Cretaceous Research 127 (2021) 104950 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes n Upper JurassiceLower Cretaceous calpionellid zones in the Neuque Basin (Southern Andes, Argentina): Correlation with ammonite zones and biostratigraphic synthesis lez Tomassini c, Diego A. Kietzmann a, b, *, Maria Paula Iglesia Llanos a, b, Federico Gonza c d d n Reijenstein Ivan Lanusse Noguera , Dolores Vallejo , Herna a gicas, Ciudad Universitaria, Pabello n II, Intendente Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Ciencias Geolo noma de Buenos Aires, Argentina Güiraldes 2160, C1428EHA, Ciudad Auto b sicas, Ambientales y Aplicadas de Buenos Aires (IGeBA), Ciudad Universitaria, Pabello n CONICET-Universidad de Buenos Aires, Instituto de Geociencias Ba noma de Buenos Aires, Argentina II, Intendente Güiraldes 2160, C1428EHA, Ciudad Auto c noma de Buenos Aires, Argentina YPF S.A, Bv. Macacha Güemes 515, C1106BKK, Ciudad Auto d n 925, C1008, Ciudad Auto noma de Buenos Aires, Argentina Chevron Argentina, Pres. Tte. Gral. Juan Domingo Pero a r t i c l e i n f o a b s t r a c t Article history: Received 21 November 2020 Received in revised form 30 June 2021 Accepted in revised form 30 June 2021 Available online 8 July 2021 This work presents the first regional biostratigraphic study on the calpionellid zones and assemblages of n Basin, Southern Andes, Western Argentina. the Tithonianelower Valanginian interval in the Neuque n Basin is mainly represented by the Vaca Muerta The lower Tithonianelower Valanginian in the Neuque Formation, which is a thick sucession (100e1250 m thick) of rhythmic marlstone and limestone alternations corresponding to the distal hemipelagic facies of a carbonate ramp. This formation is one of the most important unconventional hydrocarbon reservoirs in the world and has become a relevant target in Argentina during the last decade. The Vaca Muerta Formation is characterized by an abundant fossil content and a remarkable stratigraphic continuity along several hundred meters, encompassing the Jurassic/Cretaceous boundary. The detailed study of seven outcrop and well sections (three of them studied for the first time herein), allowed the elaboration of a reliable stratigraphic scheme based on the correlation of ammonites, microfossils, magnetostratigraphy and cyclostratigraphy. The Vaca Muerta Formation contains moderate to poorly preserved calpionellids. Despite that, twenty-six calpionellid species and five calpionellid biozones known in the Tethyan regions have been identified: Chitinoidella, Crassicollaria, Calpionella, Calpionellopsis and Calpionellites. Additionally, nine subzones were recognized: Slovenica, Boneti, Remanei, Massutiniana, Alpina, Elliptica, Simplex, Oblonga, and Darderi. These results allow chronostratigraphic correlations between the Tethys and the Southeastern Pacific domains. © 2021 Elsevier Ltd. All rights reserved. Keywords: Biostratigraphy Calpionellids Jurassic/Cretaceous boundary Vaca Muerta Formation 1. Introduction Calpionellids represent a well-known group of planktonic protozoa widely distributed in the Tethyan Realm during the Late JurassiceEarly Cretaceous. They are often used during the latest * Corresponding author. Universidad de Buenos Aires, Facultad de Ciencias Exgicas, Ciudad Universitaria, actas y Naturales, Departamento de Ciencias Geolo n II, Intendente Güiraldes 2160, C1428EHA, Ciudad Auto noma de Buenos Pabello Aires, Argentina. E-mail addresses: [email protected] (D.A. Kietzmann), mpiglesia@ gl.fcen.uba.ar (M.P.I. Llanos), [email protected] (F.G. Tomassini), ivan. [email protected] (I.L. Noguera), [email protected] (D. Vallejo), [email protected] (H. Reijenstein). https://doi.org/10.1016/j.cretres.2021.104950 0195-6671/© 2021 Elsevier Ltd. All rights reserved. years in assessing Upper JurassiceLower Cretaceous biostratigraphy, due mainly to their rapid evolution, widespread paleogeographic distribution, as well as similar stratigraphic ranges in remote areas, and accordingly, allow reliable long-range correlations between the Tethyan provinces (e.g., Benzaggagh, 2020; Grün and Blau, 1997; Lakova and Petrova, 2013; Michalík et al., 2009; Remane, 1971; Scott, 2019; and references therein). Reports of calpionellids in mid and high latitudes of the Southern Hemisphere are scarce and had been practically unknown in Argentina until ndez Carmona et al., 1996; Ferna ndez Carmona recent times (Ferna and Riccardi, 1998, 1999; Kietzmann et al., 2011a; Kietzmann, 2017; pez Martinez et al., 2017). Lo D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 n Basin (western Argentina) and location of the studied sections: 1) Tres Esquinas, 2) Arroyo Loncoche, 3) Cuesta del Chihuido, 4) Las Loicas, 5) Cara Cura, Fig. 1. Map of the Neuque 6) Puerta Curaco. 2, 3, and 6 are sections studied in this work. 1, 4, and 5 are previous studied sections mentioned in the text. Gray lines indicate thermal maturity curves based on vitrinite reflectance equivalents: oil and wet-gas window between 0.6 and 1.3%VRr, and gas window between 1.3 and 2%VRr. FTB: fold and thrust belt. The Jurassic and Cretaceous successions in the Andes Domain are characterized by hundreds to thousands of meters thick marine deposits bearing abundant fossils, intercalated with ashes from the volcanic arc on the west. This is observed in the Tithonianelower Valanginian deposits, made up of thick rhythmic marlstones and limestones succession known as Vaca Muerta Formation, encompassing the Jurassic/Cretaceous boundary (J/K boundary). Because of the increase in global ammonite provincialism during these times, only some ammonite and nannofossil species allow interregional correlations between the Andes and the Tethys regions. n Basin, the location of the Jurassic/Cretaceous In the Neuque boundary has been largely discussed among Argentinean biostratigraphers and is still a matter of debate (Leanza, 1996; Riccardi, 2008, 2015; Vennari et al., 2014; Aguirre Urreta et al., 2019). In Faunal interchangees during the Mesozoic between the Southeastern Pacific and the Tethys oceans were continuous throughout the Central Atlantic and around Australasia (Riccardi, 1991; Crame, 1999). Cosmopolitan faunas and floras would have been distributed along the Hispanic Corridor, interpreted as a narrow, embryonic Atlantic seaway that would have been open during the Pliensbachian, in consonance with the Mozambique Corridor, that was opened during the OxfordianeKimmeridgian. There are ample evidences of these connections documented from micro- and macrofossils in the Andean back-arc basins (e.g., Riccardi, 1991; Damborenea, 1993, 2002; Ballent et al., 2011; Damborenea et al., n Ba2013). Therefore, the finding of calpionellids in the Neuque sin is to be expected, but its importance lies in the fact that marks the southernmost record beyond the Tethys. 2 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 n Basin through a north-south cross section and lateral facies variations Fig. 2. (A) Chronolithostratigraphic chart for the Upper JurassiceLower Cretaceous succession in the Neuque (modified from Leanza et al., 2020); B-D) Panoramic views of outcropping sections of the Vaca Muerta Formation: (B) upper part of the formation (Spiticeras damesi to Neocomites wichmanni Zones) at Cuesta del Chihuido section, showing middle to outer ramp facies; (C) Arroyo Loncoche section, showing middle to outer ramp facies; (D) Puerta Curaco section, showing outer ramp to basin facies with subvertical dip. 3 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 n Basin, and correlation with the standard Fig. 3. (A) Summary table showing ammonite, seismic horizons and microfossil zones of the early Valanginian stage in the Neuque ammonite zones according to Aguirre Urreta (2013). Regional seismic horizons defined by Desjardins et al. (2018), and microfossil zones according to their correlation to Andean ammonite zones: (5) Nannofossil zones after Ballent et al. (2011), (6) organic-walled dinoflagellates zones after Volkheimer et al. (2011); (7) Calcareous dinoflagellate zones after Ivanova and Kietzmann (2017), (8) calpionellid zones. Gray shading indicates that no data is available. (B) Summary table showing ammonite, magnetostratigraphy, seismic and n Basin, and correlation with the standard ammonite zones. (1e2) Andean ammonite biozones, 1 according to microfossil zones of the Tithonian and Berriasian stages in the Neuque Vennari et al. (2014) and Vennari (2016), 2 according to Riccardi (2015), (3) magnetostratigraphic calibration after Iglesia Llanos et al. (2017). 4), Regional seismic horizons defined by Desjardins et al. (2018). 5e9) Distribution of microfossil zones according to their correlation to Andean ammonite zones calibrated by magnetostratigraphy: (5) Nannofossil zones after Ballent et al. (2011), (6) organic-walled dinoflagellates zones after Volkheimer et al. (2011); (7) Calcareous dinoflagellate zones after Ivanova and Kietzmann (2017) and pez Martínez et al. (2017), correlated according to Kietzmann et al. (2018a), (8) calpionellid zones after Kietzmann (2017) and Kietzmann et al. (2018b), (9) calpionellid zones after Lo this authors to ammonite zone distribution of Vennari et al. (2014). 2. Geological setting and chronostratigraphic framework recent years, several magnetostratigraphic studies have been carried out in the Vaca Muerta Formation tied to ammonite biozones, to determine the exact position of the J/K boundary (Amigo et al., 2016; Iglesia Llanos and Kietzmann, 2020; Iglesia Llanos et al., 2017; Kohan Martínez et al., 2017, 2019), which so far, had not been thoroughly supported by cosmopolitan micro- and macrofossils. Calpionellids reported by Kietzmann (2017) in sections of this formation allowed the recognition of the lowermost upper Tithonian Chitinoidella Zone, although restricted to Chitinoidellidae, and with several out-of-age chitinoidellid specimens. Another recent study regarding calpionellids of this geological unit is that pez Martínez et al. (2017), who studied few samples from a from Lo short stratigraphic interval of the Las Loicas section (Fig. 1). The main goal of this study is to establish the stratigraphic distribution of calpionellids and their TithonianeBerriasian bion Basin. For that purpose, several thin sections zones in the Neuque were analized from seven stratigraphic sections in outcrops and wells, located mostly in the northern part of the basin. Further interpretations were provided for some calpionellid species that stratigraphically extend outside of their known age in the Tethys areas. These results could hopefully allow to establish a clearer chronostratigraphic scheme for the Andes region and a better correlation with that of the Tethys, although more detailed studies regarding calpionellid assemblages from the Vaca Muerta Formation are needed. n Basin was developed as a retro-arc basin at the The Neuque Pacific margin of South America throughout Mesozoic and Cenozoic times (Fig. 1). The basin was subjected to different tectonic regimes, which exerted a first-order control in the structure and sedimentary evolution (Legarreta and Uliana, 1991, 1996). The earliest tectonic regime exerted an overall compression during the Late TriassiceEarly Jurassic, bringing about a set of narrow, isolated depocenters bounded by large strike-slip fault systems and filled with continental to marine deposits of the Precuyano Cycle (D'Elia et al., 2012, 2020; Gulisano, 1981; Gulisano et al., 1984a; Vergani et al., 1995). Deposition during the Early Jurassic to Late Cretaceous was controlled by thermal subsidence accompanied by local tectonic events, making up the continental and marine siliciclastic, carbonate and evaporitic sediments of the Cuyo, Lotena, and Mendoza Groups (Gulisano et al., 1984b; Mitchum and Uliana, 1985; Vergani et al., 1995; Zavala et al., 2020). From the Late Cretaceous to the Cenozoic, the basin was affected by a generalized compression, which resulted in the formation of an extensive fold and thrust belt (Ramos, 2010). The Andean Mountain range between 34 and 39 S can be divided in two sectors. The western sector corresponds to the main cordillera and is characterized by a complex evolution that involves periods of out-of-sequence thrusting, and pulses of relaxation of 4 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Catutos section, the sampled interval spans a part of the Tithonian. Only 4 normal and 4 reverse polarity zones were identified and assigned to the M22 to M20 Chrons. Magnetostratigraphic studies on these three sections were complemented by cyclostratigraphic analysis, resulting in a robust chronostratigraphic framework (Iglesia Llanos et al., 2017; Kietzmann et al., 2015, 2018a). In the subsurface wells, three well cores at El Trapial area, spaning the early Tithonian-early Berriasian interval were studied (Iglesia Llanos et al., 2015; Costanzo-Alvarez et al., 2019), involving 9 normal and 8 reverse polarity zones, which were correlated to the M22-M16 Chrons. Calcareous nanofossils studies were also carried out on several sections of the Vaca Muerta Formation (Bown and Concheyro, 2004; Kietzmann et al., 2011b; Scasso and Concheyro, 1999; Vennari et al., 2014, 2017). The most important events of this fossil group are: the first occurrence (FO) and last occurrence (LO) of Polycostella beckmannii Thierstein, Hexalithus noeliae Loeblich and Tappan, Polycostella senaria Thierstein, Umbria granulosa Bralower and Thierstein, Eiffellithus primus Applegate and Bergen, Eiffellithus windii Applegate y Bergen, Rhagodiscus asper (Stradner) Reinhardt, Cruciellipsis cuvillieri (Manivit) Thierstein, Nannoconus wintereri Bralower and Thierstein, Nannoconus kamptneri minor Bralower, Nannoconus steinmannii Kamptner, and Nannoconus kamptneri €nnimann. It is worth noting that none of these events could be Bro n Basin (e.g., realibly documented at a regional scale in the Neuque Vennari et al., 2017). Concerning calcareous dinoflagellate cysts, eight events were recently reported by Ivanova and Kietzmann (2017) for the lower Tithonian-lower Valanginian interval (Fig. 3), a nek, Paraincluding the FO of Committosphaera pulla (Borza) Reh stomiosphaera malmica (Borza) Nowak, Colomisphaera tenuis (Nagy) a nek, StoNowak, C. fortis Reh anek, Stomiosphaerina proxima Reh miosphaera wanneri Borza, Colomisphaera conferta Reh anek, and Carpistomiosphaera valanginiana Borza, that allowed the characterization of seven calcareous dinocyst zones, previously recognized in the Tethyan Realm. These biozones have been subsequently reported in several sections throughout the basin (Ruffo Rey et al., 2018; Kietzmann et al., 2018b), even as far as the Antarctic Peninsula (Kietzmann and Scasso, 2020), which makes this fossil group very consistent, although we are aware that further studies are mandatory on the issue. In addition, a regional seismostratigraphic framework (Fig. 3) consisting of 13 key seismic horizons has recently been established through cooperation between 15 oil companies and the University of Buenos Aires (Desjardins et al., 2018). Such horizons crosscut almost 300 km of a continuous seismic line, that was successfully extrapolated up to the surface in Puerta Curaco. Horizon ages were assigned according to the ammonites collected from different well cores. the compressive structure (Zapata and Folguera, 2005). This sector show heights of 2000 to 3000 m, and higher peaks such as the Domuyo volcano (4709 m), which is the highest mountain in the Patagonian Andes. The eastern sector corresponds to the Agrio, Chos Malal, and Malargüe fold and thrust belts (Fig. 1) characterized by a major exhumation during the Late Cretaceous, exposing n Basin. The Agrio fold and the Mesozoic deposits of the Neuque thrust belt is a thin-skinned mountain belt with an average altitude of c. 1200 m. The Chos Malal and Malargüe fold and thrust belts are thick-skinned mountain belts with an average altitude of c. 1600 m (Rojas Vera et al., 2016). These geological conditions allowed the Vaca Muerta Formation to become a prolific oil- and gas-producing resource, characterized by high organic content (3e12% of TOC) and a large thermal maturity gradient running east to west (Craddock et al., 2019; n Legarreta and Villar, 2015; Sylwan, 2014). Most of the Neuque Embayment area is in the oil window with vitrinite reflectance (Ro) between 0.6% and 1.3% (Fig. 1), namely maximum burial temperatures for maturation between approximately 60 and 150 C. Outcrops from the Malargüe fold and thrust belt also display stages of immaturity/early maturity to mid-maturity for oil at different depth ranges (Fig. 1). By contrast, outcrops from the Chos Malal and Agrio fold and thrust belts are overmatured (dry gas window stage) and were submitted to temperatures between 150 and 200 C (e.g., Capelli et al., 2018; 2021a,b; Legarreta and Villar, 2015; Sylwan, 2014). During the early Tithonianeearly Valanginian, the onset of narrow corridors carving the volcanic arc, connected the basin with the Proto-Pacific Ocean, prompted the deposition of shallow marine sequences forming the Lower Mendoza Subgroup (Legarreta and Uliana, 1996). In the Malargüe Subbasin (Mendoza Platform, Fig. 2), the Lower Mendoza Subgroup is conformed by the continental deposits of the Tordillo Formation, then by basinal to middle carbonate ramp sequences of the Vaca Muerta Formation (lower Tithonianelower Valanginian), and middle to inner ramp oysterdeposits of the Chachao Formation (lower Valanginian) (e.g., n embayMitchum and Uliana, 1985) (Fig. 2). At northern Neuque ment, sediments corresponding to a mixed siliciclastic-carbonate shelf, were deposited from the late Berriasian to the early Valanginian and assigned to the Quintuco and Vaca Muerta Formations (Gulisano et al., 1984b; Mitchum and Uliana, 1985; Kietzmann et al., 2016) (Fig. 2). n Basin, Tithonian and Berriasian intervals (Fig. 3) In the Neuque were divided, for the first time, into eight ammonite biozones by Leanza (1945, 1980) on the base of autochthonous species, with minor modifications in some subzones (e.g., Zeiss and Leanza, 2008; Vennari, 2016). Such biozonation poses a real challenge in the correlation with the Tethysian Standard biozones, bringing to various correlation schemes. Currently, two correlation schemes (Vennari et al., 2014; Riccardi, 2015) are in use, which differ in the range of some biozones, and particularly most relevant discrepancy lies arround the Jurassic/Cretaceous boundary (Fig. 3). Concerning magnetostratigraphy, three recent studies were carried out in outcrops of the Vaca Muerta Formation: Puerta Curaco (Amigo et al., 2016; Kohan Martinez et al., 2019), Arroyo Loncoche (Iglesia Llanos et al., 2017) and Los Catutos (Kohan Martinez et al., 2018), but only Puerta Curaco and Arroyo Loncoche sections involve the J/K boundary. In the Puerta Curaco, which represents the lower Tithonianelower Valanginian interval, 8 normal and 9 reverse polarity zones were preliminary identified (Amigo et al., 2016; Kohan Martinez et al., 2019), but magnetostratigraphic investigations are still in process. At the Arroyo Loncoche section, the sampled interval spans the lower Tithonianeupper Berriasian and bears 11 reverse and 10 normal polarity zones correlated with the M22 to M15 Chrons. At Los 3. Materials and methods Almost 600 thin sections made from limestone and marlstone belonging to seven sections of the Vaca Muerta Formation were studied for microfacies analysis, following standard criteria. For calcareous microfossils, we used a petrographic microscope Leica DM 750 with attached digital camera and processed the data with a software for micrometric measurements. The studied material from well logs is housed at the YPF Technical Repository, Avellaneda, Buenos Aires, Argentina under the collection code HGTC. Thin sections from outcropping stratigraphic sections are housed at the Palaeontology colleccion of the University of Buenos Aires under the code BAFC-LD. Calpionellid determination and their taxonomic follow the systematics criteria from Colom (1948), Tappan and Loeblich (1968), Remane (1964, 1971, 1978), Borza (1969) and Trejo (1976), 5 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 6 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 represented by the Virgatosphinctes andesensis to Neocomites wichmanni Zones (Kietzmann et al., 2014, 2018a, b). Calpionellid assemblages were studied through 68 thin sections. Cyclostratigraphic data determine a duration of 10.25 Ma (Kietzmann et al., 2015, 2018a, b). among others. These include: 1) lorica-wall texture, 2) lorica morphology, 3) collar morphology, and 4) lorica width/length ratio. To work out the new data that could establishing calpionellid n basin, we take into considbiostratigraphic zones in the Neuque eration all biozonation schemes synthesized by Lakova and Petrova (2013). Hence, we have favored those events that were independent of paleoenvironmental conditions, such as FO and LO, and above all, to account for their regional representativeness throughout the studied sections. 4.3. Puerta Curaco section At Puerta Curaco section (Fig. 6), with coordinates 37 220 26.1900 S, 69 560 17.2200 W, the Vaca Muerta Formation involves a rhythmic succession of c. 400 m-thick that consists of decimetric marlstone and limestone, corresponding to basinal to distal outer ramp setting. Ammonite biozones span from Virgatosphinctes andesensis Zone to the Spiticeras damesi Zone (lower Tithonianeupper Berriasian). The stratigraphic succession continues with the Quintuco Formation (c. 300 m-thick) that consists of mudstone and sandstone of prodelta facies (Kietzmann et al., 2016; Capelli et al., 2018). Ammonite species characterize the Neocomites wichmanni Zone and lower part of the Lissonia riveroi Zone, indicating the lower Valanginian (Leanza and Hugo, 1977; Mitchum and Uliana, 1985; Kietzmann et al., 2016, 2018c). In addition, 6 of the 13 key regional seismic horizons were placed within this section (Kietzmann et al., 2018c). For the microfossils, a total of 90 thin sections were studied from this section. 4. Studied sections and blocks 4.1. Arroyo Loncoche section At Arroyo Loncoche section (Fig. 4), with coordinates 35 360 00.7500 S, 69 370 32.2600 W, the Vaca Muerta Formation shows c. 280 m-thick, which constitutes one of the most studied sections in the n basin in terms of biostratigraphy (ammonites and miNeuque crofossils), polarity zones, and cyclostratigraphy. Here, the Tithonian and Berriasian succession consists of a rhythmic alternation of decametric marlstone and limestone beds representing basinal to distal middle ramp deposits (Kietzmann et al., 2008; 2011b, 2014). The lower Valanginian is conformed by oyster-dominated shallow water limestones assigned to the Chachao Formation (Legarreta and Kozlowski, 1981). Ammonite species ranges from the lower Tithonian to the upper Berriasian, represented by Virgatosphinctes andesensis to Spiticeras damesi Zones (Kietzmann et al., 2008, 2011b, 2014, 2018a, b). The top 15 m-thick interval of the section is covered by debris from the Chachao Formation and likely corresponds to the lower Valanginian Neocomites wichmanni Zone. Nannoplankton is poorly represented, although a few important bioevents were recognized (Kietzmann et al., 2011b): FO of Polycostella beckmannii, and Polycostella senaria. Calcareous dinoflagellate cyst studies reveal a relatively rich assemblage of 24 known species (Ivanova and Kietzmann, 2017), that allowed to distinguish six zones, ranging from the Carpistomiosphaera tithonica to the Colomisphaera conferta Zones (lower Tithonianelower Valanginian). Likewise, 11 poorly preserved known calpionellid species allowed the identification of the Chitinoidella and Crassicollaria Zones (Kietzmann, 2017). Magnetostratigraphic results indicate the Vaca Muerta Formation encompassed the M22r.2r to M15r Subchrons (Iglesia Llanos et al., 2017). Coupled to the paleomagnetic data, the analysis of 24 samples (Kietzmann 2017) and 60 thin sections obtained from paleomagnetic sample horizons (Fig. 4), allowed to adjust the positions of bioevents. On the other hand, cyclostratigraphic results allow to recognize 24 low-frequency eccentricity cycles that imply a duration of ~10 Ma (Kietzmann et al., 2011b, 2015; 2018b). 4.4. El Trapial block n province (c. This block is located in the northwestern Neuque 37 S, 69 W; ~900 m a.s.l), to the south of the Colorado River (Fig. 1). The cored interval of the Vaca Muerta Formation is c. 450 m-thick (between 2300 and 4000 m from the surface) and is characterized by a rhythmic alternation of marlstone and limestone. Ammonites span the Virgatosphinctes andesensis Zone to the Neocomites wichmanni Zone (Fig. 7), indicating a TithonianeEarly lez Tomassini et al., 2015). A regional Valanginian age (Gonza magnetostratigraphic scale was constructed using magnetic polarity zones isolated from three well cores at El Trapial block. Altogether, the well cores span the lower Tithonianeupper Berriasian interval and involve 9 normal and 8 reverse polarity zones correlated to the M22 to M16 Chrons (Iglesia Llanos et al., 2015). Additionally, 13 key seismic horizons are precisely located within this block (Vallejo et al., 2018). For micropaleontological analysis, 44 thin sections from cores and side well cores were studied from one well (Fig. 7). 4.5. Narambuena block This block (37 S, 68 300 W) is located to the east of El Trapial n province. Cored thickness and (Fig. 1), in northwestern Neuque stratigraphy are similar to those of El Trapial well cores. Ammonite data are not published yet, but 13 key seismic horizons are precisely located within different wells. Two hundred thin sections were analysed for micropaleontological assemblages, belonging to cores and side well cores of three different wells. Biostratigraphic results are given in Figures 8, 9 and 10. 4.2. Cuesta del Chihuido section This section (Fig. 5), with coordinates 35 44 0 49.380 S, 69 W, is located in the southern end of the Malargüe anticline, 20 km south of the previous section. Its stratigraphic succession, of 185 m-thick, is almost identical to that of the Arroyo Loncoche section (Kietzmann et al., 2014). Ammonites and cyclostratigraphic studies were performed, as well as a detailed paleomagnetic sampling, but numerous cenozoic dykes and sills have remagnetized the entire section. So, it was not possible to obtain a magnetostratigraphic scale for this section. Ammonite species indicate biozones of the lower Tithonian to lower Valanginian, 340 37.32 5. Stratigraphic distribution of the calpionellid taxa We have recognized seven species of the family Chitinoidellidae (Fig. 11), and 19 of the family Calpionellidae (Figs. 12e15). Chitinoidellids include Borziella slovenica (Borza), Chitinoidella boneti Fig. 4. Arroyo Loncoche section (lower Tithonianeupper Berriasian). From left to right: Andean ammonite zones, low-frequency eccentricity cycles, magnestostratigraphy, litholog, and location of the studied samples (data from Iglesia Llanos et al., 2017; Kietzmann et al., 2014, 2015, 2018a), distribution of identified calpionellid species, zones, and subzones. Out-of-age specimens are indicated with white circles and dotted gray lines, indicate likely reworking. 7 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 5. Cuesta del Chihuido section (lower Tithonianelower Valanginian). From left to right: Andean ammonite zones, low-frequency eccentricity cycles, litholog, and location of the studied samples (data from Kietzmann et al., 2014, 2015; 2018a), distribution of identified calpionellid species, zones, and subzones. Out-of-age specimens are indicated with white circles and dotted gray lines, indicate likely reworking. Abbreviations: slov.: slovenica, e.: elliptica, obl.: oblonga, dar.: darderi, Cts.: Calpionellites. 8 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 6. Puerta Curaco section (lower Tithonianelower Valanginian). From left to right: Andean ammonite zones, litholog, and location of the studied samples (data from Kietzmann et al., 2018c), distribution of identified calpionellid species, zones and subzones. Out-of-age specimens are indicated with white circles and dotted gray lines, indicate likely reworking. 9 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 10 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Crassicollaria is also represented by distinctive species, such as Cr. brevis Remane, Cr. colomi? Doben, Cr. intermedia Durand Delga, Cr. massutiniana (Colom), and Cr. parvula Remane (Fig. 14). Cr. brevis, Cr. intermedia, Cr. massutiniana and Cr. parvula occur within the Windhauseniceras internispinosum and Corongoceras alternans Zones (upper Tithonian), the lastest two species are more common. Cr. parvula appears with remarkably higher abundance throughout the Substeueroceras koeneni Zone, where also Cr. colomi? appears. Some Tithonian species such as Cr. brevis (Fig. 6) have been found in Berriasian levels, which suggests reworking. Other typical genera of Calpionellidae include Lorenziella Knauer and Nagy, Calpionellopsis Colom and Calpionellites Colom (Fig. 15). Genus Lorenziella, is represented by scarce Lorenziella hungarica Knauer and Nagy that appears within the Spiticeras damesi Zone (upper Berriasian). On the other hand, Calpionellopsis, often abundant, is represented by Calpionellopsis simplex (Colom) and Calpionellopsis oblonga (Cadisch). Cps. simplex appears within the Argentiniceras noduliferum Zone, and Cps. oblonga within the upper Spiticeras damesi Zone. Finally, some specimens assigned to Calpionellites darderi (Colom) were recognized within the Neocomites wichmanni Zone (lower Valanginian). Doben, Chitinoidella elongata Pop, Chitinoidella hegarati Sallouhi, Boughdiri and Cordey, Dobeniella cubensis (Furrazola-Bermúdez), a nek), and Popiella oblongata Reh Longicollaria cf. insueta (Reh akova (Fig. 11). Most of these species have been previously reported at the Arroyo Loncoche section (Kietzmann, 2017). The new data presented here help adjusting the stratigraphic distribution of the above-mentioned species. In addition, some chitinoidellid species previously described, as Dobeniella cf. pinaraensis (Kietzmann, 2017, . 4.20), were attributed to Longicollaria cf. insueta based on a new well-preserved material. The species Dobeniella cubensis and Popiella oblongata are reported here for the first time in the Neun Basin. The first chitinoidellids appear with low abundance que within the lower part of the Vaca Muerta Formation (Pseudolissoceras zitteli Zone to Aulacosphinctes proximus Zone) and are represented by L. cf. insueta and B. slovenica. The remaining species appear in the basal part of the Windhauseniceras internispinosum Zone, showing a slight increase in abundance and diversity. In the studied sections, chitinoidelids reach the Corongoceras alternans zone (upper Tithonian) and they were found in abnormal position in higher stratigraphic levels of early Berriasian age (Kietzmann, 2017). These occurrences were carefully re-analyzed in this work, concluding that chitinoidellid specimens within the upper Corongoceras alternans Zone and the lower Substeueroceras koeneni (upper Tithonian) are most likely reworked specimens, but those reaching the Berriasian levels are certainly diagenetically modified calpionellid specimens. Therefore, the latter specimens should be reassigned to the Family Calpionellidae (see section 7). With regards to the calpionellids, most of the typical Tethyan species could be identified in the studied sections, although their abundance and diversity are markedly low compared to the genera of the Tethys (Figs. 12e15). Typical calpionellid species from the Upper JurassiceLower Cretaceous transition are often well pren Basin, including representative species of served in the Neuque the genera Calpionella Lorenz, Crassicollaria Remane, and Tintinnopsella Colom. The first occurrence of calpionellids starts with the genus Tintinnopsella, represented by small variety of T. carpathica (Murgeanu and Filipescu) and T. remanei Borza. Specimens of T. carpathica specimens show a characteristic increase in size through the mid Substeueroceras koeneni Zone, suggesting an early Berriasian age. T. remanei occurs at the lowermost upper Tithonian Windhauseniceras internispinosum Zone, reaching hardly the higher part of the lower Berriasian Substeueroceras koeneni Zone (Figs. 4 and 5). It is worthy to remark that since this species is characteristic of the base of the Crassicollaria Zone, its finding in uppermost upper Tithonian (upper Crassicollaria Zone) and lower Berriasian (Calpionella Zone) levels would indicate reworked material. Typical Cretaceous species of this genus also include T. doliphormis (Colom), T. longa (Colom) and T. subacuta (Colom). Calpionella includes C. grandalpina Nagy, C. alpina Lorenz, C. elliptalpina Nagy, C. elliptica Cadisch, and C. minuta Housa (Fig. 13), which show a rather consistent stratigraphic distribution with respect to the Tethys regions. C. grandalpina occurs within the upper Tithonian Corongoceras alternans Zone. Its abundance diminishes immediately before the J/K boundary and reaching the lower Berriasian within the Substeueroceras koeneni Zone. C. alpina is found firstly in the upper Corongoceras alternans Zone and continues along the Substeueroceras koeneni Zone, where a remarkable increase in its abundance is observed. C. elliptalpina is restricted to the upper Corongoceras alternans and lower Substeueroceras koeneni Zones, and within the upper part of the latter zone, C. minuta and C. elliptica are also found. 6. Calpionellid biozones The basis of the calpionellid biostratigraphic backbone for the Tethyan Realm proposed by Allemann et al. (1971), Remane (1971), and Remane et al. (1986) has been improved over the years, and subdivisions of standard zones has provided a more refined framework (Andreini et al., 2007; Benzaggagh, 2020; Benzaggagh and Atrops, 1995; Grün and Blau, 1997; Lakova and Petrova, 2013; kova and Lakova et al., 1997, 1999; Pop, 1994a,b, 1997; Reha Michalík, 1997; Remane et al., 1986; Trejo 1980; among others). n Basin, the complete Tethyan calpionellid bioIn the Neuque zonation was not properly demonstrated yet, and therefore all the cited biozonations were considered. The following zones and subzones were recognized after a regional analysis and correlation between the studied sections (Fig. 16). 6.1. Chitinoidella Zone The base of the Chitinoidella Zone (sensu Enay and Geyssant, 1975) is marked by the FO of chitinoidellids, located in the middle part of the Pseudolissoceras zitteli Zone within the Vaca Muerta Formation. The upper boundary is marked by the FO of hyaline calpionellids in the mid-up Windhauseniceras internispinosum Zone. The zone additionally includes L. cf. insueta, B. slovenica, Ch. boneti, Ch. hegarati, Ch. elongata and D. cubensis. n Basin by The Chitinoidella Zone was recognized in the Neuque Kietzmann (2017), who has recognized two subzones. The lower subzone contains L. cf. insueta and B. slovenica, which are reported in the Dobeni Subzone of the Thetys. So far, it is remarkable to n Basin of the typical small size notice the absence in the Neuque species of the Dobeni group, L. dobeni and D. colomi, which are the most characteristic species of the Dobeni Subzone in the Tethys regions. The upper subzone contains Ch. boneti, Ch. hegarati, Ch. elongata, and L. cf. insueta. These four species are characteristic of the Boneti Subzone in the Tethys. In this study we recognized two subzones for the Chitinoidella Zone: Fig. 7. Representative well logs from the El Trapial block (lower Tithonianeupper Berriasian). From left to right: Regional seismic horizons, Andean ammonite zones identified from lez Tomassini et al., 2015; Vallejo et al., 2018), magnetostratigraphy (Iglesia Llanos et al., 2015; gray intervals ¼ Cenozoic volcanic intrusives), and well cores (data from Gonza location of the studied samples, distribution of identified calpionellid species, zones, and subzones. 11 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 12 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 2) Crassicollaria massutiniana Subzone: The subzone starts with the FO of C. grandalpina and C. alpina. The upper boundary is marked by the LO of C. elliptalpina. This subzone is equivalent to the Crassicollaria massutiniana Subzone defined by Lakova (1993), and contains, but not registered in all sections: Cr. massutiniana, Cr. intermedia, Cr. brevis, Cr. parvula, Cr. colomi, and C. elliptalpina, as well as reworked specimens of D. cubensis, B. slovenica, and Ch. boneti. This subzone corresponds to the uppermost Windhauseniceras internispinosum Zone and the lowermost Substeueroceras koeneni Zone. C. elliptalpina is restricted to the uppermost part of this subzone. The occurrence of this species in the lower Substeueroceras koeneni Zone is a n Basin. reliable regional event in the Neuque 1) Borziella slovenica Subzone: This subzone contains B. slovenica and L. cf. insueta. This interval can be correlated to the Borziella slovenica Subzone defined by Sallouhi et al. (2011) in northern Tunisia. The Subzone spans the middle part of the Pseudolissoceras zitteli Zone to the transition between Aulacosphinctes proximus and the Windhauseniceras internispinosum Zones. In contrast with the Tunisian subzone, the Slovenica Subzone in the n Basin does not contain the most representative species Neuque of the genera Longicollaria, Carpathella, Daciella and Dobeniella. n Basin, this subzone extends up to the Moreover, in the Neuque base of the Boneti Subzone, since the species D. bermudezi, D. tithonica, and D. colomi that characterizes the following Bermudezi Subzone in Tunisia, have not been found in Argentina. Therefore, the Tethyan Dobeni Subzone would be substituted in n Basin by the Slovenica Subzone. the Neuque 2) Chitinoidella boneti Subzone: It is represented by the species Ch. boneti, Ch. hegarati, Ch. elongata, L. cf. insueta, and D. cubensis. Its starts at the FO of Ch. boneti and its upper boundary corresponds to the FO of the calpionellids with hyaline lorica, including T. remanei. This subzone corresponds to the Chitinoidella boneti Subzone in the Tehtys regions (Borza, 1984; Borza and Michalík, 1986; Benzaggagh and Atrops, 1995). The Boneti Subzone corresponds approximately to the lower half of the Windhauseniceras internispinosum Zone. 6.3. Calpionella Zone The base of the Calpionella Standard Zone (sensu Allemann et al., 1971) is marked by the acme of C. alpina, which is particularly observable in the Loncoche section and in well 3 from the Narambuena block. This event is situated at the lower part of the Substeueroceras koeneni Zone in Arroyo Loncoche, whereas in the well 3, this limit is found 20 m above the T5 seismic horizon. In other studied sections, the lower boundary of the Calpionella Zone is marked by the LO of C. elliptalpina located just below the acme of C. alpina and is an event that have a regional consistency in the n Basin. Its upper boundary is defined by the FO of Cps. Neuque simplex, within the Argentiniceras noduliferum Zone. The Calpionella zone contains T. carpathica, T. doliformis, C. grandalpina, C. alpina, C. minuta, C. elliptica, Cr. parvula, and reworked Cr. brevis, and Cr. colomi?. The zone is characterized by the higher abundance of Cr. parvula and isometric shaped C. alpina and the disappearance of Cr. massutiniana, Cr. intermedia, and C. elliptalpina. In the Tethys, the Calpionella Zone is divided into three or four subzones (e.g., Lakova and Petrova, 2013, and references therein), although in the Neuquen basin we could recognize a single consistent event that divides the zone in two subzones: 6.2. Crassicollaria Zone The base of this zone corresponds to the FO of Calpionellidae, represented by the almost co-occurrence of T. carpathica and T. remanei within the upper half of the Windhauseniceras internispinosum Zone. In the Tethys, the Crassicollaria Zone extends up to the acme of the small spherical forms of C. alpina. In the Andes, the situation is somehow different, for even though C. alpina becomes more abundant along the Substeueroceras koeneni Zone. The acme of the spherical forms of this species does not seem to be definitely documented all over the basin. Despite that, the upper boundary of the zone can be situated at the LO of C. elliptalpina, which is an event that is consistent at a regional scale, and that coincides with the extinction of the most typical Tithonian species of the genus Crassicollaria (e.g., Benzaggagh and Atrops, 1995; Benzaggagh et al., 2012; Lakova and Petova, 2013; Kowal-Kasprzyk and Reh akov a, 2019). Therefore, the zone can be correlated to the Crassicollaria Standard Zone as defined by Allemann et al. (1971). Its specific assemblage is composed of T. carpathica, T. remanei, C. grandalpina, C. alpina, C. elliptalpina, Cr. massutiniana, Cr. brevis, and Cr. parvula, and at its base contains a few species of chitinoidellids, including Ch. boneti, Ch. elongata, Ch. hegarati, D. cubensis, and P. oblongata. In the Tethys, this zone is divided in two or three subzones. In n Basin only two subzones can be identified, following the Neuque the division criteria from Lakova and Petrova (2013), which are from base to top: 1) Calpionella alpina Subzone: Its lower boundary is marked by the acme of C. alpina and/or the LO of C. elliptalpina, whereas its upper boundary is located by Pop (1974) at the FO of C. elliptica. The Alpina Subzone was characterized within most part of the Substeueroceras koeneni Zone, where C. alpina and Cr. parvula are dominant. The subzone involves the latter species' acme, the FO of C. minuta and contains T. carpathica, and T. doliformis. 2) Calpionella elliptica Subzone: Its lower boundary is marked by the FO of the index species; its upper boundary is located by Pop (1974) at the FO of Cps. simplex. The Elliptica Subzone ranges from the upper part of the Substeueroceras koeneni Zone to the lower part of the Argentiniceras noduliferum Zone. Within the subzone, we noticed a decrease in the abundance and diversity of calpionellids. It also contains T. carpathica. 6.4. Calpionellopsis Zone 1) Tintinnopsella remanei Subzone: Its lower boundary is marked by the first occurrence of T. remanei and T. carpathica. The upper boundary is marked by the FO of C. grandalpina. Therefore, this subzone corresponds to the Tintinnopsella remanei Subzone defined by Remane et al. (1986). Within this subzone we occasionally find Cr. intermedia, Cr. massutiniana, and Ch. boneti. The subzone corresponds to the upper Windhauseniceras internispinosum Zone. The base of the Calpionellopsis Standard Zone (sensu Allemann et al., 1971) is marked by the FO of Cps. simplex, whereas its upn per boundary has not been accurately determined in the Neuque Basin. The zone spans the Spiticeras damesi Zone and the lower part of the Neocomites wichmanni Zone. It comprises Cps. simplex, Cps. oblonga, L. hungarica, T. carpathica, T. longa, T. subacuta, T. doliphormis, C. alpina, C. minuta, and C. elliptica. In the Neuquen Fig. 8. Well log number 1 from the Narambuena block (lower Tithonianelower Valanginian). From left to right: Regional seismic horizons, location of the studied samples, and distribution of identified calpionellid species, zones, and subzones. Abbreviations: rem.: remanei, Cts.: Calpionellites. 13 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 basin, based on the occurrence of a consistent event within this zone, we divided the Calpionellopsis Zone into two subzones. 1) Calpionellopsis simplex Subzone: The lower boundary of the subzone (sensu Remane et al., 1986) is marked by the FO of its index species, and the upper boundary by the FO of Cps. oblonga. The Subzone spans the upper Argentiniceras noduliferum Zone and the most part of the Spiticeras damesi Zone. It contains T. carpathica, T. longa, T. subacuta, C. alpina, C. minuta, C. elliptica (only at the basal part of the subzone), and L. hungarica. 2) Calpionellopsis oblonga Subzone: Its lower boundary is defined by the FO of its index species; the upper boundary is defined by the FO of Cts. darderi (Remane et al., 1986). The subzone spans the uppermost part of the Spiticeras damesi Zone to the lowermost part of the Neocomites wichmanni Zone. It contains Cps. simplex, L. hungarica, T. carpathica, T. longa, and T. subacuta. 6.5. Calpionelllites Zone The base of the Calpionellites Standard Zone (sensu Allemann et al., 1971) is marked by the FO of Cts. darderi; the upper boundn Basin. The ary has not been accurately determined in the Neuque zone was recognized so far in the upper part of the Neocomites wichmanni Zone. It also contains L. hungarica, and T. carpathica. This interval can be assigned to the Darderi Subzone. 7. Remarks on the stratigraphic range and identification of certain chitinoidellid and calpionellid specimens previously n Basin reported from the Neuque In previous papers by the authors (Kietzmann, 2017; Kietzmann et al., 2011a), several species of chitinoidellids were described from the Arroyo Loncoche and Cara Cura sections. In these two sections, typical species of the Chitinoidella Zone (lowermost upper Tithonian) were reported within younger stratigraphic levels, up to the lower Berriasian. This anomalous stratigraphic distribution of this n Basin (Kietzmann, fossil group, previously reported in the Neuque 2017), could be partly explained by submarine erosion and n Basin reworking from older stratigraphic levels of the Neuque margin, where the interval comprising the upper Windhauseniceras internispinosum Zone to the Argentiniceras noduliferum Zone is characterized by pronounced forced regressions (Mitchum and lez et al., 2018). This geological phenomenon Uliana, 1985; Gonza would satisfactorily explain the presence of out-of-age chitinoidellid species within a limited stratigraphic interval since there is no evidence of important hiatuses or pronounced erosion. For example, despite the missing taphonomic evidence supporting reworking of out-of-age species, the presence of some specimens of B. slovenica, Ch. boneti, Ch. hegarati and D. cubensis in the Massutiniana Subzone, and those of T. remanei in the Alpina Subzone, in Arroyo Loncoche and Cuesta del Chihuido sections (Figs. 4 and 5) can be explained by this process. In fact, these two sections represent the most proximal facies corresponding to outer to middle ramp setting (Kietzmann et al., 2014, 2016) among the seven studied sections, and within these deposits, a clear increase of out-of-age chitinoidellid specimens is observed. While in the Puerta Cuaraco section and the El Trapial and Narambuena blocks the facies consists of basinal to outer ramp deposits and shows only a few out-of-age species. However, although erosion and reworking Fig. 9. Well log number 2 from the Narambuena block (lower Tithonianelowermost Valanginian). From left to right: Regional seismic horizons, location of the studied samples, distribution of identified calpionellid species, zones, and subzones. Abbreviations: dar.: darderi, Cts.: Calpionellites. 14 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 10. Well log 3 from the Narambuena block (lower Tithonianelowermost Valanginian). From left to right: Regional seismic horizons, location of the studied samples, distribution of identified calpionellid species, zones, and subzones. Abbreviations: dar.: darderi, Cs.: Calpionellites. 15 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 11. Chitinoidellids from the Vaca Muerta Formation. (AeF) Borziella slovenica (Borza): (A) lower Tithonian, middle part of the Pseudolissoceras zitteli Zone, Arroyo Loncoche section, sample AL26 (BAFC-LD21), (B) lower Tithonian, middle part of the Pseudolissoceras zitteli Zone, Puerta Curaco section, sample PC10 (BAFC-LD38), (CeF) lower Tithonian, Aulacosphinctes proximus Zone, Cuesta del Chihuido section, samples CH8 (BAFC-LD49) and CH10 (BAFC-LD50), (CeD) lowermost upper Tithonian Windhauseniceras internispinosum Zone, Cuesta del Chiuido section, sample CH13 (BAFC-LD51), (F) upper Tithonian, Corongoceras alternas Zone, Arroyo Loncoche section, sample AL35 (BAFC-LD24); (GeL) Chitinoidella boneti Doben: (G) Lowermost upper Tithonian, lower part of the Windhauseniceras internispinosum Zone, Arroyo Loncoche section, sample AL 30 (BAFC-LD22), (HeJ) upper Tithonian, Corongoceras alternas Zone, Arroyo Loncoche section, samples AL35 (BAFC-LD24) and AL38 (BAFC-LD26), (K) upper Tithonian, Corongoceras alternans Zone, Cuesta del Chihuido section, sample CH25 (BAFC-LD53), (L) possible reworked specimen from the lower Berriasian, Substeueroceras koeneni Zone, Arroyo Loncoche section, sample A45 (BAFCLD29); (MeO) Chitinoidella elongata Pop: lowermost upper Tithonian Windhauseniceras internispinosum Zone, (MeN) Puerta Curaco section, sample PC18 (BAFC-LD40), (O) Arroyo Loncoche section, sample L74 (BAFC-LD36); (PeR) Chitinoidella hegarati Sallouhi, Boughdiri and Cordey: (P) uppermost upper Tithonian, Windhauseniceras internispinosum Zone, Cuesta del Chihuido section, sample CH13 (BAFC-LD51), (Q) lower Tithonian, uppermost part of the Windhauseniceras internispinosum Zone, Arroyo loncoche section, sample AL30 (BAFC-LD22), (R) oblique section, upper Tithonian, Corongoceras alternans Zone, Arroyo Loncoche section, sample AL34 (BAFC-LD23); (S) Dobeniella cubensis (Furrazola-Bermúdez): possible reworked specimen from the uppermost upper Tithonian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL38 (BAFC-LD26). (TeV) Longocollaria cf. insueta a nek): (T) lower Tithonian, Pseudolissoceras zitteli Zone, Puerta Curaco section, sample PC10 (BAFC-LD38), (U) lower Tithonian, uppermost part of the Pseudolissoceras zitteli (Reh Zone, Puerta Curaco section, sample PC12 (BAFC-LD39), (V) lowermost lower Tithonian, Windhauseniceras internispinosum Zone, Puerta Curaco section, sample PC20 (BAFC-LD41), : (W) lowermost lower Tithonian, Aulacosphunctes proximus Zone, Arroyo loncoche section, sample AL30 (BAFC-LD22), (X) lowermost lower (WeX) Popiella oblongata Rehakova Tithonian, Windhauseniceras internispinosum Zone, Cuesta del Chihuido section, sample CH24 (BAFC-LD52). Scale bar: 50 mm. After a revision of the material studied previously by Kietzmann (2017), and the examination of the new thin sections from that interval, we have demonstrated that several specimens with dark lorica, given the impression of chitinoidellids, are rather calpionellids with loricas that are diagenetically modified. Organic-rich marine deposits, like that of the Vaca Muerta can explain the presence of some out-of-age specimens, these processes can hardly explain clarely the presence of chitinoidellids within the uppermost lower Berriasian levels. The recognized hiatuses within the Vaca Muerta Formation involve no more than 400e800 ka (Kietzmann et al., 2018a). Therefore, it cannot explain reworking of species that are 5e7 Ma older. 16 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 12. Calpionellids from the Vaca Muerta Formation (Genus Tintinnopsella Colom): (AeF) Tintinnopsella carpathica (Murgeanu and Filipescu): (A) upper Tithonian Windhauseniceras internispinosum Zone, Puerta Curaco section, sample PC20 (BAFC-LD41), (B) lower Berriasian Substeueroceras koeneni Zone, Puerta Curaco section, sample PC27 (BAFCLD42), (C) lower Berriasian, well 2 of the Narambuena block, HGTC15113 - 38, (D) deformed specimen from the lower Berriasian Substeueroceras koeneni Zone, El Trapial block, HGTC13038 - 35, (EeF) upper Berriasian, well 3 of the Narambuena block, HGTC15116 - 32; (GeI) Tintinnopsella remanei Borza: (G) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 7, (H) upper Tithonian, well 3 of the Narambuena block, HGTC15008 - 9, (I) upper Tithonian, well 3 of the Narambuena block, HGTC1511 - 9; (J-L) Tintinnopsella doliformis (Colom): lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL49 (BAFC-LD32) and AL50 (BAFC-LD33); (MeR) Tintinnopsella longa (Colom): (MeN) upper Berriasian, well 1 of the Narambuena block, HGTC15008 - 39 and 40, (O) upper Berriasian, well 3 of the Narambuena block, HGTC15116 - 31, (oeq) upper Berriasian Spiticeras damesi Zone, Cuesta del Chihuido section, sample CH56 (BAFC-LD57), (R) upper Berriasian, El Trapial block, HGTC13038 - 39; (SeX) Tintinnopsella subacuta (Colom): (S) lower Berriasian Substeueroceras koeneni Zone, Cuesta del Chihuido section, sample CH53 (BAFC-LD56), (T) lower Berriasian, well 1 of the Narambuena block, HGTC15008 - 37, (U) upper Berriasian, well 3 of the Narambuena block, HGTC15116 - 31, (V) upper Berriasian Spiticeras damesi Zone, Puerta Curaco section, sample PC45 (BAFC-LD47), (W) upper Berriasian Spiticeras damesi Zone, El Trapial block, HGTC13038 - 40, (X) upper Berriasian Argentiniceras noduliferum Zone, Cuesta del Chihuido section, sample CH57 (BAFC-LD58). Scale bar: 50 mm. et al., 2018, 2021a,b; Catalano et al., 2018; Fortunatti et al., 2018; Lanz et al., 2021). The studied stratigraphic sections of the Vaca Muerta Formation show high organic matter thermal maturity, ranging between the oil/wet-gas window and the gas window (Fig. 1), and isotopic signatures indicating that the Vaca Muerta Formation reached temperatures of 150e195 C (Catalano et al., Formation, are subjected to a variety of early and late diagenetic processes affecting mineral compositions, organic matter transformation and authigenic mineral precipitations. Previous petrographic and geochemical studies indicate that marlstone and limestone reached deep burial conditions and have been affected by several stages of diagenesis during their burial history (Capelli 17 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 8. Correlations between calpionellids, ammonite, and polarity zones 2018; Weger et al., 2019; Lanz et al., 2021). During burial diagenesis, compaction and thermal maturation of organic matter produces acidic poral water promoting the dissolution of calcium carbonate. Under these conditions, fine-grained limestone tends to recrystallize forming microspar mosaics, and a series of mineral and textural transformations occur in the particles contained within the lime mud. In the studied samples, three main neomorphic processes are recognized that distort the original composition and textures of the hyaline loricas: micritization, chloritization, and pyritization. Micritization in the deep burial stage occurs by partial dissolution of skeletal grains associated with recrystallization and crystal diminution, but it can also occur without a dissolution stage, associated with decomposition of organic matter producing the simultaneous growth of microcrystalline carbonate or a micrite residue (Purdy, 1968; Flügel, 2004). The observation of new material from the Vaca Muerta Formation allowed us to recognize this type of process in lower Berriasian micritic loricas. When the dissolution of the hyaline wall is complete, and the micritic residue has been preserved, it becomes difficult to establish the original texture of the wall. Nevertheless, in many specimes, relics of the original hyaline lorica are still recognized (Fig. 17aeC) allowing to identify this process. Another criterion is the thickness of the wall, which in specimens formed by the micritic residue turns out to be 30e60% less thick than expected (Fig. 17A,B). Similarly, replacement processes are common within the Vaca Muerta Formation. Autigenic chlorite shows pervasive distribution within the lime mud matrix at certain stratigraphic intervals. These chlorites are Mg-rich mineral species that are consistent with burial paleotemperatures and organic maturation of the Vaca Muerta Formation and have been interpreted as the neoformation of clays that were formed during early diagenesis from the abundant volcanic glass contained in the fine-grained matrix (Capelli et al., 2021b). Fully or partially chloritized calpionellid specimens have been observed in the studied samples (Fig. 17D,E). These specimens are easily recognizable when the micritic matrix is recrystallized to granular calcite, but they can be easily confused with microgranular calcite in dark colored samples, rich in organic matter. Autigenic pyrite also shows pervasive distribution within the lime mud matrix, particularly in transgressive system tracts. It occurs as framboidal aggregates and as cubic crystals depending on the time of formation during diagenesis (Kietzmann et al., 2020). As with chlorite replacements, pyrite replacements are easy to identify when the matrix is recrystallized (Fig. 17F), but they can become difficult in very dark samples, with high organic matter and disseminated pyrite. The mentioned diagenetic modifications have led to misidentification of some species and represent a real problem that must be carefully evaluated. Concerning to the species mentioned by n Basin, the Kietzmann (2017) for the Berriasian of the Neuque presence of Ch. boneti, Ch. hegarati, Ch. elongata, B. slovenica, and C. rumanica should be discarded, because their original loricas are diagenetically modified, and these species should be assigned to species of genera Tintinnopsella, Lorenziella and Calpionella. On the other hand, specimens assigned to B. slovenica are too large for this species and must be regarded as oblique sections of Tintinnopsella. Lastly, the specimens reported as Dobeniella cf. pinnaraensis (Kietzmann, 2017, . 4.19) from the base of the Vaca Muerta Formation (middle part of the V. andesensis Zone) are of doubtful assignment and could be diagenetic modifications of other grains showing by chance a form close to that of chitinoidellids, associated with the accumulation of autigenic minerals between the intercrystalline spaces of pseudosparite crystals. Therefore, these specimens cannot be considered until new well-preserved specimens will be found. This work presents a comprehensive calpionellid biozonation n Basin in the Southern Andes (Fig. 18), based on the for the Neuque systematic sampling of several sections and regional correlations, focused to provide more reliable correlations with the biozones of the Tethyan Realm. Particularly, calpionellids have proved to be very helpful and are consistent with other stratigraphic frameworks used over the last years for the Vaca Muerta Formation (Iglesia Llanos et al., 2017; Kietzmann et al., 2015, 2018a,b; Riccardi 2008, 2015). n Basin spans the middle The Chitinoidella Zone in the Neuque part of the Pseudolissoceras zitteli Zone to the lower part of the Windhauseniceras internispinosum Zone (. 3, 19). From ammonite biostratigraphy, the Pseudolissoceras zitteli Zone is correlable to the Semiforme and/or Fallauxi Standard Zones (Leanza, 1996; Riccardi, 2008, 2015; Vennari 2016). This zone was also correlated to the uppermost M22n and M21r Subchrons by Iglesia Llanos et al. (2017) and Kohan Martínez et al. (2018). In addition, the base of the n Basin almost coincides with the Slovenica Subzone in the Neuque FO of Polycostella beckmanni, placed within the M21r Subchron at Arroyo Loncoche, and the FO of the dinoflagellate cysts Colomisphaera tenuis (Ruffo Rey et al., 2018). The Boneti Subzone coincides with the presence of the ammonite Simplisphinctes neuquensis within the Windhauseniceras internispinosum Zone (Zeiss and Leanza, 2008), a distinctive marker of the lower Microcanthum riz, 1978; Benzaggagh and Atrops., Zone in the western Tethys (Olo 1997; Zeiss and Leanza, 2008; Riccardi, 2015). The Chitinoidella Zone in the Andes is also characterized by abundant ossicles of saccocomid crinoids (Kietzmann and Palma 2009) and involves the FO of Colomisphaera fortis (Ruffo Rey et al., 2018), which occur within the upper M20r (lower Microcanthum Zone) in the Tethys (Lukeneder et al., 2010). The biggest difference with the Tethyan regions is at the base of the zone, which is located within the mid M21n Subchron, corresponding to the upper Fallauxi ammonite Standard Zone (Benzaggagh and Atrops, 1995; Michalík et al., 2009; et al., 2019; Sallouhi et al., 2011; Lakova et al., 2017; Svobodova Wimbledon et al., 2020). However, the boundary between the Dobeni and Boneti Subzones is placed within the uppermost M21r Subchron, corresponding to the uppermost Ponti ammonite Standard Zone (Benzaggagh and Atrops, 1995; Sallouhi et al., 2011; Lakova et al., 2017) in both regions. The following zone corresponds to the Crassicollaria Zone, since the Preatintinnopsella andrusovi Zone has not be recognized yet in the Andes. The Crassicollaria Zone spans the middle part of the Windhauseniceras internispinosum to the lower part of the Substeueroceras koeneni Zones, considered to be correlatable with the upper Microcanthum to lower Jacobi Zones, equivalent to the upper M20n to mid M19n Subchrons (Iglesia Llanos et al., 2017; Iglesia Llanos and Kietzmann 2020). This ranges and calpionellid assemblage of the Crassicollaria Zone in the Andes, are similar to that reported for this zone in the Tethys (Grabowski et al., 2010a,b; et al., Lakova et al., 2017; Michalík et al., 2009, 2016; Svobodova 2019; Wimbledon et al., 2020). In addition, in the upper part of the Corongoceras alternans Zone (equivalent, in this paper, to the upper Massutiniana Subzone), Vennari et al. (2017) recorded the FO of the nannofossil Hexalithus noeliae. Also, the latest isolated Saccocoma ossicles (Kietzmann and Palma, 2009) were reported in this subzone (Fig. 18). pezAt Las Loicas section of the Vaca Muerta Formation, Lo Martínez et al. (2017) reported the assemblage of C. alpina, Cr. parvula, Cr. colomi, Cr. massutiniana, Cr. brevis, T. remanei, and T. carpathica in the uppermost Substeueroceras koeneni Zone, which interpreted as the Colomi Subzone (upper Crassicollaria Zone). The 18 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 13. Calpionellids from the Vaca Muerta Formation (Genus Calpionella Lorenz): (AeF) Calpionella grandalpina Nagy: (p) upper Tithonian Corongoceras alternans Zone, Arroyo Loncoche section, sample AL36 (BAFC-LD25), (BeC) Possible reworked specimens from the lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL50 (BAFC-LD33), (DeE) upper Tithonian, well 2 of the Narambuena block, HGTC15113 - 24 and 25; (GeL) Calpionella alpina Lorenz: (G) upper Tithonian Corongoceras alternans Zone, Cuesta del Chihuido section, sample CH34 (BAFC-LD54), (h) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 13, (I) Tithonian/Berriasian boundary, well 3 of the Narambuena block, HGTC15116 - 17, (J) Tithonian/Berriasian boundary, well 2 of the Narambuena block, HGTC15113 - 27, (k) upper Berriasian Spiticeras damesi Zone, Puerta Curaco section, sample PC45 (BAFC-LD47), (K) lower Berriasian Substeueroceras koeneni Zone, well 1 of El Trapial Block, HGTC13038 - 33; (MeR) Calpionella elliptalpina Nagy: (M) upper Tithonian Corongoceras alternans Zone, Arroyo Loncoche section, sample AL38 (BAFC-LD26), (N) upper Tithonian Corongoceras alternans Zone, Cuesta del Chihuido section, sample CH24 (BAFC-LD52), (O) upper Tithonian Substeueroceras koeneni Zone, Cuesta del Chihuido section, sample CH36 (BAFC-LD55), (P) Tithonian/Berriasian boundary, Substeueroceras koeneni Zone, Puerta Curaco section, sample PC27 (BAFC-LD42), (Q) Tithonian/Berriasian boundary, Substeueroceras koeneni Zone, well 3 of El Trapial Block, HGTC13038 - 15, (R) upper Tithonian, well 2 of the Narambuena block, HGTC15113 - 25; s-x) Calpionella elliptica Cadisch: (SeT) lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL50 (BAFC-LD33), (UeV) lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL51 (BAFC-LD34), (W) lower Berriasian Substeueroceras koeneni Zone, Puerta Curaco section, sample PC45 (BAFC-LD47), (X) lower Berriasian, well 1 of the Narambuena block, HGTC15008 - 24; y-d’) Calpionella minuta Housa: (YeZ) lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL47 (BAFC-LD30) and AL48 (BAFC-LD31), (A’) lower Berriasian, well 1 of the Narambuena block, HGTC15008 - 34, (B’) lower Berriasian Substeueroceras koeneni Zone, Puerta Curaco section, sample PC44 (BAFC-LD46), (C’) lower Valanginian Neocomites wichmanni Zone, Puerta Curaco section, sample PC60 (BAFC-LD48); (D’)) recrystallized specimen from the upper Berriasian Spiticeras damesi Zone, Puerta Curaco section, sample PC44 (BAFC-LD36). Scale bar: 50 mm. 19 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 14. Calpionellids from the Vaca Muerta Formation (Genus Crassicollaria Remane): (AeC) Crassicollaria brevis Remane: (AeB) upper Tithonian, well 3 of the Narambuena block, HGTC15116 - 13, (C) possible reworked specimen from the upper Berriasian Spiticeras damesi Zone, Puerta Curaco section, sample PC39 (BAFC-LD44); (DeF) Crassicollaria intermedia Durand-Delga: (D) upper Tithonian Corongoceras alternans Zone, El Trapial bloc, HGTC13038 - 27, (EeF) upper Tithonian, well 3 of the Narambuena block, HGTC15116 - 13; (GeL) Crassicollaria colomi? Doben: (GeI) lower Berriasian, well 1 of the Narambuena block, sample 20; (J) lower Berriasian, well 1 of the Narambuena block, HGTC15008 - 35, (K) lower Berriasian Substeueroceras koeneni Zone, Cuesta del Chihuido section, sample CH47 (BAFC-LD60), (L) lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL52 (BAFC-LD35); (MeR) Crassicollaria massutiniana (Colom): (M) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 14, (N) upper Tithonian, well 2 of the Narambuena block, HGTC15113 - 18, (O) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 15, (P) possible reworked specimen from the lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL50 (BAFC-LD33), (Q) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 14; (R) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 8; (SeX) Crassicollaria parvula Remane: (S) lower Berriasian, well 1 of the Narambuena block, HGTC15008 - 18, (TeU) lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL42 (BAFC-LD27), (W) lower Berriasian Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL43 (BAFCLD28), (X) lower Berriasian, well 1 of the Narambuena block, HGTC15008 - 21, (W) upper Tithonian, well 1 of the Narambuena block, HGTC15008 - 13; Scale bar: 50 mm. The following Calpionella Zone spans the lower Substeueroceras koenenielower Argentiniceras noduliferum Zones, which correponds to the mid M19n.2n to M16r Subchrons (Iglesia Llanos et al., 2017; Iglesia Llanos and Kietzmann, 2020), and is therefore correlatable with the lower Jacobi and Occitanica ammonite Standard Zones, as it occurs in the Tethys region (Elbra et al., 2018; Grabowski et al., 2010ab, 2016; Lakova et al., 2017; Michalík et al., 2009, 2016; et al., 2019; Wimbledon et al., 2020). These results Svobodova would indicate that only Alpina and Elliptica Subzones are assignment of this zone is controversial because it has been based on a few specimens and questionable identification (Kietzmann and Iglesia Llanos. 2018). For instance, specimens assigned by pez-Martínez et al. (2017) to the illustrated specimen of Cr. Lo massutiniana is most likely Cr. parvula, and the illustrated specimen of T. remanei could be an oblique section of T. carpathica. Therefore, it would be important to study a larger number of samples from Las Loicas section, since the association of Cr. Parvula, T. carpathica and C. alpina could be indicating the Calpionella Zone. 20 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 15. Calpionellids from the Vaca Muerta Formation (Genera Lorenziella Knauer and Nagy, Calpionellopsis Colom, and Calpionellites Colom): (AeF) Lorenziella hungarica Knauer and Nagy: (A) uppermost lower Berriasian, Argentiniceras noduliferum Zone, Arroyo Loncoche section, sample L190 (BAFC-LD37), (B) upper Berriasian, Spiticeras damesi Zone, Cuesta del Chihuido section, sample CH57 (BAFC-LD58), (CeD) upper Berriasian, well 1 of the Narambuena block, HGTC15008 - 35, (E) lower Valanginian, well 2 of the Narambuena block, HGTC15113 - 50, (F) lower Valanginian, Neocomites wichmanni Zone, Cuesta del Chihuido section, sample CH68 (BAFC-LD59); (GeL) Calpionellopsis simplex (Colom): (G) upper Berriasian, uppermost Argentiniceras noduliferum Zone, Puerta Curaco section, sample PC36 (BAFC-LD43), (HeI) upper Berriasian Spiticeras damesi Zone, Puerta Curaco section, sample PC42 (BAFC-LD45), (JeK) upper Berriasian Spiticeras damesi Zone, El Trapial block, HGTC13038 - 39, (L) upper Berriasian, well 2 of th Narambuena block, HGTC15113 - 44; (MeR) Calpionellopsis oblonga (Cadisch): (M) upper Berriasian, well 2 of the Narambuena block, HGTC15113 - 47, (N) upper Berriasian, well 3 of the Narambuena block, HGTC15116 33, (O) upper Berriasian, well 3 of the Narambuena block, HGTC15116 - 35, (P) lower Valanginian, well 2 of the Narambuena block, HGTC15113 - 49, (Q) lower Valanginian, well 1 of the Narambuena block, HGTC15008 - 48. (R) deformed specimen from the lower Valanginian, well 3 of the Narambuena block, HGTC15116 - 39; (SeX) Calpionellites darderi (Colom): (S) lower Valanginian, well 3 of the Narambuena block, HGTC15116 - 40, (TeU) lower Valanginian Neocomites wichmanni Zone, Cuesta del Chihuido section, sample CH68 (BAFCLD59), (V) lower Valanginian, well 3 of the Narambuena block, HGTC15116 - 39, (W) lower Valanginian, well 2 of the Narambuena block, HGTC15113 54, (X) lower Valanginian, well 2 of th Narambuena block, HGTC15113 - 55. Scale bar: 50 mm. 21 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 22 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 Fig. 17. Selected examples of diagenetically altered calpionellid specimens: (A) Partially micritized specimen of Lorenziella from the uppermost lower Berriasian (lower Argentiniceras noduliferum Zone, Arroyo Loncoche section, sample L190 - BAFC-LD37) showing a micritic residue (black arrow) and a partially recrystallized hyaline wall (white arrow); (B) Micritized specimen of Tintinnopsella carpathica from the uppermost lower Berriasian (lower Argentiniceras noduliferum Zone, Arroyo Loncoche section, sample L190 - BAFC-LD37) showing a thin wall corresponding to the micritic residue (black arrow), and relicts of the hyaline wall (white arrow); (C) Micritized specimen of Calpionella alpina from the lower Berriasian Substeueroceras koeneni Zone (Arroyo Loncoche section, sample AL42 - BAFC-LD27) showing a thin wall corresponding to the micritic residue (black arrow), and relicts of the hyaline wall (white arrow); (DeE) Chloritized specimen of Tintinnopsella carpathica from the lower Berriasian (Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL45 - BAFC-LD29); (F) Partially pyritized specimen of Tintinnopsella carpathica from the lower Berriasian (Substeueroceras koeneni Zone, Arroyo Loncoche section, sample AL50 BAFC-LD33) showing the hyaline wall (white arrow). et al., 2017; Wimbledon et al., 2020). Also, it is possible that some of pez Martinez et al. (2017) the calpionellid species reported by Lo would be reworked. The stratigraphic section of the Vaca Muerta Formation studied by these authors at Las Loicas, is made up by turbiditic distal outer ramp to basinal facies, yielding characteristic sedimentary textures such as sand-sized intraclastic packstonegrainstone, and intraclastic marlstones (Kietzmann et al., 2020, 2021). These textures indicate that not all specimens would necessarily be accumulated directly by fall-out from the water column in this area. Such reworking processes may also have affected the distribution of nannofossils, such as N. wintereri, N. kamptneri minor and N. steinmannii minor, that were found in the low Argentiniceras noduliferum Zone (transition between the Elliptica Subzone and the Simplex Subzone). In fact, N. kamptneri minor and N. steinmannii minor were also reported in such a high represented in the studied sections, since the Remaniella Subzone has not been characterized. The FO Calpionella elliptica occurs in the upper part of M17r Subchron, so it is possible that this event occurs n Basin. in a further down stratigraphic interval in the Neuque However, as noted by Lakova et al. (2017), the FO of Calpionella elliptica has been reported throughout the M17r by different authors. Among other evidence, Vennari et al. (2014, 2017) reported the FO of N. wintereri, N. kamptneri minor and N. steinmannii minor within the low Argentiniceras noduliferum Zone. These three events occur within the M19r and M18r Subchrons (Lakova et al., 2017; Wimbledon et al., 2020). However, Vennari et al. (2017) reported the FO of N. kamptneri minor and N. steinmannii steinmannii within the lowemid Substeueroceras koeneni Zone, events that occurs within the uppermost M19n to lowermost M17r Subchrons (Lakova Fig. 16. Correlation of studied sections. Blue and green dotted lines show the correlation between ammonite zone boundaries, solid lines indicate the correlation of seismic horizons. Calpionellid standard zones and seismic guide horizons show good consistency. In logs of some wells of the Narambuena block some of the Calpionella/Calpionellopsis boundary zones is not well defined, as observed from the crossing of this boundary and seismic guide horizons. Ammonite zones key: Va: Virgatosphinctes andesensis, Pz: Pseudolissoceras zitteli, Ap: Aulacosphinctes proximus, Wi: Windhauseniceras internispinosum, Ca: Corongoceras alternans, Sk: Substeueroceras koeneni, An: Argentiniceras noduliferum, Sd: Spiticeras damesi, Nw: Neocomites wichmanni. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 23 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 n basin and correlation with previous data. Magnetostratigraphy after Iglesia Llanos et al. (2017) and Kohan Martínez Fig. 18. Biostratigraphy based on calpionellids for the Neuque et al. (2017), cyclostratigraphy based on Kietzmann et al. (2018a,b). Other markers are included in the right column. Calcareous dinoglagellate cysts in black, nannofossils in blue, and ammonites in green. Gray shaded intervals indicate uncertain in position of events from other authors. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) Calpionellites darderi occur in the mid Neocomites wichmanni Zone of early Valanginian age. In the sections studied, only the Simplex and Oblonga Subzones have been characterized, with the lower boundary of the Oblonga Subzone is located close to the mid part of the M16n Subchron. The age of this subchron is in accordance with that reported in the Tethys, where the base of the Oblonga Subzone is located within the loweremiddle M16n Subchron (Grabowski et al., 2016, 2018). Other important bioevents recognized in the Calpionellopsis Zone (Fig. 18) are the presence of Stomiosphaera wanneri within the upper part of the Argentiniceras noduliferum Zone, and the FO of Colomisphaera conferta in the upper part of the Spiticeras damesi Zone (Ivanova and Kietzmann, 2017). The FO of Stomiosphaera wanneri is stratigraphic position (e.g., Lakova et al., 2017; Wimbledon et al., 2020), but the FO of N. wintereri is located close to the Jurassic/ Cretaceous boundary. Nonetheless, the Argentiniceras noduliferum Zone comprises a reverse polarity zone which was correlated by Iglesia Llanos et al. (2017) with the M16r Subchron, and therefore, the FO of N. wintereri occurs most likely in a lower stratigraphic position. The Calpionellopsis Zone spans the upper part of the Argentiniceras noduliferum Zone and the Spiticeras damesi Zone and is correlated with mid M16r - M14r Subchrons (Iglesia Llanos et al., 2017) that corresponds to the upper Occitanica and Boissieri Zones. In Cuesta del Chihuido, Puerta Curaco and El Trapial sections, some specimens that have been assigned to the species 24 D.A. Kietzmann, M.P.I. Llanos, F.G. Tomassini et al. Cretaceous Research 127 (2021) 104950 reported in Europe within the Simplex Subzone of the Calpionellopsis Zone (Wimbledon et al., 2020). However, this species occurs in Morroco, in the upper part of the Alpina Zone and becomes abundant from the upper part of the Elliptica Zone and the Calpionellopsis Zone (Benzaggagh and Atrops, 1996). The FO of Colomisphaera conferta occurs in the upper Berriasian, uppermost Calpionellopsis Zone, Murgeanui Subzone, near the BerriasianeValanginian boundary (Grabowski et al., 2016). Andreini, G., Caracuel, J.E., Parisi, G., 2007. Calpionellid biostratigraphy of the Upper TithonianeUpper Valanginian interval in Western Sicily (Italy). Swiss Journal of Geosciences 100, 179e198. ~ ez, C., Pujana, I., Lescano, M., Carignano, A.P., Ballent, S., Concheyro, A., N an s, A., Angelozzi, G., Ronchi, D., 2011. Microfo siles mesozoicos y cenCarame s, J.M. (Eds.), ozoicos. In: Leanza, H.A., Arregui, C., Carbone, O., Danieli, J.C., Valle n. Asociacio n GeoGeología y Recursos Naturales de la Provincia del Neuque gica Argentina, Buenos Aires, pp. 489e528. lo Benzaggagh, M., 2020. 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Marine Micropaleontology 52, 51e84. the Neuque Capelli, I., Scasso, R.A., Kietzmann, D.A., Cravero, F., Minisini, D., Catalano, J.P., 2018. Mineralogical and geochemical trends of the Vaca Muerta-Quintuco system in n Basin. Revista de la Asociacio n Geolo gica the Puerta Curaco section, Neuque Argentina 75 (2), 2010e2228. Capelli, I.A., Scasso, R.A., Spangenberg, J.E., Kietzmann, D.A., Cravero, F., Duperron, M., Adatte, T., 2021a. Mineralogy and geochemistry of deeply-buried marine sediments of the Vaca Muerta-Quintuco system in the Neuqu'en Basin (Chacay Melehue section), Argentina: Paleoclimatic and paleoenvironmental implications for the global Tithonian-Valanginian reconstructions. Journal of South American Earth Sciences 107, 103103. Capelli, I.A., Scasso, R.A., Cravero, F., Kietzmann, D.A., Vallejo, D., Adatte, T., 2021b. Late-diagenetic clay mineral assemblages in tuffs of the Vaca Muerta Formation n Basin, Argentina): insights into the diagenetic formation of chlorite. (Neuque Marine and Petroleum Geology 132, 105207. Catalano, J.P., Scasso, R.S., Kietzmann, D.A., Fӧllmi, K., Spangenberg, J., Capelli, I.A., 2018. Carbonate sedimentology and diagenesis of Vaca Muerta Formation in n Basin. In: 10 Congreso de Exploracio n y Desarrollo de Puerta Curaco, Neuque Hidrocarburos, pp. 1e19. Colom, G., 1948. Fossil Tintinnids: Loricated Infusoria of the Order of the Oligotricha. Journal of Paleontology 22, 2e33. Costanzo-Alvarez, V., Rapalini, A.E., Aldana, M., Díaz, M., Kietzmann, D.A., IglesiaLlanos, M.A., Cabrera, A., Luppo, T., Vallejo, M.D., Walther, A.M., 2019. A combined rock-magnetic and EPR study about the effects of hydrocarbonrelated diagenesis on the magnetic signature of oil shales (Vaca Muerta formation, southwestern Argentina). Journal of Petroleum Science and Engineering 173, 861e879. , L., Bernhardt, C., Ortiz, A.C., Gonza lez Tomassini, F., Craddock, P.R., Mosse Saldungaray, P., Pomerantz, A.E., 2019. Characterization and range of kerogen n Basin, Argentina. Organic properties in the Vaca Muerta Formation, Neuque Geochemistry 129, 42e44. Crame, J.A., 1999. An evolutionary perspective on marine faunal connections between southernmost South America and Antarctica. Scientia Marina 63, 1e14. Damborenea, S.E., 1993. Early Jurassic South American pectinaceans and circumPacific palaeobiogeography. Palaeogeography, Palaeoclimatology, Palaeoecology 100, 109e123. Damborenea, S.E., 2002. Jurassic evolution of Southern Hemisphere marine palaeobiogeographic units based on benthonic bivalves. Geobios 35 (24), 51e71. moire Spe cial. Me Damborenea, S.E., Echevarría, J., Ros-Franch, S., 2013. Southern Hemisphere Palaeobiogeography of Triassic-Jurassic Marine Bivalves. Springer Briefs in Earth System Sciences, p. 142. pez, L., 2012. Tectonostratigraphic analysis D'Elia, L., Muravchik, M., Franzese, J.R., Lo n Basin in the of the Late Triassic-Early Jurassic syn-rift sequence of the Neuque ~ ico depocentre, Neuque n Province, Argentina. Andean Geology 39, 133e157. San D'Elia, L., Bilmes, A., Naipauer, M., Vergani, F.D., Muravchik, M., Franzese, J.R., 2020. n Basin (Precuyano and Lower Cuyano Cycle): The Syn-Rift of the Neuque 9. Conclusions A regional biostratigraphic study based on calpionellids was n presented for the Upper JurassiceLower Cretaceous in the Neuque Basin, Argentina, in which five calpionellid standard zones were recognized: Chitinoidella, Crassicollaria, Calpionella, Calpionellopsis, and Calpionellites. These zones have been correlated with ammonites and polarity zones. The Chitinoidella Zone is divided into two subzones: Slovenica and Boneti, which are equivalent to the Tethyan Dobeni and Boneti Subzones, respectively. The Crassicollaria Zone includes the Remanei and Massutiniana Subzones. In the Calpionella Zone, we have recognized the Alpina Subzone and for the first time the Elliptica Subzone. The Calpion nellopsis Zone is also recornized for the first time in the Neuque Basin, and is divided into the Simplex and Oblonga Subzones. Some specimens of Calpionellites darderi allow characterizing the Calpionellites Zone for the first time. All these zones and subzones present a similar calpionellid assemblages than those reported from the Tethys regions. The cosmopolitan character of calpionellids allows to consolin basin and longdate the chronostratigraphy in the Neuque distance correlations between the Tethys and the Andes domains. Except for the lower part of the Vaca Muerta Formation, the achieved correlation shows an exceptionally good consistency with the magnetic polarity scales obtained recently in the studied basin, as well as with the biozones of other microfossils, such as nannofossils and calcareous dinoflagellates. Acknowledgments This research was supported by projects PICT 2016e3762 and n Científica 2018e02492 financed by Agencia Nacional de Promocio gica, Argentina. We acknowledge YPF and Chevron for y Tecnolo publication permission. We are especially indebted to Alberto C. Riccardi (Universidad Nacional de La Plata y Museo, Argentina) for the identification of the ammonites from Arroyo Loncoche and Cuesta del Chihuido sections. We especially thank Justyna KowalKasprzyk and Mohamed Benzaggagh for meticulous and constructive reviews that allowed to significantly improve the original version of the manuscript. We also thank Eduardo Koutsoukos for editorial handling. References Aguirre-Urreta, M.B., 2013. Amonoideos del Valanginiano-Hauteriviano de la tica, bioestratigrafía y paleobiogeografía. 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