Tertiary extinctions cretaceous, cause

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). 

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. 

Alvarez L. W., Alvarez W., Asaro F., and Michel H. V. (1980) Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 208, 1095—1108. 

Professor MacLeod is an internationally recognized leader in many areas of palaeontology. Prominent among these are (1) morphometries (the quantitative analysis of form variation), (2) the causes of Phanerozoic extinction events and (3) quantitative stratigraphical data analysis. Through his work in these areas, he has made significant contributions to the punctuated-equilibrium controversy and the Cretaceous-Tertiary extinction controversy, as well as being personally responsible for the development of several new morphometric data-analysis techniques. He is the co-editor of... 

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. 

Pope K. O. (2002) Impact dust not the cause of the Cretaceous-Tertiary mass extinction. Geology 30, 99-102. 

The last globally catastrophic collision between Earth and an asteroid probably took place 65 million years ago at the end of the Cretaceous period. It now seems reasonably likely that the extinction of many species, including the great dinosaur extinction which occurred at the Cretaceous-Tertiary boundary, was caused by the impact of an asteroid approximately 6.2 mi (10 km) in diameter. The submerged remnants of the giant impact crater produced in this terminal Cretaceous collision were recently discovered on the coast of the Yucatan peninsula in Mexico. The crater, Chixulub (pronounced CHIKS-a-lub), is approximately 112 mi (180 km) in diameter and has long been buried under coastal sediments. 

There are two main models that attempt to explain the success of the dinosaurs. According to one, dinosaurs out-competed the mammal-like reptiles over a long period of time due to superior adaptations such as upright walking. The other model, which is supported by fossil evidence, says that the dinosaurs took advantage of openings created by two mass extinctions. By the end of the Triassic, dinosaurs had taken over the land. They were dominant for 165 million years, from the Late Triassic until their extinction at the Cretaceous-Tertiary (K-T) boundary some 65 million years ago. This massive extinction may have taken place in only a week or lasted for tens of thousands of years this has not been determined yet, but further study may provide an answer. One prominent theory for the cause of this... 

The efficiency of this method was again demonstrated by Bekov et al. (1988) when detecting Rh traces in natural samples. Extraordinarily high concentrations of iridium and other siderophiles were discovered in the Cretaceous/Tertiary (K/T) boundary deposits and interpreted (Alvarez et al. 1980) as a result of a large extraterrestrial body falling upon the Earth, causing mass extinction of the biota dominant in the... 

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