Geological Society of America
Special Paper 378
2004
Detecting provenance variations and cooling patterns within the
western Alpine orogen through 40Ar/ 39Ar geochronology on detrital
sediments: The Tertiary Piedmont Basin, northwest Italy
B. Carrapa*
J. Wijbrans*
G. Bertotti*
Vrije Universiteit Amsterdam, Faculteit der Aardwetenschappen, De Boelelaan 1085, 1081HV Amsterdam, The Netherlands
ABSTRACT
The Tertiary Piedmont Basin is a synorogenic basin located on the internal side of
the Western Alps. Because of its key position, the Tertiary Piedmont Basin represents
an important record of processes occurring in the Alpine retrowedge for over the last
30 m.y. 40Ar/39Ar geochronology has been applied to detrital white micas as a provenance tool and to derive information on cooling and exhumation patterns within the
surrounding orogen. The age distribution in the detritus shows that in the Oligocene
the clastic sediments were fed mainly from a southern source area (Ligurian Alps)
that widely records high pressure (HP) Alpine metamorphism (40–50 Ma) and, in
part, Variscan metamorphism (ca. 320 Ma). From the Miocene, the main source area
gradually moved from the south to a western Alpine provenance characterized by
strong Late Cretaceous (70 Ma) and Early Cretaceous (120 Ma) signals. This enlargement in the source is likely linked to an evolution of the main paleodrainage system
into the basin. From the Serravallian, Variscan ages reappear; this is attributed to the
exposure of the Argentera Massif as a new source for the Tertiary Piedmont Basin.
The lack of thermal overprinting of the main detrital signals through time suggests
that the western Alpine orogen has been regulated by episodic fast cooling and exhumation events followed by periods of slower erosion. Also, detrital 40Ar/39Ar Cretaceous signals in Miocene and Present sediments suggest the presence of real Eoalpine
events in the Alps.
Keywords: Western Alps, provenance, 40Ar/39Ar geochronology, cooling, exhumation.
INTRODUCTION
consequence, clastic sediments are the only remaining direct
evidence of the original source rocks outcropping at the time
of sediment deposition. Therefore, they provide a record of the
original setting of mountain belts through time.
The Tertiary Piedmont Basin, located within the internal
western Alpine Arc (retrowedge; Beaumont et al., 1996) in
northwest Italy (Fig. 1), contains up to 4 km of clastic sediments (Fig. 2). The Tertiary Piedmont Basin and the western
Alpine arc formed as a result of the Tertiary European-African
plate collision (e.g., Platt et al., 1989). The Tertiary Piedmont
Synorogenic clastic sediments contained in sedimentary
basins preserve a record of the exhumation kinematics of
an orogen. Because of erosional and tectonic processes, the
original rocks outcropping in the orogen no longer exist. As a
*Present address, Carrapa (corresponding author)—Universität Potsdam,
Institut für Geowissenschaften, Postfach 601553, 14415 Potsdam, Germany,
carrapa@geo.uni-potsdam.de. E-mails: Wijbrans—wijj@geo.vu.nl; Bertotti—bert@geo.vu.nl.
Carrapa, B., Wijbrans, J., and Bertotti, G., 2004, Detecting provenance variations and cooling patterns within the western Alpine orogen through 40Ar/39Ar geochronology on detrital sediments: The Tertiary Piedmont Basin, northwest Italy, in Bernet, M., and Spiegel, C., eds., Detrital thermochronology—Provenance analysis,
exhumation, and landscape evolution of mountain belts: Boulder, Colorado, Geological Society of America Special Paper 378, p. 000–000. For permission to copy,
contact editing@geosociety.org. © 2004 Geological Society of America.
69
70
B. Carrapa, J. Wijbrans, and G. Bertotti
Figure 1. Geological map of the
study area; TPB—Tertiary Piedmont Basin (study area), VG—Voltri Group, LA—Ligurian Alps,
AGM—Argentera Massif, DM—
Dora Maira, GP—Gran Paradiso,
SL—Sesia Lanzo.
Basin is well suited for investigation of a substantial part of the
complex Alpine orogen because it is one of the main sedimentary basins collecting clastic sediments produced by cooling and
exhumation and erosion of the internal Western Alps (including
the Ligurian Alps). The Tertiary Piedmont Basin stratigraphy is
well preserved, exposed, and documented (e.g., Gnaccolini et al.,
1998, and references therein; Fig. 2). These data, together with
paleocurrent directions data (Fig. 3A) on the study area, allowed
a good sample strategy (Fig. 3B).
For the present study, we have applied 40Ar/39Ar geochronology to detrital white micas derived from samples selected from
the entire Tertiary Piedmont Basin stratigraphy (Lower Oligocene–Upper Miocene). To extend the covered time interval from
the oldest Tertiary Piedmont Basin sediments to the present, we
sampled sands from three of the main rivers currently draining
the internal side of the southwestern Alps, which are the main
sources of Tertiary Piedmont Basin sediments (Fig. 3B).
Detrital mineral thermochronology on present-day river
sands has been largely applied to different tectonic settings to
characterize the present river drainage pattern (e.g., Heller et al.,
1992). Dating minerals from present-day river sediments provides new information on the geochronological signal currently
recorded at the surface in the southwestern margin of the Dora
Massif, the Argentera Massif, and on the Ligurian Alps.
The major objective of this work is to obtain new information on: (1) Provenance of the clastic sediments; (2) Cooling
patterns due to unroofing of the original source rocks related to
past denudation and/or tectonic and erosional processes; and (3)
potential information on the timing of HP and ultra-high pressure
(UHP) metamorphism in the Western Alps.
White micas are well suited for this geochronological
approach because of their high K content, their widespread
occurrence in different lithologies, and their resistance against
mechanical breakdown. Furthermore, the closure temperature
of white micas (350–420 °C; e.g., Hames and Bowring, 1994;
Kirschner et al., 1996; Kohn et al., 1995; von Blanckenburg et
al., 1989) is high enough to avoid substantial overprinting due
to short-lived thermal disturbances and sedimentary burial. Also,
40
Ar/39Ar dating of white mica is a well-tested technique that
records the time in which the investigated minerals pass through
a closure temperature of 350–420 °C (Najman et al., 1997; von
Eynatten and Wijbrans, 2002; White et al., 2002).
Research in the Himalayas (e.g., Harrison et al., 1993;
Najman et al., 2001; White et al., 2002), in the Central Alps
(e.g., Bernet et al., 2001; Spiegel et al., 2001; von Eynatten and
Wijbrans, 2002), and in western North America (e.g Heller et
al., 1992) has demonstrated the potential of the geochronological approach for both provenance and tectonothermal evolution
studies. In particular, studies on the Central Alpine sedimentary
record and on the exhumation of crystalline rocks from the Alpine
orogen have suggested rapid episodic exhumation (e.g., Hurford
et al., 1991) followed by a relatively steady state of exhumation
(e.g., Bernet et al., 2001; Schlunegger and Willett, 1999). So far,
however, little data exist (Carrapa et al., 2003) on the depositional
counterpart of the western Alpine erosion. Our data set of over
500 individual white mica analyses is well constrained due to
the proximity of the source to the basin and sheds new light on
the reconstruction of the thermotectonic evolution of the western
Alpine Arc for a time period of over 30 m.y.
GEOLOGICAL SETTING
The Tertiary Piedmont Basin is located on the boundary
between the internal Alpine domain, consisting of deep crustal
rocks, and the Apennine domain, constituted mainly by upper
Cretaceous–Eocene flysch (Fig. 1). The Tertiary Piedmont Basin
is flanked to the south by the Ligurian Alps and to the west and
north by Plio-Quaternary sediments, which in turn are bounded
Detecting provenance variations and cooling patterns
to the west by metamorphic units belonging to the internal western Alpine domain (Fig. 1).
The Orogen Surrounding the Tertiary Piedmont Basin
The western Alpine arc surrounding the Tertiary Piedmont
Basin includes the Ligurian Alps to the south and the Western
71
Alps (sensu stricto) to the west. The western Alpine arc contains
HP and UHP rocks that experienced deep burial during the
Alpine orogeny and subsequent rapid exhumation, such as the
Dora Maira and Gran Paradiso massifs to the west (Hurford et al.,
1991; Hurford and Hunziker, 1989; Rubatto and Hermann, 2001)
and the Voltri Group to the south (Brouwer, 2000). All these
rocks constitute potential sources of sediments for the Tertiary
Piedmont Basin.
Figure 2. (continued on next page) A: Geological framework of the study area modified after Gnaccolini et al. (1998). 1—Pliocene to Recent
deposits; 2—Messinian deposits; 3—Langhian to Tortonian siliciclastic and carbonate shelf to slope deposits; 4—Late Burdigalian to Tortonian
mainly turbidite succession (only Burdigalian in the eastern sector of the figure); 5—Late Oligocene to Burdigalian turbidite systems and hemipelagic mudstones; 6—Late Eocene to Early Oligocene deposits: (a) alluvial to coastal conglomerates, shallow marine sandstones and hemipelagic mudstones, (b) slope and base-of-slope, resedimented conglomerates, and (c) mainly turbidites; 7—Late Eocene to Tortonian siliciclastic
deposits of the northwestern Apennines–Monferrato–Torino Hill wedge; 8—Alpine and Apennine allochthonous units; 9—depocenter axis of the
Plio-Quaternary basins; 10—buried thrust-front of the Torino Hill–Monferrato–northwestern Apennine wedge; 11—buried, southvergent backthrusts of the Monferrato, active from Messinian onward; 12—buried, pre Burdigalian backthrusts of the Western Alps (as inferred from Roure
et al., 1990); 13—faults: SV—Sestri-Voltaggio; VVL—Villalvernia-Varzi line; I: Bagnasco–Ceva–Bastia Mondovì transect; II: Millesimo–Monesiglio–Somano transect; III: Dego–Torre Bormida–Alberetto della Torre transect; IV: Spigno Monferrato–Cessole transect; V: Montechiaro
d’Acqui; VI: Cavatore; VII: Visone. The square corresponds to the area of the paleocurrent study of Gnaccolini and Rossi (1994). B: Oligo-Miocene depositional sequences (A, B1–B6, C1–C6) in the study area after Gelati et al. (1993). 1—mudstones, locally with thin-bedded turbidites
(a); 2—turbidite systems (sand/mud ratio from very high to = 1; locally, conglomerates); 3—resedimented ophiolite breccia; 4—olistolith-bearing pebbly mudstones; 5—shallow-water carbonates; 6—alluvial conglomerates, coastal sandstones, and conglomerates, freshwater mudstones
(a); 7—Pre-Cenozoic rocks; 8—sequence boundary; 9—fault. The square inset is mainly based on Cazzola et al. (1981), Cazzola and Sgavetti
(1984), and Cazzola and Fornaciari (1990). The ages of the unconformities and sequence boundaries are based on planktonic foraminifers and
calcareous nannofossils and correlate with the third order global cycles boundaries of Haq et al. (1988). C: Stratigraphic scheme modified after
Gelati (1968).
72
B. Carrapa, J. Wijbrans, and G. Bertotti
Figure 2. (continued).
The Ligurian Alps
The Ligurian Alps bound the Tertiary Piedmont Basin to
the south. They consist of a nappe stack (Vanossi et al., 1984),
including the following:
1. The meta-ophiolite Voltri Group, which is a remnant of
the Piedmont-Ligurian ocean and consists of a cover sequence
constituted by metasedimentary rocks (calc-schists, mica schists,
quartz schists, and metabasalts) and a basement sequence of
Mg-gabbros, Fe-Ti–gabbros, and serpentinites (Messiga, 1984).
The Voltri group experienced a complex retrograde metamorphism ranging from peak eclogitic and blueschist facies toward
greenschist facies (Cimmino et al., 1981; D’Antonio et al., 1984;
Messiga et al., 1989; Messiga and Scambelluri, 1991). Scarse KAr geochronology on white micas from presently outcropping
gneisses of the Voltri group give cooling ages of 31–41 Ma (Hunziker et al., 1992; Schamel and Hunziker, 1977; Fig. 4). 40Ar/39Ar
dating on white mica from the Beigua serpentinite unit (Voltri
Group) gives ages of 45 ± 2 Ma (data cited in Brouwer, 2000).
2. The Montenotte Nappe (Piemontese unit), which is
derived from the transitional domain between the ocean and the
paleo-European continental margin (Vanossi et al., 1984). This
unit experienced HP/low temperature (LT) Alpine metamorphism
with a re-equilibration in blueschist facies (Messiga, 1981). No
chronological data is available on the age of the metamorphism.
3. The Briançonnais complex, which is derived from thinned
paleo-European continental crust and includes the Variscan Crystalline Massifs (e.g., Calizzano–Savona Massifs). These units
have been affected by Alpine greenschist facies metamorphism
(e.g., Messiga et al., 1992, and references therein). The Variscan
Crystalline Massifs are characterized by 40Ar/39Ar ages ca. 380–
240 Ma (Hunziker et al., 1992; Fig. 4). Zircon fission-track ages
on the Briançonnais domain yielded ages between 180–125 and
31 Ma (Vance, 1999).
The Western Alps
The Western Alps consist of different domains including
numerous units. In the following, we will consider only those
Detecting provenance variations and cooling patterns
73
Alpine units affected by cooling and exhumation during the formation of the Tertiary Piedmont Basin and that therefore constitute a
possible source for the Tertiary Piedmont Basin sediments.
The Internal Massifs (e.g., Dora Maira, Gran Paradiso;
Fig.1) belong to the Penninic units, which represent the European
continental basement and form the core of the western Alpine
chain. They were affected by Eoalpine HP or UHP metamorphism during Alpine subduction (e.g., Chopin, 1984; Chopin
and Monié, 1984; Compagnoni and Lombardo, 1974; Dal Piaz,
1999; Monié and Chopin, 1991; Paquette et al., 1989; Polino et
al., 1990; Scaillet et al., 1992) and subsequent exhumation. The
timing and mechanism of the HP metamorphism and kinematics of exhumation of the Internal Massifs are still debated (e.g.,
Brouwer, 2000; Compagnoni et al., 1995; Hurford et al., 1991;
Michard et al., 1993; Rubatto et al., 1999; Rubatto and Hermann,
2001; von Blanckenburg et al., 1989).
The Dora Maira Massif is mainly characterized by 40Ar/39Ar
age ranges of 45–30 Ma, 85–60 Ma, and ≥120 Ma (Monié and
Chopin, 1991; Scaillet et al., 1992; Scaillet et al., 1990; Fig. 4).
Determination of cooling and relative exhumation kinematics for
the UHP rocks of the Dora Maira has not been totally resolved
(Gebauer et al., 1997; Hurford et al., 1991; Michard et al., 1993).
One important issue in the Western Alps exhumation evolution is
the interpretation of ages ~70–120 Ma. Different geochronometers (U-Th-Pb on zircons and monazites, U/Pb on whole rock,
and 40Ar/39Ar on white micas) from HP rocks of the Dora Maira
record ages ranging between 70–120 Ma (Monié and Chopin,
Figure 3. A: Paleocurrent directions modified after Gnaccolini and Rossi (1994); location given in B. B: Enlargement of the study area with location of the analyzed samples. The inset area corresponds to the study on paleocurrent directions of Gnaccolini and Rossi (1994) (Fig. 3A).
74
B. Carrapa, J. Wijbrans, and G. Bertotti
Figure 4. Probability distribution diagrams
of 40Ar/39Ar ages on white micas (single/total
fusion ages) in the Tertiary Piedmont Basin
surrounding source areas based on literature
data from Stöckhert et al. (1986), Hurford et
al. (1991), Hunziker et al. (1992), Scaillet et
al. (1992), Ruffet et al. (1997), and Cortiana
et al. (1998). For legend, see Figure 1.
1991; Paquette et al., 1989; Scaillet et al., 1992; Scaillet et al.,
1990), partially reset by a later Eocene-Oligocene greenschist
phase (Chopin and Maluski, 1980; Monié, 1985). A contrasting
view is that cooling of the UHP in the Dora Maira massif occurred
at 35–38 Ma (Gebauer et al., 1997; Rubatto and Hermann, 2001)
while 70–120 Ma 40Ar/39Ar ages are ascribed to incorporation of
excess 40Ar (Arnaud and Kelley, 1995; Kelley et al., 1994).
The Gran Paradiso massif was affected by HP metamorphism
during the Alpine orogeny. Rb-Sr dating on white micas yielded
ages ca. 34 Ma (Freeman et al., 1997), while zircon fission-track
(ZFT) ages are ca. 30 Ma (Hurford and Hunziker, 1989). Apatite
fission-track (AFT) ages are ca. 20 Ma, indicating that the massif was at a few kilometers depth in the early Miocene (Hurford
and Hunziker, 1989), possibly constituting a source for Tertiary
Piedmont Basin sediments in late Miocene time.
A further potential source for the Tertiary Piedmont Basin is
the Sesia Lanzo zone and the Argentera Massif. The first belongs
to the Austroalpine basement and was part of the Adriatic plate,
while the second belongs to the Provençal Delphinois domain.
The Sesia Lanzo zone was affected by Paleogene-Neogene exhumation (Hurford et al., 1991). Timing of HP metamorphism in
the Sesia Lanzo Zone has been argued to be between 130 Ma
(Inger et al., 1996; Oberhänsli et al., 1985; Ruffet et al., 1997;
Stöckhert et al., 1986) and 70–40 Ma (Cliff et al., 1998; Cortiana
et al., 1998; Rubatto et al., 1999; Fig. 4). A phase of rapid exhumation of the Sesia Lanzo zone occurred during the Oligocene
(25–30Ma) Insubric phase (Hurford et al., 1991; Schmid et al.,
1989).
The Argentera Massif is one of the largest external crystalline massifs of the Western Alps, and it is the most proximal to
the Tertiary Piedmont Basin. The Argentera Massif is made of
Variscan basement overlain by Upper Carboniferous, Permian,
and Triassic series (Menot et al., 1994). The massif was overthrust
by the Penninic nappes during the Oligocene and exhumed and
eroded in Miocene time (Bigot-Cormier et al., 2000). 40Ar/39Ar
dating on the Argentera Massif give Variscan ages (e.g., Monié
and Maluski, 1983; Fig. 4) while apatite fission-track ages show
that the Massif was at few kilometers from the surface during the
Late Miocene–Pliocene (Bigot-Cormier et al., 2000).
The Tertiary Piedmont Basin
Sedimentation in the Tertiary Piedmont Basin started with a
transgression dated as Late Eocene in the east and as Late Oligocene in the west (Fravega et al., 1994; Lorenz, 1984; Vannucci
et al., 1997) and continued until Late Miocene (e.g., Gelati and
Detecting provenance variations and cooling patterns
75
Formation, Lequio Formation), tabular bodies are formed that
can be traced through the whole basin, reaching a thickness of
up to 2000 m (Fig. 2B, 2C). This reorganization is also recorded
by uniform sandstone composition (Gnaccolini and Rossi, 1994).
In particular, rock fragments of Miocene (from the Cortemilia
Formation up) sediments mainly comprise quartzite, micashist,
orthogneiss, acid metavulcanite, phyllite, carbonatic rock and
subordinate metabasic rock, serpentinite, and phyllite, indicating mainly a western Alpine source. Also, a detailed sandstone
petrographic study on the Cassinasco Formation by Caprara et al.
(1985) shows that sandstones from this formation are very rich
in all types of metamorphic lithics and indicates a composite collision orogen source (e.g., Dickinson and Suczek, 1979), which
could correspond to the Alpine Penninic nappe.
METHODOLOGY
Concepts for the Interpretation of Detrital Minerals Ages
Figure 5. Sketch showing: A: continuous cooling and exhumation, erosion of the source, and the correspondent geochronological signature
produced in the clastic infill; B: rapid cooling and exhumation followed by slower erosion and the correspondent geochronological signature produced in the clastic infill. For both scenarios, nappe stacking
took place at a temperature entirely below ~350 °C.
Gnaccolini, 1996; Mutti et al., 1995). Sedimentation continued
until the Plio-Pleistocene in the surrounding Po Plain. Initially,
transitional (fluvial, fan deltas) environments characterized
sedimentation with the deposition of a mainly conglomeratic
sequence up to 600 m thick, known as the Molare Formation
(Fig. 2B, 2C) (e.g., Gnaccolini et al., 1990; Turco et al., 1994).
Sediments from the Molare Formation were locally sourced from
the Ligurian Alps (Gnaccolini et al., 1990; Barbieri et al., 2003).
These sediments pass stratigraphically into the Rocchetta and
Monesiglio formations (lower Oligocene pro parte-Aquitanian;
Gnaccolini et al., 1998, and references therein). These sediments
consist of transitional facies (Rocchetta Formation) and turbiditic sandstones (Monesiglio Formation) in the lower part and by
pelagic mudstones in the upper part, for a total of up to 1500 m
(Fig. 2B, 2C). They are indicative of the progressive deepening
of the Tertiary Piedmont Basin. The Rocchetta Formation in
the eastern sector includes a redeposited sandy body known as
Cassinelle Sandstones of Rupelian age. Facies characteristics,
petrographic data, and paleocurrent directions obtained from the
Rocchetta and Monesiglio formations suggest a provenance from
both southern sectors, mainly the Briançonnais domain of the
Ligurian Alps and the Voltri Group, and western sectors (Gelati et
al., 1993; Gnaccolini and Rossi, 1994).
From the Miocene, sedimentation became more homogeneous (Gelati et al., 1993) with paleocurrent directions indicating dominant flow to the east (Gnaccolini and Rossi, 1994; Fig.
3A). From the late Burdigalian (Cortemilia Formation) up to
the Serravallian-Tortonian (Cassinasco Formation, Murazzano
Source rocks, each with characteristic geochronological
signals, will result in the contribution of different ages to the
basin infill. Potentially, mica 40Ar/39Ar ages from different stratigraphic levels of the Tertiary Piedmont Basin can be interpreted
as recording variations in the original source rock cooling ages.
Therefore, 40Ar/39Ar age populations reflect the contribution in
ages present in the original source area surface at the time of sediment deposition. The major assumption underlying the geochronological approach is that of a short, and therefore negligible,
time span between erosion in the belt and deposition of clastic
sediments in the correspondent sedimentary basin (Brandon and
Vance, 1992; Heller et al., 1992). This assumption is important
for the calculation of cooling rates. We argue that this assumption
is justified in the case of the Tertiary Piedmont Basin because of
the close proximity of the source and basin.
In general, two different end member scenarios can be
envisaged for the potential Tertiary Piedmont Basin source area
cooling and exhumation pattern and related 40Ar/39Ar ages in
the Tertiary Piedmont Basin sediments. The first one involves
tectonic nappe stacking taking place entirely at temperatures in
excess of ~350 ºC. In this case, exhumation of the nappe stack
would create a younging of cooling ages in the sediments (detrital ages) due to continuous upward movements of crustal rocks
(e.g., Neubauer et al., 1996; Bernet et al., 2001) (Fig. 5A). In the
sedimentary record, this would result in a decreasing of detrital
ages (age populations or peaks of ages) up-sequence (e.g., “moving peaks” of Brandon and Vance, 1992). However, if cooling
and exhumation ceased following an initial pulse of rapid cooling, and erosion was insufficient to unroof deeper crustal levels
(recording younger cooling ages), constant cooling ages in the
detritus would be detected over a substantial period of time (e.g.,
“static peaks” of Brandon and Vance, 1992) (Fig. 5B).
The second scenario involves tectonic nappe stacking taking place entirely at temperatures less than ~350 ºC. In this case,
exhumation and erosion would produce ages recording old
76
B. Carrapa, J. Wijbrans, and G. Bertotti
cooling processes while the time of tectonic nappe stacking
would not be recorded by the Ar system, because it would have
occurred at a temperature lower than the closure temperature
(T) of the system (T < ~350 ºC). As we are dealing with the
integrated contribution of minerals over a large source area,
any combination of the proposed scenarios may occur. Thus, by
looking at changes in the main detrital age populations, we can
obtain information on different source rock contributions and on
different cooling patterns (e.g., Harrison et al., 1993; White et
al., 2002; von Eynatten and Wijbrans, 2002). For provenance discrimination, we use variations in main detrital age populations.
Analytical Technique
40
Ar/39Ar geochronology has been applied to detrital phengites from over 60 samples from selected stratigraphic units of
the Tertiary Piedmont Basin, ranging in age from Oligocene to
Tortonian and to present-day river sands, with an average of
seven samples for each formation and two samples for each river
(Tables A1 and A2). Single fusion was applied on ~10 single
crystals (ranging between 250–500 µm in size) for each selected
sample, for a total of over 500 individual experiments. Step heating was applied to 10 single grains ranging between 500 and
1000 µm in size, derived from different formations and rivers, to
check the internal distribution of radiogenic 40Ar in each sample.
Only experiments concordant within 95% confidence intervals
(i.e., MSWD < 2.5) have been used to derive plateau ages. The
ages obtained on Tertiary Piedmont Basin clastic phengites are
interpreted to represent the time of isotopic closure during cooling of the crystalline source through 350–420°C, as temperatures
reached during the main metamorphic events of the basement
rocks were generally higher than ~500 °C in the whole source
area (e.g., Messiga and Scambelluri., 1991; Gebauer, 1999).
The 40Ar/39Ar experiments were carried out with the
VULKAAN laserprobe at the Isotope Geology Laboratory of
the Vrije Universiteit in Amsterdam, following laser extraction
and mass spectrometry methods for the laserprobe described
by Wijbrans et al. (1995). The irradiation was carried out in
the cadmium-lined CLICIT facility of the TRIGA reactor of
the Oregon State University Radiation Center. Irradiation times
were 7 h for three different irradiations VU32, VU36, VU41.
Correction factors for interferences of Ca and K isotopes were
0.000673 for 39Ar/37Ar, 0.000264 for 36Ar/37Ar, and 0.00086 for
40
Ar/39Ar, respectively. These values were determined using zero
age K-feldspar and anorthite glass. After irradiation, a J curve
was derived for individual samples by interpolation between five
single fusion experiments on every flux monitor. As flux monitor standards for this project, we used Taylor Creek sanidine (for
VU32) and DRA (Drachenfels trachite [Wijbrans et al., 1995;
Steenbrink et al., 1999]) sanidine (for VU36-41; Steenbrink et
al., 1999), with an age of 28.34 ± 0.16 Ma and 25.26 ± 0.14 Ma,
respectively. These values are compatible with the set from Renne
et al. (1998), based on biotite GA1550 (at a K/Ar age of 98.79
± 0.69 Ma). In the present study, system blanks were determined
after every five unknowns. The unknowns were corrected for the
interpolated blanks at the time of analysis of the unknown, and
the 2σ error on the blank was further used for the error calculation
of the unknown. 40Ar intensities for the analyzed samples were in
the order of >100 times the blanks (see Wijbrans et al. [1995] for
further details on mass spectrometer sensitivity). The discrimination factor was on average equal to 1.006 (see Kuiper [2003] for
further details on discrimination factor calculation). Note that the
2σ errors reported in Table A2 do not include the uncertainties in
J and uncertainties related to the age of the standards (the average
of J-related errors is in the order of 0.3%). The exclusion of the Jrelated errors in the analytical errors reported in Table A2 enables
a better comparison between samples (Foland, 1983). For further
details on the calculation of the ages and related errors reported
in Table A1, refer to Koppers (2002).
Probability distribution diagrams (Sircombe, 1999; Sircombe, 2000) have been used to identify the main populations
of detrital ages present in different formations of the Tertiary
Piedmont Basin clastic infill and present-day river sands. The
probability distribution curves are compiled by summing the
Gaussian distribution of each individual measurement, which
is defined by the age and its error (e.g., Sircombe, 2000). Some
formations (e.g., Rocchetta-Cassinelle, Cortemilia-Paroldo,
Murazzano-Cassinasco) have been combined because they are
synchronous and contain similar sedimentological patterns
(similar depositional environment and/or similar petrographic
compositions and paleocurrent directions). As we are using the
age probability distribution mainly as an indication of provenance, the major conclusions of this research are independent
of any possible 40Ar excess problems in the source rocks. When
addressing the question of differential exhumation and cooling of
the source rocks, we assess systematic age differences in the mica
populations at different stratigraphic levels. Biostratigraphic ages
of the formations indicated in the following paragraphs are given
using the stratigraphic scheme of Figure 2C and the geological
timescale of Berggren et al. (1995).
RESULTS
Results from Tertiary Piedmont Basin Clastic Minerals
The geochronological data set is presented in Figure 6 and
Tables A1, A2, and A3. The results will be discussed in order of
stratigraphic succession. The Molare Formation (Oligocene, ca.
33.7–23.8 Ma) is characterized mainly by 40Ar/39Ar ages clustering ~38–52 Ma with a strong 320 Ma signal and few ages ca. 99
Ma and 60–75 Ma (Fig. 6). We refer to Barbieri et al. (2003) for
further details on this formation.
The Rocchetta Formation (Lower Oligocene pro parte-Aquitanian; ca. 30–20.5 Ma) is characterized by a dominant age signal
of 40–65 Ma (Fig. 6), which is similar to the main age population
also found in the Molare Formation. Some ages ranging between
90 Ma and 150 Ma are present, while the Variscan signal is less
pronounced than in the Molare Formation. Step heating analy-
Detecting provenance variations and cooling patterns
77
ses on single grains were carried out on four samples from the
Rocchetta Formation (Fig. 7). A step heating experiment on
D61a produced a discordant age spectrum with a total fusion
age of 109.8 ± 1.1 Ma. This spectrum is represented by slightly
higher ages at lower temperatures, which might be the result of
alteration or excess 40Ar. However, in case of excess 40Ar, a much
more disturbed spectrum should be expected (e.g., McDougall
and Harrison, 1999). The “plateau-like” region of the spectrum
has a weighted mean age of 113.5 ± 7.4 (Fig. 7; Table A3). The
analysis on sample D61b gives a plateau age of 108.7 ± 1.0 Ma,
suggesting that this signal is undisturbed. The analysis of sample
D57 yields a slightly discordant total fusion age of 73.2 ± 3.1 Ma,
whereas a plateau age of 51.4 ± 1 Ma was obtained from sample
D72, showing that this signal is undisturbed.
The Monesiglio Formation (Upper Oligocene–Aquitanian;
ca. 28.5–20.5 Ma), laterally interfingering with the Rocchetta
Formation toward the east, is characterized mainly by ages ca.
50 Ma. The other ages range between 38 Ma and 150 Ma. Step
heating analysis on sample D69 produced a slightly discordant
age spectrum (e.g., alteration) with a total fusion age of 51.7 ±
0.5 Ma. The “plateau-like” region of the spectrum has a weighted
mean age of 51.6 ± 1.3 Ma (Fig. 7; Table A3).
The Cortemilia and Paroldo formations (latest Aquitanian–
Langhian; ca. 22–14.8 Ma) display a cluster of ages mainly ranging between 38 and 70 Ma, with a few ages between 100 and 180
Ma. A minor component shows ages in the range 250–300 Ma.
The Cassinasco and Murazzano formations (Langhian-Serravallian; ca. 16.4–11.2 Ma) are characterized by an important
contribution of ages ca. 70 Ma (Fig. 6), which is distinctive,
because it is older than the dominant age population (ca. 50 Ma)
detected in general in the previous formations. A minor signal
indicating Variscan provenance is present. These formations are
further characterized by an important group of ages between 90
and 150 Ma. Step heating analyses on single grains have been
carried out on three samples from the Cassinasco Formation.
Samples D40 and D50 give a plateau age of 106 ± 1 Ma and 78
± 1 Ma, respectively (Fig. 8). The third analysis, on sample D65,
produced a slightly discordant age spectrum (e.g., alteration) with
a total fusion age of 94.4 ± 0.7 Ma. The “plateau-like” region of
the spectrum has a weighted mean age of 94.4 ± 0.7 Ma (Fig. 8;
Table A3). The Lequio Formation (Serravallian-Tortonian; ca.
14.8–7.12 Ma) displays two major peaks in its detrital mica ages,
one at 50 Ma and the other at 70 Ma, and a strong reappearance
of Variscan ages.
Results from Present-Day River Sands
Figure 6. Probability distribution diagrams of 40Ar/39Ar (detrital) ages
for the samples (grouped in formations) investigated in this study.
N—number of experiments; gray bars—indicative depositional ages.
For further details, see Table A2.
Three samples (average of 20 grains for each sample) coming from the main rivers draining the present western Alpine Arc
(Tanaro, Maira, and Stura Rivers; Fig. 3) have been analyzed
using single fusion analyses. Step heating analyses have been
performed on a single grain from each river sample.
The headwaters of the Tanaro River are in the Ligurian
Alps. It drains Triassic and Permian formations belonging to the
78
B. Carrapa, J. Wijbrans, and G. Bertotti
Figure 8. Step heating analyses of selected samples from the Cassinasco Formation. For further details, see Tables A1 and A2.
Figure 7. Step heating analyses of selected samples from the Rocchetta
and Monesiglio formations. For further details, see Table A3.
Piemontese and Briançonnais domain and, further to the southwest, the Variscan Crystalline Massifs belonging to the Ligurian
Alps. The sample was collected at the entrance of the Tanaro
River into the Tertiary Piedmont Basin (Fig. 3A). White mica
ages range mainly between 270 and 306 Ma, with only one age
of 37 Ma (Fig. 9, Table A2). A step heating analysis performed
on sample B16 (Fig. 10) gives a plateau age of 314 ± 3 Ma, suggesting an homogeneous signal.
The Stura River drains mainly the Argentera Massif and
partly the Briançonnais domain. The main age population
detected falls between 204–302 Ma (Fig. 9). A step heating
analysis performed on sample B18 gives a plateau age of 306 ± 2
Ma (Fig. 10, Table A2), suggesting a Variscan signal undisturbed
by subsequent Alpine overprinting.
The Maira River drains the poly-metamorphic HP-UHP
units of the southwestern part of the Dora Maira Massif. Detrital
mica ages range between 39 Ma and 159 Ma (Fig. 9), with a
Detecting provenance variations and cooling patterns
79
Figure 9. Probability distribution diagrams of
samples coming from present-day river sands.
For further details, see Tables A1 and A2.
cluster of ages between 65 and 95 Ma. A step heating analysis
performed on sample B14 produced a slightly discordant spectrum with a total fusion age of 75.9 ± 0.6 Ma signal (Fig. 10). The
“plateau like” region of the spectrum has a weighted mean age of
76.3 ± 0.7 Ma (Fig. 10).
PROVENANCE DISCRIMINATION AND INFERENCES
FOR SOURCE AREA EVOLUTION
The wide range of ages in the Tertiary Piedmont Basin samples reflects the diverse provenance of the micas from different
tectonic units of the surrounding belt. Discrimination between
different source areas has been attempted using the main detrital
age populations for each formation or group of formations as
distinctive of different source area contribution.
Oligocene–Early (Middle) Miocene
Oligocene-Aquitanian
The Molare Formation is the first Tertiary Piedmont Basin
clastic infill that lies on the crystalline rocks of the Ligurian Alps,
mirroring directly the source area outcropping at time of deposition (Barbieri et al., 2003; Gnaccolini, 1974). Ages range mainly
ca. 40–45 Ma, which can be related to the Alpine metamorphic
rocks of the Voltri Group and Montenotte Nappe, and ca. 320
Ma, which can be linked to the contribution of detritus from the
Variscan Crystalline Massifs present in the Ligurian Alps (Barbieri et al., 2003).
Within the Rocchetta and Monesiglio formations, depositional facies change from transitional to marine with the hemipelagic sediments and high to low density turbidity bodies (e.g.,
Noceto, Mazzurrini, Piantivello; Gelati and Gnaccolini, 1998,
and references therein), marking a deepening of the basin. Therefore, more distal sources compared to the Molare Formation can
be expected. The presence of a common (ca. 45–50 Ma) age
population for the Rocchetta and Monesiglio formations could
have different interpretations: (1) a primary contribution from the
southern domain (e.g., Voltri Group), which reflects the signal of
the crystalline basement that was widely affected by the Eocene
Alpine metamorphism; (2) a contribution from western sectors,
which also record the same Eocene signal (ca. 45 Ma); (3) a mix
of these different sources; or (4) partial reworking of sediments
from the underlying formations.
The first hypothesis is less likely because in case of a primary southern source, a stronger Variscan signal might have been
expected.
Ages between 200 and 120 Ma are widely preserved in the
western Alpine domain (e.g., Hunziker et al., 1992; Cortiana et
al., 1998) but less so in the Ligurian Alps (Vance, 1999). Ages
ca. 200 Ma may represent the cooling following the Middle
80
B. Carrapa, J. Wijbrans, and G. Bertotti
in comparison to that feeding the Molare Formation. Therefore,
the Rocchetta and Monesiglio ages are interpreted to record the
first signal of the erosion of western Alpine sectors.
Latest Aquitanian–Langhian
Facies characteristics, petrographic data, and paleocurrent
directions in latest Aquitanian–Langhian sediments (Cortemila
and Paroldo formations) suggest a change in sedimentary patterns with provenance mainly from western sectors (Gelati et
al., 1993; Gnaccolini and Rossi, 1994). The detrital signal in the
Cortemilia and Paroldo formations spans a broad range of ages,
which is interpreted to indicate a wide source area (possibly
wider than the one feeding the Rocchetta and Monesiglio formations), including mainly western Alpine sectors. The lack of
Variscan ages discounts the southern sectors as a possible source
area. The main age population (40–50 Ma) could be interpreted
partially as a signal coming from the Western Alps, which could
potentially also record the Eocene signal or be the result of partial
reworking. Other ages, ranging between 50 and 150 Ma, suggest
a contribution from the western Alpine domains.
Middle–Late Miocene
Figure 10. Step heating analyses of selected samples from present river
sands. For further details, see Tables A1, A2, A3.
Triassic thermal anomaly, which influenced the Southern Alps
and the Lombardian Basin and which was possibly related to the
intrusion of a magmatic body in the lower crust (Bertotti et al.,
1997, and references therein). Ages ca. 85–100 and 65 Ma can
potentially be linked to early exhumed oceanic units (e.g., the
Sestri-Voltaggio Unit; no geochronological data are available in
this particular area).
The presence of different ages that can potentially be related
to different sources within the same formation (e.g., D57–59,
Noceto system: depositonal lobes as in Mutti and Normark,
1987), with paleocurrent directions coming from both southern
and western sectors (Fig. 3), suggests mixing of sources within
the same formation and possibly within the same sample.
The wider range of ages present in the Rocchetta and Monesiglio formations compared to the Molare Formation suggests a
wider source area (including both southern and western sectors)
This time span is characterized by a change in paleocurrent directions, sandstone composition, and sedimentary facies
(Gelati et al., 1993; Gnaccolini and Rossi, 1994). With the Cassinasco and Murazzano formations (Langhian-Serravallian), an
important shift in main detrital age population (from 40 to 50
Ma toward 70 Ma) occurs, with a significant cluster of ages at
ca. 90–150 Ma. The stronger proportion of 70 Ma ages, which
appears to be a dominant age cluster, older than the main age
population (ca. 50 Ma), revealed in older formations is not compatible with a simple scenario in which continuous exhumation
and erosion of a fixed source takes place (Fig. 5A). An evolution
of the paleodrainage system, including more western-northwestern sectors (e.g., Sesia Lanzo), may explain the stronger
contribution of the 70 Ma predominant signal. Also, in the currently exposed crystalline units of the Ligurian Alps, there is little
evidence for units that have experienced cooling following a ca.
70 Ma event, while evidence for an Eocene cooling after HP
metamorphism is widespread in the western Alpine domain (e.g.,
Cortiana et al., 1998; Hunziker et al., 1992; Ruffet et al., 1995;
Agard et al., 2002, and references therein). Therefore, the shift in
the main detrital age is interpreted as an evolution in sedimentary
pattern and provenance related to an enlargement of the Tertiary
Piedmont Basin source area toward more western-northwestern
Alpine domains. This enlargement in the main Tertiary Piedmont
Basin source area is probably associated with a reorganization of
the paleodrainage system. Reorganization of paleodrainage systems has also been recorded for this particular time in the Central
and Eastern Alps (Carrapa and Di Giulio, 2001; Spiegel et al.,
2001; Frisch et al., 1998), suggesting a regional rearrangement
in the erosional pattern of the Alpine chain, probably caused by a
period of increased tectonic activity.
Detecting provenance variations and cooling patterns
The Lequio Formation (Serravallian-Tortonian; 14.8–7.12
Ma) shows a main detrital population ca. 50–70 Ma, which can
still be attributed to a western Alpine domain with a strong reappearance of Variscan ages. The Variscan ages are interpreted in
this case as a signal coming from the Argentera Massif since
petrographic and paleocurrent data (Gnaccolini and Rossi, 1994)
do not give any support to the hypothesis of a southern source
(Variscan Crystalline Massifs in the Ligurian Alps). This conclusion is well supported by a Late Miocene cooling and exhumation event recorded in the Argentera Massif (Bigot-Cormier et
al., 2000).
Present
The main detrital 40Ar/39Ar age population in the Tanaro
River clearly mirrors cooling ages of the Variscan Crystalline
Massifs. Ages ranging between 204 and 302 Ma in the Stura
River are representative of the Variscan metamorphic event
recorded at present in the Argentera Massif. Our data agree with
the conclusion reached by Monié and Maluski (1983) that the
Alpine peak temperature in the Argentera Massif was <220–250
°C and consequently did not overprint the Variscan signal in
white micas. The signal coming from the Tanaro and the Stura
Rivers (mainly Variscan ages) could be evidence of either a
geochronologically homogeneous source or of a low degree of
mixing of the present drainage system.
The wide range of ages in the Maira River record the heterogeneity of sources mainly characterized by middle-late Cretaceous ages and possibly also a good degree of mixing of different
geochronological domains. Rocks outcropping in the present
Maira drainage system provide a signal very similar to the one
produced by present-day river sands (Figs. 4 and 9).
By combining the age data coming from the three rivers
(Fig. 9), we obtain a picture that is remarkably similar to the one
observed for the Upper Miocene sediments (Lequio Formation;
Fig. 6). This suggests that no major paleodrainage reorganizations occurred at least since the Late Miocene in the western
Alpine catchment area.
WESTERN ALPINE COOLING EXHUMATION
PATTERNS
In theory, a continuous pattern of exhumation of a fixed
source area, represented by crustal rocks, is recorded by moving
peaks up sequence (younging of the main signal) in the sedimentary infill (Brandon and Vance, 1992). Continuous exhumation
through time would create a constant resetting of ages due to
a steady upward movement of crustal material through the isotherms. Looking at the main detrital age populations of the Tertiary Piedmont Basin sediments (Fig. 6), a lack of moving peaks
up sequence is apparent; this is mainly the result of the evolution
of the paleodrainage system through time. The same ca. 45–50
Ma signal recorded as the main detrital population in Oligocene
to Aquitanian sediments is very similar to outcropping ages in the
81
southern domain at present (Fig. 4). The same is true for 70–120
Ma ages recorded as a strong signal in Langhian-Serravallain
sediments and in the present-day sands, which is very similar to
40
Ar/39Ar data on present outcropping rocks of the western Alpine
domain (e.g., Cortiana et al., 1998; Ruffet et al., 1997; Scaillet et
al., 1992; Stöckhert et al., 1986; Agard et al., 2002; Fig. 4). These
lines of evidence are not supported by a continuous exhumation
and erosion pattern of a fixed source. This shows that a consistent
amount of crustal rocks with indistinguishable 40Ar/39Ar ages has
been eroded for a substantial amount of time, suggesting that the
Western Alps have been regulated by episodes of fast cooling
and exhumation (see also Carrapa et al., 2003). During these episodes, enough crustal material with indistinguishable 40Ar/39Ar
isotopic ages was formed and then was eroded over long periods
of time and at present still sheds the same signals.
Also, Cretaceous ages (i.e., 120 Ma, 70 Ma) in Miocene
and Present sediments derived from different western Alpine
rocks could be the result of real geological events or the effect
of excess 40Ar (Arnaud and Kelley, 1995; Ruffet et al., 1995;
Ruffet et al., 1997). Ages ca. 120 Ma have been originally
interpreted as the result of cooling following the peak of high
pressure metamorphism (Monié and Chopin, 1991; Oberhänsli
et al., 1985). Some authors have dismissed a Cretaceous thermal
event for the internal Western Alps and consequently interpret
this cluster of ages as due to excess 40Ar (e.g., Arnaud and Kelley,
1995; Kelley et al., 1994). Monié and Chopin (1991) have shown
that 40Ar/39Ar ages ca. 100–110 Ma in the Dora Maira Massif
are representative of a real signal. One of their major arguments
was that it was highly unlikely that high pressure phengites from
different internal units of the Western Alps (Monte Rosa, Sesia
Lanzo, and Dora Maira) could have incorporated equivalent
amounts of excess 40Ar leading to the same result. If the signal
is geologically meaningful, then these ages could potentially be
linked with a mid-Cretaceous metamorphic event (e.g., Cortiana
et al., 1998; Monié and Chopin, 1991). Scaillet et al. (1992) show
that high Mg-phengites from UHP rocks of the Dora Maira often
yield Cretaceous ages, while Fe-phengites yield ages ca. 35–40
Ma. It is thus sometimes unnecessary to involve the presence of
excess 40Ar to explain Cretaceous ages. Also, it is very unlikely
that different rocks all experienced the same amount of excess
40
Ar leading to the same ages. Furthermore, because of the
widespread occurrence of the same cluster of ages recorded by
different thermochronometers in the Western Alps (Cortiana et
al., 1998; Inger et al., 1996; Vance, 1999) and Central Alps (e.g.,
Hunziker et al., 1992), we consider the 120–70 Ma signal to be
representative of important geological Eoalpine events(see also
Carrapa and Wijbrans, 2003).
CONCLUSIONS
The general trend in the Tertiary Piedmont Basin sediments
is that the main isotopic age population found in the oldest
sediments (ca. 45–50 Ma) gets older toward younger sediments
(ca. 70 Ma). This trend is interpreted as the result of a gradual
82
B. Carrapa, J. Wijbrans, and G. Bertotti
Figure 11. Schematic paleoreconstruction of the study area from Oligocene until post Tortonian times. + indicates uplifting area;– indicates subsiding area. Data from this work have been combined with literature data on paleogeography and paleocurrents (Gnaccolini, 1970; Lorenz, 1979;
Gelati and Gnaccolini 1982; Fannucci, 1986; Dondi and D’Andrea, 1986; Gnaccolini and Rossi, 1994; Clari et al., 1995; Foeken et al., 2003).
Detecting provenance variations and cooling patterns
enlargement of the catchment area to include tectonic units with
progressively older isotopic ages (Fig. 11).
Detrital micas from Oligocene until approximately Aquitanian time sediments in the Tertiary Piedmont Basin show a
source area localized in the southern sectors (Ligurian Alps and
Voltri Group), which was affected by a major Alpine metamorphic overprint at ca. 40–50 Ma. Since about Aquitanian-Burdigalian time, ages ca. 120–200 Ma and 70 Ma are widely recorded
from detrital micas. This indicates a wider and mixed source area
with contributions from both the Ligurian Alps and the western
Alpine domain.
Since the Langhian, the main detrital population shifts from
50 Ma toward 70 Ma, indicating an enlargement of the source
area from southern sectors toward more western-northwestern
sectors, which are characterized mainly by Eoalpine signals.
This reorganization of the Tertiary Piedmont Basin source is
likely linked to an evolution of the paleodrainage system most
likely related to vertical tectonic movements in the hinterland.
This evidence allows us to conclude that from the Early Miocene
on, the Tertiary Piedmont Basin starts to record the erosion of
83
the exhumed western Alpine Arc. From Serravallian time, there
is evidence of detritus coming from the Argentera Massif, characterized by a Variscan signal. The very similar signal shown by
present-day river sands and Upper Miocene sediments suggests
that the paleodrainage system did not continue to evolve after
Miocene time in this sector of the Alps. Also, our data suggest
that regional rapid and episodic Cretaceous and Middle Eocene
cooling events in the Western Alps were followed by periods of
relatively slow erosion, and later Mesoalpine-Neoalpine metamorphic events did not overprint the main original signals.
ACKNOWLEDGMENTS
This study was supported by the Netherlands Foundation
of Scientific Research (NWO). Special thanks to Yani Najman,
an anonymous reviewer, and Glen Murrell for their constructive advice in the preparation of the manuscript. This is NSG
(Netherlands School for Sedimentary Geology) publication
number 2003.05.15.
CODE
D
D
D
D
B
B
B
B
B
B
B
B
B
D
D
D
D
D
D
D
D
D
D
D
D
D
D
B
B
B
D
B
D
D
D
D
D
B
B
No. Field No.
Formation
Step H Total F
Lab code
42
24-3
Molare
X 99M0183+99j0119
60
4,4
Molare
X 99M0140+99M0143
67
4,4
Molare
X
99M0287
80
54-4
Molare
X 99M0144
1
2,2
Molare
X 00M0061
21
64-2
Molare
X 00M0070
33
108-9
Molare
X 00M0085
42
72
Molare
X 00M0258+01M0258L
45
83
Molare
X 00M0276
47
90
top Molare
X 01M0029
40
77
Molare
X 00m0257
52
86
Molare
X 00M0277+01M0277
36
70-1
Molare
X 00M0088
45
16-16
Rocchetta
X 99m0148
46
25-4
Rocchetta
X 99m0149+99m0186
52
21-21
Rocchetta
X 99m0197+0199
57
18-18
Rocchetta
X
99m0403
59
18-18
Rocchetta
X 99m0185
61
27-6
top Rocchetta Fm.–base Monesiglio Fm.
2X
99m0301, 99m0300
62
27-6
Rocchetta
X 99m0155
66
12,12
Rocchetta
X 99m0159
71
15-15
Rocchetta
X 99m0167
72
10,10
Rocchetta
X
99m0299
74
10,10
Rocchetta
X 99m0168
77
57-7
Cassinelle Sst.
X 99m0175
69
20-20
Monesiglio
X
99m0370
70
20-20
Monesiglio
X 99m0192+190
7
29-8
Top Monesiglio
X 00m0064
10
34-13
Monesiglio
X 00m0076
23
76-7
Monesiglio
X 00m0079
76
30-9
top Paroldo Marls
X 99m0193+195
20
63-1
Paroldo Marls
X 00m0078
43
37-2
base Cortemilia
X 99m0241
47
38-3
Top Cortemilia
X 99m0212
56
61-11
Cortemilia
X 99m0246
81
19-19
Cortemilia
X 99m0247
48
31-10
base Murazzano
X 99m0255
9
32-11
Murazzano Fm. (Cassinasco)
X 00m0074
29
87-18
Murazzano
X 00m0082
GPS
Depositional time
(UTM, 32T, EU 1950)
Chattian? (Gelati et al., 1993)
423639–491334
Rupelian (section 12, Mutti et al., 1995)
453834–492276
Rupelian (section 12, Mutti et al., 1995)
453834–492276
Rupelian (Gelati et al., 1993)
465800–493815
Rupelian (section 12, Mutti et al., 1995)
453834–492276
Rupelian (Gelati et al., 1993)
461620–492711
Rupelian (Gelati et al., 1993)
477478–494043
Rupelian (Gelati et al., 1993)
448500–491220
Rupelian (Gelati et al., 1993)
455600–492890
Rupelian (Gelati et al., 1993)
445850–493190
Rupelian (Gelati et al., 1993)
442125–491480
Rupelian (Gelati et al., 1993)
446500–493195
Chattian (N2, Gelati et al., 1996)
414965–491319
Lower Oligocene–Aquitanian
445238–493171
Aquitanian (section Ceva, Gelati 1968)
424250–491619
Aquitanian (Mazzurrini body, Gelati and Gnaccolini, 1998)
443750–493646
Chattian (Noceto system, Cazzola and Fornaciari, 1990)
44507–4932356
Chattian (Noceto system, Cazzola and Fornaciari, 1990)
44507–4932356
Aquitanian (Gelati, 1968)
424250–491619
Aquitanian (Gelati, 1968)
424250–491619
Aquitanian (top Mioglia system, Cazzola and Rigazio, 1982)
452159–492792
Lower Oligocene–Aquitanian (Gelati, 1968)
445540–423183
Chattian-Aquitanina (Mioglia system, Cazzola and Rigazio, 1982)
452502–492717
Chattian-Aquitanina (Mioglia system, Mutti et al., 1995)
452502–492717
Rupelian (d’Atri et al., 1997)
465454–493862
Burdigalian (Piantivello body, Gelati and Gnaccolini, 1998)
443360–493583
Burdigalian (Piantivello body, Gelati and Gnaccolini, 1998)
443360–493583
Burdigalian-Langhian (Gelati, 1968)
424170–491830
Aquitanian? (Gelati, 1968)
433929–492018
Chattian (N2, Gelati et al., 1996)
414788–491567
Langhian (Gelati, 1968)
425280–491956
Burdigalian-Langhian (Gelati, 1968)
426400–492110
Aquitanian (Gelati, 1968)
436475–493307
Langhian (Gelati, 1968)
434343–493702
Aquitanian (Gelati, 1968)
458183–494519
Burdigalian (Gelati, 1968)
442307–493503
Langhian (Gelati, 1968)
426250–492180
Langhian-Serravallian (Gelati, 1968)
421529–492661
Serravallian (Gelati, 1968)
427842–493809
(continued)
TABLE A1. DETAILED INFORMATION OF THE STUDY SAMPLES
84
B. Carrapa, J. Wijbrans, and G. Bertotti
Formation
40
D
46-11
Cassinasco
41
D
46-11
Cassinasco
49
D
45-10
Cassinasco
50
D
47-12
base Cassinasco
51
D
47-12
Cassinasco
54
D
39-4
Cassinasco
55
D
39-4
Cassinasco
64
D
62-12
Cassinasco
65
D
62-12
Cassinasco
B
11
42-7
Top Cassinasco
B
24
81-12
top Cassinasco-Murazzano base
B
27
84-15
Cassinasco
B
34
121-7
Serravalle Sandstone (Cassinasco)
B
26
82-13
Lequio
B
30
89-20
Lequio
A
2
80-11
Lequio
A
4
83-14
Lequio
A
6 Mondovi'
Lequio
A
5
88-19
Lequio
Ps
B
13
Maira
–
A
34
Maira
–
B
14
Maira
–
B
15 Tanaro
–
A
31 Tanaro
–
B
16 Tanaro
–
B
17
Stura
–
A
33
Stura
–
B
18
Stura
–
Note: Ps—present-day sands.
CODE No. Field No.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Step H Total F
00M0067
01M0387
00M0089
00M0068
01M0388
01M0044
00M0069
01M0423
01M0039
99m0371
99m0200+202
99m0122+184
99m0373
99m0203+0208
99m0402
99m0210+209
99m0211
99m0404
00m0073
00m0072
00m0081
00m0087
00m0080
00m0083
01M0383
01M0415
01M0368
01M0416
LAB CODE
Present
Present
Present
Present
Present
Present
Present
Present
Present
Serravallian (section type of Gelati 1968)
Serravallian (section type of Gelati 1968)
Serravallian (section type of Gelati 1968)
upper Langhian–lower Serravallian (Gelati, 1968)
Langhian-Serravallian (Gelati, 1968)
Langhian-Serravallian (Gelati, 1968)
Langhian-Serravallian (Gelati, 1968)
Langhian-Serravallian (Gelati, 1968)
Langhian-Serravallian (Gelati, 1968)
Serravallian (Gelati, 1968)
Serravallian (Gelati, 1968)
Serravallian (Gelati, 1968)
Langhian-Serravallian (Gelati, 1968)
Serravallian (Gelati, 1968)
Tortonian (Gelati, 1968)
Serravallian-Tortonian (Gelati, 1968)
Serravallian-Tortonian (Gelati, 1968)
Serravallian-Tortonian (Gelati, 1968)
Serravallian-Tortonian (Gelati, 1968)
Depositional time
TABLE A1. DETAILED INFORMATION OF THE STUDY SAMPLES (continued)
Dronero
Dronero
Dronero
Ceva
Ceva
Ceva
Borgo S. Dalmazzo
Borgo S. Dalmazzo
Borgo S. Dalmazzo
44403–4948162
44403–4948162
443982–494878
423854–490674
423854–490674
431926–493473
431926–493473
462191–494965
462191–494965
430993–494386
419966–492936
429263–493713
451790–495200
418495–493108
422410–493902
419141–4930859
427669–493806
408000–491670
424127–493865
GPS
(UTM, 32T, EU 1950)
Detecting provenance variations and cooling patterns
85
86
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Molare
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
108-9 (B33)
1
2
3
4
5
6
7
8
9
10
J = 0.002408
0.00077
0.00000
0.00239
0.00000
0.00191
0.00058
0.00223
0.00041
0.00026
0.00000
0.00147
0.00029
0.00120
0.00132
0.00074
0.00005
0.00110
0.00062
0.00064
0.00054
0.00045
0.00138
0.00265
0.00243
0.00122
0.00050
0.00115
0.00097
0.00058
0.00094
0.14813
0.25215
0.48403
0.41191
0.03388
0.23183
0.40356
0.21554
0.18020
0.25440
3.48675
3.13148
4.84879
6.69340
0.43804
5.44954
3.70387
2.23130
2.73370
2.46275
99.47 ± 0.95
53.16 ± 0.50
43.00 ± 0.28
69.25 ± 0.35
55.32 ± 2.35
99.33 ± 0.54
39.44 ± 0.65
44.42 ± 0.48
64.73 ± 0.47
41.57 ± 0.33
93.89
81.58
89.55
91.04
85.10
92.61
91.23
91.10
89.35
92.82
54-4 (D80)
1
2
3
4
5
6
7
8
9
10
J=0.001572
0.00097
0.00367
0.00225
0.00214
0.00328
0.00492
0.00078
0.00592
0.00520
0.00000
0.00234
0.00000
0.00223
0.00000
0.00212
0.00078
0.00100
0.00197
0.00035
0.00000
0.00005
0.00023
0.00002
0.00015
0.00000
0.00000
0.00005
0.00000
0.00014
0.00002
0.10752
0.15023
0.21857
0.23252
0.23364
0.15658
0.24038
0.15601
0.22418
0.22746
2.00720
2.86248
5.15828
4.56705
11.25886
2.59343
4.42829
2.78566
3.86636
4.22014
52.18 ±1.28
53.24 ± 1.01
65.72 ± 0.86
54.86 ± 0.64
131.74 ± 1.16
46.37 ± 1.02
51.50 ± 0.58
49.94 ± 1.15
48.26 ± 0.75
51.87 ± 0.64
87.51
81.17
84.19
95.18
88.00
78.95
87.05
81.61
92.88
97.64
83 (B45)
1
2
3
4
5
6
7
J=0.002731
0.00019
0.00000
0.00056
0.00000
0.00183
0.00000
0.00027
0.00170
0.00044
0.00000
0.00076
0.00000
0.00018
0.00071
0.00032
0.00024
0.00024
0.00022
0.00028
0.00025
0.00033
0.19168
0.21093
0.18591
0.10137
0.10768
0.11037
0.08081
1.61768
2.49216
1.53250
0.82470
1.10118
1.73547
0.65787
41.11 ±1.01
57.29 ±0.77
40.16 ±0.90
39.64 ±1.56
49.69 ±0.64
75.85 ±1.17
39.67 ±1.28
96.65
93.79
73.93
91.09
89.47
88.59
92.49
64-2 (B21)
1
2
3
4
5
6
7
8
9
10
J=0.002799
0.00022
0.00009
0.00036
0.00000
0.00106
0.00010
0.00093
0.00014
0.00024
0.00026
0.00058
0.00240
0.00132
0.00020
0.00106
0.00000
0.00109
0.00034
0.00128
0.00159
0.00029
0.00009
0.00059
0.00084
0.00025
0.00012
0.00081
0.00073
0.00068
0.00155
0.15834
0.18868
0.28414
0.33570
0.13796
0.13227
0.26750
0.33650
0.16936
0.42424
1.17533
1.38712
3.38003
3.24415
1.02817
0.92269
3.86682
3.18388
3.15318
4.16294
37.10 ±0.84
36.75 ±0.65
59.09 ±0.63
48.15 ±0.35
37.25 ±0.86
34.89 ±0.91
71.56 ±0.80
47.16 ±0.45
91.65 ±1.08
48.88 ±0.42
94.80
92.82
91.50
92.17
93.50
84.41
90.81
91.00
90.73
91.65
90 (B47)
2
3
5
6
7
9
10
J=0.002678
0.04557
0.00169
0.00000
0.00271
0.00000
0.00057
0.00000
0.00066
0.00000
0.0011
0.00000
0.00016
0.19015
0.00051
0.00008
0.00000
0.00000
0.00000
0.00000
0.00030
0.00017
0.19861
0.24007
0.16808
0.23407
0.18693
0.11479
0.17385
1.84413
2.06499
1.32738
1.66177
1.46708
1.25148
1.32305
44.31 ±1.65
41.08 ±1.21
37.75 ±1.30
33.98 ±2.25
37.52 ±3.06
51.92 ±3.65
36.40 ±1.99
78.68
72.05
88.73
89.56
81.88
96.26
89.75
(continued)
Detecting provenance variations and cooling patterns
40
Molare
87
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
2-2 (B1)
1
2
3
4
5
6
7
8
9
J=0.003215
0.00066
0.00000
0.00023
0.00010
0.00067
0.00103
0.00466
0.00018
0.00038
0.00048
0.00236
0.00380
0.00201
0.00031
0.00046
0.00080
0.00292
0.00045
0.00000
0.00004
0.00033
0.00032
0.00033
0.00021
0.00005
0.00023
0.00012
0.16856
0.13507
0.65053
0.30100
0.21619
0.46942
0.69248
0.30685
0.42481
1.20014
1.02065
4.82774
3.56421
1.74999
3.53200
5.18755
2.25728
4.63050
40.83 ±0.68
43.30 ±0.72
42.54 ±0.26
67.40 ±0.61
46.35 ±0.64
43.12 ±0.32
42.94 ±0.34
42.17 ±0.39
62.14 ±0.42
85.99
93.84
96.03
72.12
93.90
83.50
89.72
94.32
84.27
4-4 (D60)
1
2
3
4
5
6
7
8
9
J=0.001706
0.03911
0.00386
0.00473
0.00068
0.00324
0.00182
0.00225
0.00307
0.00313
0.00016
0.00111
0.00209
0.00226
0.00267
0.00195
0.00048
0.00057
0.02252
0.00012
0.00011
0.00000
0.00000
0.00015
0.00000
0.00000
0.00000
0.00000
0.31927
0.15344
0.15559
0.12354
0.28898
0.11441
0.23445
0.31822
0.01891
6.47035
2.93695
2.51505
2.36214
4.86800
2.04062
4.14526
4.62225
0.36736
61.32 ± 4.39
57.97 ± 8.96
49.08 ± 8.86
57.91 ± 11.11
51.11 ± 0.96
54.08 ± 1.65
53.61 ± 0.92
44.16 ± 0.41
58.81 ± 6.43
54.75 ±1.2
35.89
67.73
72.41
78.00
84.03
86.17
86.13
88.92
68.61
D67
J=0.001653
TFA
86 (B52)
1
2
3
4
5
6
J=0.002556
0.00660
0.00757
0.00519
0.00344
0.00118
0.12389
0.00043
0.27901
0.00375
0.17358
0.00342
0.12384
0.00039
0.00028
0.00027
0.00000
0.00000
0.00058
0.09250
0.25660
0.19427
0.04523
0.19450
0.21019
1.05371
2.55979
1.97718
0.30707
1.34596
2.59312
51.78 ± 2.47
45.42 ± 0.61
46.33 ± 1.66
31.04 ± 9.67
31.63 ± 1.66
56.01 ± 2.75
35.08
62.55
84.99
70.91
54.82
71.97
77 (B40)
1
2
3
4
5
6
7
8
9
J=0.002856
0.00019
0.00000
0.00013
0.00000
0.00025
0.00588
0.00064
0.00171
0.00026
0.00000
0.00053
0.00000
0.00007
0.00017
0.00006
0.00507
0.00012
0.00173
0.00017
0.00053
0.00050
0.00012
0.00037
0.00017
0.00000
0.00051
0.00047
0.09104
0.15551
0.09195
0.20654
0.17751
0.10201
0.05935
0.06963
0.07406
6.02044
10.36692
6.02778
13.36365
11.84916
0.76271
3.91726
4.52877
4.83537
312.10 ±1.77
314.42 ±1.21
309.60 ±2.1
305.90 ±0.89
314.81 ±1.31
38.12 ±0.97
311.56 ±2.4
307.39 ±2.34
308.47 ±2.11
99.08
99.62
98.77
98.61
99.34
82.94
99.49
99.62
99.28
J=0.002803
0.00159
0.00230
0.00070
0.00000
0.00026
0.00046
0.00025
0.00176
0.00030
0.00038
0.00000
0.00000
0.00028
0.00432
0.00087
0.02498
0.00055
0.02422
0.00075
3.22164
0.00017
0.00017
0.00002
0.00072
0.00061
0.00090
0.00099
0.00067
0.00061
0.00057
0.22628
0.22385
0.12872
0.38301
0.14013
0.19676
0.16624
0.11757
0.13672
0.36739
3.19200
4.58688
1.09381
14.20966
9.24694
13.32092
11.06876
1.66105
8.99463
22.35749
69.96 ±0.55
100.75 ±0.67
42.47 ±0.72
178.48 ±0.66
306.18 ±1.59
313.48 ±1.06
308.72 ±2.81
70.07 ±5.34
305.33 ±2.06
291.34 ±2.6
87.16
95.68
93.51
99.49
99.06
100.00
99.27
86.61
98.24
99.02
(continued)
72 (B42)
1
2
3
4
5
6
7
8
9
10
88
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Molare
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
24-3 (D42)
1
2
3
4
5
6
7
8
9
10
J=0.001869
0.00723
0.00109
0.00348
0.00010
0.00648
0.00126
0.00949
0.00410
0.00532
0.00584
0.00981
0.00885
0.00155
0.00513
0.00164
0.00555
0.00121
0.00423
0.00063
0.00839
0.00024
0.00000
0.00015
0.00000
0.00010
0.00000
0.00000
0.00000
0.00000
0.00000
0.18314
0.13772
0.15039
0.09100
0.39962
0.24440
0.15737
0.10112
0.14297
0.15980
18.53496
14.04012
13.89986
8.00232
42.29852
25.28861
16.38853
10.78740
14.92964
18.14587
312.55 ± 1.98
314.64 ± 2.64
287.47 ± 2.51
274.51 ± 3.77
325.66 ± 1.68
318.96 ± 1.97
320.85 ± 1.77
328.01 ± 3.13
321.64 ± 1.81
347.22 ± 1.96
89.66
93.18
87.88
74.04
96.41
89.71
97.28
95.69
97.66
98.98
B36
J=0.002252
0.00021
0.00000
0.00038
0.00000
0.00013
0.00058
0.00098
0.00166
0.00088
0.00000
0.00023
0.00000
0.00029
0.00059
0.00016
0.00005
0.00039
0.00000
0.00036
0.00059
0.00015
0.00030
0.00048
0.00124
0.00040
0.00015
0.00080
0.00050
0.00031
0.00043
0.02526
0.10552
0.00787
0.21061
0.08001
0.11442
0.18568
0.10812
0.09101
0.07294
0.33070
0.96437
0.07161
1.96925
1.00862
1.45800
2.18513
0.97381
1.75191
1.47083
52.42 ±2.81
36.75 ± 0.67
36.58 ± 5.66
37.59 ± 0.52
50.50 ± 1.07
51.04 ± 0.88
47.19 ± 0.51
36.22 ± 0.76
76.56 ± 0.85
80.12 ± 1.27
84.34
89.57
65.86
87.16
79.52
95.47
96.22
95.42
93.83
93.29
38
39
40
0.00001
0.00000
0.00000
0.00000
0.00001
0.00000
0.00000
0.00000
0.03401
0.04303
0.03165
0.09001
0.05566
0.06210
0.07031
0.06639
0.57140
0.53491
0.55752
4.24593
1.06195
1.54303
2.55568
3.09772
55.04 ± 7.78
40.89 ± 5.61
57.67 ± 7.18
150.48 ± 2.51
62.38 ± 2.77
80.83 ± 3.77
117.04 ± 1.29
148.91 ± 1.45
52.58
93.78
96.11
90.73
84.76
96.00
96.97
95.97
0.00024
0.00010
0.00009
0.00000
0.00000
0.00000
0.00044
0.00001
0.00001
0.00000
0.00000
0.00000
0.00020
0.00011
0.00004
0.34355
0.33466
0.29135
0.22677
0.28963
0.35071
0.46206
0.12361
0.10619
0.12168
0.17724
0.17801
0.38913
0.17202
0.16952
36.86724
6.80874
8.10839
7.29025
4.09609
23.15138
3.18960
2.39191
1.74434
3.68076
2.03207
3.00839
2.69283
2.11834
4.31976
324.44 ± 1.38
66.16 ± 0.48
89.90 ± 0.46
103.46 ± 0.73
46.25 ± 0.64
206.38 ± 1.18
22.72 ± 0.41
62.98 ± 1.38
53.60 ± 1.21
97.51 ± 1.61
37.58 ± 1.14
55.13 ±1.23
22.78 ±0.55
40.33 ±1.14
82.49 ±1.37
99.43
95.44
94.92
96.41
96.19
97.75
93.74
91.70
86.52
92.08
93.20
96.14
95.69
96.85
97.32
(continued)
1
2
3
4
5
6
7
8
9
10
Rocchetta
D45
D46
Bc
De
Gh
Il
No
36
Ar(a)
37
Ar(Ca)
J=0.001844
0.00174
0.00048
0.00012
0.00000
0.00008
0.00000
0.00147
0.00240
0.00065
0.00269
0.00022
0.00929
0.00027
0.00000
0.00044
0.01662
J=0.001836
0.00072
0.00000
0.00110
0.00000
0.00147
0.00000
0.00092
0.00000
0.00055
0.00000
0.00180
0.00178
0.00072
0.00061
0.00073
0.00036
0.00092
0.00000
0.00107
0.00000
0.00065
0.00663
0.00057
0.00220
0.00059
0.00000
0.00041
0.00000
0.00046
0.00067
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
40
Ar(%)
Detecting provenance variations and cooling patterns
40
Rocchetta
D52
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
197ab
197de
197gh
199bc
199ef
199gh
199im
199no
199pq
J=0.001774
0.00317
0.00843
0.00077
0.00863
0.00038
0.00149
0.00040
0.00000
0.00069
0.00000
0.00027
0.00000
0.00025
0.00000
0.00047
0.00062
0.00090
0.00093
D57
J=0.00173
D59
df
gh
mn
op
qr
tu
vz
J=0.00173
0.00059
0.00000
0.00046
0.00000
0.00115
0.00098
0.00081
0.00000
0.00036
0.00000
0.00010
0.00100
0.00083
0.00222
0.00090
0.00201
0.00038
0.00126
0.00066
0.00555
D61
0.00021
0.00004
0.00000
0.00000
0.00014
0.00000
0.00009
0.00009
0.00007
0.00005
0.00013
0.00005
0.00022
0.00022
0.00005
0.00002
0.00000
0.00008
0.00000
0.12764
0.11714
0.09796
0.12249
0.10031
0.13293
0.10214
0.05797
0.15660
0.25186
0.12956
0.40920
0.19057
0.19985
0.21173
0.37011
0.19990
0.09074
0.27831
D66
2.76609
6.00016
2.13885
2.65719
1.15294
1.84397
1.87681
0.88098
6.64318
68.06 ±1.86
156.91 ±2.05
68.56 ±1.89
68.13 ±1.54
36.42 ±1.74
43.86 ±1.14
57.87 ±1.50
47.99 ±3.45
130.9 ±1.64
TFA
72.69 ±0.67
4.42508
5.13876
12.05328
5.85617
2.97448
2.95362
8.72166
8.54947
2.90255
6.46287
53.65 ± 0.50
118.93 ± 0.98
89.06 ± 0.41
92.81 ± 1.51
45.55 ± 0.65
42.73 ± 1.02
71.6 ± 0.65
127.91 ± 1.08
96.51 ± 2.17
70.58 ± 0.83
TFA
TFA
109.77 ± 1.06
108.61 ± 0.85
40
Ar(%)
87.13
96.35
97.00
97.06
96.63
99.94
95.92
97.71
96.26
96.17
97.40
97.26
96.58
97.34
98.73
97.60
97.52
96.66
97.70
J=0.001698
a
b
D62
89
J=0.001690
0.00074
0.00393
0.00295
0.00652
0.00248
0.00000
0.00048
0.00384
0.00073
0.00000
0.00166
0.00353
0.00100
0.00000
0.00028
0.00277
0.00036
0.00287
0.00007
0.00013
0.00022
0.00004
0.00011
0.00004
0.00003
0.00009
0.00012
0.12016
0.11592
0.21685
0.02310
0.16504
0.31000
0.19379
0.10747
0.02341
2.33856
4.93581
8.21452
0.36439
2.95852
13.82803
5.72020
12.69059
0.51106
58.38 ± 2.11
125.36 ± 2.58
111.95 ± 1.37
47.46 ± 10.41
53.84 ± 0.75
131.12 ± 0.82
87.82 ± 0.66
328.26 ± 2.15
65.36 ± 4.68
91.44
85.00
91.81
71.85
93.17
96.58
95.06
99.34
82.78
J=0.00166
0.00071
0.00083
0.00035
0.00017
0.00046
0.00082
0.00033
0.00024
0.00029
0.00000
0.00000
0.00000
0.00010
0.00075
0.00011
0.00000
0.00117
0.00076
0.00030
0.00000
0.00000
0.00015
0.00000
0.00010
0.00011
0.00000
0.00012
0.00009
0.00002
0.00017
0.04506
0.06933
0.02808
0.03940
0.08697
0.00340
0.02182
0.03744
0.05237
0.03879
0.73080
8.31216
0.46379
2.44456
2.65349
0.17823
1.02951
0.71227
0.89784
2.16027
47.93 ± 3.26
327.47 ± 3.57
48.79 ± 3.87
176.85 ± 2.88
89.13 ± 1.52
150.46 ± 11.48
136.04 ± 5.52
56.09 ± 2.34
50.62 ± 2.10
159.53 ± 3.68
77.63
98.78
77.33
96.13
96.86
100.00
97.21
95.69
72.14
96.00
(continued)
90
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Rocchetta
D71
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
J=0.001628
0.00488
0.00000
0.00349
0.00000
0.01692
0.00194
0.00123
0.00000
0.00333
0.00268
0.00126
0.00000
0.02720
0.30870
0.00219
0.00000
0.00411
0.00000
0.00174
0.00000
0.00000
0.00000
0.00014
0.00000
0.00005
0.00000
0.00000
0.00006
0.00007
0.00000
0.42917
0.33527
0.38987
0.27295
0.31863
0.42892
1.51318
0.17906
0.37903
0.18811
Ar(%)
7.81591
5.70112
7.75765
3.83528
4.74650
5.52668
23.55381
2.94696
6.10989
2.84659
52.71 ± 0.46
49.26 ± 0.69
57.52 ± 1.12
40.80 ± 0.84
43.23 ± 0.61
37.45 ± 1.10
45.15 ± 1.00
47.70 ± 2.89
46.73 ± 1.34
43.91 ± 2.68
84.41
84.66
60.80
91.34
82.83
93.70
74.55
82.00
83.43
84.72
TFA
51.48 ± 1.04
TFA
55.16 ± 2.48
51.42 ± 1.57
52.85 ± 1.77
50.74 ± 2.90
165.54 ± 7.35
52.61 ± 1.10
73.77 ± 1.37
43.26 ± 1.45
65.87 ± 1.17
88.72
91.02
89.51
93.64
93.86
87.25
92.43
82.01
89.44
D72
J=0.001622
D74
J=0.001609
0.00167
0.00000
0.00178
0.00253
0.00201
0.00199
0.00065
0.00000
0.00206
0.00000
0.00107
0.00157
0.00106
0.00000
0.00117
0.00361
0.00108
0.00389
0.00000
0.00000
0.00000
0.00000
0.00000
0.00015
0.00000
0.00034
0.00000
0.20076
0.29605
0.27424
0.16019
0.15599
0.11745
0.14775
0.10436
0.11736
3.87398
5.31949
5.06714
2.84000
9.31634
2.16014
3.83256
1.57415
2.71234
J=0.001591
0.00643
0.00000
0.00116
0.00000
0.00159
0.00080
0.00295
0.00000
0.00021
0.00000
0.00023
0.00374
0.00110
0.00312
0.00186
0.00349
0 00045
0 00000
0.00000
0.00000
0.00012
0.00025
0.00006
0.00011
0.00008
0.00008
0 00007
0.45155
0.02252
0.21398
0.15895
0.00671
0.00783
0.12994
0.12017
0 16599
7.61627
0.26661
3.70928
3.29189
0.06570
0.11160
3.08067
2.38736
2 19846
D77
40
47.77 ± 0.39
33.66 ± 5.74
49.08 ± 0.51
58.49 ± 1.10
27.87 ± 18.64
40.47 ± 10.17
66.80 ± 0.95
56.14 ± 1.30
37 62 0 69
80.03
43.85
88.74
79.05
51.40
61.79
90.48
81.28
94 31
Detecting provenance variations and cooling patterns
40
Monesiglio
91
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
Ar(%)
D69
J=0.00164
D70
J=0.001634
0.00070
0.00051
0.00179
0.00462
0.00142
0.01403
0.00039
0.00000
0.00077
0.00233
0.00142
0.00082
0.00193
0.00362
0.00102
0.00000
0.00053
0.00000
0.00003
0.00012
0.00012
0.00000
0.00005
0.00000
0.00017
0.00000
0.00013
0.35096
0.19733
0.22648
0.01317
0.13103
0.22606
0.29496
0.29135
0.11893
5.06897
9.23657
6.88137
0.21446
5.53889
4.76486
5.46119
4.04194
3.18736
42.08 ±0.56
133 ±1.32
87.42 ±1.04
47.38 ±17.41
120.5 ±1.68
61.09 ±1.06
53.77 ±0.82
40.44 ±0.52
77.32 ±2.03
98.62
97.30
95.88
76.23
96.83
96.44
97.75
98.67
95.81
J=0.003126
0.00041
0.00050
0.00051
0.00075
0.00033
0.00000
0.00033
0.00053
0.00181
0.00094
0.00014
0.00000
0.00052
0.00000
0.00062
0.00046
0.00001
0.00000
0.00524
0.03995
0.00026
0.00062
0.00115
0.00133
0.00039
0.00026
0.00000
0.00059
0.00000
0.01113
0.31928
0.27863
0.56657
0.42293
0.28101
0.16212
0.03158
0.20097
0.02391
4.27744
3.52550
3.70268
3.78065
3.77504
3.55024
1.15266
0.85868
3.59369
0.37080
39.96818
61.22 ± 0.56
73.43 ± 0.67
37.25 ± 0.39
49.65 ± 0.58
69.88 ± 0.81
39.66 ± 0.88
147.17 ± 3.45
98.13 ± 0.87
85.40 ± 2.01
51.94 ± 0.27
96.71
96.12
97.48
97.46
86.93
96.62
84.88
95.16
98.96
96.26
J=0.003071
0.00031
0.00090
0.00023
0.00015
0.00056
0.00014
0.00196
0.00345
0.00096
0.00114
0.00005
0.00052
0.00323
0.00287
0.00001
0.00000
0.00058
0.00000
0.00097
0.00000
0.00032
0.00074
0.00066
0.00134
0.00130
0.00013
0.00028
0.00000
0.00120
0.00086
0.26298
0.15129
0.13347
0.30706
0.16493
0.00462
0.08169
0.05052
0.14688
0.11091
1.79600
1.34870
1.34241
2.78001
1.91568
0.03239
0.63954
0.53378
1.30843
3.19119
37.45 ± 0.49
48.73 ± 1.11
54.88 ± 1.23
49.48 ± 0.63
63.23 ± 0.78
38.41 ± 10.64
42.86 ± 3.04
57.61 ± 3.73
48.69 ± 1.62
152.76 ± 2.13
95.09
95.24
89.08
82.76
87.08
69.56
40.14
99.34
88.38
91.79
J=0.002755
0.00043
0.00000
0.00014
0.00000
0.00037
0.00000
0.00068
0.00045
0.00017
0.00067
0.00013
0.00005
0.00008
0.00008
0.00018
0.00023
0.00108
0.00039
0.00150
0.00140
0.00065
0.00017
0.00067
0.00060
0.19302
0.06476
0.20511
0.27721
0.08052
0.03805
0.07865
0.08581
2.35066
1.53669
2.60984
4.41082
1.06947
0.48558
0.85280
0.92044
59.53 ± 0.75
114.24 ± 1.69
62.16 ± 0.78
77.40 ± 0.63
64.84 ± 1.22
62.34 ± 2.26
53.10 ± 1.37
52.54 ± 1.04
94.85
97.46
95.94
95.67
95.50
92.55
97.42
94.47
190ab
190cd
192cd
190ef
192eg
190gh
192hi
190lm
192mn
B7
B10
B23
TFA
40
51.71 ±0.51
92
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Paroldo
D76
193ab
195ab
195cd
195fg
195hi
195no
195pq
195st
175uv
B20
Cortemilia
D43
D47
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
J=0.001597
0.00196
0.00000
0.00069
0.00000
0.00131
0.00000
0.00056
0.00000
0.00034
0.00033
0.00046
0.00280
0.00090
0.00488
0.00009
0.00038
0.00066
0.00000
0.00005
0.00000
0.00000
0.00003
0.00000
0.00001
0.00000
0.00007
0.00004
0.20382
0.11167
0.15480
0.01443
0.07709
0.06776
0.10028
0.05051
0.18646
7.93566
2.85653
4.04510
0.34248
2.21813
2.17695
2.14321
1.17246
10.03146
108.83 ± 1.23
72.23 ± 1.38
73.76 ± 1.23
67.1 ± 13.3
81.08 ±2.36
90.26 ±3.91
60.55 ±2.7
65.67 ±3.76
148.7 ±1.49
94.12
96.28
94.08
99.04
98.88
96.95
92.85
93.39
98.57
J=0.002834
0.00031
0.00053
0.00026
0.00019
0.00021
0.00048
0.00009
0.00018
0.00028
0.00000
0.00009
0.00000
0.00037
0.00000
0.00112
0.00096
0.00068
0.00144
0.00214
0.00039
0.00084
0.11904
0.10678
0.07601
0.00997
0.01432
0.01823
0.08275
0.86962
0.78993
1.06034
0.07543
0.10813
0.28796
1.10382
36.97 ± 0.88
37.43 ± 0.96
69.95 ± 1.37
38.26 ± 9.10
38.21 ± 7.29
79.00 ± 5.34
66.94 ± 1.21
90.52
91.19
94.44
74.44
56.87
91.56
90.89
38
39
40
J=0.001861
0.00020
0.01265
0.00062
0.00717
0.00240
0.00874
0.00025
0.00999
0.00073
0.00914
0.00122
0.00621
0.00020
0.00924
0.00003
0.00000
0.00007
0.01756
0.00000
0.00013
0.00000
0.00007
0.00000
0.00000
0.00000
0.00004
0.00005
0.00782
0.18707
0.13244
0.08270
0.07755
0.17614
0.09961
0.00726
0.09435
0.09842
3.35118
7.75815
1.25431
3.50471
3.36993
9.53589
0.08573
1.32626
41.78 ± 14.43
59.16 ± 0.63
186.67 ± 1.05
50.22 ± 1.33
145.69 ± 1.71
63.12 ± 0.56
295.78 ± 1.87
39.23 ± 11.48
46.59 ± 1.18
62.10
94.83
91.64
94.37
94.17
90.37
99.39
90.57
98.41
J=0.001828
0.00062
0.00227
0.00017
0.00061
0.00065
0.00189
0.00023
0.00000
0.00003
0.00000
0.00060
0.00000
0.00015
0.00000
0.00120
0.00645
0.00314
0.00000
0.00008
0.00375
0.00010
0.00004
0.00022
0.00015
0.00006
0.00006
0.00016
0.00009
0.00016
0.00004
0.10519
0.13871
0.21446
0.11885
0.05228
0.11130
0.06984
0.14060
0.13008
0.00402
6.12265
2.49623
3.45724
1.92817
1.34853
2.58222
1.37102
8.19261
2.97166
0.03998
182.41 ± 2.63
58.39 ± 0.70
52.40 ± 0.60
52.73 ± 1.36
83.11 ± 2.37
74.94 ± 1.21
63.61 ± 1.79
182.60 ± 1.60
73.81 ± 1.31
32.50 ± 25.34
97.11
98.00
94.72
96.66
99.39
93.60
96.91
95.85
76.20
62.31
(continued)
36
Ar(a)
37
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
40
Ar(%)
Detecting provenance variations and cooling patterns
40
Cortemilia
D56
D81
Murazzano
D48
B9
93
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
J=0.001739
0.00030
0.00000
0.00038
0.00000
0.00013
0.00332
0.00093
0.00000
0.00024
0.00290
0.00038
0.01412
0.00012
0.00987
0.00010
0.00000
0.00016
0.01165
0.00038
0.00498
0.00006
0.00000
0.00005
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00019
0.08945
0.14283
0.00718
0.14432
0.16771
0.00874
0.09659
0.00545
0.16664
0.10225
8.95995
5.97093
0.11389
7.66076
6.51132
0.10131
2.68299
0.09623
3.07933
1.79978
289.69 ± 2.83
126.60 ± 1.26
49.10 ± 15.89
159.28 ± 1.60
117.87 ± 0.83
36.00 ± 10.50
85.11 ± 0.92
54.60 ± 11.66
57.06 ± 0.76
54.39 ± 0.87
99.01
98.16
74.55
96.53
98.93
47.21
98.66
75.67
98.53
94.10
J=0.001565
0.00001
0.00000
0.00047
0.00451
0.00028
0.00000
0.00044
0.00000
0.00012
0.00082
0.00359
0.01538
0.00019
0.01589
0.00036
0.02986
0.00022
0.01898
0.00032
0.02256
0.00064
0.00254
0.00278
0.00929
0.00115
0.03604
0.00000
0.00010
0.00007
0.00000
0.00000
0.00004
0.00007
0.00002
0.00008
0.00020
0.00003
0.00007
0.00006
0.03974
0.08033
0.05417
0.05065
0.06914
0.22468
0.01972
0.04994
0.07171
0.04780
0.09834
0.14245
0.09937
0.63077
4.17747
2.48371
0.80757
9.39602
4.07134
0.75874
2.30631
9.12178
1.58515
2.78768
3.76182
10.08616
44.26 ± 1.51
141.16 ± 1.49
125.03 ± 1.11
44.46 ± 1.73
347.90 ± 2.87
50.45 ± 0.51
105.49 ± 5.15
125.89 ± 3.09
327.51 ± 4.80
91.29 ± 2.64
78.31 ± 1.43
73.06 ± 0.95
265.98 ± 4.46
99.32
96.77
96.80
86.26
99.62
79.35
93.25
95.59
99.30
94.30
93.62
82.06
96.75
36
Ar(a)
Ar(Ca)
J=0.001821
0.00102
0.00893
0.00101
0.00393
0.00044
0.01544
0.00081
0.00000
0.00016
0.00000
0.00023
0.00000
0.00221
0.00000
0.00127
0.00000
0.00037
0.00633
0.00029
0.01158
0.00018
0.00090
37
38
39
0.00011
0.00007
0.00001
0.00000
0.00004
0.00000
0.00007
0.00001
0.00003
0.00005
0.00004
0.21132
0.09568
0.09710
0.07976
0.14764
0.09301
0.16599
0.09918
0.12614
0.05420
0.03259
7.73155
3.44312
2.93672
1.83752
2.07513
1.07176
3.24008
3.89857
13.66040
1.73843
0.97916
116.36 ± 0.97
114.50 ± 1.73
96.71 ± 1.45
74.15 ± 2.70
45.59 ± 1.36
37.46 ± 2.13
63.01 ± 1.28
124.72 ± 2.28
324.71 ± 1.88
102.41 ± 2.52
96.10 ± 3.92
96.25
92.01
95.74
88.48
97.73
94.05
83.23
91.23
99.21
95.26
94.95
J=0.003089
0.00013
0.00082
0.00073
0.00056
0.00027
0.00034
0.00006
0.00063
0.00032
0.00145
0.00060
0.00081
0.00097
0.00063
0.00044
0.00075
0.00029
0.00000
0.00006
0.00000
0.00028
0.00000
0.00023
0.00025
0.00000
0.00044
0.00193
0.00132
0.00089
0.00032
0.00217
0.00098
0.00095
0.22652
0.41089
0.05148
0.01312
0.26553
0.20445
0.10989
0.07600
0.20004
0.00594
0.11300
1.77568
5.18311
0.61004
0.58978
2.30684
2.62401
2.71549
0.97370
1.36717
0.05043
0.78456
43.16 ± 0.40
68.96 ± 0.29
64.85 ± 2.74
234.51 ± 12.35
47.78 ± 0.72
70.14 ± 1.00
132.71 ± 1.57
70.02 ± 2.16
37.69 ± 1.93
46.70 ± 33.13
38.28 ± 2.09
97.81
95.99
88.43
96.96
96.06
93.65
90.49
88.21
94.13
73.39
90.48
(continued)
Ar(Cl)
Ar(K)
40
Ar(r)
Age 2V Ma
40
Ar(%)
94
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Murazzano
B29
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2VMa
36
J=0.002577
0.00044
0.00067
0.00108
0.00092
0.00059
0.00075
0.00073
0.00201
0.00036
0.00047
0.00025
0.00000
0.00039
0.00024
0.00061
0.00000
0.00006
0.00051
0.00115
0.00341
Cassinasco
D40
36
Ar(a)
37
Ar(Ca)
0.00053
0.00182
0.00168
0.00109
0.00088
0.00075
0.00051
0.00076
0.00082
0.00037
0.13158
0.17130
0.20913
0.11981
0.11041
0.09706
0.05818
0.12014
0.14348
0.13319
2.07542
4.17635
3.44964
3.32769
2.70065
1.22990
1.55052
1.63738
1.17065
5.28963
38
39
40
Ar(Cl)
Ar(K)
J=0.001888
D41
200ab
200cd
200fg
200hi
200no
200pq
200st
202bc
D49
122
184
Age
2 Ma
TFA
105.7 ±1.92
Ar(%)
94.15
92.92
95.20
93.93
96.16
94.42
93.02
90.02
98.40
93.98
40
Ar(%)
39
Ar(%)
10.17
13.23
16.16
9.26
8.53
7.50
4.50
9.28
11.09
10.29
39
Ar(%)
J=0.001878
0.00120
0.00130
0.00104
0.00445
0.00067
0.00000
0.00291
0.00000
0.00053
0.00304
0.00062
0.00000
0.00465
0.03999
0.00073
0.00124
0.00011
0.00011
0.00003
0.00000
0.00001
0.00000
0.00022
0.00018
0.38048
0.17019
0.41259
0.57131
0.15647
0.21670
0.70260
0.24561
10.69314
4.77855
4.79422
20.05338
6.13619
2.76107
13.90670
11.44977
92.79 ±0.69
92.71 ±1.02
38.95 ±0.43
115.2 ±0.71
128.2 ±1.73
42.66 ±1.16
65.84 ±1.27
151.4 ±1.11
98.66
95.63
99.26
97.01
97.89
95.77
95.53
98.16
74.55
76.30
97.80
97.14
95.05
15.67
98.48
77.13
J=0.001803
0.00918
0.00000
0.00918
0.00158
0.00918
0.00135
0.00918
0.00000
0.01558
0.00041
0.00126
0.00099
0.00206
0.00085
0.00620
0.00061
0.00164
0.00286
0.00178
0.00000
0.00000
0.00000
0.00000
0.00000
0.00005
0.00017
0.00018
0.00000
0.00000
0.00000
0.21078
0.27920
0.09199
0.17047
0.01056
0.15295
0.24627
0.28746
0.24125
0.14569
3.46377
14.05690
1.10806
2.21011
0.23810
5.67705
8.51992
11.73730
8.56335
2.83263
52.68 ± 2.10
156.75 ± 1.49
38.76 ± 4.10
41.69 ± 2.54
71.91 ± 43.70
116.87 ± 1.78
109.16 ± 0.95
128.15 ± 0.75
111.91 ± 0.98
62.16 ± 1.76
56.08
83.82
29.00
44.90
4.92
93.83
93.33
86.49
94.65
84.32
27.63
36.59
12.06
22.34
1.38
14.25
22.94
26.77
22.47
13.57
77.71 ± 0.76
TFA
52.43 ±0.49
69.08 ±0.71
71.43 ±1.29
106.5 ±10.5
114.5 ±1.6
74.37 ±2.63
64.62 ±2.15
68.7 ±0.62
73.77 ±2.4
98.79
98.68
98.93
98.52
98.58
94.43
97.55
98.07
92.42
D50
J=0.001793
D51
J=0.001783
0.00056
0.00000
0.00059
0.00042
0.00065
0.00280
0.00073
0.00391
0.00226
0.06519
0.00133
0.05905
0.00149
0.05709
0.00144
0.01706
0.00044
0.01006
203ab
203ce
203fg
203hi
203pq
203st
203uv
208ab
208cd
Ar(r)
71.88 ± 1.04
109.93 ± 0.66
75.10 ± 0.59
124.72 ± 1.03
110.27 ± 1.19
57.97 ± 1.67
119.82 ± 2.81
62.28 ± 1.26
37.54 ± 1.10
175.79 ± 1.28
40
0.00015
0.00011
0.00014
0.00023
0.00022
0.00032
0.00042
0.00024
0.00005
0.36421
0.39867
0.23056
0.33995
0.70990
0.40403
0.49672
0.41071
0.05389
6.02308
8.72783
5.22240
11.59065
26.09092
9.53687
10.15882
8.94133
1.26140
75.92
92.40
75.86
80.44
93.20
21.60
96.58
59.34
30.96
(continued)
Detecting provenance variations and cooling patterns
40
Cassinasco
D54
209b
209cd
209ef
209jl
209no
210bc
210de
210gh
210il
D64
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
J=0.001755
D55
95
40
Ar(%)
TFA
94.01 ±0.7
120.54 ±1.81
55.92 ±7.63
84.21 ±0.85
116.11 ±1.18
57.39 ±1.14
88.98 ±0.98
236.19 ±1.39
147.06 ±1.31
87.14 ±0.98
95.91
90.15
96.62
91.60
91.88
96.84
98.03
94.46
92.72
97.76 ± 0.95
152.08 ± 1.10
95.84 ± 0.59
85.22 ± 0.52
70.34 ± 3.51
76.75 ± 5.80
104.83 ± 2.45
79.56 ± 2.19
78.18 ± 43.07
97.47
97.26
96.79
97.12
97.59
94.01
97.06
94.99
88.35
J=0.001747
0.00057
0.00571
0.00096
0.00897
0.00096
0.00856
0.00271
0.01210
0.00028
0.01050
0.00072
0.00000
0.00264
0.00000
0.00261
0.00000
0.00125
0.01584
0.00000
0.00008
0.00000
0.00007
0.00013
0.00000
0.00009
0.00000
0.00000
0.09919
0.02650
0.27605
0.21435
0.10606
0.19157
0.35575
0.20928
0.15479
3.92317
0.47750
7.55033
8.15645
1.96222
5.54382
28.48430
10.17397
4.38469
J=0.001675
0.00056
0.00000
0.00088
0.00000
0.00112
0.00000
0.00088
0.00000
0.00009
0.00000
0.00027
0.00000
0.00043
0.00000
0.00065
0.00000
0.00008
0.00000
0.00000
0.00000
0.00032
0.00000
0.00011
0.00001
0.00002
0.00000
0.00000
0.19138
0.17509
0.30675
0.30453
0.04558
0.04860
0.11816
0.13516
0.00672
6.36258
9.19408
9.99170
8.79460
1.08187
1.26108
4.22067
3.63828
0.17773
D65
J=0.001668
B11
J=0.003052
0.00068
0.00000
0.00041
0.00017
0.00066
0.00000
0.00038
0.00000
0.00041
0.00000
0.00029
0.00000
0.00052
0.00020
0.00021
0.00046
0.00024
0.00000
0.00054
0.00054
0.00029
0.00076
0.00055
0.00036
0.00013
0.00029
0.00039
0.00011
0.00005
0.00057
0.38029
0.47620
0.12623
0.14264
0.09471
0.18471
0.11761
0.14548
0.10353
0.15385
4.22907
4.45147
3.55487
1.56721
0.85465
1.65350
2.00304
9.17756
1.19749
1.85755
60.22 ± 0.36
50.75 ± 0.27
148.76 ± 0.97
59.50 ± 0.75
49.01 ± 1.01
48.63 ± 0.58
91.42 ± 1.05
317.66 ± 1.01
62.59 ± 1.07
65.28 ± 0.83
95.44
97.34
94.80
93.27
87.68
95.01
92.83
99.34
94.50
92.04
J=0.002712
0.00077
0.00038
0.00032
0.00000
0.00016
0.00000
0.00039
0.00000
0.00044
0.00037
0.00018
0.00000
0.00018
0.00000
0.00049
0.00000
0.00062
0.00000
0.00064
0.00000
0.00034
0.00000
0.00006
0.00014
0.00044
0.00004
0.00020
0.00114
0.00082
0.00091
0.18185
0.15674
0.08506
0.17311
0.09283
0.09199
0.41221
0.21974
0.18277
0.31646
2.55486
2.09977
0.78331
10.12281
1.77921
0.71223
14.23411
1.74031
3.12162
3.16821
67.46 ± 0.90
64.38 ± 0.73
44.50 ± 1.19
265.56 ± 1.03
91.41 ± 1.16
37.49 ± 0.79
161.50 ± 0.41
38.34 ± 0.56
81.68 ± 0.78
48.33 ± 0.37
91.82
95.68
94.19
98.88
93.13
93.14
99.62
92.37
94.42
94.39
(continued)
B24
TFA
94.44 ± 0.69
96
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Cassinasco
B27
B34
Lequio
B26
B30
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
J=0.002634
0.00026
0.00097
0.00020
0.00037
0.00046
0.00027
0.00061
0.00031
0.00019
0.00074
0.00031
0.00018
0.00041
0.00038
0.00037
0.00048
0.00016
0.00077
0.00376
0.00099
0.00254
0.00089
0.00188
0.00103
0.00210
0.00101
0.00261
0.00080
0.00084
0.00250
0.01820
0.09403
0.23393
0.13414
0.02167
0.23263
0.48812
0.17393
0.16999
0.50528
0.12682
2.04448
3.29560
2.93910
0.19339
2.37194
5.12074
3.89705
1.55097
9.21999
32.82 ± 9.57
100.48 ± 1.78
65.73 ± 0.76
101.22 ± 1.35
41.91 ± 8.00
47.81 ± 0.48
49.18 ± 0.25
103.45 ± 0.54
42.84 ± 0.40
84.69 ± 0.62
62.56
97.22
96.06
94.22
77.94
96.31
97.68
97.30
97.04
89.23
J=0.002361
0.00023
0.00015
0.00024
0.00034
0.00061
0.00022
0.00098
0.00083
0.00019
0.00095
0.00003
0.00000
0.00027
0.00000
0.00034
0.00000
0.00015
0.00000
0.00017
0.00131
0.00022
0.00081
0.00109
0.00121
0.00100
0.00000
0.00028
0.00075
0.00107
0.00102
0.07622
0.18670
0.24472
0.17421
0.17702
0.04397
0.14661
0.17543
0.21101
0.19072
1.18007
4.31110
3.33059
3.62077
2.79856
0.83430
2.20300
4.09649
3.34448
3.04255
64.77 ± 1.65
95.77 ± 0.66
57.06 ± 0.55
86.42 ± 0.94
66.11 ± 0.69
79.07 ± 2.51
62.89 ± 0.73
96.82 ± 0.83
66.28 ± 0.60
66.70 ± 0.66
94.61
98.35
94.84
92.56
98.03
98.89
96.51
97.60
98.66
98.34
38
39
40
J=0.002674
0.00042
0.00025
0.00034
0.00000
0.00019
0.00000
0.00019
0.00029
0.00017
0.00030
0.00013
0.00000
0.00012
0.00000
0.00016
0.00000
0.00017
0.00000
0.00003
0.00000
0.00096
0.00087
0.00058
0.00086
0.00127
0.00104
0.00110
0.00105
0.00089
0.00048
0.21149
0.11740
0.10173
0.21642
0.09677
0.14888
0.15639
0.13109
0.08509
0.05112
3.17208
5.45333
7.00051
14.04228
0.96833
1.21692
9.64211
1.20167
1.02352
3.57944
70.94 ± 0.53
211.22 ± 1.27
304.72 ± 1.55
288.63 ± 1.23
47.64 ± 1.05
39.01 ± 0.76
275.31 ± 1.01
43.69 ± 0.90
57.11 ± 1.45
309.61 ± 3.17
96.22
98.19
99.21
99.59
94.95
96.94
99.64
96.26
95.19
99.75
J=0.002534
0.00066
0.00078
0.00029
0.00023
0.00010
0.00000
0.00011
0.00072
0.00009
0.00006
0.00001
0.00089
0.00101
0.00055
0.00009
0.00099
0.00013
0.00000
0.00042
0.00000
0.00130
0.00069
0.00022
0.00012
0.00056
0.00003
0.00069
0.00039
0.00044
0.00067
0.30676
0.13268
0.04477
0.23841
0.08686
0.12644
0.09900
0.14771
0.23068
0.06847
3.27013
1.12180
1.07362
14.25421
6.05692
9.42874
1.94140
10.06651
15.92031
2.54216
48.09 ± 0.47
38.24 ± 0.52
106.43 ± 1.93
254.50 ± 0.76
293.55 ± 1.54
312.25 ± 1.03
87.49 ± 1.10
287.39 ± 1.84
290.76 ± 0.55
162.21 ± 1.64
94.39
92.83
97.28
99.76
99.58
99.96
86.68
99.75
99.76
95.33
(continued)
36
Ar(a)
37
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
40
Ar(%)
Detecting provenance variations and cooling patterns
40
Lequio
A2
A4
A5
A6
97
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
J=0.001894
0.00075
0.03312
0.00119
0.03149
0.00091
0.03233
0.00109
0.03318
0.00160
0.02648
0.00312
0.00126
0.00033
0.00080
0.00059
0.00000
0.00127
0.00075
0.00046
0.00000
0.00020
0.00015
0.00020
0.00038
0.00059
0.00044
0.00045
0.00006
0.00011
0.00019
0.17065
0.21709
0.16490
0.13319
0.14182
0.20966
0.18840
0.12655
0.21678
0.12004
3.69348
4.09104
2.82484
4.67569
3.63433
7.80716
2.35081
2.49137
3.27260
1.88143
72.48 ± 4.79
63.27 ± 3.82
57.61 ± 4.93
116.13 ± 5.93
85.51 ± 5.88
122.95 ± 1.51
42.14 ± 1.53
66.04 ± 3.96
50.86 ± 2.48
52.78 ± 4.34
94.36
92.10
91.28
93.56
88.51
89.45
96.00
93.42
89.73
93.27
J=0.001892
0.00029
0.00105
0.00028
0.00400
0.00021
0.00351
0.00052
0.00214
0.00036
0.00022
0.00006
0.00000
0.00024
0.00314
0.00001
0.00064
0.00016
0.00052
0.00001
0.00000
0.00001
0.00018
0.00026
0.00012
0.00000
0.00035
0.00000
0.00000
0.00016
0.00051
0.05553
0.06457
0.06035
0.10711
0.06691
0.07782
0.03796
0.00475
0.04992
0.08422
1.20649
6.78426
6.09445
2.15708
1.18909
7.98449
0.92680
0.07099
1.14729
8.64381
72.68 ± 6.56
327.11 ± 6.83
315.42 ± 6.06
67.46 ± 3.77
59.66 ± 5.06
320.06 ± 6.42
81.48 ± 10.73
50.36 ± 82.80
76.78 ± 7.43
320.17 ± 5.15
93.43
98.79
98.97
93.32
91.82
99.78
92.99
96.17
96.04
99.95
J=0.001891
0.00085
0.00000
0.00067
0.00089
0.00074
0.00000
0.00084
0.00000
0.00061
0.00000
0.00024
0.00000
0.00030
0.00000
0.00057
0.00000
0.00072
0.00121
0.00022
0.00535
0.00022
0.00025
0.00032
0.00027
0.00053
0.00015
0.00008
0.00000
0.00015
0.00060
0.11662
0.18403
0.16509
0.16146
0.10538
0.04134
0.00577
0.16197
0.13745
0.09118
2.95591
4.15946
3.25583
3.04381
2.84253
0.89234
0.03726
3.34630
1.89997
8.51274
84.46 ± 2.25
75.50 ± 1.86
66.06 ± 1.61
63.19 ± 1.71
89.75 ± 2.50
72.17 ± 6.14
21.91 ± 41.50
69.14 ± 1.26
46.55 ± 1.78
293.31 ± 3.21
92.18
95.44
93.72
92.49
94.00
92.70
29.38
95.24
89.88
99.24
J=0.001890
0.00111
0.00000
0.00008
0.00310
0.00063
0.00242
0.00043
0.00244
0.00035
0.00543
0.00028
0.00183
0.00151
0.00667
0.00074
0.00087
0.00011
0.00229
0 00027
0 00366
0.00025
0.00000
0.00048
0.00010
0.00000
0.00004
0.00000
0.00033
0.00000
0 00032
0.28128
0.17956
0.20909
0.19090
0.26135
0.11697
0.16865
0.12450
0.10152
0 13407
8.60685
18.38102
3.79445
6.33614
25.61371
4.55877
11.78144
2.78421
9.80241
13 39523
101.43 ± 0.77
319.09 ± 2.08
60.84 ± 1.78
109.76 ± 1.66
306.58 ± 1.18
128.22 ± 2.74
223.73 ± 2.56
74.69 ± 2.19
302.40 ± 3.44
312 06 2 76
96.34
99.88
95.29
98.04
99.59
98.24
96.36
92.67
99.68
99 40
98
B. Carrapa, J. Wijbrans, and G. Bertotti
40
Present sands
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
Tanaro
B15
A31
B16
J=0.002958
0.00025
0.00000
0.00015
0.00041
0.00042
0.00115
0.00074
0.00082
0.00013
0.00049
0.00067
0.00198
0.00042
0.00011
0.00045
0.00075
0.00020
0.00086
0.00000
0.00026
0.00009
0.00070
0.00029
0.00000
0.00009
0.00046
0.00055
0.27447
0.21008
0.21213
0.21769
0.17809
0.24664
0.42222
0.29752
0.24714
16.49710
12.82995
13.50218
13.36759
11.09515
14.90981
26.47683
17.85984
1.76190
295.22 ± 1.33
299.59 ± 1.15
311.21 ± 1.34
301.10 ± 1.15
305.14 ± 1.23
296.79 ± 1.16
306.98 ± 0.87
294.87 ± 1.43
37.65 ± 0.68
99.56
99.65
99.08
98.39
99.64
98.69
99.53
99.25
96.72
J=0.001870
0.00000
0.00000
0.00065
0.00289
0.00013
0.00313
0.00031
0.00128
0.00015
0.00030
0.00049
0.00312
0.00029
0.00160
0.00023
0.00556
0.00037
0.00143
0.00081
0.00588
0.00021
0.00000
0.00000
0.00010
0.00000
0.00000
0.00000
0.00038
0.00000
0.00032
0.08279
0.17393
0.10144
0.11995
0.16233
0.19347
0.10937
0.16347
0.08356
0.30906
8.55896
5.98778
9.22355
11.37688
1.73807
16.77586
11.10519
15.59394
8.72244
30.54794
318.86 ± 2.39
112.56 ± 1.36
283.30 ± 3.16
294.57 ± 3.29
35.76 ± 1.47
271.10 ± 2.25
313.64 ± 3.22
296.13 ± 2.25
321.70 ± 4.82
305.97 ± 1.55
100.00
96.87
99.60
99.20
97.54
99.15
99.22
99.57
98.75
99.22
TFA
314.7 ±2.64
J=0.002934
Stura
B17
A33
B18
J=0.002910
0.00029
0.00416
0.00094
0.00000
0.00024
0.00000
0.00022
0.00000
0.00028
0.00078
0.00012
0.00035
0.00026
0.00084
0.00010
0.00105
0.00025
0.00048
0.00000
0.00121
0.00107
0.00091
0.00084
0.00000
0.00010
0.00008
0.00181
0.74567
0.64183
0.48989
0.44144
0.42577
0.20521
0.15220
0.45785
0.35343
43.77489
39.15587
30.12441
26.80567
26.06749
12.63738
9.55720
28.69089
21.13772
284.53 ± 0.63
294.82 ± 0.85
296.98 ± 1.41
293.56 ± 0.98
295.79 ± 0.84
297.38 ± 1.55
302.77 ± 1.39
302.20 ± 1.07
289.47 ± 1.34
99.81
99.30
99.76
99.75
99.68
99.72
99.20
99.90
99.65
J=0.001868
0.00015
0.00259
0.00018
0.00008
0.00036
0.00178
0.00052
0.00399
0.00030
0.00449
0.00122
0.00451
0.00013
0.00161
0.00108
0.00000
0.00050
0.00119
0.00070
0.00111
0.00049
0.00035
0.00028
0.00040
0.00035
0.00052
0.00002
0.00000
0.00004
0.00000
0.35855
0.16345
0.32403
0.09496
0.10051
0.21609
0.13643
0.14197
0.13416
0.20369
21.87660
16.17064
32.69575
9.55715
10.66317
21.01410
14.38491
13.96509
13.65997
18.75177
294.86 ± 0.91
305.93 ± 3.12
311.53 ± 1.84
310.80 ± 4.40
326.17 ± 4.50
301.13 ± 2.93
324.34 ± 3.23
304.32 ± 3.34
314.12 ± 3.52
286.28 ± 2.71
99.80
99.66
99.67
98.41
99.17
98.31
99.73
97.76
98.92
98.91
TFA
305.87 ±1.85
J=0.002879
(continued)
Detecting provenance variations and cooling patterns
40
Present sands
99
39
TABLE A2. Ar/ Ar ANALYSES OF THE INVESTIGATED SAMPLES (continued)
37
38
39
40
Ar(a)
Ar(Ca)
Ar(Cl)
Ar(K)
Ar(r)
Age 2V Ma
36
40
Ar(%)
Maira
B13
A34
J=0.003012
0.00242
0.00078
0.00171
0.00116
0.00158
0.00113
0.00124
0.00001
0.00119
0.00033
0.00104
0.00000
0.00037
0.00001
0.00048
0.00043
0.00124
0.00071
0.00063
0.00071
0.00044
0.00095
0.00113
0.00134
0.00082
0.00062
0.00040
0.00062
0.00116
0.00086
0.74100
0.53839
0.26651
0.21017
0.29666
0.12663
0.26605
0.33386
0.37491
0.26613
11.98409
16.48979
4.23196
3.74044
4.15063
0.93653
3.02743
3.85268
6.85901
6.12037
85.81 ± 0.45
159.19 ± 0.59
84.28 ± 0.79
94.21 ± 0.87
74.47 ± 0.44
39.75 ± 1.35
60.80 ± 0.58
61.64 ± 0.44
96.77 ± 17.96
120.83 ± 0.62
94.37
97.02
90.07
91.07
92.17
75.27
96.46
96.44
94.93
97.05
J=0.001867
0.00088
0.00559
0.00098
0.00459
0.00441
0.00651
0.00104
0.00407
0.00106
0.00497
0.00199
0.00093
0.00351
0.00502
0.00114
0.00454
0.00277
0.00000
0.00060
0.00315
0.00007
0.00029
0.00000
0.00000
0.00058
0.00039
0.00002
0.00005
0.00000
0.00021
0.42525
0.35456
0.43850
0.29468
0.16429
0.21428
0.39586
0.41556
0.42950
0.33274
7.80664
6.16508
9.90354
5.44614
2.70191
5.00788
8.27521
7.94239
8.64451
5.57909
60.80 ± 1.14
57.64 ± 1.21
74.51 ± 1.03
61.20 ± 1.49
54.56 ± 3.12
77.05 ± 0.95
69.07 ± 0.59
63.25 ± 0.49
66.55 ± 0.58
55.61 ± 0.65
96.77
95.52
88.37
94.64
89.59
89.49
88.85
95.94
91.35
96.93
B14
J=0.002985
TFA
75.9 ±0.6
40
39
Note: The Molare data are part of the paper of Barbieri et al. (2003). The values (mols. and %) listed for the Ar/ Ar
36
36
37
37
38
experiments are Ar(a): atmospheric component in Ar; Ar(Ca): calcium-derived Ar; Ar(Cl): chlorine-derived
38
39
39
40
40
component Ar; Ar(K): potassium-derived component in Ar; Ar(r): radiogenic Ar; Age (Ma) with related 2Verrors;
40
37
Ar(%): percentage radiogenic component in Ar. Note that Ar in the experiments was low and indistinguishable from
the blank. This could have been the result of sample preparation, which included a leaching step with nitric acid to
dissolve the carbonate fraction and enable better mica separation. Time between sample irradiation and the analyses
37
of reported data was never more than 4 months (T1/2 Ar = 35.1 days). D—VU32; B—VU36; A—VU41. TFA—total
fusion ages (see Table A3).
REFERENCES CITED
Agard, P., Monié, P., Jolivet, L., and Goffé, B., 2002, Exhumation of the
Schistes Lustrés complex: in situ laser probe 40Ar/39Ar constraints and
implications for the Western Alps: Journal of Metamorphic Geology,
v. 20, p. 599–618.
Arnaud, N.O., and Kelley, S.P., 1995, Evidence for excess argon during high
pressure metamorphism in the Dora Maira Massif (Western Alps, Italy),
using an ultra-violet laser ablation microprobe 40Ar/39Ar technique: Contributions to Mineralogy and Petrology, v. 121, p. 1–11.
Barbieri, C., Carrapa, B., Di Giulio, A., Wijbrans, J., and Murrell, G., 2003,
Provenance of Oligocene synorogenic sediments of the Ligurian Alps
(NW Italy): Inferences on the belt age and its cooling history: International Journal of Earth Sciences, v. 92, p. 758–778.
Beaumont, C., Ellis, S., Hamilton, J., and Fullsack, P., 1996, Mechanical model
for subduction-collisional tectonics of Alpine-type compressional orogens: Geology, v. 24, p. 675–678.
Berggren, W.A., Kent, D.V., Aubry, M.P., Hardenbol, J., 1995, Geochronology,
time scales and global stratigraphic correlation; unified temporal framework for an historical geology, in Berggren, W.A., et al., eds., Geochronology, time scales and global stratigraphic correlation: SEPM (Society
for Sedimentary Geology) Special Publication 54, p. 130–212.
Bernet, M., Zattin, M., Garvar, J.I., Brandon, M.T., and Vance, J.A., 2001,
Steady-state exhumation of European Alps: Geology, v. 29, p. 35–38.
Bertotti, G., Capozzi, R., and Picotti, V., 1997, Extension controls Quaternary tectonics, geomorphology and sedimentation of the N-Apennines
foothills and adjacent Po Plain (Italy): Tectonophysics, v. 282, no. 1–4,
p. 291–301.
Bigot-Cormier, C.F., Poupeau, G., and Sosson, M., 2000, Denudations differentielles du massif cristallin externe alpin de l’Argentera (Sud-Est
de la France) revelees par thermochronologie traces de fission (apatites,
zircons); Translated Title: Differential denudation of the Alpine Argentera
crystalline massif, southeastern France, analyzed by fission track thermochronology of zircons and apatites: Comptes Rendus de l’Academie des
Sciences, Serie II, v. 330, no. 5, p. 363–370.
Brandon, M.T., and Vance, J.A., 1992, Tectonic evolution of the Cenozoic
Olympic subduction complex, Washington State, as deduced from fission track ages for detrital zircons: American Journal of Science, v. 292,
p. 565–636.
Brouwer, F.M., 2000, Thermal evolution of high-pressure metamorphic rocks in
the Alps [Ph.D. thesis]: Utrecht, Netherlands, Univeristeit Utrecht, ISBN
90–5744–056–3, 221 p.
Caprara, L., Garzanti, E., Gnaccolini, M., and Mutti, L., 1985, Shelf-basin
transition: Sedimentology and petrology of the Tertiary Piedmont Basin
100
B. Carrapa, J. Wijbrans, and G. Bertotti
(Northern Italy): Rivista Italiana di Paleontologia e Stratigrafia, v. 90,
p. 545–564.
Carrapa, B., and Di Giulio, A., 2001, The sedimentary record of the exhumation of a granitic intrusion into a collisional setting: the lower Gonfolite
Group, Southern Alps, Italy: Sedimentary Geology, v. 139, p. 217–228.
Carrapa, B., and Wijbrans, J., 2003, Cretaceous 40Ar/ 39Ar detrital mica ages
in Tertiary sediments, solving the debate on the Eo-Alpine evolution?, in
Forster, M., and Wijbrans, J., eds., Geochronology and Structural geology: Journal of the Virtual Explorer, v. 13 (online).
Carrapa, B., Wijbrans, J., and Bertotti, G., 2003, Episodic exhumation in the
Western Alps: Geology, v. 31, p. 601-604.
Cazzola, C., and Fornaciari, M., 1990, Geometry and Facies of the Budroni
and Noceto Turbidite systems (Tertiary Piedmont Basin): Atti Ticinesi di
Scienze della Terra, v. 33, p. 177–190.
Cazzola, C., and Sgavetti, M., 1984, Geometrie dei depositi torbiditici della
Formazione di Rocchetta e Monesiglio (Oligocene superiore–Miocene
inferiore) nell’area compresa tra Spigno e Ceva: Giornale di Geologica,
v. 45, p. 227–240.
Cazzola, C., Fonnesu, F., Mutti, E., Rampone, G., Sonnino, M., and Vigna, B.,
1981, Geometry and facies of small, fault-controlled deep-sea fan in a
transgressive depositional setting, tertiary Piedmont Basin, North Western Italy, in Libro Guida alle escursioni, 2nd International Association of
Sedimentologists European Regional Meeting, v. 33, p. 177–190.
Chopin, C., 1984, Coesite and pure pyrope in high grade blueschists of the
Western Alps: A first record and some consequences: Contributions to
Mineralogy and Petrology, v. 86, p. 107–118.
Chopin, C., and Maluski, H., 1980, 40Ar/39Ar dating of high pressure metamorphic micas from the gran Paradiso area (western Alps): evidence against
the blocking temperature concept: Contributions to Mineralogy and
Petrology, v. 74, p. 109–122.
Chopin, C., and Monié, P., 1984, A unique magnesiochloritoid–bearing high–
pressure assemblage from the Monte Rosa, western Alps: Petrologic and
40
Ar/39Ar radiometric study. Contributions to Mineralogy and Petrology,
v. 87, p. 388–398.
Cimmino, F., Messiga, B., and Piccardo, G.B., 1981, Le caratteristiche paragenetiche dell’evento eo–Alpino di alta pressione nei diversi sistemi
(pelitici, femici, ultrafemici) delle ofioliti metamorfiche del Gruppo di
Voltri (Liguria occidentale): Rendiconti della Societa Italiana di Mineralogia e Petrologia, v. 37, no. 1, p. 419–446.
Clari, P., Dela Pierre, F., Novaretti, A., Timpanelli, M., 1995, Late Oligocene–Miocene sedimentary evolution of the critical Alps/Appennines
junction: the Monferrato area, Northwestern Italy: Terra Research, v. 7,
p. 144–152.
Cliff, R.A., Barnicoat, A.C., and Inger, S., 1998, Early Tertiary eclogite facies
metamorphism in the Monviso Ophiolite: Journal of Metamorphic Geology, v. 16, p. 447–455.
Compagnoni, R., and Lombardo, B., 1974, The Alpine age of the Gran Paradiso
eclogites: Rendiconto della Societa Italiana di Mineralogia e Petrografia,
v. 30, p. 223–237.
Compagnoni, R., Hirajima, T., and Chopin, C., 1995, Ultra-high pressure
metamorphic rocks in the Western Alps, in Coleman, R.G., and Wang,
X., eds., Ultrahigh pressure metamorphism: Cambridge, UK, Cambridge
University Press, p. 206–243.
Cortiana, G., Dal Piaz, G.V., Del Moro, A., Hunziker, J.C., and Martin, S., 1998,
40
Ar/39Ar and Rb-Sr dating of the Pillonet klippe and Sesia-Lanzo basal
slice in the Ayas valley and evolution of the Austroalpine-Piedmont nappe
stack: Memoria della Società Geologica Italiana, v. 50, p. 177–194.
Dal Piaz, D.V., 1999, The Austroalpine-Piedmont nappe stack and the puzzle of
Alpine Tethys: Memorie Scienze Geologiche, v. 51, no. 1, p. 155–176.
D’Antonio, D., Gosso, G., Messiga, B., Scambelluri, M., and Tallone, S., 1984,
Structural analysis and lithostratigraphic reconstruction of the southwestern margin of the Voltri Massif, Piemontaise-Ligurian zone, Ligurian
Alps: Memoria della Societa Geologica Italiana, Reports of the congress
on the Geology of the Ligurian Alps, v. 28, p. 447–460.
Dickinson, W.R., and Suczek, C.A., 1979, Plate tectonics and sandstone compositions: Bulletin of the American Association of Petroleum Geologists,
v. 63, p. 2164–2172.
Dondi, L., and D’Andrea, M.G., 1986, La Pianure Padana e Veneta
dall’Oligocene superiore al Pleistocene: Giornale di Geologia, v. 48,
p. 197–225.
Fannucci, F., 1986, Évolution stratigraphique de la région du Golfe de Gênes
depuis l’Eocène Supérior: Memorie della Società Geologica Italiana,
v. 36, p. 19–30.
Foeken, J.P.T., Dunai, T.J., Bertotti, G., and Andriessen, P.A.M., 2003, Late
Miocene to present exhumation in the Ligurian Alps (southwest Alps)
with evidence for accelerated denudation during the Messinian salinity
crisis: Geology, v. 31, p. 797–800.
Foland, K.A., 1983, 40Ar/39Ar incremental heating plateaus for biotites with
excess argon: Isotope Geoscience, v. 1, p. 3–21.
Fravega, P., Piazza, M., Stockar, R., and Vannucci, G., 1994, Oligocene coral
and algal reef and related facies of Valzamola (Savona, NW Italy): Rivista
Italiana di Paleontologia e Stratigrafia, v. 3, p. 423–456.
Freeman, S.R., Inger, S., Butler, R.W.H., and Cliff, R.A., 1997, Dating deformation using Rb-Sr in white mica: Greenschist facies deformation ages
from the Entrelor shear zone, Italian Alps: Tectonics, v. 16, p. 57–76.
Frisch, W., Kuhlemann, J., Dunkl, I., and Brügel, A., 1998, Palinspastic reconstruction and topographic evolution of the eastern Alps during late tertiary
tectonic extrusion: Tectonophysics, v. 297, p. 1–15.
Gebauer, D., 1999, Alpine geochronology of the Central and Western Alps:
New constraints for a complex geodynamic evolution: Schweizerische
Mineralogische und Petrographische Mitteilungen, v. 79, p. 191–208.
Gebauer, D., Schertl, H.P., and Brix, M., 1997, 35 Ma old ultrahigh–pressure
metamorphism and evidence for very rapid exhumation in the Dora Maira
massif, Western Alps: Lithos, v. 41, p. 5–24.
Gelati, R., 1968, Stratigrafia dell’Oligo–Miocene delle Langhe tra le valli dei
fiumi Tanaro e Bormida di Spigno: Rivista Italiana di Paleontologia e
Stratigrafia, v. 74, p. 865–967.
Gelati, R., and Gnaccolini, M., 1982, Evoluzione tettonico-sedimentaria della
zona limite tra Alpi ed Appennini tra l’inizio dell’Oligocene ed il Miocene
medio: Memoria della Società Geologica Italiana, v. 24, p. 183–191.
Gelati, R., and Gnaccolini, M., 1996, The Stratigraphic record of the Oligocene–Early Miocene events at the southwestern end of the Piedmont
Tertiary Basin: Rivista Italiana di Paleontologia e Stratigrafia, v. 102,
no. 1, p. 65–76.
Gelati, R. and Gnaccolini, M., 1998, Synsedimentary tectonics and sedimentation in the Tertiary Piedmont Basin, Northwestern Italy: Rivista Italiana
di Paleontologia e Stratigrafia, v. 104, no. 2, p. 193–214.
Gelati, R., Gnaccolini, M., Falletti, P., and Catrullo, D., 1993, Stratigrafia
sequenziale della successione Oligo-Miocenica delle Langhe, Bacino
Terziario Ligure-Piemontese: Rivista Italiana di Paleontologia e Stratigrafia, v. 98, no. 4, p. 425–452.
Gnaccolini, M., 1970, Andamento della linea di costa durante la trasgressione
oligocenica nella regione tra Bandita (AL) e Celle Ligure (SV): Rivista
Italiana di Paleontologia e Stratigrafia, v. 76, p. 327–336.
Gnaccolini, M., 1974, Osservazioni sedimentologiche sui conglomerati oligocenici del settore meridionale del Bacino Terziario Ligure–Piemontese:
Rivista Italiana di Paleontologia e Stratigrafia, v. 80, no. 1, p. 85–100.
Gnaccolini, M., and Rossi, P.M., 1994, Sequenze deposizionali e composizione
delle arenarie nel Bacino Terziario Ligure-Piemontese: Osservazioni preliminari: Atti Ticinesi di Scienze della Terra, v. 37, p. 3–15.
Gnaccolini, M., Gelati, R., Catrullo, D., and Falletti, P., 1990, Sequenze deposizionali nella successione oligo–miocenica delle “Langhe”: Un approccio alla stratigrafia sequenziale del Bacino Terziario Ligure-Piemontese:
Memoria della Società Geologica Italiana, v. 45, p. 671–686.
Gnaccolini, M., Gelati, R., and Falletti, P., 1998, Sequence stratigraphy of the
“Langhe” Oligo-Miocene succession, Tertiary Piedmont Basin, Northern
Italy, in de Graciansky, P.C., Harbendol, J., Jacquin, T., and Vail, P., eds.,
Mesozoic and Cenozoic sequence stratigraphy of European Basins:
SEPM (Society for Sedimentary Geology) Special Publication, v. 60,
p. 234–244.
Hames, W.E., and Bowring, S.A., 1994, An empirical evaluation of the argon
diffusion geometry in muscovite: Earth and Planetary Science Letters,
v. 124, p. 161–167.
Haq, B.U., Hardenbol, J., and Vail, P.R., 1988, Mesozoic and Cenozoic Chronostratigraphy and Cycles of sea-level change, in Wilgus, C.K., Hastings,
B.S., Posamentier, H., Van Wagoner, J., Ross, C.A., and Kendall, C.G.St.,
eds., Sea-level changes: An integrated approach: Society of Economic
Paleontologists and Mineralogists, Special Publication 42, p. 71–108.
Harrison, T.M., Copeland, P., Hall, S.A., Quade, J., Burner, S., Ojha, T.P., and
Kidd, W.S.F., 1993, Isotopic preservation of Himalayan/Tibetan Uplift,
Denudation, and Climatic Histories of two molasse deposits: Journal of
Geology, v. 101, p. 157–175.
Heller, P.L., Renne P.R., and O’Neil, J.R., 1992, River mixing rate, residence
time, and subsidence rates from isotopic indicators: Eocene sandstones of
the U.S. Pacific Northwest: Geology, v. 20, p. 1095–1098.
Detecting provenance variations and cooling patterns
Hunziker, J.C., Desmons, J., and Hurford, A.J., 1992, Thirty-two years of geochronological work in the Central and Western Alps, a review on seven
maps: Mémoires de Géologie, Lausanne, no. 13, p. 59.
Hurford, A.J., and Hunziker, J.C., 1989, A revised thermal history for the Gran
Paradiso massif: Schweizerische Mineralogische und Petrographische
Mitteilungen, v. 69, p. 319–329.
Hurford, A.J., Hunziker, J.C., and Stockert, B., 1991, Constraints on the late
thermotectonic evolution of the western Alps: Evidence for episodic rapid
uplift: Tectonics, v. 10, p. 758–769.
Inger, S., Ramsbotham, W., Cliff, R.A., and Rex, D.C., 1996, Metamorphic
evolution of the Sesia-Lanzo Zone, Western Alps: Time constraints from
multi-system geochronology: Contributions to Mineralogy and Petrology,
v. 126, p. 152–168.
Kelley, S.P., Arnaud, N.O., and Okay, A.I., 1994, Anomalously old Ar-Ar ages
in high pressure methamorphic terrains: Mineralogial Magazine, v. 58,
no. A, p. 468–469.
Kirschner, D.L., Cosca, M.A., Masson, H., and Hunziker, J.C., 1996, Staircase
40
Ar/39Ar spectra of fine-grained white mica: Timing and duration of
deformational and empirical constraints on argon diffusion: Geology,
v. 24, p. 747–750.
Kohn, M.J., Spear, F.S., Harrison, T.M., and Dalziel, I.W.D., 1995, 40Ar/39Ar
geochronology and P-T-t paths from the Cordillera Darwin metamorphic
complex, Tierra del Fuego, Chile: Journal of Metamorphic Geology,
v. 13, p. 251–270.
Koppers, A.P., 2002, ArArCALC-software for 40Ar/39Ar age calculations: Computers and Geosciences, v. 28, p. 605–619.
Kuiper, K., 2003, Direct intercalibration of radio-isotopic and astronomical
time in the Mediterranean Neogene [Ph.D. Thesis]: Utrecht, Netherlands,
Utrecht University, 223 p.
Lorenz, C., 1979, L’Oligo-Miocène ligure: Un example de transgression: Bulletin de la Société Géologique de France, v. 12, p. 375–378.
Lorenz, C., 1984, Evolution stratigraphique et structurale des Alpes Ligures
depuis l’Eocene superieur: Memoria della Società Geologica Italiana,
v. 28, p. 211–228.
McDougall, I., and Harrison, T.M., 1999, Geochronology and Thermochronology by the 40Ar/39Ar Method: Oxford, UK, Oxford University Press,
269 p.
Menot, R.P., Raumer, J.F. von, Bogdanoff, S., and Vivier, G., 1994, Variscan
basement of the Western Alps: the Alpine Crystalline Massifs, in Keppie,
J.D., ed., The Pre-Mesozoic Terranes in France and Related Areas:
Springer, p. 458–466.
Messiga, B., 1981, Structural and paragenetic evidence of polyphase evolution
of the Prealps of Savona crystalline Massif: Rendiconti della Società Italiana di Mineralogia e Petrologia, v. 37, no. 2, p. 739–754.
Messiga, B., 1984, Il metamorpfismo alpino nelle Alpi Liguri: alcuni aspetti
petrologici: Memoria della Società Geologica Italiana, v. 28, p. 151–179.
Messiga, B., and Scambelluri, M., 1991, Retrograde P-T-t path for the Voltri
Massif eclogites (Ligurian Alps, Italy); some tectonic implications: Journal of Metamorphic Geology, v. 9, no. 1, p. 93–109.
Messiga, B., Piccardo, G.B., Rampone, E., and Scambelluri, M., 1989, Primary
characters and high pressure metamorphic evolution of the subducted
oceanic lithosphere of the Voltri Massif (Ligurian Alps, northern Italy):
Ofioliti, v. 14, no. 3, p. 157–175.
Messiga, B., Tribuzio R., and Caucia, F., 1992, Amphibole evolution in Varisican eclogite-amphibolites from the Savona crystalline massif (Western
Ligurian Alps, Italy: controls on the decompressional P-T-t path): Lithos,
v. 27, p. 215–230.
Michard, A., Chopin, C., and Henry, C., 1993, Compression versus extension
in the exhumation of the Dora Maira coesite-bearing unit, Western Alps,
Italy: Tectonophysics, v. 221, p. 173–193.
Monié, P., 1985, La méthode 40Ar/39Ar appliqué au metamorphisme alpine
dans le massif du Mont Rose (Alpes occidentales): Chronologie détaillée
depuis 110 Ma: Eclogae Geologica Helvetica, v. 3, p. 487–516.
Monié, P., and Chopin, C., 1991, 40Ar/39Ar dating in coestite-bearing and associated units of the Dora Maira massif, Western Alps: European Journal of
Mineralogy, v. 3, p. 239–262.
Monié, P., and Maluski, H., 1983, Ar-Ar geochronologic data on the pre-Permian basement of the Argentera–Mercantour Massif, Alpes Maritimes,
France: Bulletin de la Société Géologique de France, v. 25, no. 2,
p. 247–257.
Mutti, E., and Normark, W.R., 1987, Comparing examples of modern and
ancient turbidite system: Problems and concepts, in Legget, J.K., and
101
Zuffa, G.G., eds., Marine clastic sedimentology: Concepts and case studies: London, UK, Graham & Trotman Ltd., p. 1–38.
Mutti, E., Papani, L., Di Biase, D., Davoli, G., Mora, S., Segadelli, S., and
Tinterri, R., 1995, Il Bacino Terziario Epimesoalpino e le sue implicazioni
sui rapporti tra Alpi ed Appennino: Memorie di Scienze Geologiche di
Padova, v. 47, p. 217–244.
Najman, Y., Pringle, M., Godin, L., and Grahame, O., 2001, Dating of the oldest
continental sediments from the Himalayan foreland basin: Nature, v. 410,
p. 194–197.
Najman, Y.M.R., Pringle, M.S., Johnson, M.R.W., Robertson, A.H.F., and
Wijbrans, J.R., 1997, Laser 40Ar/39Ar dating of single detrital muscovite
grains from early foreland-basin sedimenatry deposits in India: Implications for early Himalayan evolution: Geology, v. 25, p. 535–538.
Neubauer, F., Handler, R., and Dallmeyer, R.D., 1996. Mica tectonics: Constraints for crustal rejuvenation and growth of continents: Geological
Society of America Abstracts with Programs, v. 28, no. 7, p. A-502.
Oberhänsli, R., Hunziker, J.C., Martinotti, G., and Stern, W.B., 1985, Geochemistry, geocronology and petrology of Monte Mucrone: An example
of Eoalpine eclogitization of Permian granitoids in the Sesia-Lanzo Zone,
Western Alps, Italy: Isotope Geoscience, v. 52, p. 165–184.
Paquette, J.L., Chopin, C., and Peucat, J.J., 1989, U-Pb zircon, Rb-Sr and SmNd geochronology of high to very high pressure meta-acidic rocks from
the western Alps: Contributions to Mineralogy and Petrology, v. 101,
no. 280–289.
Platt, J.P., Behrmann, J.H., Cunningham, P.C., Dewey, J.F., Helman, M., Parish,
M., Shepley, M.G., Wallis, S., and Weston, P.J., 1989, Kinematics of the
Alpine arc and the motion of Adria: Nature, v. 337, p. 158–161.
Polino, R., Dal Piaz, G., and Gosso, G., 1990, Tectonic erosion at the Adria
margin and accretionary processes for the Cretaceous orogeny of the
Alps, in Roure, F., Heitzmann, P., and Polino, R., eds., Deep structure
of the Alps, Société Géologique de France, Société Geologique Suisse,
Società Geologica Italiana, p. 345–367.
Renne, P.R., Becker, T.A., and Swapp, S.M., 1990, 40Ar/39Ar laser-probe dating
of detrital micas from the Montgomery Creek Formation: Clues to provenance, tectonics, and weathering processes: Geology, v.18, p. 563–566.
Renne, P.R., Swischer, C.C., Deino, A.L., Karner, D.B., Owens, T.L., and
DePaolo, D.J., 1998, Intercalibration of standards, absolute ages and
uncertainties in 40Ar/39Ar dating: Chemical Geology, v. 145, p. 117–152.
Roure, F., Polino, R., and Nicolich, R., 1990, Early Neogene deformation
beneath the Po Plain: constraints on the post–collisional Alpine evolution:
Mémoire de la Société Géologique de France, v. 156, 309–322.
Rubatto, D., and Hermann, J., 2001, Exhumation as fast as subduction?: Geology, v. 29, p. 3–6.
Rubatto, D., Gebauer, D., and Compagnoni, R., 1999, Dating of eclogite-facies
zircons: the age of Alpine metamorphism in the Sesia-Lanzo Zone (Western Alps): Earth and Planetary Science Letters, v. 167, p. 141–158.
Ruffet, G., Féraud, G., Ballèvre, M., and Kiénast, J.R., 1995, Plateau ages and
excess argon in phenigites: an 40Ar-39Ar laser probe study of Alpine micas
(Sesia Zone, Western Alps, northern Italy): Chemical Geology, v. 121,
p. 327–343.
Ruffet, G., Gruau, G., Ballèvre, M., Feraud, G., and Philippot, P., 1997, RbSr and 40Ar-39Ar laser probe dating of high–pressure phengites from the
Sesia zone (Western Alps): Underscoring of excess argon and new age
constraints on the high-pressure metamorphism: Chemical Geology,
v. 141, p. 1–18.
Scaillet, S., Féraud, G., Ballèvre, M., and Amouric, M., 1992, Mg/Fe and
[(Mg,Fe)Si–Al2] compositional control on Ar behaviour in high-pressure
white micas: A continuous 40Ar/39Ar laser-probe study from the DoraMaira nappe of the Western Alps, Italy: Geochimica et Cosmochimica
Acta, v. 56, p. 2851–2872.
Scaillet, S., Féraud, G., Lagabrielle, Y., Ballèvre, M., and Ruffet, G., 1990,
40
Ar/39Ar laser-probe dating by step heating and spot fusion of phengites
from the Dora Maira nappe of the Western Alps, Italy: Geology, v. 18,
p. 741–744.
Schamel, S., and Hunziker, J., 1977, Eocene-Oligocene blueschist facies metamorphism in Liguria, Italy, and Alpine Corsica: Geological Society of
America Abstracts with Programs, v. 9, no. 7, p. 1158–1159.
Schlunegger, F., and Willett, S., 1999, Spatial and temporal variations in exhumation of the central Swiss Alps and implications for exhumation mechanisms, in Ring, U., Brandon, M.T., Lister, G.S., and Willett, S.D., eds.,
Exhumation processes: Normal faulting, ductile flow and erosion: London, Geological Society [London] Special Publication 154, p. 157–179.
102
B. Carrapa, J. Wijbrans, and G. Bertotti
Schmid, S.M., Aebli, H.R., and Zingg, A., 1989, The role of the Periadriatic
Line in the tectonic evolution of the Alps, in Coward, M., Dietrich, D., and
Park, R.G., eds., Alpine Tectonics: London, Geological Society [London]
Special Publication 45, p. 153–171.
Sircombe, K.N., 1999, Quantitative comparison of large sets of geochronological data using multivariate analysis: A provenance study example from
Australia: Geochimica et Cosmochimica Acta, v. 64, no. 9, p. 1593–
1616.
Sircombe, K.N., 2000, The utility and limitations of binned frequency histograms and probability density distributions for displaying absolute age
data: Geological Survey of Canada Current Research, v. F2, p. 11.
Spiegel, C., Kuhlemann, J., Dunkl, I., and Frisch, W., 2001, Paleogeography
and catchment evolution in a mobile orogenic belt: the Central Alps in
Oligo-Miocene times: Tectonophysics, v. 341, p. 33–47.
Steenbrink, J., van Vugt, N., Hilgen, F.J., Wijbrans, J.R., and Meulenkamp, J.E.,
1999, Sedimentary cycles and volcanic ash beds in the lower Pliocene
lacustrine succession of Ptolemais (NW Greece); discrepancy between
40
Ar/39Ar and astronomical ages: Palaeogeography, Palaeoclimatology,
Palaeoecology, v. 152, no. 3–4, p. 283–303.
Stöckhert, B., Jäger, E., and Voll, G., 1986, K-Ar age determinations on phengite from the internal part of the Sesia Zone, Western Alps, Italy: Contributions to Mineralogy and Petrology, v. 92, p. 456–470.
Turco, E., Duranti, B., Iaccarino, S., and Villa, G., 1994, Relationship between
foramminiferal biofacies and lithofacies in the Oligocene Molare Formation and Rigoroso Marls: preliminary results from the Piota river section
(Tertiary Piedmont Basin, NW Italy): Giornale di Geologia, v. 56(3),
no. 2, p. 101–116.
Vance, J.A., 1999, Zircon fission track evidence for a Jurassic (Tethyan)
thermal event in the Western Alps: Memorie di Scienze Geologiche di
Padova, v. 51, no. 2, p. 473–476.
Vannucci, G., Piazza, M., Pastorino P., and Fravega, P., 1997, Le facies a coralli
coloniali e rodoficee calcaree di alcune sezioni basali della Formazione di
Molare (Oligocene del Bacino Terziario del Piemonte, Italia Nord–occidentale): Atti Società Toscana, Scienze Naturali, Memorie, v. 104, no. A,
p. 13–39.
Vanossi, M., Cortesogno, L., Galbiati, G., Messiga, B., Piccardo, G., and
Vannucci, R., 1984, Geologia delle Alpi Liguri: Dati, problemi, ipotesi:
Memoria della Società Geologica Italiana, v. 28, p. 5–57.
von Blanckenburg, F., Villa, I.M., Baur, H., Morteani, G., and Steiger, R.H.,
1989, Time calibration of a P-T–path from the Western Tauern Window,
Eastern Alps: The problem of closure temperatures: Contributions to Mineralogy and Petrology, v. 101, p. 1–11.
von Eynatten, H., and Wijbrans, J., 2002, Precise tracing of exhumation and
provenance using 40Ar/39Ar geochronology of detrital white mica: the
example of the Central Alps, in McCann, T., ed., Tracing tectonic deformation using the sedimentary record: London, UK, Geological Society
[London] Special Publication 208, 289–305.
White, N.M., Pringle, M., Garzanti, E., Bickle, M., Najman, Y., Chapman, H.,
and Friend, P., 2002, Constraints on the exhumation and erosion of the
High Himalayan Slab, NW India, from foreland basin deposits: Earth and
Planetary Science Letters, v. 195, no. 1–2, p. 29–44.
Wijbrans, J., Pringle, M.S., Koppers, A.A.P., and Scheveers, R., 1995, Argon
geochronology of small samples using the Vulkaan argon laserprobe:
Proceedings Koninklijke Nederland Akademie van Wetenschappen, v. 98,
no. 2, p. 185–218.
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