Cretaceous Research

Published by Elsevier
Online ISSN: 1095-998X
Publications
Article
Planktonic foraminiferal diversity, equitability and biostratigraphic analysis of samples from Ocean Drilling Program (ODP) Leg 122, Hole 762C show that in general, cool water conditions prevailed during the latest Campanian–Maastrichtian in the eastern Indian Ocean. This is indicated by planktonic foraminiferal assemblages characterized by low species diversity and equitability with abundant rugoglobigerinids and heterohelicids. Archaeoglobigerinids, globigerinelloids, hedbergellids, and long-ranging double-keeled globotruncanids are also present in varying abundance but single-keeled forms occur rarely and sporadically.
 
Article
An almost complete Upper Cretaceous sedimentary sequence recently recovered on the Kerguelen Plateau (southern Indian Ocean) during ODP Leg 183 was analysed for planktonic foraminifera in order to refine and integrate the zonal schemes previously proposed for the Southern Ocean area. Detailed biostratigraphic analysis carried out on holes 1135A, 1136A and 1138A (poleward of 50°S palaeolatitude during Late Cretaceous time) has allowed recognition of low and mid–high latitude bioevents, useful for correlation across latitudes, in addition to known Austral bioevents. The low latitude biozonation can be applied to Turonian sediments, because of the occurrence of Helvetoglobotruncana helvetica, which marks the boundary between Whiteinella archaeocretacea and Helvetoglobotruncana helvetica zones. The base of the Whiteinella archeocretacea Zone falls within the uppermost Cenomanian–Turonian black shale level in Hole 1138A. The stratigraphic interval from upper Turonian to uppermost Santonian can be resolved using bioevents recognized in the mid–high latitude sections. They are, in stratigraphic order: the last occurrence of Falsotruncana maslakovae in the Coniacian, the first occurrence of Heterohelix papula at the Coniacian/Santonian boundary, the extinction of the marginotruncanids in the late Santonian, and the first occurrence of Globigerinelloides impensus in the latest (?) Santonian. The remainder of the Late Cretaceous fits rather well in the Austral zonal scheme, except that Globigerinelloides impensus exhibits a stratigraphic range in agreement with its record at the mid–high latitude sections and extends further downwards than previously recorded at southern sites. Therefore, despite the poor recovery in certain intervals and the presence of several hiatuses of local and regional importance as revealed by correlation among holes, a more detailed zonal scheme has been obtained (mainly for the less resolved Turonian–Santonian interval). Remarks on some species often overlooked in literature are also provided.
 
Article
The taxonomy and taxonomic affinities of the Lenticulina (Astacolus) humilius (Reuss, 1863) “group” in the Lower Cretaceous of north-west Europe are discussed with reference to the naming of a new species in the Lower Aptian in the Isle of Wight. Lenticulina (Astacolus) atherfieldensis sp. nov. is recorded from the type section of the Atherfield “Group” (Lower Aptian) on the Isle of Wight (map ref. SZ 790452) and from Lower Aptian strata in the Paris Basin and the Celtic Sea Basin.
 
Article
The uppermost part of the Upper Cretaceous platform carbonates of the Bey Dağları Autochthon in the Korkuteli, Turkey, area is characterised by an association of hippuritid and radiolitid rudist bivalves dominated by Vaccinites praegiganteus (Toucas). A Late Turonian age is indicated by 87Sr/86Sr values of well-preserved low-Mg calcite of the shells and agrees with the stratigraphical range of the species in the western and central Mediterranean region. This is the first record of Upper Turonian rudists from Turkey. Right valves of 17 specimens of V. praegiganteus from Bey Dağları have been analysed morphometrically and are compared with previously reported specimens from the central and western Mediterranean. Most of the specimens from Turkey differ in having fused posterior pillars.
 
Article
A brief review and discussion of baissine wasps of Gasteruptiidae, Hymenoptera is given. Eight fossil specimens of wasps from the Laiyang Formation in Laiyang, Shandong, China are described. One new genus, Mesepipolaea, and four new species, M. nanligezhuangica, Humiryssus specialis, H. cancellatus and H. vulgatus are established, and two new combinations are proposed: Humiryssus laiyangensis (Hong and Wang, 1990) (originally Aulocopsis laiyangensis Hong and Wang , 1990), H. oculatissimus (Rasnitsyn and Jarzembowski, 1998) (originally Manlaya oculatissima Rasnitsyn and Jarzembowski, 1998). Sinowestratia communicata Zhang and Zhang, 2000 is a junior synonym of Manlaya flexuosa (Ren et al.,1995) (originally Manlaya flexuosus Ren et al.,1995). Stratigraphic inferences from these finds are briefly discussed.
 
Article
It is now generally accepted that the Oceanic Anoxic Event 1a [OAE 1a] correlates with the lower part of the Leupoldina cabri planktonic foraminiferal Zone. Its calibration against the standard ammonite scale, however, seems to be more problematic. This is due, in part, to the fact that ammonites are scarce and/or of little diagnostic value from a biochronological viewpoint in the lower Aptian pelagic successions where the black shale horizons are better developed.We have been able to characterize OAE 1a geochemically in the relatively shallow water deposits of the eastern Iberian Chain (Maestrat Basin, eastern Spain), where ammonite faunas are rich. The interval corresponding to this event is dominated by the genera Roloboceras and Megatyloceras, accompanied by Deshayesites forbesi and Deshayesites gr. euglyphus/spathi. This assemblage is characteristic of the middle/upper part of the Deshayesites weissi Zone. The first occurrence of the species Deshayesites deshayesi (d'Orbigny), which marks the base of the overlying zone, takes place in our sections some metres above the OAE 1a interval.In the historical stratotype region of Cassis-La Bédoule (southern Provence Basin, southeastern France), the OAE 1a interval is also characterized by the presence of Roloboceras and Megatyloceras. Nevertheless, it has usually been correlated with the D. deshayesi Zone. In our opinion, this discrepancy is due to divergences in the taxonomic assignments of the deshayesitids present in these beds. In fact, the specimens attributed by French authors [Ropolo, P., Conte, G., Gonnet, R., Masse, J.P., Moullade, M., 2000. Les faunes d'Ammonites du Barrémien supérieur/Aptien inférieur (Bédoulien) dans la région stratotypique de Cassis-La Bédoule (SE France): état des connaissances et propositions pour une zonation par Ammonites du Bédoulien-type. Géologie Méditerranéenne 25, 167–175; Ropolo, P., Moullade, M., Gonnet, R., Conte, G., Tronchetti, G., 2006. The Deshayesitidae Stoyanov, 1949 (Ammonoidea) of the Aptian historical stratotype region at Cassis-La Bédoule (SE France), Carnets de Géologie / Notebooks on Geology Memoir 2006/01, 1–46.] to D. deshayesi and D. dechyi can be reinterpreted as belonging to D. forbesi.Following this reinterpretation, the Roloboceras beds (equivalent of OAE 1a) of Cassis-La Bédoule would also correspond to the D. weissi Zone. This age is additionally corroborated by data from southern England [Casey, R., 1961a. The stratigraphical palaeontology of the Lower Greensand. Palaeontology 3, 487–621; Casey, R., 1961b. A Monograph of the Ammonoidea of the Lower Greensand, part III. Palaeontographical Society, London, pp. 119–216], and by our recent observations in Le Teil (Ardèche Platform, southeastern France), where the Roloboceras faunas are also associated with Deshayesites consobrinus and Deshayesites gr. euglyphus, taxa that are characteristic of the D. weissi Zone.
 
Article
This study of Tepexi de Rodríguez (Puebla, Mexico), a mid-Cretaceous (Aptian?) locality with exceptional fossil preservation, combines statistically based microfacies-transition analysis with spectral analysis of depth-series measurements, in an attempt to constrain the paleoenvironmental setting. Tepexi de Rodríguez (Tepexi) is largely composed of laminated micrites, and presents a complex amalgam of primary and diagenetically altered fabrics. Modified Markov analysis of microfacies successions was used to assess repetitive patterns among primary microfacies. The reconstructed microfacies succession indicates recurring upward-fining sequences. Spectral analysis of depth-series measurements of magnetic susceptibility and RGB visible color (redness) reveals a pattern of repetition in the sedimentary sequence that is concordant with patterns of Milankovitch cyclicity. Strong eccentricity, obliquity, and semi-precessional signals are inferred. This suite of Milankovitch cyclicities is attributed to double-monsoon influences on Tepexi from both the northern and southern hemispheres, and implies an average rock accumulation rate of 2.0 cm/kyr. Previous reconstructions of Tepexi (e.g. a variety of back-reef lagoonal settings) do not match the observations reported here. Likewise, tidally influenced deposition is ruled out. Tepexi de Rodríguez appears to have been an open marine basin with storm-dominated sedimentation and bottom waters with restricted circulation. The fossil biota has a strong terrestrial influence, indicating that land was close by.
 
Article
This paper is based on Santonian–Campanian sediments of Ocean Drilling Program Sites 1257 (2951 mbsl) and 1259 (2353 mbsl) from Demerara Rise (Leg 207, western tropical Atlantic, off Surinam). According to its position, Demerara Rise should have been influenced by the early opening of the Equatorial Atlantic Gateway and the establishment of a bottom-water connection between the central and South Atlantic Oceans during the Late Cretaceous. The investigated benthic foraminiferal faunas demonstrate strong fluctuations in bottom-water oxygenation and organic-matter flux to the sea-floor. The Santonian–earliest Campanian interval is characterised by laminated black shales without benthic foraminifera in the lowermost part, followed by an increasing number of benthic foraminifera. These are indicative of anoxic to dysoxic bottom waters, high organic-matter fluxes and a position within the oxygen minimum zone. At the shallower Site 1259, benthic foraminifera occurred earlier (Santonian) than at the deeper Site 1257 (Early Campanian). This suggests that the shallower site was characterised by fluctuations in the oxygen minimum zone and that a re-oxygenation of the sea-floor started considerably earlier at shallower water-depths. We speculate that this re-oxygenation was related to the ongoing opening of the Equatorial Atlantic Gateway. A condensed glauconitic chalk interval of Early Campanian age (Nannofossil Zone CC18 of Sissingh) overlies the laminated shales at both sites. This interval contains benthic foraminiferal faunas reflecting increasing bottom-water oxygenation and reduced organic-matter flux. This glauconitic chalk is strongly condensed and contains most of the Lower and mid-Campanian. Benthic foraminiferal species indicative of well-oxygenated and more oligotrophic environments characterise the overlying mid- to Upper Campanian nannofossil chalk. During deposition of the nannofossil chalk, a permanent deep-water connection between the central and South Atlantic Oceans is proposed, leading to ventilated and well-oxygenated bottom waters. If this speculation is true, the establishment of a permanent deep-water connection between the central and South Atlantic Oceans terminated Oceanic Anoxic Event 3 “black shale” formation in the central and South Atlantic marginal basins during the Early Campanian (Nannofossil Zone CC18) and led to well-oxygenated bottom waters in the entire Atlantic Ocean during the Late Campanian (at least from Nannofossil Zone CC22 onwards).
 
Article
The Berriasian to Barremian pelagic succession along the Rio Argos (SE Spain) has been subdivided into sequences which are precisely dated by ammonite biozones. Comparative analyses of ranges of Mediterranean ammonite species and elaborate studies of ammonite diversity revealed seven important changes in ammonite composition between (or even within) certain biozones. These changes are much greater than between most other biozones and represent important faunal turnovers. Similar changes occur at the same levels in other parts of the Mediterranean Region; they are therefore of supraregional significance. Each faunal turnover coincides with a prominent minimum in ammonite diversity and is immediately preceded by a marked maximum in diversity. The turnovers virtually coincide with particular sequence boundaries and are ascribed to severe eustatic sea-level falls with a far higher amplitude than those at most other sequence boundaries. The high diversities preceding the turnovers are ascribed to extra high eustatic sea-level stands, which correspond not only to bundles of extensively transgressive sequences in the Mediterranean Region, but also to major incursions of Tethyan organisms into the boreal seas of northern Germany and Russia. A causal relationship is assumed. The repeated high amplitude sea-level falls were ascribed to a long-term sea-level variation cycle, not apparent from the eustatic curve published by Haq et al. (1988).
 
Article
Terrestrial deposits of the Upper Cretaceous (Campanian) Two Medicine Formation of northwestern Montana preserve multiple bentonite beds (n ≥ 19) that reflect recurrent pyroclastic events in the Western Interior Basin. Major and trace element concentrations were determined on 27 samples derived from four bentonites using X-ray fluorescence spectroscopy. This study evaluates the potential for geochemically distinguishing three of these bentonite beds using a stepwise discriminant analysis of trace element concentrations. Seven elements were found sufficient to establish 100% classification in the group matrix. The elements (in order of decreasing contribution to the canonical discriminant functions) are Zr, Sc, V, Cr, U, Ga, and Th. The validity of these results is strongly supported by cross-validation methods that correctly assigned 100% of randomly-selected bentonite samples left out of the stepwise analysis to their correct bed. These findings indicate geochemical discrimination is a viable tool for correlation within the formation and suggests its application to more distant coeval strata. We also report here a new 40Ar/39Ar age of 77.52 ± 0.19 Ma for one of the analyzed bentonite beds. This new radioisotopic age affords insights into the timing of regional eruptive events, and further constrains the age of the Two Medicine Formation and its renowned fossil resources. Finally, the inferred magmatic composition of the original ash (based on trace element compositions) from the two older bentonites beds suggest a source in the Elkhorn Mountain Volcanics whereas the younger bentonites may have been sourced from the Adel Mountain Volcanics.
 
Article
A sediment sequence which may contain the early Albian OAE 1b was investigated in a deep-water (3800 m) open-ocean environment at Site 417D, western North Atlantic Ocean. Redox cycles, which contain black shale intervals and occur in the early Albian M. gracilis radiolarian Biozone, were studied in order to show processes and climate-associated controlling factors during the deposition of early Albian sediments. The black shale intervals are characterized by the enhanced accumulation and preservation of marine-derived organic matter as determined by Rock-Eval pyrolysis and organic petrology. The presence of laminated sediments, the relationships between organic carbon, iron and total sulfur, pyrite size analysis and trace-metal enrichment indicate the periodic prevalence of anoxic conditions in the pore waters, which may at times have extended to the sediment/water interface. Changes in the mineralogical composition throughout the black shale-dominated interval, i.e., quartz content and clay-mineral assemblage, resulted in the variation of the major-element chemistry and probably reflect cyclic climatic changes in northern Africa combined with flooding of coastal lowlands during an overall transgressive phase in the early Albian. The geochemical signatures observed at different scales demonstrate a genetic link between the climate system on land and processes in the deep ocean during the deposition of black shales in deep-water environments of the western North Atlantic.
 
Article
Site 549 recovered a Lower Cretaceous succession which has been shown to include parts of the Barremian and Albian stages. Forty-four species of Ostracoda are illustrated and their stratigraphic distribution used to recognise three major facies units. An high diversity inner shelf facies earlier in the Barremian gives way to a low diversity, outer shelf facies, higher in the succession. The early Albian appears to indicate a return to an inner shelf fauna. The faunas recovered have been compared to similar faunas elsewhere in N. W. Europe.
 
Geological map of the Bauru Basin with the location area of Peir  ́polis, Uberaba County (modified from Fernandes and Coimbra, 1996). 
Location map and stratigraphic context for the theropod occurrences at Uberaba County, Bauru Basin. 
Abelisauroid dorsal vertebra CPP 893 in cranial (A), caudal (B), left lateral (C) and dorsal (D) views. Detail of prespinal cavity in craniodorsal view (E), and detail of neural spine in right lateral view (F). Abbreviations: cdl , centrodiapophyseal lamina; dp , diapophysis; gr , groove; hyf , hyposphene; hyp , hypanthrum; ls , ligament scar; ogr , oblique groove; pdl , parapodiapophyseal lamina; pnc , pneumatic cavity; pnf , pneumatic foramen; poz , postzygapophysis; pp , parapophysis; prsc , prespinal cavity; prz , prezygapophysis; psc , postspinal cavity; sc , scar; st , spine table. 
A e E, Abelisauroid left femur CPP 174 in cranial (A), caudal (B), medial (C), lateral (D) and distal (E) views. F e J, Abelisauroid pedal phalanx (presumably phalanx 2.III) in dorsal (F), plantar (G), distal (H), lateral (I), and proximal (J) views. Abbreviations: af , abductor fossa; clp , collateral ligament pit; elp , extensor ligament pit; fc , fibular condyle; lf , longitudinal furrow; lip , linea intermuscularis caudalis; lp , lateral prominence; mdc , mediodistal crest; ms , muscle scar; tc , tibial condyle; tfc , tibiofibular condyle. 
Line drawing of the abelisauroid left femur CPP 174 in cranial (A) and caudal (B) views depicting rugosities and muscle scars. Abbreviations: af , abductor fossa; fc , fibular condyle; lf , longitudinal furrow; lip , linea intermuscularis caudalis; lp , lateral prominence; mdc , mediodistal crest; ms , muscle scar; tc , tibial condyle; tfc , tibiofibular condyle. 
Article
Bones of abelisaurid theropods from the Upper Cretaceous (Maastrichtian) Marília Formation, Bauru Basin, Brazil, are here described. They are a dorsal vertebra, the distal part of a femur, and a pedal phalanx corresponding to three specimens found in different fossil sites of Uberaba County, Minas Gerais State. These specimens are the first abelisaurid bones from Uberaba County and thus verify the presence of these theropods, previously indicated only by isolated teeth. The new discoveries, together with that of the abelisaurid Pycnonemosaurus found elsewhere in the Bauru Basin, indicate that these theropods were the most common large predatory dinosaurs in South America during the Cretaceous. The assemblage of abelisaurid theropods and titanosaurid sauropods in the Maastrichtian beds of Brazil is congruent with that documented in same-aged beds of Patagonia.
 
Article
The Campanian to Lower Maastrichtian Abiod Formation of the Ellès section, central Tunisia, has been analyzed bed by bed for cyclostratigraphic purpose. Based on the “20 kyr” precession and “100 kyr” eccentricity cycles, sedimentation rate profiles were generated, which were then transformed into cumulative time scales. The resulting synthetic time scale places identified sedimentary and biological events in a new time-based framework floating around the Campanian-Maastrichtian boundary. This new time scale was compared with previously published geological time scales.
 
Article
A biostratigraphic study carried out in the Monti d'Ocre area, Abruzzi, Central Apennines, allowed us to recognize Orbitolina (Conicorbitolina) moulladei ‘Strata 5 (1985) 1’, Praealveolina iberica Reichel and Praealveolina simplex Reichel in uppermost Albian–lower Cenomanian shelf-edge deposits of the Fossato Machè succession. These foraminifers have now been found for the first time in the Apennines of central Italy; their finding is quite important from a palaeobiogeographic viewpoint, as it contributes to the improvement of our knowledge on facies distribution in the circum-Mediterranean regions during the Cretaceous Period. In the study area, the coeval Monte Rotondo and Monte Orsello sections also crop out; these are characterized by bauxite deposits and stratigraphic gaps reflecting episodes of emergence on the carbonate platform. The Monte Rotondo and Monte Orsello sections accumulated in a platform back-reef environment; consequently, in this sector of the Monti d'Ocre area, the depositional environment shifted from a back-reef westward and southward to a shelf-edge northward, during the latest Albian–early Cenomanian. Owing to synsedimentary tectonics, the area investigated underwent differential subsidence: westward and southward, wide areas were uplifted and subjected to emergence, karstification and bauxite accumulation, whereas sedimentation continued in a shelf-edge environment in the north-eastern area.
 
Article
The Cretaceous of the United Arab Emirates is divided into three major lithostratigraphic units separated by three regional unconformities: Lower Cretaceous Thamama Group (Berriasian-mid-Aptian); Mid-Cretaceous Wasia Group (Albian-Cenomanian, possibly Early Turonian) and Upper Cretaceous Aruma Group (Coniacian-Maastrichtian). In the United Arab Emirates, because of the abundance of subsurface data, it has been possible to relate the character of the Mesozoic shelf carbonates and their associated minor clastics and evaporites to eustatic sea-level changes. The patterns of sedimentation were driven by gentle tectonic subsidence punctuated by eustatic sea-level variations. Most of the carbonates are sheets formed in response to deposition during sea-level highstands while some of the upper Lower, Middle, and Upper Cretaceous carbonates contain build-ups that caught up with the sea-level highstands following rapid marine transgressions that initially stressed deposition. Shale-rich units deposited during sea-level lowstands and transgressive phases are common in the Cretaceous sequences. They occur in the Lower Cretaceous Lekhwair Formation and Bab Member. The Middle Cretaceous includes the lowstand Nahr Umr Formation and the basinal Shilaif, while the Upper Cretaceous contains the transgressive Laffan shales.
 
Article
Vertebrate microfossils, including abundant dinosaur teeth, recovered from a series of horizons in the Late Cretaceous (Turonian–Campanian) Bostobynskaya Formation (Bostobynskaya Svita), north-east Aral Sea region, Republic of Kazakhstan, display taphonomic characteristics consistent with deposition within floodplain-hosted assemblages. Teeth collected from the horizons confirm the presence of theropods, hadrosaurs and sauropods in the formation, consistent with previous suggestions of the dinosaur fauna. Compositional analysis of microfossil collections show that the material is characterised by low weathering and abrasion states, a high diversity of small fossils that represent aquatic, semi-aquatic and terrestrial taxa, and an abundance of resistant bioclasts, such as teeth. The sedimentology of the Bostobynskaya Formation is dominated by crevasse-splay and flood-event facies. New records from these sites document an important Late Cretaceous vertebrate fauna in an equally important and much understudied part of Central Asia.
 
Article
The biostratigraphic correlation scheme of Upper Cretaceous multicoloured claystones in the Polish Romanian. External Carpathians using agglutinated deep-water foraminifers can be extended to onshore localities in the Gibraltar Arch area (Morocco, Spain) and DSDP/ODP sites in the North Atlantic. In all studied areas, taxonomic turnovers in deep-water agglutinated foraminifers are observed at the Cenomanian-Turonian boundary and in the early/middle Campanian. Additionally, a remarkable decrease in abundance and diversity of benthic agglutinated foraminifers is observed at the same levels in continuous sections of North Atlantic DSDP sites. These datum levels correspond to inter-regional and time-constant palaeoceanographic events, and may facilitate the direct correlation of the biozonation of agglutinated foraminifers to the standard geomagnetic polarity time scale.
 
Article
A new fossil species of oribatid mite, Ametroproctus valeriae sp. nov., belonging to the family Ametroproctidae is described. The new species is preserved in a piece of amber from the San Just outcrop in Teruel Province, Spain, which is believed to be Albian in age. Comparison is made between the new species and extant species of the family.
 
Article
A new genus and species of coelurosaurian theropod dinosaur from the Wessex Formation (Early Cretaceous, Barremian) of the Isle of Wight, England, is described and named. Distinctive characters of the premaxilla, its dentition, maxilla and nasals allow it to be diagnosed. The teeth in the premaxilla are D-shaped in cross-section and the nasals are fused. The hands are elongate and slender and the hindlimbs are gracile. Lack of element fusion elsewhere in the skeleton suggests that it is a subadult. Numerous character states are shared with tyrannosaurids but the new taxon appears to be excluded from the group that comprises aublysodontine and tyrannosaurine tyrannosaurids. We conclude that the taxon is a basal tyrannosauroid and as such it is one of the earliest and (with the exception of some teeth and an isolated ilium from Portugal) the first from Europe. Implications for tyrannosauroid biogeography and evolution are discussed. The animal was part of an unusual taphonomic assemblage in which some elements were partially articulated while others were scattered or broken.
 
Article
An investigation of silicified ovules/seeds recovered from the Early Cretaceous intertrappean rocks of Sonjori, Rajmahal Basin, has revealed the occurrence of Acmopyle-like ovules/seeds described here as Podospermum rajmahalensis gen. et. sp. nov. These fossils depict characteristic features of podocarpaceous ovules/seeds, i.e., erect posture of drupaceous ovule/seed subtended by a fertile bract; ovuliferous scale indistinguishable from the integument enclosing an ovule; integument consisting of three layers and a nucellus free from integument except at base. The presence of two archegonia in the apical part of the female prothallus and the presence of tentpole-like nucellar tissue in the ovule indicate the post-pollination stage of development of the ovule. Moreover, the presence of embryonic tissue in the female prothallus indicates the post-fertilization stage. The presence of these podocarpaceous remains further confirms the palaeoposition of the Indian subcontinent during the Early Cretaceous period.
 
Article
Bathymetric change is investigated within the transgressive phase of an extensive Early Cretaceous (Aptian-Albian) marine flooding of the Australian continent. Lithofacies and biofacies associations, found in nine outcrop sections and four continuously cored bore sections in the northeastern Eromanga Basin, are used to reconstruct depositional environments and to determine palaeobathymetry. Shoreface (c . 0–2 m water depth), transitional (c . <10 m), upper offshore (c . <50 m), and lower offshore (c . 50–100 m) facies are distinguished. Curves showing bathymetric changes are constructed for each stratigraphic section, and are placed in a time framework by biozones and compared across the region. Three depositional cycles are tentatively recognized during the transgressive phase. The first depositional cycle includes the Gilbert River Formation and the lower part of the Doncaster Member, and ranged from early Aptian (or late Barremian) to within the late Aptian. During maximum flooding, water depth was greatest in the southwest of the study area. Most sediment accumulation occurred under standstill conditions, and a fall in relative sea level occurred at the end of the cycle in all areas within the study region. The second cycle, during the later part of the late Aptian, includes the upper Doncaster Member and the Jones Valley Member. Most sediment accumulation occurred under fluctuating water depths, but a fall in relative sea level ends the cycle in all areas. The third depositional cycle includes the Ranmoor Member, and was represented by a significant late Early Albian transgressive pulse, recognized in age-equivalent formations from widely separated basins in Australia. At maximum flooding, the sea-floor was deepest in the northeast and shallowest in the southwest of the study area. The reversal in the direction of the bathymetric gradient between cycle 1 and cycle 3 in the region is probably related to tectonism along the eastern Australian margin. The apparent lack of correspondence between the Australian Albian record and the global sea-level curve suggests that continental-wide tectonism was an important influence in determining Australian sea levels during this time.
 
Distribution of the Yezo Supergroup and index map showing study areas.
List of inoceramid specimens from the Oyubari area measured for this paper
A, Mytiloides sp. (WE. P551), left valve, locality Y070085 of Hirano et al. (1989) and Kawabe (2000), lower Lower Turonian, Hakkinzawa River, Oyubari area. B, Inoceramus kamuy Matsumoto and Asai (WE. P523), right valve, locality 5418 of Tanabe et al. (1977), lower Lower Turonian, Kanajirizawa River, Tappu area. C, Inoceramus hobetsensis Nagao and Matsumoto (WE. P327Y), right valve, locality Y070059 of Hirano et al. (1989), upper Lower Turonian, Hakkinzawa River, Oyubari area. D, Actinoceramus nipponicus (Nagao and Matsumto) (WE. P333Y), left valve, locality Y070077 of Hirano et al. (1989) and Kawabe (2000), upper Upper Cenomanian, Hakkinzawa River, Oyubari area. E, Inoceramus pictus minus Matsumoto (WE. P545), left valve, locality 5401 of Tanabe et al. (1977), lower Upper Cenomanian, Kanajirizawa River, Tappu area. F, Inoceramus pennatulus Pergament (WE. P554), right valve, locality Y070077 of Hirano et al. (1989) and Kawabe (2000), upper Upper Cenomanian, Hakkinzawa River, Oyubari area. 
List of endemic and cosmopolitan species
Compiled size-frequency distributions for three areas, and ratios of relatively large specimens in each interval. N, number of specimens.
Article
This paper describes the responses of inoceramid bivalves to events across the Cenomanian/Turonian boundary (C/T boundary), and the marine environments inferred from these responses, within the Yezo forearc basin, Hokkaido (northern Japan), as based on examination of newly collected specimens and a literature survey. All Late Cenomanian inoceramid species in this region became extinct at the C/T boundary and were replaced by newly evolved Early Turonian taxa. This change in generic composition, accompanied by stunting, a decrease in interspecific size variation, and predominance of cosmopolitan species evidently occurred immediately after the C/T transition. Based on these results and on previous studies, inoceramids would have been affected by oxygen-depleted conditions associated with Oceanic Anoxic Event 2. Consequently, niches became vacant in the Yezo forearc basin just after the C/T transition, and small, cosmopolitan species invaded those niches in the early Early Turonian. Faunal stunting suggests that oligotrophic conditions spread into the basin immediately after the C/T boundary.
 
Article
The history of definition of the Aptian-Albian boundary is reviewed with particular reference to the ammonite schemes of Brinkmann (1937), Breistroffer (1947), Casey (1961a, 1996, 1999), Kemper (1982), Owen (1996, 1999), and Ruffell & Owen (1995). The classic sequence in the Hannover area of Germany described by Brinkmann (1937) is reviewed in the light of subsequent work. The definition of the base of the Albian Stage at the first occurrence of the ammonite Proleymeriella schrammeni (Jacob, 1907) is rejected as it can only be recognised over a limited area near Hannover; no more widely recognised secondary markers have been documented, and there is no permanent section at the present time.An alternative Aptian-Albian boundary, defined by the first occurrence of the ammonite Leymeriella (L.) tardefurcata (d'Orbigny, 1841) in the expanded Marnes Bleues section at Tartonne, Alpes-de-Haute-Provence, France, is suggested.The palynomorph, coccolith, planktonic foraminiferan, ammonite, and inoceramid bivalve sequence, organic and inorganic carbon, trace, rare earth, and major element record, oxygen and carbon isotope sequence, and strontium isotope data are presented for sections at the Col de Pré-Guittard, Arnayon (Drôme), and Tartonne (Alpes-de-Haute-Provence) and described in detail. The Pré-Guittard section, considered as a candidate Global Boundary Stratotype Section (GSS) for the base of the Albian Stage at the Second International Symposium on Cretaceous Stage Boundaries held in Brussels in September 1995, provides a standard section for the boundary interval in SE France. It is, however, unsuitable as a GSS, as there is a hiatus at the critical level in the section. In contrast, the Tartonne section is a potential GSS. The Boundary Point for the base of the Albian Stage suggested here is the first criterion proposed at Brussels: the first appearance of the ammonite Leymeriella (L.) tardefurcata at the base of the Niveau Paquier within the expanded Marnes Bleues sequence. The first appearance is only 60 cm above the last record of its presumed ancestor, L. (L.) germanica Casey, 1957. So defined, the boundary lies within thePrediscosphaera columnata Nannofossil (NF) Zone NC/CC8, and the planktonic foraminiferal Hedbergella planispira Partial Range Zone.There is no major or trace element event associated with the proposed boundary, nor is there any distinctive oxygen or carbon isotopic signal. Strontium isotope data from the Tartonne section are compatible with those elsewhere in the basin, and show that the base of the Albian, defined by the first appearance of L. (L.)tardefurcata corresponds to an87Sr/86Sr ratio of 0.707339±2.Systematic sections deal with a new palynomorph, calcareous nannofossils and ammonites; full range data and taxonomic indices are given for the first two groups.
 
Article
Key exposures through the Late Cretaceous (Campanian-Maastrichtian) Marambio Group are located in the Admiralty Sound region, James Ross Island group, Antarctica. On southern James Ross Island, an extensive sequence of bioturbated silty mudstones, muddy sandstones, fine-grained sandstones, ash layers and rare conglomerates has been subdivided into two component members of the Santa Marta Formation: the Rabot Member and the overlying, newly defined, Hamilton Point Member. Both members are fossiliferous, and have yielded a variety of both macro- and microbiotas indicating relatively shallow (i.e., shelf depth) marine conditions. In particular the Rabot Member contains an assemblage of both heteromorph and regularly coiled ammonites, giant inoceramid bivalves, and other benthos. A combination of both ammonite and palynomorph evidence suggests that both the Rabot and Hamilton Point members are early to late Campanian in age. The Santa Marta Formation is believed to pass directly up into the newly defined Snow Hill Island Formation, which forms the majority of the exposure on Snow Hill Island and the south-westernmost tip of Seymour Island. This unit comprises poorly lithified grey sandy mudstones, lithified fine-grained sandstones, and dark mudstones. It contains numerous concretion horizons and is typified by the late Campanian-early MaastrichtianGunnarites antarcticusmolluscan assemblage. The Snow Hill Island Formation is in turn unconformably overlain by the López de Bertodano Formation, which, as redefined herein, is restricted to the northern tip of Snow Hill Island, Seymour Island, and one small exposure on Vega Island. An informal lithostratigraphical unit characterised by distinctive, pale grey weathering mudstones is identified at the base of the López de Bertodano Formation, and on the basis of palynological studies may be of mid- to late Maastrichtian age. The stratigraphical scheme presented here has enabled us to enhance regional correlation of the Late Cretaceous strata within the James Ross Basin. Based on these new correlations, we can prove that the Campanian-Maastrichtian sequence is between 2500 and 2900 m thick. This is one of the thickest onshore Late Cretaceous successions in the Southern Hemisphere, and has the potential to become a key reference section. In addition, given its high palaeolatitude location, it is a crucial locality to examine Late Cretaceous palaeoenvironmental change.
 
Article
The chronostratigraphy of Coniacian–Maastrichtian platform carbonates exposed on the island of Brač and the adjacent mainland has been revised, based on numerical ages derived from strontium-isotope stratigraphy (SIS) of low-Mg calcite of rudist shells. The Dol intra-platform basin formed during the mid-Coniacian–early Santonian. The base of the prograding Pučišća Formation is of mid-Santonian age (84.9 Ma) in the southeast, and late Middle Campanian (77.3 Ma) in the northwest of the island, indicating a progradation rate of the platform margin of ca. 2.5 km/myr. Subaerial exposure of the platform occurred during the latest Middle Campanian and is coeval with a major drop in sea level reported from the Boreal Realm, North America, and the southern Tethyan margin. The base of the Sumartin Formation is revised here to the earliest Late Campanian (ca. 75 Ma). At its top, the formation contains rudist-bearing limestones of latest Maastrichtian age (65.4–65.0 Ma). The exact position of the K/T boundary cannot be drawn due to the lack of material suitable for SIS, and to the absence of diagnostic fossils in restricted innermost-platform deposits of the Liburnian Formation, which follows conformably over the rudist-bearing Sumartin Formation.Based on the revised chronostratigraphy of platform evolution, and particularly on the numerical ages that constrain the progradation of the Pučišća Formation, the stratigraphic ranges of characteristic Tethyan rudist bivalves and benthic foraminifers are re-evaluated.
 
Article
The Adriatic-Dinaridic carbonate platform (ADCP) was one of the largest and relatively well preserved Mesozoic platforms in the Mediterranean region (central Tethys). The peninsula Istria, in the northwestern part of the ADCP, is built up predominantly of shallow-water carbonates of the Middle Jurassic (Dogger) to Eocene age and, to a lesser extent, of Paleogene clastic deposits (flysch and calcareous breccia). This study focuses on a Lower Cretaceous (Barremian to Albian) succession of strata at five localities in western Istria. Stratigraphic determinations are based on identification of nine microfossil assemblages (benthic foraminifera and calcareous algae Dasycladales) and on using their taxa as index fossils. The age of strata with these microfossil assemblages, however, is questionable. Most of the age uncertainties are associated with a regional emersion, which occurred on the ADCP during the Aptian or close to the Aptian–Albian transition. It is unclear what portions of the Upper Aptian and/or Lower Albian are missing along this unconformity. A stable isotope study was conducted on homogenous micritic matrix samples in an attempt to resolve some of these uncertainties. Variations in carbon isotope compositions proved useful for stratigraphic correlation between the examined successions of strata, for improving their age determination, and for relating them to other coeval successions that span an important time interval of major oceanographic changes and carbon-cycle perturbations associated with the Early Aptian oceanic anoxic event (OAE 1a).
 
Article
In this work, we examine the transition from an ephemeral palustrine to a desertic sand sheet depositional system, corresponding to the Araçatuba Formation and Vale do Rio do Peixe Formation, respectively. These Upper Cretaceous formations form the lower part of the sedimentary sequence that fills the intracratonic Bauru Basin in the South American Platform (southeast Brazil). The transition between the two formations is through paleosols located at the top of the Araçatuba Formation, which have different spatial and temporal evolutions. In the inner, southern, and western parts of the Araçatuba Formation area, the paleosols are well developed, while in the outer, northern and eastern parts they are less developed. In the inner area, the mature paleosols are in sharp contact with the overlying deposits of the Vale do Rio do Peixe Formation, while in the outer area, immature paleosol successions in which sedimentary and pedogenetic features are interlayered represent the transition. Ghosts of sedimentary structures in the outer paleosols allow us to attribute the variations in paleosol development to different sedimentary inputs. In the outer part, a slow but continuous supply of sediment caused continuous rejuvenation of the soils, whereas in the inner portion the absence of sedimentary input allowed very mature soils to form. The transition between Araçatuba and Vale do Rio do Peixe formations may thus be explained by a sudden increase in sedimentation in the area, probably triggered by tectonic uplift in northern and eastern parts of the Bauru Basin, causing the progradation of alluvial fans of the Marília Formation, which supplied sediments to the sand sheet depositional system of the Vale do Rio do Peixe Formation.
 
Article
Parapetala liaoningensis gen. et sp. nov. is described from the Lower Cretaceous of China. It has a very basal position in the clade Aeshnoptera (Odonata. Petalura, Spec. 2 (1996) 402), basal or close to the Upper Jurassic family Mesuropetalidae. This discovery confirms the high diversity of this group of dragonflies during the Late Jurassic–Early Cretaceous, suggesting rapid evolution of this clade in the Early or Middle Jurassic.
 
Article
Results based on taxonomic and biostratigraphic studies of marine Cretaceous ostracods collected from the Potiguar and Sergipe basins on the northeastern continental margin of Brazil are presented. The assemblages comprise more than 100 taxa, ranging in age from late Aptian to Campanian. Many taxa show restricted vertical ranges which make them stratigraphically useful. In the Potiguar Basin the Albian–Campanian succession comprises six biozones based on ostracods, whereas in the Sergipe Basin the upper Aptian–Coniacian succession comprises four biozones.
 
Wing venation of Sinonemestrius akirai sp. nov., holotype. Crosses indicate convex areas in the wing; broken lines in all fi gures indicate convex folding. Scale bar represents 1 mm. 
Wing venation of Heterostomus curvipalpis, Recent, Chile. Scale bar represents 1 mm.
Wing venation of Exeretoneura maculipennis, Recent, Tasmania (after Mackerras, 1925, with modification).
Article
A distinctive but rare fly, Sinonemestrius akirai sp. nov. (family Xyophagidae), is described from the upper Hauterivian of southern England. This extends the range of the genus Sinonemestrius outside of China for the first time, and supports a Cretaceous date for the Laiyang Formation.
 
Article
The Cretaceous sediments of the Iullemmeden Basin represent two major biosedimentary episodes. The first, during the “Neocomian” to Cenomanian, is dominated by deposition in a nonmarine basin characterized by braided river and meandering shallow river, floodplain systems. The Upper Cretaceous, from Cenomanian to top Maastrichtian is characterized by an alternation of shallow marine, coastal plain deposits. During this episode the basin forms, albeit intermittently, the central region of the trans-Saharan seaway, which connected waters of the opening Atlantic with those of Tethys. Migration routes for both marine and nonmarine faunas existed throughout the Cretaceous period across the Iullemmeden region.
 
Article
Nonmarine Cretaceous rocks of mainly Early to mid-Cretaceous age are found widely scattered throughout the African continent, including Madagascar and the Middle East. Correlation of these rocks between regions has been attempted in the northern part of Africa, but the less frequent outcrops south of the Sahara are poorly understood and correlations are very tentative. It is premature to attempt a continent-wide correlation scheme, but inter-regional correlations are presented to understand better the nonmarine Cretaceous throughout Africa and the Middle East. The Saharan region is dominated by nonmarine “Continentale Intercalaire” and “Nubian Sandstone” clastics of Early to mid-Cretaceous age, and in Egypt, locally Late Cretaceous. The rocks labelled “Nubian Sandstone” can be correlated into the Arabian Peninsular, where it was deposited around the Arabian craton prior to inundation by Tethyan transgressions. The opening of the South Atlantic invoked tectonic stresses forming pull-apart basins in West Africa, and exploited the Pan-African shear zone cutting central Africa forming basins from Nigeria to southern Sudan. Intracratonic basins in northern Sudan and Egypt resulted from tectonic stresses associated with the opening of the Red Sea and the northward convergence of Africa into the European continent. Nonmarine Cretaceous deposits in central and inland south-eastern Africa outcrop sporadically and are associated with regional extensional tectonics related to the separation of Madagascar. Coastal basins of Mozambique and South Africa containing marginal nonmarine Cretaceous facies appear to be associated with the separation of Madagascar and the Falkland Plateau from Africa. The ages of nonmarine Cretaceous strata in Africa and the Middle East are often imprecisely known, although recent palynostratigraphic results have improved precision. Vertebrate and megaplant fossils are found throughout the continent, but their biostratigraphic value is rather general. Nonmarine sedimentation in Africa and the Middle East is predominantly pre-Cenomanian, with some Upper Cretaceous rocks occurring in Egypt, Somalia, Yemen, Nigeria and Madagascar during regressive episodes.
 
Article
Lower Aptian strata exposed in the Agadir Basin of the Western High Atlas represent the fill of a fluvial valley incised during the Early Aptian (Bedoulian) sea-level fall. The valley fill comprises a diverse assemblage of lithofacies that can be grouped into lowstand, transgressive, and highstand systems tracts. Fluvial conglomerates and pebbly sandstones, referred to the lowstand systems tract, incised into the underlying Late Barremian marginal-marine deposits to form a basal sequence boundary. As sea level began to rise, fluvial deposits were reworked into alternating couplets of moderately bioturbated sandstones and mudstones that display tidally-influenced, inclined, heterolithic strata. The transgressive systems tract comprises the bulk of the estuarine fill and consists of a seaward and landward thinning wedge of tidally-influenced fluvial, tidal flat, estuarine point-bar and bay-fill deposits. Highstand infilling of the valley was characterised by estuarine mouth bars and shoal progradation.
 
Article
K−Ar ages were measured on biotite from six bentonite beds in the Upper Cretaceous (latest Cenomanian (?) and earliest Turonian) Seabee Formation of norther Alaska. The bentonite beds occur in the Shale Wall Menber of the Seabee Formation in three different coreholes in the Umiat and Simpson regions of the National Petroleum Reserve in Alaska. Fossil-bearing localities in the Shale Wall Member contain bivalves of the Inceramus labiatus (Schlotheim) group that has a worldwide distribution in rocks of mostly early Turonian age. The K−Ar ages range from 91.5±0.9 to 93.6±1.2 Ma and indicate an age of about 92 Ma for the highest occurrence of the I. labiatus group in the three coreholes.
 
Article
Deep-water agglutinated Foraminifera (DWAF) display potential for correlating pelagic (calcareous and non-calcareous) and flysch environments. This is illustrated by an example from Sites 765 and 261 on the Argo Abyssal Plain. A working zonation based on DWAF has been developed for Lower Cretaceous flysch sequences of the Polish Carpathians, but this zonal scheme has not been tested in other areas of the Tethys. No zonation has yet been developed for abyssal oceanic DWAF. The challenge for the future, under the auspices of Project 262, is to test the existing zonation in other regions and develop a widely applicable biochronology for integration into a general Tethyan biochronological correlation scheme.
 
Article
Alluvial conglomerates were widely distributed around the margin of the Early Cretaceous North American Cretaceous Western Interior Seaway (KWIS). Conglomerates, sandstones, and lesser amounts of mudstones of the upper Albian Nishnabotna Member of the Dakota Formation were deposited as fill-in valleys that were incised up to 80 m into upper Paleozoic strata. These paleovalleys extended southwestward across present-day northwestern Iowa into eastern Nebraska. Conglomerate samples from four localities in western Iowa and eastern Nebraska consist mostly of polycrystalline quartz with lesser amounts of microcrystalline (mostly chert), and monocrystalline quartz. Previous studies discovered that some chert pebbles contain Ordovician–Pennsylvanian invertebrate fossils. The chert clasts analyzed in this study were consistent with these findings. In addition, we found that non-chert clasts consist of metaquartzite, strained monocrystalline quartz and ‘vein’ quartz from probable Proterozic sources, indicating that parts of the fluvial system’s sediment load must have travelled distances of 400–1200 km. The relative tectonic stability of this subcontinent dictated that stream gradients were relatively low with estimates ranging from 0.3 to 0.6 m/km.
 
Article
A dark-coloured trace fossil assemblage from the Cretaceous/Palaeogene (K/Pg) boundary interval in the Agost section (Betic Cordillera, south-east Spain) has been examined. These trace fossils, of early Danian age, are located within host Plummerita hantkeninoides Biozone (Late Maastrichtian) sediments. The assemblage consists of Chondrites ?targionii, Zoophycos isp., Planolites isp. (two size classes), ?Thalassinoides isp. A, T. isp. B, T. isp. C, Alcyonidiopsis longobardiae, and Diplocraterion ?parallelum. The latter two species are described here for the first time within K/Pg boundary intervals. Major differences in trace-fossil composition between the Agost and other K/Pg boundary sections (Denmark, Alabama and north-east Mexico) can be related to palaeoenvironmental factors, mainly reflecting the more distal and deeper environment of the Agost section.
 
Article
Mesozoic bryozoans are uncommon in the Southern Hemisphere and none have yet been described from the Lower Cretaceous of Argentina. This paper describes six taxa from the lower Valanginian to the upper Hauterivian-?lower Barremian Agrio Formation of the Neuquén Basin. New species are Charixa burdonaria sp. nov., notable for being the oldest known spine-bearing cheilostome and for constructing multilayered colonies intergrown with serpulid worms, and an unusual cyclostome described as Neuquenopora carrerai gen. et sp. nov. The poor preservation and/or lack of diagnostic gonozooids makes taxonomic assignment of the remaining bryozoans, all cyclostomes, uncertain. Apart from Multizonopora sp., a cerioporine cyclostome with bushy, ramose colonies, all of the Agrio Formation bryozoans are encrusters. In general, the Agrio Formation bryozoan fauna resembles faunas from the Neocomian and Aptian of north-west Europe. The relatively low diversity may be an artefact of collecting effort, although environmental factors may also be important, with the intergrowths between C. burdonaria and serpulids from the top of the Agrio Formation being reminiscent of some present day occurrences of primitive cheilostomes in lagoons with fluctuating salinities.
 
Article
Twenty three different sites in two areas of Río Negro Province (Salitral Ojo de Agua and Salitral de Santa Rosa-Salinas de Trapalcó), preserving eggs and eggshells from the Allen Formation (Upper Cretaceous) were studied, and five egg levels were identified. Three different types of eggshell were recognized. Eggs possessing thick eggshells of Type 1 are abundant in both areas, sometimes associated with eggs having thinner shells. Eggs of eggshell Type 1 are included in the oofamily Faveoloolithidae of the parataxonomic classification. Eggshell Type 2 is subdivided into two groups (Types 2A and 2B), mostly based on the mean thickness of the eggshells and other parameters. Eggs of eggshell Type 2 are assigned to the oofamily Megaloolithidae of the parataxonomic classification, and ascribed to titanosaurs. A third type of eggshell (Type 3) is only recorded at one of the localities (Salitral Ojo de Agua, egg level 2). This type is intimately associated with theropod bones, and its microstructure agrees with an assignation to the Theropoda. It is assigned to the oofamily Elongatoolithidae.
 
Article
The Upper Cretaceous (?Santonian) Aitym Formation in the central Kyzylkum Desert, Uzbekistan, produced remains of a cimolodontan multituberculate (Uzbekbaatar wardi), a spalacotheriid symmetrodont (cf. Shalbaatar sp.), a deltatheroidan (cf. Deltatherus sp.), possibly the asioryctithere aff. Daulestes sp., possibly two zalambdalestids (Kulbeckia sp. cf. K. kulbecke and aff. Kulbeckia sp.), two supposed lipotyphlans (Paranyctoides sp. cf. P. aralensis and Paranyctoides sp.), and zhelestid ungulatomorphs (cf. Aspanlestes sp., Parazhelestes sp. aff. P. minor, Parazhelestes sp. cf. P. robustus, and Eoungulatum sp. cf. E. kudukensis). The Aitym mammal fauna is most similar to the more diverse mammal fauna of the underlying Bissekty Formation (upper Turonian–Coniacian). Uzbekbaatar and Shalbaatar were most probably derived from North American immigrants. Paranyctoides and ‘Zhelestidae' are of Middle Asian (a commonly and long used Soviet geographic region approximately extending from the Caspian Sea on the west to the Chinese border on the east, and from the Iranian and Afghan borders on the south to southern Kazakhstan on the north) origin and migrated to North America during the late Santonian–early Campanian. A dispersal route was present in Beringia during the entire Late Cretaceous, which may have worked as a cold filter, allowing intercontinental dispersals between Asia and western North America in both directions, especially during shorter, warm climatic phases.
 
Article
A new amber-rich deposit has been identified in the Upper Cretaceous (Santonian) Eutaw Formation exposed in eastern Alabama, U.S.A. Amber occurs as common parautochthonous clasts and in direct association with conifer plant parts in the lower part of a thin, laterally discontinuous, carbonaceous and pyritiferous clay lens that was deposited in a tidal channel within a transgressive estuarine bayhead-delta system. Organic inclusions are common in amber clasts and include plant and fungal debris and terrestrial arthropod remains. The latter include mites, a spider in association with its web, and scale insects. Amber-plant associations and amber geochemistry indicate that resins were derived from the Cupressaceae, virtually identical to the trees that produced the Turonian-aged amber from central New Jersey, USA.
 
Article
Acanthoceratid ammonites from near Maceió, in the State of Alagoas, provide evidence of a mid-Cretaceous marine incursion into the present onshore part of the Alagoas Basin. The ammonites Pseudocalycoceras sp. cf. P. harpax (Stoliczka, 1864) and Kamerunoceras sp. are assigned a late Cenomanian age. The rock is a siliceous oolite that occurs as derived nodules and fragments in late Cenozoic continental sediments. It is interpreted as an originally calcareous oolite formed in a near-shore, high-energy environment. Absence of primary cement suggests that silicification took place early in diagenesis. The silicified, and therefore more resistant material from the original Cenomanian sequence was reworked and redeposited with the Cenozoic sediments. The age, indicated by the ammonites, suggests that the original deposition was related to the global late Cenomanian—early Turonian sea-level rise.RésuméA ocorrência de amonóides da família Acanthoceratidae ao sudoeste de Maceió (Estado de Alagoas) fornece evidência de uma incursão marinha durante o meso-Cretáceo, na atual parte emersa da Bacia de Alagoas. Aos amonóides, Pseudocalycoceras cf. harpax (Stoliczka) e Kamerunoceras sp., é atribuída uma idade neocenomaniana. A rocha que contem os amonóides é constituída por oolito silicoso que ocorre em forma de nódulos e fragmentos isolados nos sedimentos neocenozóicos continentais do Grupo Barreiras. É interpretada como um oolito originalmente calcáreo, formado num ambiente litorâneo de energia alta. A ausência de cimento primário sugere que a silicificação ocorreu na fase inicial da diagênese. O material silicificado, e portanto mais resistente, da seqüência original cenomaniana foi retrabalhado e redepositado junto com os sedimentos cenozóicos. A idade indicada pelos amonóides sugere que a deposição original do oolito foi relacionada ao levantamento global do nível do mar que ocorreu durante o neo-Cenomaniano-neo-Turoniano.
 
Article
The Doyran section in the Alakırçay Nappe of the Antalya Nappes includes the organic carbon-rich black shales within radiolarian-rich pelagic sediments that were deposited in an off-margin abyssal environment. A biostratigraphical analysis, based on radiolarian assemblages, indicates that the rock units studied encompass the Cenomanian/Turonian boundary (CTBE). The total organic carbon contents of the black shales in this horizon vary from 7.89 to 42.19% wt with an average value of 22.0% wt. The calculated values of the hydrogen and oxygen indexes indicate that the organic carbon originated from marine organic matter (type I/II kerogen). The black shales include thin-bedded and laminated layers deposited at low sedimentation rates with little terrestrial input. Lamination, no bioturbation and abundant pyrite occurrences indicate that the anoxic conditions prevailed on the depositional environment and favoured the preservation of organic matter. Lithological features and the radiolarian fauna of the CTBE in the Doyran section are in keeping with each other and correlate with the CTBE at other localities in the Atlantic and Tethyan realms.
 
Article
A 178-m-thick stratigraphic section exposed along the lower Colville River in northern Alaska, near Ocean Point, represents the uppermost part of a 1500 m Upper Cretaceous stratigraphic section. Strata exposed at Ocean Point are assigned to the Prince Creek and Schrader Bluff formations. Three major depositional environments are identified consisting, in ascending order, of floodplain, interdistributary-bay, and shallow-marine shelf.Nonmarine strata, comprising the lower 140 m of this section, consist of fluvial distributaries, overbank sediments, tephra beds, organic-rich beds, and vertebrate remains. Tephras yield isotopic ages between 68 and 72.9 Ma, generally consistent with paleontologic ages of late Campanian–Maastrichtian determined from dinosaur remains, pollen, foraminifers, and ostracodes.Meandering low-energy rivers on a low-gradient, low-relief floodplain carried a suspended-sediment load. The rivers formed multistoried channel deposits (channels to 10 m deep) as well as solitary channel deposits (channels 2–5 m deep). Extensive overbank deposits resulting from episodic flooding formed fining-upward strata on the floodplain. The fining-upward strata are interbedded with tephra and beds of organic-rich sediment. Vertical-accretion deposits containing abundant roots indicate a sheet flood origin for many beds. Vertebrate and nonmarine invertebrate fossils along with plant debris were locally concentrated in the floodplain sediment. Deciduous conifers as well as abundant wetland plants, such as ferns, horsetails, and mosses, covered the coastal plain. Dinosaur skeletal remains have been found concentrated in floodplain sediments in organic-rich bone beds and as isolated bones in fluvial channel deposits in at least nine separate horizons within a 100-m-thick interval. Arenaceous foraminifers in some organic-rich beds and shallow fluvial distributaries indicate a lower coastal plain environment with marginal marine (bay) influence.Marginal marine strata representing interdistributary bay deposits overlie the nonmarine beds and comprise about 15 m of section. Extensive vegetated sand flats, shoals, and shallow channels overlain by shallow bay deposits (less than 7 m deep), containing storm-generated strata characterize the marginal marine beds. Abundant bioturbation and roots characterize the stratigraphic lowest bay deposits; bioturbated sediment, pelecypods, barnacles, and benthic microfossils are found in the overlying bay storm deposits. The sediments abruptly change upward from hummocky cross-stratified bay deposits to a muddy marsh deposit containing shallow organic-rich channels to prograding nonmarine to marginal marine beds.Transgressive, abundantly fossiliferous shallow-marine strata more than 13 m thick comprise the uppermost exposures at Ocean Point. The marine beds overlie nonmarine and bay strata and represent an environment dominated episodically by storms. The age of the marginal marine and marine beds is late Maastrichtian based on pollen.
 
Article
One-hundred-and-ten angiosperm pollen taxa have been found in upper Campanian to Masstrichtian rocks of the Colville River region, North Slope of Alaska. These are the highest paleolatitude Campanian and Maastrichtian floras known from North America. Total angiosperm pollen diversity rose during the Campanian and declined toward the end of the Maastrichtian. However, anemophilous porate pollen of the Betulaceae-Myricaceae-Ulmaceae complex increased gradually in diversity during the late Campanian and Maastrichtian and into the Paleocene. Turnover of angiosperm taxa was active throughout most of late Campanian and Maastrichtian time; rapid turnover affected mainly the taxa of zoophilous herbs, representing an bundant but ecologically subordinate element of the vegetation. Last appearances of pollen taxa during the late Campanian and Maastrichtian probably represented mainly extinctions rather than emigrations; end- Cretaceous angiosperm extinctions in the North American Arctic began well before the Cretaceous-Tertiary boundary event. The last appearances in the late Maastrichtian took place in bursts; they appear to represent stepwise rather than gradual events, which may indicate the existence of pulses of climatic change particularly in late Maastrichtian time.
 
Article
Cretaceous dinosaurs are recorded for the first time from southwestern Alaska by a series of three tracks found in Aniakchak National Monument. This trackway is in the Upper Cretaceous (Campanian–Maastrichtian) Chignik Formation, a cyclic sequence of marine to non-marine clastic sedimentary rocks. The nearest coeval locality is approximately 1500 km northeast of this site, along the Colville River in northern Alaska, which contains abundant dinosaurs. This distance helps to document the occurrence of a widespread Cretaceous Arctic terrestrial ecosystem that supported significant numbers of large-bodied herbivores.
 
Article
Fossil Psocoptera belonging to the family Empheriidae preserved in the Cretaceous amber of Alava, northern Spain, comprise three new species belonging to two new genera. These are described and illustrated as Empheropsocus arilloi gen. et sp. nov., Empheropsocus margineglabrus sp. nov. and Preempheria antiqua gen. et sp. nov. The relationships between Cretaceous and Oligocene (Baltic amber) Empheriidae are discussed. Diagnostic characters for the family Empheriidae are provided and compared with those of the most closely related families within the Atropetae. A key for the identification of the species of Empheriidae is included.
 
Article
The fluviatile, Whitemud Formation in Alberta and Saskatchewan has yielded Azolla and Ghoshispora megaspores. Associated with these aquatic fern spores are seed cuticles of Costatheca, Spermatites and Carpotheca exhibiting several similarities with the extant families Butomaceae, Juncaceae and Typhaceae respectively. One sample from the Whitemud Formation at Eastend in the Cypress Hills yielded a palynomorph assemblage comparable with the Wodehouseia spinata Zone of the Red Deer River Valley in Alberta. Major pollen species of this assemblage are W. spinata, Aquilapollenites delicatus var. collaris and Kurtzipites trispissatus. A similar assemblage occurs in the Whitemud Formation of southern Saskatchewan. The fining upward Whitemud sequence was deposited by meandering streams in a continental, subtropical to warm temperate climate.
 
Article
Erosional surfaces are present in middle and upper Coniacian rocks in Montana and Alberta, and probably at the base of the middle Santonian in the Western Interior of Canada. These erosional surfaces are biostratigraphically constrained using inoceramid bivalves and ammonites, which are used to define lower, middle, and upper substages of both the Coniacian and Santonian stages of the Upper Cretaceous in this region. The most detailed biostratigraphy associated with these erosional surfaces concerns the MacGowan Concretionary Bed in the Kevin Member of the Marias River Shale in Montana, where the bed lies disconformably on middle or lowermost upper Coniacian strata, and is overlain by upper Coniacian beds. Surface and subsurface investigations in west-central Alberta reveal that the Bad Heart Formation, bounded by unconformities, is about the age of the MacGowan Concretionary Bed. Coniacian and Santonian strata are present elsewhere in Alberta and adjoining areas, but little has been published concerning the Santonian megafossils.
 
Top-cited authors
Fernando E Novas
  • Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"
Andy Gale
  • University of Portsmouth
Silke Voigt
  • Goethe-Universität Frankfurt am Main
Martin Ezcurra
  • Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"
Federico Agnolin
  • Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"