variable paleocurrent directions in member I of the Quiñoas Formation would suggest that the foreland basin system seen during Quiñoas time was probably already partially segmented by proximal highlands. These areas provided a local, and minor sediment source, e.g., plutonic bodies located immediately to the NW of the study area or even part of the Sierra de Calalaste to the east (Figure 3) [Kraemer et al., 1999]. Also, late Eocene – early Oligocene apatite fission track cooling ages have been reported to the east-southeast of the study area [Coutand et al., 2001] introducing the possibility that there may have been some topography to the east at this time that was responsible for the compartmentalization of the foreland. In this respect it is interesting that Horton et al. [2002] proposed that the Eastern Cordillera of southern Bolivia was a source of the Altiplano sediments during the Paleocene and OligoMiocene. The western flank of the Eastern Cordillera was strongly deformed during the paleogene by west vergent backthrusts [McQuarrie and DeCelles, 2001; McQuarrie, 2002b]. The Eastern Cordillera continues southward along strike into the Puna plateau, and this range is a candidate source for the investigated sediments (Figure 7). [29] However, to date, no clear sedimentological and thermochronological evidence exists that the Eastern Cordillera provided detritus to the west into the Puna at this time. Furthermore, the metamorphic and volcanic lithic fragments that would be characteristic of the Sierra de Calalaste and in general of more eastern and southeastern sources [e.g., Reutter et al., 1994] are exceedingly scarce in the Quiñoas sandstone, suggesting that such sources, if present, were not contributing to sandstone detritus. Also, recent AFTT on granitic rocks from eastern and northeastern areas in the Puna suggest that the nearest ranges were exhuming later than the deposition of the Quiñoas sediments by 20 Ma [Deeken et al., 2004]. In light of the presently available data we cannot rule out the possibility that the eastern boundary of the Puna might have constituted some topographic high already during the late Eocene –early Oligocene [e.g., Coutand et al., 2001; Horton et al., 2002]. [30] Interestingly, during the late Eocene, the local gypsum and anhydrite layers within the lower Quiñoas Formation (member I), and their association with evaporitic playa mud flats, suggest that at least a seasonal arid environment existed. This arid environment may have resulted from deformation and uplift of the Chilean Cordillera [Maksaev and Zentilli, 2000], which might have shielded the southern Puna from occasional moisture incursions at a time when the cold Humboldt current had not been fully established and thus provided sufficient moisture to generate precipitation [Alpers and Brimhall, 1988]. In addition to regional climatic effects, the prolonged aridity seen in the Calalaste 15 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES Figure 7. Main sandstone compositions of the investigated sediments: (a) QFL diagram based on the technique described by Dickinson [1970]. Q, monocrystalline and polycrystalline quartz; F, feldspar; L, sedimentary, metasedimentary, and volcanic lithic fragments including chert. Gray area represents the compositional field of the late Eocene-Oligocene Potoco sedimentary rocks from the Altiplano sourced from the Western Cordillera (sections 1– 2; after Horton et al. [2002]). (b) QmFLt diagram based on the technique described by Graham et al. [1976]. Qm, monocrystalline quartz; F, feldspar; Lt, sedimentary, metasedimentary, and volcanic, lithic fragments including polycrystalline quartz and chert. (c) QpLvmLsm diagram based on the technique described by Graham et al. [1976]. Qp, polycrystalline quartz; Lvm, volcanic lithics; Lsm, metamorphic lithics. 16 of 19 TC4011 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES TC4011 Figure 8. AFT vertical profile and length histogram related to sample SCAD 3. area may also have been further supported by the potential topographic culminations of the Eastern Cordillera at least by early Miocene time [Deeken et al., 2004]. [31] At a broader scale, time-equivalent clastic sedimentary rocks (Potoco Formation) deposited in the Bolivian Altiplano and sourced from the Western Cordillera show very similar facies associations in turn suggesting a similar sedimentary environment [Horton et al., 2002]. It is important to acknowledge however, that the Altiplano provenance data were obtained from localities hundreds of kilometers to the north of the study area. In any case, similarities between these units may indicate that an extensive longitudinally oriented basin, with local highlands, existed during the late Eocene – early Oligocene that spanned the length of the central Andes. In such a scenario, the Quiñoas Formation may represent a part of a semicontinuous foreland basin located to the east of the Eocene Incaic mountain belt. [32] The overlying upper Oligocene – lower Miocene Chacras Formation shows a change in sediment dispersal and facies association, with a marked coarsening compared to the Quiñoas Formation, and paleocurrent and petrographic data that suggest input from the Sierra de Calalaste. Despite the fact that paleocurrent measurements within the Chacras Formation are only available along the eastern margin of the range, these data unequivocally indicate a source from the Sierra de Calalaste. [33] AFTT data show that exhumation of the range occurred between 24 and 29 Ma, which is the time of deposition of the late Quiñoas and early Chacras formations (28.9 ± 0.8 Ma; 24.2 ± 0.9 [Kraemer et al., 1999]). Therefore we propose that the observed change in sediment dispersal is a direct response to the uplift and erosion of the Sierra de Calalaste range, which must have had a profound effect on the fluvial systems within adjacent basins during the Oligocene. Finally, the facies association with the presence of extensive eolian dunes within this formation suggests that the arid climate established prior to or during Quiñoas time persisted during Chacras time. [34] In Sierra de Calalaste and adjacent basins, uplift resulting from Oligocene deformation led to reorganization of the depositional systems within the present-day Salar de Antofalla area. Paleocurrent and sandstone provenance data show that the depositional system, originally mainly sourced from western crystalline rocks, was reorganized during the Oligocene. This reorganization was contemporaneous with deformation within the Sierra de Calalaste, suggesting a causal linkage between uplift of the range and response of the adjacent basin. At least transient internally drained conditions existed during depositions of the Quiñoas sediments though it is less clear if such conditions were present during the deposition of the Chacras sediments. However, the occurrence of thick evaporite units in the late Miocene (Juncalito Formation [Kraemer et al., 1999]) indicates that the Salar de Antofalla basin was internally drained by that time. Therefore we suggest that the basin reorganization seen between the Quiñoas and Chacras formations heralded the beginning of the process of disruption of the regional fluvial system that may have ultimately led to the formation of internal drainage. [35] Many workers have documented deformation possibly driving range uplift and a transition from external to internal drainage within basins of the Puna plateau in Oligo-Miocene time [e.g., Alonso, 1986; Jordan and Alonso, 1987; Marrett, 1990; Alonso et al., 1991; Coira et al., 1993; Vandervoort, 1993]. Around 23S latitude, the Salinas Grandes and Tres Cruces basins contain evidence of deformation beginning in the late Eocene to early Oligocene [Coutand et al., 2001]. At 24S latitude, internal drainage at Siete Curvas may have formed as early as the late Oligocene and certainly by late Miocene time [Vandervoort et al., 1995], whereas to the west internal drainage within the Arizaro and Tolar Grande basins commenced no later than early Miocene time [Donato, 1987; Coutand et al., 2001], 17 of 19 TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES and early to middle Miocene [Vandervoort et al., 1995], respectively. Within the Salar de Pastos Grandes to the west of Siete Curvas, thick evaporites show that internal drainage formed sometime between 11.2 Ma and perhaps as early as the late Eocene – early Oligocene [Alonso et al., 1991]. Within the Salar de Hombre Muerto area at 25S latitude, evaporite deposition started by 15.0 ± 1.2 Ma, and internal drainage may have been established as early as the Oligocene [Alonso et al., 1991; Vandervoort et al., 1995]. In the same region the termination of supergene copper mineralization indicates that hyperaridity was established after 14.7 Ma [Alpers and Brimhall, 1988]. Finally, in the Campo Arenal area along the present Puna margin at 27S latitude, AFTT data indicate that deformation had begun between 29 and 38 Ma [Coutand et al., 2001]. [36] In summary, these observations suggest that deformation, exhumation of basement ranges, and the establishment of internal drainage within the Puna plateau were spatially diachronous [e.g., Vandervoort, 1993; Coutand et al., 2001]. In particular, the timing of the onset of internal drainage in the area may be dependent on the details of the uplift of discrete mountain ranges that may be controlled by local structural or volcanic conditions [Segerstrom and Turner, 1972; Alonso, 1986]. Combined with our new data TC4011 set, this suggests that deformation driving uplift within the Puna may not have occurred progressively from west-toeast as previously suggested [e.g., Andriessen and Reutter, 1994] and that the establishment of internal drainage may not only have been dependent on local details of marginal range uplift but also on the history of the uplift of ranges farther upwind. [37] At a more regional scale, our new data show that deformation and uplift of the southern Puna plateau started already in Oligocene time, if not earlier, and contributed to the fragmentation and paleodrainage reorganization of an earlier semicontinuous foreland basin. This event occurred in an already arid climate environment, and created the ideal morphotectonic preconditions for the establishment of the subsequent internal drainage environment that was in place no later than middle Miocene time. [38] Acknowledgments. Deutsche Forschungsgemeinschaft (DFG) and the Alexander von Humboldt Foundation are kindly acknowledged for financial support through grants to M. Strecker and B. Carrapa, respectively. Peter DeCelles, Teresa Jordan, Brian Horton, and an anonymous reviewer are kindly thanked for constructive reviews of this manuscript. Also, we thank R. Marrett and R. Alonso for their help during sample collection and logistics. References Adelmann, D. (1997), Thrust tectonic controls on late Tertiary sedimentation patterns in the Salar de Antofalla are (NW Argentina), Bol. Soc. Venezolana Geol., 1, 7 – 13. Adelmann, D. (2001), Känozoische Beckenentwicklung in der südlichen Puna am Beispiel des Salar de Antofolla (NW-Argentinien), Ph.D. thesis, 180 pp., Freie Univ. Berlin, Berlin. Adelmann, D., and K. Görler (1998), Basin development in the southern Puna: sedimentary record from the Salar de Antofalla area, NW Argentina, in Actas del X Congreso Latinoamericano de Geologı́a, vol. I, p. 26, Buenos Aires. Allen, J. R. L. (1963), The classification of crossstratified units, with notes on their origin, Sedimentology, 2, 93 – 114. Allmendinger, R. W. (1986), Tectonic development, southeastern border of the Puna plateau, northwestern Argentine Andes, Geol. Soc. Am. Bull., 97, 1070 – 1082. Allmendinger, R., T. Jordan, S. Kay, and B. Isacks (1997), The evolution of the Altiplano-Puna plateau of the central Andes, Annu. Rev. Earth Planet. Sci., 25, 139 – 174. Alonso, R. N. (1986), Occurencia, posición estratigráfica y génesis de boratos de la Puna Argentina, Ph.D. thesis, 196 pp., Univ. Nac. de Salta, Salta, Argentina. Alonso, R. N., T. E. Jordan, K. T. Tabutt, and D. S. Vandervoort (1991), Giant evaporite belts of the Neogene central Andes, Geology, 19, 401 – 404. Alpers, C. N., and G. H. Brimhall (1988), Middle Miocene climatic change in the Atacama Desert, northern Chile: Evidence from supergene mineralization at La Escondida, Geol. Soc. Am. Bull., 100, 1640 – 1656. Andriessen, P., and K. J. Reutter (1994), K-Ar and fission track mineral age determinations of igneous rocks related to multiple magmatic arc systems along the 23S Latitude of Chile and Argentina, in Tectonics of the Southern Central Andes, edited by K.-J. Reutter, E. Scheuber, and P. Wigger, pp. 141 – 153, Springer, New York. Coira, B., S. M. Kay, and J. Viramonte (1993), Upper Cenozoic magmatic evolution of the Argentina Puna: A model for changing subduction geometry, Int. Geol. Rev., 35, 677 – 720. Coutand, I., P. R. Cobbold, M. de Urreiztieta, P. Gautier, A. Chauvin, D. Gapais, E. A. Rossello, and O. Lòpez-Gamundı́ (2001), Style and history of Andean deformation, Puna plateau, northwestern Argentina, Tectonics, 20, 210 – 234. DeCelles, P., and B. K. Horton (2003), Early to middle Tertiary foreland basin development and the history of Andean crustal shortening in Bolivia, Geol. Soc. Am. Bull., 115, 58 – 77. Deeken, A., E. R. Sobel, M. Haschke, M. R. Strecker, and U. Riller (2004), Age of Initiation and Growth Pattern of the Puna plateau, NW-Argentina, constrained by AFT Thermochronology: abstract volume, paper presented at International Fission Track Conference, Vrije Univ., Amsterdam. Dickinson, W. R. (1970), Interpreting detrital modes of greywacke and arkose, J. Sediment. Petrol., 40, 695 – 707. Dickinson, W. R. (1985), Interpreting provenance relations from detrital modes of sandstones, in Provenance of Arenites, edited by G. G. Zuffa, pp. 333 – 361, Springer, New York. Donato, E. (1987), Caracterı́sticas estructurales del sector occidental de la Puna Salteña, Bol. Inf. Petrol., 12, 89 – 99. Donelick, R. A., R. A. Ketchman, and W. D. Carlson (1999), Varaibility of apatite fission track annealing kinetics: II. Crystallographic orientation effects, Am. Mineral., 84, 1224 – 1234. Dumitru, T. (1993), FT STAge Systems, described, Nucl. Tracks Radiat. Meas., 21, 575 – 580. Ege, H. (2004), Exhumations- und Hebungsgeschichte der zentralen Anden in Südbolivien (21S) durch Spaltspur-Thermochronologie an Apatit, Ph.D. thesis, 159 pp., Freie Univ. Berlin, Berlin. 18 of 19 Elger, K. (2004), Analysis of deformation and tectonic history of the southern Altiplano plateau (Bolivia) and their importance for plateau formation, Ph.D. thesis, 152 pp., GeoForschungsZentrum Potsdam, Potsdam, Germany. Flint, S. (1985), Alluvial fan and playa sedimentation in an Andean arid closed basin: the Pacencia Group, Antofagasta Province, Chile, J. Geol. Soc., 142, 533 – 546. Flint, S., and P. Turner (1988), Alluvial fan and fandelta sedimentation in a forearc extensional setting: The Cretaceous Coloso Basin of northern Chile, in Fan Deltas: Sedimentology and Setting, edited by W. Nemec and R. J. Steel, pp. 387 – 399, Blackwell Sci., Malden, Mass. Galbraith, R. F. (1981), On statistical models for fission track counts, Math. Geol., 13, 471 – 478. Gazzi, P., G. G. Zuffa, G. Gandolfi, and L. Paganelli (1973), Provenienza e dispersione litoranea delle sabbie delle spiaggie adriatiche fra le foci dell’Isonzo e del Foglia: Inquadramento regionale, Mem. Soc. Geol. Ital., 12, 1 – 37. Graham, S. A., R. V. Ingersoll, and W. R. Dickinson (1976), Common provenance for lithic grains in Carboniferous sandstones from the Ouachita Mountains and Black Warrior Basin, J. Sediment. Petrol., 46, 620 – 632. Green, P. F. (1981), A new look at statistics in fissiontrack dating, Nucl. Tracks, 5, 77 – 86. Grier, M. E., and R. D. Dallmeyer (1990), Implications for foreland basin development, NW Argentina, J. S. Am. Earth Sci., 4, 351 – 372. Günther, A., M. Haschke, K.-J. Reutter, and E. Scheuber (1998), Kinematic evolution and structural geometry of the Chilean Precordillera (21.5 – 23S): Inversional tectonics in the late Cretaceous-Paleogene magmatic arc, Terra Nostra, 5, 58 – 59. Hardie, L. A., J. P. Smoot, and H. P. Eugster (1978), Salina lakes and their deposits: a sedimentological approach, in Modern and Ancient Lake Sediments, TC4011 CARRAPA ET AL.: OLIGOCENE UPLIFT IN THE CENTRAL ANDES edited by A. Matter and M. E. Tucker, Spec. Publ. Int. Assoc. Sedimentol., 2, 7 – 41. Hartley, A. J. (2003), Andean uplift and climate change, J. Geol. Soc. London, 160, 7 – 10. Hartley, A. J., S. Flint, P. Turner, and E. J. Jolley (1992), Tectonic controls on the development of a semi-arid, alluvial basis as reflected in the stratigraphy of the Purilactis Group (Upper CretaceousEocene), northern Chile, J. S. Am. Earth Sci., 5, 275 – 296. Hilley, G. E., and M. R. Strecker (2005), Processes of oscillatory basin infilling and excavation in a tectonically active orogen: Quebrada del Toro Basin, NW Argentina, Geol. Soc. Am. Bull., 117, 887 – 901. Horton, B. K., B. A. Hampton, and G. L. Waadners (2001), Paleogene synorogenic sedimentation in the Altiplano plateau and implications for initial mountain building in the central Andes, Geol. Soc. Am. Bull., 113, 1387 – 1400. Horton, B. K., B. A. Hampton, B. N. LaReau, and E. Baldellón (2002), Tertiary provenance history of the northern and central Altiplano (central Andes, Bolivia): A detailed record of plateaumargin tectonics, J. Sediment. Res., 72, 711 – 726. Hunter, R. E. (1977), Basin types of stratification in small eolian dunes, Sedimentology, 24, 361 – 387. Hurford, A. J., and P. F. Green (1983), The Zeta age calibration of fission track dating, Isotope Geosci., 1, 285 – 317. Ingersoll, R. V., T. F. Bullard, T. F. Ford, J. P. Grimm, J. D. Pickle, and S. W. Sares (1984), The effect of grain size on detrital modes: A test of the Gazzi-Dickinson point-counting method, J. Sediment. Petrol., 54, 103 – 116. Isacks, B. (1988), Uplift of the central Andean plateau and bending of the Bolivian orocline, J. Geophys. Res., 93, 3211 – 3231. Jordan, T. E., and R. N. Alonso (1987), Cenozoic stratigraphy and basin tectonics of the Andes mountains, 20 – 28 south latitude, AAPG Bull., 71, 49 – 64. Jordan, T. E., J. H. Reynolds, and J. P. Herikson (1997), Variability in age of initial shortening and uplift in the central Andes, 16 – 33300S, in Tectonic Uplift and Climate Change, edited by W. F. Ruddiman, pp. 41 – 61, Springer, New York. Jordan, T. E., W. M. Burns, R. Veiga, F. Pangaro, P. Copeland, and C. Mpdozis (2001), Extension and basin formation in the southern Andes caused by increased convergence rate, Tectonics, 20, 308 – 424. Kay, S. M., B. Coira, and J. Viramonte (1994), Young mafic back-arc volcanic rocks as indicators of continental lithospheric delamination beneath the Argentine Puna plateau, central Andes, J. Geophys. Res., 99, 24,323 – 24,339. Kleinert, K., and M. R. Strecker (2001), Changes in moisture regime and ecology in response to late Cenozoic orographic barriers: the Santa Maria Valley, Argentina, Geol. Soc. Am. Bull., 113, 728 – 742. Kley, J., J. Müller, S. Tawackoli, V. Jaconshagen, and E. Manutsoglu (1997), Pre-Andean and Andean-age deformation in the eastern and southern Bolivia, J. S. Am. Earth Sci., 10, 1 – 19. Kraemer, B., D. Adelmann, M. Alten, W. Schnurr, K. Erpenstein, E. Kiefer, P. van den Bogaard, and K. Görler (1999), Incorporation of the Paleogene foreland into Neogene Puna plateau: The Salar de Antofolla, NW Argentina, J. S. Am. Earth Sci., 12, 157 – 182. Lowe, D. R. (1979), Sediment gravity flows: their classification and some problems of application to natural flows and deposits, in Geology of Continental Slopes, edited by L. J. Doyle and O. H. Pilkey, Spec. Publ. SEPM Soc. Sediment. Geol., 27, 75 – 82. Maksaev, V., and M. Zentilli (2000), Fission track thermochronology of the Domeyko Cordillera, northern Chile: Implications for Andean tectonics and porphyry copper metallogenesis, Explor. Min. Geol., 8, 65 – 89. Marrett, R. (1990), The late Cenozoic tectonic evolution of the Puna plateau and adjacent foreland, northwestern Argentine Andes, Ph.D. thesis, 365 pp., Cornell Univ., Ithaca, N. Y. Marrett, R., and M. R. Strecker (2000), Response of intracontinental deformation in the central Andes to late Cenozoic reorganization of South American Plate motions, Tectonics, 19, 452 – 467. McQuarrie, N. (2002a), Initial plate geometry, shortening variations, and evolution of the Bolivian orocline, Geology, 30, 867 – 870. McQuarrie, N. (2002b), The kinematic history of the central Andean fold-thrust belt, Bolivia: Implications for building a high plateau, Geol. Soc. Am. Bull., 114, 950 – 963. McQuarrie, N., and P. DeCelles (2001), Geometry and structural evolution of the central Andean backthrust belt, Bolivia, Tectonics, 20, 669 – 692. Métivier, F., Y. Gaudemer, P. Tapponnier, and B. Meyer (1998), Northeastward growth of the Tibet plateau deduced from balanced reconstruction of two depositional areas: The Qaidam and Hexi Corridor basins, China, Tectonics, 17(6), 823 – 842. Miall, A. D. (1978), Lithofacies types and vertical profile models in braided river deposits: A summary, in Fluvial Sedimentology, edited by A. D. Miall, Mem. Can. Soc. Pet. Geol., 5, 597 – 604. Miall, A. D. (Ed.) (1996), The Geology of Fluvial Deposits, 582 pp., Springer, New York. Muruaga, C. (2001), Estratigrafı́a y desarrollo tectonosedimentario de los sedimentos terciarios en los alrededores de la Sierra de Hualfı́n, borde suroriental de la Puna, Catamarca, Argentina, Asoc. Argent. Sedimentol. Rev., 8, 27 – 50. Nemec, W., and R. J. Steel (1984), Alluvial and coastal conglomerates: their significance features and some comments on gravelly mass flow deposits, in Sedimentology of Gravel and Conglomerates, edited by E. H. Koster and R. J. Steel, Can. Soc. Pet. Geol. Mem., 10, 1 – 31. Rasmussen, H. (2000), Nearshore and alluvial facies in the Sant Llorenç del Munt depositional system: Recognition and development, Sediment. Geol., 138, 71 – 98. Reading, H. G. (1996), Sedimentary Environments: Processes, Facies and Stratigraphy, 688 pp., 3rd ed., Blackwell Sci., Malden, Mass. Reutter, K. J., R. Döbel, T. Bogdanic, and J. Kley (1994), Geological map of the central Andes between 20S and 26S, in Tectonics of the Southern Central Andes, edited by K. J. Reutter, E. Scheuber, and P. Wigger, pp. 121 – 139, Springer, New York. Segerstrom, K., and J. C. M. Turner (1972), A conspicuous flexure in regional structural trend in the Puna of northwest Argentina, U.S. Geol. Surv. Prof. Pap., 800-B, B205 – B209. 19 of 19 TC4011 Smith, D. G. (1987), Meandering river point lithofacies models: modern and ancient examples compared, in Recent development if fluvial sedimentology, edited by F. G. Etheridge, R. M. Flores, and M. D. Harvey, Spec. Publ. SEPM Soc. Sediment. Petrol., 39, 83 – 91. Sobel, E., and M. R. Strecker (2003), Uplift, exhumation and precipitation: tectonic and climatic control of late Cenozoic landscape evolution in the northern Sierras Pampeanas, Argentina, Basin Res., 15, 431 – 451. Sobel, E. R., G. E. Hilley, and M. R. Strecker (2003), Formation of internally drained contractional basins by aridity-limited bedrock incision, J. Geophys. Res., 108(B7), 2344, doi:10.1029/2002JB001883. Sohn, Y. K. (1997), On traction carpet sedimentation, J. Sediment. Geol., 67, 502 – 509. Steinmann, G. (1929), Geologie von Peru, 448 pp., Karl Winter, Heidelberg, Germany. Strecker, M. R. (1987), Late Cenozoic landscape development, the Santa Maria Valley, northwest Argentina, Ph.D. thesis, 261 pp., Cornell Univ., Ithaca, N. Y. Strecker, M. R., P. Cerveny, A. L. Bloom, and D. Malizia (1989), Late Cenozoic tectonism and landscape development in the foreland of the Andes: Northern Sierras Pampeanas (26 – 28), Argentina, Tectonics, 8, 517 – 534. Tapponnier, P., Xu Z., F. Roger, B. Meyer, N. Arnaud, G. Wittlinger, and Yang J. (2001), Oblique stepwise rise and growth of the Tibet plateau, Science, 294, 1671 – 1677. Tucker, M. (2001), Sedimentary Petrology, 3rd ed., 262 pp. Blackwell, Malden, Mass. Urreiztieta, M., D. Gapais, C. Le Corre, P. R. Cobbold, and G. T. Rosello (1996), Cenozoic dextral transpression and basin development at the southern edge of the Puna plateau, northwest Argentina, Tectonophysics, 254, 17 – 39. Vandervoort, D. S. (1993), Non-marine evaporite basin studies, southern Puna plateau, central Andes, Ph.D. thesis, 261 pp., Cornell Univ., Ithaca, New York. Vandervoort, D. S., T. E. Jordan, P. K. Zeitler, and R. N. Alonso (1995), Chronology of internal drainage development and uplift, southern Puna plateau, Argentine central Andes, Geology, 23, 145 – 148. Voss, R. (2000), Die Geologie der Region um den südlichen Salar de Antofalla (NW-Argentinien), Ph.D. thesis, 201 pp., Freie Univ., Berlin. Voss, R. (2002), Cenozoic stratigraphy of the southern Salar de Antofalla region, northwestern Argentina, Riv. Geol. Chile, 29, 151 – 165. Wagner, G., and P. Van der Haute (1992), FissionTrack Dating, 285 pp., Springer, New York. D. Institut für Geowissenschaften, FrieAdelmann, drich-Schiller-Universität Jena, Burgweg 11, D-07749 Jena, Germany. B. Carrapa, E. Mortimer, E. R. Sobel, and M. R. Strecker, Institut für Geowissenschaften, Universität Potsdam, Karl-Liebknecht-Str. 24, D-14476 Potsdam, Germany. (carrapa@geo.uni-potsdam.de) G. E. Hilley, Department of Earth and Planetary Science, University of California, 377 McCone Hall, Berkeley, CA 94720-4767, USA.