Earth and Planetary Science Letters 247 (2006) 82 – 100
www.elsevier.com/locate/epsl
Cenozoic orogenic growth in the Central Andes: Evidence from
sedimentary rock provenance and apatite fission track
thermochronology in the Fiambalá Basin, southernmost
Puna Plateau margin (NW Argentina)
B. Carrapa ⁎, M.R. Strecker, E.R. Sobel
Institut für Geowissenschaften, Universtität Potsdam, 14476 Golm, Germany
Received 10 November 2005; received in revised form 2 March 2006; accepted 6 April 2006
Editor: V. Courtillot
Abstract
Intramontane sedimentary basins along the margin of continental plateaus often preserve strata that contain fundamental
information regarding the pattern of orogenic growth. The sedimentary record of the clastic Miocene–Pliocene sequence deposited
in the Fiambalá Basin, at the southern margin of the Puna Plateau (NW Argentina), documents the late Miocene paleodrainage
evolution from headwaters to the west, towards headwaters in the ranges that constitute the border of the Puna Plateau to the north.
Apatite Fission track (AFT) thermochronology of sedimentary and basement rocks show that the southern Puna Plateau was the
source for the youngest, middle Miocene, detrital population detected in late Miocene rocks; and that the margin of the Puna
Plateau expressed a high relief, possibly similar to or higher than at present, by late Miocene time. Cooling ages obtained from
basement rocks at the southern Puna margin suggest that exhumation started in the Oligocene and continued until the middle
Miocene. We interpret the basin reorganization and the creation of a high relief plateau margin to be the direct response of the
source–basin system to a wholesale surface uplift event that may have occurred during the late Cenozoic in the Puna–Altiplano
region. At this time coeval paleodrainage reorganization is observed not only in the Fiambalá Basin, but also in different basins
along the southern and eastern Puna margin, suggesting a genetic link between the last stage of plateau formation and basin
response. However, this event did not cause sufficient exhumation of basin bounding ranges to be recorded by AFT
thermochronology. Our new data thus document a decoupling between late Cenozoic surface uplift and exhumation in the southern
Puna Plateau. High relief achieved at the Puna margin by late Miocene time is linked to Oligocene–Miocene exhumation; no
significant erosion (< 3 km) has occurred since in this arid highland.
© 2006 Elsevier B.V. All rights reserved.
Keywords: plateau; sedimentary basin; provenance; thermochronology; exhumation; uplift; relief
1. Introduction
⁎ Corresponding author.
E-mail addresses: carrapa@geo.uni-potsdam.de (B. Carrapa),
strecker@geo.uni-potsdam.de (M.R. Strecker),
sobel@rz.uni-potsdam.de (E.R. Sobel).
0012-821X/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.epsl.2006.04.010
Orogenic plateaus, such as Tibet or the Andean
Puna–Altiplano region, are areas of high mean-surface
elevation, which exert a fundamental influence on
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
atmospheric circulation, precipitation patterns, and
modes of erosion and sedimentation. With 3700 m
average elevation, the arid, Andean Puna–Altiplano
Plateau of Argentina and Bolivia is the second largest
plateau on Earth, after Tibet (e.g., [1]). Little is still
known about the timing, patterns or mechanisms of
plateau formation. Paleoelevation and oxygen isotope
data available in the Bolivian Altiplano suggest that
most of the plateau surface uplift may have occurred in
83
the last 10 Ma [2–4]. However, the lack of quantitative
data for most of the extensive plateau region, especially
in the south, has prevented the validation of this
scenario. Also, it is unclear how range exhumation
and sedimentary basin architecture along the margin of
the plateau would have responded to such an uplift
event.
Although many studies have focused on the
formation of the Puna–Altiplano region, unresolved
Fig. 1. DEM of the Puna–Altiplano plateau; thick dashed black and white line denotes area exhumed between 30 and 50 Ma, based on AFT data of
Maksaev and Zentilli [10]. White box shows the location of Fig. 2, the study area. A: Angastaco Basin, where the exhumation of the Eastern
Cordillera between ca. 22 and 13 Ma is recorded by AFT from both detrital samples [23] and from vertical profiles [61]. C: Calalaste range,
characterized by AFT ages between 24 ± 3 and 29 ± 2 Ma ages [13]. CR: Chango Real, characterized by AFT ages between 29 ± 3 and 38 ± 3 Ma [23].
SF: Sierra Famatina range, characterized by 47 ± 4 Ma AFT age; SU and SM correspond to Sierra Umango and Sierra Fertile, characterized by 147 ± 6
and 253 ± 8 AFT ages respectively [28]. Slc: Sierra de los Colorados area, where ca. 14 Ma detrital AFT population has been recorded [67]. Striped
area corresponds to coeval along strike deformation and exhumation between 12 and 25 Ma, based on data from Carrapa et al. [13] and Deeken et al.
[61]. White dashed line corresponds to the extension to the north of the Sierra Famatina range (SF). The inset figure shows the portion of South
America with elevations over 3000 m in gray modified after Horton et al. [72].
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B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
questions remain, including what uplift mechanism was
responsible, and what spatial–temporal uplift patterns
were characteristic of the evolution of this region (e.g.
[1,5–7]). Recent data show that regional deformation of
the present plateau region started in the Paleocene–
Eocene in the Bolivian Altiplano (e.g. [6,8,9]) and in the
Coastal Cordillera of Chile [10], and in the Eocene–
Oligocene in the Puna Plateau and Eastern Cordillera of
Argentina [11–13]. In particular, structural data suggest
that most of the shortening occurred before the late
Cenozoic [5,7,9,14,15]. If shortening and crustal
thickening were the main driving mechanism for plateau
uplift, a region with high elevation and/or high relief
may have existed already at that time. Alternative
mechanisms for plateau uplift include isostatic uplift
following lithospheric delamination [2,16,17], magmatic addition [15], underplating of material removed from
the forearc by subduction erosion [18,19], and possibly
the flow of ductile lower crust from areas of excess
shortening into areas that have a deficit of shortening
[20,21]. Lithospheric delamination and ensuing wholesale plateau uplift have been proposed to have occurred
between 8 and 3 Ma [22] in the region of the present-day
southern Puna Plateau. Sedimentological and thermochronological data from the southern Puna Plateau and
the Argentine Eastern Cordillera show that deformation
driving exhumation started already in Eocene–Oligocene time, contributing to the development of basin
compartmentalization and eventually internal drainage
conditions (e.g. [11,13,23]). However, it is not clear
when the plateau reached geomorphic conditions similar
to present, and if and how the attainment of such a
geomorphic phenomenon is related to a wholesale, late
Cenozoic tectonic uplift event.
In summary, different data sets from the Puna–
Altiplano region and its margins suggest that widespread deformation and exhumation of individual
ranges had occurred already in Oligocene time in the
present-day plateau realm, which may have been
followed by a surface uplift event in the Mio-Pliocene.
The amount of exhumation related to these early events
and the timing of the inferred last surface uplift are still
poorly constrained. In particular, it is not clear whether
exhumation and surface uplift occurred at the same time
and were linked (i.e. were coupled).
Sedimentary rocks preserved within and along the
margin of the Puna Plateau provide important information about the timing and potentially the processes
responsible for establishing the morphological features
characteristic of the present-day plateau. For example,
sedimentary basins located within the present-day
plateau, such as in the Calalaste region (Fig. 1), record
the direct response of drainage basin reorganization to
exhumation of intra-basin ranges in Eocene–Oligocene
time [13]. Likewise, intramontane basins in the Eastern
Cordillera, and in the transition between the Argentine
Sierras Pampeanas province and the Puna, show a
similar response to the progressive unroofing of
bounding ranges that deform and exhume as the plateau
grows spatially and temporally along its margins (e.g.
[11,24–26]).
With this study we aim to determine (1) when
exhumation occurred in the southern plateau margin
and if and how it is related to previously proposed
mechanisms; (2) whether exhumation was coupled
with a wholesale late Cenozoic surface uplift event;
and (3) how such late stage plateau uplift was
reflected in the geological record. In particular, we
present new sedimentologic and apatite fission track
(AFT) thermochronologic data from Mio-Pliocene
sedimentary rocks and from Paleozoic basement
rocks from the southern margin of the Puna Plateau
that constrain the exhumation history and paleogeographic evolution of this region with respect to
plateau–margin growth. Our data document early to
middle Miocene exhumation of the Puna Plateau
margin associated with the creation of high topography that provided sediments to the Fiambalá Basin by
ca. 6 Ma. This was coeval with an important
paleogeographic reorganization and change in sediment source regions, inferred to be the direct result of
widespread plateau uplift.
Fig. 2. (A) Geological map of the Fiambalá Basin and surrounding region (redrawn from the geological map of Catamarca, 1 : 500,000 [73]): 1)
Quaternary volcanics, 2) Mio-Pliocene volcanics (andesite–dacites), 3) Quaternary evaporites, 4) Cambrian–Ordovician volcanics (dacites) and
metamorphic rocks, 5) Paleozoic granites, 6) Triassic–Jurassic gabbros, 7) Permo-Triassic granites, 8) Ordovician phyllites, gneiss, and minor
metavolcanites, 9) Cambrian phyllites, schists and metavolcanics, 10) Permo-Triassic red sandstones, conglomerates, marls, and related volcanics
(Grupo Paganzo), 11) Ordovician granodiorites and minor gabbros, 12) Miocene (Guanchin and Tamberia formations), 13) Pliocene (Punashotter
Formation) and Quaternary, 14) late Miocene–Pliocene distal facies: a) Guanchin Formation, b) Punaschotter Formation. The black line correspond
to the transect along which the stratigraphic sections were measured. Distal facies have been measure at the far NE end of this transect. White inset
rectangle: northern vertical profile (Cerro Negro: CN); gray inset rectangle: eastern vertical profile (Alto Grande: AG); dark gray square corresponds
to sample UP78-9 (Sierra de las Planchades: Pl); light gray square corresponds to sample UP78-3 (Filo Negro: FN). The ages of these samples are
listed in Table 1. (B) Simplified profile (A–A′) through the investigated section in the Fiambalá Basin; T: Tamberia, G: Guanchin, P: Punaschotter,
formations; Q: Quaternary.
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
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B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
2. Geological setting
Our study area comprises the southernmost basement
ranges of the Puna Plateau margin, ca. 4000 m high, and
the adjacent Fiambalá Basin, a Cenozoic sedimentary
basin immediately to the south at ca. 1650 m elevation
(Fig. 1). Deformation and exhumation of reverse-fault
bounded basement ranges within and on the eastern
margin of the present southern Puna began during the
Oligocene (e.g., [23,27]). AFT cooling ages from
western areas record deformation and exhumation
commencing during Eocene and early–middle Miocene
time, respectively [10,28]. To the southeast the Puna is
transitional with the reverse-fault bounded Sierras
Pampeanas basement uplifts, a broken foreland province
overlying the flat subduction segment of the Nazca Plate
between 27° and 33°S latitude [29].
The arid Fiambalá Basin contains over 4 km of upper
Mio-Pliocene rocks belonging to the Tamberia, Guanchin and Punaschotter formations [30] that record the
exhumation and erosion of the surrounding ranges [31–
34]. These sediments are distributed throughout the
entire basin and reflect ephemeral braided fluvial and
alluvial fan depositional environments [35]. The lack of
plant fossils and the presence of mud cracks, halite and
gypsum layers [36] suggest that the depositional
environment was already arid at time of the Tamberia
sediments deposition (ca. 8 Ma). To the west and north–
northwest the basin margin mainly comprises CambroOrdovician dacites and sedimentary rocks, Paleozoic
(Ordovician–Carboniferous) granites, Carboniferous,
Permian and Triassic sedimentary rocks as well as
Tertiary and Quaternary volcanic rocks of predominantly andesitic composition [30]. To the northeast and east
the basin is bounded mainly by Cambrian schists and
phyllites and minor sectors with Ordovician–Carboniferous granites that constitute the southernmost end of
the Puna Plateau (Fig. 2).
3. Methods
In order to constrain the exhumation history and
paleogeography of the southern Puna Plateau margin and
the adjacent ranges during the late Cenozoic, we choose
a multidisciplinary approach involving quantitative
sedimentological investigations and thermochronological analysis using apatite fission track dating.
3.1. Sedimentary provenance
Sedimentary provenance analysis was carried out on
sedimentary rocks from the Fiambalá Basin in order to
constrain the spatial–temporal evolution of the contributing sediment sources. Sedimentological investigations
were conducted along a NE to SW transect (Fig. 2), the
only transect in the basin along which the complete
Cenozoic sequence is exposed; this includes the easternmost outcrops in the basin, which record more distal
sources. Clast composition analysis was performed
throughout the complete stratigraphic sequence at eighteen
localities (Figs. 2 and 3). Pebbles of different lithologies
were counted every 5 to 10 cm (depending on granulometry) within a 50× 50 cm2 grid. The grid was shifted
parallel to bedding until at least 100 clasts were counted at
each locality, for a total of over 1800 clast counts.
3.2. Apatite fission track thermochronology
Apatite Fission Track (AFT) thermochronology was
performed on both basement rocks surrounding the
Fiambalá Basin and sedimentary rocks from the Cenozoic
basin sequence (detrital samples), in order to constrain the
cooling and exhumation histories of the source areas as
well as the relationship between exhumation, relief,
uplift, and sedimentation. AFT thermochronology provides information on the timing and rates of cooling
occurring at temperature (T) between ca. 60 and 110 °C,
defined as the Partial Annealing Zone (PAZ). The exact T
of the upper (hotter) boundary depends on the kinetic
characteristics of the apatites and the cooling rate; the
former can be quantified by measuring the diameter of
track etch pits, known as Dpar [37–39]. In general, apatites
with smaller Dpar are typical of fluorine-rich apatite and
are characterized by lower temperatures of the upper
boundary. Fission track-lengths provide information on
the proportion of the cooling history that the sample
experienced within the PAZ, and hence how quickly the
apatite passed through the PAZ. Therefore, in order to
interpret the AFT data in terms of a T–t path an integrated
analysis of fission track age, track length distribution, and
kinetic characteristics of the apatite grains is required.
Samples were prepared and analyzed following the
procedure described by Sobel and Strecker [40].
About 20 grains for basement samples and 100 grains
for detrital samples were dated (Table A1 in the
Appendix). Confined track-lengths were measured in
both basement and detrital samples together with the
angle between the confined track and the C-crystallographic axis (C-axis projected data). Use of the angular
data mitigates track-measurement bias [41] and
improves annealing model results, as confined tracks
anneal anisotropically as a function of orientation
[37,38]. Apatite etch pit diameter (Dpar) and grain
shape were also determined (Table A1 in the Appendix).
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
Fig. 3. Clast counts (see text for explanation) and simplified
stratigraphic logs from the Fiambalá Basin. Paleocurrents are indicated
with rose diagrams; the number of measurements is noted on the side.
AFT detrital sample numbers shown in Fig. 6 are marked in italics.
Depositional ages are based on magnetostratigraphy [31] and zircon
fission track dating on ash layers [32]. Mrl: marls; fS: fine sandstones;
mS: middle sandstones; mcg: micro conglomerate; cgl: conglomerates.
87
Pooled ages are reported for the basement samples,
calculated using the Trackkey program [42] (Table 1), as
they all pass the chi squared test [43,44]. For each detrital
sample fission track grain-age distributions were decomposed following the binomial peak-fit method [45]
incorporated in the Binomfit program [46]. In automatic
mode, the program provides an iterative search of peak
ages and number of peaks to find the optimal (best-fit)
solution. The best-fit solution is determined by directly
comparing the distribution of the grain data to a predicted
mixed binomial distribution. The related best-fit peaks
are reported by age, uncertainty, and size (Table 2). The
uncertainty for the peak age is given at 95% confidence
intervals. The size of the individual peaks is reported as a
fraction (in percent) on the total (Table 2).
Basement samples were collected along two elevation transects from basin bounding ranges to the north
and east and from different ranges to the west of the
basin (Fig. 2). The vertical profiles were collected along
the steepest possible routes between 2291 m to 4072 m
elevation (northeast, Cerro Negro – CN), and 2165 and
3127 (east, Alto Grande – AG). Results from seven
samples from the CN profile are presented in Fig. 4 and
Table 1. Unfortunately, only the lowest sample (2165 m)
from the AG profile yielded sufficient apatite to provide
results (Table 1). Out of many samples collected to the
west of the basin only two, Sierra de las Planchadas (Pl;
Fig. 2) and Filo Negro (FN; Fig. 2), yielded sufficient
apatite to provide results. In total, we present results
from ten basement samples and one cobble from the
Punaschotter Formation (Table 1).
In addition, five detrital samples from the Tamberia,
Guanchin and Punaschotter formations were selected for
AFT analysis (Table 2), representing ca. 1 sample per Ma
of depositional time. Assuming that the temperature in
the sedimentary basin was never high enough to overprint the original thermochronological signal (discussed
in the following), detrital thermochronology provides
fundamental information on characteristic cooling ages of
rocks originally present in the adjacent source (e.g.
[47,48]) and the timing, rates and patterns at which these
rocks were exhumed (e.g. [49–51]). Most detrital fission
track thermochronology studies have utilized zircons (e.g.
[52,53]) while apatite has only rarely been analyzed (e.g.
[54]). Only recently, detrital AFT analysis has been
recognized as an important tool in resolving young
exhumation histories [11,55]. The advantage of analyzing
apatite rather than zircon fission tracks is that the former
mineral provides information on the thermal history of
shallower crustal levels due to the lower closure
temperature, thus enabling the identification of cooling
events in regions where little erosion has occurred. When
88
Table 1
Apatite fission track analytical data of the NE vertical profile (VP) and single basement samples and pebble
Lithology
Elevation
(m)
No.
Xlsa
Rho-S
(e5)b
NSc
Rho-I
(e5)b
NIc
P(χ)2
(%)d
Rho-D
(e5)e
NDf
Age
(Ma)
±1σ
U
(ppm)
Mean length
(μm)
Dpar
(μm)
S.D.
041B(UP61-10)
042B(UP61-12)
042A(UP61-13)
042B(UP60-1)
045A(UP60-2)
046A(UP60-3)
048(UP60-4)
149(UP78-9)
116-1(UP78-3)
161-1(UP79-5)
177 (79-11)
VP (CN), granite, NE
VP (CN), granite, NE
VP (CN), granite, NE
VP (CN), granite, NE
VP (CN), granite, NE
VP (CN), granite, NE
VP (CN), granite, NE
(P1), granite, W
(FN), phyllite, W
Granite east (Alto Grande)
Granite cobble,
(Pliocene Punaschotter Fm.)
4072
3785
3463
3190
2889
2584
2291
2952
4635
2165
1648
25
10
20
22
20
20
20
16
15
20
19
3.200
1.040
1.193
0.418
4.172
2.880
1.679
2.279
2.119
0.621
7.767
493
22
141
45
724
547
201
82
107
69
1310
27.409
9.265
12.356
5.356
54.501
46.752
23.312
13.204
12.495
8.429
16.186
4222
196
1460
576
9458
8879
2791
4775
631
939
2730
90.15
92.46
96.05
84.08
0.09
98.72
60.8
89.6
63.5
11.33
42.62
10.771
10.688
10.647
13.232
13.144
13.057
12.97
11.037
11.943
9.7876
9.3689
4444
4444
4444
5168
51.68
5168
5168
4612
4612
3922
3922
23.1
22.0
18.9
19.0
18.4
14.8
17.1
34.6
43.9
13.1
81.3
1.2
5.0
1.7
3.0
0.8
0.7
1.3
4.2
4.4
1.7
3.4
30.33
10.69
14.02
4.83
52.00
44.29
20.73
17.31
15.32
12.18
21.28
NA
NA
NA
NA
14 ± 1.0
NA
NA
NA
NA
NA
NA
1.8
2.1
1.9
1.8
2.1
2.1
1.9
1.8
1.9
1.7
1.9
0.3
0.2
0.2
0.2
0.2
0.2
0.2
0.3
0.1
0.2
0.1
AFT analytical data for the vertical profiles (VP), basement samples and pebble; the sample indicated in bold is the one modeled in Fig. 7.
CN: vertical profile along the Cerro Negro (north-east); Pl: single sample from the Sierra de las Planchadas to the west; AG: single sample from a vertical profile along the Alto Grande to the east.
Sample 177 is a cobble from the Punaschotter Formation (refer to Fig. 3). Samples 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 [74].
Analysis performed with reflected and transmitted light at 1250× magnification. Samples were irradiated at Oregon State University. Samples where etched in 5.5 M nitric acid at 21 °C for 20 s.
Following irradiation, the mica external detectors were etched with 21 °C in 40% hydrofluoric acid for 45 min. The pooled age is reported for all samples as they pass the χ2 test, suggesting that they
represent a single population. Error is 1σ, calculated using the zeta calibration method [75] with zeta of 364.1 ± 4.8 for apatite [unpublished data, 2006, B. Carrapa].
a
No. Xls is the number of individual crystals dated.
b
Rho-S and Rho-I are the spontaneous and induced track density measured, respectively (tracks/cm2).
c
NS and NI are the number of spontaneous and induced tracks counted, respectively.
d
(χ)2 (%) is the chi-square probability [45,76]. Values greater than 5% are considered to pass this test and represent a single population of ages.
e
Rho-D is the induced track density in external detector adjacent to CN5 dosimetry glass (tracks/cm2).
f
ND is the number of tracks counted in determining Rho-D. Dpar: fission track etch pit measurements, SD is the related standard deviation.
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
Sample
number
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
89
Table 2
Detrital populations of samples from the Fiambalá clastic sequence
Sample
Approximate depostional age
N
P1
P2
P3
P4
Punaschotter 177
t < 3.6
100
92.9 ± 18.3
3.6 < t < 5.7
129
Guanchin 054⁎
30.0 ± 2.8
23.5%
36.3 ± 3
22%
57.2 ± 5.5
10.7%
Guanchin 053
3.6 < t < 5.7
110
Tamberia 050⁎
5.7 < t < 8
117
11.1 ± 1
60.60%
14.0 < 1.5
25.10%
14.4 ± 1.6
23.20%
13.8 ± 1.7
31.60%
Tamberia 003
5.7 < t < 8
108
43.0 ± 3.7
32.10%
37.2 ± 4.6
23.70%
81.7 ± 7.9
15.50%
92.0 ± 6.5
22.40%
71.4 ± 6.1
21.60%
49.7 ± 4.6
57.30%
P5
P6
127.1 ± 10.6
34.10%
167.8 ± 9
22.20%
123.3 ± 11.6
19.10%
121.9 ± 12.2
42.70%
217.5 ± 92.1
3.30%
206.0 ± 47.3
4%
⁎ Modeled samples in Fig. 6.
applying detrital AFT thermochronology, a large number
of grains and related lengths must be analyzed in order to
obtain a statistically significant representation of ages
present in the source region.
3.3. Track-length modeling
Track-length modeling was carried out on basement
and detrital samples using the multikinetic annealing
model AFTSolve [56] in order to better define the
exhumation history of specific sediment sources and to
constrain the maximum degree of burial re-heating,
respectively. In the latter case, modeling was performed
on selected detrital populations from the stratigraphically oldest (and deepest) samples 050 and 054 from the
Tamberia and Guanchin formations, respectively, for
which enough data for modeling were available.
Populations were selected for which sufficient lengths
could be associated with specific age grains, in order to
check on possible annealing due to burial-related reheating. When modeling a specific age detrital population, an important issue is that the ages belonging to a
single population might be derived from a broad
spectrum of possible sources that experienced similar,
but not necessarily identical thermal histories. Furthermore, a detrital apatite population is typically composed
of a range of ages that may be derived from different
elevations within the same range. Consequently, the
spectrum of lengths in a specific population may reflect
both multiple cooling events prior to exhumation and
variations due to different elevations of the source unit,
potentially overprinted by re-heating due to burial and
subsequent cooling. Considering that multiple cooling
events may have affected the original source prior to
deposition, correctly constraining this portion of the
cooling path in the model is difficult. Therefore, it is
clear that modeling detrital samples is challenging and
must be undertaken with caution. Therefore, we can
only make reasonable hypotheses about the thermal
history of the original source prior to deposition in the
basin if independent geological constraints are available.
In the following section, track-length modeling is
applied to test hypotheses about the amount of reheating experienced due to burial of the samples during
the formation of the Fiambalá Basin. The initial time
constraint is set at double (at least) the pooled age of the
sample or detrital population to ensure that the firstformed tracks are all completely annealed, thereby
avoiding potential boundary condition artifacts [56].
4. Results and discussions
4.1. Sedimentary evolution
Fig. 4. Plot of AFT age versus elevation in km for basement samples
collected from the southern Puna margin (CN, see Fig. 2 for location and
Table 1 for tabulated data); the grey sample (UP60-2) is modeled in Fig. 7.
Sedimentation in the Fiambalá Basin commenced
between ca. 8 and 5.7 Ma with the deposition of the
Tamberia Formation [30,32]. It comprises massive,
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B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
generally structureless sandstones, with occasional
planar cross-bedded strata grading into well sorted,
parallel bedded conglomerates toward the top (Fig. 3).
The clast composition of the upper Tamberia Formation
is characterized by dacitic volcanics and red sandstones
and minor andesitic volcanics; granites are also present.
These lithologies, particularly the red sandstone clasts,
are typical of Cambro-Ordovician and Permo-Triassic
rocks from western sources. Granites are typical of both
western and north-eastern sources. Paleocurrent directions measured in an imbricated conglomerate layer
(Pc10), from the upper part of this formation, suggest a
first contribution from the north-east (Fig. 3).
The Guanchin Formation was deposited between ca.
5.7 Ma and 3.6 Ma [32]. It comprises mainly trough and
planar cross bedded sandstones with occasional CaCO3
bearing paleosols and silicified tree trunks, alternating
with conglomerate lenses with silt intraclasts. Toward
the top of the formation these rocks grade into coarse
sandstones and conglomerates. The lower part of the
Guanchin Formation is mainly composed of Ordovician
dacite clasts typical of western sources. The upper part
of the Guanchin Formation is still dominated by
volcanic clasts. However, an increase in the abundance
of granite clasts in the upper Guanchin Formation with
respect to the underlying Tamberia Formation may
either represent the progressive unroofing of western
crystalline sources or/and an expansion of the source
area involving north-eastern granitic sources. Importantly, distal facies of these sediments, exposed farther
basinward, record the first unequivocal influx of schist/
phyllite sourced in the southern Puna margin.
The Guanchin Formation is separated by an angular
unconformity and overlain by the Punaschotter Formation [32,34], which should be younger than 3.6 Ma [32].
To date, no other radiometric ages are available for these
sediments in the Fiambalá Basin. The Punaschotter
Formation consists of ca. 500-m-thick, disorganized and
poorly sorted conglomerates that are deeply incised and
preserved in isolated outcrops in the basin. Clast counts
reveal a broad compositional variation, but with a large
component of the same Puna-related schist/phyllite
lithologies found in the upper Guanchin Formation.
Paleocurrent data measured on ca. 100 imbricated clasts
(Pc19-20) from the easternmost preserved units clearly
record a provenance from the north–northeast (Fig. 3).
4.2. Exhumation history of the southern Puna revealed
by apatite fission track thermochronology of basement
sources
The ca. 1800 m AFT vertical profile (CN; Fig. 2)
documents that basement rocks at the southern Puna
margin passed through the partial annealing zone
(PAZ: ca. 110°– 60° [57,58]) between 14.7 ± 0.7 Ma
and 23.1 ± 1.2 Ma (Fig. 4), from which an apparent
mean exhumation rate of ca. 0.2 mm/yr can be
inferred. This estimate neglects possible affects of
advection; however, this is justified by the relatively
slow exhumation rate [59]. The onset of more rapid
exhumation is represented by a break in slope on an
age–elevation plot [60]. Unfortunately, this feature
apparently occurred at an elevation above the presently
preserved ridge crest and therefore can potentially only
be preserved in the detrital record. Although we
cannot determine the precise onset of more rapid
exhumation, it must have been prior to ca. 24 Ma,
when the highest elevation sample cooled through the
PAZ. Length measurements were only possible on
sample UP60-2 (2889 m) and yield an average value
of 14.5 ± 1 μm.
A single sample from the eastern vertical profile
(UP79-5), collected at 2165 m, has a pooled age of 13.1 ±
1.7 Ma (Fig. 2; Table 1). This age is remarkably similar
to ages characteristic of the lower portion of the northern
vertical profile, suggesting that the eastern basinbounding range is the southward structural continuation
of the southern Puna margin, and that eastern sources are
characterized by early to middle Miocene ages (Fig. 2).
A single granite sample (UP78-9) collected at 2952 m
west of the basin has a pooled age of 34.6 ± 4.2 Ma (Fig.
2; Table 1). A single sample of phyllite (UP78-3), from
the west, yields a pooled age of 43.9 ± 4.4 Ma (Fig. 2;
Table 1). Both ages are in agreement with other ages
reported from regions to the west and southwest [10,28]
and document that these source regions were subject to
an important Eocene–Oligocene cooling and exhumation event.
Fig. 5. Radial plots of detrital ages recorded in the Tamberia, Guanchin and Punaschotter formations and corresponding populations calculated in
automatic mode using the Binomfit program of Brandon [46]. Mean Dpar values and related standard deviations (S.D.) are provided). Ages on radial
plots shown in Ma; (L) denotes mean length. Arrows in sample 177 indicate the two components forming the binomial fitting curve (discussed in the
text); histograms are provided for the lengths counted for each sample. Note that lengths are in this case non-corrected for c-axis to allow comparison
with previous studies; corrected values are indicated. The light gray area corresponds to acceptable fits, the dark gray area to good fits, and the dashed
black line to the best fit.
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
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4.3. Detrital apatite fission track thermochronoloy
Using the Binomfit program on the five analyzed
detrital samples decomposes them into 2 to 5 components per sample. Examination of these components
suggests that they belong to 6 discrete age groups
(populations: P) (Table 2). Based on these age clusters
we assigned to the age populations P1 through P6. This
implies that a specific sample has only a subset of the 6
possible populations; these population numbers are not
always consecutive. Table A1 in the Appendix contains
raw data of all detrital samples including length and Dpar
values for each grain; mean length and Dpar values are
presented in Fig. 5.
In order to interpret detrital AFT ages in terms of
provenance and/or cooling and exhumation events of
a specific sediment source we need to be able to
exclude important annealing due to post-depositional
burial re-heating. Considering the total estimated
thickness of ca. 4 km of the Fiambalá Basin, postdepositional heating, annealing, and subsequent cooling are carefully addressed here. Several lines of
evidence strongly argue against significant burialrelated annealing following deposition in the Fiambalá Basin. Firstly, all detrital age populations are
older than the depositional ages and all samples
contain at least two discrete populations, indicating
that none of the analyzed samples were subjected to
total or significant annealing after deposition. This is
also confirmed by the mean length trend that tends to
decrease up-section (Fig. 5). If significant partial
annealing due to burial induced re-heating had
occurred, shorter track lengths in the bottom (deepest)
sample would be expected. Secondly, the central ages
increase systematically down-section while the population ages are relatively consistent, whereas partially annealed samples would show the opposite pattern
(Table 2; Fig. 5). Thirdly, the mean track lengths
observed from the adjacent ranges, which are the
likely source of our sediments as indicated by
sediment provenance data, are from 10 to 13 μm
[28,61] and are very similar to the ones observed in
the detrital samples, indicating that no significant
partial annealing has occurred after deposition.
4.4. Estimation of annealing due to post burial heating
from heat flow density analysis
The calculation of the maximum amount of heating
related to burial is here attempted by first performing
heat flow density analysis. Heat flow data are not
available in the study area; however, data from Bolivia
[62], suggest that heat flow in the Eastern Cordillera is
between 60 and 40 mW m− 2 (Q0). We consider a range
of plausible thermal conductivity values based on
literature (e.g., [63]); we apply values from 3.0 to
2.0 W m− 1 K− 1 for the 4 km thick sandstones and
conglomerates of the Fiambalá Basin. The following
simplified equation, assumes thermal steady state and it
is used to calculate the maximum temperature (T)
beneath a sedimentary layer with 4 km thickness (zsed),
assuming thermal steady state:
T ¼ Ts þ ðQ0 zsed =KÞ
where Ts is the temperature at the surface (∼ 10 °C;
Climatic Atlas of South America [64]), Q0 is the heat
flow, zsed is the thickness of the sedimentary pile and K
is the thermal conductivity. Following this equation we
obtain values between 63 °C (Q0 = 40 mW m− 2 and
K = 2) and 130 °C (Q0 = 60 mW m− 2 and K = 3) for
the base of the stratigraphic sequence. It must be noted
that these values are obtained on a calculation based on
thermal steady state and therefore can only be used as
maximum estimates of the re-heating caused by burial.
4.5. Thermal modeling of detrital populations:
implications for maximum burial temperatures
Combined, the presented evidence documents that
annealing related to burial in the Fiambalá Basin
played a minor role in the thermal history of the detrital
samples. However, thermal modeling of the P4
population from sample 050 (Tamberia Formation)
and sample 054 (Guanchin Formation) is presented in
order to further examine cooling following heating due
to burial between ca. 8 and 3.6 Ma (Fig. 6). T–t
constraints have been applied based on independent
data from the Sierra Pampeanas ranges presented by
Coughlin et al. [28] and Jordan et al. [65]. AFT data
from the Sierra Famatina range, directly to the west of
the Fiambalá Basin (SF; Fig. 2), suggest that this range
underwent two phases of cooling: the first one between
ca. 40 and ca. 60 Ma and the second at ca. 10 Ma.
Track length modeling suggests that a re-heating event
occurred between these two cooling episodes [28]; this
re-heating is attributed to burial by a hypothesized
foreland basin sequence [28]. Isopach map reconstructions and AFT data suggest that the Sierra Famatina
range, together with other ranges in the Sierra
Pampeanas, were once covered by a thick pile of
sediments that were eroded in the Miocene during the
main deformation and exhumation phase in this region
[28]. In particular, farther south, at ca. 29°S, Jordan et
al. [66] show the presence of a continuous foreland
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
93
Fig. 6. AFTSolve thermal modeling of population P4 in sample 050 and 054 from the Tamberia and Guanchin formations respectively. For T–t
constraints refer to the text. Lengths reported are corrected with respect to the c-axis for modeling purposes (see text for more details).
basin at ca. 20 Ma; this may also have formerly been
present in the north. In accord with this geological
evidence, a T constraint of 60–120 °C has been applied
at 2 Ma steps between 25 and 15 Ma to test the
hypothesis of cooling following burial caused by the
sediments of a foreland basin in the early Miocene
(Fig. 6). The best solution was obtained at 18 Ma;
acceptable and no fits were obtained when such
constraint was not applied for samples 050 and 054,
respectively.
Specific model input parameters for sample 050
(Tamberia Formation) include a T constraint of 10–
20 °C at ca. 8 Ma because the source for the Tamberia
sediments must have been at the surface at the time of
sediment deposition; a T constraint of 40–70 °C at
5.7 Ma was applied to test burial heating caused by
deposition of sediments belonging to the Tamberia
Formation; a T constraint of 50–86 °C at ca. 3.5 Ma was
applied to test burial heating caused by deposition of
sediments corresponding to the Tamberia, Guanchin and
Punaschotter formations. Modeling results show that the
best fit for the maximum burial T experienced by the
sample is ca. 60 °C (Fig. 6).
An additional modeling exercise was performed on
the P4 population from sample 054 from the Guanchin
Formation, stratigraphically above sample 050 (Figs. 3
and 6). The same general T–t constraints as for sample
050 were used. A T constraint of 10–20 °C was applied
at ca. 5.5 Ma and one at 35–72 °C was applied at ca.
3.5 Ma to test burial heating caused by deposition of
Guanchin and Punaschotter sediments. Our modeling
results show that the best fit for the maximum burial T
experienced by the sample is less than 60 °C (Fig. 6).
These results support the evidence presented above,
documenting negligible annealing due to post-depositional burial in the Fiambalá Basin.
A possible explanation for this negligible amount of
burial-heating annealing during the evolution of the
Fiambalá Basin could be the combination of a relatively
low and/or unsteady heat flow and syn-depositional
deformation. This last could have involved migration of
the basin depocenter during thrust propagation and
formation of growth strata. Such processes might have
prevented the clastic sequence from ever reaching a
thickness of ca. 4 km. Lack of seismic data and 3D
outcrops prevent us from holding such a scenario as the
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B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
sole responsible mechanism; however, evidence of synsedimentary deformation in the Fiambalá Basin may
support this hypothesis [35].
Interestingly, a similar example of minimally reset
detrital samples analyzed from a ca. 6-km-thick
stratigraphic sequence in the Angastaco Basin, northeast of the study area (Fig. 1), also documents
negligible annealing associated with post-depositional
re-heating. A combination of scenarios, similar to
those discussed here, was invoked to explain observations there [11].
4.6. Implications for provenance and sediment source
rock exhumation
The detrital thermochronologic data obtained from
the Tamberia, Guanchin, and Punaschotter formations
in the Fiambalá Basin provide important insights into
the evolution of the paleogeography of the surrounding ranges. Below, we interpret the detrital age
populations in terms of provenance proxies and as
representing cooling and exhumation events of the
sediment source.
Sample 003 from the lower part of the Tamberia
Formation has two main age populations (P): 121.9 ±
12.2 and 49.7 ± 4.6 Ma, respectively (Fig. 5). Sample
050 from the upper part of the Tamberia Formation
presents a wider age spectrum with five populations:
206.0 ± 47.3, 123.3 ± 11.6, 71. 4 ± 6.1, 37.2 ± 4.6, and
13.8 ± 1.7 Ma. While older populations are similar to
the first sample, the youngest middle Miocene
population (P1; Table 2) suggests that a new, different
source terrain began contributing sediment to the
Tamberia Formation at about 5.7 Ma. Sample 054
from the lower part of the Guanchin Formation
contains age populations of 167.8 ± 17.8, 92.0 ± 12.8,
43.0 ± 7.2, and 14.4 ± 3.1 Ma. Sample 053 from the
upper member of the Guanchin Formation is characterized by age populations of 217.5 ± 194.2, 127.1 ±
21.0, 81.7 ± 15.5, 36.3 ± 5.8, and 14.0 ± 2.8 Ma. Sample
177 from the distal Punaschotter Formation (location
Pc19 in Fig. 3) contains age populations of 92.9 ± 18.3,
57.2 ± 5.5, 30.0 ± 2.8, and 11.1 ± 0.9 Ma. A single
granite cobble, from the same location as the sandstone
sample 177, records a pooled age of 81.3 ± 3.4 Ma
(Table 1). Paleocurrent measurements from this
location unambiguously show provenance from the
N–NE (Fig. 3). The Punaschotter Formation reflects a
significant contribution (60%) of middle Miocene ages
(P1). P1 from sample 177 is slightly younger compared
to P1 of the underlying samples. However, detailed
examination of the youngest grains in sample 177
suggests volcanic contamination, responsible for making P1 in sample 177 younger (see Table A1 in the
Appendix) compared to other samples. Indeed, the
Gaussian distribution (Fig. 5) shows that the binomial
fitting curve contains two components, at ca. 10 and
15 Ma. The younger one could denote contamination
from reworked ashes while the older one is closer in
age to P1 detected in other samples.
Jurassic and Eocene ages are characteristic of
western sources (e.g., [10,28]). Such a source is also
supported by the late Eocene age recorded in samples
UP78-9 and UP78-3, collected immediately west of the
basin. However, Eocene ages are also characteristic of
eastern sources, as shown by sample 177 (sandstone
matrix of conglomerate) from the Punaschotter Formation. The Punaschotter conglomerates at this location are
derived from the east as indicated by paleocurrent data
(Fig. 3).
A Late Cretaceous age recorded by a single granite
cobble derived from the east in the distal Punaschotter
Formation (sample 177, location Pc19; Fig. 3) may also
represent an easterly source. Cretaceous cooling ages in
this region are typical of eastern sources that have been
influenced by events in the vicinity of the Cretaceous
Salta Rift, such as sectors including the Eastern
Cordillera further north [61] and parts of the northern
Sierra Pampeanas [40].
In contrast, middle Miocene ages, as recorded in the
P1 population are more typical of sources located within
the southern portion of the Puna Plateau (e.g. [61]) (Fig.
1). Grains recording the youngest detrital Miocene
population (ranging between 11.1 and 14.4 Ma) are
generally rounded and not as translucent as volcanically
derived crystals, but are instead more typical of grains
derived from crystalline basement rocks. This suggests
that this age population represents an exhumation signal
rather than a Miocene volcanic input (i.e. from ashes).
Although a limited amount of ash contamination may be
potentially present in the Punaschotter Formation, this
would not significantly alter the main population age.
Grains derived from unconsolidated volcanic sources
(i.e. ash flow) are typically euhedral and translucent (see
Table A1 in the Appendix). In particular, similar detrital
middle Miocene ages (P1) have been detected in the
Sierra de los Colorados area, immediately southwest of
the study area (Slc in Fig. 1), and are considered to
represent the exhumation of southern Puna sources [67],
thus corroborating our interpretation. In particular the
lower part of the northern vertical profile is characterized
by ages typical of middle Miocene detrital population
(P1). A sample from the AG range to the east of the basin,
at a similar elevation as the lower samples of the CN
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
95
Fig. 7. AFTSolve thermal modeling of basement sample UP60-2 (2889 m; lower part of the northern vertical profile), indicated in grey in Fig. 4 and in
bold in Table 1. The model was initiated at 200 Ma at T > 180 °C; T constraints of 170–90 °C, 140–60 °C and 17–70 °C were applied at 24 and 15 Ma
and 8 Ma, respectively, to examine cooling indicated by the age–elevation profile (Fig. 4) and the possibility that this part of the range might have
been at the surface by late Miocene time. Lengths reported are corrected for c-axis for modeling purposes. Refer to text for more details. The light
gray area corresponds to the acceptable fit, the dark gray area to the good fit and the dashed black line to the best fit. Note that lengths are corrected
for c-axis for modeling purposes explained in the text.
profile, shows similar middle Miocene ages, suggesting
that the two ranges have similar exhumation histories
and that they are not separated by major structures. Thus,
we hypnotize that rocks from structural positions similar
to the lower part of the northern and eastern vertical
profiles were the likely source for P1, first detected in the
upper Tamberia Formation (ca. 6 Ma). This is supported
by paleocurrent data from ca. 6 Ma strata documenting
the first input from northeastern sources at this time (Fig.
3). The same P1 detrital age population prevails in
samples from the Guanchin Formation. The composition
of this unit in turn is similar to the sediments from the
Punaschotter Formation, which is clearly sourced from
the southern Puna margin. By the time the Guanchin
Formation was deposited (3.6 < t < 5.7 Ma), the sediment
source had thus evolved toward the north, suggesting
that rocks from the vicinity of the northern profile
supplied sediments. In order to test the hypothesis that
the range to the northeast of the basin (CN vertical
profile) was the source for P1 in the Fiambalá sediments
track length modeling on a sample from the lower part of
the vertical profile is performed in the following.
4.7. Track length modeling of the northern vertical
profile: implications for the creation of a high relief
plateau margin
The AFT ages and track-length modeling from the
basement profile from the southern Puna margin suggest
that this area was exhumed during the early–middle
Miocene. Thermal modeling was performed on sample
UP60-2 (Fig. 7). The model was initiated at 200 Ma at
T > 180 °C; T constraints of 170–90 °C and 140–60 °C
were applied at 24 and 15 Ma, respectively, to examine
cooling indicated by the age–elevation profile (Fig. 4).
In order to test the hypothesis that the lower part of the
range was exposed by late Miocene time, a T constraint
between ca. 17 and 70 °C was applied at different times
from 10 to 6 Ma at intervals of 2 Ma. The best run was
obtained with the T constraint at 8 Ma and shows that the
sample could have cooled below ca. 60 °C by ca. 8 Ma.
We hypothesize that rocks characterized by ca. 14 Ma
ages were at the surface by ca. 6 Ma based on the model
of landscape development shown in Fig. 8. The region
between the vertical profile and the Fiambalá Basin does
not contain any mapped structures; therefore, exhumation on this flank of the range must occur by a
combination of rock uplift and headward erosion,
requiring the exhumation path to approach the surface
obliquely. However, isochrons representing the layer of
rock that passed through the ca. 110 °C closure isotherm
at a particular time extend subhorizontally; rocks with
roughly the same age as the base of the profile would be
exposed on the flank of the range prior to exposure of the
particular rock that was sampled. As headward erosion
removed the flank of the range, the area representing the
vertical profile continues to cool as it approaches the
surface; rock uplift due to the isostatic response to
erosion will continue even after tectonism has ceased.
Alluvial fans sourced from the growing topography will
onlap the eroding flank of the range.
5. Conclusions
Provenance and thermochronologic data from the
Fiambalá Basin at the southern margin of the Puna
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B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
Fig. 8. Schematic depiction of the exhumation pathways followed by the 1.8 km vertical profile at 3 time steps. Please note that the figure is not at
scale. For simplicity, surface topography is depicted as being in a steady state; dash lines represent the topography at various t-stages. Stars represent
the AFT sample locations; light grey swath represents position of the apatite partial annealing zone (PAZ). Lower temperature isotherms are more
strongly warped due to topographic effects [59]. 14 and 17 Ma isochrons depicts layers of rock that passed through the lower portion of PAZ. Note
that these are approximation values from the P1 population (ca. 14 Ma) and the pooled age of sample UP60-2 (Fig. 5). The 17 Ma AFT sample (black
star) crosses 60 °C isotherm at 8 Ma; by 6 Ma, samples with 14 Ma fission track age are exposed at the surface and deposited in the adjacent basin. At
this time, the relief must be at least 1.8 km. Curved grey arrows show cooling paths for the lowest and highest samples of the vertical profile; curvature
with respect to the surface is caused by effects of headward erosion and rock uplift. Sedimentary basin progressively onlaps topography as flank of
range retreats from the depocenter.
Plateau show that late Miocene–Pliocene sedimentary
rocks preserved in the basin are derived from the
progressive exhumation and erosion of the basinbounding ranges. This was coupled (i.e. contemporaneous and genetically linked) with a northward shift in
the evolution of the paleo-drainage system. Initially,
the primary source of the Tamberia Formation (ca.
8 Ma) was located to the west, in the Precordillera.
With the deposition of the upper Tamberia (sample
050) and Guanchin formations (3.6 < t < 5.7 Ma), a shift
of the source towards the north–northeast is recorded
by paleocurrent data and by the first appearance of
clast lithologies typical of the present-day southern
margin of the Puna Plateau.
B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
Our thermochronological data document that rocks
that supplied middle Miocene detrital apatites to the
upper Tamberia and Guanchin strata must have been
exposed at surface at about ca. 6 Ma. Middle Miocene
cooling ages are only characteristic of basement rocks
that constitute northern and eastern source areas. In
particular, 14 Ma ages are characteristic of the lowest
part of the vertical profile to the north, this suggests that
this structural level of the range (ca. 2300 m) was at the
surface at ca. 6 Ma. Consequently, at least the entire
crustal column that presently overlies this sample (crestal
elevation of 4072 m) must had also been exhumed by
then (Fig. 8). The crestal elevation is a minimum
estimate, as there has likely been erosion during the last
6 Ma. Moreover, the fact that the same ages recorded in
the 6 Ma basin strata are still recorded by the range to the
north suggests that not enough tectonic and or erosional
exhumation has occurred since then to be recorded by the
AFT system. Assuming 60 °C as the upper limit of the
PAZ, a mean surface temperature of ca. 10 °C and a
conservative 20 °C/km paleo-geothermal gradient, less
than 3 km of upper crust would have been exhumed by
erosion since middle Miocene time.
Our data show that the southern margin of the Puna
Plateau expressed an high relief by late Miocene time,
when sedimentary strata hosting AFT detrital ages of
14 Ma (P1) were deposited in the Fiambalá Basin.
Rocks of the northern and eastern ranges that provided
sediments to the basin in late Miocene time are
presently at ca. 2300 m. Although our new data may
indicate a relief similar or higher than present in the
source region during the latest Miocene, they do not
provide direct information on absolute paleo-elevations. Instead, our data may document a minimum
crestal height of ca. 1800 m above the elevation of the
Fiambalá Basin at that time. However, more detailed
information on paleo-elevation and relief conditions are
not available for this region in order to further constrain
the paleo-geographic evolution. Paleo-elevation proxies
from the Bolivian Altiplano have been used to suggest
that present plateau elevations further north may have
been acquired within the last 10 Ma [2–4], implying a
rapid uplift event subsequent to the main phase of
shortening and crustal thickening. Indeed, this timing
for wholesale plateau uplift broadly coincides with an
inferred isostatic uplift event following mantle delamination in the southern Puna Plateau sometime between
8 and 3 Ma [16,17].
Interestingly, sedimentologic, thermochronologic,
paleontologic, and oxygen-isotope data in Mio-Pliocene
sedimentary sequences deposited in other intramontane
basins along the eastern margin of the Argentine Puna
97
Plateau record a similar paleogeographic reorganization
with evolution of headwaters from the west to the north
and north–east [11,24,25,68,69]. In particular, in the
neighboring El Cajon Basin (Fig. 1), a reorganization of
the source and basin depositional environment is
recorded by both seismic reflection and thermochronological data at ca. 6 Ma and is interpreted to result from
plateau–margin growth [13].
Cooling ages from basement ranges in the southern
Puna Plateau and detrital AFT data from adjacent
intramontane basins [11,13] suggest that the main
phase of exhumation was prior to a late Miocene–early
Pliocene event during which significant changes
occurred in paleo-drainage conditions. In particular,
our data suggest that range uplifts existed at the
present-day southern Puna margin by late Miocene
time and were the result of Oligo-Miocene distributed
shortening and exhumation [13]. This is in agreement
with data from the Eastern Cordillera of Argentina to
the northeast [61] and the Bolivian Altiplano [70]. If a
genetic link between shortening, crustal thickening,
exhumation, and uplift, exists, then a high-elevation
and/or high relief region may already have been in
place in the Puna region by Oligo-Miocene time.
Although not recorded by AFT, there certainly has
been some amount of rock uplift since then, as
documented by regional paleo-drainage reorganization
and Pliocene reverse faulting observed in the Fiambalá
Basin and other intramontane sedimentary basins along
the plateau margin [11,25,71].
Thus, while reverse-fault bounded ranges and
intervening, internally drained basins are a typical
feature of the present-day plateau morphology, the
foundation for this setting may already have been
attained in Oligo-Miocene time. The filling of these
basins and consequent reduction of local relief within
the present plateau region also began at that time and has
continued since then. However, the pronounced changes
at the immediate eastern and southern plateau margin in
late Miocene–early Pliocene time suggest that wholesale
plateau uplift may have affected this region, subsequent
to the earlier period of distributed shortening and crustal
thickening. This younger event is not reflected in the
AFT data, presumably due to the arid climate and
associated reduced erosion rates in the Puna region; the
southern Puna Plateau margin has experienced less than
ca. 3 km exhumation since the middle Miocene.
Acknowledgements
We thank Glen R. Murrell for his fundamental help
with part of fission track analysis, A. Villanueva Garcia
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B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100
and J. Sosa Gomez for their hospitality and help in the
field. We appreciate the constructive reviews of two
anonymous reviewers as well as the useful comments of
Teresa Jordan on an earlier version of this manuscript.
The Alexander von Humboldt Foundation is kindly
acknowledged for supporting B. Carrapa's research at
Potsdam. We thank the German Science Foundation for
financial support (Leibniz-Prize to M. S.) as well as the
A. Cox Fund (M.S.), Stanford University.
[13]
[14]
[15]
[16]
Appendix A. Supplementary data
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.
epsl.2006.04.010.
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ScienceDirect - Earth and Planetary Science Letters : Cenozoic orogenic g...gy in the Fiambalá Basin, southernmost Puna Plateau margin (NW Argentina)
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Earth and Planetary Science Letters
Volume 247, Issues 1-2 , 15 July 2006, Pages 82-100
doi:10.1016/j.epsl.2006.04.010
Copyright © 2006 Elsevier B.V. All rights reserved.
This Document
Abstract
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Cenozoic orogenic growth in the Central Andes:
Evidence from sedimentary rock provenance and Actions
E-mail Article
apatite fission track thermochronology in the
Fiambalá Basin, southernmost Puna Plateau margin (NW Argentina)
B. Carrapa
aInstitut
, a,
, M.R. Streckera,
and E.R. Sobela,
für Geowissenschaften, Universtität Potsdam, 14476 Golm, Germany
Received 10 November 2005; revised 2 March 2006; accepted 6 April 2006. Editor: V. Courtillot. Available online 12
June 2006.
Abstract
Intramontane sedimentary basins along the margin of continental plateaus often preserve strata that
contain fundamental information regarding the pattern of orogenic growth. The sedimentary record of the
clastic Miocene–Pliocene sequence deposited in the Fiambalá Basin, at the southern margin of the Puna
Plateau (NW Argentina), documents the late Miocene paleodrainage evolution from headwaters to the
west, towards headwaters in the ranges that constitute the border of the Puna Plateau to the north. Apatite
Fission track (AFT) thermochronology of sedimentary and basement rocks show that the southern Puna
Plateau was the source for the youngest, middle Miocene, detrital population detected in late Miocene
rocks; and that the margin of the Puna Plateau expressed a high relief, possibly similar to or higher than at
present, by late Miocene time. Cooling ages obtained from basement rocks at the southern Puna margin
suggest that exhumation started in the Oligocene and continued until the middle Miocene. We interpret
the basin reorganization and the creation of a high relief plateau margin to be the direct response of the
source–basin system to a wholesale surface uplift event that may have occurred during the late Cenozoic
in the Puna–Altiplano region. At this time coeval paleodrainage reorganization is observed not only in the
Fiambalá Basin, but also in different basins along the southern and eastern Puna margin, suggesting a
genetic link between the last stage of plateau formation and basin response. However, this event did not
cause sufficient exhumation of basin bounding ranges to be recorded by AFT thermochronology. Our new
data thus document a decoupling between late Cenozoic surface uplift and exhumation in the southern
Puna Plateau. High relief achieved at the Puna margin by late Miocene time is linked to Oligocene–
Miocene exhumation; no significant erosion (< 3 km) has occurred since in this arid highland.
Keywords: plateau; sedimentary basin; provenance; thermochronology; exhumation; uplift; relief
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ScienceDirect - Earth and Planetary Science Letters : Cenozoic orogenic g...gy in the Fiambalá Basin, southernmost Puna Plateau margin (NW Argentina)
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Volume 247, Issues 1-2 , 15 July 2006, Pages 82-100
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