5 results found.
... Science Frontiers ONLINE No. 12: Fall 1980 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects The Rehabilitation Of Cuvier Cuvier (1769-1832) was a catastrophist. To him, the record of death in the layers of fossiliferous rocks was obviously the consequence of terrestrial convulsions. But Cuvier's ideas were swept aside by the uniformitarians who saw the earth and its cargo of life unfolding with almost agonizing slowness. But Cuvier is making a comeback, as illustrated by the following back-to-back articles in Nature. We quote from the abstracts. "Closely spaced samples from an uninterupted calcareous pelagic sequence across the Cretaceous-Tertiary boundary reveal that the extinction of planktonic Foraminifera and nannofossils was abrupt without any previous warning in the sedimentary record, and that the moment of extinction was coupled with anomalous trace element enrichments, especially of iridium and osmium. The rarity of these two elements in the crust of the Earth indicates that an extraterrestrial source, such as the impact of a large meteorite may have provided the required amounts of iridium and osmium." (Smit, J., and Hertogen, J.; "An Extraterrestrial Event at the Cretaceous-Tertiary Boundary," Nature, 285:198, 1980.) "Evidence is presented indicating that the extinction, at the end of the Cretaceous, of large terrestrial animals was caused by atmospheric heating during a cometary impact and that the extinction of calcareous marine plankton was a consequence of poisoning by cyanide released by the fallen comet and of a catastrophic rise in calcitecompensation depth in ...
Terms matched: 1 - Score: 24 - 15 May 2017 - URL: /sf012/sf012p08.htm
... Science Frontiers ONLINE No. 6: February 1979 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Humps Of Particles In The Gulf Stream Peculiar humps or hills of particulate material, thousands of feet long and hundreds high, have been observed in the Florida Current with ultrasensitive, 20-kilohertz sonar. The humps extend from the bottom of the oceanic mixed layer to near the surface. Sediment and plankton probably make up the humps, but the actual constitution and cause of the concentrations are unknown. Conceivably, currents could concentrate the particulate matter; so could some sort of coordinated, collective biological activity. (Proni, John R., et al; "Vertical Particulate Spires or Walls within the Florida Current and near the Antilles Current," Nature, 276:360, 1978.) From Science Frontiers #6 , February 1979 . 1979-2000 William R. Corliss ...
Terms matched: 1 - Score: 14 - 15 May 2017 - URL: /sf006/sf006p10.htm
... This Issue Sourcebook Project Sourcebook Subjects More Doubts About Asteroids In an apparent reaction to the stampede to climb aboard the extinction-by-asteroid bandwagon, dissenting papers have begun to appear in the scientific literature. For example, Van Valen's list of objections to the hypothesis of asteroid impact at the Cretaceous-Tertiary boundary was reproduced in the last issue of Science Frontiers. Now, in a recent issue of New Scientist, T. Hallam raises still more objections: Tropical plants, mammals, crocodiles, birds, and benthic invertebrates were little affected by whatever happened at the Cretaceous-Tertiary interface. Furthermore, many groups that were extinguished were already well into a decline. Some geologists insist that some of the supposedly synchronous extinctions were probably separated by several hundred thousand years; viz., plankton and dinosaurs. The vaunted iridium anomaly in deep-sea cores is spread through a considerable thickness of sediment. Even after allowing for the mixing of sediments, the iridium-rich layer is thousands of years thick. According to the asteroid scenario, the clay layer separating the Cretaceous from the Tertiary should represent the fallout from impact-raised dust, which would include asteroidal material and a mixed sample of earth rocks. However, in Denmark, the boundary is marked by the so-called Fish Clay, which is almost pure smectite -- a single mineral and not a mixture of terrestrial rock flour. If it wasn't an asteroid impact, why the iridium concentration? At least three hypotheses have been proposed to circumvent the asteroid debacle: (1 ) volcanic activity; ( ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf037/sf037p10.htm
... rocks that were deposited in the facies that also preserves sulfide minerals and that represent environments analogous to those that preserve fecal pellets today. Rocks containing pellets and algal microfossils range in age from 0.53 to 1.9 gigayears (Gyr) and include Burgess Shale, Greyson and Newland Formations, Rove Formation, and Gunflint Iron-Formation. Similar rock types of Archaean age, ranging from 2.68 to 3.8 Gyr, were barren of pellets. If the Proterozoic microfossils are fossilized fecal pellets, they provide evidence of metazoan life and a complex food chain at 1.9 Gyr ago. This occurrence predates macroscopic metazoan body fossils in the Ediacaran System at 0.67 Gyr, animal trace fossils from 0.9 to 1.3 Gyr, and fossils of unicellular eukaryotic plankton at 1.4 Gyr." (Robbins, Eleanora Iberall, et al; "Pellet Microfossils, Possible Evidence for Metazoan Life in Early Proterozoic Time," National Academy of Sciences, Proceedings, 82:5809, 1985.) The senior author of the above paper also submitted a unique interpretation of the data by J.C . Stager. Stager begins by noting that the paper of Robbins et al has been criticized because the earliest known fossils of metazoans date back to only about 1 Gyr and, therefore, the supposed pellets were obviously something else. Sager next makes a giant conceptual leap: Quite clearly the data prove that feces evolved before animals did!! He goes on: "In standard systematic reasoning, one assumes that the most widespread characteristic represents the primitive state ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf046/sf046p14.htm
... Science Frontiers ONLINE No. 66: Nov-Dec 1989 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Care for a cup of viruses?" The concentration of bacteriophages in natural unpolluted waters is in general believed to be low, and they have therefore been considered ecologically unimportant. Using a new method for quantitative enumeration, we have found up to 2.5 x 108 virus particles per millilitre in natural waters. These concentrations indicate that virus infection may be an important factor in the ecological control of planktonic microorganisms, and that viruses might mediate genetic exchange among bacteria in natural aquatic environments." (Bergh, Oivind, et al; "High Abundance of Viruses Found in Aquatic Environments," Nature, 340:467, 1989.) A sip of water could therefore introduce a billion virus particles into your stomach! This level of virus density in natural water is about 10 million times that formerly estimated. Besides reducing your thirst, what are the implications of this discovery? First, it suggests that bacteria in natural waters are probably kept in check by viruses as well as protozoans. So far, this sounds good. Second, since viruses can ferry genetic material between organisms via transduction (i .e ., host DNA is carried to the next host). This means that genes for antibody resistance and increased bacterial virulence (as present in sewage) may be spread quickly and widely. Also, "engineered bacteria" proposed for use in agriculture, viz., the ice-minus bacterium created to protect strawberries, ...
Terms matched: 1 - Score: 13 - 15 May 2017 - URL: /sf066/sf066b10.htm
