Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

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Palaeogeography, Palaeoclimatology, Palaeoecology

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New magnetobiostratigraphic results from the Ladinian of the Dolomites T and implications for the Triassic geomagnetic polarity timescale ⁎ Matteo Marona, , Giovanni Muttonia, Manuel Rigob,c, Piero Gianollad, Dennis V. Kente,f a Department of Earth Sciences “Ardito Desio”, University of Milano, via Mangiagalli 34, 20133 Milano, Italy b Department of Geosciences, University of Padova, via Gradenigo 6, 35131 Padova, Italy c Institute of Geosciences and Earth Resources, Consiglio Nazionale delle Ricerche (CNR), via Gradenigo 6, 35131 Padova, Italy d Department of Physics and Earth Sciences, University of Ferrara, via Saragat 1, 44122 Ferrara, Italy e Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA f Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA

ARTICLE INFO ABSTRACT

Keywords: We investigated for magnetostratigraphy the Rio Nigra and Rio Frommer stratigraphic sections from Alpe di Magnetostratigraphy Siusi/Seiser Alm (Dolomites, northern Italy) in order to improve the calibration of the Triassic time scale. Both Geochronology sections are characterized by ammonoid and conodont associations typical of Longobardian (late Ladinian, Middle Triassic Middle Triassic) age. Moreover, the Rio Nigra section is constrained by a U-Pb zircon date of 237.77 ± 0.05 Ma. U-Pb dating Building on the recently verified Newark-Hartford astrochronological polarity timescale for the Late Carnian–Rhaetian (plus the Hettangian) and through magnetostratigraphic correlations of an updated inventory of Tethyan marine stratigraphic sections from the literature, some of which are provided with U-Pb zircon age constraints, we propose a revised Geomagnetic Polarity Time Scale for the entire Triassic.

1. Introduction Rio Nigra section, in conjunction with available geochronological data from the late Ladinian–Carnian and estimates of regional sediment The continuous addition of relevant magnetostratigraphic, radio- accumulation rates, to derive an age of ~237 Ma for the Carnian base, metric, and astrochronologic age data warrant an update of the Triassic older than in previous timescales (e.g., Hounslow and Muttoni, 2010). geomagnetic polarity timescale (GPTS). An astrochronological polarity The aim of this study was to improve the chronology of the Middle timescale (APTS) for the Early–Middle Triassic has been recently ob- Triassic by conducting a magnetostratigraphic study of the U-Pb-cali- tained through astronomically-tuned magnetostratigraphic sections brated Rio Nigra section as well as of the largely coeval Rio Frommer from South China (Li et al., 2016, 2018). The magnetostratigraphy of section from the Dolomites. These new data are used in conjunction the Late Triassic has been improved with studies at Pignola-2 (Carnian; with data from a selection of 33 Tethyan marine sections (Fig. 1A, B) Maron et al., 2017), Wayao (Carnian; Zhang et al., 2015), and Pignola- from the literature (10 of them from the Southern Alps; Fig. 2A), con- Abriola (Norian–Rhaetian; Maron et al., 2015; Rigo et al., 2016), and strained by an updated inventory of radiometric age data and key their correlations to the reference Newark-Hartford APTS (Carnian–- biostratigraphic events useful to define stage boundaries, to construct Hettangian; e.g., Kent et al., 2017), which has been recently confirmed an updated GPTS spanning from the recently recalibrated age of the by new U-Pb zircon dates from the Petrified Forest drill core (Kent Permian/Triassic boundary (Burgess et al., 2014) to the Carnian (Late et al., 2018). The central thread of the Middle Triassic GPTS derives Triassic). This GPTS is then appended to the Late Triassic Newark APTS from radiometrically-calibrated magnetostratigraphic sections in the (Kent et al., 2017 and references therein; Fig. 1A, B) where stage Dolomites of northern Italy (e.g., Muttoni et al., 2004a), where addi- boundaries are defined by correlations to Tethyan marine sections some tional U-Pb zircon dates have recently become available from tuff layers of which of recent publication. Our Triassic GPTS is then discussed in at Seceda (239.04 ± 0.10 Ma, 240.28 ± 0.09 Ma, 240.58 ± 0.13 Ma; comparison with previous timescales (e.g., Szurlies, 2007; Hounslow Wotzlaw et al., 2018) and Rio Nigra (237.77 ± 0.05 Ma; Mietto et al., and Muttoni, 2010; Li et al., 2018). 2012). In particular, Mietto et al. (2012) used the U-Pb date from the

⁎ Corresponding author. E-mail addresses: [email protected] (M. Maron), [email protected] (G. Muttoni), [email protected] (M. Rigo), [email protected] (P. Gianolla), [email protected] (D.V. Kent). https://doi.org/10.1016/j.palaeo.2018.11.024 Received 11 July 2018; Received in revised form 2 November 2018; Accepted 21 November 2018 Available online 23 November 2018 0031-0182/ © 2018 Elsevier B.V. All rights reserved. M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Fig. 1. Panel A: Global map with the location of the stratigraphic sections discussed in the text. Panel B: Paleogeographic reconstruction of Pangea and the Tethys Ocean in the earliest Late Triassic at ∼225 Ma (from Muttoni et al., 2015). Due to general north- ward motion of Pangea during the Triassic, strati- graphic sections older than 225 Ma, such as the Early Triassic sections from South China, were located closer to the paleoequator. Magnetostratigraphic sections discussed in the text are indicated by num- bers (legend in figure).

8°E 12°E 3 4 5 B Creek N N 0 1 2 Km 0 20 40 Km 6 2 Siusi Pathway Bolzano 1 N Compaccio (Bozen) Dolomites 7 Road ITALY N 46°32’ Rio Frommer

44°N 46°N Town Belluno Sciliar-Catinaccio Rio Freddo section Trento 0 250 Km Nature Park Mountain 8 ALPE 10 Lombardy Peak Alps Rio Nigra DI 46°31’ N 46°31’ section Stratigraphic 46°N 9 SIUSI Mt. Sciliar Section

Bergamo Garda Lake 11°33’ E 11°35’ E 11°37’ E Venezia C Volcanites Brescia (Fernazza Fm.) Verona Padova Adriatic Frommer mb. Sea (Fernazza Fm.) A Po Plain Sciliar Fm. (Sciliar III) 10°E 11°E 12°E RIO FROMMER (~38 m) Marmolada Cgm. River Sea/Lake City Stratigraphic Section RIO NIGRA (Wengen Fm.) (~38 m) 1 - Rio Nigra/Rio Frommer; 2 - Frotschbach; 3 - Bulla/Siusi; 4 - Seceda; Wengen Fm. 5 - Pedraces; 6 - Prati di Stuores; 7 - Belvedere; 8 - Margon; 9 - Italcementi Quarry; 10 - Brumano Erosive Surface

Fig. 2. Panel A: Map of north-eastern Italy, with position of the main stratigraphic sections from the Southern Alps. Panel B: Map of the Alpe di Siusi/Seiser Alm area, Dolomites, Italy. The Rio Frommer stratigraphic section is located near the village of Compaccio/Compatsch and the Rio Nigra section closer to the Sciliar/Schlern massif, within the Sciliar-Catinaccio/Schlern-Rosengarten Nature Park. Panel C: Stratigtraphic framework of Alpe di Siusi in which are represented the boundaries between the Fernazza Fm. (Volcanites and Frommer member), the Sciliar Fm., and the Wengen Fm. (including the Marmolada Conglomerate).

2. Stratigraphy of Rio Nigra and Rio Frommer sections Schlern along the Rio Nigra Creek (Fig. 2B). The section is ~38 m-thick and straddles the Frommer member of the Fernazza Formation The Rio Nigra section (coordinates: 46° 30′ 56.1″ N; 11° 35′ 43″ E) is (Gianolla et al., 1998; Stefani et al., 2010; Mietto et al., 2012; Bernardi located in the Alpe di Siusi on the north-eastern flank of Mount Sciliar/ et al., 2018)(Fig. 3A). It starts with pillow lavas at the base overlain by

53 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Rio Nigra section

D. Magnetostratigraphy A. Lithostratigraphy B. Biostratigraphy C. Thickness IRM0.3/SIRM (m) Declination Inclination VGP Latitude Scilliar Fm 38 CNI 1 36 RNM 31.53 RNM 31.00 34 Frankites regoledanus RNM 30.00 CNI 2 RNM 28.69 32 RNM 27.74 RN2n CNI 3 30

CNI 4 Zestoceras nitidum cf. RNM 24.60 28

CNI 5 26 RNM 22.86 237.77 ± 0.05 Ma RNM 21.60 24 RN1r.1n RNM 20.80 RN1r 22

20

CNI 6 Paragondolella foliata RNM 16.61 RNM 15.89 18 Gladigondolella tethydis RNM 15.28 Pseudofurnishius murcianus murcianus RN1n.2r RNM 14.47 16

RNM 13.68 Frommer mbr RNM 12.99 RN1n.1r FernazzaFm Budurovignathus diebeli RNM 12.38 14 Paragondolella inclinata RNM 11.45 RNM 10.01 12 RNM 9.22 RNM 7.92 10

RNM 7.34 Budurovignathus sp. RN1n RNM 7.00 8

RNM 5.66 Budurovignathusmostleri RNM 5.31 6

4 Budurovignathus mungoensis RNM 2.80 Anolcites ? neumayri RNM 1.50 2 RNM 1.10 Gladigondolella malayensis malayensis 0 Pseudofurnishius murcianus praecursor 10.90.8 270 0 18090 270 09- -30-60 0 3060 90 54-09- 0 9045 Ammonoids Conodonts )E°( )°( (°N)

Fig. 3. The Rio Nigra stratigraphic section. From left to right: A) lithostratigraphic log, where on the left are the samples for magnetostratigraphy (red lines) and for conodonts (blue lines), while on the right are the positions of the ash-beds (black triangles), including the one at ∼28 m dated with U-Pb at 237.77 ± 0.05 Ma (Mietto et al., 2012); B) biostratigraphy, represented mainly by conodonts and ammonoids attributed to the neumayri and regoledanus subzones interval; C) IRM0.3T/ SIRM ratio, showing a general increase of high-coercivity minerals in the upper-part, suggesting a decrease of magnetite relative to hematite; D) magnetostratigraphy (ChRM declination, ChRM inclination, Virtual Geomagnetic Pole latitude, magnetozones), revealing dominant normal polarity along the entire section (magneto- zones RN1n, RN2n), punctuated by a reverse magnetozone (RN1r) and three single-sample reverse intervals (RN1n.1r, RN1n.2r, RN1r.1n).

volcaniclastic sandstones and marls. The basalt-sediment contact is 3. Paleomagnetism characterized by pockets sometimes bearing ammonoids. Upsection, marls and shales become dominant, intercalated with limestones and 3.1. Methods volcaniclastic calcarenites. The upper part is enriched in bioclastic calcarenites that are in sharp upper contact with the slope breccias of A total of 52 and 28 standard (10 cc) drill core samples have been the Sciliar-III carbonate platform. A tuff layer at ~27.5 m yielded ahigh recovered from the Rio Nigra and Rio Frommer sections respectively precision U-Pb detrital zircon date of 237.77 ± 0.05 Ma (Mietto et al., and analyzed at the Alpine Laboratory of Paleomagnetism of Peveragno 2012)(Fig. 3A). The Rio Nigra section is characterized by the presence (Italy). Samples were thermally demagnetized in steps of 50 °C–25 °C of conodonts Gladigondolella malayensis malayensis, G. tethydis, Budur- from room temperature up to 675 °C with an ASC Scientific TD48 oven. ovignathus mostleri, B. mungoensis, B. diebeli, Paragondolella inclinata, P. The natural remanent magnetization (NRM) was measured after each foliata, Pseudofurnishius murcianus praecursor and P. murcianus murcianus step with a 2G Enterprises 755 DC-SQUID cryogenic magnetometer (Figs. 3B; 4). This association suggests a late Ladinian age, confirmed by located in a magnetically shielded room. The directions of the NRM the occurrence of ammonoids Anolcites? neumayri, Zestoceras cf. nitidum were plotted on standard vector end-point demagnetization diagrams and Frankites regoledanus attributed altogether to the neumayri and re- (Zijderveld, 1967) and the characteristic remanent magnetization goledanus Subzones (De Zanche et al., 1993; Mietto and Manfrin, 1995; (ChRM), where present, was isolated with standard principal compo- Broglio Loriga et al., 1999; Mietto et al., 2008; Mietto et al., 2012). nent analysis of selected data. Isothermal remanent magnetization The Rio Frommer section (coordinates: 46° 32′ 16″ N; 11° 36′ 20.6″ (IRM) acquisition experiments were performed using an ASC Scientific E) crops out along the Rio Frommer Creek, ~1 km southwest of the IM-10-30 impulse magnetizer and an AGICO JR-6 spinner magnet- village of Compaccio/Compatsch in the Alpe di Siusi (Fig. 2B). The ometer on 8 samples from Rio Nigra and 7 samples from Rio Frommer. section encompasses ~40 m of strata pertaining to the Frommer Thermal demagnetization of a three-component IRM (Lowrie, 1990) member of the Fernazza Formation (Fig. 5A). It starts with basalts was performed on a subset of the samples from both sections adopting overlain by volcaniclastic shales intercalated with marls and fine 2.5 T, 0.4 T and 0.12 T orthogonal fields. The relative concentration of sandstones. The basal contact with the lavas is marked by a chaotic low vs. high coercivity minerals was obtained by computing the ratio of level. Marls and shales become more abundant upsection. A few tuff IRM imparted at 0.3 T and at a saturating 1.0 T fields (IRM0.3T/SIRM). layers are present. Ammonoids recovered in the basal portion of the Rio Finally, the low-field magnetic susceptibility (κ) and the anisotropy of Frommer section (Anolcites? neumayri, Zestoceras cf. nitidum, Pro- the magnetic susceptibility (AMS) were measured with an AGICO KLY-3 trachyceras ladinum, Frankites sp., and Frankites regoledanus; Fig. 5B) are Kappabridge. attributed to the neumayri and regoledanus Subzones of late Ladinian age, similar to Rio Nigra.

54 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Fig. 4. Conodonts of the Rio Nigra section (scale bar = 200 μm). A is for upper view, B for lower view, and C for lateral view. 1) Budurovignathus mostleri (CNI6); 2) Budurovignathus mungoensis (CNI6); 3) Budurovignathus diebeli (CNI1); 4) Pseudofurnishius murcianus praecursor (CNI6); 5) Pseudofurnishius murcianus murcianus (CNI1); 6) Paragondolella foliata (CNI3); 7) Gladigondolella tethydis (CNI1); 8) Gladigondolella malayensis malayensis (CNI4); 9) Paragondolella inclinata (CNI5).

3.2. Magnetic properties are close to 1 in the upper part of the Frommer member in both sections (Figs. 3C, 5C), suggesting the presence of a dominant low-coercivity Values of κ and NRM are relatively high in the lower part of both magnetic phase. Above level ~25 m at Rio Nigra (Fig. 3C) and level sections just above the lavas (Figs. 3A, 5A), due to high concentrations ~33 m at Rio Frommer (Fig. 5C), IRM0.3T/SIRM values slightly decrease of volcanigenic material. Upsection, κ and NRM values tend to decrease to around 0.85, indicating a moderate increase in high-coercivity mi- suggesting a decrease of volcaniclastic input; the IRM0.3T/SIRM values nerals.

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Rio Frommer section

A. B. C. D. Magnetostratigraphy Lithostratigraphy Biostratigraphy IRM0.3/SIRM Thickness Declination Inclination VGP Latitude (m)

RFM 38.07 RFM 37.60 38 36

34 RF1n.4r RFM 31.61 RFM 30.39 32

RFM 28.10 30 RFM 27.84 RFM 26.44 28

RFM 24.27 26 RFM 23.49 24

RFM 21.83 22 Frankites sp. RFM 21.01 RFM 20.54 RF1n 20 RFM 18.77 18 RFM 17.00 RFM 15.80 16 RF1n.3r RFM 14.70 14

12 RFM 10.72 RFM 10.20 10 Protrachyceras ladinum 8 Frankites regoledanus Anolcites ? neumayri RFM 6.20 RFM 5.50 6 RFM 4.78 RFM 4.05 RF1n.2r RFM 3.45 4

RFM 2.20 Zestoceras nitidum RFM 2.00 2 RF1n.1r RFM 1.32 RFM 0.30 RFM 0.00 0 0.8 0.9 1 270 270180900 -90 -30-60 0 3060 90 -90 -45 0 45 90 (°E) (°) (°N)

Fig. 5. The Rio Frommer stratigraphic section. From left to right: A) lithostratigraphy, where samples for magnetostratigraphy are on the left of the stratigraphic log, and ash-beds are indicated on the right (black triangles); B) biostratigraphy, represented exclusively by ammonoids attributed to the neumayri and regoledanus subzones interval; C) IRM0.3T/SIRM ratio, showing a general increase of high-coercivity minerals in the upper part, suggesting a decrease of magnetite relative to hematite; D) magnetostratigraphy (ChRM declination, ChRM inclination, VGP [Virtual Geomagnetic Pole] latitude, magnetozones), showing only one normal magnetozone (RF1n), with four single-sample aberrant direction (reverse polarity intervals?) labeled RF1n.1r, RF1n.2r, RF1n.3r, and RF1n.4r.

The IRM acquisition curves of samples from both sections (Fig. 6, 3.3. Magnetostratigraphy samples labeled with prefix ‘RNM’ for Rio Nigra and ‘RFM’ for Rio Frommer followed by a suffix indicating stratigraphic position) tend to Bipolar ChRM component directions, oriented predominantly north- saturate around 0.1–0.2 T indicating the presence of a low coercivity and-down or more rarely south-and-up in in situ coordinates, have been mineral. Samples RFM37.60 and RNM21.16 tend to saturate around isolated from ~150 °C to ~550 °C in 47 of 52 samples from Rio Nigra 1.7–2 T indicating the presence of a higher coercivity mineral phase. and in all (28) samples from Rio Frommer (Fig. 8) (see also Supple- The three-axes IRM experiments (Fig. 7) show that the magnetization is mental Table S1). The ChRM directions do not coincide with the geo- generally carried by the 0.12 T curve that shows maximum unblocking centric axial dipole (GAD) field in in situ coordinates (Fig. 9), indicating temperatures of ~575 °C, indicating the dominant presence of magne- that any overprints of recent origin have been successfully removed. tite in agreement with most of the IRM acquisition curves. In a few The mean ChRM direction in tilt-corrected coordinates, calculated by cases (e.g., sample RNM28.69), the 2.5 T curve seems to persists above applying Fisher statistics (Fisher, 1953) on n = 75 ChRM directions 575 °C, possibly indicating minor contributions from (fine-grained?) from both sections, yields a paleomagnetic pole (Table 1) that lies close hematite, in agreement with the subsidiary high coercivity component to the paleopole from the Ladinian Buchenstein beds of the Dolomites observed in the IRM acquisition curves. (Muttoni et al., 2004a, 2013), supporting a primary origin of the ChRM. The AMS data indicate that samples from both sections are char- A virtual geomagnetic pole (VGP) was calculated for each ChRM acterized by relatively scattered principal susceptibility axes and very component direction in tilt corrected coordinates. Assuming that the low degrees of anisotropy (P < 1.1) (Fig. S1, Supplemental material). Dolomites were located in the northern hemisphere (Muttoni et al., Most of the Rio Frommer samples show oblate anisotropy ellipsoids, 2004a), the latitude of the sample VGP relative to the north paleo- whereas Rio Nigra ellipsoids are either oblate or prolate (Fig. S1, magnetic pole (positive for normal, negative for reverse polarity) was Supplemental material), but in any case, even in the prolate cases, the used for interpreting the polarity stratigraphy. Each magnetozone is degree of anisotropy is very low. These observations tend to exclude prefixed by the acronym for the source of the magnetostratigraphy major tectonic overprints (e.g., pervasive compression-induced folia- (“RN” for Rio Nigra, “RF” for Rio Frommer). The latitudes of the sample tion) on the studied samples. VGPs define a sequence of 3 magnetozones at Rio Nigra (from RN1nto RN2n; Fig. 3D) and one magnetozone at Rio Frommer (RF1n), in which

56 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

(A) RIO NIGRA 4. An updated Triassic Geomagnetic Polarity Time Scale 1.0 0.8 The U-Pb-calibrated magnetostratigraphy of the Rio Nigra and Rio 0.6 Frommer sections represents a valuable contribution to the evolving 0.4 Triassic GPTS, which we reappraise after Hounslow and Muttoni (2010) 0.2 using an updated inventory of Early–Middle Triassic age-calibrated 0.0 Tethyan marine magnetostratigraphies from the literature that can be -0.2 appended to the Late Triassic Newark continental APTS (Fig. 1A, B). -0.4 We initially constructed a visually coherent correlation grid where IRM (normalized) -0.6 individual sections are scaled in the depth domain using magnetozone thickness usually expressed relative to the thickest and most continuous -0.8 (reference) sections for each stratigraphic interval of the Triassic. In this -1.0

0 correlation scheme, subdivided into three separate figures for better .2 0.2 0.4 0.6 0.8 1.6 1.0 1.2 1.4 1.8 2.0 2 2.4 visualization (Figs. 11–13), magnetostratigraphic correlation lines Applied Field (mT) should ideally be horizontal, albeit this geometry is not always attain- RNM1.10 RNM2.80 RNM5.66 RNM11.85 RNM21.16 able due to variations in sediment accumulation rates within some of RNM22.50 RNM28.69 RNM31.21 the sections used in the compilation. Within this correlation grid, we (B) RIO FROMMER correlated the magnetostratigraphy of individual sections onto the re- 1.0 ference sections (Meishan [Li and Wang, 1989] and Guandao 0.8 [Lehrmann et al., 2006; Li et al., 2018] for the Early–Middle Triassic, 0.6 Seceda [Muttoni et al., 2004a] and Mayerling [Gallet et al., 1994, 0.4 1998] for the Middle–Late Triassic, the Newark APTS [Kent et al., 2017, 0.2 2018] for the Late Triassic) using additional data from correlative an- 0.0 cillary sections, essentially key fossil datums useful to define (or im- -0.2 prove the definition of) stage boundaries and extend the applicability of -0.4 U-Pb age data. In general, we opted to maintain the magnetostrati- IRM (normalized) -0.6 graphy of the reference sections as integral as possible to allow the -0.8 traceability of the original data used to compile the final magnetic -1.0 polarity timescale; however, focused insertions of missing or better 0 .2 defined magnetozones from ancillary sections have been performed 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2 2.4 Applied Field (mT) where appropriate (and denoted by the different section acronyms). RFM0.30 RFM2.20 RFM3.45 RFM10.72 RFM15.80 The augmented reference sections in depth coordinates were then RFM21.01 RFM37.60 migrated to the time domain by linear stretching between U-Pb dated tie-points (see Table 2 for a summary of U-Pb dates) and, where pos- Fig. 6. Normalized IRM backfield curves of a set of selected samples from Rio sible, using astrochronology (Figs. 11–13, right column). Contrary to Nigra (Panel A) and Rio Frommer (Panel B). Samples labeled with prefix ‘RNM’ Hounslow and Muttoni (2010), Ogg (2012a) and Hounslow et al. for Rio Nigra and ‘RFM’ for Rio Frommer followed by a suffix indicating stra- (2018), we opted to maintain in the assembled magnetic polarity tigraphic position. Most of the samples show saturation around 100-200 mT timescale the original magnetozone nomenclature of the constituent consistent with magnetite, except for RNM21.16 and RFM37.60 that tend to reference sections (e.g., SC for Seceda, etc.). This philosophy based on saturate at much higher fields because of the presence of high coercivity mi- magnetostratigraphic correlations of reference sections under the as- nerals (probably hematite). sumption that sedimentation is a linear proxy of time differs from timescales erected assuming biozones of equal duration (Krystyn et al., single-sample reverse sub-magnetozones (RF1n.1r, RF1n.2r, RF1n.3r, 2002; Gallet et al., 2003; see also discussion in Muttoni et al., 2010 and RF1n.4r) are embedded (Fig. 5D). Kent et al., 2017). Parenthetically, biostratigraphy enters our con- The two sections have been tentatively correlated using magnetos- struction essentially to define stage boundaries but very moderately asa tratigraphy and rock-magnetic properties (Fig. 10). Reverse magneto- correlation tool. Also, we avoided segmenting sections by introducing zone RN1r has been correlated to RF1n.4r and reverse sub-magneto- gaps according to the apparent lack of recovery of a given biozone zone RN1n.1r to RF1n.3r (Fig. 10). This correlation matches the trend (Krystyn et al., 2002; Hounslow and Muttoni, 2010, Fig. 10) because it of the IRM0.3T/SIRM curves observed in both sections and interpreted as is hard to assess the duration of these postulated gaps. a slight increase of high-coercivity minerals in the upper part of the The correlation grid is subdivided into three time intervals Frommer member (Fig. 10). The IRM0.3T/SIRM spikes probably mark a (Induan–Anisian, Anisian–Carnian, Carnian–Rhaetian) for clarity of (relative) major input of high-coercivity minerals as hematite possibly visualization, as described below. due to the extrusion and consequent low temperature oxidation of subaerial volcanics (e.g. Holmes, 1995; Planke et al., 1999). Ammonoid 4.1. Induan–Olenekian–Anisian (Early Triassic–early Middle Triassic) levels are too sparse to be used as meaningful correlation tools or to erect subzone boundaries; for example, the levels in the two sections The magnetostratigraphy across the Permian/Triassic with F. regoledanus are not necessarily correlative. The magnetic cor- (Changhsingian/Induan) boundary is relatively well established (and relation implies complex onlap geometries of sedimentary layers with dominated by normal polarity) at Meishan in China (Li and Wang, the underlying basalts, in agreement with the general tectonostrati- 1989), which is the GSSP for the base of the Triassic placed at the first graphic setting of the area characterized by morphologically complex occurrence (FO) of conodont Hindeodus parvus. At Meishan, the age of volcanic structures onlapped and sutured by volcaniclastic packages of the boundary has been recently recalibrated at 251.90 ± 0.02 Ma by extremely variable thicknesses (Fig. 2C). Accordingly, the Rio Nigra and interpolating U-Pb ages at 251.94 ± 0.04 Ma and 251.88 ± 0.03 Ma Rio Frommer sections probably represent the same Neumayri–R- obtained respectively from a level 16 cm below and 12 cm above the egoledanus stratigraphic interval straddling the U-Pb detrital zircon age level registering the FO of H. parvus (Burgess et al., 2014)(Fig. 11). This of 237.77 ± 0.05 Ma (Fig. 10). new recalibration updates the previous ages proposed by Mundil et al. (2004) and Shen et al. (2011). Correlative sections with a reliable

57 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

(A) RIO NIGRA (B) RIO FROMMER X (0.12 T) Y (0.4 T) Z (2.5 T) RNM 2.80 RFM 2.20 6.0 8.0 5.0 4.0 6.0 3.0 4.0 J(A/m) 2.0 (A/m) J 2.0 1.0 0 0 0 0 0 50 50 100 150 200 250 300 350 400 450 500 550 600 650 100 150 200 250 300 350 40 450 500 550 600 650 T (°C) T (°C) RNM 11.47 RFM 20.54 1.4 6.0 1.2 5.0 1.0 4.0 0.8 3.0 J (A/m)

J (A/m) 0.6 2.0 0.4 0.2 1.0 0 0 0 0 50 50 50 100 150 200 250 300 350 400 450 500 550 600 650 100 150 200 250 300 350 400 450 500 550 600 6 T (°C) T (°C) RNM 28.69 RFM 31.61 0.16 0.012 0.16

0.12 0.008 0.12 0.004 0.08 0.08 J (A/m)

J (A/m) 0

0.04 500 525 550 575 600 625 650 675 0.04

0 0 0 0 50 50 100 150 200 250 300 350 400 450 500 550 600 650 100 150 200 250 300 350 400 450 500 550 600 650 T (°C) T (°C)

Fig. 7. Thermal demagnetization of a three-component IRM imparted first at 2.5 T than in 0.4 T and 0.12 T fields along orthogonal axes on selected samplesfromRio Nigra and Rio Frommer. The largest part of the magnetization is acquired along the 0.12 T axis and is characterized by maximum unblocking temperatures com- patible with magnetite. In a few samples (e.g., RNM 28.69), a subsidiary part of the magnetization is acquired along the 2.5 T axis and persists above 575°C, suggesting the presence of hematite. magnetostratigraphy are Bulla/Siusi in Italy (Scholger et al., 2000), Chaohu section is characterized by a short normal polarity zone en- Abadeh in Iran (Gallet et al., 2000a), Hechuan in China (Steiner et al., cased in a dominant reverse polarity interval (Sun et al., 2009). Li et al. 1989) and Shangsi in China (e.g. Steiner et al., 1989; Glen et al., 2009) (2016) reinterpreted this polarity sequence and inserted a zone of un- (Fig. 11). At the Guandao section from China (Payne et al., 2004; certain polarity (without providing supportive information or experi- Lehrmann et al., 2006), the Permian/Triassic boundary interval is mental data) at the base of the section that they correlated to normal characterized by a large unsampled shale interval, whereas the lower magnetozone ME3n at Meishan in order to use the age of 251.9 Ma as a Chaohu section from China (Sun et al., 2007, 2009; Li et al., 2016; tie-point for the cyclostratigraphy. In addition, at lower Chaohu the reported as Pingdingshan West in Hounslow and Muttoni, 2010) does Permian/Triassic boundary is not clearly defined by biostratigraphy (it not contain a biostratigraphic record of the boundary (e.g. Zhao et al., has been placed using the ‘boundary stratigraphic set’ of Peng et al. 2008; Sun et al., 2009)(Fig. 11). (2001) encompassing the boundary clay bed [Zhao et al., 2007, 2008; The Induan/Olenekian boundary is placed in the lower Chaohu Sun et al., 2009]). An alternative option for the age of the Induan/ section at the FO of conodont Neospathodus waageni, which falls in a Olenekian boundary is provided by Galfetti et al. (2007) who obtained short normal polarity magnetozone within a dominant reverse polarity a U-Pb zircon date of 251.22 ± 0.20 Ma for a volcanic ash layer within interval (Sun et al., 2007, 2009; Li et al., 2016). A correlative magneto- the “Kashmirites densistriatus beds” of early Olenekian age (lower Eu- biostratigraphic pattern is observed also in the lower part of the flemingites romunderi ammonoid Zone, considered mostly coeval to the Guandao section, from magnetozone GDL1 to GDL5 (Lehrmann et al., FO of N. waageni in Canada [Orchard and Tozer, 1997; Orchard, 2008; 2006)(Fig. 11). Following the cyclostratigraphy of the lower Chaohu Romano et al., 2013]) from the Luolou Formation of South China; this section (Li et al., 2016), based on 405 kyr and 100 kyr eccentricity age estimate coupled with the recalibrated age of the Permian/Triassic cycles, and accepting an age for the Permian/Triassic boundary of boundary would imply a duration of the Induan of only ~0.7 Myr. 251.9 Ma (Burgess et al., 2014), the Induan/Olenekian boundary should Acknowledging the limitations illustrated above, we provisionally fall at 249.9 Ma for a total duration of the Induan of ~2 Myr (Li et al., opt for the Li et al. (2016) solution (Induan/Olenekian boundary at 2016). 249.9 Ma) as we consider the uncertainties related to the trans-con- However, there are some issues regarding the astronomically tuned tinental biostratigraphic correlations at the base of the Galfetti et al. lower Chaohu section. In Li et al. (2016), the cyclostratigraphy is ca- (2007) solution possibly larger than the uncertainties related to the librated with the U-Pb zircon interpolated date of 251.90 ± 0.02 Ma at Meishan-lower Guandao correlation at the base of the Li et al. (2016) Meishan (Burgess et al., 2014) through a questionable correlation. solution. Moreover, the U-Pb dates of Burgess et al. (2014) and According to the original magnetostratigraphy, the base of the lower Lehrmann et al. (2015) have been obtained through the EARTHTIME

58 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

(A) RIO NIGRA

-3 Sample: rnm1.10 W,Up Sample: rnm16.61 W,Up Units: A/m ×10 In Situ 15 In Situ N N 15

S N 10

S N 15 Units: A/m ×10-2 vertical horizontal E,Down E,Down

Sample: rnm22.03 W,Up Sample: rnm26.98 In Situ 20 In Situ Units: A/m ×10-3 Units: A/m ×10-3 W,Up 10

N

S N 15 N

E,Down

S N 15

E,Down (B) RIO FROMMER Sample: rfm1.32 Sample: rfm4.05 W,Up In Situ W,Up In Situ 12 Units: A/m ×10-3

S N 10

N N S N 4 10 E,Down E,Down Units: A/m ×10-2

W,Up Sample: rfm14.70 W,Up Sample: rfm18.77 20 In Situ 8 In Situ Units: A/m ×10-3 Units: A/m ×10-4

N S N N 12 S N 20

E,Down

E,Down

Fig. 8. Vector end-point NRM demagnetization diagrams and stereographic projections of representative samples from Rio Nigra (Panel A) and Rio Frommer (Panel B). tracer solution, thus we prefer to avoid the comparison with the dates the correlation between lower Chaohu and Meishan without the in- obtained with older tracers, as is the case with the Olenekian U-Pb troduction of purported magnetozones in the lower Chaohu section. zircon date of Galfetti et al. (2007). Even if we prefer the Li et al. (2016) Using also the magnetostratigraphy of Shangsi (e.g. Steiner et al., 1989; option for the Induan/Olenekian boundary age, we would still update Glen et al., 2009) to test the correlation between Meishan and lower

59 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

RIO NIGRA

IN SITU Mean Direction TILT CORRECTED GAD Direction

RIO FROMMER

IN SITU Mean Direction TILT CORRECTED GAD Direction

ALPE DI SIUSI

IN SITU Mean Direction TILT CORRECTED GAD Direction

Fig. 9. Stereographic projections in in situ and tilt-corrected coordinates of the sample ChRM component directions from Rio Nigra (upper panel), Rio Frommer

(middle panel), and from both sections together as Alpe di Siusi (lower panel). Fisher site-mean directions (red square) and a95 confidence circles are reported in each projection. The position of the present-day Geocentric Axial Dipole (GAD) field is also reported.

Chaohu, we propose magnetozone ME3r (Meishan) as correlative to constrained by data from Guandao (Lehrmann et al., 2006) and upper Ch1r (lower Chaohu) (Fig. 11). Using the cyclostratigraphy of Meishan Chaohu (Li et al., 2016)(Fig. 11). The Olenekian/Anisian boundary is and Chaohu (Li et al., 2016), calibrated with the U-Pb zircon dates from placed at the FO of conodont Chiosella timorensis in reverse magneto- Meishan (Burgess et al., 2014), we estimate the age of the Induan/ zone GD2r at Guandao (Lehrmann et al., 2006)(Fig. 11). This datum Olenekian boundary at ~249.7 Ma (~0.2 Myr younger than in Li et al., was found also in correlative magneto-biostratigraphic sections at Deşli 2016), and a consequent duration of the Induan of ~2.2 Myr (Fig. 11). Caira in Romania (Gradinaru et al., 2007), Kçira in Albania (Muttoni The magnetostratigraphy of the Olenekian is relatively well et al., 1996a), and Chios in Greece (Muttoni et al., 1995)(Fig. 11). The

60 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Table 1 cycles recognized in the Germanic Basin sequence (Szurlies, 2007) as Paleomagnetic directions, poles and paleolatitudes of Rio Nigra and Rio well as at the lower Chaohu and Meishan sections (Li et al., 2016), Li Frommer sections. et al. (2018) estimated an age of 246.8 Ma for the base of the Anisian. Mean directions This modest discrepancy between radiometric and astrochronologic estimates, on the order of ~0.5 Myr, could be due to a missing 405 kyr Site Comp. N In situ Tilt-corrected beat or radiometric dating errors (Li et al., 2016). Here, we adopt the age of 247.3 Ma for the Anisian base (Lehrmann et al., 2015), which K α95 Dec. Inc. k α95 Dec. Inc. leads to a ~2.4 Myr-long Olenekian and a ~4.6 Myr-long Early Triassic Rio Nigra ChRM 47 10.8 6.6° 4.5°E 27.1° 10.8 6.6° 356.1°E 50.0° (Induan and Olenekian). Rio Frommer ChRM 28 5.2 13.2° 350.8°E 28.2° 5.2 13.2° 351.8°E 39.1° In summary, we adopted as reference sections to construct our Early Alpe di Siusi ChRM 75 7.6 6.4° 359.8°E 27.6° 7.6 6.4° 354.5°E 46.2° Triassic GPTS the Meishan magnetostratigraphic section (Li and Wang, Geocentric axial dipole 2.6°E 62.7° 1989), provided with a U-Pb zircon age estimate of 251.90 ± 0.02 Ma (Burgess et al., 2014) for the Permian/Triassic (Changhsingian/Induan) Paleomagnetic poles and paleolatitudes boundary as defined by the FO of H. parvus (Yin et al., 2001), the lower Chaohu section (Sun et al., 2009), and the entire Guandao magnetos- Site Lat. Long. dp dm Paleolatitude tratigraphic section (from magnetozone GDL1 to GDL6 [Lehrmann

Rio Nigra 74.0°N 203.8°Ε 5.9° 8.8° 30.8°N ± 5° et al., 2006] and from GD1 to GD10 [Li et al., 2018]). The Induan/ Rio Frommer 64.7°N 209.6°Ε 9.4° 15.8° 22.1°N ± 7° Olenekian boundary, placed in the lower Chaohu section at the FO of N. Alpe di Siusi 70.5°N 206.4°Ε 5.3° 8.2° 27.5°N ± 4° waageni and cyclostratigraphically constrained to lie around 249.7 Ma, has been traced onto the Guandao reference section using magnetos- Note: Comp.: paleomagnetic component; N: number of samples; k, α95: Fisher statistics parameters; Dec.: mean declination; Inc.: mean inclination; Lat.: lati- tratigraphy (Fig. 11). The Guandao section is provided also with direct tude; Long.: longitude; dp, dm: confidence limits on poles. evidence for the Olenekian/Anisian boundary (FO of Ch. timorensis) attached to an interpolated U-Pb age of ~247.3 Ma (Lehrmann et al., middle part of the Guandao section, within GD2r, is provided also with 2006, 2015), in substantial agreement with astrochronology (Li et al., U-Pb zircon dates, from which an interpolated age of 2018). Finally, we also adopted in our GPTS two short normal polarity 247.28 ± 0.12 Ma for the Anisian base has been proposed (Lehrmann magnetozones from Kçira (Kç1r.1n and Kç1r.2n) around the Olenekia- et al., 2015)(Fig. 11). Using 405 kyr and 100 kyr eccentricity cycles n–Anisian boundary (Muttoni et al., 1996a) that seem absent or poorly recognized in this mid-upper part of the Guandao section (the lower defined at Guandao (Fig. 11). part of the section did not yield cyclostratigraphy), integrated with Rio Nigra

Thickness IRM 0.3 T/SIRM (m) Frankitesregoledanus

RN2n 30 Rio Frommer

Zestoceras nitidum cf. IRM 0.3 T/SIRM Thickness (m)

RN1r.1n RF1n.4r RN1r 30

20 RF1n Frankites sp.

237.77±0.05 Ma 20

RN1n.2r RF1n.3r

RN1n.1r 10 Frankites regoledanus Anolcites? neumayri

RF1n.2r Zestocerasnitidum RF1n.1r 0 10 0.8 0.9 1 RN1n Anolcites?neumayri

0 10.90.8

Fig. 10. Correlation between Rio Nigra and Rio Frommer based on magnetostratigraphy and the IRM 0.3 T/SIRM ratio. Ammonoid biostratigraphy confirms that the two sections are broadly coeval. The 237.77 ± 0.05 Ma U-Pb detrital zircon age of Mietto et al. (2012) is also indicated.

61 .Mrne al. et Maron M. Age (Ma) GD10n 25 SC3 FO U-Pb ages: GD9r SC3n 241 20 Eoprotrachyceras GD9n curionii LADINIAN E27 ALB 15 SC2r HC4r (1) Burgess et al., 2014 GD8r ALB SC2 (2) Lehrmann et al., 2015 SC2n GD8n sec. sbz. 10 241.71 ± 0.07 Ma (4) 241.71 ± 0.07 Ma (3) Lehrmann et al., 2006 GD7r E26 15 HC3n 5 SC1r GD7 GD7n 242.01 ± 0.04 Ma 242 (4) Wotzlaw et al., 2018 242.01 ± 0.04 Ma (4) SC1 GD6r E25 0 HC3r

GD6n reitzi sbz. curionii sbz. S6r 140 GD6 Abbreviations: E24 HC2n Lower Seceda Conodont genera: GD5r E23 S6n 10 (Italy) HC2r Ns.: Neospathodus GD5 243 120 Ng.: Neogondolella Budurovignathus truempyi E22 S5r HC1n GD5n S5n HC1r H.: Hindeodus E21 I.: Isarcicella GD4r E20 100 5 Ammonoid Zones: S4r 244

sec.: secedensis TRIASSIC MIDDLE GD4 Breccia Correlation line 80 Kçira ANISIAN GPTS Correlation S4n 0 GD4n (Albania) S3r 245 line 50 E19 60 Holy Cross Mt. E18 40 Kç3r Deşli Caira GD3r (Poland) (Romania) Chios A S3n E17 (Greece) 40 GD3 246 0 m Kç3n E16 35 Upper Chaohu 30 30 DC2n 12 S3n.1r (China) GD3n E15 Kç2r 246.50 ± 0.11 Ma Chiosellatimorensis 25 Ch2n 246.50 ± 0.11 Ma (2) Kç2n 10 20 E14 20 S2r FO 405 kyr 247.08 ± 0.11 Ma (2) OAB fault S2n 62 OAB OAB OAB Chiosella 247 cycles 247.32 ± 0.08 Ma (3) 15 247.08 ± 0.11 Ma 247.46 ± 0.05 Ma (2) 8 S1r GD2r timorensis E13 10 DC1r 20 Kç1r Ch1r 247.32 ± 0.08 Ma E15 GD2r Kç1r 5 6 0 m 247.46 ± 0.05 Ma E14 405 kyr 0 m DC1n 50 E13 ? S1n

E12 cycles 4 E12 248 0 m GD2n Kç1n 2 Ch1n Chiosella timorensis 10 Chiosella timorensis GD2n

E11 Chiosella timorensis E10 0 m Upper Silesia E9 GD1r (Poland) 405 kyr GD1n

GD1 Palaeogeography, Palaeoclimatology,Palaeoecology517(2019)52–73 cycles GDL6r He4r Kç1n.1r 249 GDL6n He4n 0 m OLENEKIAN GDL6 FO

E5 GDL5r waageniNs. Neospathodus GDL5n IOB 100 Abadeh GDL5 waageni IOB He3r (Iran) Meishan Ch2r Ns. dieneri He3n 0 m (China) 250 GDL4r Bulla/Siusi E4 Shangsi (Italy) Ch2

is Ns. waageni Ch2r.1n He2r (China) TRIASSIC EARLY

eneri

i E3 ens BS3r Ab4r us/typicalis

. d .

i

v

s

e

H.parvus GDL4n N 251

vus

Ng.tulongensis Ch2n He2n Ng.discreta BS3n na sp. 40 Ab4n 405 kyr sch

cica Ch1r

e

r INDUAN

.par cycles Me3r H. par Me3r

25m

Ng.meishan He1r H

Claraia

.sta BS2r .isa Elliso Ab3r

I GDL3r I FO

E2 H. parvus 10 30

H.typicalis Hindeodus

Sh5 Ophiceras sp. Ch1r H. parvus He1n CIB (+ 0.12 m) E1 GDL3n CIB Me3n BS2n Ab3n 251.88 ± 0.03 Ma Me3n parvus

H.praeparvus Sh4 CIB H. typicalis 251.88 ± 0.03 Ma (1) CIB CIB 251.94 ± 0.04 Ma 252 E1 GDL2r Sh3 20 CIB Sh2 E0 BS1n Ab2r Ch1r.1n 0 m 251.94 ± 0.04 Ma (1) vus Ng. changxingensis

Sh1r eschei E0 Me2r (- 0.16 m) ar Ab2n

I.turgida GDL2n Hechuan 10 E . p Ab1r Me2

I.sta GDL1r H

(China) Me2n 25 m Ab1n 5 m

I.staeschei Lower Chaohu Ophiceras sp. Me1r E-1 (China) Guandao 0 m Me1r 253 (China) CHANGHSINGIAN LATE PERMIAN LATE

(caption on next page) M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Fig. 11. Magnetostratigraphic correlations of selected Early Triassic sections: lower Chaohu (Sun et al., 2007, 2009) and upper Chaohu, China (Li et al., 2016); Guandao, China (Lehrmann et al., 2006); Hechuan, China (Steiner et al., 1989); Shangsi, China (Steiner et al., 1989; Glen et al., 2009); Meishan, China (Li and Wang, 1989); Bulla/Siusi, Italy (Scholger et al., 2000); Abadeh, Iran (Gallet et al., 2000a); Deşli Caira, Romania (Gradinaru et al., 2007); Kçira, Albania (Muttoni et al., 1996a); Chios, Greece (Muttoni et al., 1995); Upper Silesia and Holy Cross Mountain, Poland (Nawrocki and Szulc, 2000); Seceda (lower part), Italy (Muttoni et al., 2004a). Long-eccentricity cycles (405 kyr) from Chaohu, Meishan and Guandao are from Li et al. (2016, 2018). The radiometric ages around the base of the Induan (251.9 Ma) are from Burgess et al. (2014). The age of the Olenekian base (~249.7 Ma) is estimated through Meishan and lower Chaohu cyclostratigraphy (Li et al., 2016). The radiometric ages around the base of the Anisian (247.3 Ma) are from Lehrmann et al. (2006, 2015), while the base of the Ladinian (241.5 Ma; base of Eoprotrachyceras curionii Subzone) has been dated following the radiometric-based age model of Wotzlaw et al. (2018). FO of conodont Hindeodus parvus is from Meishan, South China (Induan base; Li and Wang, 1989), FO of conodonts Neospathodus waageni (Olenekian base) and Chiosella timorensis (Anisian base) are from Guandao, South China (Lehrmann et al., 2006), base of Eoprotrachyceras curionii ammonoid Subzone is from Seceda, Italy (Ladinian base; Muttoni et al., 2004a; Wotzlaw et al., 2018). Acronyms used for stage boundaries are: CIB for Changhsingian/Induan boundary; IOB for Induan/Olenekian boundary; OAB for Olenekian/ Anisian boundary; ALB for Anisian/Ladinian boundary.

4.2. Middle Triassic (Anisian–Ladinian) from Punta Grohmann are coherent with the U-Pb date from Rio Nigra (Mietto et al., 2012), as confirmed by lithostratigraphic correlations At the Guandao reference section, the Anisian base (247.3 Ma, FO of between Alpe di Siusi and Punta Grohmann (Storck et al., 2018). These C. timorensis; see above) is characterized by an interval of dominant new radiometric ages constrain Middle Triassic magmatism in the Do- normal polarity followed by an interval of mainly reverse polarity lomites to a ~5 Myr long interval, including a ~0.9 Myr episode of (Fig. 12). The Anisian/Ladinian boundary is placed at the FO of am- basaltic volcanism during the Ladinian (Storck et al., 2018). monoid Eoprotrachyceras curionii at the Bagolino GSSP in Italy (Brack The magnetostratigraphy of the Ladinian is well represented at et al., 2005) from a level that was litho-biostratigraphically correlated Seceda in Italy (Muttoni et al., 2004a), Mayerling in Austria (Gallet to reverse polarity magnetozone SC2r at Seceda in Italy (Muttoni et al., et al., 1994, 1998) and Prati di Stuores in Italy (Broglio Loriga et al., 2004a) where it was recently attributed an interpolated U-Pb age of 1999; Mietto et al., 2012), which are chosen as reference sections for 241.46 ± 0.28 Ma (Wotzlaw et al., 2018)(Fig. 12). At additional our composite GPTS (Fig. 12). The Ladinian/Carnian (Middle/Late magneto-biostratigraphic sections, namely Pedraces in Italy (Brack and Triassic) boundary is placed at the Prati di Stuores GSSP at the FO of Muttoni, 2000), Frötschbach in Italy (Muttoni et al., 1996b, 1997), ammonoid Daxatina canadensis and is approximated by the FO of con- Belvedere in Italy (Brack and Muttoni, 2000), Aghia Triada in Greece odont Paragondolella polygnathiformis (Mietto et al., 2012). The (Muttoni et al., 1998), and Gammstein-1 in Austria (Gallet et al., 1998), boundary falls toward the base of normal polarity magnetozone S2n the Anisian/Ladinian boundary is proxied by the FO of conodont Neo- (Broglio Loriga et al., 1999; Mietto et al., 2012)(Fig. 12). The Prati di gondolella praehungarica (Fig. 12). At Guandao, the Anisian/Ladinian Stuores magnetostratigraphy (Broglio Loriga et al., 1999) was originally boundary as approximated by the FO of Budurovignathus truempyi was correlated to the Mayerling magnetostratigraphy (Gallet et al., 1998) attributed an astrochronological age of 241.5 Ma by counting long and across magnetozones MA3n–MA5n (Broglio Loriga et al., 1999; short eccentricity cycles from the Meishan GSSP at 251.9 Ma (Li et al., Hounslow and Muttoni, 2010). After the finding of P. polygnathiformis at 2018; see also discussion above), in excellent agreement with Wotzlaw Prati di Stuores (Mietto et al., 2012), Kent et al. (2017) proposed a et al. (2018). Adopting the age of 241.46 Ma for the Ladinian base correlation of Prati di Stuores to MA5n–MA5r at Mayerling that opti- (Wotzlaw et al., 2018), the Anisian Stage should be ~5.8 Myr-long mizes the general distribution of P. polygnathiformis in both sections (Fig. 12). (Fig. 12). According to this revised correlation, the FO of P. poly- Additional U-Pb detrital zircon dates for the Anisian–Ladinian come gnathiformis at Mayerling should fall slightly below the FO of D. cana- from the Latemar carbonate platform of the Dolomites, Italy densis at Prati di Stuores, a situation that has been reported also in other (241.7 + 1.5/−0.7 Ma, 241.2 + 0.7/−0.6 Ma, 242.6 ± 0.7 Ma; sections such as Guling and Muth in the Spiti Valley of India (Bhargava Mundil et al., 2003). Kent et al. (2004) used these ages in conjunction et al., 2004; Krystyn et al., 2004). with magnetostratigraphic correlation of the Latemar sequence to Se- A comparison of the conodont and ammonoid biostratigraphic ceda magnetozone SC2 to infer a much faster tempo of platform car- scales from the Reifling Basin of Austria, to which Mayerling belongs, bonates deposition than originally proposed by Preto et al. (2001, and the Dolomites (Krystyn, 1983; Mietto and Manfrin, 1995; Gallet 2004), who interpreted the ~600 shallowing-upward meter-scale cycles et al., 1998; Hochuli et al., 2015), leads us to infer that the neumayr- at Latemar as a ~9–12 Myr record of precessional forcing (~50 m/Myr i–regoledanus Subzones interval recorded at Rio Nigra and Rio Frommer sediment accumulation rate) in sharp disagreement with the ~2.2 Myr (see also above) should broadly fall in the mid part of the Mayerling duration predicted from the U-Pb ages and even shorter based on the section. Thus, reverse magnetozone RN1r at Rio Nigra, closely asso- presence of only one ammonoid zone, sub-Milankovitch cyclicity, and ciated with the 237.77 ± 0.05 Ma U-Pb zircon date, can be reasonably barely more than one magnetozone in the entire Latemar sequence correlated to MA3r at Mayerling (Fig. 12). Through the U-Pb zircon (Mundil et al., 2003; Zühlke et al., 2003; Kent et al., 2004). Subsequent dates of Seceda (Wotzlaw et al., 2018) and Rio Nigra (Mietto et al., analyses of Latemar cyclostratigraphy (Meyers, 2008) favor very fast 2012), the base of the Carnian Stage can be approximated at (~500 m/Myr) accumulation rates for the Latemar limestones, con- ~236.8 Ma, in agreement with the age proposed by Mietto et al. (2012), sistent with the U-Pb dates and magnetobiostratigraphic constraints leading to a duration of ~4.6 Myr for the Ladinian and a ~10.5 Myr- and with the recent magnetostratigraphy of the corresponding basinal long Middle Triassic (Anisian and Ladinian) (Fig. 12). Buchenstein beds in Rio Sacuz (Spahn et al., 2013). In summary, we adopted as reference sections to construct our Additional age constraints for the Anisian and Ladinian Stages are Anisian–Ladinian GPTS the U-Pb-calibrated (Wotzlaw et al., 2018) Se- presented in Storck et al. (2018), providing new U-Pb zircon dates from ceda magneto-biostratigraphic sequence (Muttoni et al., 2004a) where the Bagolino section (238.64 ± 0.04 Ma, 242.65 ± 0.04 Ma), which the Anisian/Ladinian boundary is traced at the FO of E. curionii with an are in agreement with the dates from Seceda (Wotzlaw et al., 2018). interpolated U-Pb age of 241.46 ± 0.28 Ma, and the Mayerling mag- Moreover, new Ladinian U-Pb zircon dates are reported by (Storck neto-biostratigraphic sequence straddling the conodont Ladinian/Car- et al., 2018) from the western Dolomites from a bentonite layer within nian boundary interval. We traced magnetostratigraphically onto the Wengen Formation in the Punta Grohmann section Mayerling the Ladinian/Carnian boundary as defined by the FO of (237.58 ± 0.04 Ma; 237.68 ± 0.04 Ma), and from the Monzoni ammonoid D. canadensis at the Prati di Stuores GSSP (Mietto et al., (238.14 ± 0.05 Ma; 238.19 ± 0.05 Ma) and Predazzo 2012). The Ladinian is further constrained by the U-Pb zircon date of (238.08 ± 0.09 Ma) magmatic intrusions and dykes. The U-Pb dates 237.77 ± 0.05 Ma from Rio Nigra (Mietto et al., 2012; this study).

63 .Mrne al. et Maron M. Age Wayao (Ma) (China) 234 Prati di Stuores Bolücektasi Tepe Wa5 (Italy) Wa5 (Turkey) Wa4 Wa4 2.0 Conodont genera: Rio Nigra Mayerling (Italy) 1.5 235 P.: Paragondolella aon (Austria) 1 m BT7n Wa3 Wa3 N.: Nicoraella 200 1.0

180 BT6 Sirenites sp. Ps.: Pseudofurnishius S4n CARNIAN B.: Budurovignathus 160 Rio Frommer 236 S3r MA5r 0.5 140 (Italy) BT5 En.: Enantiognathus 120 S3n 60 Wa2 FO

G.: Gladigondolella S2r TRIASSIC LATE 100 BT4 Wa1r 0 Myr MA5 Daxatina 80 canadensis Ammonoid genera: S2n MA5n BT3 60 Paragondolella polygnathiformis 237 LCB 50 BT2r 40 S1r MA4r An.: Anolcites 20 S1n BT2n Gladigondolella tethydis Ps. murcianus murcianus MA4 40 Budurovignathus mungoensis BT1r

0 Frankites regoledanus Seceda 35 MA4n RN2n 237.77(4) ± 0.05 Ma 237.77 ± 0.05 Ma Correlation line (Italy) 30 Zestocerascf. nitidum

Paragondolellainclinata 238 regoledanus canadensis 25 GPTS Correlation 30 sp. Trachyceras MA3 SC6n MA3r RN1r 30 Frankites sp. 20

line 65 regoledanus 20 RF1n Protrachyceras ladinum Frankites regoledanus 15 10 Anolcites ? neumayri 60 Zestoceras nitidum SC5r Pg. foliata 10 RN1n 0 GS4n 20 MA3n diebeliB. MA2 GS3r.2r 55 polygnathiformisPg. 5 239.04 ± 0.10 Ma 239 GS3r.2n 25

50 0 mostleriB.

GS3r.1r MA2r neumayri 45 SC5n 45 10 40 GS3n 20 MA2n LADINIAN

239.04 ± 0.10 Ma (3) Metapolygnathuspolygnathiformis SL5n AT3n 40 Frotschbach SC4 35 20 SC4r MA1r (Italy) Budurovignathus sp. 240 30 AT2r 15 35 Margon MW2r SL4r GS2r SC4n MA1n SL4n 25 0 F2r (Italy) 240.28 ± 0.09 Ma

240.28 ± 0.09 Ma (3) ?An. neumayri Ps. murcianus praecursor SL3r G. malayensismalayensis 35 MW2n.2n 15 20 gredleri archelaus SC3r 240.58 ± 0.13 Ma SL3n AT2n.2n 10 GS2n.2n 10 30 240.58 ± 0.13 Ma (3) 30 MW2n.1r SL2r 15 AT2n.1r GD10n 30 F2n 10 Pg. praehungarica GS2n.1r M2n SC3 MW2n.1n SL2n 10 AT2n.1n 25 SC3n FO N. praehungaricaN. GS2n.1n GD9r 25 5 praehungaricaPg. 30 P3n 25 241 3.5 20 GD9n Eoprotrachyceras

5 N. praehungarica 5 SL1r AT1r GS1r

MW1r curionii SC2r E27 P2r curionii 0 15 ALB ALB 25 20 F1r.2r 20 GS1n 0 GD8r P2n F1r.1n M1r HC4r SC2 MW1n AT1n 0 seced. SC2n GD8n 0 10 241.71 ± 0.07 Ma (3) P1r 15 F1r.1r 241.71 ± 0.07 Ma 64 E26 Belvedere Gammsstein 1 GD7r 20 F1n.2n 15 M1n Mendlingbach West (Italy) Aghia Triada 5 SC1r GD7n 10 F1n.1r 15 242.01 ± 0.04 Ma GD7 242 (Austria) 242.01 ± 0.04 Ma (3) GD6r E25 P1n F1n.1n HC3n (Austria) (Greece) reitzi 0 GD6n SC1 HC3r GD6 E24 Pedraces praehungaricaN. (Italy) HC2n U-Pb ages: E23 GD5r S6r 10 E22 140 HC2r GD5 243 GD5n HC1n (1) Lehrmann et al., 2015 E21 S6n HC1r Budurovignathus truempyi (2) Lehrmann et al., 2006 120 S5r TRIASSIC MIDDLE (3) Wotzlaw et al., 2018 GD4r E20 S5n 5 (4) Mietto et al., 2012 244

100 Palaeogeography, Palaeoclimatology,Palaeoecology517(2019)52–73

Breccia S4r GD4 Kçira (Albania) 50 GD4n 80 ANISIAN E19 S4n S3r 0 245 40 Kç3r Deşli Caira E18 60 Holy Cross Mt. Chios A (Romania) GD3r (Greece) S3n (Poland) 0 m E17 Kç3n 40 35 S3n.1r 246 30 E16 Kç2r 12 Ch2n 30 DC2n GD3n S2r GD3 25 E15 S2n Kç2n 10 246.50 ± 0.11 Ma (1) 20 246.50 ± 0.11 Ma 20 S1r fault OAB 247.08 ± 0.11 Ma (1) E14 OAB OAB 15 OAB FO 8 247.32 ± 0.08 Ma (2) S1n Chiosella 20 Ch1r 10 DC1r 247.46 ± 0.05 Ma (1) E13 247.08 ± 0.11 Ma 247 Kç1r 0 timorensis 6 5 GD2r 247.32 ± 0.08 Ma GD2r 0 DC1n 405 kyr 247.46 ± 0.05 Ma Kç1r 4 cycles Upper Silesia Kç1n (Poland) 10 2 Ch1n 248 0 GD2n

Chiosella timorensis Chiosella timorensis GD2n Chiosella timorensis Chiosella timorensis

0 Kç1n.1r Upper Guandao OLENEKIAN (China) TR. EARLY 249

(caption on next page) M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Fig. 12. Magnetostratigraphic correlations of selected Middle Triassic sections: Kçira, Albania (Muttoni et al., 1996a); Chios, Greece (Muttoni et al., 1995); Deşli Caira, Romania (Gradinaru et al., 2007); Guandao, China (Lehrmann et al., 2006); Upper Silesia and Holy Cross Mountain, Poland (Nawrocki and Szulc, 2000); Pedraces and Belvedere, Italy (Brack and Muttoni, 2000); Aghia Triada, Greece (Muttoni et al., 1998); Mendlingbach West and Gammstein 1, Austria (Gallet et al., 1998); Frötschbach, Italy (Muttoni et al., 1996b, 1997); Margon, Italy (Gialanella et al., 2001); Prati di Stuores/Stuores Wiesen, Italy (Broglio Loriga et al., 1999; Mietto et al., 2012); Mayerling, Austria (Gallet et al., 1994, 1998); Seceda, Italy (Muttoni et al., 2004a); Bolücektasi Tepe, Turkey (Gallet et al., 1992); Wayao, China (Zhang et al., 2015); Rio Nigra and Rio Frommer, Italy (this work). U-Pb ages for Seceda are from Wotzlaw et al. (2018), from which the age of the Ladinian base is estimated at ~241.5 Ma, whereas the U-Pb age of Rio Nigra is from Mietto et al. (2012), from which the age of the Carnian base is estimated at ~236.8 Ma. FO of conodont Chiosella timorensis is from Guandao, South China (Anisian base; Lehrmann et al., 2006), base of Eoprotrachyceras curionii ammonoid Subzone is from Seceda, Italy (Ladinian base; Muttoni et al., 2004a; Wotzlaw et al., 2018), base of Daxatina canadensis ammonoid Subzone is from Prati di Stuores, Italy (Carnian base; Broglio Loriga et al., 1999; Mietto et al., 2012). Acronyms used for stage boundaries are: OAB for Olenekian/Anisian boundary; ALB for Anisian/Ladinian boundary; LCB for Ladinian/Carnian boundary.

4.3. Late Triassic (Carnian–Norian–Rhaetian) Carnian conodont-bearing Pignola-2 section of Italy (Rigo et al., 2007, 2012) was magnetostratigraphically correlated to Newark magnetozone The magnetostratigraphy of the early part of the Carnian (Julian) is E3 at ~231 Ma (Maron et al., 2017)(Fig. 13). The Carnian/Norian represented by marine sections at Prati di Stuores (Broglio Loriga et al., boundary, currently placed at the Pizzo Mondello section in Sicily in an 1999; Mietto et al., 2012), Mayerling (Gallet et al., 1994, 1998), and interval between the FOs of conodonts Metapolygnathus parvus and Bolücektasi Tepe in Turkey (Gallet et al., 1992), as well as the astro- Carnepigondolella gulloae (Mazza et al., 2010, 2012a; Onoue et al., 2018; nomically-tuned (100 and 405 kyr eccentricity cycles) ~2.4 Myr-long Rigo et al., 2018) within Pizzo Mondello magnetozone PM4r (Muttoni Wayao composite section from China (Zhang et al., 2015)(Fig. 13). et al., 2004b), was magnetostratigraphically traced to Newark magne- The Wayao section, comprised of the Zhuganpo Member (Falang tozone E7r at ~227 Ma (Krystyn et al., 2002; Muttoni et al., 2004b; Formation) overlain by the Xiaowa Member (Falang Fm.), has a com- Kent et al., 2017)(Fig. 13). Similar results were obtained also by plex biostratigraphic attribution based on apparently contradictory Channell et al. (2003) at the Silická Brezová section in Slovakia. Thus, conodont and ammonoid associations (e.g., Zhang et al., 2015 and re- using an age of ~236.8 Ma for the Ladinian/Carnian boundary (see ferences therein; Zou et al., 2015). In brief, the section is considered below) and ~227 Ma for the Carnian/Norian boundary, we obtain a Carnian in age essentially based on the presence of conodonts Para- ~9.8 Myr duration for the Carnian Stage (Fig. 13). The Carnian mag- gondolella polygnathiformis (=Metapolygnathus polygnathiformis) netostratigraphic record is probably incomplete as there is currently no throughout the Zhuganpo Mb. and Hayashiella nodosa (=M. nodosus) in reliable way to correlate or append the Wayao and Bolücektasi Tepe its uppermost beds (Zhang et al., 2015 and references therein), in as- magnetostratigraphies to the Newark-APTS or Pignola-2 section sociation with polygnathiformis-nodosa transitional forms (Zou et al., (Fig. 13; see also Kent et al., 2017). Awaiting further investigation, a 2015). The FO of P. polygnathiformis is closely associated with the base ~2 Myr gap is provisionally inserted between these two blocks of data of the Carnian at the Prati di Stuores GSSP (Broglio Loriga et al., 1999; (Fig. 13). This gap may straddle the Carnian Pluvial Episode, a distinct Mietto et al., 2012; see above), while H. nodosa first occurs shortly sedimentary episode particularly evident in the Dolomites (Bernardi afterwards still in the Carnian (e.g., Aghia Marina section; Muttoni et al., 2018 and references therein). et al., 2014). Zou et al. (2015) reported ammonoids from the Zhuganpo The Norian/Rhaetian boundary was dated through magnetostrati- Mb. that are largely endemic and of little chronological value, except graphic correlation of the Pignola-Abriola section from Italy (Maron for a Trachyceras assemblage in the upper part of the formation that et al., 2015), candidate GSSP for the Rhaetian Stage (Rigo et al., 2016; they attributed to the Carnian, whose base is indeed placed at the base Bertinelli et al., 2016), to the Newark APTS. At Pignola-Abriola, the of the Trachyceras Zone at the Prati di Stuores GSSP (Mietto et al., boundary is approximated by the FO of conodont Misikella posthernsteini 2012). In spite of this relatively clear indication of Carnian age for the sensu stricto within reverse magnetozone MPA5r (Maron et al., 2015). Zhuganpo Mb., Zou et al. (2015) tentatively attributed the pre-Tra- This level was magnetostratigraphically traced to Newark magnetozone chyceras endemic ammonoid association to the Ladinian and placed the E20r dated to ~205.7 Ma (Maron et al., 2015)(Fig. 13). This age is Ladinian/Carnian boundary in the upper part of the Zhuganpo Mb. We coherent with the U-Pb age estimate of Wotzlaw et al. (2014) for a level consider the arguments presented in Zou et al. (2015) in support of a close to the last occurrence of the Norian bivalve Monotis subcircularis at Ladinian age of the Zhuganpo Mb. as insufficient and maintain a Car- the Levanto section in Peru (205.50 ± 0.35 Ma). The Norian/Rhaetian 13 nian age for the formation and consequently for the Wayao composite boundary at Pignola-Abriola is also approximated by a negative δ Corg section as originally proposed by Zhang et al. (2015). Following these excursion (Maron et al., 2015; Rigo et al., 2016; Bertinelli et al., 2016) considerations, the magnetostratigraphy of the ~2.4 Myr-long Wayao that seems to be present in other marine sections (Zaffani et al., 2017). composite section is tentatively correlated to the upper part of the Previously, the Norian/Rhaetian boundary was placed in the Stein- Carnian Bolücektasi Tepe section (Fig. 13). bergkogel section, GSSP candidate for the Rhaetian Stage, at the FO of The remainder of the Late Triassic timescale is mostly represented M. posthernsteini sensu latu, and was magnetostratigraphically corre- by the continental Newark APTS (e.g. Kent et al., 1995; Kent and Olsen, lated to Newark levels at around 209 Ma (Krystyn et al., 2007a,b). M. 1999; Olsen and Kent, 1999; Olsen et al., 2011; Olsen et al., 2015; Kent posthernsteini sensu latu was later reinterpreted as a Misikella hernsteini/ et al., 2017) anchored to a U-Pb zircon age of 201.52 ± 0.03 Ma for posthernsteini transitional form (Maron et al., 2015; Rigo et al., 2016, the base of the Central Atlantic Magmatic Province (CAMP) basalts 2018; Bertinelli et al., 2016), following the new taxonomical definition (Blackburn et al., 2013), and altogether extending from ~232 Ma to of Giordano et al. (2010), from which was derived a recalibration of the ~199 Ma in the Early Jurassic (Kent et al., 2017)(Fig. 13). The Newark Norian/Rhaetian boundary at the FO M. posthernsteini sensu strictu at astrochronology was recently confirmed by results from the Petrified ~205.7 Ma as described above. Forest drill core project, where the U-Pb detrital zircon dates from core The Triassic/Jurassic boundary as approximated by the FO of am- PFNP-1A (210.08 ± 0.22 Ma, 212.81 ± 1.25 Ma, 213.55 ± 0.28 Ma, monoid Psiloceras spelae in the Levanto section (Peru) has been recently 214.08 ± 0.20 Ma; Fig. 13) have been linked to the Newark-APTS assigned an age of 201.36 ± 0.17 Ma (Wotzlaw et al., 2014) through through magnetostratigraphy (Kent et al., 2018). Moreover, the study the recalibration of previous U-Pb dates (Schoene et al., 2010; Guex demonstrated the stability of the 405 kyr eccentricity cycle, which was et al., 2012), falling in the basal part of magnetozone E24n in the used as a framework for the Newark APTS. Newark-Hartford APTS (Fig. 13). The carbon isotope excursions close to As a further confirmation of the Newark chronology, the U-Pb the Triassic/Jurassic boundary (Precursor, Initial and Main CIE), com- zircon date of 230.91 ± 0.33 Ma of Furin et al. (2006) from the monly related to the onset of the Central Atlantic Magmatic Province

65 .Mrne al. et Maron M.

Brumano Italcementi Quarry Age Steinbergkogel Steinbergkogel (Italy) (Italy) Newark-APTS (Ma) STK A STK B+C (USA) FO (Austria) 150 (Austria) Psiloceras E24 spelae 201 100 201 E24 EARLY JUR. 11 M-CIE 201.52 ± 0.03 Ma (3) 201.52 ± 0.03 Ma BIT5 202 Psiloceras planorbis 202 E23 E23 10 ST2/M+ SA6n 250 BIT5 50 20 BIT4 BIT4 M-CIE Pignola-Abriola SA5r 200 BIT3 203 E22 E22 203 9 10 150 0 m BIT3 (Italy) I-CIE

I-CIE E21 ST2/L-? SA5n 100 BIT2 204 E21 204

(Z.) FO 8 ST2/I+ 0 50 P-CIE RHAETIAN HETTANGIAN Misikella posthernsteini s.s.

BIT1 P-CIE Misikella 0 m 205 205 Misikella hernsteini 7 Mi. posthernsteini s.l. -10 E20 posthernsteini s.s. ST2/H- Silicka Brezova E20 50 peak

ST1/H- org 206 3 -20 206 MPA5r 6 ST2/G+ ST1/G+ (Slovakia) C NRB E19 13 E19 moniliformis ST2/F- ST1/F- SA4r 207 Proparvicingula 207 -30 s.s. 5 ST2/E+ 2 ST1/E+ 40 MPA5n E18 E18 ST2/D- SA4n 160 0 m MPA4r FO 208 ST1/D- -40 450 208 MPA4n 4 ST2/C+ Misikella ultima Misikella

1 -29 ‰ δ

ST1/C+ Rhaetavicula contorta SB-11r 30 ST2/B- -50 SA3r ? PF1r 209 E17 MPA3r E17 posthernsteini s.l. 209 3 ST1/B- 150 PM12r 0 m ST1/A+ SB-11n PM12n 210.08 PF2n s.l. -60 PF2r 210 MPA3n 210 SB-10r Betraccium 210.08 ± 0.22 Ma PM11r ± 0.22 Ma (2) 20

2 SA3n deweveri (Zone) -70 140 400 PM11n MPA2r E16 211 ST2/A+ 100 PF3n 211 E16 1 SA2r SB-10n MPA2n -80 PM10r 10 212 Misikella posthernsteini

Misikella posthernsteini s.s. 212.81 212 E. bidentata SA2n 130 PM10n MPA1r 0 m KV-19 ± 1.25 Ma (2) PF3r 212.81 ± 1.25 Ma E15 -90 E15 MPA1n 213 SB-9r Misikella hernsteini 213 0 m SA1r 350 PM9r PF4n 213.55 ± 0.28 Ma -100 213.55 Misikella hernsteini 120 SB-9n 214 214.08 ± 0.20 Ma 214 Misikella hernsteini ± 0.28 Ma (2)

Misikella hernsteini 200 PF4r Misikella posthernsteini E14 E14

Epigondolella mosheri A 215 St. Audrie’s Bay 215 Misikella hernsteini/posthernsteini PM9n KV-18 (UK) 110 214.08 PF5n

E. n. sp. D Mockinabidentata Parvigondolellaandrusovi 300 ± 0.20 Ma (2) 216 216 SB-8r KV-17 KV-16 100 217 217 SB-8n PM8r E13 E13 Mockina bidentata Petrified Forest NORIAN KV-15 Parvigondolella andrusovi 218 218 PM8n (USA) 90 SB-7r 250 219 E12 219 KV-14 E. multidentata E12 E. spatulata SB-7n 66 80 220 220 KV-13 SB-6r PM7r E11 SB-6n E11

Mockina bidentata 221 221 SB-5r 200 70 SB-5n KV-12 222 222 PM7n E10 E10 E. triangularis

SB-4r LATE TRIASSIC 223 223 KV-11 60 KV-10 E9 E9 KV-9 SB-4n 150 224 224 10 KV-8 PM6r Pignola 2 KV-7 50 SB-3r 225 (Italy) 225 KV-6 FO Carnepigondolella gulloae E. abneptis A Carnepigondolellatuvalica PM6n Paragondolella noah E8 E8 Carnepigondolella 226 Paragondolella carpathica PM5r 226 gulloae KV-5 M. communisti B 40 SB-3n PM5n Palaeogeography, Palaeoclimatology,Palaeoecology517(2019)52–73 100 Metapolygnathusechinatus

Me.praecommunisti CNB 227 227 0 m KV-4 PM4r M. pseudodiebeli E7 FO KV-3 30 PM4n E7 SB-2r 228 Metapolygnathus 228

Epigondolella rigoi PM3r KV-2 parvus KV-1 M. nodosus 229 E6 E6 229 20 50 PM3n Pg. polygnathiformis 20 Me. praecommunisti 230 E5 230 Paragondolella polygnathiformis E5 Kaavalani SB-2n Ma (1) MP5 Epigondloella quadrata PM2r

Me. communisti 15 E4 Epigondolella rigoi (Turkey) 10 Epigondolella triangularis 231 E4 MP4 230.91 ± 0.33 Ma 231 PM2n E3 E3 10 MP3 Gladigondolella sp. E2 Paragondolella oertlii SB-1r 0 m PM1 232 E2 ± 0.33 MP2 232

Metapolygnathus parvus 5 SB-1n 1 E1 0m Ma MP1 Pg. noah E1 Wayao ABBREVIATIONS 0 m 233

230.9 (China)

Pizzo Mondello CARNIAN Upper Mayerling U-Pb ages: (Italy) BT7n Wa5 Wa5 234 aon 200 (Austria) Conodont genera: Wa4 Wa4 S4 1 m BT6 2.0 Pg.: Paragondolella 160 235 (1) Furin et al., 2006 S3 MA5r BT5 Wa3 Wa3 FO 120 60 1.0 Me.: Metapolygnathus BT4 Daxatina 236 (2) Kent et al., 2018 Wa2 80 S2 BT3 MA5 canadensis Mi.: Misikella Pg. polygnathiformis LCB 50 MA5n BT2r Wa1 0 Myr (3) Blackburn et al., 2013 40 237 MA4r S1 Sirenites sp. MA4 0 BT2n 237.77 ± 0.05 Ma Carbon Isotopes Excursion (CIE): 40 BT1r 238 Correlation line MA4n M-CIE: Main CIE GPTS Correlation regoledanus canadensis I-CIE: Initial CIE LADINIAN Trachyceras sp.

line polygnathiformis P-CIE: Precursor CIE Prati di Stuores MIDDLETR. (Italy) Me. Bolücektasi Tepe Pg.polygnathiformis (Turkey)

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Fig. 13. Magnetostratigraphic correlations of selected Late Triassic sections and cores: Prati di Stuores, Italy (Broglio Loriga et al., 1999; Mietto et al., 2012); Mayerling, Austria (Gallet et al., 1994, 1998); Bolücektasi Tepe, Turkey (Gallet et al., 1992); Wayao, China (Zhang et al., 2015); Pignola-2, Italy (Maron et al., 2017); Silická Brezová, Slovakia (Channell et al., 2003); Kaavalani, Turkey (Gallet et al., 2000b); Pizzo Mondello, Italy (Muttoni et al., 2004b); Newark-APTS 2017, USA (Kent et al., 2017); Petrified Forest, USA (Kent et al., 2018); Pignola-Abriola, Italy (Maron et al., 2015); Steinbergkogel, Austria (Krystyn et al., 2007a, b); St. Audrie’s Bay, UK (Hounslow et al., 2004); Brumano and Italcementi Quarry, Italy (Muttoni et al., 2010, 2014). Conodont biostratigraphy of Silická Brezová is after Mazza et al. (2010, 2011, 2012a, b) and Maron et al. (2017). The 227 Ma age of the base of the Norian is based on magnetostratigraphic correlation of Pizzo Mondello and the Newark APTS (Muttoni et al., 2004b; Mazza et al., 2012a; Kent et al., 2017). The 205.7 Ma age of the Rhaetian base is based on magnetostratigraphic correlation of Pignola-Abriola and the Newark APTS (Maron et al., 2015) and the 201.36 Ma age of the Hettangian is from Wotzlaw et al. (2014). U-Pb ages in Furin et al. (2006) are from Pignola 2, in Kent et al. (2018) from Chinle Fm. in Petrified Forest, and in Blackburn et al. (2013) from Palisades Sill. Carbon Isotopes Excursions (CIE) in Brumano and Italcementi Quarry sections are from Zaffani et al. (2018); CIEs in St. Audrie’s Bay section are from Hesselbo et al. (2002, 2004). Base of Daxatina canadensis ammonoid Subzone is from Prati di Stuores, Italy (Ladinian base; Broglio Loriga et al., 1999; Mietto et al., 2012), FOs of conodonts Metapolygnathus parvus and Carnepigondolella gulloae are from Pizzo Mondello, Italy (Norian base; Mazza et al., 2012a), FO of conodont Misikella posthernsteini s.s. is from Pignola-Abriola, Italy (Rhaetian base; Maron et al., 2015; Rigo et al., 2016; Bertinelli et al., 2016; Zaffani et al., 2017), FO of Psiloceras spelae is from Levanto, Peru (Hettangian base; Schoene et al., 2010; Guex et al., 2012; Wotzlaw et al., 2014). See text for discussion. Acronyms used for stage boundaries are: LCB for Ladinian/Carnian boundary; CNB for Carnian/Norian boundary; NRB for Norian/Rhaetian boundary.

(e.g. Marzoli et al., 2004; Hesselbo et al., 2007; Deenen et al., 2010; Dal at Pignola-Abriola by the FO of conodont Misikella posthernsteini sensu Corso et al., 2014; Davies et al., 2017) and associated with the end- stricto (Maron et al., 2015). With a Rhaetian base at 205.7 Ma, the Triassic extinction event (e.g. Hesselbo et al., 2002; Guex et al., 2004; Norian Stage is estimated to be ~21.3 Myr long. According to the Ward et al., 2004; Richoz et al., 2007; Van de Schootbrugge et al., 2008; Triassic/Jurassic boundary age of 201.36 ± 0.17 Ma (Wotzlaw et al., Tanner, 2010; Whiteside and Ward, 2011; Hillebrandt et al., 2013; 2014), the duration of the Rhaetian is ~4.3 Myr and the duration of the Zaffani et al., 2017; Lucas and Tanner, 2018), are located in the murky Late Triassic (Carnian, Norian and Rhaetian) is ~35.4 Myr. SA5n.2n–SA6n magnetostratigraphic interval of the St. Audrie's Bay section (Hesselbo et al., 2002, 2004; Hounslow et al., 2004) and in the BIT2r–BIT5n interval of Brumano/Italcementi Quarry (Muttoni et al., 4.4. Summary and error estimates 2010; Zaffani et al., 2018), which broadly correspond to the E22n-E24n interval in the Newark-APTS (Fig. 13). As described above and illustrated in Figs. 11–13, we selected key In summary, we adopted as reference sections to construct our Late Tethyan marine magnetostratigraphic sections as “building blocks” for Triassic GPTS the astronomically tuned ~2.4 Myr-long Wayao compo- the construction of a GPTS that embraces the entire Triassic System site magnetostratigraphy (Zhang et al., 2015) and the Newark APTS from the Changsinghian/Induan (Permian/Triassic) boundary to the (Kent et al., 2017) provided at the base and in the mid-part with U-Pb Rhaetian/Hettangian (Triassic/Jurassic) boundary for a total duration zircon age constraints from Pignola-2 (Furin et al., 2006; Maron et al., of ~50.5 Myr (Fig. 14; magnetozone ages and durations are in Sup- 2017) and the Petrified Forest drill core (Kent et al., 2018), respec- plemental Table S2). Reference sections have been selected among tively. We traced magnetostratigraphically onto the Newark APTS at those deemed to have minimum variations in sediment accumulation the ~227 Ma the level of the Carnian/Norian boundary as defined at rates (as reflected by lithological variations) and to be provided withU- Pizzo Mondello (Muttoni et al., 2004b) between the FOs of conodonts Pb age constraints (see Table 2 for a summary) and/or biostratigraphic Metapolygnathus parvus and Carnepigondolella gulloae (Mazza et al., datums useful to define stage boundaries. For the Late Triassic, we 2012a; Onoue et al., 2018; Rigo et al., 2018). We also traced onto the adopted the Newark APTS correlated to stage boundaries from Tethyan Newark-APTS at ~205.7 Ma the Norian/Rhaetian boundary as defined marine sections. We also opted to maintain in our composite GPTS the magnetozone nomenclature of the constituent reference sections (e.g.,

Table 2 Radiometric datings and Stage boundaries ages.

Age (Ma) Locality Stage Event Magnetozone (GPTS) Reference

251.902 ± 0.024 Meishan (South China) Induan FO Hindeodus parvus; Changhsingian-Induan boundary Me3n Burgess et al., 2014 ~249.7 Guandao (South China) Olenekian FO Neospathodus waageni; Induan-Olenekian boundary GDL5n This study 247.46 ± 0.05 Guandao (South China) Olenekian GD2r/Kç1r Lehrmann et al., 2015 247.32 ± 0.08 Guandao (South China) Olenekian GD2r/Kç1r Lehrmann et al., 2006 247.28 ± 0.12 Guandao (South China) Anisian FO Chiosella timorensis; Olenekian-Anisian boundary GD2r/Kç1r Lehrmann et al., 2015 247.08 ± 0.11 Guandao (South China) Anisian GD2r/Kç1r Lehrmann et al., 2015 246.50 ± 0.11 Guandao (South China) Anisian GD3n Lehrmann et al., 2015 242.010 ± 0.040 Seceda (Italy) Anisian GD7r/SC1r Wotzlaw et al., 2018 241.705 ± 0.065 Seceda (Italy) Anisian SC2n Wotzlaw et al., 2018 ~241.4 Seceda (Italy) Ladinian FO Eoprotrachyceras curionii; Anisian-Ladinian boundary SC2r This study; Wotzlaw et al., 2018 240.576 ± 0.126 Seceda (Italy) Ladinian SC3n Wotzlaw et al., 2018 240.285 ± 0.095 Seceda (Italy) Ladinian SC4n Wotzlaw et al., 2018 239.044 ± 0.104 Seceda (Italy) Ladinian MA2n Wotzlaw et al., 2018 237.773 ± 0.052 Rio Nigra (Italy) Ladinian MA4n Mietto et al., 2012 ~236.8 Prati di Stuores (Italy) Carnian FO Daxatina cf. canadensis; Ladinian-Carnian boundary MA5n This study 230.91 ± 0.33 Pignola 2 (Italy) Carnian E3r Furin et al., 2006 ~227 Pizzo Mondello (Italy) Norian FO Metapolygnathus parvus; FO Carnepigondolella gulloae; E8n Mazza et al., 2012a; Carnian-Norian boundary Onoue et al., 2018 ~207.5 Pignola-Abriola (Italy) Rhaetian FO Misikella posthernsteini s.s.; Norian-Rhaetian boundary E20r Maron et al., 2015 214.08 ± 0.20 Petrified Forest (USA) Norian E14r Kent et al., 2018 213.55 ± 0.28 Petrified Forest (USA) Norian E14r Kent et al., 2018 212.81 ± 1.25 Petrified Forest (USA) Norian E15n Kent et al., 2018 210.08 ± 0.22 Petrified Forest (USA) Norian E16r Kent et al., 2018 201.520 ± 0.034 Newark Basin (USA) Rhaetian Palisades sill – Central Atlantic Magmatic Province (CAMP) E24n Blackburn et al., 2013

67 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Fig. 14. Proposed geomagnetic polarity time scale Triassic GPTS (GPTS) for the Triassic, derived from a magnetos- Age (this study) tratigraphic composite of selected Tethyan marine sections integrated with key nonmarine sequences (Ma) FO P. spelae and U-Pb dates and astrochonologies (Figures E. JURASSIC E. E24 201 HETTANGIAN 201.52 ± 0.03 Ma8 11–13). Key U-Pb ages are on the left side of the E23 GPTS (marked by blue lines), while on the right are 203 E22 reported the main biostratigraphic markers of the E21 Stage boundaries (marked by green lines), the 205 FO RHAETIAN M. posth. s.s. E20 ranges of the reference stratigraphic sections used to compile the GPTS and the range of the age con- 207 E19 E18 straints used to compile the GPTS (astrochronology or U-Pb datings). References of the U-Pb ages are: 1) 209 E17 Burgess et al., 2014; 2) Lehrmann et al., 2015; 3) 210.08 ± 0.22 Ma7 Lehrmann et al., 2006; 4) Wotzlaw et al., 2018; 5) 211 E16 Mietto et al., 2012; 6) Furin et al., 2006; 7) Kent et al., 2018; 8) Blackburn et al., 2013. References for 212.81 ± 1.25 Ma7 213 E15 213.55 ± 0.28 Ma7 the age constraints are: a) Li et al., 2016, 2018; b) 214.08 ± 0.20 Ma7 e Wotzlaw et al., 2018; c) Mietto et al., 2012; d) 215 E14 Zhang et al., 2015; e) Kent et al., 2017.

217 E13 NORIAN

219 E12 APTS 2017 Newark Newark-APTS 221 E11

LATE TRIASSIC E10 223 E9 225 FO E8 Ca. gulloae 227 FO E7 229 Me. parvus E6 E5 E4 230.91 ± 0.33 Ma6 231 E2 E3 E1 233 CARNIAN Wa5 Wa4 235 d FO Wa3 Wayao D. canadensis

MA5 Wayao 237 5 MA4 c 237.77 ± 0.05 Ma b MA3 239.04 ± 0.10 Ma4 239 MA2 Mayerling 4 SC4 240.28 ± 0.09 Ma FO 4 Seceda 240.58 ± 0.13 Ma LADINIAN SC3 241 E. curionii Rio Nigra 241.71 ± 0.07 Ma4 SC2

4 GD7/SC1 Seceda 242.01 ± 0.04 Ma GD6 243 GD5 a GD4 245 MIDDLE TRIASSIC 246.50 ± 0.11 Ma2 ANISIAN FO GD3 247.08 ± 0.11 Ma3 C. timorensis

247 Guandao 247.32 ± 0.08 Ma2 GD2r/Kç1r 247.46 ± 0.05 Ma2

GD2n Kçira FO GD1 249 N. waageni OLENE. GDL6 Ch2 GDL5 FO 251 Ch1r/Me3r South China APTS South China 1 E. TRIASSIC H.parvus 251.88 ± 0.03 Ma INDUAN Me3n 251.94 ± 0.04 Ma1 Me2 253 Me1r LowerChaohu Meishan

405 Kyr U-Pb zircon eccentricity cycles ages CHANGHSINGIAN LATE PERMIAN

SC for Seceda, E for Newark, etc.; Fig. 14) Finally, we opted to exclude discontinuities in polarity records. For the Early Triassic and the early from our final composite GPTS (Fig. 14) polarity intervals based on Late Triassic (Carnian), potential errors could be due to missing ec- single samples (represented as half bars in Figs. 11–13). centricity (100 or 405 kyr) beats in the reference APTSs of South China Potential errors propagating through the GPTS are those inherited (Li et al., 2016, 2018) and Wayao (Zhang et al., 2015) due, for example, from the radiometric and astrochronology methods applied, as well as to the presence of subtle gaps or unconformities, although no report in the usual correlation uncertainties from provinciality of biozones and this sense has been presented by the above-referenced authors. Missing

68 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73

Fig. 15. A comparison between the Early Triassic A Triassic GPTS (this study) APTS from the Germanic Basin (Szurlies, 2004, 239 2007) and the Early Triassic GPTS (this study) is SC4 shown in Panel A. Following the method outlined in

241 LADINIAN SC3 Muttoni et al. (2004a), we obtained a best correla- SC2 GD7/SC1 tion option (red correlation lines) that optimizes the GD6 match between magnetozone durations in the GPTS 243 GD5 German Basin APTS of this study and the Germanic Basin APTS (Panel B GD4 (Szurlies 2004, 2007) with indication of correlation coefficient R). This 245 MIDDLE TRIASSIC optimal correlation is significant at 95% level ac- ANISIAN GD3 cording to a Student t test. The derived Age-Age 6 CG11 247 GD2r/Kç1r CG10 function of this best correlation option is shown in CG9 GD2n 5 Panel C. The 95% confidence interval (blue line) GD1 CG8 249 4 CG7 associated to linear regression (red line) is marked in OLENE. GDL6 GDL5 3 CG6 both the correlation (Panel B) and Age-Age plots Ch2 CG5 251 Ch1r/Me3r 2 (Panel C). See text for discussion. E. TRIASSIC CG4 INDUAN Me3n 1 CG3 Me2 CG2 253 Me1r Age Age (Myr) L. PERM.

(Ma) CHANGHS. B Statistical Correlation C Age vs. Age plot 2.5 8 7 2.0 6 1.5 5 1.0 4 0.5 3 2 0.0 1 (German Basin APTS) (German Basin -0.5 APTS) (German Basin 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Ages of magnetozones in Myr Duration of magnetozones in Myr Duration of magnetozones in Myr -1 (GPTS; this study) 253 252 251 250 249 248 247 246 Ages of magnetozones in Ma Regression R= 0.759 (GPTS; this study) Line t = 3.691 95% 95% Regression Degrees of freedom = 10 Confidence Confidence Line Interval Correlation confidence = 95% Interval

eccentricity (405 kyr) beats in the Late Triassic Newark-APTS (Kent 5. Comparison with other polarity timescales et al., 2017) are much less probable, at least in the younger part of the APTS as recently confirmed by high-precision U-Pb zircon dates back to As described above, the Induan–Anisian (Early–early Middle E14r from the Petrified Forest drill core (Kent et al., 2018). This leaves Triassic) part of our composite GPTS is based on the same set of stra- almost a 17 Myr interval between available U-Pb dates of tigraphic sections (Meishan, lower Chaohu, upper Chaohu, and 214 ± 0.2 Ma from Petrified Forest correlated to E14r and Guandao) used in the South China APTS of Li et al. (2016, 2018), with 230.91 ± 0.33 Ma from Pignola 2 correlated to E4n that relies on the however two notable differences concerning the use of the Guandao astrochronology of the Newark-APTS. In the case of the Middle Triassic, and Germanic Basin magnetostratigraphies. The Li et al. (2016, 2018) the reference Seceda age model is well controlled by a half-dozen U-Pb correlation grid had a gap in the Olenekian between the lower Chaohu dates and mainly subject to errors defined through the 95% confidence and the upper Chaohu sections essentially because the lower part of the limits of the Bayesian method used, which suggests maximum un- Guandao section from magnetozone GDL1 to GD1 (Lehrmann et al., certainties of ~200 kyr (Wotzlaw et al., 2018). 2006), which would nicely straddle the magnetostratigraphic gap, did When astrochronology is not available and the radiometric age tie- not yield useful cyclostratigraphic data. Hence, the gap was filled by points are wide apart, as in the late Ladinian–Early Carnian, we applied importing magnetostratigraphic and cyclostratigraphic data (100 kyr a simple linear interpolation between the nearest U-Pb dates and ac- cycles) from cores in the continental Germanic Basin (Szurlies, 2004, commodated sedimentation rates of the correlated sections accordingly. 2007). Instead, giving priority to expanded records in stratigraphic Errors in this interval are therefore inherited from the uppermost U-Pb continuity, we prefer to adopt the entire Guandao magnetostratigraphy age at Seceda (239.044 ± 0.104; Wotzlaw et al., 2018) and the Rio (from magnetozone GDL1 at the base to magnetozone GD10 at the top), Nigra U-Pb age (237.773 ± 0.052; Mietto et al., 2012), while potential in association with Meishan and Chaohu, as the reference magnetos- errors originating in the intervening interpolated part of the GPTS, tratigraphy for the Induan–Olenekian time interval (see Section 4.1). based on magnetostratigraphic data from the apparently continuous We then used the Germanic Basin magneto-cyclostratigraphy as an in- Mayerling (Gallet et al., 1994, 1998) reference section, are at present dependent test to validate our GPTS following the correlation method not readily assessable. The various age constraints (and associated po- outlined in Muttoni et al. (2004b). The Germanic Basin sequence in tential errors) adopted through the GPTS are shown in Fig. 14 (details floating age coordinates (based on the 100 kyr cycles; Szurlies, 2007) on U-Pb age constraints in Middle Triassic, and associated errors, are was placed aside the Early–early Middle Triassic portion of our GPTS. A provided in Supplemental Fig. S2). linear correlation coefficient (R) relating the duration of each of the N = 12 complete Germanic Basin polarity zones to the duration of the

69 M. Maron et al. Palaeogeography, Palaeoclimatology, Palaeoecology 517 (2019) 52–73 correlative chrons in our GPTS was calculated, from which a t value was Triassic boundary at 251.9 Ma based on U-Pb zircon dates around the derived using the equation t = R*sqrt[(N-2) / (1-R2)]. The Germanic FO of conodont Hindeodus parvus at the Meishan GSSP, China. Induan/ Basin sequence was then slid by two polarity zones along the GPTS, R Olenekian boundary at 249.7 Ma, astrochronological age of the FO of and t were recalculated, and the exercise was repeated until all possi- conodont Neospathodus waageni at Guandao (China). Olenekian/Anisian bilities in the Early–early Middle Triassic interval were explored. We boundary at 247.3 Ma based on U-Pb dates around the FO of conodont obtained a positive statistical correlation match (significant at 95% Chiosella timorensis at Guandao, China. Anisian/Ladinian boundary at level) that is stratigraphically meaningful and provides support for the 241.5 Ma based on U-Pb zircon dates from Seceda, Italy, of a level validity of both timescales and the duration of the Early Triassic correlated to the base of the Eoprotrachyceras curionii ammonoid Zone at (Fig. 15; preferred correlation option is shown in Panel A; the statistical the Bagolino GSSP, Italy. Ladinian/Carnian boundary at 236.8 Ma, es- parameters R and t are shown with the preferred linear correlation timated age of the FO of ammonoid Daxatina canadensis at the Prati di option plot in Panel B). An age-age plot has been obtained according to Stuores GSSP. Carnian/Norian boundary at ~227 Ma, estimated age of the preferred correlation between the Early Triassic GPTS and the a level between the FOs of conodonts Metapolygnathus parvus and Germanic Basin APTS (Fig. 15C), showing slight deviations from line- Carnepigondolella gulloae at Pizzo Mondello, Italy. Norian/Rhaetian arity that could be imputable to the uncertainty of cycle-derived ages boundary at 205.7 Ma, estimated age of FO of conodont Misikella between the Early Triassic GPTS and the Germanic Basin APTS. posthernsteini sensu stricto at Pignola-Abriola, Italy. Triassic/Jurassic As stated previously, our revised Triassic GPTS shows differences boundary at 201.4 Ma, based on U-Pb zircon age of the FO of ammonite relative to Hounslow and Muttoni (2010) that essentially arise from the Psiloceras spelae at Levanto section, Peru. use we make here of magnetozone sequences and nomenclatures from a According to these stage boundary ages, the Induan Stage more strict inventory of Tethyan marine sections for the Early–Middle (251.9–249.7 Ma) is estimated to be ~2.2 Myr-long, the Olenekian Triassic, less strict reliance on biozones for correlation, as well as the Stage (249.7–247.3 Ma) ~2.4 Myr-long, the Anisian Stage availability since 2010 of additional magneto-bio-cyclostratigraphic (247.3–241.5 Ma) ~5.8 Myr-long, the Ladinian Stage (241.5–236.8 Ma) data (e.g., Maron et al., 2015; Li et al., 2016; this study) sometimes ~4.7 Myr-long, the Carnian Stage (236.8–227 Ma) ~9.8 Myr-long, the calibrated with new U-Pb zircon dates and age models (e.g., Wotzlaw Norian Stage (227–205.7 Ma) ~21.3 Myr-long, and the Rhaetian Stage et al., 2018; this study). Moreover, we adopted here the entire Newark (205.7–201.4 Ma) ~4.3 Myr-long. The average geomagnetic polarity APTS as key reference timescale for the Late Triassic (Late Car- reversal frequency for the Early Triassic (251.9–247.3 Ma) is ~3 rev/ nian–Rhaetian), onto which fossil-based stage boundaries and U-Pb Myr, of the Middle Triassic (247.3–236.8 Ma) is ~2.5 rev/Myr, and of ages have been traced from various Tethyan marine sections by means the Late Triassic (236.8–201.4 Ma) is ~1.4 rev/Myr (Supplementary of magnetostratigraphy, whereas Hounslow and Muttoni (2010) opted Table S2). for a composite Late Triassic sequence based exclusively on Tethyan Main future improvements of this timescale would include filling marine sections, which was tested against the Newark APTS according the Carnian magnetobiostratigraphic gap between Wayao, Pignola-2, to three correlation options (A, B, C; figure 12 in Hounslow and and the base of the Newark APTS; improving coverage in the Ladinian Muttoni, 2010). interval presently represented by the upper Seceda and lower Mayerling These differences are inevitably reflected also inthe Ogg (2012b) sections; and providing additional numeric age constraints for the timescale that uses for the Triassic a slightly modified version of the Ladinian/Carnian, Carnian/Norian, and Norian/Rhaetian boundaries. Hounslow and Muttoni (2010) timescale [for example, see the debate in Another improvement would be to delineate new magnetostratigraphic Ogg (2012b) on the “long-Tuvalian” versus “long-Rhaetian” correlation sections containing the 405 kyr climate beat, which is likely to have a options that derives from options A vs. B in Hounslow and Muttoni fixed single period back to the base of the Triassic. (2010)]. Differences of our Triassic GPTS are relatively reduced relative Supplementary online material (available in Mendeley Data to the more recent Ogg et al. (2016) timescale that adopts, as we do, the Repository) includes the following data: ChRM data (Supplemental South China APTS of Li et al. (2016) for the Early Triassic (but see Table S1); ages and durations of the GPTS chrons and reversal fre- above), and a Late Triassic composite magnetostratigraphy that is still quencies in the Early, Middle and Late Triassic (Supplemental Table derived from Hounslow and Muttoni (2010) but is correlated to the S2). Stereograms of Anisotropy of Magnetic Susceptibility (AMS), F-L Newark APTS according to the “long-Rhaetian” option (essentially plots and Jelinek plots are available as Supplemental Fig. S1. A plot equivalent to option A of Hounslow and Muttoni, 2010) that is more with the U-Pb age constraints used to build the Middle Triassic GPTS, consistent with our solution (see also Muttoni et al., 2010; Maron et al., and related errors, is available as Supplemental Fig. S2. Supplementary 2015). Finally, our GPTS differs from Hounslow et al. (2018) insofar as data associated with this article can be found in the online version, at these authors averaged the durations (or thicknesses) of magnetozones doi: https://doi.org/10.1016/j.palaeo.2018.11.024. from correlative sections, thus obtaining a composite average magne- tozone sequence, whereas we chose to select key sections for each Acknowledgments chronostratigraphic interval and use them as reference sections for the GPTS construction. This research was supported by IAS (International Association of Sedimentologists) Post-doctoral Research Grant 2016 to Matteo Maron. 6. Conclusions Funding for this research was provided through PRAT CPDA152211/15 to Manuel Rigo by the University of Padova. Dennis Kent thanks the US We presented the magnetostratigraphy of the Rio Nigra and Rio National Science Foundation (Sedimentary Geology and Paleobiology Frommer sections from the Dolomites calibrated with a U-Pb zircon Program) and the Director of Lamont-Doherty Earth Observatory for date of 237.77 ± 0.05 Ma and provided with ammonoid and conodont support of his contribution to this research. LDEO Contribution #8268. biostratigraphy. These new data contribute to the chronology of the The authors wish to thank anonymous Reviewer 1 and Reviewer 2 Ladinian, represented thus far mainly by the radiometrically un- (Mark Hounslow) for their valuable comments. The authors would like constrained Mayerling marine section (Gallet et al., 1994, 1998). Using to dedicate this paper to the late Maurizio Gaetani (1940 – 2017). these new data in conjunction with a total of 35 selected magnetos- tratigraphic sequences from the literature, we constructed an updated References Triassic GPTS from the Permian/Triassic boundary to the Triassic/ Jurassic boundary (Newark APTS for the Late Carnian–Rhaetian) for a Bernardi, M., Gianolla, P., Petti, F.M., Mietto, P., Benton, M.J., 2018. Dinosaur diversi- total duration of ~50.5 Myr. fication linked with the Carnian Pluvial Episode. Nat. Commun. 9 (1499). https:// doi.org/10.1038/s41467-018-03996-1. Stage boundaries correlated to the GPTS are as follows: Permian/

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