GSSP of base of Ladinian The Global Boundary Stratotype Section and Point (GSSP) for the Base of the LADINIAN STAGE (Middle Triassic)

A proposal for the GSSP at the base of the curionii zone in the Bagolino section (Southern Alps, Northern Italy)

Peter Brack1, Hans Rieber2, Alda Nicora3

1Departement Erdwissenschaften, ETH-Zentrum, CH-8092 Zürich 2Paläontologisches Institut, Universität Zürich, CH-8006 Zürich 3Dipartimento di Scienze della Terra, Università di Milano, Via Mangiagalli 34, I-20133 Milano

ABSTRACT the South Alpine Buchenstein Beds and siliceous The Global boundary Stratotype Section and Point limestones of Bakony (Hungary). Because (GSSP) for the Base of the LADINIAN STAGE Mojsisovics erroneously equated this interval with (Middle Triassic) is defined at the top of a distinctive parts of the ammonoid-rich Hallstatt-limestones, 20-cm-thick groove (= “Chiesense groove”) of he used the term “Norian” as the stage name. limestone nodules in a shaley matrix, located about “Norian” refers to the Norian Alps around Hallstatt 5 m above the base of the Buchenstein Beds in the near Salzburg (Austria). Later, the Hallstatt- Caffaro river bed (45°49ʼ09.5ʼʼN, 10°28ʼ15.5ʼʼE), ammonoids turned out to be much younger. Bittner south of the village of Bagolino (Province of (1892) therefore proposed the term “ladinisch” Brescia, northern Italy). The lower surface of (Ladinian) as a new label of the stratigraphic the overlying thick limestone bed has the lowest interval of South Alpine Buchenstein and Wengen occurrence of the ammonoid Eoprotrachyceras Beds. Although not accepted by Mojsisovics et al. curionii (base of the E. curionii zone; onset of the (1895), “Ladinian” was subsequently a generally Trachyceratidae ammonoid family). Secondary adopted stage name (e.g., Arthaber, 1906). global markers in the uppermost Anisian include In the time of Mojsisovics, knowledge of ammonoid the lowest occurrence of conodont Neogondolella successions in the Anisian/Ladinian boundary praehungarica and a brief normal-polarity interval was still fragmentary and correlations magnetic zone. The GSSP level is bracketed by were rather speculative. For instance, the South U-Pb single zircon age data, indicating that the Alpine Buchenstein Beds and siliceous limestones boundary age is ~ 240 to 242 Ma. in Bakony were considered age equivalents and both attributed to the R. reitzi zone. However, STRATIGRAPHIC RANK OF BOUNDARY recent biostratigraphic results on ammonoids, Base of the Ladinian Stage in the Middle Triassic conodonts and radiolaria (see further on) clearly Series. document that the main ammonoid bearing interval of Mojsisovicsʼ “yellow siliceous limestones of Relation of the GSSP to historical usage Bakony” slightly predates and overlaps in age with The long history of concepts regarding the Anisian/ only the lowermost South Alpine Buchenstein Ladinian boundary is summarized and illustrated Beds. Moreover the base of the Buchenstein Beds in Brack & Rieber (1994). These views have been is diachronous and the lower part of this unit has further discussed by Kozur (1995). sometimes also been considered Anisian. In the The first formal recognition of a stratigraphic light of a modern definition of the base of the interval comprising what is now called Ladinian Ladinian Stage, the original concepts and historical goes back to the subdivisions of the Triassic usage of the Anisian/Ladinian boundary provide System proposed by E.v.Mojsisovics. Ammonoids no unambiguous basis for the positioning of the served as the main biostratigraphic tool for these GSSP. What still may be considered of particular divisions. By 1874 and with later modifications relevance in this context is that in his introduction (e.g., 1882), Mojsisovics used the name “Norian” of the term “ladinisch” (Ladinian), Bittner (1892) for a stratigraphic interval including, at its base, specifically referred to stratigraphic successions

- 1 - GSSP of base of Ladinian

1

M. Re di Castello Schilpario 2 Concarena M. Corona Stabol Fresco 3 C.naS.Fermo Ch Breno M. Frerone iese e i Contrada Gobbia r a Prezzo 4 c Dezzo a Cimego i c d i o r u n a f f i o a 5 C G m l o i e gl a O d i

C e l l

l l

l a

a V a 6 V V Bagolino

ia mp 7 o Dosso Alto o Tr r al d V I ' d N

o

g P.Aiale a L 10 km 8 M.Guglielmo Pèrtica 7˚E A 13˚E CH 46˚N se 9 ie Brozzo h C Brescia Marcheno Milano Venezia F ITALY 44˚N 10 Figure 1: Geological sketch map of the area with classical localities of Middle Triassic stratigraphy in eastern Lombardy and Giudicarie (Trentino). 1: Pre-Permian basement; 2: Permian to Lower Triassic including lowermost Anisian units; 3: Mainly lower/middle Anisian units (Angolo Lst.; Dosso dei Morti - Camorelli Lst.); 4: Upper Anisian - Ladinian pelagic successions (Prezzo Lst., Buchenstein- and Wengen Beds); 5: Ladinian / Carnian platform carbonates and age-equivalent intra platform deposits (Pratotondo Lst., Lozio Shales); 6: Ladinian - Carnian shallow intrusive rocks; 7: Norian - Rhaetian shallow water carbonates and basinal equivalents; 8: Jurassic - Cretaceous units; 9: Tertiary Adamello plutonics; 10: major tectonic lines (faults and thrusts). in the Southern Alps, with the Buchenstein Beds boundary succession is well exposed at three sites as the oldest unit. The lower part of the South in the bed of the river Caffaro, in the surroundings Alpine Buchenstein Beds is thus an appropriate of the Romanterra bridge, south of the village of stratigraphic interval for establising the GSSP for Bagolino (Sites A - C; see Fig.2). The GSSP-Site the base of the Ladinian Stage. is situated close to eastern end of Site B and its coordinates are 614.276 / 5075.118 (UTM-grid) PROPOSED GSSP - GEOGRAPHIC AND and Long./Lat. 45°49ʼ09.5ʼʼN, 10°28ʼ15.5ʼʼE PHYSICAL GEOLOGY respectively. Bagolino can be reached by car or by public Geographic location transport from Brescia. A bus station is located at The GSSP-candidate at Bagolino (Province of short distance from the Romanterra bridge. The Brescia, Northern Italy) is located in the Brescian bridge can also be reached by car and its coordinates Prealps portion of the Southern Alps, and more are 45°49ʼ11.1ʼʼN, 10°28ʼ8.6ʼʼE and the altitude precisely, in Valle del Caffaro between Val Camonica is 646m. From this point the main exposures lie and Valli Giudicarie (Fig.1). The Anisian/Ladinian within walking distance along the banks and in the - 2 - GSSP of base of Ladinian

500 m C 800 a f f BAGOLINO a

r o

R i v 700 e r

e eston lo Lim Ango B stone Lime A C ezzo Pr ds n Be nstei o m uche R a n B t e 5075 eds r gen B r Wen a 0 0 0 0 GSSP-Site 3 2 00 1 1 14

0 0 1 1 ol. Lst./D 700 Esino

0 0 8 D 9 00

0

0

0

1

900

ipale Princ 3 4 omia 1 1 Dol 6 6 Figure 2: Geological sketch map of the vertical to slightly overturned Middle Triassic succession in the surroundings of Bagolino. The main sites (A - D) with exposures of the Anisian/Ladinian boundary interval are indicated. The stratigraphic ranges of the intervals exposed at each site are shown in Fig.3. A continuous succession ranging from the uppermost Angolo Limestone to the Wengen Beds is exposed at Site A. The frame at Site B outlines the area of a detailed map of this outcrop as illustrated in fig.4 of Brack & Rieber (1986). Coordinates of GSSP-Site: Long./Lat. N 45°49’09.5’’, E 10°28’15.5’’. bed of the Caffaro river. The GSSP-Site (= Site B) Bagolino (Fig.1), including the classical locality at is situated approximately 150m ESE of the bridge. Dosso Alto and important complementary sections Site B lies downstream of a dam deviating the river at Pèrtica, Brozzo and Marcheno. To the north waters. Parts of the outcrops may be submerged of Bagolino, Middle Triassic pelagic sediments during high river waters in spring or after heavy occur along the southern margin of the Adamello showers. The other sites are inaccessible only with intrusives. This area hosts important sections in extreme winter conditions. Giudicarie (Prezzo, at the eastern termination of Val di Daone; Monte Corona - Stabol Fresco) and Geological setting in Val Camonica (e.g., Contrada Gobbia). The Middle Triassic succession at Bagolino is At Bagolino, the pelagic succession consists part of a thick sediment prism comprising Lower from bottom to top of the Prezzo Limestone, the to Upper Triassic strata, which are turned upright Buchenstein Beds and the Wengen Beds. The in front of an uplifted portion of the Brescian succession is well exposed at different places in Prealps. The latter area is situated to the north of the Caffaro river bed at Romanterra (Fig.2). The a bounding fault (Val Trompia Line) and consists same lithologies occur in scattered outcrops on the of pre-Permian metamorphic basement and Lower southern slopes of M. Pizza (Site D). Additional Permian - Triassic cover rocks. Alpine deformation exposures of these strata are also accessible along of the Middle-Upper Triassic rocks south of the the Rio Ricomassimo creek around 3km east- Val Trompia Line was the result of south-directed northeast of Romanterra. tectonic transport of basement and cover rocks The stratigraphic succession at Romanterra, as which occurred in two phases, prior and after the documented in Figure 3, starts in the uppermost emplacement of the Eocene-Oligocene Adamello Angolo Limestone with a distinct brachiopod intrusives respectively. lumachella at its top. The pelagic Prezzo Pelagic successions of Middle Triassic age are Limestone consists of limestone-shale alternations also exposed at various places south and west of with nodular to wavy bedding in the lower and - 3 - GSSP of base of Ladinian '

s Exposed stratigraphic Important Macrofossils d (Ammonoids, Daonella) F.regoledanus

e intervals at sites A-D: zone

B Frankites 100 n e

g D. lommeli U-Pb zircon ages

n in Ma from e P. archelaus (MC) Mundil et al. (1996) W N ' Daonella lommeli 238.0 +0.4 P.archelaus 90 - 0.7 zone D. tyrolensis (Seceda) A

D. pichleri (MC) I

' + 1.0

237.9 - 0.7 N s I d (Bagolino) e B B 80 D e t

i Protrachyceras n i S A e t

P.gredleri L s Arpadites zone

n + 0.5 238.8 - 0.2 e D

h 70 (Bagolino) e t c i u S E.curionii B ' Eoprotrachyceras zone Chieseiceras GSSP-Level 5 N.secedensis . Nevadites + 0.8

g zone i 241.2 - 0.6

C 60 Ticinites F Halilucites

e (Seceda/ s t

' Parakellnerites . i n M.S.Giorgio) s s Aplococeras R.reitzi S d n m Reitziites e a u Hungarites zone l r b t ' o Kellnerites

C Lardaroceras (Pe) Asseretoceras (SF) 50 Daonella sturi P.trinodosus zone Paraceratites "C." abichi gp. A e t e

i 40 n S

o Judicarites t s e m i N L 30 o A z z I e r S P I 20 N A

correlated macrofossils: (Pe) Pèrtica 10 (MC) M. Corona (SF) Stabol Fresco

Bulogites (SF)

e 0m

n Balatonites cf. balatonicus (SF) o l o Brachiopod Bed B.balatonicus

t Acrochordiceras (SF) o

s zone g e n m A i L Figure 3: Summary log of the Middle Triassic pelagic succession at Bagolino. The stratigraphic intervals exposed at Sites A - D as well as the main macrofossil horizons and the scheme of ammonoid zones are indicated. Isotopic age data are weighted mean U-Pb-ages (uncertainties at 95% confidence level) on single grain zircon from volcaniclastic layers at Bagolino and Seceda (from Mundil et al., 1996).

- 4 - GSSP of base of Ladinian

.8 0 .6 + 0 - .2 Base 1 4 Reitzi Zone 2

e it 5 2

. S . 0 - 0

- P + S m S 8 .

0 G 8 6 3

2

. Z is s n m e e 5 d m e n 6 m c o e Z l) 0 4 S ii e 7 7 e n v s o a i le B r - u P C S e s S a G B (=

Figure 4: View of the spectacular outcrop of Buchenstein Beds at Site B (eastern end; = GSSP-Site) with a continuous exposure of strata between the reitzi zone and the archelaus zone (base of Wengen Beds). more regular and thicker bedding in the upper slide of the river bank part. In an interval transitional to the Buchenstein Beds, the first significant volcaniclastic layers are Location of Level and Specific Point interbedded with increasingly siliceous limestones The proposed GSSP-level at Bagolino is defined and shales. The Buchenstein Beds consist of in the lower part of the Buchenstein Beds, around siliceous pelagic nodular limestones and up to a 5m above its base, at the top of a distinct 20-25cm- few decimetres thick volcaniclastic layers which thick interval of limestone nodules in a shaly can be traced laterally on a regional scale. A matrix in contact (upwards) with several thick marked change in sedimentation is observed at the limestone beds (Fig.5b). The nodular limestone top of the Buchenstein Beds with the abrupt switch interval is known as the “Chiesense groove” and to the predominantly siliciclastic Wengen Beds. bears ammonoids such as Chieseiceras chiesense The Anisian/Ladinian boundary interval comprises and ʻStoppanicerasʼ (ellipticum-group). On the the “transitional beds” and the lower part of the lower surface of the overlying thick limestone Buchenstein Beds and is best exposed at Sites A - bed Eoprotrachyceras curionii has its lowest C. In particular, at the eastern end of Site B (Fig.4; occurrence. Macrofossils were found at this level for a detailed map of this outcrop see fig.4 in Brack at all sites mentioned for Bagolino (Figs.2,3,5). & Rieber, 1986), the fully exposed strata from the Because of the particularly vast exposure, the 57m-level upward can be traced over several tens eastern end of Site B (Fig.4) is designated as the of metres along strike. At Site C, until recently, principal outcrop / section for the GSSP. an undisturbed succession was exposed of the 51- 65m-interval and which comprised all boundary Stratigraphic completeness positions hitherto discussed as potential base of No signs of stratigraphic gaps have been detected the Ladinian Stage. Unfortunately the lower part so far in the pelagic part of the Middle Triassic of this section is now partly covered by a recent sediment succession at Bagolino. The reduction of

- 5 - GSSP of base of Ladinian

Site A Site C

Outcrop Site C Section continues to top of Buchenstein Beds (beds are vertical)

) Eoprotrachyceras curionii Eoprotrachyceras curionii "

e "Chiesense groove" k

l Chieseiceras chiesense Chieseiceras chiesense a

'Stoppaniceras' (ellipticum-gr.) , k s i

n Monophyllites sp. d e a l l s p r d o a e n . B K A " n , i ( Nevadites sp. e e t s

'Celtites' s Te s n n e

d Te e s e h e i c B

h Td u c B n . i f h

Td o a e C t c i p : s d o s t Chieseiceras sp. r l n i a s o e b t

s Tc h o o s f g c e o n u r u Tc o c l n i B t a .

Proarcestes f n m c o c d Ticinites brescianus a l l e n t

Parakellnerites aff. boeckhi e o c i n t e l Aplococeras sp. o c l a e o s c D

Halilucites rusticus Parasturia sp. (coll. and det. by Lecanites misanii Mietto et al., 2003) ) 3 y Tbc 0 Aplococeras avisianum b 0 . t 2

A. avisianum, A. aff. smithi, Parakellnerites sp. e , . d l

Parakelln. sp., Kelln. sp., Reitz. sp., "Megaceratites" sp. a d t Parakelln. sp., Kelln. sp., Reitziites reitzi n

c e

Tb a .

Parakellnerites, "Semiornites" falcifer o l t l t

H. bagolinensis o b e Tb i c Parakellnerites arthaberi ( Reitziites reitzi M s

f Parakellnerites arthaberi f 57 u t a - Reitziites reitzi Tb Reitziites reitzi b Reitziites ?

T Kellnerites bagolinensis Kellnerites bagolinensis Tba Kellnerites bagolinensis Reitziites reitzi Ceratitidae cf. hungaricus Kellnerites bagolinensis 56 " Ceratitidae gen. indet. s

d Kellnerites bagolinensis e Tac Hungarites sp. b

l Hungarites ? a

n b c Ta Kellnerites bosnensis o Ta 55 i

t Kellnerites angustecarinatus i s

f a s f Ta Kellnerites cf. ecarinatus u n b t Ta

- Kellnerites bosnensis a r a

t Kellnerites angustecarinatus T " Kellnerites bosnensis Kellnerites fissicostatus Taa Hungarites lenis, Norites sp. 54 Hungarites lenis, Norites sp. 'Hungarites' cf. lenis 'Hungarites' cf. lenis Ceratitidae cf. hungaricus Ceratitidae cf. hungaricus Kellnerites sp. Kellnerites sp.

53 Kellnerites sp. Site D Kellnerites halilucensis Norites gondola Lardaroceras sp. 52 e s n f f o u t t - s 51 e G C m i

L 51 o z

z exposures of Prezzo Lst. e r corresponding to P 43-50m-interval) 50 section continues to base of Prezzo Lst. (= 0-m-level) Fig. 5a

- 6 - GSSP of base of Ladinian Site B (east) = Bagolino reference GSSP location (composite log, reference m-scale Section continues to top of and compiled macrofossil data) Buchenstein Beds; for ammonoids and Correlated fossils: Daonella from this part see Fig.7 in U-Pb zircon Pe: Pèrtica ages [Ma] from

Brack & Rieber (1993). e

Pr: Prezzo N

Mundil (1996) n o + 0.5 A 65 65 z

Eoprotrachyceras recubariense Eoprotrachyceras recubariense 238.8 - 0.2 I i i Eoprotrachyceras rieberi Eoprotrachyceras rieberi at 72.2m N n Chieseiceras perticaense Chieseiceras perticaense I o i D r u c 64 Chieseiceras perticaense 64 Chieseiceras perticaense A . L E GSSP Eoprotrachyceras curionii Eoprotrachyceras curionii

Chieseiceras chiesense Chieseiceras chiesense s e t 63 'Stoppaniceras' ellipticum-gr. 63 'Stoppaniceras' ellipticum-gr. i h

Monophyllites sp. c y e t p n

Nevadites avenonensis (Pe) o o x z

Daonella fascicostata (Pr) e l

Nevadites sp. F s B Te 62 Nevadites sp. 62 'Celtites' i s

e Te n t i

'Stoppaniceras' ellipticum-gr. (Pr) e S Td Td d Halilucites cf. arietitiformis (Pe) e m c o Chieseiceras sp. Chieseiceras sp. e r s f . 61 'Stoppaniceras' ellipticum-gr. l 61 'Stoppaniceras' ellipticum-gr. a N

Tc v Tc + 0.8 r Nevadites sp. (Pr) 241.2 - 0.6 e Halilucites cf. obliquus, H. sp. t (Seceda) n Halilucites cf. obliquus, H. sp. I s e Ticinites brescianus Ticinites brescianus t s

60 Parakellnerites aff. boeckhi 60 Parakellnerites aff. boeckhi e c Stoppaniceras sp. Stoppaniceras sp. r a

Aplococeras sp. o r ) t r P a

Parakellnerites sp. Parakellnerites sp. p r

Halilucites rusticus e

59 59 Parasturia p

(coll. and det. by p

Lecanites misanii u Mietto et al., 2003) (

Hungarites zalaensis Hungarites zalaensis ) 3 y 0 b

Aplococeras avisianum 0 . t c 2 Tb A. avisianum, A. aff. smithi, Parakellnerites sp. e , .

58 58 d Parakellnerites sp., Kellnerites sp. l

Parakellnerites arthaberi a d t "Megaceratites" sp., Reitziites reitzi n e a . o

Parakellnerites, "Semiornites" falcifer l t Reitziites reitzi l t o

H. bagolinensis, Reitziites reitzi e i c ( e

b Parakellnerites arthaberi M

Tb n

57 57 Parakellnerites arthaberi o Reitziites reitzi z Reitziites reitzi i

Reitziites ? z t Kellnerites bagolinensis i e r

Kellnerites bagolinensis .

56 Ceratitidae cf. hungaricus R Ceratitidae gen. indet. 1m Ta/c Kellnerites bagolinensis Hungarites sp. Ta-Tuffs Hungarites ? All sections 55 Kellnerites bosnensis

same scale C Kellnerites angustecarinatus

e Kellnerites cf. ecarinatus t ) i t

0 r S N Kellnerites bosnensis a p r m Kellnerites angustecarinatus e o A r Kellnerites fissicostatus

54 w f o l

l Hungarites lenis, Norites sp. ( a Kellnerites sp. I v

r 'Hungarites' cf. lenis e

t Ceratitidae cf. hungaricus S n

I Kellnerites sp. 53 Kellnerites halilucensis I Norites gondola e n o N z Lardaroceras aff. pseudohungaricum (Pe) s A 52 Lardaroceras aff. krystyni (Pe) u s o d o n

Asseretoceras camunum -horizon i r

CG-Tuffs at Contrada Gobbia (= CG Nr.5) and Stabol Fresco t (= SF Nr.105a) in Balini et al. (1993). . Fig. 5b 51 P Site A Figure 5a,b: Detailed stratigraphic logs with distribution of ammonoids in intervals around the Anisian/ Ladinian boundary at sites A-D and resulting composite log with integrated age information for Bagolino. Specific volcaniclastic marker beds used for bed-by-bed correlation are indicated and labelled. The designated GSSP-section is at Site B (eastern end), i.e. at the base of the curionii zone corresponding to the top of a distinctly recessive weathered interval with limestone nodules in a shaly matrix (“Chiesense groove”).

- 7 - GSSP of base of Ladinian clay content at the base of the Buchenstein Beds realm of western Tethys where, in a single section, suggests a decrease of the sedimentation rate from all levels discussed as potential Anisian/Ladinian moderately high values in the Prezzo Limestone to boundary have been identified on the basis of low values in the Buchenstein Beds. On the basis of ammonoids (Fig.6b)! isotopic age constraints, the average sedimentation Comparable sections elsewhere in the Southern rates in the (non-decompacted) siliceous pelagic Alps are either condensed (e.g., Clap di Val: see nodular limestone of the Buchenstein Beds in Mietto & Manfrin, 1995), show a much lower the Dolomites are estimated to be in the order of number of ammonoid horizons (e.g., Seceda, 10m/m.y. (Brack & Muttoni, 2000). In comparison Margon / Val Gola; Fig.6a) or have a limited with the Dolomites the thickness of corresponding stratigraphic range (e.g., M.S.Giorgio; Fig.6b) intervals of Buchenstein Beds in sections of and/or a punctuated fossil record in non-pelagic eastern Lombardy (including Bagolino) and settings (e.g., storm-layers in the plaform-interior Giudicarie is reduced by 40-50% and the rates carbonate succession at Latemar; e.g. Mundil et of sedimentation are accordingly lower. The al., 2003; Manfrin et al., in press). layers with predominantly airborne volcaniclastic material obviously represent short-lived deposition Provisions for conservation and protection on the scale of duration of volcanic eruptions. The The existence of exposures of Buchenstein Beds siliciclastic Wengen Beds again represent rapid south of the village of Bagolino (Site B) was sediment accumulation. indicated by Bittner (1881). Mariani (1906) In spite of the somewhat reduced thickness of the documented the first ammonoids from these beds. Anisian/Ladinian boundary interval at Bagolino This is sufficient guarantee for a long persistence its ammonoid record seems to be exceptionally of the natural exposures in the Caffaro river bed. complete (Fig.5). Moreover, a good portion of the outcrop surface is periodically cleaned by high river waters. Adequate thickness and stratigraphic extent The authorities of Bagolino are prepared to The entire pelagic succession exposed at Bagolino maintain and label an easy access to the river bed (Fig.3) is more than 100m thick and ranges in age of the main outcrop (Site B) and to fix appropriate from the middle/late Anisian to the late Ladinian. posters with information also for the public. Ammonoid faunas of the balatonicus zone and from a stratigraphic level corresponding to the Brachiopod Bed at Bagolino are known from Giudicarie (e.g., Balini et al., 1993; Brack et al., OTHER USEFUL SECTIONS 1999). The Prezzo Limestone at Bagolino bears Stratigraphic results from the most relevant South ammonoids from the Judicarites-horizon upwards. Alpine sections complementary to Bagolino and Nearby sections of Prezzo Limestone (e.g., Stabol of significance for the definition of the base of the Fresco, Contrada Gobbia; see Balini et al., 1993; Ladinian Stage are shown in Figure 6a,b. Balini, 1998) bear one of the richest ammonoid New stratigraphic data are now also available from faunas reported so far for the trinodosus zone in a multidisciplinary study of the Seceda core (Brack Western Tethys. At Bagolino the ammonoid record et al., 2000). So far these efforts have resulted shows a particularly high resolution in the reitzi, in a detailed sedimentological characterisation secedensis and curionii zones. Ammonoids and of Buchenstein lithologies (Maurer & Schlager, Daonella are known from the upper Buchenstein 2002) as well as in detailed information on its and from the Wengen Beds, with representatives of magnetostratigraphy and conodonts (Muttoni et Frankites (regoledanus zone) being the youngest al., 2004). For the GSSP here proposed, Seceda ammonoids found to date. is therefore the principal auxiliary section, mainly In the Southern Alps and beyond, the Bagolino because it adds magnetostratigraphy, isotope and section is thus arguably one of the most extensive complementary conodont data to the information not condensed and macrofossil-bearing Middle from Bagolino. However, the stratigraphic range Triassic succession known so far. Moreover, the and number of macrofossil levels known from Anisian/Ladinian boundary interval at Bagolino Seceda is clearly inferior to the resolution of the (i.e. the interval corresponding to 51-65m of the fossil record in the proposed GSSP-section at reference scale; Fig.5) is the only place in the Bagolino (Fig.6a,b).

- 8 - GSSP of base of Ladinian

PRIMARY AND SECONDARY MARKERS last Ceratitidae (ʻStoppanicerasʼ ellipticum-gp.), Nevadites and Ticinites below the GSSP-level Principal correlation event (marker) at GSSP (Brack & Rieber, 1986, 1993; Brack et al., 1995). level The fossil record below the layers with Ticinites The proposed GSSP-level at Bagolino is defined provides an excellent correlation of sections in the with the first appearance of the ammonoid Southern Alps with those in Hungary (Figs.6,8). genus Eoprotrachyceras, i.e. with the species The ammonoid zones referred to in this proposal Eoprotrachyceras curionii (MOJS.) as indicated are understood as assemblage zones and are named above. In all sections studied thoroughly in eastern after a typical ammonoid species. Following Lombardy (including Bagolino) and Giudicarie E. Brack & Rieber (1993, 1994) and Rieber & Brack curionii occurs in a single layer. To date there is no (2002) the base of the reitzii zone (= Reitziites evidence for the occurrence of older representatives reitzi zone) is defined by the FAD of the genus of the genus Eoprotrachyceras. Kellnerites, the base of the secedensis zone (= In western Tethys E. curionii is thus the oldest known Nevadites secedensis zone) by the FAD of the representative of the genus Eoprotrachyceras and genus Ticinites and the base of the curionii zone marks the onset of the family Trachyceratidae. (= Eoprotrachyceras curionii zone) by the FAD The genus ʻAnolcitesʼ shares some morphological of the genus Eoprotrachyceras respectively. In characters with, and its FAD predates that of western Tethys the genus Eoprotrachyceras is Eoprotrachyceras. However, the stratigraphically the oldest representative of the ammonoid family oldest representatives of ʻAnolcitesʼ seem to be Trachyceratidae. Note, however, that alternative descendants of Nevadites, which is considered to schemes with ammonoid zones and subzones belong to the Ceratitidae (Tozer, 1994a; Rieber & proposed for the Anisian/Ladinian boundary Brack 2002). interval differ from these definitions. Until The proposed GSSP-level allows an excellent recently (e.g., Vörös et al., 1996; Vörös, 1998) correlation of sections not only in the Southern the Hungarian stratigraphers used a corresponding Alps but also the recognition of a corresponding reitzi zone (including four subzones, named level in Greece (Epidavros). Representatives of felsoeoersensis, liepoldti, reitzi, avisianum) with the genus Eoprotrachyceras have been reported its base placed at the FAD of Kellnerites. However, from numerous places including the Triassic without a specific explanation, Vörös et al. (2003) successions in North America (Nevada, British have reduced the range of the reitzi zone to only Columbia) and is therefore a suitable marker for comprise the reitzi and avisianum subzones. The trans-Panthalassan correlation. scheme of ammonoid zones and subzones used The narrow interval with Chieseiceras chiesense by Mietto et al. (2003a,b) refers to a succession of immediately below the layer with E. curionii is the following subzones: reitzi, avisianum, crassus. another most suitable marker for correlation of In this scheme the reitzi and avisianum subzones sections in the Southern Alps and Greece. largely correspond to the lower and upper parts of our R. reitzi zone respectively. With respect to Mietto & Manfrin (1995), the base of the crassus Other stratigraphy subzone (lowermost subzone of their Nevadites zone) is redefined by Mietto et al. (2003a,b) with Biostratigraphy the FAD of Halilucites, i.e. at a level slightly above the 59m-level of the Bagolino reference scale but Other Ammonoids and definition of ammonoid clearly below the base of the secedensis zone at zones the 60m-level. Apart from the macrofossils mentioned above and proposed for the collocation of the GSSP, Conodonts the record of ammonoids is particularly well Conodont data are available from Bagolino (Nicora established also above and below the GSSP-level. & Brack, 1995; Brack & Nicora, 1998) and closely Within the Brescian Prealps and Giudicarie firm correlated sections (Pèrtica, Brozzo: Nicora & correlations are evident for ammonoids with a short Brack, in prep.; Stabol Fresco: Kovács et al., 1990 range such as Eoprotrachyceras recubariense, E. and updates). New results from the Dolomites rieberi, Chieseiceras perticaense above, and the (Muttoni et al., 2004) provide a significant

- 9 - GSSP of base of Ladinian

Margon / Val Gola Frötschbach Seceda at 49m (Upper Pietra Verde) [m] [m] 238.0 + 0.4 Arpadites (M) - 0.7 Arpadites sp. 25 Arpadites- Layer (M) at 39.2m

30 n n 2 2 n F M 3 C S (Eo-)Protrachyceras margaritosum (G) 20 (in scree) 25 SC2r.2n Eoprotrachyceras cf. recubariense r 2 . r 2 r r 1 6 C 6 2 S . M

r 20

) 4 (pelagic marker 1 4 M F ( beds 1-6)

n 2 2 o Eoprotrachyceras curionii 15 g r a

SC2r.1n r M

Chieseiceras 1 . cf. chiesense F1r.1n Chieseiceras r Chieseiceras chiesense 2 C n Nevadites sp. chiesense S 1 F1r.1r (in block) M Daonella cf. golana 15 Nevadites secedensis 1m n Nevadites crassiornatus 2 . n n

1 Te - Tuff

) Te - Tuff

0 2 F G ( Td - Tuff C ) Td - Tuff S 4 8

+ Tc - Tuffs 4 Tc - Tuffs + 0.8 6 F1n.1r 241.2 - 0.6 9 1 ( 10 Ticinites dolomiticus

a Daonella golana l o F1n.1n Stoppaniceras evolutum G

l Stoppaniceras

a Daonella elongata V golanum Daonella caudata ? Te - Tuff Daonella angulata Daonella angulata Parakellnerites sp.

r Daonella serpianensis

1 Daonella cerneraensis C Parakellnerites aff. rothpletzi S 5 5 Aplococeras sp.

? Td - Tuff D. airaghii Daonella pseudomoussoni 0 Daonella elongata

0

+ 0.8 acidic volcaniclastic layers 241.2 - 0.8 U-Pb single zircon ages (Mundil et al., 1996) siliceous nodular pelagic limestones Magnetic polarity (dark: normal; white: reversed) laminated (partly kerogenous) limestones Frötschbach, Seceda after Muttoni et al. 2004; bituminous shales and dolomites Val Gola/Margon after Gialanella et al. (2001). marls and marly limestones Macrofossils (ammonoids, daonella): Bagolino: Brack & Rieber (1986,1993), Brack et al. (1995) and later updates; Mietto et al. (2003b) Seceda, Val Gola, Frötschbach: Brack & Rieber (1986, 1993) Monte San Giorgio: Rieber (1968, 1969, 1973), Brack & Rieber (1986, 1993) and updates. Fig. 6a

Figure 6a,b: Compilation of important stratigraphic results from correlated South Alpine sections in the Anisian/Ladinian boundary interval (updated after Brack et al., 2001) with indication of lithological markers (volcaniclastic layers, bedding patterns), magnetic reversals, isotopic age data and the ranges of macrofossils (ammonoids, Daonella). The Seceda section is the main auxiliary section in the Dolomites. The correlation of key fossils and the proposed GSSP-level at the base of the curionii zone are highlighted. Also shown is the correlation with the zonal scheme and important fossil horizons of the Balaton Highland (Felsöörs; Vörös et al., 2003). Triangles with numerals mark the positions of various proposals for the base of the Ladinian Stage: 1-3 correspond to the GSSP-proposals in Albertiana 28; 1b and 2b are older alternatives.

- 10 - GSSP of base of Ladinian

Bagolino M. S. Giorgio

[m] at 72.2m (Middle Pietra Verde) + 0.5 238.8 - 0.2 Arpadites arpadis at 70.5-75.6m N (Eo-)Protrachyceras margaritosum

Daonella sp. A I N ) e l

230 a c I s e o t n t o o n z ( D i 199 s i r ö n o 65 s o

Eoprotrachyceras recubariense s e i l r A n e o u Eoprotrachyceras rieberi F z t Chieseiceras perticaense c b a . u s L s E Chieseiceras perticaense d e N 160 b O e c Eoprotrachyceras curionii 'Protrachyceras' cf. gortanii T 150 n A e r GSSP 3 L e e f Chieseiceras chiesense Chieseiceras chiesense A n e r 'Stoppaniceras' ellipticum-gr. B Monophyllites sp. o Daonella golana z Nevadites avenonensis (Pe) 'Stoppaniceras' s Daonella fascicostata (Pr) 112 i Nevadites sp. Nevadites ambrosionii s Te - Tuff Serpianites serpianensis n

e 117 98 Daonella fascicostata Td - Tuff d

Halilucites cf. arietitiformis (Pe) 'Stoppaniceras' e Chieseiceras sp. Daonella pseudomoussoni c e

'Stoppaniceras' ellipticum-gr. Daonella airaghii s + 0.8 Tc - Tuffs Stoppaniceras 241.2 - 0.8 .

Nevadites sp. (Pr) 69 Aplococeras misanii N Halilucites cf. obliquus, H. sp. Daonella vaceki 113 Ticinites brescianus 61 Stoppaniceras variabilis polymorphus 60 Parakellnerites aff. boeckhi 58 Ticinites 2b 111/J Stoppaniceras sp. Daonella elongata ) t

Aplococeras sp. Daonella caudata r a

Daonella angulata p Parakellnerites sp. m 41 r Halilucites rusticus Parakellnerites u e n

35 Daonella serpianensis p

Parasturia a i (Mietto et al., 2003) p u Lecanites misanii Aplococeras cf. avisianum s i ( Hungarites zalaensis v 1m a Aplococeras avisianum (Mietto et al., 2003) Aplococeras aff. smithi 10 0 "Megaceratites" 2 110 Parakellnerites arthaberi e n i o P. cf. arthaberi z t i Reitziites reitzi z e r Parakellnerites arthaberi i z

Reitziites reitzi t i 105 Reitziites ? e 1 i r t

Kellnerites bagolinensis . d l R

Kellnerites bagolinensis o

Ceratitidae cf. hungaricus p e i l Ta/c Kellnerites bagolinensis 100 Hungarites sp. Ta-Tuffs Kellnerites bosnensis 55 ) s t i Kellnerites angustecarinatus r s a N p Kellnerites cf. ecarinatus n r e e

Kellnerites bosnensis s r Kellnerites angustecarinatus w ö o l o ( Kellnerites fissicostatus A s

Hungarites lenis, Norites sp. l e 'Hungarites' cf. lenis f Ceratitidae cf. hungaricus I Kellnerites sp. 1b . 100F Kellnerites halilucensis h . o Norites gondola S z d

correlated u e macrofossils: s s aff. pseudohungaricum (Pe) I Lardaroceras u (Pe) Pèrtica p

s 97 Lardaroceras aff. krystyni (Pe) (Pr) Prezzo . o a d c N o

Asseretoceras camunum-horizon at Contrada Gobbia (= CG Nr.5) n 90 CG-Tuffs i

and Stabol Fresco (= SF Nr.105a) in Balini et al. (1993). r t . A P

Fig. 6b

- 11 - GSSP of base of Ladinian extension of the conodont record reported earlier Daonella are precisely located in layers of the for Frötschbach (Muttoni et al., 1996, 1997). middle (D. cf. longobardica, D. moussoni) and Figure 7 shows the conodont distribution at upper Buchenstein Beds (D. taramellii, D. pichleri, Bagolino and compiled data from additional D. tyrolensis) at Bagolino, M. Corona and Seceda sections accurately correlated with Bagolino on (Brack et al., 2000; Schatz, 2001a,b; Maurer & the basis of bio- and lithostratigraphy. Rettori, 2002). In the Anisian/Ladinian boundary interval, the most significant “conodont events” are the Radiolarians following: (1) Close to the base of the reitzi zone, Numerous, but hitherto unreported species of Neogondolella cornuta postcornuta and the group radiolarians have been detected in samples from of Paragondolella alpina appear among other Buchenstein Beds from Seceda and Frötschbach taxa; (2) In the upper reitzi zone, Neogondolella (H. Kozur, pers. commun.). Of these, the pseudolonga, Paragondolella fueloepi and radiolarians from the uppermost Plattenkalke Paragondolella trammeri appear for the first with Daonella of the elongata-group (lower time; (3) In the upper part of the secedensis zone, Buchenstein Beds; Fig.6) can be attributed to the Neogondolella praehungarica appears together Oertlispongus inaequispinosus subzone (upper with a precursor form of Budurovignathus Spongosilicarmiger italicus Zone). In agreement gabriellae provisionally referred to here as with the correlation based on macrofossils Neogondolella sp. A; (4) Budurovignathus truempyi (Seceda-Bagolino, Bagolino-Felsöörs; Figs.6 and and B. hungaricus occur in layers corresponding 8), at Felsöörs (Fig.8) this radiolarian subzone to the 66m-level of the Bagolino reference column comprises the layers 110-111C (Vörös et al., 2003). or higher up. This radiolarian subzone is known throughout the The appearance of N. praehungarica and its co- Tethys and has also been recognised in radiolarites occurrence with P. fueloepi in the upper part of the of Panthalassa (Japan, Philippines) thus allowing secedensis zone, just below the proposed GSSP- a correlation with ammonoid-free and mostly level, seems at present to be the only suitable conodont-free low latitude oceanic radiolarite marker for conodont-based correlation with data successions. from Nevada and British Columbia (Bucher & The most complete available uppermost Anisian Orchard, 1995; Orchard & Tozer, 1997). to lower Ladinian radiolaria succession (beginning with the reitzi zone) is known from the Recoaro Daonella area (Kozur & Mostler, 1994). However, for the Only a few well preserved specimens of the stratigraphic interval above the reitzi zone this biostratigraphically relevant thin shelled bivalves succession lack a detailed ammonoid calibration. Daonella have been extracted from the Anisian/ Ladinian boundary interval in sections around Palynomorphs Bagolino. Of these, Daonella fascicostata was First results on palynomorphs from Buchenstein found in the upper secedensis zone just above the Beds of the Seceda core (Dolomites) along with Te-tuff layer at Prezzo. Figure 6a,b highlights the revised data from Val Gola suggest a distinct close match of the distribution of Daonella in other change in the microflora between assemblages South Alpine sections. In particular, the levels with observed in the Lower Plattenkalke (upper reitzi representatives of the group of Daonella elongata zone) and in the Knollenkalke corresponding to (D.serpianensis-angulata-caudata-elongata- the upper curionii zone (Hochuli & Roghi, 2002). airaghii) at M.S.Giorgio, Seceda and Val Gola are in excellent agreement. Because of the occurrence Magnetostratigraphy of undisputed representatives of the D. elongata- Samples taken for magnetostratigraphic analysis group in China (D. cf. airaghii) and in the meeki at Bagolino show remagnetised Tertiary zone of Nevada (Daonella cf. elongata; Silberling components (G. Muttoni, pers. commun.). & Nichols, 1982 and new unpublished own finds), However, the succession of magnetic reversals is these bivalves are of particular interest for far well established for almost the entire succession reaching correlation. of Buchenstein Beds in correlated sections in the No determinable Daonella are known so far from Dolomites (Muttoni et al., 1996, 1997, 2004; Brack the curionii zone. Higher up, different species of & Muttoni 2000) and at Val Gola (Gialanella et al.,

- 12 - GSSP of base of Ladinian

Bagolino e N n s i o u y A z e

65 c p i I a r l i l m i a N e e n i g I r u o n i r b t r u D a u . h g c . B A

64 . . r B E L GSSP g . )

Level B " e k l a a t

k 63 u n n e e l r l n o o o c n i z . K n " c ( ) a a s i e . c

62 i s a m s l r N r l n d e a e e i e r g d b a B b t n e e a i a n c l u i g t e . . h e n s t P B e e s .

61 f a n d N o r i e p u r h . o q c s a u e r N g B u a c n . e o r l 60 N a p o ( c i d A n ) u t . a r e a k p s l p s p i r a . r e . b p 59 e N . N p i c u m ( p . m e N a o l r t e . u f s P

58 i . s P n e y a e l n a

o 57 m z . i m z t " . i l s e r d G e . b R 56 l a n o i t i s n a

r 55 t " ) t r N a p r e A

w 54 o l ( I p u o S r

53 g I a e n i n i r e a a a o p t t n N e l i z s l o u s a t m e n s n . s r c e m A a P u o x r

52 a Bagolino s m t c e i r t o t ) L . s . d o f P o o o f

e additional sections from z n p a i . z ( r f . E-Lombardy / Giudicarie t f e . c r . a . N P P 51 . Dolomites N P

Figure 7: Detailed stratigraphic log of the Anisian/Ladinian boundary interval at Bagolino with the distribution of conodonts. Average sample spacing is around 18cm above and 50cm below the 58m- level respectively (for details see Brack & Nicora, 1998). Also shown are correlated complementary data from additional sections in eastern Lombardy (Brozzo, Pèrtica) and Giudicarie (Stabol Fresco) as well as in the Dolomites.

- 13 - GSSP of base of Ladinian 2001; see also discussion by Brack et al., 2001). realm (Aigner & Bachmann, 1992) may indeed In this record of magnetic reversals (Fig.6a), the correspond to a level at around or just above the proposed GSSP-level lies close to the base of base of the curionii zone (Brack et al., 1999). the reversed magnetozone SC2r.2r at Seceda and correlative magnetozones F1r.2r, P2r, M1r, at Cycle stratigraphy Frötschbach, Pedraces and Margon respectively. No cyclostratigraphic data are available for This magnetozone is preceded by the short normal Bagolino. polarity interval SC2r.1n (corresponding to Fr1r.1n The spectral analysis of bedding rhythms in distinct and P2n). intervals of Buchenstein Beds of the Seceda core The new data from the Seceda core (Muttoni et and section (Maurer et al., in press.) may point al., 2004) not only confirm the previous results to the existence of hierarchical stacking patterns but also provide a stratigraphic expansion of this possibly related to variations in orbital parameters. record. Remarkable is the existence of a long zone If confirmed and extended, these results could of reversed polarity in the Lower Plattenkalke potentially provide a significant refinement of the below the base of the secedensis zone (Ticinites age resolution in the Knollenkalk-interval of the horizon). The comparison with the Hungarian data Buchenstein Beds, i.e. from the secedensis zone as reported in Vörös et al. (2003) casts doubts on upwards and including the proposed GSSP-level. the reliability of a long normal polarity interval in the corresponding interval at Felsöörs (upper part Tephrastratigraphy of Vàszoly Fm.). At Bagolino volcaniclastic layers occur in the uppermost Prezzo Limestone and throughout the Chemical stratigraphy entire Buchenstein succession as a few millimetres No systematic studies on stable isotopes and up to a few decimetres thick acidic ash beds other chemical markers are available for often with a greenish colour (“Pietra verde”). In Bagolino. Unpublished results of a pilot study the Buchenstein Beds the volcaniclastic layers of stable isotopes (C, O) on 30 outcrop samples show increased frequencies in three stratigraphic evenly distributed over the entire succession of intervals. Individual beds and characteristic stacks Buchenstein Beds at Seceda show lithology- of layers can be traced over tens of kilometres related variation in the carbon isotopes (R. Abart, and have been identified as far away as in the pers. commun.). Throughout the entire column Dolomites and Southern Switzerland (Fig.6a,b; no significant excursion is evident in the oxygen see also figs.7,10,11 in Brack & Rieber, 1993 isotopes with a mean value of ∂18O(PDB) of - and figs.2,3,11 in Brack & Muttoni, 2000) The 2.82+/-0.78‰. 87Sr/86Sr-ratios of conodonts from lateral persistence of volcaniclastic layers points the secedensis to curionii zone interval in equivalent to an airborne origin of the silt to sand-sized ash Buchenstein-type lithologies (Knollenkalke) in particles, probably originating from eruption Hungary (Felsöörs, Köveskal) fall in the range centres outside the present Southern Alps. between 0.707664-0.707716, with a tendency Beyond their occurrences in South Alpine basinal of (stratigraphically) upwards decreasing values sediments and platform interior carbonates (e.g., (Korte et al., 2003). at Latemar; Mundil et al., 2003), comparable volcaniclastic ash layers are well known and show Sequence stratigraphy potential for isotopic age dating and stratigraphic The deposition of the pelagic Buchenstein correlation in the Reifling Beds of the Eastern Alps Beds occurred in deep marine conditions. The as well as in sedimentary successions further afield age calibration of platform-basin settings in (e.g., Hungary, Dinarids, Greece). the Dolomites (Maurer 1999, 2000; Brack & Muttoni, 2000) indicates a maximum basin depth Geochronometry close to the base of the curionii zone (i.e. close High-resolution U-Pb age data obtained on single to the proposed GSSP-level). Comparison of zircon grains from volcaniclastic layers are the pelagic successions of the Southern Alps available for four distinct stratigraphic horizons in with the Germanic Middle Triassic suggests that Buchenstein and corresponding layers at Bagolino, the “Cycloides gamma”-horizon identified as Seceda and M.S.Giorgio (Figs.3,5,6; Mundil et al., a maximum flooding surface in the Germanic 1996; Brack et al, 1996). The proposed GSSP-

- 14 - GSSP of base of Ladinian level is bracketed by the age values for the Tc-tuff Ladinian boundary at Bagolino and in the interval (secedensis zone; SEC.22: 241.2+0.8/- condensed section of red Hallstatt-type limestone at 0.6Ma and MSG.09: 241.2±0.8Ma; uncertainties Epidavros (Krystyn, 1993; unpublished own data) at 95% confidence level) below and for a are also in good agreement (e.g., representatives volcaniclastic layer with accretionary lapilli at the of Kellnerites, Nevadites, Chieseiceras, 72.2m-level of Bagolino (BAG.06a: 238.8+0.5/- Eoprotrachyceras, Arpadites). The proposed 0.2Ma) above. Sanidine Ar-Ar data (239.3±0.6Ma, GSSP-level can be identified but the comparison obtained by incremental CO2 laser heating of also suggests particularly strong condensation in approximately 100 grains; Renne et al., in prep.) of the curionii zone interval at Epidavros. the lower level (secedensis zone) with U-Pb data The correlation of South Alpine pelagic successions at M.S.Giorgio conform with the ca. 1% age bias (including Bagolino) with the Germanic Middle between the Ar-Ar and U-Pb geochronometric Triassic is discussed in Brack et al. (1999). A systems (e.g., Min et al., 2000). Moreover, the detailed fossil-based correlation is hampered by error bars of the zircon ages of this level overlap endemism of the faunas in the Germanic upper with multigrain U-Pb-ages from stratigraphically Muschelkalk. The resulting old correlation problem somewhat older tuff layers at Felsöörs (Pálfy et al., might be overcome in future by the recognition of 2003; Vörös et al., 2003). An independent U-Pb corresponding magnetic reversals in Muschelkalk zircon study on crystals from volcaniclastic layers successions. To date, magnetostratigraphic results in South Alpine Buchenstein sections (including are available only for an incompletely preserved Bagolino) yields results which are in agreement succession of upper Muschelkalk in Poland with the above mentioned U-Pb data (S. Bowring, (Navrocki & Szulc, 2000). This record ends pers. commun.). presumably at around the proposed GSSP-level. Correlations of South Alpine sections with Regional and global correlation sediment successions in North America are The accurate litho-, tephra- and biostratigraphic discussed in Brack & Rieber (1994) and Bucher correlation of Anisian/Ladinian boundary intervals & Orchard (1995). In the Anisian/Ladinian of sections in the Brescian Prealps (including boundary interval the correlation is established Bagolino) and Giudicarie has been discussed on the basis of corresponding ammonoid genera above. With a comparable bed-scale resolution, (Nevadites, Eoprotrachyceras), Daonella (D. distinct intervals of Buchenstein Beds in the elongata-gp.) and conodonts (N. constricta + N. Dolomites have been correlated on the basis of alpina, N. praehungarica, P. (aff.) fueloepi). These stratal patterns and magnetostratigraphy (Brack & elements document the close correspondence of Muttoni, 2000; Muttoni et al., 2004). Selected key the interval upper reitzi zone - curionii zone of sections from these areas and Southern Switzerland western Tethys with the upper part of the meeki are shown in Fig.6a,b and comprise the most zone - lower subasperum zone of Nevada. In important macrofossils, magnetic reversals and North America (Nevada, British Columbia) the lithostratigraphic markers (see Brack & Rieber, proposed GSSP-level is recognised by the onset 1993; Brack et al., 2001 for additional information of representatives of the genus Eoprotrachyceras. and references). Tozer (1994b) emphasized that a base of the The comparison of ammonoids also documents Ladinian at a stratigraphically deeper level would a good correspondence of fossils (ammonoids, be unrecognizable in British Columbia. Because conodonts) below the Ticinites horizon at of the affinities of ammonoids with those of the Bagolino and in the Balaton Highland (e.g., Arctic and also with those of Nevada, the Triassic Felsöörs; Figs.6b,8). The apparent expansion successions of northeastern British Columbia of the stratigraphic interval of the reitzi zone at are of crucial importance for the biostratigraphic Felsöörs (Vörös, 1998; Vörös et al., 2003) is due to link with the Arctic Middle Triassic (Dagys & dilution with abundant volcaniclastic material. The Weitschat, 1993). Nevertheless, a precise macro- cumulative thickness of fossil-bearing limestone and microfossil-based correlation of upper Anisian layers is comparable in both sections (Fig.8). The to lower Ladinian successions at low latitudes proposed GSSP-level (i.e. the base of curionii and in the Arctic realm are still problematic zone) has not yet been identified at Felsöörs. and magnetostratigraphy has to our knowledge The ammonoid records straddling the Anisian/ not been established with sufficient detail in

- 15 - GSSP of base of Ladinian Bed no. 136 Bagolino (Southern Alps) Felsöörs (Balato1n34 Highland) 136 132 65 Eoprotrachyceras recubariense column original column Eoprotrachyceras rieberi with 134 (grey areas = Chieseiceras perticaense limestone v1o2l9caniclastics) Chieseiceras perticaense 132 beds 126 only GSSP Eoprotrachyceras curionii 129 125 122 Chieseiceras chiesense 126 Stoppaniceras' (ellipticum-gr.) 125 120 Nevadites avenonensis (Pe) 122 Nevadites sp. 119 "Stoppaniceras" ex gr. ellipticum 118 Halilucites cf. arietitiformis (Pe) 120 Repossia sp. 'Stoppaniceras' 117 Chieseiceras sp. 119 Chieseiceras sp. ellipticum-gr. (FO) 116 'Stoppaniceras' (ellipticum-gr.) 115 Stoppaniceras cf. variabile 116 114 Nevadites sp. (Pr) 113 Halilucites cf. obliquus Halilucites cf. obliquus 112 Ticinites 112 Ticinites cf. crassus Ticinites brescianus KJ K 60 J Ticinites hantkeni Parakellnerites aff. boeckhi I Aplococeras sp. Stoppaniceras sp. E H Halilucites rusticus G Parakellnerites hungaricus Halilucites rusticus A111 F Lecanites misanii 110 Halilucites cf. costosus E Halilucites rusticus Hungarites zalaensis 107 D Aplococeras avisianum 105 C Halilucites cf. arietitiformis "Megaceratites" B 102 A Hungarites mojsisovicsi Parakellnerites arthaberi 101 111 Latemarites latemarensis Reitziites reitzi 110 Parakellnerites arthaberi Reitziites reitzi 100 Reitziites reitzi 100A 100E Kellnerites bagolinensis Kellnerites bagolinensis 100F Kellnerites bagolinensis corresponding to: 99C 109 Ceratitidae cf. hungaricus Hyparpadites 99B Kellnerites bagolinensis Ta-Tuffs 99A 108 f

55 Kellnerites bosnensis o 99 s s

Kellnerites angustecarinatus e e i

t 97 c i 107 r Kellnerites bosnensis, K. angustecarinatus e e p s K. fissicostatus, Hungarites lenis n l l r e 'Hungarites' cf. lenis a l i Ceratitidae cf. hungaricus K 106 m i Kellnerites halilucensis s Norites gondola Lardaroceras aff. pseudohungaricum (Pe) Lardaroceras aff. krystyni (Pe) Lardaroceras / Asseretoceras Parakellnerites cf. boeckhi CG-Tuffs Asseretoceras camunum -hor. 105 at Contrada Gobbia (= CG Nr.5) All columns at Reitziites reitzi and Stabol Fresco (= SF Nr.105a) same scale! [m] in Balini et al. (1993). 104

103

102

Figure 8: Comparison of stratigraphic sections at Bagolino and Felsöörs (original column from Vörös et al., 2003; reduced column was obtained by eliminating grey shaded Hyparpadites aff. liepoldti areas representing tuffaceous intervals, i.e. deposits of short-lived volcanic events). Note 101 that the stratigraphic thickness of distinct intervals of pelagic limestone at Bagolino is similar or even exceeds the corresponding 100 values in the Felsöörs column. In particular, the limestone interval between the beds with Reitziites reitzi and the layer with Halilucites 100A 100B Kellnerites cf. bispinosus rusticus (marked by arrows) is thicker at 100C Bagolino, suggesting condensation or a 100E Kellnerites felsoeoersensis stratigraphic gap in the Felsöörs section Kellnerites cf. bispinosus immediately above the base of the reitzi 100F Kellnerites sp. zone. 2 "Hungarites" inconstans 99C Lardaroceras pseudohung. 1 99B Asseretoceras sp. 99A 99 0 98 m 97

- 16 - GSSP of base of Ladinian Arctic intervals. Conversely, the correlation of the species of Aplococeras as bearing too few stratigraphic sequences between low and high distinctive characters for a ready identification. In latitude successions still lacks sufficiently precise agreement with Silberling & Nichols (1982), we age control. repeat our conviction that the Tethyan ammonoid Elsewhere, fossiliferous pelagic sediment A. avisianum and the North American Lecanites successions straddling the Anisian/Ladinian vogdesi are not co-specific. Unfortunately, Site C boundary seem to be quite rare. At present we are proposed by Mietto et al. (2003b) as GSSP-section unaware of successions with appropriate records at Bagolino is now partly covered by a recent of either ammonoids, Daonella or conodonts. landslide. Himalayan successions (e.g. Spiti) seem not to bear Older alternatives for the Anisian/Ladinian ammonoids attributable to the upper secedensis to boundary are indicated in Fig.6b (1b and 2b) but curionii zone. Daonella and/or ammonoids of this have been rejected for similar reasons, i.e. the interval presumably occur in places throughout restricted distributions of key taxa (Kellnerites, south-east Asia (e.g., Vietnam) but hitherto Ticinites) used in their definitions. lack appropriate stratigraphic and paleontologic documentation. Daonella-bearing marine Acknowledgments: sediments of Middle Triassic age and from higher- We would like to thank all people involved in the paleolatitudes are known from volcaniclastic-rich long process of defining the base of the Ladinian successions in New Zealand. for stimulating discussions and scientific and moral If confirmed and properly positioned with respect support. In 1993, M. Gaetani initiated the formal to the proposed GSSP-level, the distinct change discussion and decision process. Later on A. Baud in microflora assemblages observed between the led the Anisian/Ladinian boundary working group upper reitzi zone and the upper curionii zone in whose discussions significantly contributed to the Seceda and associated sections (Hochuli & Roghi, current proposal. STS-chairman Mike Orchard and 2002) may have potential for correlation of marine ICS-officer James G. Ogg thoroughly reviewed and non-marine sections of comparable climate this proposal. zones.

References: OTHER CANDIDATES AND REASONS FOR (Several key references describing aspects of the REJECTION Bagolino stratigraphy are marked with an asteriks). Two alternative formal proposals for the GSSP of Muttoni et al. (2004) provide the most up-to-date the base of the Ladinian Stage have been published stratigraphic information on the auxiliary section in Albertiana 28 (marked 1 and 2 in Fig.6b). at Seceda including the reference succession of Vörös et al. (2003) advocate a GSSP at the base magnetic reversals). of the reitzi zone with a repositioned base, i.e. at layer 105 in the Felsöörs section. Unambiguous Aigner, T. & Bachmann, G.H., 1992. Sequence specimens of Reitziites reitzi have been documented stratigraphic framework of the German so far only from Hungary and from the Southern Triassic. Sed. Geol., 80: 115-135. Alps. Moreover, no species assigned to Reitziites Arthaber, G.v., 1906. Die alpine Trias des have as yet been indicated from sections in North Mediterran-Gebietes. In: Lethaea geognostica, America or Canada. Therefore we consider the pt.2 (ed. by Frech, F.). Das Mesozoicum 1 distribution of Reitziites as being too restricted (Trias), 223-475. and unsuitable for a GSSP definition. Finally, Balini, M., 1998. Taxonomy, stratigraphy and the comparison of the Felsöörs section with the phylogeny of the new genus Lanceoptychites Bagolino column (Fig.8) documents the existence (Ammonoidea, Anisian). Riv. It. Paleont. of a strongly condensed or even incomplete Strat., 104(2): 143-166. interval immediately above the Reitziites horizons Balini, M. 2003. The Proposals for the GSSP at Felsöörs. of the Ladinian stage: pros and cons of a Mietto et al. (2003b) propose the GSSP at the base complex choice. Comment circulated among of their avisianum subzone at Bagolino. For reasons members of the A/L boundary working group given in Brack & Rieber (2003) we still consider and Albertiana, 28: 48-53.

- 17 - GSSP of base of Ladinian Balini, M., Gaetani, M. & Nicora, A., 1993. of the Middle Triassic Margon section Excursion Day 2: In Gaetani M. (ed)., (Southern Alps, Italy)ʼ by P.R. Gialanella. Anisian/ Ladinian boundary field workshop F. Heller, P. Mietto, A. Incoronato, V. De Southern Alps - Balaton Highlands, 27 June Zanche, P. Gianolla, G. Roghi [Earth Planet. - 4 July 1993; Field-guide book. I.U.G.S. Sci. Lett. 187 (2001) 17-25]. Earth Planet. Subcommission of Triassic Stratigraphy; 43- Sci. Lett. 193(1-2): 255-257. 54. *Brack, P., Rieber, H. & Mundil, R., 1995. The Bittner, A., 1881. Über die geologischen Anisian/Ladinian boundary interval at Aufnahmen in Judikarien und Val Sabbia. Jb. Bagolino (Southern Alps, Italy): I. Summary k.k. geol. Reichsanst., 31(3): 219-370. and new results on ammonoid horizons and Bittner, A., 1892. Was ist norisch? Jb. k.k. geol. radiometric age dating. Albertiana, 15: 45- Reichsanst., 42(3): 387-396. 56. Brack, P. & Muttoni, G., 2000. High-resolution *Brack, P., Rieber, H. & Nicora, A., 2003. The magnetostratigraphic and lithostratigraphic Global Stratigraphic Section and Point (GSSP) correlations in Middle Triassic pelagic for the base of the Ladinian Stage (Middle carbonates from the Dolomites (northern Triassic). A proposal for the GSSP at the base Italy). Palaeogeogr., Palaeoclim., Palaeoecol., of the Curionii Zone in the Bagolino section 161(3-4): 361-380. (Southern Alps, Northern Italy). Albertiana, *Brack, P. & Nicora, A., 1998. Conodonts from 28: 13-25. the Anisian-Ladinian succession of Bagolino, Brack, P., Rieber, H. & Urlichs, M., 1999. Pelagic Brescian Prealps (Brescia, Lombardy, successions in the Southern Alps and their Northern Italy). Giorn. Geol., ser.3, 60, 1998, correlation with the Germanic Middle Spec. Issue, ECOS VII- Southern Alps Field Triassic. Zbl. Geol. Paläont. Teil I (1998), H. Trip Guidebook, 314-325. 7-8: 853-876. *Brack, P. & Rieber, H., 1986. Stratigraphy and Brack, P., Schlager, W., Stefani, M., Maurer, Ammonoids from the lower Buchenstein F. & Kenter, J., 2000. The Seceda Drill Beds in the Brescian Prealps and Giudicarie Hole in the Middle Triassic Buchenstein and their significance for the Anisian/Ladinian beds (Livinallongo Formation, Dolomites, boundary. Eclogae geol. Helv., 79: 181-225. Northern Italy) - a progress report. Riv. It. *Brack, P. & Rieber, H., 1993. Towards a better Paleont. Strat., 106(3): 283-292. definition of the Anisian/Ladinian boundary: Bucher, H. & Orchard, M.J., 1995. Intercalibrated New biostratigraphic data and correlations ammonoid and conodont succession, Upper of boundary sections from Southern Alps. Anisian- Lower Ladinian of Nevada. Eclogae geol. Helv., 86: 415-527. Albertiana, 15: 66-71. Brack, P. & Rieber, H., 1994. The Anisian/Ladinian Dagys, A. & Weitschat, W., 1993. Correlation of boundary: retrospective and new constraints. the Boreal Triassic. Mitt. Geol.-Paläont. Inst. Albertiana, 13: 25-36. Univ. Hamburg., 75: 249-256. Brack, P. & Rieber, H., 1996. The new “high *Gaetani, M. (ed.), 1993. Anisian/Ladinian resolution Middle Triassic Ammonoid standard boundary field workshop Southern Alps - scale” proposed by Triassic researchers from Balaton Highlands, 27 June - 4 July 1993; Padova - A discussion of the Anisian/Ladinian Field-guide book. I.U.G.S. Subcommission boundary interval. Albertiana, 17, 43-50. of Triassic Stratigraphy; 118 pp. Brack, P. & Rieber, H., 2003. Proposals for the Gialanella, P.R., Heller, F., Mietto, P., Incoronato, GSSP for the base of the Ladinian Stage: A., De Zanche, V., Gianolla, P. & Roghi, Comment. Albertiana, 28: 54-55. G., 2001. Magnetostratigraphy and Brack, P., Mundil, R., Oberli, F, Meier, M. & Rieber, biostratigraphy of the Middle Triassic Margon H. 1996. Biostratigraphic and radiometric age section (Southern Alps, Italy). Earth Planet. data question the Milankovitch characteristics Sci. Lett. 187: 17-25. of the Latemar cycles (Southern Alps, Italy). Hochuli, P.A. & Roghi, G., 2002. A palynological Geology, 24(4): 371-375. view on the Anisian/Ladinian boundary - new Brack, P., Muttoni, G. & Rieber, H., 2001. Comment results from the Seceda section (Dolomites, on: ʻMagnetostratigraphy and biostratigraphy Northern Italy). STS/IGCP 467 field meeting,

- 18 - GSSP of base of Ladinian Veszprém, Hungary, 5-8 September, 2002. Italy). Sedimentology, 50: 1-22. Geological Institute of Hungary; Abstract Maurer, F., Hinnov, L. & Schlager, W., (in volume, 29-30. press), Statistical time series analysis and Korte, C., Kozur, H.W., Bruckschen, P. & Veizer, sedimentological tuning of bedding rhythms J., 2003. Strontium evolution of Late Permian in a Triassic basinal succession (Southern and Triassic seawater. Geochim. Cosmochim. Alps, Italy). SEPM spec. publ. Acta, 67(1): 47-62. *Mietto, P., Gianolla, P., Manfrin, S. & Preto, Kovács, S., Nicora, A., Szabó, I. & Balini, M., N., 2003a. Refined ammonoid biochrono- 1990. Conodont biostratigraphy of Anisian/ stratigraphy of the Bagolino section Ladinian boundary sections in the Balaton (Lombardian Alps, Italy), GSSP candidate Upland (Hungary) and in the Southern Alps. for the base of the Ladinian Stage. Riv. It. Courier Forsch. Inst. Senckenberg, 118: 171- Paleont. Strat., 109/3: 449-462. 195. Mietto, P. & Manfrin, S., 1995. A high resolution Kozur, H., 1995. Remarks on the Anisian/Ladinian Middle Triassic ammonoid standard scale in boundary. Albertiana, 15: 36-44. the Tethys realm. A preliminary report. Bull. Kozur, H. & Mostler, H., 1994. Anisian to middle Soc. Géol. Fr., 166(5): 539-563. Carnian radiolarian zonation and description of Mietto, P., Manfrin, S., Preto, N., Gianolla, P., some stratigraphically important radiolarians. Krystyn, L. & Roghi, G., 2003b. Proposal of Geol. Paläont. Mitt. Innsbruck, spec. vol. 2: the Global Stratigraphic Section and Point 39-255. (GSSP) for the base of the Ladinian Stage Krystyn, L., 1983. Das Epidaurus-Profil (Middle Triassic) - GSSP at the base of the (Griechenland) - ein Beitrag zur Conodonten- Avisianum Subzone (FAD of Aplococeras Standardzonierung des tethyalen Ladin und avisianum) in the Bagolino section (Southern Unterkarn. In: Zapfe (Ed.): Neue Beiträge zur Alps. NE Italy). Albertiana, 28: 26-34. Biostratigraphie der Tethys-Trias. Schriftenr. Min K.W., Mundil R., Renne P.R. & Ludwig K.R., erdwiss. Komm. österr. Akad. Wiss., 5: 231- 2000. Test for systematic errors in Ar-40/Ar-39 258. geochronology through comparison with U/ Manfrin, S., Mietto, P. & Preto, N., (submitted). Pb analysis of a 1.1-Ga rhyolite. Geochimica Ammonoid biostratigraphy of the Middle Cosmochimica Acta, 64(1): 73-98. Triassic Latemar platform (Dolomites, Italy) Mojsisovics, E.v., 1874. Faunengebiete und and its correlatioin with Nevada and Canada. Faciesgebilde der Trias-Periode in den Ost- Geobios. Alpen. Jahrb. k.k. geol. Reichsanst., 24(1):81- Mariani, E., 1906. Alcune osservazioni geologiche 134. sui dintorni di Bagolino nella Valle del Mojsisovics, E.v., 1882. Die Cephalopoden der Caffaro. Rend. Ist. lomb. Sci. [Lett., Ser. 2], mediterranen Triasprovinz. Abh. k.k. geol. 39(14): 646-653. Reichsanst., 10, 322pp. Maurer, F., 1999. Wachstumsanalyse einer Mojsisovics, E.v., Waagen, W. & Diener, C., 1895. mitteltriadischen Karbonatplattform in den Entwurf einer Gliederung der pelagischen westlichen Dolomiten (Südalpen). Eclogae Sedimente des Trias-Systems. Sitzber. k. geol. Helv., 92: 361-378. Akad. Wiss. Wien, 104(1): 1271-1302. Maurer, F., 2000. Growth mode of Middle Triassic *Mundil, R., Brack, P., Meier, M., Rieber, H. & carbonate platforms in the Western Dolomites Oberli, F., 1996. High resolution U-Pb dating (Southern Alps, Italy)., Sed. Geol., 134: 275- of Middle Triassic volcaniclastics: Time- 286. scale calibration and verification of tuning Maurer, F. & Rettori R., 2002. Middle Triassic parameters for carbonate sedimentation. Earth foraminifera from the Seceda core (Dolomites, Planet. Sci. Lett., 141: 137-151. Northern Italy). Riv. It. Paleont. Strat., 108(3): Mundil, R., Zühlke, R., Bechstädt, T., Peterhänsel, 391-398. A., Egenhoff, S.O., Oberli, F., Meier, M., Maurer, F. & Schlager W., 2003. Lateral variations Brack, P. & Rieber, H., 2003. Cyclicities in in sediment composition and bedding Triassic platform carbonates: synchronizing in Middle Triassic interplatform basins radio-isotopic and orbital clocks. Terra Nova, (Buchenstein Formation, Southern Alps, 15: 81-87.

- 19 - GSSP of base of Ladinian Muttoni, G., Kent, D.V., Brack, P., Nicora, Eclogae geol. Helv., 94(3):389-398. A. & Balini, M., 1997. Middle Triassic Silberling, N.J. & Nichols, K.M., 1982. Middle magnetostratigraphy and biostratigraphy Triassic molluscan fossils of biostratigraphic from the Dolomites and Greece. Earth Planet. significance from Humboldt range, Sci. Lett., 146: 107-120. Northwestern Nevada. Prof. Pap. U.S. geol. Muttoni, G., Kent, D.V., Nicora, A., Rieber, H. Surv., 1207: 1-77. & Brack, P., 1996. Magneto-biostratigraphy Tozer, T., 1994a. Canadian Triassic ammonoid of the “Buchenstein Beds” at Frötschbach faunas. Geol. Surv. Canada Bull., 467:1-663. (Western Dolomites, Italy). Albertiana, 17: Tozer, T., 1994b. Significance of Triassic stage 51-56. boundaries defined in North America. Mém. *Muttoni, G., Nicora, A., Brack, P. & Kent, D.V. de Géologie (Lausanne), 22: 155-170. 2004. Integrated Anisian/Ladinian boundary Vörös, A., 1998. A Balaton-felvidék Triás chronology. Palaeogeogr., Palaeoclim., ammonoideái és biostratigrádiája. Studia Palaeoecol., 208: 85-102. Naturalia no. 12, Magyar Természettudományi Navrocki, J. & Szulc, J., 2000. The Middle Triassic Múzeum, Budapest, 105 pp. magnetostratigraphy from the Peri-Tethys Vörös, A., Budai, T., Haas, J., Kovács, S., Kozur, basin in Poland. Earth Planet. Sci. Lett., 182: H. & Pálfy J., 2003. GSSP (Global Boundary 77-92. Stratotype Section and Point) Proposal for the Nicora, A. & Brack, P., 1995. The Anisian/ base of the Ladinian (Triassic) A proposal for Ladinian boundary interval at Bagolino the GSSP at the base of the Reitzi Zone (sensu (Southern Alps, Italy): II. The distribution of stricto) at Bed 105 in the Felsöörs section, Conodonts. Albertiana, 15: 57-65. Balaton Highland, Hungary. Albertiana, 28: Nicora, A. & Brack, P, (in prep.). The conodont 35-47. distribution in upper Anisian - Ladinian Vörös, A., Szabó, I., Kovács, S., Dosztály, L. successions (Buchenstein Beds) with & Budai, T., 1996. The Feloörs section: A ammonoid control in eastern Lombardy and possible stratotype for the base of the Ladinian Giudicarie (Southern Alps, Northern Italy). Stage. Albertiana, 17: 25-40. Orchard, M.J. & Tozer, E.T., 1997. Triassic conodont biochronology, its calibration with the ammonoid standard, and a biostratigraphic summary for the Western Canada sedimentary basin. Bull. Canad. Petrol. Geol., 45(4): 675- 692. Pálfy, J., Parrish, R.R. & Vörös, A., 2003. Mid- Triassic integrated U-Pb geochronology and ammonoid biochronology from the Balaton Highland (Hungary). J. Geol. Soc. London, 160: 271-284. Rieber, H. & Brack, P., 2002. The systematic position of Nevadites and (bio)stratigraphic implications. STS/IGCP 467 field meeting, Veszprém, Hungary, 5-8 September, 2002. Geological Institute of Hungary; Abstract volume, 24-25. Schatz, W., 2001a. Taxonomic significance of biometric characters and the consequences for classification and biostratigraphy, exemplified through moussoneliform daonellas (Daonella, Bivalvia; Triassic). Paläontolog. Zeitschr., 75(1): 51-70. Schatz, W., 2001b. Revision der Untergattung Daonella (Pichlerella) (Bivalvia, Ladin).

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