Maastrichtian Time Research Articles

Glabrobournonia Morris and Skelton (Rudist, Bivalvia) from the Campanian–Maastrichtian of Türkiye: Taxonomy, palaeoecology and palaeobiogeography

A re-examination of the specimens described as Bournonia anatolica Özer and Bournonia sp. from central and southeastern Anatolia, Türkiye reveals that they have diagnostic characteristics of the genus Glabrobournonia Morris and Skelton. New rudist material from the middle Campanian to late Maastrichtian mixed siliciclastic-carbonate sequences in the Sakarya Zone (Eastern and Central Pontides), in the east of the Anatolid–Tauride Block and in southeastern Anatolia (north of the Arabian Platform) in Türkiye also showed the occurrence of Glabrobournonia anatolica (Özer) and Glabrobournonia arabica Morris and Skelton. Glabrobournonia anatolica is characterised by a large, rectangular right valve with pronounced growth lamellae, a salient ventral carina and interband, a less salient dorsal carina, a concave indentation anterior band, a slightly concave posterior band and broad and smooth anterior surface as well as the absence of radial ribbing and ligamentary infolding. Glabrobournonia arabica has the diagnostic features of the species, such as small valves, conical right valves with a smooth surface, ventral and dorsal carinae and two concave indentations of anterior and posterior bands separated by an interband. The palaeoecological characteristics of these lateral clinger morphotypes are presented according to growth geometries. For the cosmopolitan genus Glabrobournonia, two main migration routes have been proposed for the Campanian–Maastrichtian time: one along the southern margin of the Tethys from the United Arab Emirates–Oman border region to the Zagros (Iran) and southeastern Anatolia, connecting to the northern margin of the Tethys to the Anatolid–Tauride Block and the Sakarya Zone in Türkiye, and another from the United Arab Emirates–Oman border region to the Zagros Zone (Iran) and the Tarim Basin, connecting the northern and southern margins of the eastern Tethys.

A new late-diverging non-hadrosaurid hadrosauroid (Dinosauria: Ornithopoda) from southwest China: Support for interchange of dinosaur faunas across East Asia during the Late Cretaceous

A non-hadrosaurid hadrosauroid, Qianjiangsaurus changshengi gen. et sp. nov., is named and described here based on an incomplete, partially articulated skeleton from the top of the Upper Cretaceous Zhengyang Formation in Qianjiang District, Chongqing Municipality, southwest China. The skeleton displays a transitional morphology between non-hadrosaurid hadrosauroids and hadrosaurids. The diagnosis of the taxon is therefore defined as a unique combination of characters, including a series of plesiomorphic features typical of non-hadrosaurid hadrosauroids, some apomorphic features common among hadrosaurids but rarely reported in non-hadrosaurid hadrosauroids, and a probable autopomorphy, namely the fan-shaped prepubic process of the pubis strongly anteroposteriorly constricted and dorsoventrally expanded, with the length/height ratio of ∼0.79. Phylogenetic analysis recovers a sister-taxon relationship between Qianjiangsaurus and Plesiohadros outside of Hadrosauridae, and the clade consisting of the two taxa is positioned higher on the tree than Gobihadros and Gilmoreosaurus, but below the clade of Telmatosaurus + Tethyshadros, Eotrachodon and Zhanghenglong. Combining the morphological data with the phylogenetic topology identifies Q. changshengi as a late-branching non-hadrosaurid hadrosauroid. Given that the age assemblage of the eight hadrosauroids closely related to Qianjiangsaurus in phylogeny spans the Santonian–early Maastrichtian time interval, the top of the Zhengyang Formation, from which Qianjiangsaurus is recovered, is possibly restricted to the late Late Cretaceous in age. Hierarchical clustering of twelve hadrosauroid-bearing dinosaur assemblages from the Late Cretaceous deposits of Asia shows a strong correlation between the Zhengyang Formation and the Djadokhta and Baruungoyot formations in Mongolia that supports coeval interchange of dinosaur faunas across East Asia.

Upper Cretaceous Crustacea from Central Cuba

We report new occurrences and additions to previously described species of decapod crustaceans from the Late Cretaceous (Campanian-Maastrichtian) of Cuba. Three of the eight species herein described and illustrated were published previously: Vegaranina rivasi Arano-Ruiz et al.2018; Graptocarcinus collinsi Vega et al., 2020; and Icriobranchiocarcinus rodas Vega et al., 2021; however additional specimens are included. New records include one indeterminate lobster, two new genera and three new species of raninoids, and the first report of Ophthalmoplax cf. O. brasiliana Maury 1930 from Cuba. The most numerous specimens correspond to raninoids, which although not complete, can be described based on complementary pieces of the dorsal carapace and front, and they are assigned as follows: Aguadites hexagranula Vega, Garassino, Nyborg, and Pasini n. gen. sp.; Rodanina monosensis Vega, Garassino, Nyborg, and Pasini n. gen et sp., and Raninoides granulofrons Vega, Garassino, Nyborg, and Pasini n. sp., which represents the oldest record for the genus. Vegaranina rivasi is compared to V. precocia (Feldmann, Vega, Tucker, García-Barrera and Avendaño, 1996) from the Maastrichtian of Chiapas, Mexico, confirming different characters to keep both species as representatives of Vegaranina Van Bakel, Guinot, Artal, Fraaije and Jagt 2012a. The astacid lobster is represented by one isolated carapace (part and counterpart), preserved in a concretion. Two complete dorsal carapaces (one preserving the right cheliped) of Graptocarcinus collinsi represent additional information on the morphology of this species. An incomplete specimen of Ophtalmoplax cf. O. brasiliana, confirms the extensive distribution of this species during Maastrichtian times in the Atlantic shallow marine environments, from Brazil to North Carolina, USA, representing the missing link of the distribution to be found in the Caribbean province. A dorsal carapace is assigned to Icriobranchiocarcinus rodas , since it shows the typical transverse ridges of the species. This report represents an important addition to the knowledge of the Cretaceous crustaceans from Cuba and the Caribbean, confirming that this paleobiogeographic province was composed by a quite different assemblage from those reported from the same age (Campanian-Maastrichtian) of nearby regions such as NE Mexico, SE USA and NE South America.

New remains of Mosasauroidea (Reptilia, Squamata) from the Upper Cretaceous (Santonian) of Aude, southern France

New mosasaurid remains (Squamata) were collected from various Santonian localities in the Sougraigne area (Aude Department, southern France). Cranial bones, some vertebrae, two scapulae and a phalanx are assigned to the plioplatecarpine Platecarpus cf. tympaniticus, while pelvic bones, two vertebrae and a femur (?) are referred to Tylosaurus sp. Tooth marks made by sharks, teleosts or mosasaurids are observed on the mosasaurid vertebrae. These Santonian (86.3–83.6 Ma) Platecarpus occurrences, known since almost one century, are the oldest from Europe. This deposit also yielded some elasmobranch teeth, belonging to taxa such as Squalicorax kaupi, Cretoxyrhina mantelli, Cretolamna sp. and Polyacrodus brabanticus. A review of plioplatecarpine palaeobiogeographical distribution through Late Cretaceous suggests that it follows that of other mosasaurid clades, reaching a worldwide distribution by Maastrichtian time, probably favored by marine routes largely opened at this time.

Late Maastrichtian (latest Cretaceous) Ammonoids from the Naiba Area, Southern Sakhalin, Russian Far East

Six early late Maastrichtian (Late Cretaceous) ammonoid taxa are reported from the Krasnoyarka Formation of the Yezo Group in the Naiba area, southern Sakhalin, Russian Far East. These taxa are grouped into “immigrant species”, i.e., those that migrated from other regions (Pachydiscus subcompressus, Anagaudryceras mikobokense, Gaudryceras seymouriense and Zelandites varuna) and “indigenous species” with a North Pacific distribution (Anagaudryceras matsumotoi). It is unclear to which group Tetragonites sp. belongs. Zelandites varuna and G. seymouriense occur in both the lower upper Maastrichtian as well as the upper lower Maastrichtian in southern Sakhalin, but they have never been found in the middle Maastrichtian. The appearance of these two species in the cold-water regions, i.e., North Pacific and Antarctic, as well as intermediate southern mid-latitudes regions suggests that cooling events occurred during the late early and early late Maastrichtian in the Northwest Pacific region. Their disappearance during the middle Maastrichtian may indicate that the Northwest Pacific region was affected by the greenhouse Middle Maastrichtian Event (MME). This hypothesis suggests that the influx (e.g. P. subcompressus and A. mikobokense) and reappearance (e.g. Z. varuna and G. seymouriense) of many immigrant species into the Northwest Pacific region during late Maastrichtian time may have been associated with the post-MME cooling.

Brachiopod extinctions in the Upper Cretaceous to lowermost Tertiary chalk of Northwest Europe

The white monotonous chalk from the Upper Cretaceous-lowermost Tertiary of Northwest Europe spans at least 24 million years and contains a rich, well preserved fauna of minute brachiopods. Based on taxonomical range charts and time-specific diversities this fauna is studied in terms of mean species longevity, rate of species origin and rate of extinction. The brachiopod fauna initially appears to have colonized the chalk sea in mid-Coniacian times. From there on there is a slow build-up of species diversity reflecting a gradual niche diversification of the chalk. A climax in adjustment and evolutionary stability is reached in Late Maastrichtian time. During the Coniacian-Maastrichtian interval mean rate of extinction is low (0.07 My-1) and mean rate of origination equally low (0.10 My-1). A sudden mass extinction at the Maastrichtian-Danian boundary, however, eliminated more than 70 per cent of the species. The most specialized species, in particular the secondarily free-lying species, apparently became extinct at the boundary. Only six species are known to cross the Maastrichtian-Danian boundary. These are all relatively featureless, non-specialized forms and gave, together with possible survivors in basin margin areas, rise to a rapidly formed highly diverse Early Danian fauna through adaptive radiation. The Early Danian fauna differs in taxonomic composition from the Maastrichtian fauna both on species as well as on higher levels. A dichotomous classification of extinction seems real for the brachiopods from the chalk as their mass extinction at the Maastrichtian-Danian boundary both quantitatively and qualitatively differ from their Late Cretaceous background extinction.

Taxonomy and paleobiogeographic implication of Glabrobournonia Morris and Skelton (Hippuritida, Radiolitidae) from the Late Cretaceous Yigeziya Formation, southwestern Tarim Basin

A re-examination of the specimens that were identified as Biradiolites minor Pojarkova from the late Campanian to early Maastrichtian middle member of the Yigeziya Formation of southwestern Tarim Basin reveals that they should be assigned to the genus Glabrobournonia Morris and Skelton. Glabrobournonia is a genus of radiolitids characterized by indented radial bands, salient ridges on the shell margins and absence of fine ribs on the surface of the right valve. Apart from southwestern Tarim Basin, Glabrobournonia minor (Pojarkova) has also been recorded from the late Campanian of Fergana and Alai basins. The central Asian, late Campanian to early Maastrichtian G. minor differs from the late Campanian to Maastrichtian, eastern Arabian type species Glabrobournonia arabica Morris and Skelton in the flat left valve and an additional fourth ridge on the junction of the dorsal and posterior sides of the right valve. Biradiolites ingens (Des Moulins) could be the direct ancestor of Glabrobournonia. The paleogeographic distribution of Glabrobournonia suggests that this genus dispersed to central Asia from the late Campanian time, becoming widely distributed in the eastern Tethyan region rather than endemic to eastern Arabia. Correspondingly, specimens belonging to Gyropleura yielded from the same bed as G. minor in southwestern Tarim Basin, are similar to the specimens which were attributed to the eastern Arabian Gyropleura sp.; Campanian to early Maastrichtian Osculigera specimens described from the Yigeziya Formation are comparable with those known from the Campanian–Maastrichtian of Iran, Afghanistan and eastern Arabia. The similarity of the rudist assemblages between central Asia and eastern Arabia suggests a faunal connection and affinity between the north and south margins of the eastern Tethyan realm during Campanian to early Maastrichtian times.

Lithological and geochemical characteristics and paleoclimatic conditions of the origin of Upper Cretaceous deposits of the epicontinental basin of the Russian plate in the region of the Ulyanovsk-Saratov foredeep

The results of a geochemical study and paleogeographic, paleoclimatic interpretation for a cyclically constructed section of upper Cretaceous deposits near Volsk city, Saratov region, are presented. Elementary formation cyclites and cyclic variations of a number of certain parameters were associated with the Milankovich astronomical-climatic cycles. The curves of changes of paleotemperature, humidity, paleobathymetry were compiled. The results obtained give an idea of the migration of the arid belt boundaries in the upper Cretaceous and the overall climatic zonation, which is important for regional and global paleoclimatic reconstructions, as well as the history of the development of shelf seas that covered the Russian plate (especially Ulyanovsk-Saratov trough). Paleotemperatures of the land surface in the denudation areas are obtained from the chemical index of alteration (CIA). In the Turonian-Campanian interval selected climatic cyclicity, including period of relative cooling (Turonian–Coniacian) with paleotemperature about 20 °С, the period of relative warming in the mid-late Campanian (20–24 °С), the cooling time at the end of the late Campanian (19–21 °С) and the period of warming at the turn of the Campanian and Maastrichtian and in the early Maastrichtian time. In Maastrichtian age, there are two climatic cycles, beginning with a time of relative cooling (about 19 °С) and ending with a time of relative warming (about 20 С, at the end of Maastrichtian to 25 °С). The cycles of climate humidity change are also determined: two cycles in Campanian time, three cycles in early Maastrichtian, and one cycle in late Maastrichtian. The boundary of the early and late Maastrichtian corresponds to the change of arid conditions to humid ones. The paleobatimetry curves show transgressive-regressive cycles: one in the late Turonian-Coniacian time, two in the late Campanian time, five in the early Maastrichtian time, and one in the late Maastrichtian time. Depth variations were estimated: in the Turonian-Coniacian time in the range of 70–80 m, in the Campanian-Maastrichtian time, the paleobatimetry consistently increased and changed from 100 to 200 m (on average about 150 m). The results obtaired give and idea of the migration of the boundaries of the arid belt in the Late Creataceous and main features of the climatic zonation, which is important for regional and global paleoclimatic reconstructions, as well as for the history of the development the Russian plate in the Ulyanovsk-Saratov region.

The closure of the Vardar Ocean (the western domain of the northern Neotethys) from the early Middle Jurassic to the Paleocene time, based on the surface geology of eastern Pelagonia and the Vardar zone, biostratigraphy, and seismic-tomographic images of the mantle below the Central Hellenides.

Seismic tomographic images of the mantle below the Hellenides indicate that the Vardar Ocean probably had a composite width of over 3000 km. From surface geology we know that this ocean was initially located between two passive margins: Pelagonian Adria in the west and Serbo-Macedonian-Eurasia in the east. Pelagonia was covered by a carbonate platform that accumulated, during Late Triassic to Early Cretaceous time, where highly diversified carbonate sedimentary environments evolved and reacted to the adjacent, converging Vardar Ocean plate. We conceive that on the east side of the Vardar Ocean, a Cretaceous carbonate platform evolved from the Aptian to the Maastrichtian time in the forearc basin of the Vardar supra-subduction volcanic arc complex. The closure of the Vardar Ocean occurred in one episode of ophiolite obduction and in two episodes of intra-oceanic subduction. 1. During the Middle Jurassic time a 1200-km slab of west Vardar lithosphere subducted beneath the supra-subduction, 'Eohellenic', arc, while a 200-km-wide slab obducted onto Pelagonia between the Callovian and Valanginian times. 2. During the Late Jurassic through to the Cretaceous time a 1700-km-wide slab subducted beneath the evolving east Vardar-zone arc-complex. Pelagonia, the trailing edge of the subducting east-Vardar Ocean slab, crashed and underthrust the Vardar arc complex during the Paleocene time and ultimately crashed with Serbo-Macedonia. Since the late Early Jurassic time, the Hellenides have moved about 3000 km toward the northeast while the Atlantic Ocean spread.

Albanerpetontids (Lissamphibia, Albanerpetontidae) from the Aguja Formation (lower Campanian) of West Texas, USA

The Lowerverse local fauna of West Texas, USA, preserves a rare, early Campanian assemblage of microvertebrates from Laramidia. The recovery of 137 fragmentary specimens reveals that albanerpetontids were locally abundant here and also widespread throughout much of the Western Interior of North America by early Campanian time. Both gracile- and robust-snouted species are represented within the assemblage. Among these, the occurrence of Albanerpeton nexuosum is consistent with its occurrence in paracontemporaneous deposits elsewhere in the Western Interior. The referral of two specimens to Albanerpeton sp., cf. Albanerpeton galaktion, strongly suggests that this long-lived taxon was far more widespread during the early Campanian than previously known and its likely occurrence in West Texas represents a significant geotemporal range extension for the species. However, Albanerpeton gracile is seemingly restricted to Judithian “age” deposits in North America and was not identified at Lowerverse. The Lowerverse assemblage supports the current paradigm involving the occurrence of these three named albanerpetontids during middle Campanian – Maastrichtian time in the Western Interior of North America.

Unravelling the widening of the earliest Andean northern orogen: Maastrichtian to early Eocene intra‐basinal deformation in the northern Eastern Cordillera of Colombia

AbstractThe onset of deformation in the northern Andes is overprinted by subsequent stages of basin deformation, complicating the examination of competing models illustrating potential location of earliest synorogenic basins and uplifts. To establish the width of the earliest northern Andean orogen, we carried out field mapping, palynological dating, sedimentary, stratigraphic and provenance analyses in Campanian to lower Eocene units exposed in the northern Eastern Cordillera of Colombia (Cocuy region) and compare the results with coeval succession in adjacent basins. The onset of deformation is recorded in earliest Maastrichtian time, as terrigenous detritus arrived into the basin marking the end of chemical precipitation and the onset of clastic deposition produced by the uplift of a western source area dominated by shaly Cretaceous rocks. Disconformable contacts within the upper Maastrichtian to middle Palaeocene succession document increasing supply of quartzose sandy detritus from Cretaceous quartzose rocks exposed in eastern source areas. The continued unroofing of both source areas produced a rapid shift in depositional environments from shallow marine in Maastrichtian to fluvial‐lacustrine systems during the Palaeocene‐early Eocene. Supply of immature Jurassic sandstones from nearby western uplifts, together with localized plutonic and volcanic Cretaceous rocks, caused a shift in Palaeocene sandstones composition from quartzarenites to litharenites. Supply of detrital sandy fragments, unstable heavy minerals and Cretaceous to Ordovician detrital zircons, were derived from nearby uplifted blocks and from SW fluvial systems within the synorogenic basin, instead of distal basement rocks. The presence of volcanic rock fragments and 51–59 Ma volcanic zircons constrain magmatism within the basin. The Maastrichtian–Palaeocene sequence studied here documents crustal deformation that correlates with coeval deformation farther south in Ecuador and Peru. Slab flattening of the subducting Caribbean plate produced a wider orogen (>400 km) with a continental magmatic arc and intra‐basinal deformation and magmatism.

FISH OTOLITHS FROM THE LATE MAASTRICHTIAN KEMP CLAY (TEXAS, USA) AND THE EARLY DANIAN CLAYTON FORMATION (ARKANSAS, USA) AND AN ASSESSMENT OF EXTINCTION AND SURVIVAL OF TELEOST LINEAGES ACROSS THE K-PG BOUNDARY BASED ON OTOLITHS

Otolith assemblages have rarely been studied across the K-Pg boundary. The late Maastrichtian Kemp Clay of northeastern Texas and the Fox Hills Formation of North Dakota, and the early Danian Clayton Formation of Arkansas therefore offer new insights into how teleost fishes managed across the K-Pg boundary as reconstructed from their otoliths. The Kemp Clay contains 25 species, with 6 new species and 2 in open nomenclature and the Fox Hills Formation contains 4 species including 1 new species. The two otolith associations constitute the Western Interior Seaway (WIS) community. It contains the earliest unambiguous representatives of the Gadiformes (cods and hakes) and the Heterenchelyidae (mud eels). The WIS community differs significantly from other Maastrichtian otolith assemblages previously studied from Mississippi and Maryland, which constitute the Appalachian community, with only 4 shared species (similarity percentage of 7.3%) between both communities. The difference is interpreted to be related to cold-water influence in the WIS community, which may have still been connected to the Arctic Basin, and to the depostional environment (muddy bottom) in the Kemp Clay. The Kemp Clay is unusually rich in taxa that survived the end-Cretaceous extinction event and are still present in the Danian of the Clayton Formation, or, as the case may be, in the Danian and Selandian of the boreal northern European community known from Denmark. Approximately 54% of all otolith-based teleost species identified from the Maastrichtian WIS community survived the K-Pg boundary event (versus 11-12% in other communities) and 73% of the genera (versus 40-50% in other communities). The early Danian Clayton Formation contains an impoverished inherited association with 14 species, of which 11 are survivors from late Maastrichtian times, 1 species is new, and 2 remain in open nomenclature. This compares to a significantly higher degree of newly evolved species in only slightly younger faunas from the middle to late Danian and Selandian of Europe indicating an initially slow pace of recovery. The observed differences in survival and the composition of survived and extinct taxa are discussed in the light of the ongoing discussions concerning the consequences and effects that led to the end-Cretaceous extinction event commonly thought to have been caused by a large meteorite impact. In our assessment, an ‘impact winter’ could have had a major influence on the live cycle of tropical to subtropical fishes while perturbations in the pelagic food web or ocean surface acidification might have had a minor and more selective effect. Overall, teleost fishes were significantly affected by the end-Cretaceous mass extinction, but to a much lesser extent than in many other biota. This study provides more evidence of the importance of Late Cretaceous otolith assemblages in the USA for interpreting teleostean evolution. The newly described taxa are: Elopothrissus carsonsloani n. sp., Pythonichthys arkansasensis n. sp., Congrophichthus transterminus n. gen., n. sp., Rhynchoconger brettwoodwardi n. sp., Palaeogadus weltoni n. sp., Dakotaichthys hogansoni n. gen., n. sp., and Ampheristus americanus n. sp.

Cretaceous magmatic evolution in the Deylaman igneous complex, Alborz zone, Iran: change from extensional to compressional regime

The Deylaman igneous complex, as a part of the Late Cretaceous rock unit that lies behind the Paleogene Alborz magmatic arc, in the northern Alborz zone, is composed of basaltic sheet lavas alternating with the pelagic calcareous sediments, basaltic pillow lavas, felsic lavas and gabbroic-monzodioritic intrusions. The pelagic calcareous deposits contain microfossils representing the Santonian–Maastrichtian ages. Furthermore, petrographic textures such as the hyalomicrolitic texture and swallow-tail plagioclase crystals in the pillow lavas, and also segregation vesicles in the basaltic sheet lavas, imply high external (hydrostatic) pressures as the magma was extruded in a deep-water environment. The rock samples show both compositional bimodality and characteristic trends in the variation diagrams. Also, some geochemical characteristics imply that the basaltic lavas originated from the partial melting of an undepleted deep mantle source containing spinel lherzolite: the enrichment patterns of LREE/HREE ratios of the samples [(La/Yb)n = 3.93–4.16 for basaltic lavas and 10.92 for felsic lavas] lying between those characteristic of OIBs [(La/Yb)n = 12.92] and EMORBs [(La/Yb)n = 1.91]; similarities between the patterns of multi-element spider-diagrams; LILE bulges in the basaltic samples compared with those of OIBs. Moreover, the samples show influence from two geotectonic environments: supra-subduction zone (SSZ) settings and plume-type within-plate magmas. Therefore, because of the deep submarine environment inferred for the effusive volcanic eruptions in Santonian–Maastrichtian time, it seems that the Deylaman igneous complex evolved through two stages: first, a tensional regime in a supra-subduction zone (farther from the Mesozoic magmatic arc) and formation of an embryonic rift-related oceanic basin in the Late Jurassic–Early Cretaceous; secondly, a compressive regime in the Late Cretaceous–Early Paleocene and inland migration of the magmatic arc. Consequently, the Cretaceous magmatism can be interpreted as a prelude to the Eocene magmatic flare-up in the magmatic arcs of Iran.

Benthic foraminifera of the Maastrichtian sediments from the Maliboğazi (Kalecik, Ankara) and Irmak (Kırıkkale) areas in Türkiye

The investigation focuses on benthic foraminifera and their paleoecology, particularly on the Orbitoides genus in the Maaastrichtian sediments from the northern and western Ankara City (Turkey). The hard and soft rock samples from two measured sections, namely as Malibogazi (N Ankara) and Daryaka-Irmak (W Ankara, Kirikkale) were evaluated. More than one hundred equatorial and axial sections of the Orbitoides genus were prepared. The benthic foraminifera of the Maastrichtian sediments are as follows: Dorothia sp., Marssonella sp., Lenticulina sp., Saracenaria sp., Oolina sp., Cibicides sp., Gavelinella sp., Orbitoides apiculatus, O. gruenbachensis, O. medius, Pseudomphalocyclus sp., Omphalocyclus macroporus, Lepidorbitoides sp., Sirtina sp., Sulcoperculina globosa, S. vermunti, Siderolites calcitrapoides, Laffitteina mengaudi, Laffitteina sp. In the Malibogazi area, biometric data based on the internal and external parameters of the Orbitoides genus present reliable interpretations for paleoecological approaches of the Maastrichtian time. The calcareous siliciclastics comprise abundant Orbitoides apiculatus and O. gruenbachensis species. We have identified two ichnospecies as Maeandropolydora osmaneliensis and Curvichnus semorbis in the Orbitoides tests. It is thought that meandered microboring activity are related to parasitic life modes while cave shaped ones are associated with hermit type life modes. Orbitoides bearing siliciclastics overlies reefal sediments including biostromal limestones with rich rudist fauna, Thalassoniodes rich carbonates and massive, thick bedded limestones in the Maliboğazi area. In contrast, siliciclastics indicating open sea sediments outcrop widespreadly in the Irmak area. The obtained stratigraphical, sedimantological and paleontological data show that northern part of the Ankara was shallower than western part of the Ankara during the late Maastrichtian.

CONTROLS ON FRACTURE FLOW POTENTIAL IN A TIGHT CARBONATE RESERVOIR: SAYINDERE FORMATION (CAMPANIAN), WEST ADIYAMAN BASIN, SE TURKEY

Identifying controls on the permeability of fluid‐conductive fractures is critical in tight reservoirs, but this is challenging in tectonically complex regions such as foothills belts where there may have been multiple stages of deformation and fracturing. Fracture permeability depends on fracture aperture and connectivity, both of which are affected by tectonism and cementation. Among the many factors that control the cementation history, oil charging may play an important role. Important challenges in studies of fractured reservoirs in tectonically complex regions include determining the timing (and intensity) of fracturing events relative to that of the oil charge, verifying the presence of matrix storage, and establishing the fracture cementation history.This paper reports on a comparative fracture study of four small‐scale oilfields in the west Adıyaman Basin, located within the foothills belt of the Tauride suture zone in SE Turkey. Here the tight reservoir carbonates of the Sayındere Formation (Campanian) were subjected to repeated phases of structural deformation. Major deformation phases took place in Campanian and Maastrichtian times, before oil charging into the reservoir began in the Eocene; and in the Late Eocene – Oligocene and Late Miocene, after the oil charge. Fractures that were generated before oil emplacement appear to have been cemented or partially cemented by calcite as indicated by cross‐cutting cemented fractures on borehole images. Partially‐cemented fractures in cores are oil‐stained with cement‐lined walls, suggesting cementation began before oil emplacement but was not completed. Image logs and cores also show the presence of clean, open fractures with no cement present on the walls. These open fractures cut across the cemented or partially‐cemented fractures, and are in general related to Late Miocene compressional folding. Open fracture density is correlated to Late Miocene fold curvature and asymmetry in the four oilfields studied. Of these fields, the Șambayat structure is the tightest and most asymmetric anticline and hence has the maximum open fracture density; this field also has the highest oil potential.Although the available data is not sufficient to evaluate the effects of oil charging on fracture cementation definitively, the observations are consistent with a model that oil charge into the fractured Sayındere Formation carbonates inhibited or slowed calcite cementation. Hence fracturing of a carbonate reservoir after oil emplacement may significantly enhance the fracture permeability, and may even render a tight reservoir prospective.

Cretaceous paleomargin tilted blocks geometry in northern Tunisia: stratigraphic consideration and fault kinematic analysis

New stratigraphic data, lithostratigraphic correlations, and fault kinematic analysis are used to discuss the basin geometry and sedimentation patterns of the northeastern Tunisia during Cretaceous times. Significant facies and thickness variations are deduced along the northeastern Atlas of Tunisia. The NW-SE 80-km-long regional correlation suggests a high sedimentation rate associated with irregular sea floor. The fault kinematic analysis highlights N-S to NE-SW tectonic extension during Early Cretaceous. During Aptian–Albian times, an extensional regime is recognized with NE-SW tectonic extension. The Cenomanian–Turonian fault populations highlight a WNW-ESE to NW-SE extension, and Campanian–Maastrichtian faults illustrate an NW-SE extension. The normal faulting is associated to repetitive local depocenters with a high rate of sedimentation as well as abundant syntectonic conglomeratic horizons, slump folds, and halokinetic structures. The sequence correlation shows repetitive local depocenters characterizing the basin during Early Cretaceous times. All the above arguments are in favor of basin configuration with tilted blocks geometry. This geometry is shaped by major synsedimentary intra-basin listric normal faults, themselves related to the extensional setting of the southern Tethyan paleomargin, which persisted into the Campanian–Maastrichtian times. The results support a predominant relationship between tilted blocks geometry and sedimentation rather than E-W “Tunisian trough” as it was previously accepted.

A Maastrichtian birth of the Ancestral Mississippi River system: Evidence from the U-Pb detrital zircon geochronology of the McNairy Sandstone, Illinois, USA

Sediment dispersal patterns are integral to the understanding of Cretaceous paleogeography and tectonics. Detrital zircon U-Pb geochronology of fluvial/deltaic sandstones of the Maastrichtian (∼70 Ma) McNairy Sandstone (s = 5, n = 1458) at the northern end of the Mississippi Embayment documents the initiation of south-flowing drainage in the Laurentian midcontinent. The detrital zircon age spectra of the McNairy Sandstone include zircons from the Superior (>2.5 Ga), Penokean (1.8–1.9 Ga), Yavapai-Mazatzal (1.6–1.8 Ga), Midcontinent Granite-Rhyolite (1.3–1.5 Ga), Grenville (980–1300 Ma), and Taconic-Acadian (350–450 Ma) provinces. Grenville zircons account for 74% of the age spectrum. Taconic-Acadian grains also are important, comprising ∼10% of the age spectrum. The McNairy DZ age spectra are statistically indistinguishable from uppermost Pennsylvanian strata (i.e. the later Des Moinesian Copperas Creek Sandstone) in the Illinois Basin. These DZ age spectra are also indistinguishable from sands in the Modern Ohio and Tennessee River valleys. Based on this similarity, local Illinois Basin source areas contributed a previously unrecognized volume of sediment to the Mississippi Embayment as early as Maastrichtian time. Our interpretation includes a Cenomanian onset of subsidence in the southern Mississippi Embayment initiated by the rapid opening of the Gulf of Mexico. This subsidence propagated northward, and by the Maastrichtian, the Mississippi Embayment was the drainage axis for an Ancestral Mississippi that is recorded in both the Maastrichtian strata in the northern Mississippi Embayment and the Paleogene deposits in the southern part. Our interpretation shows the integration of an Ancestral Mississippi River occurred by the Maastrichtian, that the river continued through the Paleocene, and subsequently developed into the modern Mississippi River system.

Maastrichtian oil shale deposition on the southern Tethys margin, Egypt: Insights into greenhouse climate and paleoceanography

A comprehensive set of organic and inorganic geochemical proxies, clay mineralogy, and molecular fossils are presented from two biostratigraphically well-dated oil shale horizons of Egypt, within the Upper Cretaceous Duwi and Dakhla formations. The studied oil shales were deposited within intracratonic sedimentary basins in a broad northern African epeiric sea. Calcareous nannofossil biostratigraphy indicates that the oil shales range from early to late Maastrichtian in age, covering nannofossil zones UC18, UC19, and UC20. The oil shales contain smectite and kaolinite as the main clay minerals that formed by weathering of precursor basement rocks. The relative abundances of clay minerals and several geochemical proxies (e.g. C-value, CIA, Ga/Rb, Rb/Sr and Sr/Cu), along with the occurrence of warm-water nannofossil taxa, demonstrate that the Maastrichtian oil shales accumulated under a warm, arid to humid greenhouse climate during a general Maastrichtian cooling trend. This episode of oil shale deposition in Egypt coincided with the first potential imprint of the global warming, that has been recorded during early-to-late Maastrichtian times (~70.6–67.7 Ma). Elevated eolian terrigenous input was recorded within the Duwi Formation oil shales, shown by high Ti/Al, Si/Al, Zr/Al and low La/Lu ratios. The Duwi Formation environment was characterized by enhanced salinity and a stratified water column, compared to that of the Dakhla Formation, shown by elevated values of the gammacerane index, tetracyclic terpane, β‑carotene and Sr/Ba ratio. The CaCO3 content and carbonate/siliciclastic ratio indicate that the Dakhla Formation oil shales were deposited during a relative sea-level rise in a deeper marine setting than the Duwi Formation oil shales. The data further imply a wind-driven upwelling scenario of nutrient inputs that simulated primary production and increased organic matter fluxes. Thus, paleoclimate and paleoceanography had a considerable impact on organic matter enrichment.

Record of calcareous algae from the Lameta Formation: a new insight for possible sea incursion during the Maastrichtian time

The Lameta Formation exposed in central and western India is traditionally considered as deposits of fluvio-lacustrine environment except for the type area having a few reports of shallow marine setting. The present work records the fossilization of calcareous algae from a discontinued bed of limestone preserved in argillaceous unit of Lameta succession. Taxonomical study of algal biota places them mostly in chlorophyta, charophyta, and rhodophyta divisions. These algae are being reported for the first time from Lameta sediments of a newly identified inland basin of deposition, viz., Salbardi-Belkher. Considering the paleoecological significance of presently recorded algae, a marine incursion has been interpreted which might have taken place through the Narmada-Tapti Rift Zone during the Maastrichtian time.

Palynomorphs Distribution, Biostratigraphy and Paleoecology Study of the Superficial Sediments in Parts of Gombe Formation, Upper Benue Trough, Nigeria

Paleoecological conditions of part of Gombe formation of Upper Benue Trough were studied using outcrop samples from 22 sites of 1.5 m deep each. The samples were crushed, standard maceration method employed for analysis and slides prepared. The slides were examined for identification and counting using transmitted light microscope with times one hundred oil immersion objective lenses. The result showed a fairly rich assemblage of palynomorph which includes age diagnostic palynomorphs: Cingulatisporites ornatus, Proteacidites sigalli, Constructipollenites inflectus, Echitriporites trianguliformis, Longapertites microfoveilatus, Monocolpites sp. and Tricolpites sp. which effectively assigned the upper Maastritchtian age to the sequence. Also the abundance of woody and vegetal materials which are land derived in the shales, siltstones and kaolinite rich claystone at the upper part of the sequence studied suggest the prevalence of fresh water conditions. The presence of Ephedripites in some sections of the sequence studied reflects occasional dry conditions. The high abundance of Acrostichum aureum in sample BA-8 signifies flooding of the region in Maastrichtian times by the sea characterized by shallow water depth and restricted ecological circulation which also occurs in mangrove forest and other wetlands.