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... Science Frontiers ONLINE No. 18: Nov-Dec 1981 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Iridium-rich layers and catastrophism Kyte et al have discovered a 2.3 -millionyear-old sedimentary layer under the Antarctic Ocean that contains iridium and gold concentrations comparable to those in the Cretaceous-Tertiary boundary. The noble metals are mostly contained in millimeter-sized grains that resemble ablation debris from a large extraterrestrial object. Unlike the Cre taceous-Tertiary episode, however, the newly found layer is not accompanied by evidence of mass biological extinctions. (Kyte, Frank T., et al; "High Noble Metal Concentrations in a Late Pliocene Sediment," Nature, 292:417, 1981.) Comment. Perhaps those ... who deny the existence of sudden biological extinctions at the CretaceousTertiary boundary are correct and something else besides catastrophism impacted terrestrial life at that juncture. Reference. The implications of iridium "spikes" are found in Category ESB1 in our Catalog: Anomalies in Geology. To order, go to: here . From Science Frontiers #18, NOV-DEC 1981 . 1981-2000 William R. Corliss ...
Terms matched: 2 - Score: 60 - 15 May 2017 - URL: /sf018/sf018p09.htm
... Science Frontiers ONLINE No. 60: Nov-Dec 1988 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Global fire at the k-t boundary The worldwide deposit of iridium at the K-T (Cretaceous-Tertiary) boundary has been considered very strong evidence that a large astronomical object (asteroid or comet) devastated our planet some 65 million years ago. Some scientists, however, propose that the iridium layer was instead deposited through widespread volcanic activity. The proponents of an astronomical mechanism should be heartened by a recent paper in Nature, by W.S . Wolbach et al. Here is their Abstract: "Cretaceous-Tertiary (K -T ) boundary clays from five sites in Europe and New Zealand are 102 -104 - ... :665, 1988.) Comment. Unmentioned in the above article is the possibility that extensive wildfires might have been generated by volcanic eruptions, perhaps accompanied by great electrical storms. The 1988 fires in Yellowstone needed no meteoric impact. Reference. Chemical anomalies in the earth's crust are cataloged in ESC1 in Anomalies in Geology. To order this catalog volume, visit: here . Concentration "spikes" of iridium, elemental carbon and soot at the KT boundary, Woodside Creek, New Zealand. (Adapated from Nature, 334:665, 1988). From Science Frontiers #60, NOV-DEC 1988 . 1988-2000 William R. Corliss ...
Terms matched: 2 - Score: 49 - 15 May 2017 - URL: /sf060/sf060p11.htm
... pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Asteroid impact or volcanos?The debate over the real cause of the terrestrial catastrophism that occurred at the Cretaceous-Tertiary boundary, some 65 million years ago, grinds on. Some physical scientists claim rather imperiously that the dinosaurs and many other species were done in by the impact of a huge asteroid/meteorite. The worldwide iridium spike is conclusive, they say. Many paleontologists and geologists, however, remain unconvinced and prefer widespread volcanism. We have already covered the various arguments in past issues of Science Frontiers; here, we want to advise our readers that a pair of excellent articles by principals in this debate have appeared in Scientific American. Generally speaking, it seems that the proponents of the impact theory are now ... to the other side. For example, multiple impacts are now proposed to account for evidence of the type introduced below. (Alvarez, Walter, and Asaro, Frank; "An Extraterrestrial Impact," Scientific American, 263:78, October 1990. Also: Courtillot, Vincent E.; "A Volcanic Eruption," Scientific American, 263:85, October 1990.) A spike dulled. The case for a single asteroid/meteorite impact has been weakened by a recent reexamination of the classic exposure of the CretaceousTertiary boundary at Gubbio, Italy. Here, the discovery of an iridium "spike" at the boundary was thought to betoken a sudden, catastrophic, extraterrestrial event. On further study, though, the spike no longer seems so sharp. In fact, it ...
Terms matched: 2 - Score: 113 - 15 May 2017 - URL: /sf073/sf073g09.htm
... Science Frontiers ONLINE No. 67: Jan-Feb 1990 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Microorganisms complicate the k-t boundary Ancient bacteria, it appears, have tampered with the K-T (Cretaceous-Tertiary) boundary of some 65 million years ago. A key marker of this boundary is a thin "spike" of iridium that is found worldwide, and which was supposedly deposited by the asteroid impact that helped finish off the dinosaurs. For many scientists, the asteroid-impact scenario has become a "non-negotiable" brick in the Temple of Science. The problem they have faced is that the iridium layer is variable in thickness and concentration from site to site. Sometimes iridium can be detected well above and ... Science Frontiers ONLINE No. 67: Jan-Feb 1990 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Microorganisms complicate the k-t boundary Ancient bacteria, it appears, have tampered with the K-T (Cretaceous-Tertiary) boundary of some 65 million years ago. A key marker of this boundary is a thin "spike" of iridium that is found worldwide, and which was supposedly deposited by the asteroid impact that helped finish off the dinosaurs. For many scientists, the asteroid-impact scenario has become a "non-negotiable" brick in the Temple of Science. The problem they have faced is that the iridium layer is variable in thickness and concentration from site to site. Sometimes iridium can be detected well above and ...
Terms matched: 2 - Score: 94 - 15 May 2017 - URL: /sf067/sf067g13.htm
