Albian Cenomanian Research Articles

Albian–Cenomanian Orogenic Belt and Igneous Province of Pacific Asia

Geological data and about 300 precision geochronological and geochemical determinations are analyzed to identify the Albian–Cenomanian continental-margin orogenic belt and simultaneous igneous province of Pacific Asia. The orogenic belt represents a newly formed region of continental lithosphere that resulted from the deformation of mainly Jurassic–Early Cretaceous epioceanic terranes. The igneous province is made up of volcanic and intrusive complexes of mostly Albian age, which are syn-orogenic within the belt and post-orogenic beyond it. The igneous rocks include A-, I-, and S-type granitoids; adakites; and VAB- and OIB-type basalts and their intrusive analogues. Both the orogenic belt and the igneous province were formed in a tectonic setting of a transform continental margin between 110 and 95 Ma. The interval of 103–97 Ma became the peak of orogenic and magmatic activity caused by upwelling of the hot asthenospheric mantle through destructed stagnant slabs of the pre-Albian subduction. The Albian–Cenomanian age of the large gold, copper, tungsten, tin, and other ore deposits argues in favor of recognition of the corresponding metallogenic province. The first age data (100–97 Ma) are reported for the granite from the Malmyzh deposit within the Sikhote-Alin Ridge.

Chronostratigraphic Revision of the Cloverly Formation (Lower Cretaceous, Western Interior, USA)

The Cloverly Formation is an important geologic unit for understanding the development of North American terrestrial landscapes and ecosystems, but the age of this unit is poorly constrained. We report U–Pb radiometric dates determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and chemical abrasion thermal ionization mass spectrometry (CA-TIMS) from euhedral zircons derived from fluvial sandstone and bentonitic claystone. We reanalyzed published biostratigraphic, paleomagnetic, and radiometric datasets, which have generally disregarded younger (late Albian–Cenomanian) ages for the formation. New data reported in this study suggest that deposition of the Cloverly Formation spanned the Valanginian–Cenomanian stages (ca. 140 Ma–98 Ma), a longer time interval than the commonly cited Aptian–Albian depositional timeframe. The lowest member of the Cloverly Formation, the Pryor Conglomerate, was deposited ca. 140–130 Ma in response to the onset of the Sevier Orogeny shedding sediment from the west. The overlying Little Sheep Mudstone Member was deposited ca. 124–109 Ma in a time of low sediment supply. In the mid–late Albian to early Cenomanian (ca. 109–98 Ma), sediment sourced from the east was deposited as the Himes Member and Greybull Sandstone. Following this, the Sykes Mountain Formation began nearshore deposition as the Western Interior Seaway transgressed from the north. Our revised chronostratigraphic framework for the Cloverly Formation is congruent with tectonic subsidence analysis showing a rapid increase in accommodation space in the mid-Albian. We hypothesize that more intensive sampling may yield multiple fossil assemblages within the formation, paralleling its correlates to the south. Furthermore, we hypothesize that some poorly represented taxa will be synonymized with taxa from those same units now that their temporal equivalence has been demonstrated.

Meliatic blueschists and their detritus in Cretaceous sediments: new data constraining tectonic evolution of the West Carpathians

The Western Carpathian Meliata Superunit (Meliaticum) includes a heterogeneous group of units—the blueschist-facies Borka Nappe and the very low-grade chaotic complexes—polygenous melange containing material derived from various tectonic settings (Jaklovce Unit) and Jurassic oceanic sediments with olistostrome bodies (Meliata Unit s.s.). The high pressure/low temperature (HP/LT) metamorphism, development of tectonic melanges and synorogenic sediments took place simultaneously during the Middle–Late Jurassic in connection with closing of the Meliata Ocean. We present some new data concerning composition of variegated melanges related to the subduction–accretion processes of the Meliata Ocean and its continental margins. The polygenous melange contains a mixture of fragments of HP/LT up to unmetamorphosed sedimentary and volcanic rocks, including blueschist-facies radiolarites. New electron microprobe chemical age data of monazites from metasediments of the Borka Nappe cluster in two peaks—earliest Cretaceous ages are interpreted in terms of post-exhumation, renewed burial during formation of the Meliatic accretionary wedge. The mid-Cretaceous ages might record the thermal relaxation during the thick-skinned nappe stacking and exhumation of the neighbouring Veporic metamorphic dome. In addition, we describe two distinct types of tourmalines and epidotes occurring in the Borka blueschists that document the prograde HP and retrograde LP metamorphic events. Detritus of the blueschist-facies rocks appears for the first time in the heavy mineral spectra of the Barremian–Aptian platform limestones. These limestones occur as clasts, together with glaucophanite pebbles, in the Albian–Cenomanian flysch formations of the Pieniny Klippen Belt (Klape Unit). We also review occurrences of other blueschist and ophiolitic erosional products in Cretaceous clastic formations and suggest that all have a Meliatic provenance.

Leaf and inflorescence evidence for near-basal Araceae and an unexpected diversity of other monocots from the late Early Cretaceous of Spain

Phylogenetic analyses imply that monocots were a key group in the early radiation of angiosperms, yet they are much rarer than other major clades in the Early Cretaceous macrofossil record. Here we describe a well-preserved leaf and several inflorescences related to the near-basal monocot family Araceae and abundant monocot leaves of uncertain affinities from two latest Albian localities in north-eastern Spain. Orontiophyllum ferreri sp. nov. has a multistranded midrib, several orders of parallel-pinnate veins, two orders of transverse veins, and paracytic-oblique stomata. This suite of characters (but with both anomocytic and paracytic-oblique stomata) is characteristic today of Orontium in the near-basal araceous subfamily Orontioideae, and later Cretaceous and early Cenozoic leaves assigned to Orontiophyllum have similar architecture. Sedimentology and anatomy suggest a (semi)aquatic ecology. Other monocot leaves at the same locality are linear and parallel-veined but have similar stomata. Although anomocytic stomata have been proposed as ancestral in monocots, O. ferreri, the associated linear leaves, Albian–Cenomanian cuticles from Australia and Portugal, and extant data are consistent with the hypothesis that variable paracytic-oblique stomata are ancestral. Turolospadix bogneri gen. et sp. nov., from the other locality, includes spadices of ebracteate flowers with four tepals, a central gynoecium, and a long stipe (vs a spathe attached just below the fertile zone as in most Araceae). Phylogenetic analyses indicate that the character combinations seen in O. ferreri and T. bogneri are ancestral for Araceae, and they could be either sister to Araceae or nested within a basal grade of the family. Together with fossils from the Aptian–Albian of Brazil and Portugal, the Spanish fossils indicate that Araceae are among the oldest extant monocot families, but they were associated with diverse linear-leaved monocots of uncertain affinities.

Microstructural overlap of Macroelongatoolithus eggs from Asia and North America expands the occurrence of colossal oviraptorosaurs

ABSTRACTThe first intact North American Macroelongatoolithus specimen was excavated from sediments in the Wayan Formation of southeastern Idaho and initially reported by Krumenacker et al. (2017, Historical Biology 29:170–186). Here, we present a description of the specimen, including a zonal analysis of microstructural variation and comparison with an egg pair from the Liangtoutang Formation of Zhejiang, China. We assign egg pair IMNH 2428\\49608 from the Albian–Cenomanian Wayan Formation of Idaho and egg pair ZMNH M8705 from the Liangtoutang Formation of China to the oospecies Macroelongatoolithus carlylei. The eggs are 39.8–41.7 cm long and 10.8–14.3 cm wide, and the eggshell consists of two structural layers of calcite demarcated by a distinct, undulating boundary. Eggshell thickness is 1.01–2.17 mm, and the continuous layer to mammillary layer ratio (CL:ML) ranges from 2.05:1 to 7.68:1. Identification of intact Macroelongatoolithus specimens from North America supports synonymy of M. xixiaensis with M. carlylei, as proposed by Zelenitsky et al. (2002) on the basis of eggshell fragments. Due to the substantial microstructural variation of the specimens reported here, we also regard M. goseongensis and M. qiongensis as junior synonyms of M. carlylei. The degree of microstructural variation within the new specimens expands the expected range of variation typically used in diagnosing oospecies and has implications for the naming of new oospecies on the basis of fragments or egg portions alone. The discovery of Macroelongatoolithus eggs from the latest Early Cretaceous of Idaho confirms the presence of this extraordinary oogenus outside of Asia and provides nonskeletal evidence of a Gigantoraptor-sized oviraptorosaur in western North America.

The Early Aptian volcanic episode of Gutiolo (N Spain): Expression of the Bilbao Rift Fault Zone

The Gutiolo volcanic unit belongs to the Aptian Bilbao Formation and crops out 6 km SE of Bilbao (N Spain) within marine marlstones. It is 300 m thick and up to 1 km long. The volcanics consist of lava in the lower part and volcaniclastic sediments above, with metatrachytes and metatrachybasalts, similar to others of the alkali Cretaceous sequence in the Basque–Cantabrian Basin. The palaeontological age is top early Aptian (Dufrenoyia furcata Zone) near the Bedoulian–Gargasian substage transition, and the isotopic age (K–Ar) is 123 ± 3 Ma but most probably, 122 Ma. E–W and N–S trending faults bounding the Gutiolo volcanics controlled magma eruption. Other NW‐ and SE‐oriented major faults in the Bilbao area favoured several Valanginian to Santonian eruptions including Gutiolo. The eruptions moved progressively in space and time from SW to NE. These faults make up a 15‐km‐wide tectonic belt, the magma‐leaky Bilbao Fault Zone. A similar magmatic fault zone NE of Bilbao, Gernika‐Elgoibar, poured magma onto the sea floor during the late Albian–Cenomanian up to the Santonian, continuing the north‐easterly younging trend of volcanic inceptions recognized in Bilbao. All this Cretaceous volcanism is related to the Bay of Biscay opening processes, and the Gutiolo event is correlated with the first appearance of oceanic crust in the Bay of Biscay. From stratigraphic, volcanic, geochemical, and mineralization evidence, we attribute Gutiolo to an early phase of mafic intrusion emplacement in the Bilbao area, underplated by magmatism during the Valanginian to Santonian (Cretaceous). Volcanic hydrothermal fluids associated to the Gutiolo event are considered responsible for metallic ore emplacement in the Basque–Cantabrian Basin during the early Aptian.

An overview of ichthyosaurian remains from the Cretaceous of Texas, USA

The clade nominal Ophthalmosauridae encompasses all currently recognized ichthyosaurian taxa from the mid-Cretaceous (Albian–Cenomanian) time interval in North America. These would have inhabited what is today known as the Western Interior Seaway. The remains represent mid to large-sized (up to around 5 m in maximum body length) ichthyosaurians that are mainly based upon isolated teeth and vertebrae, although some partial skeletons have been recovered from both the USA and Canada. Most of these fossils have taxonomic affinities with platypterygiines, such as the ubiquitous ‘form genus’ Platypterygius. This taxon has historically been the default identification for most North American Cretaceous ichthyosaur specimens. However, in comparison with remains from elsewhere, the ichthyosaurian fossils from Texas have been relatively understudied. Here, I review the existing records and present a concise list of all Cretaceous ichthyosaurian material currently held in public museum collections across the state. I have recognized 11 Cretaceous ichthyosaurian occurrences from Texas, including an indeterminate tooth, numerous vertebral centra, and some fragmentary skeletal remains attributable to Platypterygius. Ichthyosaurians therefore demonstrably occupied the Cretaceous epeiric seas of Texas from at least the Albian to middle Cenomanian, a distribution that traverses both the western and eastern coastlines of the Western Interior Seaway during its early phase of southern epicontinental incursion.

The palaeoenvironment of the Upper Cretaceous (Cenomanian-Turonian) portion of the Winton Formation, Queensland, Australia.

The Winton Formation is increasingly recognised as an important source of information about the Cretaceous of Australia, and, more broadly, the palaeobiogeographic history of eastern Gondwana. With more precise dating and stratigraphic controls starting to provide temporal context to the geological and palaeontological understanding of this formation, it is timely to reassess the palaeoenvironment in which it was deposited. This new understanding helps to further differentiate the upper, most-studied portion of the formation (Cenomanian–Turonian) from the lower portions (Albian–Cenomanian), allowing a coherent picture of the ecosystem to emerge. Temperatures during the deposition of the Upper Cretaceous portion of the Winton Formation were warm, with high, seasonal rainfall, but not as extreme as the modern monsoon. The landscape was heterogeneous, a freshwater alluvial plain bestrode by low energy, meandering rivers, minor lakes and mires. Infrequent, scouring flood events were part of a multi-year cycle of drier and wetter years. The heavily vegetated flood plains supported abundant large herbivores. This was the final infilling of the great Eromanga Basin.

Mid-Cretaceous paleoenvironmental changes in the western Tethys

Abstract. We present a continuous record of surface water temperature and fertility variations through the latest Barremian–Cenomanian interval (ca. 27 Myr) based on calcareous nannofossil abundances from the western Tethys. The nannofossil temperature index, calibrated with TEX86 sea surface temperatures, suggests that warmest (34–36 ∘C) conditions were reached during oceanic anoxic event (OAE) 1a onset, the Aptian–Albian boundary interval hyperthermals (113, Kilian level and Urbino level OAE 1b) and during a ca. 4 Myr long phase in the middle Albian. Coolest temperatures (29 ∘C) correspond instead to the late Aptian. Generally warm conditions characterized the Albian followed by a progressive cooling trend that started in the latest Albian (at the Marne a Fucoidi–Scaglia Bianca Formation transition). Temperate conditions occurred in the Cenomanian with frequent short-term variations highlighted by abundance peaks of the cold-water nannofossil species E. floralis and R. parvidentatum. Mid-Cretaceous surface water fertility was rather fluctuating and mostly independent from climatic conditions as well as from black shales intervals. Intense warming and fertility spikes were systematically associated only with black shales of OAE 1a and of the Aptian–Albian boundary hyperthermals. The Albian–Cenomanian rhythmic black shales are, in fact, associated with varying long-term climatic and fertility conditions. The similarity of western Tethys climatic and fertility fluctuations during OAE 1a, OAE 1b, the middle Albian and OAE 1d with nannofossil-based records from other basins indicated that these paleoenvironmental conditions were affecting the oceans at supra-regional to global scale.

A Cretaceous sporomorph palynozonation and the palaeobiogeography of northern Egypt

ABSTRACTThe multiple biozonal nomenclatures given for the same time segment at different locations in northern Egypt are problematic, as such multiplicity is highly confusing and considerably limits the correlative value of these nomenclatures within the Egyptian territory, in the Elaterates phytogeoprovince and in the Tethyan Realm. Thirty-one wells are selected and used in this work to establish a standard and unified, semi-formal, generalised Egyptian sporomorph palynozonation scheme for northern Egypt. Marker taxa are carefully picked and tracked from the different previously established palynostratigraphies, and they are methodically re-used in the present unified framework on a regular basis, where their first down-hole appearance [last appearance datum (LAD)] palynoevents are utilised to erect a regional palynostratigraphical scheme. Ten sporomorph interval zones (IZ) and two subzones are reconstructed, established and palynologically specified from all of the studied wells. The authors surveyed the palynofloral assemblages characterising different areas of the world in order to derive meaningful palaeobiogeographical implications. Connecting these databases furnishes a comprehensive palynostratigraphical framework for inter-continental correlations with the Egyptian assemblages. In addition, such correlations confirm the dating acquired from the recovered palynological markers and assemblages presented in the current review. Comparisons of coeval assemblages confirm that the extensions and boundary limits of the palaeoprovinces of the recorded sporomorphs exhibited a gradual change and that their areal extent evolved with time. Due to the wide geographical occurrences of the recorded marker taxa during the pre-Albian stages of North and West Africa, western Atlantic and east South America, the proposed sporomorph zones can be confidently applied in these areas. During the Albian–Cenomanian such correlations can be applied only between North and West Africa and east South America.

Changes in CO2 during Ocean Anoxic Event 1d indicate similarities to other carbon cycle perturbations

Past greenhouse intervals of the Mesozoic were repeatedly punctuated by Ocean Anoxic Events (OAEs), major perturbations to the global carbon cycle and abrupt climate changes that may serve as relevant analogs for Earth's greenhouse gas-forced climate future. The key to better understanding these transient climate disruptions and possible CO2-forced tipping-points resides in high-resolution, precise, and accurate estimates of atmospheric CO2 for individual OAEs. Here we present a high-temporal resolution, multi-proxy pCO2 reconstruction for the onset of mid-Cretaceous (Albian–Cenomanian Boundary) OAE1d. Coupling of pCO2 estimates with carbon isotopic compositions (δ13C) of charcoal, vitrain, and cuticle from the Rose Creek Pit (RCP), Nebraska, reveals complex phasing, including a lag between the well-documented negative δ13C excursion defining the onset of OAE1d and the CO2 increase. This lag indicates that increased CO2 or other C-based greenhouse gases may not have been the primary cause of the negative excursion. Our study reveals a pCO2 increase within the interval of the negative δ13C excursion, reaching a maximum of up to ∼840 ppm (95% confidence interval −307 ppm/+167 ppm) toward its end. The reconstructed magnitude of CO2 increase (∼357 ppm) is similar to that of Late Cretaceous OAE2 but of smaller magnitude than that of other major carbon cycle perturbations of the Mesozoic assessed via stomatal methods (e.g., the Toarcian OAE [TOAE], Triassic–Jurassic boundary event, Cretaceous–Paleogene Boundary event). Furthermore, our results indicate a possible shared causal or developmental mechanism with OAE1a and the TOAE.

The most basal ankylosaurine dinosaur from the Albian\u2013Cenomanian of China, with implications for the evolution of the tail club

The tail club knob is a highly specialized structure thought to characterize a subgroup of the ankylosaurine ankylosaurians, and the oldest documented tail club knob in the fossil record occurred in the Campanian ankylosaurine Pinacosaurus. Here we report a new ankylosaurid Jinyunpelta sinensis, gen. et sp. nov., from the Albian–Cenomanian Liangtoutang Formation, Jinyun County, Zhejiang, China. This is the first definitive and the best preserved ankylosaurid dinosaur ever found in southern China. Jinyunpelta possesses unique cranial features differs from other ankylosaurs including two paranasal apertures level with and posterior to the external naris, a triangular fossa on the anterodorsal edge of the maxilla, an antorbital fossa in the junction between the maxilla, lacrimal and jugal, and an anterior process of the prearticular that lies ventral to the splenial. Our phylogenetic analysis suggests Jinyunpelta as the most basal ankylosaurine dinosaur. Jinyunpelta has a tail club with interlocking caudal vertebrae and a well-developed tail club knob, it represents the oldest and the most basal ankylosaurian known to have a well-developed tail club knob. The new discovery thus demonstrates that a large and highly modified tail club evolved at the base of the ankylosaurine ankylosaurs at least about 100 million years ago.

Syn-sedimentary tectonics and facies analysis in a rift setting: Cretaceous Dalmiapuram Formation, Cauvery Basin, SE India

The Cretaceous (Albian–Cenomanian) Dalmiapuram Formation is one of the economically significant constituents in the hydrocarbon-producing Cauvery rift basin, SE India that opened up during the Late Jurassic–Early Cretaceous Gondwanaland fragmentation. The fossil-rich Dalmiapuram Formation, exposed at Ariyalur within the Pondicherry sub-basin of Cauvery Basin, rests in most places directly on the Archean basement and locally on the Lower Cretaceous (Barremian–Aptian) Basal Siliciclastic Formation. In the Dalmiapuram Formation, a facies association of tectonically-disturbed phase is sandwiched between two drastically quieter phases. The early syn-rift facies association (FA 1), records the first carbonate marine transgression within the basin, comprising a bar–lagoon system with occasionally storms affecting along the shore and a sheet-like non-recurrent biomicritic limestone bed on the shallow shelf that laterally grades into pyrite–glauconite-bearing dark-colored shale in the deeper shelf. Spectacular breccias together with varied kinds of mass-flow products comprise the syn-rift facies association (FA 2). While the breccias occur at the basin margin area, the latter extend in the deeper inland sea. Clast composition of the coarse clastics includes large, even block-sized limestone fragments and small fragments of granite and sandstone from the basement. Marl beds of quieter intervals between tectonic pulses occur in alternation with them. Faulted basal contact of the formation, and small grabens filled by multiple mass-flow packages bear the clear signature of the syntectonic activity localized contortions, slump folds, and pillow beds associated with mega slump/slide planes and joints, which corroborates this contention further. This phase of tectonic intervention is followed by another relatively quieter phase and accommodates the late syn-rift facies association (FA 3). A tidal bar–interbar shelf depositional system allowed a transgressive systems tract motif to grow eventually passing upwards into the Karai Shale Formation, whose contact with the Dalmiapuram Formation is gradational.

A New Titanosaurian (Sauropoda, Dinosauria) Osteoderm from the Cretaceous of Brazil and its Significance

Titanosauria is a clade of sauropod dinosaurs that includes some of the largest terrestrial animals ever recorded. An outstanding feature of some species of this group is the presence of osteoderms, which are bony deposits on the skin that form scales, plates or other structures. Only six osteoderms have been identified from Brazil. Herein, we describe the first titanosaurian osteoderm from the Potiguar Basin (Early–Late Cretaceous) and discuss Brazilian titanosaur osteoderm diversity, their taxonomy and the functional implications. The specimen (UFRJ-DG 549-R) is bilaterally symmetrical and is assigned to the ellipsoid morphotype. The most interesting feature is the large cavities separated by thin trabeculae. This pattern, according to recent interpretations, suggests that titanosaur osteoderms functioned as a source of calcium. However, the function(s) of titanosaur osteoderms remain(s) open to debate. Compared with the other reported osteoderms from Brazil, the Potiguar osteoderm shows more similarities with an osteoderm of Ibira (Bauru Group, Turonian–Santonian) than with material collected from the Sao Luis Basin (Albian–Cenomanian) despite their greater geographical and temporal proximity. The Potiguar and Ibira osteoderms are of the ellipsoid morphotype, with no cingulum and several pits on the external surface. More findings are necessary to clarify whether the Potiguar material represents a different armored titanosaurian species in northeastern Brazil.

Isolated pliosaurid teeth from the Albian–Cenomanian (Cretaceous) of Annopol, Poland

AbstractBrachauchenine pliosaurids were a cosmopolitan clade of macropredatory plesiosaurs that are considered to represent the only pliosaurid lineage that survived the faunal turnover of marine amniotes during the Jurassic- Cretaceous transition. However, the European record of the Early to early Late Cretaceous brachauchenines is largely limited to isolated tooth crowns, most of which have been attributed to the classic Cretaceous taxon Polyptychodon. Nevertheless, the original material of P. interruptus, the type species of Polyptychodon, was recently reappraised and found undiagnostic. Here, we describe a collection of twelve pliosaurid teeth from the upper Albian-middle Cenomanian interval of the condensed, phosphorite-bearing Cretaceous succession at Annopol, Poland. Eleven of the studied tooth crowns, from the Albian and Cenomanian strata, fall within the range of the morphological variability observed in the original material of P. interruptus from the Cretaceous of England. One tooth crown from the middle Cenomanian is characterized by a gently subtrihedral cross-section. Similar morphology has so far been described only for pliosaurid teeth from the Late Jurassic and Early Cretaceous. Even though it remains impossible to precisely settle the taxonomic distinctions, the studied material is considered to be taxonomically heterogeneous.

The Cretaceous conglomerates from Piatra Craiului syncline (South Carpathians, Romania): searching for the source area

The study of conglomerate-type deposits represents a valuable tool that may be used on a large scale to reconstruct the stratigraphic record of the adjacent regions. In order to identify the source area, the first step is to analyze the lithology of the pebbles. The Gura Râului Aptian conglomerates and the Upper Albian–Cenomanian conglomerates are forming the siliciclastic infill of the Piatra Craiului Syncline unit. This study aims to identify the source area by using various analytical techniques such as lithological description, morphometric measurements, and determination of paleocurrents. The carbonate pebbles from these deposits contain various types of microfacies and microfossils, which indicate a Middle Jurassic to Early Cretaceous (Barremian–Early Aptian) age. Other clasts include Callovian–Oxfordian siliceous pebbles and metamorphic fragments from the Cumpăna and Leaota groups. The analysis suggests that the Aptian conglomerates were sourced from the adjacent units located in the northern–northwestern part of the Piatra Craiului Massif. They consist of autochthonous carbonate sediments, which are surrounded by metamorphic rocks. A possible scenario is that the erosion of the carbonate succession from the surrounding areas continued until the end of the Early Cretaceous. The source area of the uppermost Albian–Cenomanian conglomerates also coincides with the carbonate succession from the Piatra Craiului Massif. A first argument in favor of this hypothesis is represented by the microfacies and microfossil associations hosted within the carbonate pebbles of this siliciclastic unit. They show similarities with assemblages described by different authors from the Kimmeridgian–Lower Valanginian succession of the Piatra Craiului Massif.

Palynofloral evolution on the northern margin of the Indian Plate, southern Xizang, China during the Cretaceous Period and its phytogeographic significance

During the Cretaceous Period, the Indian Plate separated from Gondwana and drifted northwards, eventually colliding with Eurasia at the end of the period or in the early Cenozoic. This led to major changes in the composition of the flora and fauna of the region. Palynomorph assemblages from Cretaceous deposits in Gamba County, southern Xizang (Tibet), China, are analyzed herein in an attempt to determine how the vegetation of the northern margin of the Indian Plate changed. The Gamba assemblages were initially similar in composition to those from Australia but by the Santonian Stage they were more similar to those of North Africa. Differences from the former are increasingly apparent through the Albian–Cenomanian transition. The rate of evolution of the Gamba flora was about the same as that of the Australian flora prior to the Albian, somewhat slower during this stage, but faster from the Cenomanian onwards, implying that this was, to a large extent, a result of the separation of the Indian Plate from Gondwana and its northward drift during the Cretaceous Period. During the Albian, the Australian block drifted eastwards whereas the Indian Plate remained relatively static. This resulted in few changes in the Gamba palynoflora but many in palynofloras from Australia. However, the northward movement of the Indian Plate in the Late Cretaceous led to pronounced changes, with numerous inceptions of genera and species in the Gamba succession. Of these, many have an African or equatorial distribution and none has connections with Australia, indicating that the climate at this time was similar to that of North Africa and that separation from Australia was complete. The arrival of the Indian Plate in equatorial regions allowed floral exchange between its northern part and North Africa during the Santonian.

Fossil evidence of eupolypod ferns in the mid-Cretaceous of Myanmar

Divergence time estimates based on DNA sequence variation of extant species suggest that eupolypod ferns were diverse already in the Cretaceous; however, fossil evidence to support this assumption remains exceedingly rare. Holttumopteris burmensis gen. et sp. nov., a fertile fern foliage fragment preserved in a piece of Albian–Cenomanian Burmese amber from Myanmar, is characterized by divided fertile leaves with catadromous, free lateral veins. Sporangia possess a vertical annulus interrupted by the sporangium stalk and contain monolete spores with a lophate perine. The sporangia occur clustered in discrete sori overarched by a laterally attached, reniform indusium. Reconstruction of ancestral character states suggests affinities of Holttumopteris to the Thelypteridaceae; however, several taxonomically relevant characters are not preserved. This discovery is nevertheless important because H. burmensis represents the first unequivocal fossil of a representative of the eupolypods from the middle Cretaceous.

Cenomanian Turrilitidae (Cretaceous heteromorph ammonites) from the Koppeh Dagh, northeast Iran: Taxonomy and stratigraphic implications

Early and early middle Cenomanian turrilitid ammonoids from the upper part of the Albian–Cenomanian Aitamir Formation of the Koppeh Dagh (northeast Iran) are described, illustrated and placed in an integrated stratigraphic context. The Aitamir Formation represents a graded siliciclastic shelf system and the turrilitid faunas comprise eight different species. Representatives of Mariella and Hypoturrilites have been recorded from a lower Cenomanian horizon in the Ghorghoreh section, corresponding to the Mantelliceras mantelli ammonite biozone. Mariella bicarinata (Kner, 1852) and H. wiedmanni Collignon, 1964 are recorded for the first time from Iran and the larger palaeobiogeographical area, respectively. The horizons with Turrilites costatus and T. scheuchzerianus at Taherabad can be dated as early middle Cenomanian Acanthoceras rhotomagense Zone, T. costatus Subzone. Concentrations of ammonoids commonly occur above regressive sandstone units, at the transition into overlying deeper marine shale units and in their lower parts, respectively. Such intervals represent the early transgressive systems tract of depositional sequences and may thus be regarded as early transgressive, slightly condensed shell accumulations. The uppermost lower to lower middle Cenomanian succession at Taherabad is of striking bio-, event- and sequence stratigraphic similarity to contemporaneous sections in northwest Europe. It reflects deposition during falling and low sea-level associated with the latest early Cenomanian unconformity SB Ce 3 as well as the pulsating transgressive development during the early middle Cenomanian, including levels correlative to the arlesiensis, primus and Mid-Cenomanian events in northwest Europe.

The most ancient member of the Sequoioideae – the new genus Krassilovidendron Sokolova, Gordenko et Zavialova (Cupressaceae s.l.) from the Albian–Cenomanian of Western Siberia (Russia)

The new genus Krassilovidendron Sokolova, Gordenko et Zavialova with the type species Krassilovidendron fecundum Sokolova, Gordenko et Zavialova is described on the basis of numerous compressions of polymorphic shoots in organic connection with seed and pollen cones from the Albian–Cenomanian of the Kubaevo locality (Russian Federation, Kemerovo region, Western Siberia). The new taxon is characterized by an assemblage of features that distinguishes it from all known extant and fossil conifer genera: shoots with helically arranged leaves varying from amphistomatic small scale-like leaves to strictly epistomatic linear-lanceolate leaves; terminal, ellipsoidal to obovate seed cones, bearing 14–26 helically arranged peltate bract-scale complexes (bract and ovuliferous scale are completely fused) with a cylindrical vascular bundle, bifurcating into abaxial and adaxial dichotomizing bundles; up to 22 inverted seeds of various shapes with a protruding micropyle and inconspicuous lateral wings, which are arranged in two to five arcuate rows; solitary terminal pollen cones with helically arranged microsporophylls, each bearing four abaxial microsporangia; and small pollen grains with a relatively short papilla, numerous orbicules on the surface, and a three-layered ectexine with a tectum of strongly fused granules, an infratectum of smaller and more loosely arranged granules, and a thin footlayer. The new taxon possesses a combination of characters indicating it belongs to the subfamily Sequoioideae. Krassilovidendron shares the greatest number of features with Sequoia Endlicher and Sequoiadendron Buchholz, and fewer characters with Metasequoia Miki ex Hu et W.C. Cheng.