Cretaceous Paleogene Research Articles

An astronomical time scale for the Maastrichtian based on the Zumaia and Sopelana sections (Basque country, northern Spain)

The rhythmically bedded limestone–marl alternations in the coastal cliffs of Sopelana and Zumaia in the Basque country, northern Spain, permit testing and refining of existing Maastrichtian chronologies (latest Cretaceous). The recently established astronomical time scale for the late Maastrichtian at Zumaia is extended into C31n with the integrated stratigraphy of the Sopelana section. The cyclic alternations of hemipelagic limestones and marls at Sopelana show a strong influence of eccentricity-modulated precession. Together, the Zumaia and Sopelana sections span almost the entire Maastrichtian, and encompass thirteen 405 kyr cycles spanning a total duration of 5.3 myr. From the Cretaceous–Paleogene (K–Pg) boundary downwards, 405 kyr minima in the lithological, magnetic susceptibility and reflectance data records are tuned to successive 405 kyr minima in the new La2011 eccentricity solution. Assuming a K–Pg boundary age of 65.97 Ma, we present orbitally tuned ages of biostratigraphic and magnetostratigraphic events. Whereas the bases of Chrons C29r and C30n were reliably established at Zumaia and are in good agreement with previous studies, new data from Sopelana provide a refinement of the basal age of Chron C31r. Additional planktonic foraminifera and calcareous nannoplankton data from Zumaia, and new calcareous nannoplankton data from Sopelana, allow for worldwide correlation of the cyclostratigraphy of the Basque country. Supplementary materials: A geological map and additional data are available at www.geolsoc.org.uk/SUP18696 .

A revised Paleocene (Teurian) dinoflagellate cyst zonation from eastern New Zealand

Organic-walled dinoflagellate cyst (dinocyst) assemblages are documented from Paleocene (New Zealand Teurian Stage) sediments in five sections from eastern New Zealand: Tawanui, Angora Road and Toi Flat-1 core in the East Coast Basin, mid-Waipara River in the Canterbury Basin, and ODP Site 1121 on the eastern margin of Campbell Plateau. Based on dinocyst results from these sections, along with published earliest Paleocene records from the East Coast, Canterbury and Great South Basins, a revised Paleocene (Teurian) dinocyst zonation is proposed. The zones are labelled as NZDP — New Zealand Dinocyst Paleocene — and are all interval zones. The eight zones, NZDP1 to NZDP8, encompass the entire Paleocene, from the Cretaceous–Paleogene boundary at 66.04Ma to the Paleocene–Eocene boundary at 55.96Ma. Correlation of the NZDP zones with the International and New Zealand Time Scales is provided, and is primarily based on correlation with calcareous nannofossil biostratigraphy. Three new dinocyst species are described: Leptodinium? pustulatum sp. nov., Cerodinium angulatum sp. nov., and Vozzhennikovia tawanuiensis sp. nov.

Getting a Leg Up: Mammalian Postcrania Across the Cretaceous–Paleogene Boundary in Northeastern Montana

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Sedimentary Environments and Correlative Sequence Stratigraphy of Upper Cretaceous—Paleogene Succession in Shiraz Area, Fars, SW IRAN

Sequence stratigraphic evidences have been used in this research to investigate the stratigraphic correlation of cretaceous paleogene succession in Shiraz area, Fars, SW Iran. For this purpose, 4 stratigraphic sections have been chosen and provided. According to petrographic study and field evidences, 4 depositional sequences were identified including the Tarbur, Sachun and Jahrum formations in the east and the Gurpi, Pabadeh and Asmari formations in the west of study area. After identifying the boundaries and systems tract facies, it has been found that the mentioned formations have been deposited among the continuous/discontinuous boundaries in an equivalent manner. In this case, the purple shale (between the Gurpi and Pabdeh formations) could be considered equivalent to the upper part of the Sachun formation. From the point of Paleogeography, the plat-form sedimentary environment covered almost the whole area during the Oligo-Miocene age, so that the Asmari formation would have been deposited, which is marked by sharp contact as disconformity on Jahrum formation in the east of the basin and with continuous contact (C.C) on the Pabdeh formation in the west and southwest.

The Endemic Floras of Zealandia: Key Components of the Cretaceous–Paleogene Gondwana Expressway

The Endemic Floras of Zealandia: Key Components of the Cretaceous–Paleogene Gondwana Expressway

Bottom-Water Conditions in a Marine Basin after the Cretaceous–Paleogene Impact Event: Timing the Recovery of Oxygen Levels and Productivity

An ultra-high-resolution analysis of major and trace element contents from the Cretaceous–Paleogene boundary interval in the Caravaca section, southeast Spain, reveals a quick recovery of depositional conditions after the impact event. Enrichment/depletion profiles of redox sensitive elements indicate significant geochemical anomalies just within the boundary ejecta layer, supporting an instantaneous recovery –some 102 years– of pre-impact conditions in terms of oxygenation. Geochemical redox proxies point to oxygen levels comparable to those at the end of the Cretaceous shortly after impact, which is further evidenced by the contemporary macrobenthic colonization of opportunistic tracemakers. Recovery of the oxygen conditions was therefore several orders shorter than traditional proposals (104–105 years), suggesting a probable rapid recovery of deep-sea ecosystems at bottom and in intermediate waters.

Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression

Prámparo, M.B., Cione, A.L. & Gonzalez Riga, B., 2013. Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression. Alcheringa 38, 000–000. ISSN 0311–5518.Neoselachian (modern shark) teeth and palynomorphs have been recovered from the Late Cretaceous Jagüel Formation in the Province of Mendoza, Argentina. The fossiliferous beds were deposited during the Atlantic transgression that covered northern Patagonia and other parts of South America from the Maastrichtian to the Danian. Teeth of several lamniform sharks are attributed to the anacoracid Squalicorax pristodontus and cf. Serratolamna serrata of indeterminate familial affinity. These taxa became extinct at the end of the Cretaceous and confirm the late Maastrichtian age previously assigned to the Jagüel Formation in this northwestern part of the Neuquén Basin. For the first time, the selachian faunas are described together with algae and dispersed organic matter assemblages (palynofacies), revealing new elements of the neritic biota leading up to the Cretaceous–Paleogene (K–Pg) mass extinction in South America. The palynoflora consists exclusively of the prasinophyte algae Tasmanites, Cymatiosphaera and Pterospermella, indicative of stratified saline waters. Dispersed organic components in the profile (mainly opaque equidimensional phytoclasts and prasinophytes) are consistent with an inner neritic environment, with evidence (a great variety of particle sizes, lath-shaped phytoclasts increasing slightly in number and decreasing number of marine components) of slightly more nearshore conditions towards the upper part of the profile. These marine biotas confirm the presence of an epeiric sea over northern Patagonia, which extended westwards to the volcanic arc on the western flank of the Andean Cordillera in Mendoza.Mercedes B. Prámparo [mprampar@mendoza-conicet.gov.ar], IANIGLA-CONICET, CCT-Mendoza. Avda. R. Leal s/n, Parque Gral. San Martín, (5500) Mendoza, Argentina; Alberto Luis Cione [acione@museo.fcnym.unlp.edu.ar], División Paleontología de Vertebrados. Museo de La Plata. 1900 La Plata, Argentina; Bernardo González Riga [bgonriga@mendoza-conicet.gov.ar] IANIGLA-CONICET, CCT, Mendoza. Avda. R. Leal s/n, Parque Gral. San Martín, (5500) and ICB, Universidad Nacional de Cuyo, Argentina. Received 28.5.2013, revised 17.9.2013, accepted 24.9.2013.

Platinum stable isotope analysis of geological standard reference materials by double-spike MC-ICPMS

We report a method for the chemical purification of Pt from geological materials by ion-exchange chromatography for subsequent Pt stable isotope analysis by multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) using a 196Pt–198Pt double-spike to correct for instrumental mass bias. Double-spiking of samples was carried out prior to digestion and chemical separation to correct for any mass-dependent fractionation that may occur due to incomplete recovery of Pt. Samples were digested using a NiS fire assay method, which pre-concentrates Pt into a metallic bead that is readily dissolved in acid in preparation for anion-exchange chemistry. Pt was recovered from anion-exchange resin in concentrated HNO3 acid after elution of matrix elements, including the other platinum group elements (PGE), in dilute HCl and HNO3 acids. The separation method has been calibrated using a precious metal standard solution doped with a range of synthetic matrices and results in Pt yields of ≥90% with purity of ≥95%. Using this chemical separation technique, we have separated Pt from 11 international geological standard reference materials comprising of PGE ores, mantle rocks, igneous rocks and one sample from the Cretaceous–Paleogene boundary layer. Pt concentrations in these samples range from ca. 5ngg−1 to 4μgg−1. This analytical method has been shown to have an external reproducibility on δ198Pt (permil difference in the 198Pt/194Pt ratio from the IRMM-010 standard) of ±0.040 (2sd) on Pt solution standards (Creech et al., 2013, J. Anal. At. Spectrom. 28, 853–865). The reproducibility in natural samples is evaluated by processing multiple replicates of four standard reference materials, and is conservatively taken to be ca. ±0.088 (2sd). Pt stable isotope data for the full set of reference materials have a range of δ198Pt values with offsets of up to 0.4‰ from the IRMM-010 standard, which are readily resolved with this technique. These results demonstrate the potential of the Pt isotope system as a tracer in geochemical systems.

From enriched to depleted mantle: Evidence from Cretaceous lamprophyres and Paleogene basaltic rocks in eastern and central Guangxi Province, western Cathaysia block of South China

Much of Eastern China underwent significant lithospheric thinning during Phanerozoic time. Compared to the wealth of detailed research on the destruction of the North China Craton since the Mesozoic, the lithospheric evolution of South China (including the Yangtze Craton and the Cathaysia block) is still unclear. In particular, studies of the western part of the Cathaysia block, which connects the Yangtze Craton in the west to the eastern Cathaysia block in the east, are sparse. The study of the mantle-derived magmatic rocks from the western Cathaysia block can provide a better understanding of the continental evolution of South China, and of greater East Asia. Elemental and SrNd isotopic compositions of the Cretaceous (89Ma) lamprophyres and Paleogene (51–28Ma) basaltic rocks in eastern and central Guangxi Province, western Cathaysia block, were analyzed to reveal the nature of their mantle sources. The Cretaceous lamprophyres are ultrapotassic, strongly enriched in LILE–LREE and depleted in HFSEs (e.g., Nb, Ta, Ti), and have high (87Sr/86Sr)i and negative εNd (t) values. They probably were derived from low-degree partial melting of an EM2-type garnet-facies (>80km) subcontinental lithospheric mantle (SCLM), followed by the fractionation of olivine and clinopyroxene. The modeled SCLM, mainly a phlogopite-bearing harzburgite, represents a refractory mantle that was metasomatically enriched by subduction, prior to the Pacific subduction during Mesozoic. The Paleogene basaltic rocks are enriched in alkalis, LILEs and LREE but positive NbTa anomalies, and are similar to alkali oceanic-island basalts. These basaltic rocks have DM-type SrNd isotopic signatures, with low (87Sr/86Sr)i and high εNd (t). They probably were derived from the low-degree partial melting of fertile (asthenospheric) mantle in spinel- to spinel-garnet-facies lherzolite (<80km). The differences imply that the source region was transformed from EM2 in Cretaceous time to DM-mantle in Paleogene time, and that lithospheric replacement occurred over Cretaceous–Paleogene time. It was driven by the two-sided dynamics around the Cathaysia block, with Pacific subduction in the east and the Eurasian–Indian plate collision in the west. The complex subduction dynamics led to complex asthenospheric convection, a regional lithospheric extension beneath the Cathaysia block, and the removal or modification of the ancient SCLM.

Comparison of scaling relationships of extensional fault cores in tight carbonate and porous sandstone reservoirs

This paper presents a comparative analysis of the thicknesses–displacement relationships of fault cores in non-/low-porous carbonate and porous sandstone reservoirs. Fault thickness data were collected from extensional faults in mainly Cretaceous continental sandstones and Late Cretaceous–Paleogene marine carbonates exposed along the eastern flank of the Suez Rift, Egypt. The dataset consists of 730 thickness measurements, of which 313 are from 68 faults in carbonate rocks, and 417 are from 120 deformation band/microfaults and faults in sandstones. These data show that the increase in fault core thickness with displacement for the two lithologies is, overall, similar in log–log space, consistent with a power-law trend with an exponent of 0.5. However, for smaller faults, cores in carbonates are generally thicker than those in sandstones. The observation of nearly equal core thickness–displacement relationships for larger faults (&gt;10 m displacement) suggests that increased displacement reduces the geomechanical influence of lithology. In a statistical analysis of bins of fault displacement, small displacement faults seem to follow a skewed distribution towards smaller fault core thicknesses, moderate displacement faults have a normal distribution, while large displacement faults have a distribution skewed towards large core thicknesses. Each thickness distribution can be estimated with a mean and standard deviation. Fault core thickness variations are caused by interplaying factors such as fault geometric development, spatial and temporal positioning of shear and volumetric strains, and rheological changes. The variability in core thickness and intrinsic architecture of fault cores for any given location will cause significant variation in across-fault fluid flow, even for the same juxtaposition style.

Ancient Bug Bites on Ancient Plants Record Forest Ecosystem Response to Environmental Perturbations

Leaf-compression fossils with insect feeding traces are unique in providing rich, direct evidence of two levels in a fossil food web. Plant-insect associations dominate terrestrial trophic interactions, emphasizing the need to understand their ecological and evolutionary history. This paper first discusses methods of recognizing insect herbivore damage on fossil leaves and quantifying fossil insect herbivory. By conducting an unbiased insect damage census, damage frequency (percent of leaves with insect feeding damage), percent of leaf surface area removed by insects, and damage diversity (the number of discrete damage morphotypes, or DTs, found on a fossil flora or individual host plant) can all be measured. Three examples of responses of past plant-insect trophic interactions to environmental stresses are examined. In the first case study, late Oligocene fossil floras from Ethiopia document forest response to local perturbation and key characteristics to recognize disturbance in the plant fossil record. The second case study considers the terrestrial ecosystem response to the catastrophic global perturbation at the Cretaceous–Paleogene boundary. In the third case study, the impact of past global warming events—including the Paleocene–Eocene Thermal Maximum—on insect herbivory is discussed. Productive avenues for further research include: insect damage studies conducted outside the North American Cretaceous and Paleogene, actualistic and taphonomic studies of insect herbivory, and tighter collaboration across paleobotany, paleoentomology, botany, and entomology.

Hypothesis of homeothermy evolution on isolated South China Craton that moved from equator to cold north latitudes 250–200 Myr ago

Based on avian and mammalian fossils found in the northeastern Chinese province of Liaoning and physiological traits linked to homeothermy, a hypothesis of evolution of homeothermic animals is proposed. It is based on the importance of muscle function in cold environment, as a strong selection pressure that favors endothermic metabolism during periods of cold climates. The presented hypothesis postulates that in progressively cooling environment, animals will develop thermal insulation, increased basal metabolism if food is available, and torpor when food is scarce. Since late Permian, Triassic and Cretaceous global temperatures were high, an exceptional place that gradually became cold was needed for the homeothermy evolution.South China Craton is here proposed as a plausible candidate for that role since it drifted across the Paleo-Tethys ocean, from equator to high northern latitudes in a journey that lasted from 250 to 200Myr ago. After this small continent collided with North China Craton some 200Myr ago, the already cold-adapted animals had spread to large, mostly empty spaces on the North China Craton, due to their evolutionary advantage of making active living in the cold environment. The most advantageous early homeothermic animals went further north to the cold Liaoning to start an oasis that delivered modern birds during next 50Myr. Modern mammals possibly evolved somewhere in the cold vicinity. This made Liaoning and similarly cold places the cradles of early birds and early mammals since for the following millions of years these places remained too cold for poikilotherms to enter and warm enough for homeotherms to dwell, until the Cretaceous–Paleogene extinction event and subsequent global cooling that diminished poikilotherms. Homeothermy was probably even more important as a survival advantage in cooler climates of Paleogene, when mammals and birds became dominant animals.This interpretation is probably supported by a recent report that a small primate Archicebus achilles dated ~55Myr ago was found in the more south central China Hubei Province, while Hadrocodium wui, extinct mammaliaform that lived 195Myr ago in what is now the Yunnan province in southwestern China. The final confirmation of the proposed scenario would be to find somewhere in South China avian fossils older than those found in Liaoning, or to find the cradle of early mammals somewhere in Northern China.

Diversification patterns of planktic foraminifera in the fossil record

Abstract Theories of taxonomic diversification dispute whether global diversity has an upper limit set by the strength of biological interactions or grows in unlimited fashion until catastrophic events reset the system. We analyzed a global compendium of fossil planktic foraminifera from the early Cretaceous to the present after correcting for temporal differences in sampling effort. Our results show that their morphological diversity has increased exponentially through time in two different phases. The first phase collapsed at the Cretaceous–Paleogene boundary transition. The second phase developed through the Cenozoic era and declined during the Pliocene–Pleistocene interval, a period of time that was dominated by enhanced climatic and oceanographic instability. In none of these phases diversity reached an equilibrium level. Cenozoic faunas evolved faster than those inhabiting Cretaceous oceans, perhaps as a result of a higher environmental variability. Our results indicate that planktic foraminifera conform to an exponential diversification model. However, because catastrophic events have repeatedly reset the level of biological diversity and have kept it below the maximum, we cannot confirm whether the level of diversity is potentially unlimited.

The Deccan Trap – Cretaceous–Paleogene boundary connection; new 40Ar/39Ar ages and critical assessment of existing argon data pertinent to this hypothesis

The Cretaceous–Paleogene boundary (KPgB) was dated by the 40Ar/39Ar method herein from the western interior of North America at 65.48±0.12Ma (1σ), in good agreement with other recent published estimates. For the Deccan Traps, India, new argon ages as well as others available in the literature, are assessed for reliability based on (a) statistical reliability of plateau/isochron sections and (b) freshness of material dated utilizing the alteration index method. From tholeiitic lavas from the Composite Western Ghats Section (CWGS), only six ages are found to be reliable estimates of the time of crystallization. These ages along with the magnetic polarity of the lavas agree with the geomagnetic polarity time scale (GPTS) at ∼67–64Ma. Alkaline rocks from the Anjar area of Kutch, provide three reliable ages that suggest a hiatus in lava extrusion around KPgB. For the Rajahmundry basalts, the upper flow’s age defines its formation during chron 29n; a single age from the lower reversed polarity flow appears somewhat dichotomous when plotted against the GPTS. The reliable lava ages indicate the most voluminous (reversed polarity) sections of the CWGS were extruded at a time statistically indistinguishable from that of the KPgB. The Deccan Trap – KPgB faunal extinction hypothesis remains plausible, but must compete with the latest report, favoring a very close temporal connection (∼0.03m.y.) between the Chixculub (Impact) Crater and the KPgB.

Mercury as a proxy for volcanic activity during extreme environmental turnover: The Cretaceous–Paleogene transition

The usually low geological background concentrations of Hg makes this trace element suitable for identifying accumulation pulses in sediments that can be tentatively related to weathering processes and thus to climatic changes. Intense volcanism has witnessed the Cretaceous–Paleogene transition (KTB) and was, perhaps, responsible for dramatic climatic changes and decrease in biodiversity and mass extinction. We have used Hg concentrations as a proxy for volcanic activity and atmospheric Hg and CO2 buildup across the KTB at three localities. In the Salta Basin, Argentina, Hg contents display several spikes across the KTB, with a maximum value of 250ng·g−1. In three drill cores across the KTB in the Paraíba Basin, northeastern Brazil, Hg contents increase from the late Maastrichtian to early Danian and Hg spikes predate the KTB, perhaps, as a record of volcanic activity before (but very close to) this transition. At Stevns Klint, Denmark, Hg contents reached almost 250ng·g−1 within a 5cm thick-clay layer, the Fiskeler Member (‘Fish Clay’) that comprises the KTB. Some co-variation between Hg and Al2O3 contents has been observed in all of the studied sections across the KTB, suggesting that Hg is probably adsorbed onto clays. Thermo-desorption experiments in selected samples from the Yacoraite Formation showed Hg+2 as the major species present, which is in agreement with a volcanic origin. Combined Hg and C-isotope chemostratigraphy may become a powerful tool for the eventual assessment of the role of volcanic activity during extreme climatic and biotic events, such as those during the KTB.

Platinum-group element (PGE) geochemistry of Deccan orangeites, Bastar craton, central India: Implication for a non-terrestrial origin for iridium enrichment at the K–Pg boundary

We report platinum group element (PGE) concentrations of twelve bulk-rock samples from the Behradih and Kodomali orangeite intrusions in the Mainpur field, Bastar craton, central India, which are emplaced synchronously with the Deccan flood basalts. Their palladium-group PGE (PPGE) (1.8–5.2ppb Pt, 1.2–6.4ppb Pd) contents are distinctly higher compared to their iridium-group PGE (IPGE) concentrations (0.8–2ppb Os, 0.8–1.2ppb Ir, 3.2–4.2ppb Ru, and 0.2–0.8ppb Rh). Their PGE contents as well as Pd/Ir ratios are either similar or even lower than those from the Mesoproterozoic and Cretaceous kimberlites and orangeites from the Kaapvaal craton (southern Africa), Cretaceous kimberlites from the Sao Fransisco craton (Brazil), Ordovician kimberlites from the North China craton and the Mesoproterozoic southern Indian kimberlites from the Eastern Dharwar craton. Anomalously elevated iridium (and other PGE) contents in sediments at the Cretaceous–Paleogene (K–Pg) boundary are commonly attributed either to a large bolide impact triggering the K–Pg mass extinction or to terrestrial causes such as volcanic eruptions (Deccan flood basalts) or even to mantle-plume derived lithospheric gaseous explosions (Verneshots). Lack of unusually high abundances of PGE in the Mainpur orangeties as well as in the co-eval Deccan flood basalts and associated alkaline rocks implies that the anomalous iridium enrichment reported at the K–Pg boundary sections was not sourced from the mantle and likely originated from an extraterrestrial source.

Reevaluation of siderophile element abundances and ratios across the Cretaceous–Paleogene (K–Pg) boundary: Implications for the nature of the projectile

The discovery over 30years ago at Gubbio (Italy) and Caravaca (Spain) of an enrichment in the concentrations of iridium (Ir) and the other platinum group elements (PGE) by up to four orders of magnitude (Irmax=0.10–87ng/g) compared to average continental crustal background levels remains one of the most important discoveries in the Earth sciences. Since then, similar anomalies have been detected in more than 120 Cretaceous–Paleogene (K–Pg) boundary sites worldwide. Highly elevated Ir and other siderophile element abundances in roughly chondritic ratios are considered strong indicators for the presence of a meteoritic contribution in impact-related lithologies (melt rocks, impact ejecta material, etc.), delivered when an extraterrestrial object strikes Earth. The presented work adds 113 unpublished PGE analyses of 38 K–Pg sections worldwide to the existing literature. The analytical protocol relied on for this purpose consisted of a combination of a nickel-sulfide fire assay pre-concentration technique and subsequent trace metal determination via inductively coupled plasma-mass spectrometry (ICP-MS). Through repeated determination of key siderophile elements (i.e., Cr, Co, Ni, and PGE), the importance of sampling, nugget effects, and analytical methodologies applied becomes more apparent. Even more critically, these analytical effects are superimposed by the local syn- and post-depositional conditions that have affected the pristine meteoritic signature of the K–Pg impactor, including potential fractionation during vaporization and condensation, dissimilar PGE carrier phases, terrestrial PGE input, sedimentation rate, reworking, diagenesis, bioturbation, and chemical diffusion. While chondrite-normalized PGE patterns of individual sites appear relatively flat (i.e., chondritic), strong variations in siderophile element content and inter-element ratios exist between K–Pg locations, inter-laboratory measurements, and replicate analyses, hampering a precise projectile identification using (highly) siderophile elements. Only when considering improved databases of siderophile element concentrations in meteorites, in combination with linear regression analysis to calculate inter-element ratios from a large suite of ejecta deposit sites, the nature of the K–Pg projectile can be resolved. Application of this methodology to an extensive data set of continental and marine sites, very proximal to distal to the Chicxulub impact structure, supports a carbonaceous chondritic impactor (type CM or CO).

Organic-walled dinoflagellate cyst biostratigraphy of the Well Höflein 6 in the Cretaceous–Paleogene Rhenodanubian Flysch Zone (Vienna Basin, Austria)

Abstract Palynological analysis of the Rhenodanubian Flysch Zone section recovered from Well Höflein 6 north of Vienna allows the successful application of non-calcareous dinoflagellate biostratigraphy to the deep-water sediments of the Greifenstein Nappe. All 62 cuttings samples contained organic-walled dinoflagellate cysts (dinocysts) and some of them allow age-assessment. The results corroborated the presence of two thrust slices. The upper thrust unit A comprises a Campanian to Lower Eocene succession including, from old to young, the Röthenbach Subgroup, Perneck Formation, Altlengbach Formation and Greifenstein Formation. The lower thrust unit B contains in addition a pre- Campanian base, probably the Wolfpassing Formation of Early to mid-Cretaceous age.

Testing the terrestrial δ13C Cretaceous–Paleogene (K–Pg) chemostratigraphic marker

Multiple >1‰ δ13C isotopic excursions measured across the Cretaceous–Paleogene (K–Pg) boundary in an iridium-bearing stratigraphic section from Mud Buttes, North Dakota, USA, fail to demonstrate an unambiguous chemostratigraphic signal for the extinction. Results of two-sample Kolmogorov–Smirnov tests using δ13C records for the Mud Buttes section as well as five other published K–Pg sections from Montana, North Dakota, Wyoming, and Canada – all of which report a −1.0‰ to −2.8‰ chemostratigraphic marker at or just above the extinction – demonstrate that it may not be possible to distinguish a statistically meaningful isotopic shift to lower δ13C values at the boundary in the context of background variations. Carbon isotopes as terrestrial chemostratigraphic markers of the K–Pg extinction boundary are thus of limited utility.

Compositional variation of the late Cretaceous–Paleogene plutons from southwest Japan and its implication for ore genesis and continental growth

During the late Cretaceous–Paleogene period, the fluids liberated from the subducting slab along Japanese-arc subduction zone could have triggered the partial melting of the mantle wedge, whose composition was similar to the fertile primitive mantle. Underplating of the produced basaltic magmas beneath the continental crust could further facilitate the partial melting of the lower continental crusts. The primary magmas produced by the mixing of resultant partial melts underwent various degrees of fractional crystallization processes to produce the late Cretaceous–Paleogene plutons in southwest Japan, and have contributed to the growth of continental crust with new, non-recycled materials during the Phanerozoic.The factor analysis of chemical data from ore-barren Ryoke and W–Sn-ore-rich Sanyo plutonic rocks identifies three major groups of elements: the mafic group (Al, Fe, Mg, Mn, Ca, Sr, Zn, Co, V, P, Cu, Ni, and Cr); the felsic group (Si, K, Rb, Cs, Tl, Pb, Y, Nb, Ta, Hf, Ge, Sn, W, Th, U, and HREE); and the LREE+Zr group (Ba, La, Ce, Pr, Nd, Eu, Zr, and Hf). Mafic group and felsic group elements are inversely correlated. The concentrations of LREE+Zr group elements increase first, then, decrease with increasing SiO2 content. Therefore, the high silica samples of the Ryoke+Sanyo belts are low in LREE+Zr group elements. In the Ryoke samples Mo behaves like Zr, which results in the lowest Mo content in the Ryoke samples with high silica. The high Mo and Si contents in some Sanyo samples suggest that the zircon-compatible Mo4+ may be converted to incompatible Mo6+ under a relatively high oxygen fugacity condition at the late stage of magmatic differentiation. W and Sn behave as the felsic group elements in the Ryoke+Sanyo samples. Thus, their concentrations are high in the high silica granitoids, especially rock samples from the Sanyo belt, which are often associated with W–Sn ores. The factor analysis of the Sanin plutonic samples indicates that W still belongs to the felsic group, but Sn no longer correlates with W and behaves more like Zr due to the conversion of incompatible Sn2+ to zircon-compatible Sn4+ under a relatively high oxygen fugacity condition in the Sanin belt. Therefore, Sn content is low in high silica granitoids from Sanin belt. The high silica Sanin samples are often enriched in Mo, again suggesting the conversion of zircon-compatible Mo4+ into incompatible Mo6+ in the magmas of those samples. The high Mo granitoids from the Sanin belt are probable source rocks for the associated Mo ores in the area.