The discovery of ammonoids at the top of the Cunardo Formation allows the revision of the chronostratigraphic position of the unit. Detoniceras, Argolites and Anolcites testify the Archelaus Zone. The age of the unit is then Ladinian instead of Carnian, as reported in literature

LORENZO CALABRESE

MARCO BALINI

CALABRESE, LORENZO

BALINI, MARCO

Riviste UNIMI

Rivista Italiana di Paleontologia e Stratigrafia volume lul numero 3 pagine 367-370 .lJlcemDre lv7)NOTE BREVITHE DISCOVERY OF AMMONOIDS IN THE CUNARDO FORMATION (VARESE).A NE\Ii CHRONOSTRATIGRAPHIC INTERPRETATIONLORENZO CALABRESE E{ MARCO BALINIKey-zaords: Cunardo Formation, Amnonoids, Ladinian, Car-nian, Southern Alps.Riassunto. La scoperta di Ammoniti al tetto della Formazionedi Cunardo consente la revisione della posizione cronostratigraficadell' unità. Detoniceras, ArgoLites e AnoLcites documenrano la TonaArchelaus. L età della formazione é quindi ladinica e non carnica,come sostenuto in letteratura.Abstract. The discovery of ammonoids àr the top of the Cu-nardo Formation allows the revision of the chronostratigraphic posi-tion of the unit. Detoniceras, Argolites and Anolcites testify the Ar-chelaus Zone. The age of the unit is then Ladinian instead of Car-nian, as reponed in literature.Previous sludies.The Middle and Upper Triassic formations of .we-stern Varese province founded their dating on determi-nations of Anisian-Ladinian fossils ('Ceratites" luganen-sls: Mariani, 1901; Frauenfelder, 1916; Zorn, !971,; "Ce-ratites" felsoresensis Airaghi, 1935) in the San SalvatoreDolomite and Norian fossils (.Isognomon exilis, Neomega-lodon gumbeli, IVhortenia escberi, Gyroporella oesiculife-ra: Frauenfelder, 191,6; De Sitter, 1939) ín the "DolomiaPrincipale".The placing in the time scale of the marls, marlyIimestones, and thin-bedded dolostones, lying betweenthe dated strata (Pizzella Marl and Cunardo Formationby Allasinaz, !968a,1968b and 1968c) relied on geome-trical and lithostratigraphic criteria because of the lackof significant fossils.Most of authors agreed in ascribing marls and mar-ly limestones to the Carnian and particularly to the LateCarnian, because the lithological features and the posi-tion of these strata, below the "Dolomia Principale",connected intuitively this terrigenous-calcareous depositto the typical generalízed Late Carnian sedimentation.In chronostratigraphic reconstructions, most of di-vergences were associated to the dating of the thin-bed-ded dolostones, lying on the San Salvatore Dolomite:Taramelli (1880) thought these layers were passingthrough the Ladinian and the Carnian; most of fol-lowing authors assigned them to the Middle Carnian(Frauenfelder, 1916; Senn, 1924; Bernoulli, 1964; Allasirnz, 1968a and 1968b; Zorn, 197I) and a minority con-sidered that they were a San Salvatore Dolomite's verti-cal facies variation and then an Upper Ladinian deposit(Van Houten,1929; De Sitter, t939) (Fig. t).f---l"Dolomia Principate" f[t'iatu"Qvariegated marls and marly limestones I I "ce.atites" luganensis,(Pizella Marl) Ceratites felsoresensisffi thrn-bedded dolostones(Cunardo Fomation)ffilS Satvatore Dotomite. . Detoniceras, Argolites, Anolcites and?Protrachyceras. . lsognomon exilis, Neomegalodongumbeli, Worthenia escheri, etcFig. 1 - Summary of the chronostratigraphic interpretations of theAnisian-Norian ìnterval in the west of Varese.Rio Cosarivo's fossiliferous horizon.During the geological survey relative to Calabre-se's graduation thesis, a fossiliferous horizon has beenfound out at the top of the Cunardo Formation.The fossiliferous locality is placed in the west ofCassano Valcuvia (Varese), aiong the Rio Cosarivo'snorthern affluent (480-460 m altitude) (Fíg 2a). There,the Pizzella Marl and the Cunardo Formation's strata1880 1926De Stfter I Bemoullt I A|Iasina219391196411968^ 1 971vataDEse - óanntNorianlarnian ruffi"//,/,IIHvtlTUSll-adiniani1!irtri-..!!::: :::: :: : : .: :.: : - : : t : :::: : .:. : i\nisiariiil:i.iiiiiiii f i:ijiiiii.iiirl.jI.i.iii::;i,iiiilli::ii'li i.,j:i jDipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli 34,2A133 Milano, Italy368 L. Calabrese G M. Balinihave got a different lying (Fig. 2b). This different lyingcould be explained as angular unconformity (onlaptype), or as a stratigraphic boundary affected by a lightfaulting. An accurate observation is not possible due tocovering upon the boundary.The Cunardo Formation, in western Varese pro-vince, is about 100 m thick and consists of thin beddedgrey and brown dolosbnes, sometimes laminated andwith marly drapes. Fig. 2c shovzs lithological features ofthe Cunardo Fo rmati o n-P izzella Marl b oundary.From bottom to top the section is as follows:1) flat bedded fine dolostones, white-yellow on weathered surface,grey to brown or hazel brown in fracture; beds are 2 to 5 cmthick with parallel laminations. Layers and laminations sometimesare wavy (wave ripple marks) and there are thin mariy drapes.Beds are thicker on the top (10 cm about) with more irreguhrsurfaces (4 m);light hazel brown to brown dolostones in 1 to 15 cm thick bedswith wavy and much irregular surfaces. There are bioturbations andcavities with millimetric dolomite crystals on the surface (12 m);hazel brown to brown dolostones; layers are 7 to 20 cm thickwith plane-wavy surfaces. Grey to brown dolostones follow in theupper part in 15 to 30 cm thick beds; there is a bed 40 cm thickof dark grey dolostones at the top with black chen nodules andsilicified fossils on the upper surface (8 m). Top of Cunardo Fm.Not exposed: about 3.5 m.calcareous dolostones, dolomitic limestones and limestones, whiteto grey on weathered surface, grey to hazel brown in fracture;layers are lamìnated, flat bedded, 2to 12 cm thick. There are thinmarly drapes between layers; grey to brown limestones follow in 2to 7 cm thick beds, plane-parallel stratified and with thin marlylevels, alternated to larninated layers of marly limestones (tO m).Lower Pizzella Marl.Volcanic Serie andI X:a::l permian and eo-triassicterrigenous depositsffi Cunardo Formationn-fn Pizzella Marla7-1"Dolomia Principate"F-l Mottrasio Limestonef.-77dolostonesWcalcareous dolostones|-_--r -t;-l dolomitic limestonesr;-rll timestonesFlEf, marly limestones2)4)G<' chert nodulesammonoidsFig.2 - a) Geographical location ofthe studied section; b) geolo-gical sketch of Rio Cosarivoarea; c) stratigraphical sec-tion: numbers refer to thelithologic levels described inthe text.GAmmonoi.ds of the Cunardo Formation 369Ammonoids of Rio Cosarivo section. A) Detoniceras sp., x1; B) Argolites sp., flattened specimen, xl; C) Anolcites sp., x1. The fulldescription of the fauna will be done in a fonhcoming paper.The fossiliferous layer is a dolomitic microsparitewith pelagic bivaives (also hinged), bioturbation ftur-rowing), fine shreds of organic matter and local submil-limetric concentrations of phosphatic compound. Authi-genic quartz and feldspars are also present.Fossils are common and mostly consist of ammo-noids. FIowever, bivalves can also be found. All fossilsare flattened and silicified. Usually just the upper surfa-ce of the specimens is preserved, while the lower is in-cluded in chert nodules and overprinted by diagenesis.Among the rich ammonoid fauna the genera DetonicerasManfrin & Mietto, 1991 (Fig. 3A), Argolites Renz, 1939(Fig. 3B), and Anolcites Mojsisovics, 1893 (Fig. 3C) havebeen recognized. Probably Protraclryceras Mojsisovics,1893 is also present, but the identification is uncerraindue to strong flattening of the specimens..Revision of the age of the Cunardo Formation.On the basis of the recognized ammonoids achronostratigraphic classification of the fossil-bearinglevel is possible. The genus Detoniceras s.s. is reportedfrom the Archelaus Zone (early Late Ladinian) by Man-frin & Mietto (1991). More recendy Detoniceras andArgolites have been also recognized in the same intervalby Fantini Sestini (1,994). Anolcites and Protrachycerasare not significant, at least at the level of genus, for amore refined attribution. In the assemblage there areno typical eiements of the Regoledanus Zone (latest La-dinian).In conciusion we may demonsrrate that the Cu-nardo Formation is not Carnian in age, but Ladinian.The problem of the age of the Pizzella Marl is still ope-ned. If we accept that the boundary between the Cunar-do Formation and the Pizzella Marl is represented by anangular unconformity, then the inferred age of the Prz-zella Mari could be Carnian. If the sedimerrtary sequen-ce is continuous the base of the Pizzella Marl is UpperLadinian (?Regoledanu s Zo ne).Acknouledgentents.Proff. M. Gnaccolinr and F. Jadoul, who followed thegraduation thesis of one of the authors (LC) are acknowledged forthe help in the field work and for the fruitful and stimulatingdiscussions. Proff. M. Gaetani and F. Jadoul are acknowledged for therevision of the manuscriot.REFERENCESAllasinaz A. (1968a) - Il Carnico della Lombardia occidentale.Riz,. It. Paleont. Strat., v.74, n.4, pp. 1007-i056, Milano.Allasinaz A. (1968b) - Formazione di Cunardo. Studi lll. Car.ta Geol. d' Italia, Formazioni Geologiche, fasc. I, pp. 65-70, Roma.Allasinaz A. (1968c) - Marna del Pizzella. Studi lll. CartaGeol. d' Italia, Formazioni Geologiche, fasc. I, pp. 71,-76,Roma.Airaghi C. (1935) - I fossili della dolomia triasica della Rasa(Varese). Rend. R. Ist. Lomb. Sc. Lett., v. 68, pp. 1,91,-1,96,Milano.Bernoulli D. (1964) - Zur Geologie des Monte Generoso(Lombardische Alpen). Beit Geol. Karte Schueiz,N.F.,v. 118, pp. l-134,Bern.De Sitter L.U. (1939) - Les porphyres luganais et leurs enve-loppes. L historie géologique des Alpes Tessinoises en-tre Lugano et Varese. Leid. Geol. Med., v. 11, pp. 31.-61,Leiden.Fantini Sestini N. (1994) - The Ladinian ammonoids fromCalcare di Esino of Val Parina (Bergamasc Aips, North-ern Italy). Pr. l. Ria. It. Paleont. Strat., v.1OO, n. 2, pp.227-284, Milano.Frauenfelder A. (1916) - Beitràge zur Geologie der TessinerKalkalpen. EcL Geol. Helv., v. 14, pp. 247-367, Lausan-Leuzinger P. (1926) - Geologische Beschreibung des MonteCampo dei Fiori und der Sedimentzone Luganersee-Val-cuvia. Ecl. Geol. Helo., v. 20, pp.90-157, Basel.Manfrin S. Ec Mietto P. (1991) - Detoniceras nuovo genere diammonoidi triassici dedicato ad Antonio De Toni, nelcentenario deila sua nascita. Mem. Sc. GeoL., v. 43, pp.1.25-135, Padova.370 L. Calabrese & M. BaliniMariani E. (1901) - Su alcuni fossili del Trias medio dei din- Van Flouten I. 0929) - Geologie der Kalkalpen am Ostufertorni di Porto Valtravaglia e sulla fauna della dolomia des Lago Maggiore. Ecl. Geol. Hela., v. 22, pP. 1-40, Ba-del Monte San Salvatore presso Lugano. Atti Soc. It. Sc. sel.Nat., v.40, pp. 3-27, Mìlano. Zorn H. (1971) - Palàontologische, stratigraphische und sedi-Senn A. (1924) - Beitràge zur Geologie des Alpensùdrandes mentologische lJntersuchungen des Salvatoredolomitszwischen Mendrisio und Varese. Ecl. Geol. Helo., v. 18, (Mitteltrias) der Tessiner Kalkalpen. Scbzaeitz. Palàont.pp. 560-632, Basel. Abh., v.91, pp. 3-90, Basel.Taramelli T. (1SS0) - I1 Canton Ticino meridionale e i paesifinitimi. Mat. Carta Geol. Svizzera, s. 1, v. 17, v. oÍ 230oo.- Bern. Receio.ted August 3, 1995; accepted October 4, 1995rr', --""

English

THE DISCOVERY OF AMMONOIDS IN THE CUNARDO FORMATION (VARESE). A NEW CHRONOSTRATIGRAPHIC INTERPRETATION

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Rivista Italiana di Paleontologia e Stratigrafia volume lul numero 3 pagine 367-370 .lJlcemDre lv7)NOTE BREVITHE DISCOVERY OF AMMONOIDS IN THE CUNARDO FORMATION (VARESE).A NE\Ii CHRONOSTRATIGRAPHIC INTERPRETATIONLORENZO CALABRESE E{ MARCO BALINIKey-zaords: Cunardo Formation, Amnonoids, Ladinian, Car-nian, Southern Alps.Riassunto. La scoperta di Ammoniti al tetto della Formazionedi Cunardo consente la revisione della posizione cronostratigraficadell' unità. Detoniceras, ArgoLites e AnoLcites documenrano la TonaArchelaus. L età della formazione é quindi ladinica e non carnica,come sostenuto in letteratura.Abstract. The discovery of ammonoids àr the top of the Cu-nardo Formation allows the revision of the chronostratigraphic posi-tion of the unit. Detoniceras, Argolites and Anolcites testify the Ar-chelaus Zone. The age of the unit is then Ladinian instead of Car-nian, as reponed in literature.Previous sludies.The Middle and Upper Triassic formations of .we-stern Varese province founded their dating on determi-nations of Anisian-Ladinian fossils ('Ceratites" luganen-sls: Mariani, 1901; Frauenfelder, 1916; Zorn, !971,; "Ce-ratites" felsoresensis Airaghi, 1935) in the San SalvatoreDolomite and Norian fossils (.Isognomon exilis, Neomega-lodon gumbeli, IVhortenia escberi, Gyroporella oesiculife-ra: Frauenfelder, 191,6; De Sitter, 1939) ín the "DolomiaPrincipale".The placing in the time scale of the marls, marlyIimestones, and thin-bedded dolostones, lying betweenthe dated strata (Pizzella Marl and Cunardo Formationby Allasinaz, !968a,1968b and 1968c) relied on geome-trical and lithostratigraphic criteria because of the lackof significant fossils.Most of authors agreed in ascribing marls and mar-ly limestones to the Carnian and particularly to the LateCarnian, because the lithological features and the posi-tion of these strata, below the "Dolomia Principale",connected intuitively this terrigenous-calcareous depositto the typical generalízed Late Carnian sedimentation.In chronostratigraphic reconstructions, most of di-vergences were associated to the dating of the thin-bed-ded dolostones, lying on the San Salvatore Dolomite:Taramelli (1880) thought these layers were passingthrough the Ladinian and the Carnian; most of fol-lowing authors assigned them to the Middle Carnian(Frauenfelder, 1916; Senn, 1924; Bernoulli, 1964; Allasirnz, 1968a and 1968b; Zorn, 197I) and a minority con-sidered that they were a San Salvatore Dolomite's verti-cal facies variation and then an Upper Ladinian deposit(Van Houten,1929; De Sitter, t939) (Fig. t).f---l"Dolomia Principate" f[t'iatu"Qvariegated marls and marly limestones I I "ce.atites" luganensis,(Pizella Marl) Ceratites felsoresensisffi thrn-bedded dolostones(Cunardo Fomation)ffilS Satvatore Dotomite. . Detoniceras, Argolites, Anolcites and?Protrachyceras. . lsognomon exilis, Neomegalodongumbeli, Worthenia escheri, etcFig. 1 - Summary of the chronostratigraphic interpretations of theAnisian-Norian ìnterval in the west of Varese.Rio Cosarivo's fossiliferous horizon.During the geological survey relative to Calabre-se's graduation thesis, a fossiliferous horizon has beenfound out at the top of the Cunardo Formation.The fossiliferous locality is placed in the west ofCassano Valcuvia (Varese), aiong the Rio Cosarivo'snorthern affluent (480-460 m altitude) (Fíg 2a). There,the Pizzella Marl and the Cunardo Formation's strata1880 1926De Stfter I Bemoullt I A|Iasina219391196411968^ 1 971vataDEse - óanntNorianlarnian ruffi "//,/,IIHv tlTUSll-adiniani1!irtri-..!!::: :::: :: : : .: :.: : - : : t : :::: : .:. : i\nisiariiil:i.iiiiiiii f i:ijiiiii.iiirl.jI.i.iii::;i,iiiilli::ii'li i.,j:i jDipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli 34,2A133 Milano, Italy368 L. Calabrese G M. Balinihave got a different lying (Fig. 2b). This different lyingcould be explained as angular unconformity (onlaptype), or as a stratigraphic boundary affected by a lightfaulting. An accurate observation is not possible due tocovering upon the boundary.The Cunardo Formation, in western Varese pro-vince, is about 100 m thick and consists of thin beddedgrey and brown dolosbnes, sometimes laminated andwith marly drapes. Fig. 2c shovzs lithological features ofthe Cunardo Fo rmati o n-P izzella Marl b oundary.From bottom to top the section is as follows:1) flat bedded fine dolostones, white-yellow on weathered surface,grey to brown or hazel brown in fracture; beds are 2 to 5 cmthick with parallel laminations. Layers and laminations sometimesare wavy (wave ripple marks) and there are thin mariy drapes.Beds are thicker on the top (10 cm about) with more irreguhrsurfaces (4 m);light hazel brown to brown dolostones in 1 to 15 cm thick bedswith wavy and much irregular surfaces. There are bioturbations andcavities with millimetric dolomite crystals on the surface (12 m);hazel brown to brown dolostones; layers are 7 to 20 cm thickwith plane-wavy surfaces. Grey to brown dolostones follow in theupper part in 15 to 30 cm thick beds; there is a bed 40 cm thickof dark grey dolostones at the top with black chen nodules andsilicified fossils on the upper surface (8 m). Top of Cunardo Fm.Not exposed: about 3.5 m.calcareous dolostones, dolomitic limestones and limestones, whiteto grey on weathered surface, grey to hazel brown in fracture;layers are lamìnated, flat bedded, 2to 12 cm thick. There are thinmarly drapes between layers; grey to brown limestones follow in 2to 7 cm thick beds, plane-parallel stratified and with thin marlylevels, alternated to larninated layers of marly limestones (tO m).Lower Pizzella Marl.Volcanic Serie andI X:a::l permian and eo-triassicterrigenous depositsffi Cunardo Formationn-fn Pizzella Marla7-1"Dolomia Principate"F-l Mottrasio Limestonef.-77dolostonesWcalcareous dolostones|-_--r -t;-l dolomitic limestonesr;-rll timestonesFlEf, marly limestones2)4)G<' chert nodulesammonoidsFig.2 - a) Geographical location ofthe studied section; b) geolo-gical sketch of Rio Cosarivoarea; c) stratigraphical sec-tion: numbers refer to thelithologic levels described inthe text.GAmmonoi.ds of the Cunardo Formation 369Ammonoids of Rio Cosarivo section. A) Detoniceras sp., x1; B) Argolites sp., flattened specimen, xl; C) Anolcites sp., x1. The fulldescription of the fauna will be done in a fonhcoming paper.The fossiliferous layer is a dolomitic microsparitewith pelagic bivaives (also hinged), bioturbation ftur-rowing), fine shreds of organic matter and local submil-limetric concentrations of phosphatic compound. Authi-genic quartz and feldspars are also present.Fossils are common and mostly consist of ammo-noids. FIowever, bivalves can also be found. All fossilsare flattened and silicified. Usually just the upper surfa-ce of the specimens is preserved, while the lower is in-cluded in chert nodules and overprinted by diagenesis.Among the rich ammonoid fauna the genera DetonicerasManfrin & Mietto, 1991 (Fig. 3A), Argolites Renz, 1939(Fig. 3B), and Anolcites Mojsisovics, 1893 (Fig. 3C) havebeen recognized. Probably Protraclryceras Mojsisovics,1893 is also present, but the identification is uncerraindue to strong flattening of the specimens..Revision of the age of the Cunardo Formation.On the basis of the recognized ammonoids achronostratigraphic classification of the fossil-bearinglevel is possible. The genus Detoniceras s.s. is reportedfrom the Archelaus Zone (early Late Ladinian) by Man-frin & Mietto (1991). More recendy Detoniceras andArgolites have been also recognized in the same intervalby Fantini Sestini (1,994). Anolcites and Protrachycerasare not significant, at least at the level of genus, for amore refined attribution. In the assemblage there areno typical eiements of the Regoledanus Zone (latest La-dinian).In conciusion we may demonsrrate that the Cu-nardo Formation is not Carnian in age, but Ladinian.The problem of the age of the Pizzella Marl is still ope-ned. If we accept that the boundary between the Cunar-do Formation and the Pizzella Marl is represented by anangular unconformity, then the inferred age of the Prz-zella Mari could be Carnian. If the sedimerrtary sequen-ce is continuous the base of the Pizzella Marl is UpperLadinian (?Regoledanu s Zo ne).Acknouledgentents.Proff. M. Gnaccolinr and F. Jadoul, who followed thegraduation thesis of one of the authors (LC) are acknowledged forthe help in the field work and for the fruitful and stimulatingdiscussions. Proff. M. Gaetani and F. Jadoul are acknowledged for therevision of the manuscriot.REFERENCESAllasinaz A. (1968a) - Il Carnico della Lombardia occidentale.Riz,. It. Paleont. Strat., v.74, n.4, pp. 1007-i056, Milano.Allasinaz A. (1968b) - Formazione di Cunardo. Studi lll. Car.ta Geol. d' Italia, Formazioni Geologiche, fasc. I, pp. 65-70, Roma.Allasinaz A. (1968c) - Marna del Pizzella. Studi lll. CartaGeol. d' Italia, Formazioni Geologiche, fasc. I, pp. 71,-76,Roma.Airaghi C. (1935) - I fossili della dolomia triasica della Rasa(Varese). Rend. R. Ist. Lomb. Sc. Lett., v. 68, pp. 1,91,-1,96,Milano.Bernoulli D. (1964) - Zur Geologie des Monte Generoso(Lombardische Alpen). Beit Geol. Karte Schueiz,N.F.,v. 118, pp. l-134,Bern.De Sitter L.U. (1939) - Les porphyres luganais et leurs enve-loppes. L historie géologique des Alpes Tessinoises en-tre Lugano et Varese. Leid. Geol. Med., v. 11, pp. 31.-61,Leiden.Fantini Sestini N. (1994) - The Ladinian ammonoids fromCalcare di Esino of Val Parina (Bergamasc Aips, North-ern Italy). Pr. l. Ria. It. Paleont. Strat., v.1OO, n. 2, pp.227-284, Milano.Frauenfelder A. (1916) - Beitràge zur Geologie der TessinerKalkalpen. EcL Geol. Helv., v. 14, pp. 247-367, Lausan-Leuzinger P. (1926) - Geologische Beschreibung des MonteCampo dei Fiori und der Sedimentzone Luganersee-Val-cuvia. Ecl. Geol. Helo., v. 20, pp.90-157, Basel.Manfrin S. Ec Mietto P. (1991) - Detoniceras nuovo genere diammonoidi triassici dedicato ad Antonio De Toni, nelcentenario deila sua nascita. Mem. Sc. GeoL., v. 43, pp.1.25-135, Padova.370 L. Calabrese & M. BaliniMariani E. (1901) - Su alcuni fossili del Trias medio dei din- Van Flouten I. 0929) - Geologie der Kalkalpen am Ostufertorni di Porto Valtravaglia e sulla fauna della dolomia des Lago Maggiore. Ecl. Geol. Hela., v. 22, pP. 1-40, Ba-del Monte San Salvatore presso Lugano. Atti Soc. It. Sc. sel.Nat., v.40, pp. 3-27, Mìlano. Zorn H. (1971) - Palàontologische, stratigraphische und sedi-Senn A. (1924) - Beitràge zur Geologie des Alpensùdrandes mentologische lJntersuchungen des Salvatoredolomitszwischen Mendrisio und Varese. Ecl. Geol. Helo., v. 18, (Mitteltrias) der Tessiner Kalkalpen. Scbzaeitz. Palàont.pp. 560-632, Basel. Abh., v.91, pp. 3-90, Basel.Taramelli T. (1SS0) - I1 Canton Ticino meridionale e i paesifinitimi. Mat. Carta Geol. Svizzera, s. 1, v. 17, v. oÍ 230oo.- Bern. Receio.ted August 3, 1995; accepted October 4, 1995rr', --""

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THE DISCOVERY OF AMMONOIDS IN THE CUNARDO FORMATION (VARESE). A NEW CHRONOSTRATIGRAPHIC INTERPRETATION

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