Lower Tithonian Research Articles

Dinoflagellate cyst biostratigraphy of the Bathonian, Callovian, and the Upper Jurassic in North Bulgaria

Forty-four selected organic-walled dinoflagellate cyst species have been used for biozonation of the Bathonian, Callovian, and the Upper Jurassic in North Bulgaria. The dinocysts were collected from 49 borehole sections and two exposures. The following dinocyst zones are herein introduced and described: Lithodinium valensii–Gongylodinium erymnoteichos Concurrent-range Zone (lower–middle Bathonian); Ellipsoidictyon reticulatum Assemblage Zone (upper Bathonian–lower Callovian); Dingodinium harsveldtii Taxon-range Zone (middle–upper Callovian); Lambodinium absidatum Assemblage Zone (lower Oxfordian); Scriniodinium dictyotum papillatum–Caddasphaera halosa Concurrent-range Zone (middle–upper Oxfordian); Rhyncodiniopsis gongylos Assemblage Zone (lower Kimmeridgian); Systematophora varispinosa–Gonyaulacysta? crassicornuta Concurrent-range Zone (middle–upper Kimmeridgian); Edmontodinium polyplacophorum Assemblage Zone (lower Tithonian); and Leptodinium? plagatum–Prolixosphaeridium perforospineum Concurrent-range Zone (middle–upper Tithonian). Some of the zones were partly or completely subdivided in subzones. The dinocyst zones and subzones were correlated with the Bulgarian ammonite and calpionellid zones and subzones.

Middle and Late Jurassic record of sea-level, sequence development, and carbon-isotope fluctuations, Tethyan Adriatic Carbonate Platform, Croatia

The Adriatic Platform, Croatia is a large isolated carbonate platform that developed under a warm greenhouse climate interspersed with cooler episodes in western Tethys. However, the δ13C record and high-resolution sequence stratigraphy of the Middle and Upper Jurassic portion generally is poorly known. The ~1900 m thick (30 Myr duration) mainly Middle to Upper Jurassic succession of the platform was studied bed-by-bed to track the fluctuations of δ13C, facies stacking into bundles, superbundles, and sequences and potential sea-level changes within ongoing studies of evidence of astronomical forcing of the units. The study interval consists of cyclic subtidal intervals (upper Toarcian-lower Aalenian, lower Callovian, Oxfordian, lower Kimmeridgian, and lower Tithonian) interspersed with highly cyclic peritidal units (upper Bajocian-lower Bathonian, upper Kimmeridgian, and upper Tithonian-basal Berriasian). Ages were constrained by biostratigraphy and δ13C chemostratigraphy. The absolute δ13C values obtained from the shallow-marine bulk carbonate matrix are similar to those from coeval pelagic carbonates and exhibit similar trends, are characterized by overall little data spread (<2‰), and generally show little resetting associated with disconformities and/or burial. This rock-buffered record likely preserved at least relative marine δ13C values with several major excursions, including the BjBaE (Bajocian-Bathonian), CaOxBE (Callovian-Oxfordian boundary), EOxE, and MOxE (Early and Middle Oxfordian). The studied interval provides a detailed record of Milankovitch induced platform-flooding and exposure at scales from ~1Myr to ~20 kyr. The study suggests that detailed research of similar thick Jurassic isolated platform successions could provide valuable records of δ13C, climate, and sea-level changes over relatively long geological intervals.

COMPLEX BIOSTRATIGRAPHIC SCHEME OF THE JURASSIC DEPOSITS OF THE PIENNINE ZONE OF THE UKRAINIAN CARPATHIANS

The article summarizes the results of the study of paleontology and biostratigraphy of the Jurassic of the Piennine Zone of the Ukrainian Carpathians by domestic and foreign researchers. For the first time, a summary paleontological description of these sediments is presented, taking into account numerous published data on identified macro- and mictofossils. A correlation biozonal scale has been created, as well as complex biostratigraphic schemes for each Jurassic series of its region in accordance with the International Stratigraphic Scale (2020). Because the stratigraphic sequence was disturbed by disjunctive dislocations, these schemes were developed by analysis of fragmentary sections. At present, three series of the Jurassic are determined by ammonites, belemnites, pelecypods, brachiopods, the Lower and Upper series are also dated by dinocysts, the Upper also by foraminifera and tintinnids. The stages and standard zones of the modern international scale are determined by ammonites: Liasicus of the Gettangian; Bucklandi, Obtusum, Raricostatum of the Sinemurian; Jamesoni, Emaciatum of the Pliensbachian; Tenuicostatum, Serpentinum, Bifrons, Thouarcense of the Toarcien; Opalinum, Murchisonae, Bradfordensis, Concavum of the Aalenian; Propinquans, Humpriesianum, Parkinsoni of the Bajocian; Zigzag, Aurigerus, Subcontractus, Bremeri, Retrocostatum of the Bathonian; Athletа of the Callovian; Plicatilis і Bifurcates of the Oxfordian; Divisum, Acanticum і Cavouri of the Kimmeridgian. Continuous dinocyst zonation is traced in the Upper Jurassic – Fibrata Аcme (Upper Oxfordian), Parvula Acme, Moluccana і Borzai (Kimmerigian), Pulla, Tithonica, Malmica, Semiradiata (Lower Tithonian) and all standard tintinnide zones of Tithonian — Chitinoidella (підзони Dobeni і Boneti), Praetintinnopsella, Crassicollaria. The boundaries of the stages from the Gettangiean to the Oxfordian are not determined. The boundaries between the Lower and Upper Oxfordian as well as between the Kimmeridgian substages are determined by ammonites as well as the boundary between the Kimmeridgian and Tithonian is determined by dinocysts, and the boundary between the Jurassic and Cretaceous is determined by tintinnids (corresponds to the boundary between the zones Crassicollaria of Tithonian and Calpionella of Berriassian). Stratigraphic unconformities were revealed by the macro- and mictofossils: the regional erosion on the boundary between the Aalenian and Bajocian as well as in Early Callovian, and short gap on the boundary between the Lower and Upper Bajocian.

A juvenile specimen of Neusticemys neuquina (Testudinata: Thalassochelydia) from the Upper Jurassic of Neuquén Basin (Neuquén Province, Argentina)

ABSTRACT Cranial and postcranial remains of a juvenile specimen from the lower section of the Vaca Muerta Formation (Lower Tithonian) recovered at Cerro Lotena (Neuquén Province, Argentina) are identified as Neusticemys neuquina. We contextualised this juvenile specimen inside the taxonomic and phylogenetic background of N. neuquina. The new information provided by the juvenile specimen indicates that relevant key features such as: a strong constriction of the horizontal pterygoid plate at the level of the basis of the quadrate process of the pterygoid, a round depression basisphenoidal, a well-developed parasagittal crest developed on the dorsal surface of the squamosal, a medial keel on the posterior part of the carapace, hyo and hypoplastra contacting each other by a tight suture, do not change along ontogeny and as so they are reliable characters for taxonomy and phylogenetic analysis. We also comment on some ontogenetic changes between juvenile and adult specimens (e.g., increase of fossa infratemporalis and parietal horizontal plate in the skull, reduction in the height at the surangular region in the lower jaw, and the reduction of costo-peripheral fenestrae on the carapace) of N. neuquina. In addition, we compare this species with other early stage juvenile eurysternids from the European Upper Jurassic.

Kimmeridgian and early Tithonian cephalopods from the Kisújbánya Limestone Formation, Zengővárkony (Mecsek Mountains, southern Hungary), their faunal composition, palaeobiogeographic affinities, and taphonomic character

A new collection at Zengővárkony (Mecsek Mountains, Hungary) provided a rich and diverse but poorly preserved cephalopod-dominated fossil assemblage representing the Kimmeridgian and the lower Tithonian. The material came from mixed scree, soil, and amongst roots affected by weathering processes having been exposed to the elements for a long time. The nautiloid Pseudaganides strambergensis is the first record from the Mecsek Mountains. Due to the weathering, the ammonite fauna consists of mainly fragmentary and dissolved individuals that comprises 528 specimens belonging to 34 species and 30 genera out of which 20 species and 15 genera are reported for the first time from the Mecsek Mountains. The fauna includes specimens of known taxa. No new taxa are introduced. Based on the comparison with other faunas, this assemblage most closely resembles the fauna of the Venetian Alps (Italy). Additional faunal elements include aptychi (Laevaptychus latus, Lamellaptychus murocostatus), belemnites (Hibolithes semisulcatus), and an indetermined brachiopod. The first record of Spiraserpula spirolinites, an encrusting fossil polychaete preserved on the internal mould of a Taramelliceras shell fragment indicates favourable bottom conditions for the epifauna. The presence of Aspidoceras caletanum, Gravesia aff. gigas, and Pseudowaagenia inerme indicates faunal connections with the Submediterranean Province of the Tethys, which is in line with the tectonic and palaeogeographical position of the Mecsek Zone during the Late Jurassic. The ammonite assemblage represents elements of five Tethysian ammonite zones of the Kimmeridgian and Tithonian. The lower Kimmeridgian Herbichi Zone is indicated by Streblites tenuilobatus and Praesimoceras herbichi. The upper Kimmeridgian Acanthicum Zone is indicated by Aspidoceras acanthicum, and the Cavouri Zone by Mesosimoceras cavouri and Aspidoceras caletanum. The upper Kimmeridgian Beckeri Zone is suggested by Hybonoticeras pressulum and Pseudowaagenia inerme. Whereas Gravesia aff. gigas, Lithacoceras aff. siliceum, and Malagasites? denseplicatus are faunal elements characterising the Early Tithonian Hybonotum Zone. Phylloceratid and lytoceratid specimens account only for 12% of the fauna, while the majority of the specimens belong to the Oppeliidae and Ataxioceratidae (60%).

Facies analysis and stratigraphy across the Jurassic-Cretaceous boundary in a new basinal Tithonian–Berriasian section of the Vaca Muerta Formation, Las Tapaderas, Southern Mendoza Andes, Argentina

This paper presents a multidisciplinary study of a new basinal section of Tithonian-Berriasian the Vaca Muerta Formation at Las Tapaderas area, including detailed, biostratigraphic, sedimentologic, sequence stratigraphic and cyclostratigraphic analysis. Biostratigraphy based on ammonite, calpionellids and calcareous dinoflagellate cysts indicate that Las Tapaderas section spans through the Lower Tithonian - lowermost Upper Berriasian, however, its upper part is covered through an erosive unconformity by Pleistocene volcaniclastic deposits, and therefore Las Tapaderas section could reach the Lower Valanginian. Two facies associations were identified, corresponding to basinal and distal outer ramp subenvironments. Recognition of flooding surfaces allowed the identification of three composite depositional sequences and eight high-frequency depositional sequences, which can be correlated with other sections throughout the basin. Cyclostratigraphic analysis based on the recognition of marlstone/limestone couples (elementary cycles) allowed to build a time series based on bed thickness. Fourier analysis indicates the characteristic mid latitude precession-eccentricity syndrome, with 220 precessional cycles (~20.4 and ~23 kyr), 53 low frequency eccentricity cycles (~79, ~90 and ~140 kyr) and 11 high frequency eccentricity cycles (~400 kyr). Spectral analysis also allowed to recognize the presence of the obliquity cycle (38.5 kyr), which has been erratically recorded in the Vaca Muerta Formation. Our data allowed the construction of an orbital scale, calibrated by cosmopolitan markers (calpionellids and calcareous dinoflagellate cysts), for this section. The precise bio- and cyclostratigraphic location of the Jurassic-Cretaceous boundary was established for this section. The sedimentation rate was studied at the scale of the precession cycle, showing values between 0.6 and 3 cm/kyr, while at the low-frequency eccentricity scale it shows values between 1 and 2 cm/kyr.

A new species of Cricosaurus (Thalattosuchia: Crocodylomorpha) from southern Germany: the first three-dimensionally preserved Cricosaurus skull from the Solnhofen Archipelago

Cricosaurus represents one of the most important radiations within Metriorhynchidae, a specialized marine clade of Crocodylomorpha that flourished in marine environments from the Middle Jurassic until the Early Cretaceous. Here, we describe a new species of Cricosaurus, Cricosaurus rauhuti sp. nov., from the Mörnsheim Formation (lower Tithonian) of southern Germany. The specimen is the first three-dimensionally preserved Cricosaurus from this realm, and it is represented by a partially preserved cranium and lower jaw that has autapomorphic characters that distinguish it from any other species of Cricosaurus. The phylogenetic analysis shows that the new species is more closely related to some non-European forms from the Late Jurassic and one taxon from the Valanginian of Germany (all 3D-preserved) than to other Late Jurassic Cricosaurus from southern Germany (all 2D-preserved). Our exploratory analyses confirm that this is not a preservation bias. For the first time, this shows that there are two clades of Cricosaurus present during the Late Jurassic in Germany. Furthermore, it provides additional evidence of a close faunal relationship between Europe and South America in the Late Jurassic, as also evidenced by the fossil record of other marine reptiles. Finally, the distribution of metriorhynchids in localities of the Solnhofen Archipelago suggests a change in the taxic diversity of the region during the early Tithonian, which might be the result of environmental changes in the Solnhofen Archipelago. http://zoobank.org/urn:lsid:zoobank.org:pub:488705BF-AEAD-4F02-BB4E-429E3117BCD1

Tectonic control on hydrocarbon generation in the northwestern Neuquén Basin, Argentina

The petroleum systems of the Malargue fold–thrust belt in the northwestern Neuquen Basin, Argentina, comprise multiple reservoir and seal rocks and three major source rocks of the Lower Jurassic (Los Molles Formation [Fm.]), the lower Tithonian to lower Valanginian (Vaca Muerta Fm.), and the lower Hauterivian to lower Barremian (Agrio Fm.). The thermal history of the Mesozoic source rocks has been reconstructed using one-dimensional and two-dimensional modeling. The most important factors that affected the source-rock maturation are the timing of maximum Late Cretaceous to Paleogene burial and the heat flow during back-arc extension. We postulate that synclines have been buried over longer periods and source-rock maturation ceased earlier in anticlines, accordingly. Hydrocarbon generation from the Vaca Muerta Fm. and Agrio Fm. has started during the Campanian. Despite late-stage magmatic activity causing local thermal perturbations, the models suggest that the thermal field has been dominated by conductive heat transport and that heat flow has been a response to the evolution from back-arc extension to orogenic shortening. High heat flows of 85 mW/m2 during back-arc extension between the latest Cretaceous and Paleogene have been modeled. Two main source pods supply hydrocarbons until the present. They are related to structurally deep footwall positions of thrust faults, active since the Late Cretaceous, and to deep frontal synclines, having formed through late-stage thick-skinned tectonics since the Neogene. Modeling of hydrocarbon fluid type is consistent with existing oil fields exhibiting light and medium oils with API between 22° API and 39° API, charged from early- to peak-mature source rocks.

Macrofauna and biostratigraphy of the Rollrock Section, northern Ellesmere Island, Canadian Arctic Islands – a comprehensive high latitude archive of the Jurassic–Cretaceous transition

The Rollrock Section in the Sverdrup Basin of Arctic Canada is one of the northernmost outcrops where the Jurassic-Cretaceous transition is accessible. The over 500 m thick sedimentary succession exposes the Oxfordian to Valanginian Ringnes and Deer Bay formations. Macrofauna from 15 discrete horizons includes ammonites, Buchia bivalves and belemnites. These fossils improve the biostratigraphy of the Tithonian and Berriasian in the Sverdrup Basin, provide correlation to the remainder of the Boreal Realm and set reliable calibration points. The occurrence of Buchia rugosa in the Ringnes Formation moves the upper formation boundary from the top of the Kimmeridgian into the lower Tithonian. Dorsoplanites maximus and D. sachsi document the middle Tithonian Dorsoplanites maximus Zone in Arctic Canada for the first time. The late Tithonian to early Berriasian Buchia terebratuloides is considered to be the best approximate indicator of the Jurassic-Cretaceous transition in the Rollrock Section. The middle early Berriasian Praetollia maynci and the late early Berriasian Borealites fedorovi tie the respective horizons to the successive Chetaites sibiricus and Hectoroceras kochi zones. Two species of the belemnite Arctoteuthis, collected from an interval with common glendonites, suggest a Valanginian age for the upper Deer Bay Formation. The dearth of Late Jurassic to earliest Cretaceous macrofossils in the Sverdrup Basin is inferred to be predominantly a function of diagenetic carbonate loss. Abundant dropstones and glendonites in the middle Tithonian to middle Valanginian interval suggest cold climatic conditions, and make the Rollrock Section a prime candidate for studying the Arctic environmental perturbations of this time.

A new caridean shrimp (Crustacea: Decapoda) from the Solnhofen Lithographic Limestones (Upper Jurassic, southern Germany)

A new caridean shrimp, Hefriga schlechtingerae n. sp., is described from the Upper Jurassic Solnhofen Lithographic Limestones (Altmühltal Formation, Eichstätt Member; Lower Tithonian, Hybonotum Zone). It adds to the surprisingly high diversity of carideans in the Solnhofen Archipelago.

Lower Tithonian and lower Berriasian brachiopods from the M\xe1r\xe9v\xe1r Limestone Formation, Zeng\u0151v\xe1rkony (Mecsek Mountains Hungary), and remarks on their palaeoenvironment

A new collection provided some brachiopods assigned to Lacunosella hoheneggeri, Pygope diphya and P. janitor from the lower Tithonian (Micracanthoceras ponti Zone) and lower Berriasian (Calpionella Zone), and from the limestone succession at Zengővárkony, Mecsek Mountains, Hungary. This is the first taxonomic description and photographic documentation of these fossils. We provide reliable documentation of pygopid brachiopods from the Mecsek Mountains, known since 1880, but previously not described. For the moment, three pygopid brachiopod species are reliably reported from the Mecsek Mountains: Pygope diphya, P. janitor and Pygites diphyioides. The Lacunosella hoheneggeri described herein is the first record of Berriasian rhynchonellide brachiopods from the Mecsek Mountains. The lower Berriasian brachiopods may belong to a normal palaeoenvironment, with the usual size distribution.

The first non-pterodactyloid pterosaurian trackways and the terrestrial ability of non-pterodactyloid pterosaurs

New discoveries on the ichnological site known as “the Pterosaur Beach of Crayssac” (lower Tithonian, Upper Jurassic; south-western France) answer the question of terrestrial capabilities of non-pterodactyloid pterosaurs. If the terrestrial type of locomotion of pterodactyloid pterosaurs has been solved from ichnological evidence for more than twenty years, no tracks and trackways referable to non-pterodactyloid pterosaurs have ever been described. Thus, the debate on terrestrial capabilities of these non-pterodactyloids was based on morpho-functional studies, with the main conclusion that those pterosaurs were arboreal dwellers and bad walkers. Six trackways referable to three non-pterodactyloid new ichnotaxa, maybe closely related to Rhamphorhynchidae, are described in this work. Their study leads to the conclusion that grounded non-pterodatyloids, at least during the Late Jurassic, were quadrupedal with digitigrade manus and plantigrade to digitigrade pes. They were clearly good walkers, even if hindlimbs are supposed to be hampered by the uropatagium, what could have constrained the terrestrial agility of these animals. Thus, from ichnological evidence and contrary to the current hypotheses, non-pterodactyloid pterosaurs seem to have been good walkers even though their trackways are very rare or unidentified to date. This rarity could be due to behaviour rather than to functional capacities, many non-pterodactyloids being considered both littoral fishers and arboreal or cliff dwellers. However, the concept of non-pterodactyloid “good climbers and bad walkers” has to be modified to “good climbers and rare walkers”, unless many non-pterodactyloid ichnites have yet to be discovered.

A non-archaeopterygid avialan theropod from the Late Jurassic of southern Germany.

The Late Jurassic 'Solnhofen Limestones' are famous for their exceptionally preserved fossils, including the urvogel Archaeopteryx, which has played a pivotal role in the discussion of bird origins. Here we describe a new, non-archaeopterygid avialan from the Lower Tithonian Mörnsheim Formation of the Solnhofen Archipelago, Alcmonavis poeschli gen. et sp. nov. Represented by a right wing, Alcmonavis shows several derived characters, including a pronounced attachment for the pectoralis muscle, a pronounced tuberculum bicipitale radii, and a robust second manual digit, indicating that it is a more derived avialan than Archaeopteryx. Several modifications, especially in muscle attachments of muscles that in modern birds are related to the downstroke of the wing, indicate an increased adaptation of the forelimb for active flapping flight in the early evolution of birds. This discovery indicates higher avialan diversity in the Late Jurassic than previously recognized.

Reconstruction of a Late Jurassic–Early Cretaceous carbonate platform margin with composite biostratigraphy and microfacies analysis (western Sakarya Zone, Turkey): Paleogeographic and tectonic implications

During Late Jurassic–Early Cretaceous the Pontides were the site of a wide carbonate platform facing the Tethys ocean in the south. In the western Pontides the Upper Jurassic–Lower Cretaceous shallow marine carbonates abut the Tethyan İzmir-Ankara suture with no evidence for platform margin deposits. The Sivrihisar klippe 50 km south of the İzmir-Ankara suture preserves a record of the missing platform margin. In the Upper Jurassic–Lower Cretaceous carbonates exposed in this Sivrihisar klippe, two coeval but dissimilar rock packages, separated by a thrust fault, have been detected. The lower succession is composed of Kimmeridgian–Valanginian slope to basin deposits. Within these carbonates the following biozones are defined: Globuligerina oxfordiana – Mohlerina basiliensis Zone (Kimmeridgian), Saccocoma Zone (lower Tithonian), Protopeneroplis ultragranulata Zone (upper Tithonian), Crassicollaria Zone (massutiana Subzone – uppermost Tithonian), Calpionella Zone (alpina, Remaniella, elliptica Subzones – lower Berriasian), Calpionellopsis Zone (simplex, oblonga Subzones – upper Berriasian) and Calpionellites Zone (darderi Subzone – lower Valanginian). These slope to basin deposits are overthrust from north to south by Kimmeridgian shallow marine carbonates. Within this unit Labyrinthina mirabilis – Protopeneroplis striata Zone (Kimmeridgian) is recognized. Based on the distribution of microfacies types and fossil assemblages, a Kimmeridgian–Valanginian depositional model is proposed for the western Sakarya Zone Carbonate Platform (SCP). The position of the studied sections with respect to the SCP, biofacies and microfacies associations suggest that the studied basin and slope deposits represent the remnants of the southern margin and slope of this carbonate platform largely truncated by erosion. The slope and basinal carbonates overthrusted by the coeval shallow marine deposits in a region situated to the south of the main İzmir-Ankara suture indicates an important imbrication and shortening related to the closure of the Tethys ocean.

Magnetostratigraphy and cyclostratigraphy of the Tithonian interval from the Vaca Muerta Formation, southern Neuquén Basin, Argentina

A cyclostratigraphic and paleomagnetic study was carried out in the lower part of the Vaca Muerta Formation, Los Catutos Member (Lower to lowermost Upper Tithonian) at the southern region of the Sierra de la Vaca Muerta, Neuquén Basin, west-central Argentina. The Vaca Muerta Formation is known for its unconventional resource potential and its exceptional behaviour as a world-class source rock. The studied section is c. 90 m thick and is characterized by decimetre-scale rhythmic alternations of marls, mudstones and limestones, showing a well-ordered hierarchy of cycles. Elementary cycles, bundles and superbundles were recognized with frequencies within the Milankovitch spectrum band. A total of 280 standard specimens collected from 35 paleomagnetic sampling horizons, dated with ammonites, were analyzed. The quality and primary origin of the characteristic magnetization was proved through the corresponding reversal test. A magnetostratigraphic scale was thus constructed that comprises 5 reverse and 4 normal polarity intervals, spanning the Andean Virgatosphinctes andesensis (ex mendozanus) (Lower Tithonian) to Windhauseniceras internispinosum (lowermost Upper Tithonian) ammonite Zones. Polarities were correlated with the GPTS 2016 using the equivalences between the Andean and Standard ammonite zones which, allowed to interpret that Los Catutos section was deposited between M22r to M20n Subchrons. By means of the correlation between the cyclostratigraphic and magnetostratigraphic scales, it was possible to date the Tithonian succession with unprecedented precision. Rock magnetic studies indicate that the remanence is carried by titanomagnetite.

Calcareous dinoflagellate cysts from the Tithonian - Valanginian Vaca Muerta Formation in the southern Mendoza area of the Neuquén Basin, Argentina

The Late Jurassic – Early Cretaceous marine sediments of the Andean region show an excellent record of different calcareous microfossils, among which calcareous dinoflagellate cysts stand out. Detailed micropaleontological studies of Vaca Muerta Formation (Early Tithonian – Early Valanginian) in the southern Mendoza Neuquén Basin from three sections are conducted with the aim of establishing a major presence of microfossil representatives from different microfossil groups. The analysis of several thin sections from the outcrops reveals a relatively rich micropaleontological assemblage of calcareous dinoflagellate cysts, as well as levels with poor preserved calpionellids and benthic foraminifera. Particularly, calcareous dinoflagellate cyst includes 24 known species (two of them with two subspecies). Some species with biostratigraphic value of the Tethyan region have been identified also in the Andean region: 1) Committosphaera pulla (Borza) and Parastomiosphaera malmica (Borza) are species known only from Lower Tithonian; 2) Colomisphaera tenuis (Nagy) appears in the latest Early Tithonian; 3) Colomisphaera fortis Řehánek and Stomiosphaerina proxima Řehánek are important markers for the latest Late Tithonian – middle Late Berriasian interval; 4) Stomiosphaera wanneri Borza appears in the middle Late Berriasian; 5) Colomisphaera conferta Řehánek and Colomisphaera vogleri (Borza) appear in the Late Berriasian and marked the Berriasian-Valanginian boundary interval; 6) Carpistomiosphaera valanginiana Borza is a marker for the Lower/Upper Valanginian. More detailed studies of these groups will allow their correlation with Tethyan biozones, and contribute to improve biostratigraphic schemes in the Neuquén Basin.

Integrated biostratigraphy and carbon isotope stratigraphy of the Upper Jurassic shallow water carbonates of the High-Tatric Unit (Mały Giewont area, Western Tatra Mountains, Poland)

New biostratigraphical and carbon isotope data are presented for the Upper Jurassic limestones of the Raptawicka Turnia Limestone Formation (High Tatric unit, Western Tatra Mountains, Poland) from the Maly Giewont area. The Kimmeridgian, lower Tithonian and lower part of the upper Tithonian have been identified on the basis of calcareous dinocysts and calpionellids. Eight microfossil biozones are distinguished: acme Fibrata, acme Parvula, Moluccana, Borzai, Tithonica acme Pulla(?), Malmica, Chitinoidella and Crassicollaria ( pars ). The Kimmeridgian/Tithonian boundary is indicated at the top of the Borzai Zone 76 m above the base of the Raptawicka Turnia Limestone Formation. The microfossil stratigraphy suggests the late Early Kimmeridgian age ( acme Parvula Zone) of the ammonites described by Passendorfer (1928). The taxon Taramelliceras ex gr. compsum found 14 m above those ammonites is Late Kimmeridgian in age. Seven microfacies types (MF) are identified in the Upper Jurassic limestones of the Maly Giewont area. The Bositra -Saccocomidae MF occurs across the Lower-Upper Kimmeridgian boundary. The planktonic and benthic foraminifera occur in the Upper Jurassic deposits of the Raptawicka Turnia Limestone Formation. The genera Lenticulina Lamarck and Spirillina Ehrenberg are common in the Kimmeridgian and Tithonian limestones. The palaeobathymetric evolution of the Kimmeridgian-Tithonian deposition recorded in the Maly Giewont sections reveals: the transgressive episode at the Lower/Upper Kimmeridgian boundary interval, the transgression peak during the Early Tithonian (Malmica Zone) and gradual shallowing of the High-Tatric swell in the Late Tithonian. Integrated isotope stratigraphy and biostratigraphy enabled correlation with the pelagic section of the Sub-Tatric succession in the Dluga Valley section. The middle part of the Raptawicka Turnia Limestone Formation (Upper Kimmeridgian) might be correlated with the upper part of the Czajakowa Radiolarite Formation (red radiolarites) and Czorsztyn Formation in the Dluga Valley section. The upper part of the Raptawicka Turnia Limestone Formation of Early Tithonian age corresponds mostly to the Jasenina Formation. The overall similarity of the δ 13 C decreasing values recorded in the Kimmeridgian–earliest Tithonian interval of the Maly Giewont (this study) and Dluga Valley sections indicates that the generally shallow-water deposits of the Raptawicka Turnia Limestone Formation accumulated below the zone influenced by changes in the composition of marine water caused, for instance, by intense rainfalls.

Magnetostratigraphy of the Upper Jurassic–Lower Cretaceous from Argentina: Implications for the J-K boundary in the Neuquén Basin

A systematic sedimentologic and paleomagnetic study was carried out in the Vaca Muerta Formation, cropping out in the northern Neuquén Basin, west-central Argentina. The studied section is c. 280 m-thick and represents a carbonate ramp system bearing ammonites that indicate Late Jurassic–Early Cretaceous ages. The Vaca Muerta Formation is one of the most important unconventional hydrocarbon reservoirs in the world and its thorough study has become a relevant target in Argentina. The J-K boundary is comprised within this unit, and although it is well-dated through biostratigraphy (mainly ammonites), the position of particularly the boundary is yet a matter of hot debate. Therefore, the systematic paleomagnetic and cyclostratigraphic study in the Vaca Muerta Formation was considered relevant in order to obtain the first Upper Jurassic–Lower Cretaceous magnetostratigraphy of the southern hemisphere on the first place and to precise the position of the J-K boundary in the Neuquén Basin, on the other. Biostratigraphy is well studied in the area, so that paleomagnetic sampling horizons were reliably tied, particularly through ammonites. Almost 450 standard specimens have been processed for this study distributed along 56 paleomagnetic sampling horizons that were dated using ammonites. Paleomagnetic behaviours showed to be very stable, and their quality and primary origin have been proved through several paleomagnetic field tests The resultant magnetostratigraphic scale is made up of 11 reverse and 10 normal polarity zones, spanning the Andean Virgatosphinctes mendozanus (lower Tithonian) to Spiticeras damesi Zones (upper Berriasian). These polarity zones were correlated with those of the International Geomagnetic Polarity Time Scale 2012 and 2016 through the correlation between Andean and Tethyan ammonite zones. Cyclostratigraphy on the other hand, proved to be quite consistent with the magnetostratigraphy. Through the correlation of the resultant paleomagnetic and cyclostratigraphic data, it was possible to date the section with unprecedented precision, and therefore, to establish the position of the Jurassic-Cretaceous boundary. The paleomagnetic pole calculated from the primary magnetization is located at: Lon = 191.6°E, Lat = 76.2°S, A95 = 3.5°, indicating a c. 24° clockwise rotation for the studied section, which is consistent with structural data of the region.

Passage Jurassique-Crétacé sur la plate-forme carbonatée gétique (Carpathes méridionales, Roumanie) : Foraminifères et algues benthiques

The carbonate succession of the Piatra Craiului Massif, i.e., the eastern part of the Getic carbonate platform (Southern Carpathians, Romania), comprises reefal and peritidal limestones that contain a diverse microfossil assemblage composed mainly of calcareous green algae and benthic foraminifera. The biostratigraphically most significant benthic foraminifera found in the several sections studied are described; some (Anchispirocyclina lusitanica, Neokilianina rahonensis, Bramkampella arabica, Everticyclammina praekelleri) are reported for the first time in this area. Hence, assemblages of both foraminifera and calcareous algae characterize three biostratigraphic intervals in the studied succession, the Kimmeridgian - lower Tithonian, the upper Tithonian - lower Berriasian, and the upper Berriasian - ? lower Valanginian intervals. The main microfacies types (bioclastic rudstone, coral-microbial boundstone, bioclastic grainstone, interbedded mudstones and wackestones with cyanobacteria nodules) as well as both the foraminifera and the calcareous algae are paleoecological indicators that may contribute to the decipherment of the depositional environments and to building a depositional model for the eastern part of the Getic carbonate platform at the Late Jurassic-Early Cretaceous transition.

The Braincase Assigned to the Ornithopod DinosaurUteodonMcDonald, 2011, Reassigned toDryosaurusMarsh, 1894: Implications for Iguanodontian Morphology and Taxonomy

ABSTRACT The braincase from the Upper Jurassic (lower Tithonian) Morrison Formation of the Carnegie Quarry at Dinosaur National Monument (Utah), which was assigned to the ankylopollexian iguanodontian ornithopod dinosaur Uteodon aphanoecetes (Carpenter and Wilson, 2008) is actually that of the dryosaurid iguanodontian Dryosaurus cf. D. altus (Marsh, 1878). The purported braincase autapomorphy of U. aphanoecetes, occipital condyle projects farther ventrally than basal tubera, is an artifact of damage to the latter structures in this specimen. The newly identified braincase of Dryosaurus Marsh, 1894, reveals features that are not easily observed in other specimens of this taxon, such as well-developed fossae on the anterior surfaces of the paroccipital processes and a spike-shaped parasphenoid that lacks the dorsal process seen in Dysalotosaurus Virchow, 1919. The distinction of this latter dryosaurid genus from Dryosaurus is here regarded as tentative. The removal of the braincase in question from the hypo...