Cretaceous-Tertiary Boundary Event Research Articles

SKELTON, P. W., SPICER, R. A., KELLEY, S. P. & GILMOUR, I. 2003. The Cretaceous World. 360 pp. Cambridge, New York, Melbourne: Cambridge University Press for the Open University. Price £75.00, US $110.00 (hard covers), £27.95, US $50.00 (paperback). ISBN 0 521 83112 1; 0 521 53843 2 (pb)

The Cretaceous World is a well-constructed book with the high level of production values we have come to associate with offerings from the Open University: lucid text with explanations that bend over backwards to be systematic, logical and enlightening; well-designed diagrams exhibiting a deft use of colour; exemplary photographs; carefully chosen references; and a useful index. Edited and partly written by Peter Skelton, the book also contains key contributions by Iain Gilmour, Simon Kelley and Bob Spicer. There is an accompanying website that hosts sample pages, some illustrations to download (though not perhaps the most valuable ones!) and worked exercises. The book comprises thirteen chapters covering such topics as Cretaceous palaeogeography, climate, marine and terrestrial biota, carbonate platforms, biogeochemical cycles, volcanism, the carbon cycle and the Cretaceous–Tertiary boundary event. Cretaceous strata from around …

Fireball passes and nothing burns—The role of thermal radiation in the Cretaceous-Tertiary event: Evidence from the charcoal record of North America: Comment and Reply

The suggestion that globally extensive wildfires were ignited as part of the Cretaceous-Tertiary (K-T) boundary events (e.g., [Robertson et al., 2004][1]; [Melosh et al., 1990][2]; [Kring and Durda, 2002][3]) ignores the following: (1) absence of above background levels of charcoal, (2) absence of

Evolution of the Amba Dongar Carbonatite Complex: Constraints from 40Ar-39Ar Chronologies of the Inner Basalt and an Alkaline Plug

The Amba Dongar carbonatite-alkaline complex is one of several alkaline complexes present within the Chhota Udaipur subprovince of the Deccan flood basalt province, western India. Despite previous geochronological studies, the evolutionary history of this complex had remained uncertain due to lack of precise age data for the tholeiitic basalts that are exposed within and outside the ring dike of the complex. Also, ages of many alkaline plugs of the subprovince had remained unknown. Here we report results of 40Ar-39Ar dating of the basalt exposed inside the ring dike at Amba Dongar and phonolite from an alkaline plug located at Tawa at the northernmost edge of the subprovince; the analyses yield plateau ages of 68.5 ± 0.9 and 65.2 ± 0.7 Ma, respectively. These results not only suggest that the basalts present inside the Amba Dongar complex predate the complex itself, but also confirm the earlier view that all the alkaline activity in the Chhota Udaipur subprovince was contemporaneous. This in turn has significant implications for the contributions of CO2 and SO2 into the atmosphere at the time of the Cretaceous-Tertiary boundary events.

Climatic effects of an impact-induced equatorial debris ring

[1] Several theoretical and laboratory studies suggest that some large impact events are capable of inserting material into space depending on mechanics of the impact. This material would quickly coalesce to form a temporary debris ring in orbit around the equator, which would cast its shadow on the winter hemisphere. The results of an atmospheric general circulation model (GCM) simulation where an orbiting equatorial debris ring is applied as a boundary condition to the model show how the longer-term effects of a major impact could affect the climate system. The primary effect is a severe cooling in the tropics and the subtropics, especially under the seasonally migrating ring shadow. The globe cools and becomes drier, with the exception of monsoonal regions that become wetter. The Hadley cell is weakened resulting in drier tropics and weaker subtropical high-pressure cells in the winter hemisphere. Because the tropics cool more than middle latitude regions, the equator-to-pole temperature gradient becomes shallower resulting in weaker tropospheric winds and less high-latitude storminess. We suggest that the late Eocene impact(s) (35.5 Ma) could have generated a geologically temporary orbiting debris ring based on the global distribution of tektites associated with these events and patterns of climate change immediately above the iridium/microtektite layer. The Cretaceous-Tertiary boundary event, while larger, did not produce a debris ring. We also suggest that an opaque debris ring could have acted as the trigger to at least one episode of global glaciation during the Neoproterozoic.

A short duration of the Cretaceous-Tertiary boundary event: evidence from extraterrestrial helium-3.

Analyses of marine carbonates through the interval 63.9 to 65.4 million years ago indicate a near-constant flux of extraterrestrial helium-3, a tracer of the accretion rate of interplanetary dust to Earth. This observation indicates that the bolide associated with the Cretaceous-Tertiary (K-T) extinction event was not accompanied by enhanced solar system dustiness and so could not have been a member of a comet shower. The use of helium-3 as a constant-flux proxy of sedimentation rate implies deposition of the K-T boundary clay in (10 +/- 2) x 10(3) years, precluding the possibility of a long hiatus at the boundary and requiring extremely rapid faunal turnover.

The calcareous reef alga Halimeda (Chlorophyta, Byropsidales): a cretaceous genus that diversified in the cenozoic

The genus Halimeda (Order Bryopsidales) is an important contributor of calcareous sediments to present day reefs. By ∼80 million years ago the genus appeared to have achieved limited distribution in both Old and New Worlds; today its 33 extant species are widely distributed throughout the tropics. Halimediform genera of the Ordovician exhibit considerable morphological similarity to the modern genus. However, the first records of Halimeda fossils appear to be Permian, with the greatest pre-Cenozoic species diversity being achieved during the latter part of the Cretaceous. The long paleohistory is capped by an apparent burst of speciation associated with the Holocene. At least three time periods during the ca. 260Mya of Halimeda history are likely to have had major impacts on evolution of the genus: (1) Cretaceous-Tertiary boundary events; (2) closing of the circumtropical Tethyan seaway with associated Messinian crisis; and (3) final closure of the Panama seaway. However, little concerning the relationship of these events to Halimeda phylogeny can be gleaned from its recorded paleohistory. The first strong phylogenetic data for the genus, provided by cladistic analyses of 18sDNA sequences, identify principal lineages corresponding to the three major taxonomic sections (Rhipsalis, Opuntia and Halimeda). These lineages provide the major axes of a proto phylogeny, and represent an apparent differentiation of the genus into at least 3 basic thallus designs. The most complex of the phylogenetic trees presented also indicates a geographic separation of rhipsalian species into Atlantic and Pacific clades. It is likely that these two major events occurred during the Cenozoic, with the second associated with a vicariant event such as the cessation of the circumglobal Tethys current. Research by paleontologists is especially needed for developing time references for major evolutionary events which will lead to setting an evolutionary clock for Halimeda independent of molecular data. Paleontologists also have an important role to play in testing the hypothesis that the burst of speciation in the Holocene is an artifact of differential collection, differential preservation or both, and that some of this speciation occurred in preceeding epochs. Investigation of these hypotheses, coupled with better samples, will reveal much more of the history of the genus during the period of its greatest success, the Cenozoic.

Late Maastrichtian age of spherule deposits in northeastern Mexico: implication for Chicxulub scenario

In the La Sierrita area of Nuevo Leon, Mexico, three spherule layers are present and separated from the overlying siliciclastic deposits by up to 6 m of pelagic marls. The marls are of latest Maastrichtian age (Plummerita hantkeninoides (CF1) Zone, Micula prinsii Zone) and deposited under normal pelagic conditions with no significant evidence of reworking or slumping. Original deposition of the spherule layers occurred during the last 300 ka of the Maastrichtian and well prior to the Cretaceous-Tertiary (K–T) boundary event. Thus, if the spherules in northeastern Mexico provide critical evidence of an impact at Chicxulub, this impact predates the K–T boundary.

Geochemical Markers of the Cretaceous-Tertiary Boundary Event at Brazos River, Texas, USA

The Cretaceous-Tertiary boundary sites around the Gulf of Mexico are close to the Chixculub impact site and are relatively well studied, yet much remains to be learned about them. Therefore, the first integrated study of carbon, soot, and fullerenes in a Cretaceous-Tertiary boundary section was undertaken at the Brazos-1 site on the Brazos River in Texas at the most complete section of end Cretaceous and basal Paleocene deposits on the Texas segment of the Gulf Coast area. Up to 409 ppm of native sulfur (S o) were serendipitously discovered in a spherule-bearing unit of the BR-1 section, and lesser amounts were found in spherule-bearing units of nearby Brazos riverbed sections in a section on Darting Minnow Creek. The isotopic composition, δ 33S = −12.97‰, δ 34S = −24.89‰, and δ 36S = −46.4‰, implies that this S o cannot have come to Earth by the impactor that formed the Chicxulub crater, but, most likely, was produced by sulfate-reducing bacteria during a local, transient bacterial bloom for which the sulfate was provided by CaSO 4-bearing spherules. Carbon and soot were determined in twelve samples representing all units of BR-1 from the Cretaceous Corsicana/Kemp Formation to the Tertiary Kincaid Formation. A significant increase of C and soot contents, up to 2.2×10 4 ppm and 1.4×10 4 ppm, respectively, occurs in a sandy bed at the top of the KT complex. Fullerenes were determined in fifty-four samples from all units of the same BR-1 section. Less than 1 ppb was reliably detected at the same sandy bed where the strongest Ir anomaly of the section is known to occur. It is suggested here that the Chicxulub impact 65 Ma ago ignited local wildfires that produced C, soot, and fullerene, which settled onshore, or near-shore, whence they were transported to the Brazos site by coastal flooding and associated sediment-laden water plumes moving offshore.

High-resolution late Maastrichtian–early Danian oceanic 87Sr/86Sr record: Implications for Cretaceous-Tertiary boundary events

A high-resolution late Maastrichtian–early Danian seawater 87 Sr/ 86 Sr reference curve is constructed from two Cretaceous-Tertiary boundary (K-T boundary) sections: Bidart (France) and El Kef (Tunisia). The 87 Sr/ 86 Sr curve shows maxima at 0.3–0.4 Ma before the K-T boundary and at the K-T boundary. The first maximum could mark the onset of a major outflow of the Deccan Traps. The second maximum, a rapid 0.000 06 87 Sr/ 86 Sr, shift, extends from ∼3–4 m below to ∼1 m above the K-T boundary. This profile probably results from diagenetic smoothing of an originally sharp K-T boundary 87 Sr/ 86 Sr anomaly, rather than from a gradual process. The sharp shift could result from (1) the vaporization of the Chicxulub target rocks, (2) global wildfires, and (3) acid-rain leaching of soils and sialic surface rocks. Of these three possibilities, only Sr release by soil leaching combined with increased rainfall associated with the K-T event appears to be sufficiently large to produce the observed K-T 87 Sr/ 86 Sr anomaly.

Iridium concentration as an estimation of instantaneous sediment accumulation rates

Ir concentrations and mass accumulation rates from nine deep-sea cores, one from the Atlantic Ocean and eight from the Pacific Ocean, were compiled to evaluate a new technique for determining mass accumulation rates. The technique is based on the large difference of the high Ir abundance in extraterrestrial matter versus the low Ir contents in terrestrial material. Assuming a constant flux of cosmic matter, this difference leads to high Ir concentrations in slowly accumulating sediments, versus low Ir concentration in rapidly accumulating sediments. The method is independent of stratigraphic control, and does not require knowledge of age of the deposit. We note that Ir concentrations in some slowly accumulating sediments are of the same order of magnitude as some of those reported for the Cretaceous-Tertiary boundary event.

Phenotypic experiments into new pelagic niches in early Danian planktonic foraminifera: aftermath of the K/T boundary event

Abstract In the aftermath of the Cretaceous-Tertiary (K/T) boundary event it appears that unusual phytoplankton blooms were boosted by the abundant nutrient levels left over from a short-lived ‘Strangelove Ocean’ period, which possibly gave rise to the negative-to-positive δ 13 C surface-to-bottom gradient in the Danian. The highly plastic morphology of the planktonic foraminifera at the base of the Palaeocene appeared, most likely, as an adaptive response of functional morphology to the pelagic habitat of the species and its mode of life. The diversification episodes of Danian planktonic foraminifera appear to correspond to times of reduced oceanic mixing, stratified water masses, recovery of the surface water productivity and a progressive expansion of the trophic-resource continuum, with periods of maximum diversity corresponding to widespread oceanic surface-water oligotrophic conditions. These suggest a parallel adaptive trend of feeding strategies caused by the changing availability of nutrients in the water column, with probable increasing reliance in symbiosis under low nutrient conditions later in the Danian. Guembelitria cretacea , one of the few Cretaceous survivors, has been recorded in northeastern Brazil up to the lower part of the P2 Zone. A triserially coiled planktonic morphotype, this species started to diversify immediately after the K/T transition. After only a few thousand years, in the earliest Danian, the first Tertiary taxa (the Guembelitria- Woodringina lineage) appeared; these are microperforate nonspinose forms that were probably restricted to shallow epipelagic waters. There is a trend towards uncoiling of the triserial pattern by progressively changing the positioning of the aperture, without any detectable ecophenotypic preference at first. The first specimens of the Eoglobigerina-Pseudosubbotina, Eoglobigerina-Subbotina and Praemurica lineages, cancellate spinose and non-spinose forms, also evolved in the Danian in a nearly coeval and parallel evolutionary trend from a probably ancestral Hedbergella stock. A revised phylogeny is suggested for the early Palaeocene planktonic foraminifera based on recorded stratigraphic ranges and morphological affinities (chamber arrangement and surface texture ornamentation).

Palynology of the Cretaceous-Tertiary boundary in the Scollard Formation of Alberta, Canada, and global KTB events

The present work is based on a restudy of 12 samples collected across the Cretaceous-Tertiary boundary (KTB) from Scollard Locality 2, Alberta, Canada. The KTB occurs at the Nevis coal seam near the top of the Scollard Formation that conformably overlies the Battle Formation. A progressive cooling trend in the prevailing subtropical climate of the Edmonton Group initiated floral changes in the Whitemud Formation underlying the Battle, i.e. about 0.9 Myr before the KTB. The dinosaurs and megaflora of the Scollard are distinct from those of the underlying formations of the Edmonton Group. The floral extinctions were selective and gradual across the KTB in Scollard until a temperate Tertiary flora was established at 1090 cm above or by about 0.38 Myr after the last dinosaur record. The source of the Ir normally does not appear to have affected the flora catastrophically. A fern spore abundance (FSA) occurs above the Ir anomaly in the Nevis coal seam and another one is recognized here in the early Maastrichtian Drumheller coal seam of the Horseshoe Canyon Formation. These FSA's may represent a primary succession of terrestrial plant communities on the land vacated by marine regressions. Global Cretaceous-Tertiary boundary events, such as atmospheric CO 2 concentration, extraterrestrial impact, iridium anomaly, volcanic activity, and marine fluctuations are reviewed to assess their influence on biotic extinction. Climatic deterioration and a drastic worldwide marine regression stand out as the major causes for rapid extinctions in the terminal Cretaceous.

Formation of spinels in cosmic objects during atmospheric entry: a clue to the Cretaceous-Tertiary boundary event

Magnetic spinels produced by oxidation of extraterrestrial objects in the atmosphere have a composition distinct from terrestrial spinels. They are characterized by a high iron oxidation state, arising from crystallization under high oxygen fugacities, and a high nickel concentration due to the relatively high abundance of this element in extraterrestrial material. The iron oxidation state increases from micrometeorites, to meteoroid ablation material and to impact-generated products. This reflects a progressive increase of the oxygen fugacity, corresponding to decreasing altitudes of crystallization. Spinels found at the Cretaceous-Tertiary boundary are similar to those that crystallized from meteoroid ablation material and impact-generated products, supporting the view that a collisional event did occur at the end of the Cretaceous.

Sixty-five-million-year-old flowers bearing pollen of the extinct triprojectate complex—a Cretaceous-Tertiary boundary survivor

Fossil flowers bearing pollen of Kurtzipites trispissatus Anderson have been recovered from the Paleocene Ravenscrag Formation, southwestern Saskatchewan, Canada. The flowers occur in clays about 7.0 m above the coal-zone associated with the Cretaceous-Tertiary boundary and represent a lineage that survived the Cretaceous-Tertiary boundary extinction event. Flowers are globular in shape, about 6.0 mm in diameter, and without an obvious perianth. All flowers are staminate and unisexual with numerous stamens inserted on a disk-shaped receptable. The stamens are long, narrow and basifixed; the filaments are short, the anthers are long ans slender and filled with K. trispissatus pollen. Pollen grains are tricolporate, about 20 μm in diameter, the exine tectate and scabrate, the endexine apparently restricted to the apertural region. This putatively anemophilous palynomorph is one of the few members of the mainly zoophilous triprojectate complex to survive the Cretaceous-Tertiary boundary event. Flower morphology supports the anemophilous reproductive strategy previously inferred for the plants producing Kurtzipites, suggesting that an anemophilous habit may have had selective advantage in the triprojectate complex, and perhaps other groups, at the Cretaceous-Tertiary boundary. The fossil flowers, hereassigned to Kurtziflora antherosa gen. et sp. nov., belong to a taxon that apparently became extinct during the Paleocene leaving no modern relatives.

Modeling Cretaceous‐Tertiary boundary events with extant photosynthetic plankton: effects of impact‐related acid rain

Griffis, K. & Chapman, D. J. 1990 10 15: Modeling Cretaceous-Tertiary boundary events with extant photosynthetic plankton: effects of impact-related acid rain. Lethaia, Vol. 23, pp. 379–383. OSIO. ISSN 0024–1164. An acid rain phenomenon has previously been proposed as one of the consequences of a bolide impact contributing to the extinctions at the Cretaceous-Tertiary boundary. This hypothesis has been tested by observing the growth responses of four organisms under simulated acid rain conditions. Two of these phytoplankton, Ditylum (a diatom) and Thoracosphaera (a dinoflagellate). are genera that persisted through the boundary, while the other two, Coccolithus (a coccolithophorid) and Gonyaulax (a dinoflagellate), are post-boundary genera. Ditylum and Coccolithus survive the acid rain simulation. but with the loss of scales in Coccolithus. The two dinoflagellate are sensitive to acid rain simulations. with Gonyaulax unable to survive beyond seven days. The results indicate that acid rain may have contributed to the Cretaceous-Tertiary boundary extinctions. but that the changes resulting from the acid rain were not as severe as postulated or were short-lived and quickly dissipated. ▭Acid rain, coccolithophorids. Cretaceous/Tertiary extinctions, diatons, dinoflagellates, phytoplankton.

Precessional climate cyclicity in Late Cretaceous—Early Tertiary marine sediments: a high resolution chronometer of Cretaceous-Tertiary boundary events

We report well-dated Late Cretaceous and Early Tertiary precessional climatic cycles, recorded by rhythmic carbonate maxima and minima in South Atlantic deep sea sites. Spectral analyses of digitized sediment color, a suitable carbonate proxy, show prominent regularities in the spacing marl-carbonate beds. Magnetostratigraphic dating over a number of magnetic chrons constrains the duration of the cycles, which can be detected over at least 20 Myr of sedimentation at 7 coring locations. Their mean absolute period of 23.5 ± 4.4kyr agrees closely with the predicted late Cretaceous precessional period of 20.8 kyr. Because they can be matched to a physical forcing mechanism with a known repeat time, the cycles offer a new high-resolution tool to measure rates of climate change before and after the Cretaceous-Tertiary (K/T) boundary. From counts of carbonate cycles, we derive the position of the K/T boundary within C29R at 350 kyr after the base of the reversal. The constancy of cycle thickness (linearly related to sedimentation rate) and amplitude up to the “boundary clay” does not give evidence for climate instability preceding the boundary. Orbital chronometry records a step-function decrease in sediment accumulation rate at the Cretaceous-Tertiary boundary that is consistent with a geologically instantaneous event.

Changes in floral diversities, floral turnover rates, and climates in Campanian and Maastrichtian time, North Slope of Alaska

One-hundred-and-ten angiosperm pollen taxa have been found in upper Campanian to Masstrichtian rocks of the Colville River region, North Slope of Alaska. These are the highest paleolatitude Campanian and Maastrichtian floras known from North America. Total angiosperm pollen diversity rose during the Campanian and declined toward the end of the Maastrichtian. However, anemophilous porate pollen of the Betulaceae-Myricaceae-Ulmaceae complex increased gradually in diversity during the late Campanian and Maastrichtian and into the Paleocene. Turnover of angiosperm taxa was active throughout most of late Campanian and Maastrichtian time; rapid turnover affected mainly the taxa of zoophilous herbs, representing an bundant but ecologically subordinate element of the vegetation. Last appearances of pollen taxa during the late Campanian and Maastrichtian probably represented mainly extinctions rather than emigrations; end- Cretaceous angiosperm extinctions in the North American Arctic began well before the Cretaceous-Tertiary boundary event. The last appearances in the late Maastrichtian took place in bursts; they appear to represent stepwise rather than gradual events, which may indicate the existence of pulses of climatic change particularly in late Maastrichtian time.

Erratum: Microscopic planar features in quartz from Scollard Canyon, Alberta, and the Cretaceous–Tertiary boundary event

Quartz grains separated from the Cretaceous–Tertiary (K/T) boundary clay at Scollard Canyon, Alberta, have prominent, microscopic planar features. These occur in 15–30% of the grains from the lower...

Cretaceous-Tertiary boundary event: Evidence for a short time scale

Three non-meteoritic trace elements (Sb, As and Zn) are strongly enriched at eleven K-T boundary sites, along with mainly or partly meteoritic elements (Ir, Ni, Cr, Fe and Co). The proportions (As, Sb, Zn/Ir) are remarkably constant over a ≈ 100-fold range in concentration. This correlation persists in sub-layers of boundary clay and even extends to soot (from burned land biomass). Apparently, all the components, despite their diverse origins, became associated in a single, global component prior to deposition. No wholly satisfactory source is available for As, Sb and Zn: the trace element pattern in volcanic gases does not match that in KT boundary clay, with ratios to Ir falling short by 1 to 2 orders of magnitude, terrestrial rocks do not reach high enough concentrations and (modern) ocean water contains too little Zn, but on balance, the latter source seems preferable—perhaps augmented by volatiles from the impact crater. Apparently, Ir-bearing ejecta and soot from forest fires coagulated in the stratosphere and then fell out together, sweeping out oceanic biomass and anoxically precipiting As, Sb and Zn. Significantly, the amounts of marine and land biomass at the KT boundary correspond to about the steady-state global inventory (1 generation), and the amounts of As, Sb and Zn are also within a factor of ≈5 of the global inventory. This is expected in a catastrophic but not a gradualist scenario.

Microscopic planar features in quartz from Scollard Canyon, Alberta, and the Cretaceous–Tertiary boundary event

Quartz grains separated from the Cretaceous–Tertiary (K/T) boundary clay at Scollard Canyon, Alberta, have prominent, microscopic planar features. These occur in 15–30% of the grains from the lower 1.5 cm of the boundary clay. They commonly correspond to the ω and π orientations found at known meteorite impact sites and differ from deformation features produced by other dynamic geologic processes. Basal planar features, however, are absent here and at other K/T sites. One possible explanation is that quartz at boundary sites is an incomplete sample of shocked quartz from the postulated K/T impact and unshocked detrital quartz. The source of the shocked quartz most likely was close to the point of impact and near surface. This and previous isotopic data suggest the K/T target site contained a relatively thin upper unit of quartz-bearing crystalline rocks overlying basaltic material, corresponding possibly to thinned continent or a continental margin.