Cretaceous/Tertiary

Cretaceous-Tertiary vein, skarn kuroko deposits in Japan... 

It is shown in Fig. 2.57 that the lead isotopic variation of the Besshi-subtype is similar to that of midoceanic ridge basalt, suggesting the lead in the Besshi-subtype was derived from mantle. The data from the Shimokawa, and Yanahara deposits (Group B) are slightly more radiogenic than Group A, suggesting that crustal lead was involved in the formation of the Shimokawa deposit, and lead isotopic values for the Shimokawa and Yanahara plot between MORB and Cretaceous-Tertiary deposits in Japan (Kuroko, skarn, vein-type deposits). 

Chemical and Physical Measurements Relevant to the Cause of the Cretaceous—Tertiary Extinctions1... 

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. 

There have been a number of suggestions in the past that an extraterrestrial object impacting on the. earth caused or could cause massive extinctions of life. E. J. Opik [11], for example, discussed the lethal effects which could be caused by the heat generated from such objects striking the earth, and H. C. Urey [12] stated specifically that a comet was probably the cause of the Cretaceous-Tertiary extinctions. There have also been science fiction stories and a movie relating to the effects. The events likely to occur if the sunlight were temporarily "turned off" have also been discussed [13]. Our deduction in contrast to the others is based on physical science data (the iridium anomaly) and is the only explanation we found which explained the Ir anomaloy could cause the massive extinction of life and was likely to occur in a period of 100 million years. 

Extraterrestrial Cause for the Cretaceous-Tertiary Extinction, Science 208, 1095-1108 (1980). 

Experimental Evidence in Support of an Extraterrestrial Trigger for the Cretaceous-Tertiary Extinctions, WS Trans. Am. Geophys. Union 60. 734 (1979). 

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). 

K-TEC group (P. Beland et al.), Cretaceous-Tertiary extinctions and Possible Terrestrial and Extraterrestrial Causes, Proceedings of Workshop, National Museum of Natural Sciences, Ottawa, 16 and 17 November 1976, pp. 144-149. 

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 et al. (1990) have measured the iridium content in Ocean Drilling Project hole 690 sediments from the Weddel Sea across the Cretaceous-Tertiary (K-T) boundary (Table 8.1). Depth z is relative to an arbitrary level in the core. Compare the reduced iridium flux at each depth down the core assuming the bioturbated layer is either 4 or 8 cm thick. 

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.,... 

Sheilds WR, Murphy TJ, Catanzaro EJ, Garner J (1966) Absolute isotopic abundance ratios and the atomic weight of a reference sample of chromium. J Res Natl Bur Standards 70A(2) 193-197 Shukolyukov A, Lugmair GW (1998) Isotopic evidence for the Cretaceous-Tertiary impactor and its type. Science 282(5390) 927-929... 

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... 

In recent years. Znller and associates University of Maryland) have studied six active volcanoes iAugustine, Mount St. Helens. El Chiehdn. Arcnal. Poas. and Colima) and have found no evidence of lr enrichment. The new Kilauea evidence of volcanic action as an Ir source tends to conflict with that of other researchers who have generally attributed the Ir anomaly to an extraterrestrial source, such as resulting from a cataclysmic meteorite or asteroid impact, notably in connection with (he Cretaceous-Tertiary [K i t boundary layer. 

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. 

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