Campanian Research Articles

Triprojectacites in the Songliao Basin, Northeast China: Systematics, biostratigraphy and evolution

Triprojectate pollen plays an important role in the division and correlation of the Upper Cretaceous strata for their short stratigraphic distribution, high diversity and rapid evolution rate. Long time scale material with good age constraints that is highly valuable for studying its origin, evolution and extinction is particularly rare. In this study, we report a successive sequence of Triprojectacites evolving since its origin through the extinction during the Late Cretaceous in the Songliao Basin, northeastern China. We applied a combined observation technique using both optical microscope and scanning or transmission electron microscope on single pollen grain for the morphological observation and systematic classification. A total of seven genera, thirty-five species (including two new species, Aquilapollenites prenormalis sp. nov. and Bratzevaea pumila sp. nov.) and one conformis species are described. The occurrence and range of specific species are precisely logged on the core sectivon. Five development phases of the Triprojectacites palynoflora are recognized, ascendingly: I. Occurring phase (the earliest Campanian), II. Radiating phase (the early Campanian), III. Standing phase (the middle–late Campanian), IV. Flourishing phase (the latest Campanian–the early Maastrichtian), and V. Fading phase (the middle–late Maastrichtian). The record shows that Triprojectacites in the Songliao Basin has experienced a morphological evolution of being larger in size, more robust and complicated in ornamentation, and the development of accessory structures. The latter, especially the birth of collar ring, is indicative of the Maastrichtian in age.

Palm fronds from western Canada are the northernmost palms from the Late Cretaceous of North America and may include the oldest Arecaceae

Palm leaf fossils are common from Late Cretaceous floras in the United States, but Late Cretaceous Canadian palm records are limited largely to Nanaimo Group strata of British Columbia, with only anecdotal records from east of the Rocky Mountains. Here we report Late Cretaceous leaf fossils from Alberta and Saskatchewan, Canada. Segment angles with the rachis or costa are investigated as an additional character to distinguish costapalmate from pinnate and entire-pinnate palm leaves. The leaf fossils from Alberta and Saskatchewan represent costapalmate-palms (Sabalites), in contrast to the relatively common entire-pinnate palm fossils known from the Coniacian–early Campanian lower Nanaimo Group of British Columbia (e.g., Geonomites imperialis; potentially the oldest known North American palm) and the Campanian Two Medicine Formation of Montana (cf. Phoenicites). The presence of fossil palms in the Campanian to Maastrichtian of Alberta and Saskatchewan constrains climate reconstructions for the Late Cretaceous high mid-latitudes of North America (c. 55° N) to exclude significant freezing episodes. Additionally, we update the nomenclature for G. imperialis, renaming it as a species of Phoenicites, and briefly consider its value to understanding the evolution of pinnate palms. Further, we challenge the interpretation of Sabalites magothiensis as a costapalmate species and reassess the age of S. carolinensis as late Campanian.

A new, Late Cretaceous gonorynchiform fish in the genus †Notogoneus from drill core of crater-lake deposits in a kimberlite maar, Northwest Territories, Canada

The Gonorynchiformes are a group of mostly marine fishes that are the sister group to the Otophysi (e.g., carps, tetras, catfishes). They include milkfishes (family Chanidae) and beaked sandfishes (family Gonorynchidae) among extant taxa. The only freshwater genus is the strictly fossil †Notogoneus, which until now contained eight species of Late Cretaceous to early Miocene age. A ninth species, †Notogoneus maarvelis, sp. nov., is described here from a single, small specimen found in a diamond-exploration drill core into strata deposited in a kimberlite maar lake in northern Canada. The maar crater was formed by the explosive emplacement of the “Wombat” kimberlite pipe, one of many in the nearby region. The new species is the oldest known member of the genus †Notogoneus and is dated by U–Pb geochronology on associated tephras as early Campanian or about 82 Ma. Although very small, the type and only specimen is very similar in morphology, meristics, and body proportions to the type species †N. osculus. The most important difference is that the origin of the pelvic fin in the new species is beneath vertebral centrum 26, whereas the origin of the dorsal fin is above vertebral centrum 20. In †N. osculus, in contrast, the two fins both originate opposite centrum 22 or 23. The new species is the only one known among those of †Notogoneus or the extant Gonorynchus in which the pelvic fin origin is well behind that of the dorsal fin. The new species agrees with †N. osculus and other congenerics in key attributes of the genus †Notogoneus, including subopercular clefts and, in the caudal skeleton, autogenous parhypural plus hypurals 1 and 2. The bones of the new species ossified at a much smaller size than did those of young individuals of †N. osculus, suggesting that the new species likely attained a much smaller adult size as well. This small, new species, as well as other unidentified fish fragments, was discovered in a core into maar-lake deposits within otherwise fossil-poor areas of the North American craton. Such discoveries highlight the potential importance of maar lakes and similar crater-lake settings for revealing more about fish diversity in the Late Cretaceous than has been previously known.

Radiolaria and planktonic foraminifera from Sarama composite section of the Kannaviou Formation (Campanian, Upper Cretaceous, Cyprus)

Radiolarians and planktonic foraminifers were studied from a series of continuous outcrops of the Upper Cretaceous (upper Campanian) Kannaviou Formation near Sarama Village (southwestern Cyprus). The composite study section has a narrow stratigraphic interval that covers the upper Campanian, with a total thickness of more than 70 m. The Amphipyndax tylotus (radiolarian) Zone is found within the study section. According to foraminiferal data the studied interval corresponds to the middle-upper Campanian age (from Contusotruncana plummerae Zone to the lower part of Gansserina gansseri Zone).

Geothematic map of the Altamura dinosaur tracksite (early Campanian, Apulia, southern Italy)

In 2019 a multidisciplinary study of the Altamura dinosaur tracksite (Apulia, southern Italy; early Campanian) was carried out to meticulously document its geological and palaeontological features. The goal was to pave the way for projects aimed at long-term conservation and valorisation of the geo-palaeontological heritage. For this purpose, a mapping of the whole track-bearing surface was performed, which led to the production of the first geothematic map (1:200) of the whole ichnosite. During the field activities, the surface was subdivided into 34 distinct sectors. For each sector, the work started with accurate manual and mechanical cleaning of the surface (industrial vacuum cleaner). The ichnological survey was carried out using standard methods (interpretative drawings with chalks to highlight outline and morphological features of each track). This approach was combined with close-range photogrammetry to obtain detailed 3D models of the best-preserved specimens. Finally, each sector was surveyed through aerial-based photogrammetry by means of sUAS (small Unmanned Aerial System). The aerial survey allowed us to gain a high-resolution and georeferenced orthophoto processed by using specific software. The field ichnological drawings occurring on each orthophoto were then traced and vectorised. The final step was the overlapping of each digitised sector and the processing of the tracksite map. The products of our study (geothematic map and 3D models of dinosaur tracks) highlight the extraordinary richness of the Altamura tracksite (26,000 footprints and 12 distinct trackways), confirming the high impact of new methodologies (close-range and aerial- based photogrammetry) as useful tools both for ichnological studies and future activities of public fruition of the geosite.

Structure and condition of formation of Campanian deposits of the North-Western Caucasus (Galitsyno section)

The description of rocks in the Galitsyno quarry located in the Adler region of the North Caucasus is given. The quarry is interesting because the excellent exposure in a relatively homogeneous stratum of carbonate rocks was able to identify certain changes that reflect the events common to the Late Cretaceous, in this case, Late Campanian, interval of events. These include carbonate sedimentation characteristic of this geochronological interval, constant fluctuations of the relative sea level, and periodic manifestations of volcanic activity. All these features confirmed both by the structural features of the section, the presence of various lithological types of rocks in it, and by the features of the composition of the complexes of microorganisms. The use of different methods of analysis of the factual material makes the obtained conclusions convincing.

The Upper Cretaceous Rock Springs Formation of northwest Colorado

The Upper Cretaceous Rock Springs Formation of the Mesaverde Group in northwestern Colorado, southwestern Wyoming, and northeastern Utah is composed of fluvial, deltaic, and marine sediments that record the regression of the Western Interior Seaway during the Early to Middle Campanian. Contemporaneous deposits are present along the eastern and southeastern margins of the Greater Green River Basin in Wyoming, but correlation across the basin is challenging. Analysis of a small (1-km-long), understudied outcrop in northwestern Colorado assists in bridging that gap. The outcrop consists of distal and proximal deltaic deposits, overlain by distributary-channel complexes within delta-plain deposits. Correlation panels based on subsurface wireline logs and outcrop gamma-ray profiles show that the deposits are younger than lithostratigraphically equivalent strata of the Rock Springs Formation in Utah and Wyoming. Regional nomenclature is introduced for the area, and it is shown that these deposits differ from better-documented, older Rock Springs Formation deposits in Utah and Wyoming by having a higher net sandstone percentage due to the presence of substantial distributary-channel complexes. This study benefits subsurface exploration efforts in the Greater Green River Basin by providing outcrop analogs of reservoir distribution and quality.

Santonian-Campanian neoselachian faunas of the Upper Cretaceous Yezo Group in Nakagawa Town, Hokkaido, Japan

Fifty-one fossil shark teeth, including Hexanchiformes, Echinorhiniformes, Squaliformes and Lamniformes, are described from two localities in Nishichirashinai and Omagari formations of the Yezo Group in Nakagawa Town, Hokkaido, Japan. They include the first occurrence of Protosqualus from the northwestern Pacific and suggest the onset of the adaptation to deep-water environments of the Squaliformes in this region by early Campanian. Different sedimentary settings of the two localities may have caused different taxonomic compositions. The co-existence of Hexanchiformes and Lamniformes is also known in a contemporaneous Japanese fauna and those of southern high latitudes and suggests effects of paleogeographic settings on the global distribution of Upper Cretaceous neoselachian taxa.

Planktonic foraminiferal biostratigraphy and determination of the Santonian-Campanian boundary in the Zagros sedimentary basin, SW Iran

The carbonate-dominated Upper Cretaceous Ilam Formation is representative of an important reservoir in the Zagros Basin. In this study, planktonic foraminiferal biostratigraphy of the Ilam Formation was investigated in the Kuh-e-Surgah section in western Iran. In the studied section, the 170 m thick Ilam Formation is mainly composed of imestones with shale intercalations. The formation conformably overlies and underlies the Surgah and Gurpi formations, respectively. Twelve genera and 24 species of planktonic foraminifera were identified. The following planktonic foraminiferal biozones were identified: the Dicarinella asymetrica Total Range Zone (latest Coniacian- late Santonian), the Globotruncanita elevata Partial Range Zone (Santonian to early Campanian), the Globotruncana ventricosa Interval Zone (middle to late Campanian.), the Radotruncana calcarata Total Range Zone (late Campanian.), the Globotruncanella havanensis Partial Range Zone (late Campanian) and the Globotruncana aegyptiaca Interval Zone (late to latest Campanian). In general, the biozones show that the Ilam Formation in the studied section is latest Coniacian-late Campanian in age. The Santonian-Campanian boundary in the Kuh-e-Surgah section correlates with the Globotruncanita elevata Partial Range Zone. The recognized biozones in the Ilam Formation are comparable with those recorded in other parts of the Tethyan Realm. The crinoid species Marsupites testudinarius is absent in the studied section. Generally, the last occurrence of this cosmopolitan species indicates the base of the Campanian stage. The Santonian/Campanian boundary was placed in the lower part of the Globotruncanita elevata Partial Range Zone at the base of the Ilam Formation in the studied section.

Relationship between tight reservoir diagenesis and hydrocarbon accumulation: An example from the early Cretaceous Fuyu reservoir in the Daqing oil field, Songliao Basin, China

It is crucial to determine the sequence of reservoir tightening and hydrocarbon accumulation for analyzing the accumulation dynamics, oil migration mode, and oil distribution pattern of tight oil reservoirs. The tight sandstone reservoirs in the Fuyu reservoir occur in both the Daqing Anticline (DA) and Sanzhao Sag (SS), which were used as examples for the qualitative and semiquantitative analyses conducted herein. By integrating the porosity and permeability data, thin section imaging, cathode luminescence, scanning electronic microscopy, and energy dispersive spectra, the diagenesis processes including compaction, calcite cementation and replacement, illite precipitation, quartz overgrowth, and dissolution were analyzed. Typical diagenetic processes and successive orders were established to have occurred in the following sequence: (1) compaction, early calcite cementation, and chlorite coating; (2) dissolution, quartz overgrowth, and kaolinite filling pores; (3) late calcite cementation, calcite replacing feldspar, and quartz; and (4) late illite (feldspar illitization). Utilizing fluid inclusion, isotopic analysis of C and O, and burial history, calcite cementation was determined to be related to the thermal decarboxylation of organic matter, showing that the dominant forming-temperature spanned 60°C–100 °C and that a large amount of calcite cement formed before the Middle-Nenjiang stage (the Early Campanian). Illite precipitation was determined to be related to feldspar illitization with a dominant forming temperature spanning 120°C–140 °C. The illite was mainly developed in the Late-Mingshui stage (the Late Campanian) in the DA. In the SS, illite was formed between the Late-Nenjiang stage (the Middle Campanian) and Late-Mingshui stage. The Fuyu reservoir experienced three–four periods of hydrocarbon charging, with the main charging period occurring in the Late Cretaceous (Late-Mingshui stage). The Fuyu reservoir became tight (porosity <12%) in the DA and SS in the Late-Mingshui and Late-Nenjiang stages, respectively. The formation of calcite and illite cementation and the tightening of the Fuyu reservoir occurred before the main hydrocarbon charging period, indicating that tightening occurred before oil accumulation. • Typical diagenetic processes and successive orders of the Fuyu oil reservoir are established. • The reservoir became tight in Daqing Anticline and Sanzhao Sag in Late Mingshui Stage and Late Nenjiang Stage, respectively. • The occurrence of calcite and illite cementation and the tightening of the Fuyu reservoir were before the main hydrocarbon charging period.

Taxonomy and phylogeny of Albian-Maastrichtian planispiral planktonic foraminifera traditionally assigned to Globigerinelloides

We propose a considerably revised taxonomy and phylogeny for Albian-Maastrichtian planispiral planktonic foraminiferal species that have traditionally been included in Globigerinelloides. The revised taxonomy is necessary because of a ~6 m.y. gap between the extinction of planispiral species during the late Aptian and the next younger occurrence of planispiral species in the middle Albian. Our stratophenetic taxonomic groupings utilize ontogenetic morphometric data, shell wall ultrastructure, and general morphologic features observed from Scanning Electron Microscope and X-radiograph images of primary type specimens and globally distributed hypotype specimens. The planispiral lineage Laeviella n. gen., whose type species is La. bentonensis (Morrow), first appeared in the middle Albian and is postulated to have evolved from the evolutionary series Ticinella primula Luterbacher-Laviella primuloides n. sp. Laeviella is characterized as having a smooth to finely pustulose wall texture and a moderate chamber size increase rate. Two additional species, La. tururensis (Bronnimann) and La. bollii (Pessagno), are included in Laeviella with the youngest species of the genus, La. bollii, becoming extinct during the late Campanian. Planohedbergella, with Plh. aspera (Ehrenberg) as its type species, is revised to include 10 species that show a wide variation in chamber arrangement, wall microstructure and test morphology, but all have a moderately to coarsely pustulose wall texture on some or most final whorl chambers. Its stratigraphic range is from the late Albian-Cretaceous/Paleogene boundary. The oldest species is Plh. ultramicra (Subbotina), which evolved from Planomalina pulchella Todd and Low during the late Albian. Planohedbergella circularis n. sp. is described as a new late Campanian-Maastrichtian species representing forms with evolute coiling, a large number of final whorl chambers, and a slow chamber size increase rate. Polycamerella n. gen. is described as a monospecific genus, with Po. tardata n. sp. as the type species. It is a small, biapertural form with a very slow chamber expansion rate and a stratigraphic range from the late Campanian-Maastrichtian. The ancestor of Po. tardata, is tentatively identified as Plh. ultramicra.

MEMBERS OF SOME DIAGNOSTIC SMALL CALCAREOUS LAGENID BENTHIC FORAMINIFERAL GENERA LINGULINA, TRISTIX AND CITHARINA

This study deals with the taxonomy, stratigraphy, and paleogeography of ten Campanian-Paleogene diagnostic calcareous benthic foraminiferal species belong to three lagenid genera which were erected from many localities in the world (North America, Europe and North Africa). These taxa are: Lingulina (L. carinata, L. sliteri), Tristix (T. liasina, T. aubertae, T. sliteri, T. sztrakosae), Citharina (C. strigillata, C. polonica, C. plummerae, C. plumoides). Four of these species, were recorded from three different localities in the world (Mexico, Poland, France, Egypt) are believed to be new: (1) The Late Campanian Lingulina sliteri Anan, n. sp. from Mexico, (2) The Early Maastrichtian Tristix sliteri Anan, n. sp. from Mexico, (3) The Lutetian Tristix sztrakosae Anan, n. sp. from France, and (4) The Danian Citharina polonica Anan, n. sp. from Poland. These taxa show an affinity with Midway-Type Fauna (MTF). The paleogeographic distribution of the recorded species indicate an open connection between the Atlantic and Indo-Pacific Oceans in that time.

Cretaceous biostratigraphy and lithostratigraphy of the Glinzendorf Syncline based on well Gänserndorf UeT3 (Vienna Basin, Austria)

Abstract The 2200 m thick Cretaceous units of well Gänserndorf UeT3 have been biostratigraphically analyzed based on cuttings from 3210 m to 5140 m. The deposits from the Tirolic Glinzendorf Syncline (a part of the buried Northern Calcareous Alps) can be largely correlated with the Lower Gosau Subgroup of the Grünbach Syncline. An exception is the basal unit, which has no equivalent in the Grünbach Syncline. This lower unit is subdivided into a non-marine lower and a largely marine upper part. No age constraints are available for the lower part, whereas the upper part has a possible age range from middle Turonian to Coniacian. For this unit, which is documented for the first time from the Glinzendorf Syncline, we propose Glinzendorf Formation as new lithostratigraphic term. The Glinzendorf Fm. is overlain by the Grünbach Fm., which is intercalated by a thick unit of conglomerates. These are interpreted as equivalents of the Dreistetten Conglomerate Mb. The calcareous nannofossils of these units suggest a latest Santonian to early Campanian age. Non-marine conditions prevailed during deposition of the Grünbach Fm., but marine incursions are indicated for parts of the Dreistetten Conglomerate Mb. The top of the Grünbach Fm. is formed by an about 50-m-thick unit of coal, rich in Characeae oogonia, which, together with the Dreistetten conglomerates serve as marker layer for correlation with the outcrops in the Grünbach Syncline. The Grünbach Fm. is overlain by marls and silty shales of the Piesting Fm. for which a late Campanian and Maastrichtian age is documented. Marine conditions predominated during this interval. The topmost unit in well Gänserndorf UeT3 is overthrusted on the Maastrichtian Piesting Fm. and represents Campanian sandstones and conglomerates of the Grünbach Fm. This Gänserndorf Thrust is detected and biostratigraphically constrained for the first time.

New Taxa of Marine Ostracods (Anticytherideinae, n. subfam.) from the Upper Cretaceous (Campanian and Maastrichtian) of Mississippi, Alabama and Tennessee, U. S. Gulf Coastal Plain

This contribution describes new species, genera and a subfamily (Anticytherideinae) of ostracods from the Upper Cretaceous (mid-late Campanian-Maastrichtian) marine deposits of the eastern flank of the Mississippi Embayment. New taxa assigned to the subfamily include Anticythereis dorsennus and A. slipperi; the new genus Asculdoracythereis, which includes the new species As. asculdora, As. invicta, and As. pseudoalabamensis; the new genus Frodocythereis, which includes the new species F. frodoi; the new genus Laevipellacythereis, which includes the new species L. colossus and L. laevipellis; and the new genus Tumulocythereis, which includes the new species T. incompta, T. tiberti, and T. tumulus. Previously described species assigned to the genus Anticythereis are re-evaluated, some of which are assigned to one of the new genera. Synapomorphic characters of the new subfamily include a combination of pronounced external post-ocular sulcus with corresponding pair of internal, rimmed inverted platforms and a distinctive "yin-yang" adductor muscle scar pattern. The taxa display remarkably rapid evolution. The earliest species (Anticythereis sp. 1) occurs in the planktonic foraminiferal Radotruncana calcarata Taxon Range Zone of mid- to late Campanian age and by the end of the Maastrichtian there are more than 20 species. Most species have very localized occurrences, including several that occur only at a single outcrop. Although species are found on the eastern flank of the Mississippi Embayment and the Atlantic Coastal Plain, none have been observed on the western flank of the Mississippi Embayment. Species have been assigned to the genus Anticythereis from other continents (South America, Europe and Africa), but those taxa lack distinctive features of the Anticytherideinae, which is endemic to North America. The group became extinct at the Cretaceous-Paleogene boundary.

Integrated biostratigraphy for the Santonian/Campanian boundary interval, the Kurdistan Region, northeast Iraq

The first high-resolution integrated biostratigraphic study for Santonian/Campanian sediments of the Tabin section in the Kurdistan Region, northeast Iraq is provided. The study, based on 28 closely spaced samples, combines data from planktic foraminifers (25 species), calcareous nannofossils (32 species) and two ammonite genera in the Kometan Formation, marking the Santonian/Campanian boundary (S/C boundary) in the Kurdistan Region. In the absence of the crinoid Marsupites testudinarius, the proposed boundary marker, secondary markers such as calcareous nannofossils, planktic foraminifers and ammonites, have been used to establish a multi-stratigraphic biozonation for the late Santonian–early Campanian duration. Based on the occurrences of calcareous nannofossils, three biozones are identified — Lucianorhabdus cayeuxii (late Santonian), Calculites obscurus (latest Santonian–earliest Campanian), and Broinsonia parca parca (early Campanian). Seven calcareous nannofossil bioevents and three planktic foraminiferal bioevents are also identified. The Santonian/Campanian boundary is marked by: (a) the LO (Last Occurrence) of the planktic foraminifera D. asymetrica, (b) the FOs (First Occurrence) of the calcareous nannofossil species B. parca parca and B. parca constricta, (c) the extinction of several planktic foraminiferal species of Dicarinella and Marginotruncana, (d) the abundance and diversification of the planktic foraminifera genera, Globotruncana and Globotruncanita at the beginning of the Campanian, and (e) the disappearance of the ammonite genus Texanites, 0.5 m below (i.e., at 19 m) the disappearance of all Dicarinella and Marginotruncana species in the study section. Similar to several other Tethyan sections, the FO of B. parca parca is above the LOs of D. concavata and D. asymetrica; the LO of D. asymetrica is used here to mark the S/C boundary

Ammonites and Foraminifera of Shiranish Formation (Late Campanian-Maastrichtian) from Sulaimaniya and Erbil Governorates, Northern Iraq

This study deals with the biostratigraphy of Shiranish Formation (Late Cretaceous), depending on the Ammonite and associated Foraminifera in four outcrop sections, three of which are located in Al-Sulaimaniya governorate (Dokan, Esewa and Kanny dirka sections) and one in Erbil governorate, northern Iraq (Hijran section). Fourteen species of Ammonite belonging to fourteen genera were determined, which are: Dsemoceratidae, Gaudryceras, Gunnarites, Hoplitoplacenticeras, Kitchinites, Kossmaticeratinae, Neancyloceras, Neokossmaticeras, Nostoceras, Paratexanites, Partschiceras, Phylloceras, Pseudophyllites and Yubariceras. Also, thirty- five species of Foraminifera belonging to thirteen genera were determined, which are: Cibicides, Cymopolia, Eggellina, Elphidium, Globigerinelloides, Globotruncana, Hedbergella, Heterohelix, Marginulina, Miliolid, Neobulimmina, Nodosaria and Textularia. Seven range zones were determined, three of which are of Ammonite, which are: Desmophyllites larteti (Seunes, 1892), Nostoceras (Nostoceras) hyatti and Pseudophyllites teres (Van Hoepen, 1920), whereas the others are of Foraminifera species, which are: Glt. gagnebini Tilev, Glt. tricarinata lapparenti Brotzen, Glt. tricarinata tricarinata (Querean) and Glt. Stuartiformis Dalbiez. According to these findings, the age of Shiranish Formation was determined as the Late Campanian- Maastrichtian.

Taphonomic attributes of the holotype of the lambeosaurine dinosaur Latirhinus uitstlani from the late Campanian of Mexico: Implications for its phylogenetic systematics

Latirhinus uistlani represents one of the most emblematic dinosaurs from Mexico. This hadrosaurid, originally described as a member of the Saurolophinae by Prieto-Márquez and Serrano-Brañas in 2012, was re-evaluated as a lambeosaurine by Ramírez-Velasco et al. (2021). In addition, these authors stated that the description of the 2012 holotype was based on a chimeric skeleton and designated a new holotype (a different concept for the composition of essentially the same individual). The composition of their 2021 holotype was based on the size, association and similar mode of preservation of the bones within the quarry. Notably, no details were provided regarding such mode of preservation. However, the fact that the type locality of L. uitstlani is an attritional bonebed where other similar-sized individuals were also present calls into question the criteria used by Ramírez-Velasco et al. (2021) in the composition of their holotype. We address this shortcoming by describing the taphonomic signature of the skeletal elements in the L. uitstlani holotype of Ramírez-Velasco et al. (2021), as well as that of other bones discussed collected from this species’ type locality and other sites of the late Campanian Cerro del Pueblo Formation. Our observations show different taphonomic attributes among the bones of the 2021 holotype, indicating that it is likely a chimera of different specimens. Such taphonomic attributes support a holotype for L. uitstlani consisting of the original elements listed in Prieto-Márquez and Serrano-Brañas (2012), with exclusion of the IGM 12712 jugal and a right scapula. We concur in that IGM 12712 is actually a fragmentary jugal, which represents an unusually large hadrosaurid specimen. We also tested the referral of L. uitstlani to Lambeosaurinae via a cladistic parsimony analysis that confirmed that this specimen belongs to that major clade of hadrosaurids; however, its relationships with other lambeosaurines remain unresolved. Finally, we re-evaluated the diagnostic utility of the characters used by Ramírez-Velasco et al. (2021) for referring other specimens to different hadrosaurid clades, concluding that several of them can only be referred to Hadrosauridae indeterminate.

Stratigraphy and origin of Upper Cretaceous wedge-top and proximal foredeep deposits in the Mexican foreland basin, east-central Mexico

Upper Campanian (?) to lower Maastrichtian strata exposed in the Mexican fold and thrust belt east and south of Cárdenas, San Luis Potosí (SLP), record an abrupt transition from marine foredeep sedimentation to continental deposition on the frontal part of the orogenic wedge. Shale and subordinate fine-grained sandstone of the middle Campanian–Maastrichtian Méndez Formation east of Cárdenas represent medial and distal foredeep deposits of the Mexican foreland basin. Correlative proximal deposits of the Cárdenas Formation near the village of Cárdenas consist of thick shale and fine-grained sandstone turbidite beds intercalated with thickly-bedded breccias composed of transported rudists, and other pelecypods and corals in a mudstone matrix. The fossiliferous beds are interpreted as bioclastic debris-flow deposits that accumulated in deep water of the proximal foredeep and/or wedge-top depozone. The overlying Tabaco Formation consists of conglomerate and lenticular sandstone beds as much 1.6 m thick interbedded with red shale and bioturbated, cross-stratified sandstone beds, representing deposition in fluvial channels and floodplains in a rapidly uplifted wedge-top basin.Maximum depositional age (MDA) values calculated from young grains (n = 3 grains) of the Upper Cretaceous strata yield somewhat older ages than those derived from published and new biostratigraphy data. A sandstone sample from the Méndez Formation yielded an MDA of 73.3 ± 7.5 Ma, imprecise but consistent with a middle to late Campanian biostratigraphic age reported here from an associated Méndez shale sample. Two sandstone samples from the middle part of the Cardenas Formation yielded MDAs ranging from 73.4 ± 1.5 Ma to 72.9 ± 3.7 Ma, slightly older than a reported early Maastrichtian biostratigraphic age based on ammonites and corals, but consistent with a new age range, based on nannofossils, of middle Campanian-early Maastrichtian for strata consisting of mixed Méndez and Cárdenas lithofacies. Five sandstones of the Tabaco Formation yielded an MDA range of 73.9–67.9 Ma (Campanian–Maastrichtian), but with substantial 2σ errors of 3–5 my.Sandstone petrography and detrital zircon U -Pb geochronology indicate that sediment sources were Upper Cretaceous sedimentary strata exposed in the Mesa Central and the frontal part of the Mexican fold-and-thrust belt. Cárdenas and Tabaco sandstones contain dominant extrabasinal carbonate lithic grains, reflecting progressive uplift and significant erosion of Lower Cretaceous platformal carbonate and pre-Campanian foreland basin strata, coupled with a decrease in the magmatic activity of the Mexican Cordilleran arc. We propose that the Cárdenas Formation, formerly interpreted as a carbonate platform deposit on the basis of its abundant coral content, was deposited by sediment-gravity flows sourced from nearby reefal facies that likely developed on growing folds. Deposition of the Cárdenas Formation took place in the proximal foredeep or a wedge-top basin on the frontal part of the fold-thrust belt. Coeval deposition of the Méndez Formation took place in the proximal foredeep. Continental deposits of the Tabaco Formation, which overlies the Cárdenas Formation, record an abrupt shift to continental deposition concomitant with a transition to dominantly thrust-belt sediment sources. The transition in facies and sandstone composition record shoaling of the wedge-top basin during emergence of a frontal thrust sheet. Upper Campanian-lower Maastrichtian strata therefore provide important insight on temporal and topographic evolution of the Mexican orogen in east-central Mexico.

Nature, timing and magnitude of buried Late Cretaceous magmatism on the central West Iberian Margin

AbstractThe magma‐poor West Iberian Margin (WIM), as part of the Peri‐Atlantic alkaline province, records multiple evidence for intra‐plate post‐rift magmatism. Based on high‐resolution multichannel seismic data, this work discusses the presence of large volcanic and intrusive features in the Estremadura Spur, providing evidence for important magmatic activity during the drifting of the continental margin. Our observations reveal distinct voluminous fissure‐fed effusive sequences and the details of the 2800 m‐high Fontanelas compound volcano, including its external and internal architecture, secondary vents and associated lava flows, all of which were probably extruded at intermediate water depths. Numerous and morphologically diverse sills and sill complexes are also described, attesting to the presence of a Late Cretaceous shallow magmatic plumbing system in the area. Magmatism in this region is interpreted as having occurred during two main pulses and types of activity: (1) Coniacian to lower Campanian(?) age, characterised by fissural and fault‐controlled volcanism, which mostly extruded massive lobate/sheet lava flows; and (2) a second voluminous intrusive and extrusive event of mid to late Campanian age, which includes the intrusion of the Estremadura Spur laccolith and the prominent Fontanelas compound volcano with associated dendritic lava flows. The inferred volumes of the first fissure‐fed effusive event suggest a large eruption magnitude, comparable to some of the largest historical effusive eruptions. The second magmatic pulse led to the emplacement of discrete clusters of sills and sill complexes, as well as the construction of the ca. 2.8‐km‐high Fontanelas volcano, suggesting a syn‐rift structural inheritance that controlled the location of the Estremadura Spur Intrusion and the Fontanelas volcanic area. Altogether, a total volume of rock exceeding 1.452 km3 is estimated to have been emplaced or extruded in this region in a relatively short period, attesting to the prominence of the magmatism in this sector of the WIM.

Paleoenvironment of the Late Cretaceous (Late Touronian–Early Campanian) Ostarcoda in the Kometan Formation, Dokan Area, Kurdistan region, NE-Iraq

In the present study, selected the Kometan Formation (Late Turonian - Early Campanian) from the Dokan area, NE-Iraq. In this formation studied Ostracoda and identified fifteen open Ostracoda species belonging to ten genera (Bairdia, Bairdiacypris, Bythocypris, Bairdoppilata, Cavellina, Cypridina, Cytherella, Haplocytheridea, Pterygocythereis, and Paracypris). The goal of the present study is to identify Ostracoda species under polarizing microscopes for the first time in the Kometan Formation in the Dokan area. The Ostracoda assemblage such as Bairdia, Bairdiacypris, Cytherella, Cypridina, and Paracypris with foraminifera species Globotruncana linneiana, Globotruncanita stuartiformis, Marginotruncana schneeansi, and Dicarinella asymetrica indicate the Kometan Formation deposited in the deep marine environment.