GEOLOGICA CARPATHICA, 52, 1, BRATISLAVA, FEBRUARY 2001
15 — 21
PETROGRAPHIC, GEOCHEMICAL AND RADIOMETRIC DATA
ON TERTIARY VOLCANO-ARENITIC BEDS
FROM THE SICILIAN MAGHREBIAN CHAIN:
VOLCANIC SOURCES AND GEODYNAMIC IMPLICATIONS
KADOSA BALOGH
1
, PAOLA CASSOLA
2
, MASSIMO POMPILIO
3
and DIEGO PUGLISI
2*
1
Institute of Nuclear Research, Bem tér 18/c, Debrecen H-4001, Hungary; balogh@moon.atomki.hu
2
Dipartimento di Scienze Geologiche, Università di Catania, Corso Italia 55, 95129-Catania, Italy
3
Istituto Internazionale di Vulcanologia, C. N. R., Piazza Roma 2, 95123-Catania, Italy; max@iiv.ct.cnr.it
(Manuscript received June 2, 2000; accepted in revised form December 12, 2000)
Abstract: The volcanic fraction of impure volcano-arenitic beds of the Reitano Flysch (Early Oligocene, Sicilian
Maghrebian Chain) was investigated by petrographic, geochemical and radiometric techniques. Two distinct volcanic
grain populations were recognized: (1) paleovolcanic clasts, Late-Permian in age and calc-alkaline in character, prob-
ably linked to late-Hercynian magmatism and (2) alkaline (potassic) neovolcanic clasts. As regards the alkaline fraction,
it is difficult to link its provenance with the Oligocene-Miocene Sardinia volcanism. Indeed, this latter volcanism shows
a distinct calc-alkaline character typical of subduction and/or collision-related magmas. We suggest that the volcanic
sources of this alkaline fraction could be related to magmatic events close to the sedimentary basin and associated with
extensional processes preluding the opening of new oceanic areas (i.e. Algero-Provençal Basin and Sardinia Rift).
Key words: Sicilian Maghrebian Chain, Reitano Flysch, Oligocene, volcanogenic sediments, petrography, geochemistry,
K/Ar dating.
Introduction and objectives
The Alpine orogenic system that borders the western Medi-
terranean area includes Tertiary sedimentary rock piles with
very widespread, and locally thick, volcanogenic sediments
interbedded with Tertiary marine formations (Fig. 1).
Volcanogenic levels have been found within many Oli-
gocene-Miocene successions of the Betic Cordillera (Martin-
Algarra 1987; Puglisi & Carmisciano 1992), of the Rifian
sector of Morocco (Feinberg et al. 1990; Chiocchini et al.
1980) and of the Algerian-Tunisian sector (Bellon 1976; Riv-
ière 1988). As regards the northern Apennines, volcanogenic
sediments have been studied in the internal sector (Amorosi
et al. 1994, 1995; Mattioli 1997) as well as in the external
sector (Papini & Vannucci 1993; Delle Rose et al. 1994) and
in the Piemonte Tertiary Basin (Tateo 1993; Bonci et al.
1994; Ruffini & Cadoppi 1994).
The southern Apennines and the Calabria-Peloritani Arc
also show excellent examples of Oligocene-Miocene flysch
deposits affected by volcanic supply (Critelli & Monaco
1993; Critelli 1991; Critelli & Le Pera 1990; Crisci et al.
1988; Cavazza 1989). The calc-alkaline Oligocene-Miocene
Sardinia volcanism has often been invoked to have fed these
volcanoclastic deposits. The origin of these deposits, in fact,
has been traditionally referred to Early Tertiary magmatic
events of western Sardinia, linked to subduction of the Afri-
can lithosphere beneath Europe, considering the counter-
clockwise rotation of the Corsica-Sardinia microplate (Scan-
done 1980; Patacca & Scandone 1989).
Volcanic detritus is also present in the Oligocene-Miocene
turbiditic sedimentary rocks of the outermost sectors of the Si-
cilian Maghrebian Chain. The Reitano Flysch, a thick turbidit-
ic succession of Early Oligocene age overlying the Africa-
verging tectonic units in the easternmost segment of the
Sicilian Maghrebian Chain (Nebrodi Mountains sector,
Fig. 2), and the well known Tusa Tuffites are characterized by
abundant neovolcanic detritus (sensu Zuffa 1987), thus provid-
ing evidence of a volcanism coeval with sedimentation.
In this study we focus our attention on the petrographic,
geochemical and textural characters of the volcanic fraction of
the Reitano Flysch in order (i) to identify the volcanic source
areas and the mechanisms of sedimentary transport and (ii) to
constrain an Oligocene-Miocene geodynamic reconstruction.
In particular, the Reitano Flysch can be correlated with other
turbiditic sequences cropping out in the Betic Cordillera (Al-
geciras Flysch) and along the Maghrebian Chain in northern
Africa (Beni Ider Flysch and Flysch marno-gréso-micacé, in
Morocco and Algeria, respectively). As indicated by the oc-
currence of volcanic clasts and of clinopyroxenes characteriz-
ing the heavy mineral assemblages, the composition of these
turbiditic successions is similar (Puglisi & Carmisciano 1992).
Thus, if the above assumed correlation is valid, the results of
this study could provide useful information about the Early
Tertiary kinematic evolution of the western Mediterranean
*Corresponding author: dpuglisi@mbox.unict.it
16 BALOGH et al.
area by studying the relationships between volcanism and sed-
imentation.
Petrographic and geochemical characters
of the volcanic detritus
The basal and middle levels of the southern outcrops of the
Reitano Flysch (Puglisi 1979; Loiacono & Puglisi 1983) are
made up of impure volcano-arenitic beds (sensu Zuffa 1987),
where a locally abundant volcanic fraction (max 30—35 %) is
mixed with quartzose-feldspathic detritus. This quartzose-
feldspathic detritus, which is predominant at the top of the suc-
cession, is related to a provenance from the Hercynian crystal-
line rocks now deformed into the Peloritani Mountains
tectonic edifice (Cassola et al. 1992, 1995; Costa et al. 1992;
Puglisi 1992).
Petrographic and geochemical characters of the Reitano Fly-
sch sandstones (henceforth RF), taken from the literature, are
shown in Table 1. The Table also includes the discriminating pa-
rameters [(Fe
2
O
3tot
+ MgO), TiO
2
, (Al
2
O
3
/SiO
2
), (K
2
O/Na
2
O)
and Al
2
O
3
/(CaO + Na
2
O)] suggested by Bathia (1983) for in-
terpreting the provenance and tectonic setting of the sedimen-
Fig. 1. Tectonic scheme of the western Mediterranean area. European Units: 1 = Spanish and European Foreland (including “a” Iberian
Cordillera), 2 = Units of the Spanish—European palaeomargin deformed during the Alpine orogeny (Pyrenees, Provençal Chain and Alps), 3
= Kabylo-Calabride Chain (including the internal units of the Betic Cordillera). African Units: 4 = African Forelands (a = gently deformed:
Atlas and Trapanese area; b = undeformed: Pelagian Block, Hyblean Plateau and Apulian Platform), 5 = Units of the African paleomargin
deformed during the Alpine orogeny (Southalpine), 6 = African Units deformed during the Apenninic-Maghrebian orogeny (Apennines, Si-
cilian Maghrebian Chain, Rif, Tell and Betic Cordillera). 7—10 = Pennidic, South-Alpine, Kabylo-Calabride Chain and Apenninic-Maghrebi-
an Chain fronts; 11 = main outcrops of Tertiary volcanogenic sediments along the Betic Cordillera and the Apenninic-Maghrebian Chain.
Fig. 2. Geological sketch map of North-Eastern Sicily with Reit-
ano Flysch outcrops (taken from Puglisi 1992). 1 = External Units;
2 = Numidian Flysch; 3 = Sicilide Units s.s. and Tusa Tuffites; 4 =
Monte Soro Flysch; 5 = Reitano Flysch; 6 = Calabride Units; 7 =
Stilo-Capo d’Orlando Formation; 8 = Antisicilide units; 9 = Qua-
ternary deposits; 10 = Monte Etna volcanites.
TERTIARY VOLCANO-ARENITES IN SICILY: PETROGRAPHY, AGE AND PROVENANCE
17
tary basins. By using both Bathia’s model (1983) and Roser &
Korsch’s (1986) simple bivariate plot [(K
2
O/Na
2
O) vs. SiO
2
],
the Reitano Flysch succession seems to have been deposited
inside a sedimentary basin connected with active continental
margins (Puglisi 1994).
In order to define the petrographic and geochemical charac-
teristics of the volcanic detritus, samples of RF sandstones
were collected from several channeled conglomerate and
coarse-grained sandstone basal levels in the outcrops of Troina
and Lago d’Ancipa (southern slope of the Nebrodi Mountains)
and of Cefalù (Tyrrhenian coast of Sicily, Fig. 2). The petro-
graphic analysis indicates the presence of two distinct volcanic
grain populations with different sizes and features:
A – well-rounded volcanic pebbles (about 1—2 cm in
size) characterized by oligo-porphyritic texture with a low
number of phenocrysts (not more than 7—9 %), ranging in
size from 0.3 to 0.6 mm and mainly represented by sanidine,
plagioclase and quartz, set in a holocrystalline fine-grained
groundmass forming a felt of feldspar and quartz microlites;
B – medium sand-sized (25—50 mm) grains made of angu-
lar and subangular volcanic clasts, scattered in the sandstones,
always associated with quartz and feldspars derived from plu-
tonic and/or middle-high grade metamorphic sources. These
volcanic lithic fragments contain phenocrysts of (i) remark-
ably fresh augitic clinopyroxenes (ii) plagioclase, (iii) rare K-
feldspar and subordinate biotite and amphibole, all of them set
in a micro- to cryptocrystalline groundmass. Clinopyroxenes
are also present as monocrystalline detrital grains.
The chemical compositions of the mineral phases (phe-
nocrysts and microlites, about 245 as total number of analy-
ses for both the A and B volcanic grain populations) and of
the groundmass of the volcanic fraction (84 analyses, 28 and
56 for the A and B populations respectively) have been de-
termined by SEM—EDS methods. Analyses have been per-
formed at the Institute Internazionale di Vulcanologia of
Catania (C.N.R.).
Plagioclase phenocrysts and microlites of both A and B
volcanic grain populations always show an albite composi-
tion
(average composition measured on 140 plagioclase crys-
tals is, by weight: SiO
2
= 68.27 %, Al
2
O
3
= 19.96 %, FeO
tot
= 0.15 %, CaO = 0.33 %, Na
2
O = 11.03 %, K
2
O = 0.26 %).
B-population volcanic clasts shows an abundance of sani-
dine, mainly as microlites rather than phenocrysts (average
composition on 70 sanidine crystals is, by weight: SiO
2
=
64.86 %, Al
2
O
3
= 18.29 %, Na
2
O = 0.45 %, K
2
O = 16.30 %,
SrO = 0.22 %, BaO = 0.14 %), and of clinopyroxenes. Very
few amphiboles were also found and analyzed (SiO
2
= 43.92
%, TiO
2
= 2.39 %, Al
2
O
3
= 10.69 %, FeO
tot
= 14.11 %, MnO
= 0.43 %, MgO = 13.48 %, CaO = 11.56 %, Na
2
O = 2.33 %,
K
2
O = 1.10 %).
Because of the low number of phenocrysts within the A-
population of volcanics, we assume the groundmass compo-
sition as representative of the affinity of the whole rock.
Thus, the two different volcanic grain populations can also
be discriminated by the simple Total Alkali-Silica diagram
(Fig. 3, after Le Maitre 1989), where the average ground-
mass compositions (see Tables 2 and 3) have been plotted.
The groundmass of the two volcanic fractions shows a
strongly variable alkali content, with K
2
O/Na
2
O ratio <1 and
>4 in the pebbles and in the fine-grained detritus, respective-
ly. The groundmass of the fine-grained fraction, in fact,
shows a well marked alkaline (potassic) character with tra-
chytic composition, whereas the groundmass of the volcanic
pebbles shows a subalkaline character with rhyolitic compo-
sition. In addition, the [SiO
2
vs. (FeO
tot
/MgO)] diagram
clearly shows the calc-alkaline affinity of this subalkaline
fraction (Fig. 4).
Clinopyroxenes are only present within the fine-grained
volcanic fraction. Their chemical composition (see Tables 4
and 5) ranges from augite to diopside. As the composition of
the clinopyroxenes vary according to the chemistry of the
Table 1: Petrographic and chemical characters of the Reitano Flysch
sandstones.
Gross Composition
(n = 41)
1
Chemical Composition
(n = 21)
2
x
σ
x
σ
Qm
22.1
5.95
SiO
2
69.58
4.15
Qp
5.3
1.61
TiO
2
0.39
0.07
Qr
3.8
2.59
Al
2
O
3
13.18
0.85
Ch
0.4
0.73
Fe
2
O
3
2.42
0.72
FeO
0.89
0.32
Ps
18.7
2.46
MnO
0.09
0.05
Pr
3.9
2.46
MgO
2.08
0.44
Ks
5.1
3.02
CaO
5.33
4.19
Kr
1.3
1.26
Na
2
O
2.92
0.40
K
2
O
2.95
0.25
Lv
9.2
7.46
P
2
O
5
0.11
0.03
Lc
0.3
0.75
Lf
0.6
1.00
Fe
2
O
3t ot
+MgO
5.51
1.29
Al
2
O
3
/SiO
2
0.19
0.02
Ms
5.6
3.12
K
2
O/Na
2
O
1.03
0.15
Mr
0.7
0.76
Al
2
O
3
/(Na
2
O+CaO)
2.03
0.97
Al
1.1
1.20
lg (Fe
2
O
3t ot
/K
2
O)
0.05
0.15
Mt
4.6
3.28
lg (SiO
2
/Al
2
O
3
)
0.72
0.04
Cm
17.3
10.24
lg (Na
2
O/K
2
O)
-0.01
0.04
100.0
Q
44.7
6.76
F
41.0
6.98
L
14.3
10.11
100.0
Qm
36.6
6.30
F
41.0
6.98
Lt
22.4
9.15
100.0
Gross compositions: symbols of the parameters adopted for modal
analysis
Q = Qm + Qp, where: Q = total quartzose grains, Qm = monocrystalline
quartzose grains (including Qr = quartz in coarse-grained rock fragments,
i.e. >0.06 mm), Qp = polycrystalline quartzose grains (including Ch =
chert);
F = P + K, where: F = total feldspar grains, P and K = plagioclase and
potassium feldspar single grains (Ps and Ks) or in coarse-grained rock
fragments (Pr and Kr);
L = Lv + Lc + Lf, where: L = unstable fine-grained rock fragments (< 0.06
mm, i.e.: Lv = volcanic, Lc = carbonate and Lf = epimetamorphic lithic
fragments);
Lt = L + Qp, where: Lt = total lithic fragments (both unstable and quartzose);
M = micas and chlorites in single grains or in coarse-grained rock fragments
(Ms and Mr, respectively);
Al = other mineral grains, Mt = siliciclastic matrix, Cm = carbonate cement.
1
after Puglisi (1979), Loiacono & Puglisi
(1982), Cassola et al. (1992; 1995)
2
oxide compositions re-calculated on the
volatile-free basis (after Puglisi, 1994);
x e
σ = average and standard deviation,
n = number of analyzed samples.
18 BALOGH et al.
host magma, it can be used to identify the original magmatic
affinity. Thus, the chemical composition of the analyzed cli-
nopyroxenes (about 30 analyses of single detrital grains and
of phenocrysts) are plotted in the diagram suggested by Le-
terrier et al. (1982), discriminating the alkaline/subalkaline
affinities of volcanic rocks (Fig. 5). The alkaline character of
the fine-grained volcanic fraction is also supported by means
of this diagram.
Samples
SiO
2
Al
2
O
3
FeO
tot
MgO CaO Na
2
O K
2
O BaO P
2
O
5
1 (6) x 62.53 21.77 0.99 0.31 0.10
3.45 10.49
- 0.35 100.00
σ
1.50
0.90 0.77 0.25 0.11
0.85
0.88
- 0.18
2 (7) x 60.91 21.65 0.99 0.57 0.42
1.12 13.79 0.30 0.25 100.00
σ
4.42
3.31 1.30 0.50 0.64
0.84
2.93 0.40 0.31
3 (4) x 63.91 19.93 0.41 0.17 0.04
2.43 12.53 0.51 0.07 100.00
σ
2.01
2.22 0.42 0.23 0.08
1.40
3.23 0.59 0.14
4 (12) x 63.98 20.49 0.51 0.18 0.07
2.70 11.81 0.21 0.05 100.00
σ
2.15
2.37 0.58 0.22 0.18
1.77
2.25 0.28 0.11
5 (24) x 64.55 20.23 0.57 0.16 0.11
2.44 11.58 0.34 0.02 100.00
σ
4.28
3.60 0.61 0.20 0.25
1.23
2.48 0.33 0.08
6 (3) x 64.96 20.10 0.55 0.21 0.72
4.27
9.27 0.12
- 100.00
σ
0.47
0.56 0.11 0.20 0.43
0.70
1.32 0.21
-
Number of analyzed groundmass within the brackets; x = average;
σ = standard deviation.
Table 3: Groundmass composition of the B-population volcanic
grains (i.e. fine-grained volcanic clasts scattered in the sandstones).
Fig. 4. SiO
2
-FeO
tot
/MgO diagram (after Miyashiro 1974) discrimi-
nating between the calc-alkaline and tholeiitic products. Only the
subalkaline volcanic fraction of the Reitano Flysch is plotted in
this diagram. For explanation of symbols see Fig. 3.
Fig. 3. TAS (after Le Maitre 1989, with the Irvine and Baragar’s
curve 1971) showing the average groundmass composition of the
study volcanic fraction. Reitano Flysch:
(
(
(
(
(
A-population volcanic
grains (i.e. volcanic pebbles, average of 28 analyses),
B-popula-
tion volcanic grains (i.e. fine-grained volcanic fraction scattered in
the sandstones, average of 56 analyses); Tusa Tuffites: Sicily
(after Ogniben 1964),
o
southern Apennines (after Ardito et al.
1985); S. Mauro Fm. (southern Apennines, after Crisci et al. 1988):
✜
✜
✜
✜
✜; Val d’Aveto Sandstones and Petrignacola Fm. (northern Apen-
nines, after Mattioli 1997): lavas, ignimbrites.
Samples
SiO
2
Al
2
O
3
FeO
tot
MgO
CaO Na
2
O K
2
O
A (5) x
68.83
19.47
0.05
0.04
0.50 10.00 1.11
100.00
σ
1.95
1.39
0.12
0.09
0.16
0.92 1.02
B (3) x
69.24
19.07
-
0.07
0.78 10.14 0.70
100.00
σ
2.91
2.02
-
0.12
0.14
1.02 1.01
C (2) x
74.53
12.26
4.36
1.80
2.31
3.44 1.30
100.00
σ
1.75
1.63
0.60
0.35
0.57
0.64 0.08
D (7) x
80.83
11.28
0.18
0.03
0.22
4.63 2.83
100.00
σ
1.95
1.14
0.23
0.09
0.20
1.43 1.52
E (6) x
79.93
14.90
1.05
0.32
0.75
7.20 1.85
100.00
σ
8.96
4.74
1.46
0.58
0.77
2.64 0.88
F (5) x
76.83
14.88
0.25
-
0.62
6.26 1.16
100.00
σ
5.65
3.20
0.42
-
0.22
2.61 0.54
Number of analyzed groundmass within the brackets; x = average;
σ = standard deviation.
Table 2: Groundmass composition of the A-population volcanic
grains (i.e. volcanic pebbles).
Fig. 5. Average and standard deviation of clinopyroxene composi-
tions of phenocrysts ( , n = 6) and detrital single grains (
(
(
(
(
(
, n = 9;
o
, n = 7;
+
+
+
+
+
, n = 9); n = number of clinopyroxene grains analyzed
in the different samples.
Ti
Ca+ Na
TERTIARY VOLCANO-ARENITES IN SICILY: PETROGRAPHY, AGE AND PROVENANCE
19
K/Ar dating
Radiometric investigation was only possible for the porphy-
ritic pebbles belonging to the A-population of volcanic frag-
ments. Two pebbles were submitted to analysis in order to ob-
tain the K/Ar ages measured for the whole rocks.
Measurement of K/Ar age was performed in the Institute of
Nuclear Research of the Hungarian Academy of Sciences
(ATOMKI), Debrecen, using the conventional method. The in-
terlaboratory standards Asia 1/65, HD-B1, LP-6 and GL-O as
well as atmospheric Ar were also used for the calibration. De-
tails about instruments, applied methods and results of calibra-
tion have been described elsewhere (Balogh 1985; Odin et al.
1982). Age was calculated with the constants suggested by
Steiger & Jaeger (1977).
The obtained results are summarized in Table 6. The
younger age of 213 ± 8 My (sample A) can be explained by
admitting a loss of radiogenic Ar which frequently occurs in
altered whole rock samples. The measured age of 249 ± 10
My (sample B) agrees with the Permian/Triassic boundary
(245 My, Harland et al. 1990). Since some Ar loss may be as-
sumed even for the sample B, related to the transportation of
the pebble, its real geological age either coincides with the
measured value or it is older.
Discussion and conclusive remarks
The above results show that two distinct volcanic sources
fed the Reitano Flysch.
A calc-alkaline source, Late Permian in age, originates paleo-
volcanic clasts (i.e. non-coeval to the sedimentation, sensu Zuf-
fa 1987), derived by the erosion of ancient volcanics probably
linked to a late-Hercynian magmatism. The other source dis-
plays a well marked alkaline (potassic) affinity and originates
products having textural and petrographic characters (angular
shaped volcanic clasts, presence of well preserved augites and
amphiboles) of a volcanism penecontemporaneous with the sed-
imentation and of a rapid burial after short-lived transports (i.e.
coeval volcanic grains, B-population volcanic grains).
Our results have been compared with the geochemical data
of several turbiditic successions cropping out in the southern
and northern Apennines, showing a similar volcanism-induced
sedimentation coeval to the deposition of the Reitano Flysch
(Fig. 3). The volcanic fraction of these latter deposits always
shows a calc-alkaline affinity, commonly interpreted as de-
rived from the Oligocene-Miocene, subduction-related, mag-
matic arc of the Sardinia-Corsica microplate (Crisci et al.
1988; Critelli et al. 1990a,b). Nevertheless, this hypothesis of
provenance can undoubtedly be excluded for the calc-alkaline
volcanic pebbles of the Reitano Flysch (A-population), be-
cause of their older K/Ar age (minimum age is about 249 ± 10
My, i.e. Late Permian).
At first sight, the fine-grained alkaline volcanic clasts of the
Reitano Flysch (B-population volcanic grains) could be relat-
ed to the Late Paleocene-Early Eocene volcanic activity, re-
sponsible for the alkaline products of South-Western Sardinia
(about 62—60 My, Assorgia et al. 1992). These last products, in
fact, are the only Early Tertiary volcanics of Sardinia showing
an alkaline character. Nevertheless, the petrographic and
geochemical features of these Early Tertiary volcanics of Sar-
dinia (SiO
2
~ 39 %, MgO ~ 12 % and K
2
O ~ 1.52 %, Maccioni
et al. 1990) are very different from those of the analyzed
clasts. Moreover, this hypothetical correlation is also in con-
trast with the textural characters recognized in the alkaline
fraction of the Reitano Flysch which testify for volcanic
events coeval with deposition.
Alkaline volcanism in Sardinia also occurred during
Pliocene Tyrrhenian spreading (Beccaluva et al. 1977), but it
cannot be compared with the alkaline volcanic B-population
of the Reitano Flysch sandstones, whose age has recently been
referred to the Early Oligocene (Cassola et al. 1992).
Samples
SiO
2
TiO
2
Al
2
O
3
FeO
tot
MnO MgO CaO Na
2
O
2 (9) x
52.39
0.23 1.57 9.54
0.67 13.41 21.60 0.59
100.00
σ
0.24
0.25 0.23 0.68
0.13 1.03 0.99 0.23
3 (9) x
51.19
0.58 2.48 9.77
0.51 13.08 21.67 0.72 100.000
σ
1.26
0.25 1.15 1.34
0.13 1.51 1.07 0.28
5 (7) x
51.35
0.56 2.36 9.14
0.50 13.20 22.26 0.63
100.00
σ
0.60
0.15 0.94 1.04
0.28 1.34 1.01 0.26
5 (6)* x
51.49
0.42 2.56 8.17
0.39 13.62 22.84 0.51
100.00
σ
1.60
0.35 1.27 1.50
0.25 1.35 0.82 0.20
Table 4: Chemical composition of clinopyroxene detrital grains
and phenocrysts (B-population volcanic grains).
Number of analyzed clinopyroxenes within the brackets; x = average;
σ = standard
deviation; asterisk marks the analyzed clinopyroxenes representing the phenocrysts
of volcanic clasts.
Chemical composition
N° of ions on the basis of 6 oxygens
Samples
2
3
5
5*
Samples
2
3
5
5*
SiO
2
52.46 52.04 51.68 48.66 Si
1.944
1.950 1.940 1.819
TiO
2
0.40
0.23 0.47
0.91 Al
IV
0.056
0.050 0.060 0.181
Al
2
O
3
1.75
1.50 1.80
5.08 Σ T Site 2.000
2.000 2.000 2.000
FeO
tot
9.84
7.68 9.40
8.85 Al
VI
0.020
0.016 0.020 0.043
MnO
0.55
0.56 0.71
0.28 Fe
3+
0.036
0.072 0.061 0.119
MgO
14.99 13.71 12.33 11.97 Ti
0.011
0.006 0.013 0.026
CaO
20.06 22.47 22.67 23.61 Mg
0.828
0.766 0.690 0.667
Na
2
O
0.31
0.70 0.65
0.45 Fe
2+
0.269
0.169 0.234 0.158
Total
100.36 98.89 99.72 99.81 Mn
0.017
0.018 0.023 0.009
Σ M
1
Site 1.181
1.047 1.041 1.022
Ca
0.796
0.902 0.912 0.946
Na
0.022
0.051 0.047 0.033
Σ M
2
Site 0.818
0.953 0.959 0.979
Ca % 40.91
46.83 47.50 49.82
Mg % 42.54
39.76 35.95 35.14
Fe % 16.55
13.41 16.55 15.04
Table 5: Selected analyses of clinopyroxenes (detrital and phe-
nocrysts*) from the B-population volcanic grains.
Samples
(whole rock)
K %
40 Ar (rad)
10
-5
cc STP/g
40 Ar (rad)
%
Age
(My ±
σ)
A
3.68
3.241
93.1
213 ± 8
B
2.85
2.959
94.5
249 ± 10
Table 6: K/Ar ages of two volcanic pebbles from the A-population
volcanic grains.
20 BALOGH et al.
Traversa G. 1989: Cainozoic tectono-magmatic evolution and
inferred mantle sources in the Sardo-Tyrrhenian area. In: Bori-
ani A., Bonafede M., Piccardo G.B. & Vai G.B. (Eds.): The
Lithosphere in Italy. Accademia Nazionale dei Lincei, CNR,
Roma, 229—248.
Beccaluva L., Deriu M., Macciotta G., Savelli C. & Venturelli G.
1977: Geochronology and magmatic character of the
Pliocene-Pleistocene volcanism in Sardinia (Italy). Bull. Vol-
canol. 40, 1—16.
Bellon H. 1976: Séries magmatiques néogènes et quaternaires du
pourtout de la Méditerranée occidentale, comparées dans leur
cadre géologique. Implications géodynamiques. Unpubl. doc-
toral dissertation, Univ. Paris Sud, Orsay, 367.
Bonci M.C., Cortesogno L., Gaggero L., Negri A. & Pirini Radriz-
zani C. 1994: Preliminary data on the Oligo-Miocene volcan-
ism in the Garbagna area (Al F. Voghera). Atti Ticinensi di
Scienze della Terra I, 283—296.
Carmignani L., Decandia F.A., Disperati L., Fantozzi P.L., Lazzarot-
to A., Liotta D., Oggiano G. & Tavarnelli E. 1995: Relazioni
tra il Bacino Balearico, il Tirreno settentrionale e l’evoluzione
neogenica dell’Appennino settentrionale. Stud. Geol. Camerti,
Vol. Spec. 1995/1, 255—278.
Cassola P., Costa E., Loiacono F., Moretti E., Morlotti E., Puglisi D.
& Villa G. 1992. New biostratigraphic, petrographic, sedimen-
tologic and structural data on some “late-orogenic” sequences
of Maghrebian Chain in North-Eastern Sicily. Riv. Ital. Pale-
ont. Stratigr. 98, 2, 205—228.
Cassola P., Loiacono F., Moretti E., Nigro F., Puglisi D. & Sbarra R.
1995: The Reitano Flysch in the northern sector of the Nebrodi
Mountains (NE Sicily): sedimentologic, petrographic and
structural characters. G. Geol. 57, 1-2, 195—217.
Cavazza W. 1989: Detrital modes and provenance of the Stilo-Capo
d’Orlando Formation (Miocene), southern Italy. Sedimentology
36, 1077—1090.
Cherchi A. & Montadert L. 1982a: Oligo-Miocene rift of Sardinia
and the early history of the Western Mediterranean Basin. Na-
ture
298, 736—739,
Cherchi A. & Montadert L. 1982b: Il sistema di rifting oligo-mioce-
nico del Mediterraneo occidentale e sue conseguenze paleo-
geografiche sul Terziario sardo. Mem. Soc. Geol. Ital. 24,
387—400.
Chiocchini U., Franchi R., Guerrera F., Ryan W.B.F. & Vannucci S.
1980: Geologia di alcune successioni torbiditiche cretaceo-ter-
ziarie appartenenti ai “Flysch Maurétaniens” e alla “Nappe Nu-
midienne” del Rif settentrionale (Marocco). Stud. Geol.
Camerti 4, 37—66.
Costa E., Loiacono F., Moretti E., Morlotti E., Puglisi D., Villa G.,
Cassola P. & Sbarra R., 1992: Stratigrafia, caratteri di facies,
petrografia e caratterizzazione strutturale del Flysch di Reitano
(Oligocene inferiore, Sicilia NE). Guida all’escursione. Notiz-
iario Gruppo Informale Sedimentologia del C.N.R., n. 10, Sup-
pl. al Vol. 54 (1) (1992), G. Geol. 1—21.
Crisci G.M., Critelli S. & De Rosa R. 1988: Vulcanismo sinsedi-
mentario nella successione terrigena della formazione di San
Mauro (Miocene inferiore, Unità del Cilento), Appennino me-
ridionale. Mineral. Petrogr. Acta 31, 159—178.
Critelli S. 1991: Evoluzione delle mode detritiche delle successioni
arenitiche terziarie dell’Appennino meridionale. Mem. Soc.
Geol. Ital. 47, 55—93.
Critelli S., De Rosa R. & Sonnino M. 1990a: Le Tufiti di Tusa (Mi-
ocene inferiore): un esempio di sedimentazione vulcanoclasti-
ca in Appennino meridionale. Notiziario Gruppo Informale
Sedimentologia del C. N. R., n. 6, Suppl. al Vol. 51 (2) (1990),
G. Geol. 65—70.
Critelli S., De Rosa R., Sonnino M. & Zuffa G.G. 1990b: Significato
dei depositi vulcanoclastici della formazione delle Tufiti di
In conclusion, it seems difficult to relate the provenance of
this alkaline volcanic fraction of the Reitano Flysch to the Oli-
gocene-Miocene Sardinia-Corsica magmatic arcs. The source
of the alkaline volcanism, in fact, may fairly be interpreted as
the result of magmatic events located closely to the sedimenta-
ry basin during extensional processes. Tentatively, the Reitano
Flysch could have a provenance similar to that already sug-
gested for the Early Oligocene volcano-sedimentary beds from
the Tertiary Piedmont Basin (D’Atri & Tateo 1994). In this
way we would consider the deposition of the Reitano Flysch
as coeval to the incipient break-up of the southern paleomargin
of the European plate, which at that time included the Hercyn-
ian basement of the presently deformed Calabria-Peloritani
Arc. This rifting phase widely affected the western Mediterra-
nean region from the Rupelian-Chattian boundary (Cherchi &
Montadert 1982a,b; Fanucci & Morelli 1995, 1997), preluding
the opening of new oceanic areas (i.e. Algero-Provençal Basin
and Sardinian Rift, Kezirian et al. 1994; Carmignani et al.
1995) and the translation and counterclockwise rotation move-
ments of the Sardinia-Corsica microplate during Oligocene—
Miocene times (Beccaluva 1989; Patacca & Scandone 1989).
Therefore, the geodynamic significance of the alkaline neovol-
canic fraction of the Reitano Flysch may be linked to these
processes of tearing and thinning of the European continental
crust occurred during Oligocene times. Successively to this
process of early continental rifting and together with the drift-
ing of the Sardinia-Corsica microplate, other volcanic events,
calc-alkaline in nature, are commonly recorded within the Late
Oligocene-Miocene successions widespread along the south-
ern and northern Apennines as well as in the Sicilian Maghre-
bian Chain (i.e. Tusa Tuffites of Early Miocene age).
Acknowledgments: Financial support provided by the Ital-
ian MURST and by the Hungarian OTKA Foundation (Grant
n. T 014961, related to the K/Ar dating).
References
Amorosi A., Coccioni R. & Tateo F. 1994: The volcaniclastic bodies
in the lower Miocene Bisciaro Formation (Umbria-Marche Ap-
ennines, central Italy). G. Geol. 56, 1, 33—46.
Amorosi A., Ricci Lucci F. & Tateo F. 1995: The Lower Miocene
siliceous zone: a marker in the palaeogeographic evolution of
the northern Apennines. Palaeogeogr. Palaeoclimatol. Palaeo-
ecol. 118, 131—149.
Ardito M.C., Colaluce G., Dazzaro L., Del Gaudio V., Lops B., Mo-
resi M., Piccarreta G. & Rapisardi L. 1985: Le arenarie
dell’Appennino Dauno Osservazioni geologiche, mineralog-
iche e petrografiche. In: Atti 3° Conv. Naz. “Attività estrattiva
dei minerali di II categoria, Bari 1985, 50—53.
Assorgia A., Brotzu P., Callegari E., Fadda A., Lonis R., Ottelli L.,
Ruffini R. & Abrate T. 1992: Carta geologica del distretto vul-
canico cenozoico del Sulcis (Sardegna sud-occidentale). Scala
1:50.000. S.El.Ca., Firenze.
Balogh K. 1985: K/Ar dating of Neogene volcanic activity in Hun-
gary: experimental technique, experiences and methods of
chronologic studies. ATOMKI, Debrecen—Hungary, Rep. D/1,
277—288.
Bhatia M.R. 1983: Plate tectonic and geochemical composition of
sandstones. J. Geol. 91, 611—627.
Beccaluva L., Brotzu P., Macciotta G., Morbidelli L., Serri G. &
TERTIARY VOLCANO-ARENITES IN SICILY: PETROGRAPHY, AGE AND PROVENANCE
21
Tusa (Miocene inferiore, Lucania meridionale). Boll. Soc.
Geol. Ital. 109, 743—762.
Critelli S. & Le Pera E. 1990: Litostratigrafia e composizione della
Formazione di Pollica (Gruppo del Cilento, Appennino meridi-
onale). Boll. Soc. Geol. Ital. 109, 511—536.
Critelli S. & Monaco C. 1993: Depositi vulcanoclastici nell’unità
del flysch Calabro-Lucano (Complesso Liguride, Appennino
meridionale). Boll. Soc. Geol. Ital. 112, 121—132.
D’Atri A. & Tateo F. 1994: Volcano-sedimentary beds of Oligocene
age from the Tertiary Piedmont Basin (NW Italy): biostratigra-
phy and mineralogy. G. Geol. 56, 1, 79—95.
Delle Rose M., Guerrera F., Renzulli A., Ravasz-Baranyai L. & Ser-
rano F. 1994: Stratigrafia e petrografia delle Marne di Vicchio
(Unità tettonica Cervarola) dell’alta Val Tiberina (Appennino
Tosco-Romagnolo). Boll. Soc. Geol. Ital. 113, 675—708.
Fanucci F. & Morelli D. 1995: Modello cinematico di evoluzione
del Mediterraneo nord-occidentale. Stud. Geol. Camerti, Vol.
Spec. 1995/1, 383—390.
Fanucci F. & Morelli D. 1997: Il margine Sardo nel contesto geodi-
namico del Mediterraneo occidentale. In: Convegno-Escur-
sione su La “Fossa Sarda” nell’ambito dell’evoluzione
geodinamica cenozoica del Mediterraneo occidentale. Vill-
anovaforru (Cagliari) 19—22 Giugno 1997, 81—83.
Feinberg H., Maate A., Bouhdadi S., Durand-Delga M., Maate M.,
Magné J. & Olivier Ph. 1990: Signification des dépôts de
l’Oligocène supérieur et du Miocène inférieur du Rif interne
(Maroc) dans l’évolution géodynamique de l’Arc de Gibraltar.
C. R. Acad. Sci. Paris 310, 1487—1495.
Harland W.B., Armstrong R.L., Cox A.V., Craig L.E., Smith A. G. &
Smith D.G. 1990: A Geologic Time Scale 1989. Cambridge
University Press, Cambridge, New York, Port Chester.
Irvine T.N. & Baragar W.R.A. 1971: A guide to the chemical classi-
fication of the common volcanic rocks. Canad. J. Earth Sci. 8,
523—554.
Kezirian F., Barrier P., Bouillin J.P. & Janin M.C. 1994: L’Oligo-
Miocène Péloritain (Sicile): un témoin du rifting du Bassin Al-
géro-Provençal. C.R. Acad. Sci. Paris 319, II, 699—704.
Le Maitre R.W. 1989: A classification of igneous rocks and glossary
of terms. Recommendation of I.U.G.S. subcommission on the
systematics of the igneous rocks. Blackwell Scientific Publica-
tions, Oxford.
Leterrier J., Maury R.C., Thonon P., Girard D. & Marchal M. 1982:
Clinopyroxene composition as a method of identification of the
magmatic affinities of palaeo-volcanic series. Earth Planet.
Sci. Lett. 59, 139—154.
Loiacono F. & Puglisi D. 1983: Studio sedimentologico-petrografi-
co del Flysch di Reitano (Oligocene-Miocene inferiore, Sicil-
ia). Boll. Soc. Geol. Ital. 102, 307—328.
Maccioni L., Marchi M. & Salvadori A. 1990: Eocene alkaline lam-
prophyre in south-western Sardinia (Italy) (new occurrence).
Rendiconti del Seminario della Facolt
à di Scienze dell’ Uni-
versit
à di Cagliari, 60, 217—231.
Martín Algarra A. 1987: Evolución geologíca alpina del contacto
entre las Zonas Internas y las Zonas Externas de la Cordillera
Bética. Unpubl. doctoral dissertation, Univ. Granada, D. pto
Estratigrafía y Paleontología, 1171.
Mattioli M. 1997: Vulcanismo terziario nell’Appennino settentrion-
ale: evidenze da clasti andesitici nell’Unità di Canetolo e da
corpi vulcanici sepolti. Unpubl. doctoral dissertation, Univer-
sità di Parma, 144.
Miyashiro A. 1974: Volcanic rocks series in Island arcs and active
continental margins. Amer. J. Sci. 274, 321—335.
Odin G.S. & 35 collaborators 1982: Interlaboratory standards for
dating purposes. In: Odin G.S. (Ed.): Numerical Dating in
Stratigraphy. Wiley & Sons, Chichester, New York, Brisbane,
123—150.
Ogniben L. 1964: Arenarie tipo Taveyannaz in Sicilia. Geol. Roma-
na 3, 125—170.
Papini M. & Vannucci S. 1993: Intercalazioni vulcanoclastiche e sil-
icee nelle arenarie del Cervarola del versante orientale di M.
Giovi (Firenze). G. Geol. 55, 51—69.
Patacca E. & Scandone P. 1989: Post-Tortonian mountain building
in the Apennines. The role of the passive sinking of a relic
lithosphere slab. In: Boriani A., Bonafede M., Piccardo G.B. &
Vai G.B. (Eds.): The Lithosphere in Italy. Accademia Nazion-
ale dei Lincei, CNR, Roma, 157—176.
Puglisi D. 1979: Variazioni composizionali nelle arenarie del Flysch
di Reitano (Monti Nebrodi, Sicilia centro-settentrionale). Min-
eral. Petrogr. Acta 23, 13—46.
Puglisi D. 1992: Le successioni torbiditiche “tardorogene” della Si-
cilia orientale. G. Geol. 54/1, 181—194.
Puglisi D. 1994: Caratteri petrochimici delle arenarie delle unità tor-
biditiche oligo-mioceniche della Sicilia nord-orientale. Miner-
al. Petrogr. Acta 37, 393—415.
Puglisi D. & Carmisciano R. 1992: Il Flysch di Algeciras (Oli-
gocene-Miocene inf.?, Cordigliera Betica): studio petrografi-
co-sedimentologico e confronto con altre unità torbiditiche
della catena maghrebide. Boll. Acc. Gioenia Sci. Naturali di
Catania 25, 340, 5—23.
Rivière M. 1988: Sédimentologie et géochimie des formations du
Miocène inférieur des Bétides et des Maghrébides. Implica-
tions paléogéographiques. Unpubl. Doctoral dissertation,
Univ. Paris-Sud, Orsay, 388.
Roser B.P. & Korsch R.J. 1986: Determination of tectonic setting of
sandstone-mudstone suites using SiO
2
content and K
2
O/Na
2
O
ratio. J. Geol. 94, 635—650.
Ruffini R. & Cadoppi P. 1994: Evidence of trachytic and rhyolitic
volcanism in the Miocene succession of Monferrato (NW Ita-
ly). Atti Ticinensi di Scienze della Terra I, 297—311.
Scandone P. 1980: Origin of the Tyrrhenian Sea and Calabrian Arc.
Boll. Soc. Geol. Ital. 98, 27—34.
Steiger R.H. & Jäger E. 1977: Subcommisssion on Geochronology:
convention on the use of decay constants in geo- and cosmo-
chronology. Earth Planet. Sci. Lett. 12, 359—362.
Tateo F. 1993: Intercalazioni vulcano-sedimentarie nella Formazi-
one di Antognola: le sezioni “Rio Nespolo” e “M. Varano”
(Oligocene superiore, Appennino parmense). Mineral. Petrogr.
Acta 36, 61—79.
Zuffa G.G. 1987: Unraveling hinterland and offshore palaeogeogra-
phy from deep-water arenites. In: Legget J.K. & Zuffa G.G.
(Eds.): Deep-marine Clastic Sedimentology: concepts and
Case Study. Graham and Trotman, 39—61.