Uppermost Maastrichtian Research Articles

Cretaceous/Paleogene boundary bathyal paleo-environments in the central North Pacific (DSDP Site 465), the Northwestern Atlantic (ODP Site 1049), the Gulf of Mexico and the Tethys: The benthic foraminiferal record

Uppermost Maastrichtian benthic foraminiferal assemblages (> 63 μm) are diverse, indicating mesotrophic conditions in lower bathyal DSDP Hole 465A (Hess Rise, central North Pacific), in 4 lower bathyal land sections in central-East and Northeastern Mexico, and in the upper to middle bathyal Agost section (Tethys area, Southeastern Spain). They indicate more eutrophic conditions in lower bathyal ODP Hole 1049C (Blake Nose, Northwestern Atlantic). Benthic foraminifers did not suffer significant extinction at the K/Pg boundary, but diversity and heterogeneity of the assemblages and the percentage of infaunal morphogroups decreased drastically in all sections, with the exception of DSDP Hole 465A where the percentage of infaunal taxa increased. These faunal changes probably reflect the effect on the benthic faunas of a widespread decrease in the food supply to the sea floor, as a result of the collapse of primary productivity at the K/Pg boundary. The decrease in food supply apparently affected the benthic faunas least at more eutrophic NW Atlantic ODP Site 1049 and at Pacific DSDP Site 465, which is distal from the impact site of the K/Pg bolide on the Yucatan Peninsula. At these sites the faunas recovered within the Parvulorugoglobigerina eugubina Biozone (∼ 100 ky), although diversity and heterogeneity remained low through the early Danian, possibly indicating environmental stress. This stress might be related to a high or fluctuating food supply by primary producers that could not easily be used by the benthos, such as various bloom species of dinoflagellates. Benthic assemblages recovered more slowly (∼ 300 ky) in the Mexican and Spanish sections. Low oxygen conditions after the K/Pg boundary could be inferred from the benthic assemblages at Agost (Southeastern Spain) only. A short episode of hypoxia, however, may be obscured at Pacific DSDP Hole 465A by drilling disturbance, and in the Mexican sections and Hole 1049C by incomplete sections due to downslope transport. Benthic foraminiferal assemblages thus appear to have been affected by the collapse of primary productivity at the K/Pg boundary to a different extent in different regions, and took different lengths of time for their recovery after the boundary.

Unconformity between the Upper Maastrichtian and Upper Paleocene in the Hakobuchi Formation, north Hokkaido, Japan: a major time gap within the Yezo forearc basin sediments

Cretaceous sediments of the Yezo Group in the Yezo forearc basin-fill are widely distributed along the meridian zone of Hokkaido, Japan. The uppermost part of the Cretaceous sequence, namely the Hakobuchi Formation, ranges in age from Early Campanian to Late Maastrichtian and partly into Late Paleocene. It is subdivided into, in ascending order, the Kamikoma, Heitaro-zawa, Oku-utsunai and Utsunaigawa members in the Nakatonbetsu area, north Hokkaido. Recently, an unconformable sequence boundary was found between the Heitaro-zawa and Oku-utsunai members. A Lower Campanian and two Lower Maastrichtian inoceramid zones are established in the lower half of the Hakobuchi Formation. A lower Upper Maastrichtian ammonite fauna, composed of Anagaudryceras matsumotoi, Pseudophyllites indura and Zelandites varuna, can be recognized above the inoceramid extinction horizon in the upper Heitaro-zawa Member. Although there are no good index megafossils in the two overlying members, Glycymeris shell-beds of the basal Oku-utsunai Member overlie the Upper Maastrichtian Heitaro-zawa Member with a sharp, undulating, erosional surface. As Late Paleocene nannofossils were reported from the two upper members, the uppermost Maastrichtian and Lower Paleocene appear to have been eroded away at the unconformity. The K/Pg gap can be traced into the Oyubari and north Hobetsu areas of central Hokkaido and four drillholes offshore from Honshu in the Pacific Ocean. This might indicate large-scale subaerial erosion caused by a relative sea-level fall throughout the Yezo Basin.

東北日本の白亜系―古第三系蝦夷前弧堆積盆の地質学的位置づけと層序対比

The Cretaceous to Paleocene Yezo forearc basin was developed between the western Early Cretaceous volcanic arc and the eastern Early Cretaceous to Early Eocene accretionary complexes in the northeastern margin of Eurasia Plate. Its sediments are distributed across a 150 km-wide and 1400 km-long belt from Northeast Japan to Sakhalin including off the Pacific coast in north-south direction. It is subdivided into three subbasins on the basis of geologic setting: Hokkaido, Kitakami and Joban subbasins. In the first half of this paper, the tectonic setting is reviewed not only for the better understanding of the basin, but also in order to evaluate the distribution of carbonaceous rocks as source rocks and reservoir sandstone.In the latter half, twenty-seven stratigraphic sections including 4 onshore and 8 offshore boreholes and 15 surface sections are correlated to delineate the sedimentary history and basin evolution through the temporal and spatial distributions of facies successions and depositional sequences. Two second-order shallowing-upward cycles for the Cretaceous are recognized in Hokkaido but are obscure in northern Honshu. Shallow-marine to paralic sediments of the first cycle (early Albian to Turonian) are represented by the Mikasa Formation (late Albian to Turonian) as the western marginal facies in Hokkaido. The Campanian to Maastrichtian shallow-marine and non-marine facies of the second cycle (Coniacian to Maastrichtian) are characterized by the Hakobuchi Formation in the Hokkaido subbasin and its correlatives in the Kitakami and Joban subbasins. The two formations include several third- and fourth-order depositional sequences with coarsening-upward facies successions. The uppermost Maastrichtian to Upper Paleocene interval is missing everywhere in the Yezo basin. Furthermore, two third-order depositional sequences of the late Paleocene (uppermost Hakobuchi Formation) and the uppermost Paleocene to lower Eocene (Haboro Formation) have developed with unconformities in a few areas.

Laffitteina from the Maastrichtian-Paleocene shallow marine carbonate successions of the Eastern Pontides (NE Turkey): biozonation and microfacies

Microfacies and benthic foraminiferal assemblages from the Maastrichtian-Paleocene shallow-marine carbonate successions of the Eastern Pontides (NE Turkey) are described and illustrated. Microfacies comprise fossiliferous intrasparites, packed biomicrites/biosparites, rudistid biosparites, gastropod-biosparites, miliolid biomicrites/biosparites, coralline algal biosparites and intrabiosparites. Dolomite horizons occur in the Maastrichtian-Danian and Lower-Upper Paleocene transitions. Microfacies and microfossil content indicate deposition in shallow marine to lagoonal environments all within same sedimentary basin. The Shallow Benthic Foraminiferal Zonal (SBZ) Scheme proposed for the Tethyan Paleogene is tested on Eastern Pontian material. It cannot be applied to the Paleocene in the Eastern Pontides due to the presence of the large number of endemic taxa, and variable stratigraphic ranges of some benthic foraminifera. Various species of Laffitteina have been used to produce a biozonation through the Maastrichtian-Thanetian. Laffitteina marsicana FARINACCI and Laffitteina oeztuerki INAN occur in the lower and upper parts of the Upper Maastrichtian, respectively. Laffitteina turcica INAN occurs in the uppermost Maastrichtian. Laffitteina bibensis MARIE appears in the Lower Paleocene (Danian), Laffitteina erki (SIREL) in the Upper Paleocene (Selandian) and they coexist from the Selandian to the lower part of the Thanetian.

Morphometry of selected calcareous nannofossils across the Cretaceous-Paleocene boundary at the Bidart (France) and Elles (Tunisia) sections. Comparison with carbon and oxygen stable isotope ratios

Abstract A detailed biometric analysis of five species of calcareous nannofossils was carried out on samples from the uppermost Maastrichtian and lowermost Danian of Bidart (Basque Country, SW France) and Elles (central Tunisia). This study reveals the existence of two morphotypes of A. cymbiformis and an abrupt reduction of the five species immediately below the K-T boundary, likely in relation with a stressful environment, which would have developed just before the deposition of the iridium level, followed by a sudden size increase in the basal Danian reflecting the reworking pattern of the Cretaceous species. In addition, the comparison of biometric and isotopic data seems to indicate that the two morphotypes of A. cymbiformis have different ecologies, the large one being favoured in cool waters.

Benthic foraminifera and environmental turnover across the Cretaceous/Paleogene boundary at Blake Nose (ODP Hole 1049C, Northwestern Atlantic)

Sediments recovered at lower bathyal ODP Site 1049 on Blake Nose (Northwestern Atlantic) offer an opportunity to study environmental changes at the Cretaceous/Paleogene (K/P) boundary relatively close to the Chicxulub impact structure on the Yucatan peninsula, Mexico. In Hole 1049C, the boundary is located at the base of a 9-cm-thick layer with abundant spherules, considered to be impact ejecta. Uppermost Maastrichtian oozes below, and lowermost Danian pelagic oozes above the spherule-bed contain well-preserved bathyal benthic foraminifera. The spherule-bed itself, in contrast, contains a mixture of shallow (neritic) and deeper (bathyal) species, and specimens vary strongly in preservation. This assemblage was probably formed by reworking and down-slope transport triggered by the K/P impact. Across the spherule-bed (i.e., the K/P boundary) only ∼7% of benthic foraminiferal species became extinct, similar to the low extinction rates of benthic foraminifera worldwide. Quantitative analysis of benthic foraminiferal assemblages and morphogroups in the >63-μm size fraction indicates a relatively eutrophic, stable environment during the latest Maastrichtian, interrupted by a sudden decrease in the food supply to the benthos at the K/P boundary and a decrease in diversity of the faunas, followed by a stepped recovery during the earliest Danian. The recovery was probably linked to the gradual recovery of surface-dwelling primary producers.

Carbon isotope evidence for the timing of the Cretaceous–Palaeogene macrobenthic colonisation at the Agost section (southeast Spain)

The Cretaceous–Palaeogene (K–T) boundary section of Agost (southeast Spain), one of the most complete sections existing, contains a well-developed trace-fossil assemblage, composed of dark- and light-filled trace fossils, registered in the uppermost Cretaceous (Maastrichtian, Plummerita hantkeninoides Biozone) sediments. The trace-fossil assemblage reveals that significant macrobenthic colonisation occurred around the K–T boundary interval. However, difficulties in recognising trace fossils affecting the K–T boundary layer, as well as in biostratigraphically characterising these trace fossils hindered a conclusive interpretation on the timing of this macrobenthic colonisation. With the aim of this characterisation, we determined the δ 13C of the carbonate fraction of dark and light filling materials from the trace fossils, since the carbon isotope compositions of uppermost Cretaceous and lowermost Palaeogene materials are clearly different. The data compiled provide evidence for a significant distinction between light-filled trace fossils, with δ 13C values higher than 1.6‰ PeeDee Belemnite (PDB), and dark-filled trace fossils, with δ 13C values between 0.21 and 1.2‰ PDB, most of these being lower than 0.7‰ PDB. The comparison of these values with those from the uppermost Maastrichtian to the lowermost Danian sediments reveals that the macrobenthic colonisation occurred in different phases across the K–T boundary interval.

Stratigraphic correlation of Upper Cretaceous to Paleocene forearc basin sediments in Northeast Japan: cyclic sedimentation and basin evolution

Cretaceous to Paleocene sediments are distributed across a 200 km-wide and 1400 km-long belt in Northeast Japan to Sakhalin. Twenty-six stratigraphic sections including land-based and offshore drill holes and surface sections are correlated to delineate the sedimentary history and basin evolution of the Yezo forearc basin. Two second-order shallowing-upward cycles are recognized in Hokkaido but are obscure in north Honshu. Shallow-marine to paralic sediments of the first cycle (early Albian to Turonian) are represented by the Mikasa Formation (late Albian to Turonian) as the western marginal facies, while the eustatic curves (e.g. Haq curves) reach the highstand maximum at the late Cenomanian. The Campanian to Maastrichtian shallow- and non-marine facies of the second cycle (Coniacian to Maastrichtian) are characterized by the Hakobuchi Group in Hokkaido and its correlatives in north Honshu. This large-scale shallowing may have reflected directional changes of the Izanagi-Kula plate motion near the early Campanian. The uppermost Maastrichtian to Upper Paleocene is possibly absent everywhere in the basin. The shallow-marine to non-marine facies often show several third-order depositional sequences with upward-coarsening facies successions. They may have been controlled by global eustasy even in an active-margin setting, since the stacking patterns of sequences and the timing of sequence boundaries appear considerably concordant with the oscillation patterns of the Haq curves.

Palynology and palynostratigraphy of Maastrichtian, Paleocene, and Eocene strata in the Denver Basin, Colorado

Palynological analysis provides data for determinations of ages and paleoenvironments of Maastrichtian, Paleocene, and Eocene strata in the Denver Basin. These strata were sampled on the surface at natural and artificial outcrops (construction sites) and in the subsurface via auger, drill core, and well cuttings. Extensive artificial outcrops existed temporarily during construction of the Denver International Airport. The Kiowa core, drilled as part of the Denver Museum of Nature & Science9s Denver Basin Project, is the principal palynostratigraphic reference section for the basin. It is supplemented by data from the Castle Pines core. Palynostratigraphic zonations of the Kiowa and Castle Pines cores are correlated with magnetostratigraphic zonations in the same cores. Regionally known palynostratigraphic biozones are present in the basin, as follows: Aquilapollenites striatus Interval Zone (Maastrichtian) in the Fox Hills and Laramie Formations; Wodehouseia spinata Assemblage Zone (uppermost Maastrichtian) in the lower part of the D1 sequence; Zones P1 through P3 (lower Paleocene) in the upper part of the D1 sequence; Zone P6 (uppermost Paleocene) locally at the base of the D2 sequence; and Zone E (lowermost Eocene) in the D2 sequence, above the basin-wide paleosol unit. The K–T boundary is bracketed by samples from the Kiowa and Castle Pines cores and is located within centimeters at the West Bijou Site. The Paleocene–Eocene boundary is determined to be within the paleosol unit of the Denver Basin, near the base of the D2 sequence. These and other palynological age determinations supplement independent paleobotanical and vertebrate paleontological research in the Denver Basin.

La coupe d'Ouled Haddou (Rif externe oriental) : un affleurement continu de la transition Crétacé–Paléogène au Maroc, révélé par les Foraminifères planctoniques

Abstract In the Ouled Haddou section, deposits of the Uppermost Maastrichtian correspond to the Abathomphalus mayaroensis Biozone. The index species is regularly present until the Cretaceous–Palaeogene boundary, which is marked by a mass extinction affecting 41 species (large and complex). Some Cretaceous small species persist in the Lowermost Danian. The first levels of the Danian are assigned to the Guembelitria cretacea Biozone, in which the species index persist without being affected, and the first species of the Tertiary appear. The upper part of the Lower Danian corresponds to the succession of Parvularugoglobigerina eugubina, Parasubbotina pseudobulloides , and Subbotina triloculinoides Biozones. From the P. eugubina Biozone, associations of Danian vary to undergo a complete renewal in the upper zones. The Ouled Haddou section, described for the first time, presents, according to planktonic Foraminifera, a complete record of the Cretaceous–Palaeogene transition. To cite this article: A. Toufiq et al., C. R. Geoscience 334 (2002) 995–1001.

Cretaceous lithostratigraphic units (Belgium)

The Cretaceous formations of the Mons Basin, of the Méhaigne-Petite Gette Basin area and of the Liège-Limburg Basin area are described and discussed following recent literature. Of the 22 Cretaceous formations of the Mons Basin 8 are of Early Cretaceous age and 14 of Late Cretaceous age. In the Méhaigne-Petit Gette Basin area no formations have been named, but the different levels found have been considered as members; their age varies from? Coniacian to Late Maastrichtian. In the Liège-Limburg Basin area four Cretaceous formations have been recognised, divided in very detailed members based on lithostratigraphical characteristics (flints) by Felder; these formations vary in age from? Coniacian to uppermost Maastrichtian.

Clay mineralogy of the Late Cretaceous and early Tertiary successions of the Cauvery Basin (southeastern India): implications for sediment source and palaeoclimates at the K/T boundary

Clay mineral analyses were carried out on late Maastrichtian–early Palaeocene (Cretaceous–Tertiary) sedimentary rocks in the Ariyalur area of the Cauvery Basin (southeastern India). These investigations were aimed at determining the sedimentary provenance and palaeoclimate of the area in the latest Cretaceous and earliest Tertiary. The late Cretaceous deposits show significant palaeogeographic variation in clay mineral contents across the study area. Mixed-layer illite-smectites dominate the clay mineral content of the uppermost Maastrichtian of all areas, with elevated smectite, illite, palygorskite, sepiolite, kaolinite and chlorite occurring at intervals through the succession. This combination and widespread variation in the clay mineral suite suggests a lithologically highly variable source terrain and lack of sediment mixing during transport. Mixed-layer clays occur with both kaolinite and palygorskite, interpreted in terms of a seasonal (warm and wet, warm and dry) source area. The uppermost Maastrichtian of the Niniyur section displays an upward increase in illite content, suggesting that the adjacent continental area became strongly influenced by physical weathering just prior to the K/T boundary. The return of mixed-layer clays, smectite, illite and kaolinite during the early Tertiary suggests that chemical weathering in a seasonal climate once again controlled the formation of clay minerals. These results imply that the volcanism associated with the Deccan Traps had no sudden effect on the Cretaceous or Tertiary sedimentation and clay mineralogy of this area.

New dinosaur sites correlated with Upper Maastrichtian pelagic deposits in the Spanish Pyrenees: implications for the dinosaur extinction pattern in Europe

Six new dinosaurs sites have been found close to the Cretaceous/Tertiary boundary in Arén (south-central Pyrenees, Huesca, Spain) in coastal and non-marine deposits of the Arén and Tremp Formations. The sites contain articulated remains (skull elements, vertebrae, hind-limb bones) and isolated teeth and bones of hadrosaurids, three types of theropod teeth, one sauropod, at least seven types of eggshells (six ornithoid types and one Megaloolithidae probably from a sauropod), remains of other vertebrates, and four charophyte species. The fossil-bearing rocks have been correlated with marine sediments containing planktonic foraminifera from the uppermost Maastrichtian Abathomphalus mayaroensis Biozone. These rich and diversified dinosaur assemblages enable more accurate dating of the faunal changes that took place during the Maastrichtian in Europe and support the hypothesis of a sudden dinosaur extinction at the Cretaceous/Tertiary boundary.

Origin of the Peñalver Formation in northwestern Cuba and its relation to K/T boundary impact event

Abstract The uppermost Maastrichtian Penalver Formation and its equivalents in northwestern Cuba are characterized by thick, normal-graded calcarenite with distinct basal conglomerate, and have been suspected as deposits related to the Cretaceous–Tertiary boundary (K/T) impact. However, its depositional mechanism is not well understood and clear evidence for its association with the impact has never been presented. In this study, detailed field survey and petrographic observations were carried out on the Penalver Formation in order to clarify its sedimentary processes and to test its relation to the K/T impact. The Penalver Formation at the type locality near Havana is approximately 180 m thick and is subdivided into the Basal, Lower, Middle, Upper and Uppermost Members based on its lithology. The Basal Member consists of massive, poorly sorted, calcirudite with grain-supported fabric, which contains abundant macrofossils of shallow-marine origin and occasional large intraclasts of the underlying strata, suggesting that it was formed by a grain flow from a carbonate platform on the Cretaceous Cuban Arc. The Lower to Uppermost Members consist of massive calcarenite and calcilutite that show upward fining. Composition of the calcarenite is distinctly different from that of the Basal Member. The homogeneous appearance, coarse-tail normal grading, abundant water escape structures, and abundant reworked fossils in these members are consistent with those of the Mediterranean “homogenite”, a deep sea tsunami-induced deposit that was formed by settling from a high density suspension. Repetition of thin conglomerate beds in the Lower Member that contain well-sorted, well-rounded mud clasts and shallow marine fossils is considered to reflect intermittent lateral flow possibly induced by a series of tsunami waves during an early stage of settling of grains from a high density suspension. Altered vesicular glass of probable impact origin and shocked quartz are discovered in the Basal and the Lower to Upper Members, respectively. Together with the biostratigraphically constrained age of the Penalver Formation, this evidence suggests that the Penalver Formation has a genetic relation to the K/T impact. Distribution of altered vesicular glass and shocked quartz grains can explain the sequence of the initial grain flow and the following tsunami waves.

Paléosurfaces d'érosion et paléokarsts dans la série de passage Crétacé/Tertiaire des Corbières occidentales (Aude, France)

The continental series of Uppermost Maastrichtian/‘Lower Paleocene’ includes 6 palaeosurfaces induced by the erosion of alluvial marls and the karstification of lacustrine/ palustrine limestones within a subtropical climate characterized by a moderate pluviometry. An estimation of the whole gap gives a relatively high extension which must be taken into consideration in the stratigraphic studies and the search for the iridium anomaly at the K/T boundary. The evidenced discontinuities are helpful for correlations between continental and marine domains as they may refer to low stand episodes.

Paleoenvironmental changes across the Cretaceous–Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy

The Koshak section of the Mangyshlack Peninsula, Kazakhstan, is one of the most complete Cretaceous–Tertiary (K–T) transitions known from the boreal Paratethys. Cretaceous species richness is low (11 to 13 species), except for a peak of 20 species near the K/T boundary in the uppermost Maastrichtian (top 50 cm) that represents the temporary incursion of low-latitude taxa. This maximum species richness occurred during climatic warming associated with increased humidity, as suggested by clay mineral analyses. Biofacies analysis suggests external platform conditions at this time, followed by a more humid climate, a sea-level transgression, and deepening basinal facies in the lower Danian Subzone P1a. Shallower platform conditions resumed in Danian Subzones P1b and P1c, accompanied by a cooler and probably more arid climate. No abrupt mass extinction occurred at the Koshak K/T boundary which is marked by an Ir anomaly, a clay layer and the first appearance of Tertiary planktic foraminifera. The influx of lower-latitude species ends at or before the K/T boundary, whereas the majority of the indigenous Cretaceous assemblage survived into the Danian. These data suggest that long-term climatic changes may have been the principal factors in the progressive demise of the Cretaceous planktic foraminifera in the eastern boreal Paratethys.

Stratigraphy and pre-Miocene tectonic evolution of the southwestern part of the Sivas Basin, Central Anatolia, Turkey

In central Anatolia there are several important basins developed mainly after closure of the northern branch of Neotethys. These are the Haymana, Tuzgölü, Ulukışla, Kızılırmak, Çankırı-Çorum and Sivas basins. The Sivas Basin is located in the eastern part of central Anatolia between the Central Anatolian Crystalline Complex (CACC) in the north and Taurides in the south. The basement to the southeastern part of the basin consists of recrystallized limestone and clastics of the Permian–Lower Cretaceous Bünyan Metamorphics. These units are overlain by an Upper Cretaceous ophiolitic olistostrome that is overthrust by ophiolites and high pressure–low temperature metamorphic rocks. Lower Palaeocene cover units unconformably overlie this sequence. The basement to the northwestern part is constituted by CACC that includes a high temperature–low pressure polymetamorphic succession of Palaeozoic–Mesozoic age, overthrust by ophiolites and intruded by Upper Cretaceous post-collisional granitoids and syenitoids. The uppermost Maastrichtian–Palaeocene continental to shallow marine (lagoonal) unit unconformably overlies this unit. Upper Cretaceous–Palaeocene siltstone, shale, pelagic limestone, volcaniclastic rocks and basic volcanic rock intercalations of a within-continental-plate eruptive setting have also been developed on the basement unit. These sequences represent the products of an extensional episode during Late Cretaceous–Palaeocene times in the region between the Taurides and CACC. The Middle Eocene is represented by a regional transgression which was followed by a compressional episode evidenced by thrust faults at the margins and continued regression in the central part of the basin. This compressional period continued up to the end of the Early Miocene. Units formed during this episode are overlain by Upper Miocene–Quaternary continental units intercalated with volcanic rocks formed in fault-controlled extensional basins. It is suggested that the palaeotectonic events were the result of terminal closure of the northern branch of Neotethys. However, the neotectonic events are the result of the collision of the Arabian Plate and Anatolides which causes a westward escape of the Anatolian Plate. Copyright © 1999 John Wiley & Sons, Ltd.

The oertlispongidae (Radiolaria) from the middle triassic of Masirah Island (Oman)

The paper describes the species of Oertlispongidae (Spumellarian Radiolaria) found in an exotic block embedded in the uppermost Maastrichtian of the Fayah Unit (Masirah Island, Oman). This block was dated as Fassanian-Cordevolian on the basis of poorly preserved radiolarians. The Oertlispongidae are exclusively represented by remains of main spines belonging to 6 genera and 11 species, among which two species ( Baumgartneria ambigua and B. omanensis) are new. The former species is transitional between the genera Oertlispongus Dumitrica, Kozur and Mostler and Baumgartneria Dumitrica, while the latter seems transitional between Baumgartneria and some Scutispongus Kozur and Mostler.

La limite Crétacé-Tertiaire en domaine marin dans les Pyrénées centrales (zone sous-pyrénéenne, France)

The discovery of Paleocene planktonic Foraminifera (subzones P1c to P3b) in the western sub-Pyrenean zone (Haute-Garonne) made it possible to locate an anomalously high abundance of iridium at the Cretaceous-Tertiary boundary underlining the interface between the ‘calcaires à Bryozoaires/calcaires à Algues, of Larcan-Nizan’, newly assigned to Danian-Selandian and the underlying ‘marnes bleues de Saint-Loup’, the top of them being Uppermost Maastrichtian in age (Hariaensis zone and grade-datation of 65.47 Ma). A short gap (subzones P0 to P1b, Lowermost Danian) probably marks, as in Béarn, the base of the Paleocene Larcan-Nizan Bryalgal limestones.

Planktonic foraminiferal turnover across the Cretaceous-Tertiary boundary in the Vajont valley (Southern Alps, northern Italy)

Planktonic foraminiferal analysis of the Erto section in the Vajont valley (Southern Alps, northern Italy) reveals a relatively complete succession across the Cretaceous–Tertiary (K–T) boundary. The turnover of planktonic foraminiferal fauna was studied for a stratigraphic interval spanning the Abathomphalus mayaroensisZone p.p., Pseudotextularia deformisZone, Guembelitria cretaceaZone, Parvularugoglobigerina eugubinaZone, Eglobigerina eobullioidesSubzone, and Parasubbotina pseudobulloidesZone p. p.The extinction of most large, ornate, late Maastrichtian species occurs below a black ‘boundary clay’ (2–4 cm thick); however, part of the Late Cretaceous species, mainly heterohelicidids and hedbergellids, were found over an interval of more than 100 cm above the boundary. Although a relatively high number of species occur for the last time in the main extinction phase, the abundance of these outgoing species is less than 20% of the total population; unkeeled or weakly keeled, simple-shaped forms (heterohelicids, globotruncanellids, hedbergellids) constitute the bulk of the planktonic foraminiferal population both in uppermost Maastrichtian and lowermost Danian beds. The first Tertiary species (‘ Globigerina’ minutulaand ‘ Globigerina’ fringa) appear just above the ‘boundary clay’; Parvularuglobigerina eugubinaoccurs a few centimeters above. A marked increase in abundance and diversity in the Tertiary planktonic foraminiferal population occurs at the base of the Eoglobigerina eobulloidesSubzone.