Cretaceous-Tertiary Boundary Sediments Research Articles

XAFS study of Sb and As in Cretaceous–Tertiary boundary sediments: an index of soiling of the global environment with dust and ashes from impact ejecta falls

XAFS study of Sb and As in Cretaceous–Tertiary boundary sediments: an index of soiling of the global environment with dust and ashes from impact ejecta falls

Rare earth element composition as evidence of the precursor material of Cretaceous–Tertiary boundary sediments at distal sections

The Chicxulub impact event led to a worldwide deposition of impact materials originated from target rocks and the vaporized bolide. Relative contributions of both types of material to the K/T ejecta deposits vary with distance to the crater site. At distal sites (e.g., Agost and Caravaca in the SE of Spain) a major contribution of extraterrestrial material is indicated by different impact signatures, such as Os and Cr isotope composition, abundant microkrystites, platinum group elements and other siderophile elements that are typical of extraterrestrial components. Closer settings to the Chicxulub crater, for example the Blake Nose Plateau in the North American margin, display major continental crustal rock contributions in the ejecta layer. REE compositions provide additional evidence for terrestrial vs. extraterrestrial rock contributions. Previous research has not focused specifically on REE concentrations and corresponding C1- and NASC-normalized patterns. However, normalized REE patterns are already generating supplementary insights into the nature of the original material of the K/T boundary layer. Thus, Blake Nose ejecta C1-normalized patterns indicate a derivation from continental crustal target rocks. In more distal sections REE compositions point to a probable mafic precursor and confirm that extraterrestrial materials represent a major contribution the ejecta layer.

GC/MS analysis of polycyclic aromatic hydrocarbons in the Cretaceous-Tertiary boundary sediments

GC/MS analysis of polycyclic aromatic hydrocarbons in the Cretaceous-Tertiary boundary sediments

Spherule deposits in Cretaceous–Tertiary boundary sediments in Belize and Guatemala

Large spheroid deposits at Albion Island and Armenia in northern and central Belize and the spherule deposits of southern Belize and eastern Guatemala have the same glass origin based on the presence of almost pure Cheto smectite derived from alteration of impact glass from the Chicxulub impact on Yucatan, Mexico. The same origin has also been determined for altered glass spherules in Mexico, Haiti and the Caribbean. However, the spherule layers have variable ages as a result of erosion and redeposition, with an early Danian ( Parvularugoglobigerina eugubina ) zone Pla(1) age in southern Belize, Guatemala, Haiti, southern Mexico and the Caribbean, and a pre-K–T ( Plummerita hantkeninoides ) zone CF1 age of 65.27 ± 0.03 Ma in NE Mexico. A pre-K–T age for the Chicxulub impact has now also been determined from the new Yaxcopoil 1 core drilled in the impact crater. These data show that Chicxulub was not the K–T impact that caused the end-Cretaceous mass extinction, but an earlier impact event. A multiple impact hypothesis, volcanism and climate change appears the likely scenario for the end-Cretaceous mass extinction.

Palynological events and zones in Cretaceous-Tertiary Boundary sediments of Krishna-Godavari and Cauvery basins, India

Palynological events and zones in Cretaceous-Tertiary Boundary sediments of Krishna-Godavari and Cauvery basins, India

Geochemical characterisation of the Cretaceous-Tertiary Boundary sediments at Anjar, India

Geochemical, geochronological, palaeomagnetic and palaeontological evidences that show that the third Intertrappean bed at Anjar encompasses the Cretaceous-Tertiary boundary are described. Presence of three well separated iridium rich horizons indicates multiple depositional events. Their origin in volcanic or multiple cometary impacts is discussed. The results are compared with the chemical anomalies observed in Um Sohryngkew River Section in Meghalaya.

Search for fullerenes C 60and C 70in Cretaceous–Tertiary boundary sediments from Turkmenistan, Kazakhstan, Georgia, Austria, and Denmark

Fullerenes C 60and C 70have been found previously in sediments from the Cretaceous-Tertiary boundary (KTB) sites of Woodside Creek and Flaxbourne River (both New Zealand). Additional discoveries from Caravaca (Spain), Sumbar and Malyi Balkhan (Turkmenistan) and Stevns Klint (Denmark) are reported here. Fullerenes were not found in the KTB sediment from Elendgraben (Austria), nor in acid-demineralized sediments from Koshak (Kazakhstan) and Tetri Tskaro (Georgia). The average surface concentration of C 60at these sites is estimated to be 11.7×10 −3 g /cm 2(11.7 ng/cm 2), which implies 1.1 ppm normalized to the average elemental carbon surface concentration at KTB sites. Global wildfires following the Chicxulub impact 65 Myr ago are the most likely process by which these fullerenes were formed.

Elemental and stable isotope variations in the Cretaceous–Tertiary boundary sediments from the Soča Valley, NW Slovenia

ABSTRACTOxygen and carbon stable isotopes and 25 elements were determined in the undisturbed K/T boundary profile of a flysch succession in the Soča Valley, Slovenia. The elemental enrichment and stable isotope anomalies are not confined strictly to the biostratigraphically defined K/T boundary. The relatively weak metal enrichment, which is probably due to the high sedimentation rate at the time of deposition of the K/T transition sequence, was found in a clayey layer and in the boundary clayey mar] 15 cm and 5 cm above the boundary, while the negative shift in δ18O and δ13C of carbonates was restricted to the basal part of the boundary clayey marl, approximately 5 cm below the boundary. It is postulated that elemental and isotopic anomalies are probably related to the supposed, so far poorly investigated impact of an extraterrestrial body in the Gorski Kotar area of Croatia.

Provenance of mineral phases in the Cretaceous-Tertiary boundary sediments exposed on the southern peninsula of Haiti

Acid-insoluble mineral residua of tektite-bearing Cretaceous-Tertiary boundary sediments in the Beloc Formation of Haiti contain abundant shocked quartz and lesser amounts of shocked plagioclase. The shocked quartz grains typically have 2 or 3 sets of planar deformation features, although grains with up to 15 sets were observed. The proportion of shocked quartz in the boundary sediments increases with stratigraphic height; at least 70 ± 11% of the quartz grains are shocked in the uppermost stratigraphic interval. The proportion of shocked quartz throughout the boundary sediments indicates that these grains were excavated primarily from crystalline silicate units, which may have been covered with a small amount of porous quartz-bearing sediments. Polyhedral and moderately sutured margins in shocked polycrystalline quartz grains, the size of the crystal units in these grains and the presence of shocked plagioclase, indicate these ejecta components were excavated from a target with continental affinities, containing quartzites or metaquartzites and a sialic metamorphic and/or igneous component. Other evidence suggests the target may also have contained a significant amount of calcium carbonate and/or sulfate. The large size and amount of shocked quartz grains deposited in Haiti indicate the crater from which they were excavated was produced in the proto-Caribbean region.

Oxygen Isotope Constraints on the Origin of Impact Glasses from the Cretaceous-Tertiary Boundary

Laser-extraction oxygen isotope and major element analyses of individual glass spherules from Haitian Cretaceous-Tertiary boundary sediments demonstrate that the glasses fall on a mixing line between an isotopically heavy (delta(18)O = 14 per mil) high-calcium composition and an isotopically light (delta(18)O = 6 per mil) high-silicon composition. This trend can be explained by melting of heterogeneous source rocks during the impact of an asteroid (or comet) approximately 65 million years ago. The data indicate that the glasses are a mixture of carbonate and silicate rocks and exclude derivation of the glasses either by volcanic processes or as mixtures of sulfate-rich evaporate and silicate rocks.

Did extraterrestrial impactors supply the organics necessary for the origin of terrestrial life?: Amino acid evidence in cretaceous-tertiary boundary sediments

Did extraterrestrial impactors supply the organics necessary for the origin of terrestrial life?: Amino acid evidence in cretaceous-tertiary boundary sediments

Siderophile interelement variations in the Cretaceous-Tertiary boundary sediments from Caravaca, Spain

A detailed profile of the siderophiles Fe, Co, Ni, Pd, Re, Os, Ir, Pt, and Au from the Cretaceous-Tertiary boundary at Caravaca, Spain, indicates that the major fractionation mechanisms are local redistribution, reworking, and diagenetic mobilization. Large fractions of the Fe, Co, and Re and perhaps a small amount of Pd and Au appear to be terrestrially derived, but nearly all of the Ni, Os, Ir, and Pt must be derived from an extraterrestrial source. Only the basal layers at Caravaca and Stevns Klint, Denmark, are representative of the initial fallout and integrated Ir fluences across entire sections can be misleading. These suggest a concentration of t 120mg/g projectile in the fallout and a global fluence of chondritic matter of t 140mg cm −2 .

Rb-Sr, Sm-Nd, K-Ca, O, and H isotopic study of Cretaceous-Tertiary boundary sediments, Caravaca, Spain: evidence for an oceanic impact site

Isotopic ratios and trace element abundances were measured on samples of Ir-enriched clay at the Cretaceous-Tertiary boundary, and in carbonate and marl from 5 cm below and 3 cm above the boundary. Samples were leached with acetic acid to remove carbonate, and with hydrochloric acid. Leachates and residues were measured. The Sr, Nd, O and H isotopic compositions of the boundary clay residues are distinct from those of the stratigraphically neighboring materials. The data indicate that most of the clay material was derived from a terrestrial source with relatively low 87Sr/ 86Sr and high 143Nd/ 144Nd ratios. The δ 18O data suggest that the detritus has been modified by submarine weathering. K-Ca and Rb-Sr systematics, as well as O isotope ratios of K-feldspar spherules within the boundary clay, suggest that they are predominantly authigenic and may have formed after the time of deposition. However, Sm-Nd and Rb-Sr isotopic data indicate that the spherules contain relict material that provides information on the nature of the original detritus. The isotopic evidence for foreign terrestrial detritus in the boundary clay, the low rare earth element concentrations and high Ni concentration, support the hypothesis of a terminal Cretaceous asteroidal impact that produced a global layer of fallout. The data are most easily explained if the impact site was on oceanic crust rather than continental crust, and if a substantial fraction of the fallout was derived from relatively deep within the lithosphere (>3 km). This would probably require a single large impactor.

Magnetostratigraphy, biostratigraphy and geochronology of Cretaceous–Tertiary boundary sediments, Red Deer Valley

Magnetostratigraphy, biostratigraphy and geochronology of Cretaceous–Tertiary boundary sediments, Red Deer Valley

Magnetostratigraphy, biostratigraphy and geochronology of Cretaceous–Tertiary boundary sediments, Red Deer Valley (reply)

Magnetostratigraphy, biostratigraphy and geochronology of Cretaceous–Tertiary boundary sediments, Red Deer Valley (reply)

Magnetostratigraphy, biostratigraphy and geochronology of Cretaceous–Tertiary boundary sediments, Red Deer Valley

Integrated magnetostratigraphic and biostratigraphic data for continental Cretaceous–Tertiary boundary sediments in Alberta allow a correlation with recognised sea floor magnetic anomalies 29 and 30. When compared with data from the marine Gubbio section in Italy, the correlation indicates that extinction of the dinosaurs on land was synchronous with foraminiferal extinctions in the sea which are equated with the Cretaceous–Tertiary boundary. We advocate that the base of anomaly 29 be tentatively accepted as the best worldwide physical approximation of the Cretaceous–Tertiary boundary. Eleven K–Ar dates on bentonite sanidines near this boundary yield a mean age of 63.1 ± 0.5(2σ) Myr.