Cretaceous/Tertiary boundary

The historical background is presented for the asteroid-impact theory that is based on the iridium anomaly found in rocks frm the Cretaceous-Tertiary boundary. Recent measurements of Ir, Pt, and Au abundances from such rocks in Denmark have shown that the element abundance ratios are different from mantle-derived sources and agree with values for chondritic meteorites within one standard deviation of the measurement errors (7-10%). Rare-earth patterns for these rocks are... 

We were not able to determine exactly the length of time associated with the deposition of the clay layer. Instead the laboratory studies on the chemical and physical nature of the Cretaceous-Tertiary boundary led to the theory that an asteroid collision with the earth was responsible for the extinction of many forms of life including the dinosaurs. 

Anomalous Iridium Levels at the Cretaceous-Tertiary Boundary at Gubbio, Italy Negative Results of Tests for a Supernova Origin, Geol. Soc. America Abstract 11. 378 (1979). 

Smit, J. and Hertogen, J., An extraterrestrial event at the Cretaceous Tertiary boundary, Nature 285, 198-200 (1980). 

Surlyk, Finn, The Cretaceous-Tertiary boundary event, Nature 285, 187-188 (1980). 

Ganapathy, R., A Major Meteorite Impact on the Earth 65 Million Years Ago, Evidence from the Cretaceous-Tertiary Boundary Clay, Science 209, 921-923 (1980). 

Michel, H. V., Asaro, F., Alvarez, W. Alvarez, L. W. (1990). Geochemical studies of the Cretaceous-Tertiary boundary in ODP holes 689B and 690C. Proc. ODP Sci. Res.,... 

Zhao, M. and Bada, J. L. (1989). Extraterrestrial amino acids in cretaceous/tertiary boundary sediments at Stevns Klint, Denmark. Nature, 339, 463-5. 

Fullerenes are rather easily oxidized, which explains the fact that, despite their commonplace occurrence in soots, they had escaped detection for so long. Fullerenes have now been found in Precambrian carbonaceous rocks from Karelia, Russia in breccias associated with the 1.85-billion-year-old Sudbury impact structure in Canada and in a sooty layer (believed to be due to fires from the asteroid impact that is thought to have killed off the dinosaurs) marking the Cretaceous-Tertiary boundary in New Zealand.8... 

Luck, J.M. and K.K. Turekian Osmium 187/Osmium 186 in Manganese Nodules and tile Cretaceous Tertiary Boundary, Science. 222, 613 615 (1983). 

Like iridium, arsenic is enriched in Cretaceous-Tertiary boundary shales from New Zealand (Brooks et al., 1984 Strong et al., 1987). The iridium is believed to have originated from an asteroid impact that caused the massive extinction at the end of the Cretaceous period about 65 million years ago. In contrast, most of the arsenic in the boundary shales probably had a terrestrial origin (Strong et al., 1987). The extinction of marine organisms, especially plankton, from the impact may have been responsible for increased anoxic conditions in the oceans, which led to the precipitation of arsenic in the marine deposits (Brooks et al., 1984), 541. 

Brooks, R.R., Reeves, R.D., Yang, X.-H. et al. (1984) Elemental anomalies at the Cretaceous-Tertiary boundary, Woodside Creek, New Zealand. Science, 226(4674), 539-42. 

Strong, C.P., Brooks, R.R., Wilson, S.M. et al. (1987) A new Cretaceous-Tertiary boundary site at Flaxbourne River, New Zealand biostratigraphy and geochemistry. Geochimica et Cosmochimica Acta, 51, 2769-77. 

Wolfe JA (1979) Temperature parameters of the humid to mesic forests of eastern Asia and their relation to forests of other regions of the Northern Hemisphere and Australasia. US Geol Surv Prof Pap 1106 1-37 Wolfe JA (1990) Palaeobotanical evidence for a marked temperature increase following the Cretaceous/Tertiary boundary. Nature 343 153-156... 

Another environment that has been successfully searched for nanodiamonds is the Cretaceous-Tertiary boundary layer. Carlisle Braman (1991) carried out the now time honoured acid dissolution procedure on samples from Knudsen s Farm, Alberta, Canada. They found 45 ppb of a white fraction 97 % carbon almost entirely 3-5 nm... 

Carlisle, D. B. Braman, D. R. 1991 Nanometre-sized diamonds in the Cretaceous/Tertiary boundary clay of Alberta. Nature, Lond. 352, 708-709. 

Gilmour, I., Russell, S. S., Arden, J. W., Lee, M. R., Franchi, I. A. Pillinger, C. T. 1993 Terrestrial carbon and nitrogen isotope ratios from Cretaceous Tertiary boundary microdiamonds. Science, Wash. (In the press.)... 

Venkatesan, M. I., and Dahl, J. (1989). Organic geochemical evidence for global fires at the Cretaceous/Tertiary boundary. Nature 338,57-60. 

A sharp increase in 3He and 3He/4He ratio around 35 million years is nearly synchronous with the well-known tektite horizons observed around the world. However, the Cretaceous/Tertiary boundary (K/T) which is easily recognized by a large Ir peak in the core is associated with essentially no 3He peak. Farley argued that decoupling of 3He and Ir in the core illustrates the fact that the two tracers of extraterrestrial fall-out were delivered to the sea floor from different sources and in different ways, perhaps by size bias of the carrier dusts. 

Zachos J.C., Arthur M.A. and Dean W.E. (1989) Geochemical evidence for suppression of pelagic marine productivity at the Cretaceous/Tertiary boundary. Nature 337, 61-64. 

CourtiUot V., Besse J., Vandamme D., Montigny R., Jaeger J. J., and Cappeta H. (1999) Deccan flood basalts at the Cretacous/ Tertiary boundary Earth P/anct. Sci. Lett. 80, 361—374. 

These phenomena were accompanied by an extinction event that resulted in the demise of 26% of all known genera (Sepkoski, 1986). Although the overall extinction rate is much lower than that at the Cretaceous-Tertiary boundary, deep water marine invertebrates fared much worse in the CTB event (Kaiho, 1994). This difference supports the view that anomalous oceanic volcanism around the CTB may have played a significant role in the environmental and biotic crisis at this time (Kerr, 1998). 

Caldeira K. and Rampino M. R. (1990) Deccan volcanism, greenhouse warming, and the Cretaceous/Tertiary boundary. In Global Catastrophes in Earth Elistory, Geological Society of America Special Paper 247 (eds. V. L. Sharpton and P. D. Ward), pp. 117-123. 

Prinn R. and Fegley B. (1987) Bolide impacts, acid rain, and biospheric traumas at the Cretaceous-Tertiary boundary. Earth Planet. Sci. Lett. 83, 1-15. 

There are characteristic chemical properties of cosmic dust that have been involved in the study of sediment accumulation rates. The platinum group elements, such as iridium and osmium, offer good examples. Attempts to use iridium in this way have had the important result of indicating a giant meteorite impact at the Cretaceous-Tertiary boundary (Alvarez et ai, 1980) but it has not been proven important in determining chronometry. 

Luck J. M. and Turekian K. K. (1983) Osmium-187/osmium-186 in manganese nodules and the Cretaceous-Tertiary boundary. Science 222(4624), 613-615. 

Zhou and Kyte (1992) provided the concentration data of major and trace elements in the top 24.5 m of Deep Sea Drilling Project hole 596 (located at 23°5l S, 169°39 W with a water depth of 5,700 m). This core contains the K/T (Cretaceous/Tertiary) boundary with characteristic high Ir anomaly, and major and trace element data are available for 65 down-core samples. The results of factor analysis on those samples are summarized in Figures 6(a)-(d) (elements with both factor loadings of less than... 

Barrera E. (1994) Global environmental changes preceding the Cretaceous-Tertiary boundary, Early-Late Maastrichtian transition. Geology 22, 877-880. 

Barrera E. and Keller G. (1990) Stable isotope evidence for gradual environmental changes and species survivorship across the Cretaceous/Tertiary boundary. Paleoceanography 5, 867-890. 

Hansen T. A., Upshaw B., Ill, Kauffman E. G., and Gose W. (1993) Patterns of molluscan extinction and recovery across the Cretaceous-Tertiary boundary in East Texas report on new outcrops. Cretaceous Res. 14, 685-706. 

Hildebrand A. R., Penfield G. T., Kring D. A., PiUdngton D., Camargo A., Jacobsen S. B., and Boynton W. V. (1991) Chicxulub crater, a possible Cretaceous-Tertiary boundary... 

Keller G. and Lindinger M. (1989) Stable isotopic, TOC and CaC03 record across the Cretaceous/Tertiary boundary at El Kef, Tunisia. Palaeogeogr. PalaeocUmat. Palaeoecol. 73,... 

Keller G. R., Barrera E., Schmitz B., and Mattson E. (1993) Gradual mass extinction, species survivorship, and longterm environmental changes across the Cretaceous-Tertiary boundary in high latitudes. Geol. Soc. Am. Bull. 105,... 

Kyte F. T., Smit J., and Wasson J. T. (1985) Siderophile interelement variations in the Cretaceous—Tertiary boundary sediments from Caravaca, Spain. Earth Planet. Sci. Lett. 73, 183-195. 

MacdougaU J. D. (1988) Seawater strontium isotopes, acid rain, and the Cretaceous—Tertiary boundary. Science 239, 485-487. 

MacLeod K. G., Huber B. T., and FuUagar P. D. (2001) Evidence for a small (approximately 0.000030) but resolvable increase in seawater Sr/ Sr ratios across the Cretaceous—Tertiary boundary. Geology 29, 303-306. 

Stott L. D. and Delaney M. L. (1988) Cd/Ca in benthic foraminifera and stable isotopes across the Cretaceous-Tertiary boundary at Site 690C (Leg 113), Weddell Sea, Antarctic. EOS 69, 1243. 

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