Cretaceous extinction event

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). 

CourtiUot V., Jaeger 1.1., Yang Z. Z., Feraud G., and Hofmann C. K. B. (1996) The influence of continental flood basalts on mass extinctions where do we stand In The Cretaceous-Tertiary Event and Other Catastrophes in Earth History, Geological Society of America Special Paper 307 (eds. G. Ryder, D. Fastovsky, and S. Gartner), pp. 513-525. 

HaUam A. (1987a) End-Cretaceous mass extinction event argument for terrestrial causation. Science 238, 1237-1242. 

Perhaps the best known of these extinction events occurred at the Cretaceous—Tertiary boundary (KTB), which left a clear signature in the C isotopic record. As we have seen in Section 5.8, the preferential assimilation of 12C02 during photosynthesis leaves surface waters depleted in the lighter C isotope, but... 

The end of the Permian Period is defined by the extinction of about 90% of all life forms that existed on the Earth at that time. This catastrophe was even more severe than the extinction event that defines the end of the Cretaceous Period which resulted from the profound environmental disturbance caused by the impact of an asteroid at Chicxulub on the Yucatan Peninsula of Mexico. The cause of the Permo-Triassic extinction could have been a dramatic fluctuation of the global climate, or of sealevel, or the impact of an asteroid or comet, or severe volcanic activity, or all of the above. 

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... 

The end of the Cretaceous period is marked by a major extinction event. Though not as great as the extinction event at the end of the end of the Triassic period, as many as fifty percent of the Earth s species became extinct. Nevertheless it caused the demise of the dinosaurs and was the end of the age of reptiles. Why this event occurred is contentious but there may have been an asteroid impact which created the Chicxulub crater off the Yucatan peninsula, Mexico. The pterosams, many marine reptiles, some groups of foraminifera and ammonites also became extinct. 

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. 

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