Upper Carboniferous to Lower Permian continental deposits in Sardinia (Italy)

4 Pages·1997·1.2 MB·English

by  Ausonio Ronchi

Upper Carboniferous to Lower Permian
continental deposits in Sardinia (Italy)
Giuseppe CASSINIS & Ausonio RONCHI
Dipartimento di Scienze délia Terra,
Via Abbiategrasso 217, 27100 Pavia (Italy)
Cassinis G. & Ronchi A. 1997. — Upper Carboniferous to Lower Permian continental
deposits in Sardinia (Italy), /n Crasquin-Soleau S. & De Wever P. (eds), Peri-Tethys: strati¬
graphie corrélations, Geodiversitas 19 (2) : 217-220.
ABSTRACT
The paper is a brief outline on the sedimentary and volcanic continental suc¬
cessions ot a number of Sardinian basins, which hâve been attributed to
KEY WORDS
Permian and, locally, also to Late Carboniferous rimes. In general this (late)-
continental basins,
sedimentary deposits, postHercynian picture is similar, in most aspects, to the situation in nearby
igneous products, Corsica, and is also reminescent of conditions in South France and Spain,
Upper Carboniferous,
with which Sardinia and Corsica were linked before beginning their drift
Lower Permian,
Sardinia. toward the Tyrrhenian.
RESUME
Cette note est un aperçu des successions sédimentaires et de volcanisme
continental dans les bassins de Sardaigne qui ont été attribués au Permien et,
MOTS CLÉS
localement, au Carbonifère supérieur. En général, cette photographie du
bassin.s continentaux,
depots sédimentaires, (tardi)-posthercynien esc similaire dans la plupart de ses aspects à la situation
produits ignés, de la Corse voisine et évoque aussi ce que l’on connaît en France méridionale
Carbonifère supérieur,
Permien inférieur, et en Espagne, avec lesquelles la Sardaigne et la Corse étaient liées avant leur
Sardaigne. séparation vers la Tyrrhénienne.
GEODIVERSITAS • 1997 • 19(2) 217
Cassinis G. & Ronchi A.
After rhc fïercynian orogeny, during l.ate occurred under a tensional régime after rapid
Carboniferouü and Early Permian times, a large- régional uplift, contain leucogranites (Ghezzo &
scale calcalkaline magmatisrn took place on the Orsini 1982; Carmignani et nL 1989).
island (Fig. 1). The intrusive sequence gave rise The (late)-postHercynian terrigenous and volca-
to hundred-s of plutons over a period of more nic sequence lies unconformably on a heteroge-
than 25 Ma, from at leasr 310 Ma ro about neous, generally tectonized metarnorphic
280 Ma 'l'his plutotiic compicx forms the South¬ hascmcnc. As in many parcs of Permo-
ern part (about 6000 km^) of tbc Sardinian- C'arboniferous continental Europe, it is made up
Corsican bailiolith, which, tn Sardlnia, largdy both of fluvial to laciistrine clastic deposits,
comprises tonalités to tonaJitic granodiorites and which accumulated within more or less subsiding
younger monzogranitic granodiorites to leuco- fauU-bounded basins, and of wider volcanic pro-
monzogranites. Post-tectonic plutons, which ducts, which are generally acidic to intermédiare
in composition.
At présent, the San Giorgio Basin in [glesiente
(SW Sardinia) appears to be the oldesT Upper
Palacozoic sedimentary outerop on the island
(Fig. 2). Its upper dctrital deposits, on the basis
of tossil macroflora vvith Pecopieris, Calamites^
Nenwpieris, Corduiles^ etc. (Coeozza 1967), and
of palynoflora which yields Calanmpom pallida^
SASSARI Florirntvs parims^ etc. (Del Rio 1973), bave-been
identified as belonging to the Upper Srcpbanlan.
More reccntly, howeveu in the lowcrmost layers,
rhc discovery of cccrapod fbotprints, which hâve
been referred to ihe genus Salichnium (already
recorded from the Wesiphalian of Central
nuorq,
Europe and Nonh Africa) and ihus attribuicd to
microsaurs, has encouraged the hyporhesis that
the sédimentation may hâve begun in the San
IRISTANO
Giorgio Basin in former cimes (Fondi 1980).
On the other hand, during rhc Early Permian, a
certain number of well-developed basins (Mt. Lu
Caparoni in Nurra, Seui-Seulo in Barbagia,
Perdasdefogu in Üglfasrra, Escalaplano in Cierrei,
Lake Mulargia in Sarcldano, Guardia J^isano in
Sulcis) occurred on the island. Phey were charac-
terized by rhe above-mentioned (laie)-
CAGLtARI
postHcrc)mian succession (Fig. 2), during which
volcanic products (tuffs, ignimbrircs, lavas and
other igneous exirusive aspects) played an impor¬
tant rôle, and were widespread over exrernal areas.
These continental deposits, which range in
0 _ÿKm
thickness from a dozen to some hundreds of
UPPER CARBONJFEKOUS-PERMIAN
métrés, are normally rich in Aiuunian plants,
CONTINENTAL SEDIMENTS AND VOLCANICS
sLich as Anmniax Odontopteris^ Pecopterisy
VARiSCAN PLinONlC COMPLEX
Anniilarîti^ Ernestodendriou^ Iheniopteris^
Sphenopteris, Corduites^ etc. (Novaresc 1917;
Fig.1 . — Location map of the stratigraphie columns drawn up in Oosterbaan 1936; Maxia 1938; Comaschi Caria
Fig. 2. 1, Pta Lu Caparoni; 2, Perdasdefogu; 3, Escalaplano; 4,
San Giorgio. 1959; Pccorini 1962, 1974; Gasperi & Gelmini
218 GEODIVERSITAS • 1997 • 19(2)
U. Carboniferous and Permian continental deposits in Sardinia
I—1325
1;, ,,j ^ irZ-j |T 11 11 crosion and/or StÜIMHNTARY STRUCTURES biolurbation
min dqKsilion
1.,,! un<iiflerc«n«edc*lcilkllinc •• sandsloncs —vyç- croai'mvl «utriicc large scaJe ao» stratification ^ slunipitig 1
. smalIscalecrrautiTaiiticahnn FOSSILCONlENf
(« ritifiln)
•i»uu.utfo»miiy plants
paraRel straliHcalion ^ palynofloras
j* "lahaf deposils* l'®’-®*! t^bonale nodules ahalcs, mudalones LNVlRONMfcNl lominatinn iCl fish leeth and scales
cherts (_>s . ! dolostones I*", “al 1t.c c.oefuKainneen-piaal med, channei nsiracods
f; fïne-graiited. , ' paUeosol ^ amphibians
hlacustrinc)
^ fooipnnt»
Fig. 2. — Some Upper Palaeozoic sedimentary and volcanic successions of Sardinia. Vertical distances not time or thickness-re(a-
ted. Géologie lime scalefrom Odin & Odin (1990).
1980; Francavilla (• ta/ ,1977i Broutin pers. bably .scals a gap of different, but still uncertain
comm.) and sporomorphs, such as Potoniehpo- magnitude.. Morcover rhe radiometric age-dating
rites novicus. P. hharadwaj, Latensina triletay from a large number of Permian volcanic rocks
Candîdhpom candida, Cordaithidy Florinites, (Cozzupoli et ai 197L 1984; Del Moro et al.
LimhoîpoYÏtes. etc. in che Guardia Pisano basin 1974; Lombanli et al. 1974; Ldcl et al. 1981)
{Barca rt j/. 1992). produccd unrcliable results.
The temporal distribution of rhe overlying per- From rhe above, Ir follows thaï the (late)-
motriassic, coarsc- ro fine-grained, mainly red, postHcrcynian picture in Sardinia is similar^ in
dctriiic sédiments, as »n rhe Mt. Lu Caparoni niost aspects, to die situation in nearby Corsica,
and Lakc Mulargia basins, is not yet clearly de- and is also remiiiiscent of conditions in Provence
fined. The lower boundary of these clastics pro- (France) and Spain, with which Sardinia and
GEODIVERSITAS • 1997 • 19(2) 219
Cassinis G. & Ronchi A.
Corsica werc united bcforc beginning their drift '‘Permo-Ciarbonifero*’ del bacino dî San Giorgio
roward the Tyrrheniaii. The Lare Carboniferoiis (Iglesience, Sardegna sud occidentale). BaUcuino
délia Società Geolngica ludiana 92: 485-494.
ro Early Permian fault-block landscape may bave
Ldel B., Vlnntigny R. îk TKui/.ai R. 1981. — l ate
been formed duiing the rranscurrenr régime,
Paleozoic rotations of C'orsica and Sardinia: New
which is chouglu by many to bave characterized cvidence from paleomagnetic and E-Ar sttidies.
the European Late Paleozoic climax. This régime Tecwfiopbysics 79: 201 -223.
was contemporaneous with the extensional Fondi R. 1980. — Orme di microsauri iiel
Carbonifero superiore délia Sardegna. Memorie
movements linked ro the progressive thinning of
delRt Sfhietà Geologica Jtalinna 30 (1979): 347-356.
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Francavilla F., C^assinis G.. Coco/.za T., Gandin A.,
Gasperi G., Gelmini R., Rau A., Tongiorgi M. &
Vai G.B. 1977. — Macroflora e datazione di alcuni
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Submitted for publication on Î5 April 1996\
accepted on ] October 1996.
220 GEODIVERSITAS • 1997 • 19(2)