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| UPDATE: 2 February 2005 | The impact of a large extraterrestrial object on the Yucatan platform 65 million years ago created one or more large tsunami, or huge wave... This water, rushing back into the Gulf, would have possessed tremendous erosive capacity and the ability to carry sediment and fossils from the coast into deep water. Geologists working in north-eastern Mexico recently discovered evidence for this southward backrush of water in the deposits of ancient valleys scoured into the continental shelf. The valley-fill deposits, laid down at the end of the Cretaceous period, contain abundant grains of formerly molten rock (ejecta) thrown from the Chixculub impact crater. These grains evidently arrived in north-eastern Mexico before the tsunami, and the backwash of Gulf-bound water eroded them from coastal regions and concentrated them in the valleys as flow velocity slowed adjacent to the temporarily lowered sea level of the Gulf. Also present in the valley-fill deposits are fossils eroded from coastal settings; these organisms provide firm evidence for the source of the flow. Although the duration of the backflow is unknown, it is likely to have continued for hours or days after the initial impact. These deposits therefore provide evidence for an enormous sediment-recycling system set up by the run-up of tsunami waves onto coastal North America shortly after the Yucatan impact. This discovery confirms the grand scale of sediment and fossil recycling at the end of the Cretaceous and helps to explain why the latest Cretaceous fossils are commonly found above the impact rocks in the Gulf of Mexico region. | |
| Startling new evidence |
from boreholes drilled into the 120-mile-wide Chicxulub crater in Mexico indicate that the great impact there happened 300,000 years too early to have been the one that wiped out the dinosaurs. The discovery comes at a time when some geologists are convinced that the Chicxulub event killed 70 percent of living species at the Cretaceous-Tertiary (K-T) boundary, 65 million years ago. Several lines of geological evidence from Chicxulub make a compelling case for the crater having been formed too early to be the mass killer. Evidence, broken `breccia` rocks, from a borehole, Yaxcopoil 1, was expected to provide final, irrefutable confirmation of Chicxulub's role in the K-T boundary mass extinction. It didn't. On top of the impact breccia is about two feet of gently-laid-down, thinly layered seafloor mud built up over 300,000 years, Keller said. Those two feet of post-impact mud have the fossils, carbon isotopes and magnetic signal of the late Cretaceous, before the mass die-off. It's 300,000 years too early . Also missing from the Yaxcopoil 1 borehole rocks is any significant iridium signal , the extraterrestrial element that first clued scientists into the fact that an asteroid might have caused the K-T extinctions. As to what really caused the K-T mass extinction; it was probably another asteroid impact combined with intense volcanic activity., and, many dinosaur researchers suspect that dinosaurs were on the decline before the final mass extinction. (new evidence contradicts that theory - Nov 19th) Chicxulub might have played a role in their extinction. but a second impact, still undiscovered, might have been the terminal blow. | |
 The humble tropical honeybee |
may challenge the idea that a post-asteroid impact "nuclear winter" was a big player in the decimation of dinosaurs 65 million years ago. Somehow the tropical honeybee, Cretotrigona prisca, survived the end-Cretaceous extinction event, despite what many researchers believe was a years-long period of darkness and frigid temperatures caused by sunlight-blocking dust and smoke from the asteroid impact at Chicxulub. The survival of C. prisca is problematic and telling, asserts palaeontology graduate student Jacqueline M. Kozisek of the University of New Orleans. Late Cretaceous tropical honeybees preserved in amber are almost identical to their modern relatives. If no modern tropical honeybee could have survived years in the dark and cold without the flowering plants they lived off of, something must be amiss with the nuclear winter theory. "It couldn't have been that huge," says Kozisek of the Chicxulub-related temperature drops asserted by other researchers. Kozisek will present her work on Monday, 8 Nov. 2004 at the Geological Society of America annual meeting in Denver. Modern tropical honeybees have an optimal temperature range of 88 to 93 degrees F (31-34 °C) in order to maintain vital metabolic activities, according to entomological research. That's also the range that's best for their food source: nectar-rich flowering plants. Based on what is known about the Cretaceous climate and modern tropical honeybees, Kozisek estimates that any post-impact winter event could not have dropped temperatures more than 4 to 13 degrees F (2-7 °C) without wiping out the bees. Current nuclear winter theories from the Chicxulub impact estimate drops of 13 to 22 degrees F (7-12 °C) - too cold for tropical honeybees. "I'm not trying to say an asteroid impact didn't happen. I'm just trying to narrow down the effects." To do this, Kozisek took a novel approach for a palaeontologist - instead of looking at what died out, she dug through the literature to find out what survived the massive extinction event. "I made a list of all survivors and picked those with strict survival requirements." . She determined that those survival requirements were by calling on studies of the closest modern analogues - which wasn't always easy for some species, she pointed out. There was, for instance, a very early primate that crawled out of the Cretaceous alive, but there is really no comparable small primate around today with which to reliably compare. On the other hand, a good number of tropical honeybees haven't changed a lot in 65 million years and a great deal is known about modern tropical honey bees' tolerances to heat and cold. What's more, amber-preserved specimens of the oldest tropical honey bee, Cretotrigona prisca, are almost indistinguishable from - and are probably the ancestors of some modern tropical honeybees like Dactylurina, according to other studies cited by Kozisek.  to read more | |
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The theory that a single, massive asteroid strike killed off the dinosaurs 65 million years ago may itself become extinct... New data suggests the Chicxulub crater in Mexico, created by the collision, predates the extinction of the dinosaurs by about 300,000 years. Data was derived from analysed rock-core, using five separate indicators of age, including fossil planktonic organisms and patterns of reversals in the Earth's magnetic field. The cooling of the global climate shortly followed by a period of greenhouse warming placed enormous stress on the dinosaurs. This warming could have been kicked off by carbon dioxide released by a massive eruption of lava from the Deccan traps in India. The Chicxulub impact occurred during this warming period and, although the environmental effects were severe, it did not cause the extinction of the dinosaurs. Perhaps, a second impact (beneath the Indian Ocean?), 300,000 years after the Chicxulub collision, may have finished off the creatures... | |
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| A theory that the Chicxulub | impact 65 million years ago may have created the conditions that led to coal formation in the Williston Basin, the largest known deposit of lignite in the world. "We think the coal formation could be related to the Cannonball Sea. As sea levels rose, it may have raised groundwater levels and created swamps." The Cannonball Sea formed about 2 million years before the impact and was a younger, smaller version of the shallow Western Interior Seaway. At its peak 90 million years ago, the seaway covered much of North America. Throughout the Williston Basin, the boundary between the pre-impact Hell Creek and post-impact Fort Union rock formations is immediately apparent, as darker floodplain deposits are replaced by distinctive layers of lighter-coloured sediments. to read more
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| A new study, | provides strong indications that the Permian-extinction event did not come from an extraterrestrial impact, but from Earth itself. An international team of scientists led by Christian Koeberl from the University of Vienna studied rock samples taken from deep in the Carnic Alps of southern Austria and the western Dolomites in northeast Italy. "Our geochemical analyses of these two famous end-Permian sections in Austria and Italy reveal no tangible evidence of extraterrestrial impact. This suggests the mass extinction must have been home-grown." to read more
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| A novel way | A novel way has been developed, to determine land elevation throughout
geological ages. Knowing how high mountains and plateaus were in the
past can help scientists to study how our climate system evolved. "Understanding the past elevation of land surfaces, also known as paleoelevation, has been one of geology's Holy Grails. This is the first paleobotanical method that works globally and is independent of long-term climate change. The new method will help us to understand the rate at which some of the Earth's most important mountains have uplifted. It will also show how the process of mountain building influenced climatic patterns as well as plant and animal evolution." The new method of paleoelevation involves counting the stomata on leaves of plants going back as far as 65 million years ago. Stomata are minute openings on the surface of leaves through which plants absorb gases, including carbon dioxide, which plants need for photosynthesis. If you climb to higher elevations, carbon dioxide is less concentrated. Therefore, the higher the elevation, the more stomata per square inch of leaf surface a plant would need to survive. By simply counting the number of fossil stomata, Dr. McElwain, a Field Museum scientist, estimated how much carbon dioxide was in the air when the fossil leaf developed. From that, she estimated the elevation at which the fossil plant once lived. She used historical and modern collections of Quercus kelloggii (California Black Oak) leaves for her study, because the tree grows within an unusually wide range of elevations from 60 to 2,440 meters. The historical leaves were collected by botanists in the 1930s and stored within herbarium collections of the Field Museum and the University of California, Berkeley. This new method of estimating land elevation has an average error of about 300 meters– but as low as 100 meters. Such an error rate is much lower than the error rate of existing paleoelevation methods, all of which have significant limitations. This method can be used for any area where suitable plant specimens can be found. High mountains and plateaus can act as important barriers to plant and animal migration and dispersal resulting in isolation of plant and animal populations on opposite sides of mountain chains. Therefore, knowing exactly when in the geological past the mountains of today's world reached their current elevations is relevant to our understanding of plant and animal evolution since isolation is an important mechanism in the formation of species. In addition, high mountains and large plateaus (such as those in Tibet and Colorado today) have always had a big influence on climate by altering patterns of atmospheric circulation. | |
| When dinosaurs became extinct, |
there were more varieties of the reptiles living than ever before, according to a new analysis of global fossil records by a team of researchers from the University of Rhode Island. “Our analysis finally lays to rest the old, utterly unsupported idea that dinosaurs were declining in diversity during the last 10 million years of their time on Earth” Only 40 known genera of dinosaurs comprised the fauna of the late Triassic period, with diversity increasing until the Cretaceous period - 99 to 65 million years ago - when at least 245 dinosaur genera were to be found. "Dinosaur diversity was increasing logarithmically throughout their 160 million years on Earth," "Their increasing diversity seems to have been fuelled by the evolution of new innovations that allowed them to explore new habitat." According to palaeontologists, early dinosaurs tended to be unspecialised, but during the late Cretaceous period they became much more specialized in their feeding and behaviour patterns, driving their evolution into more diversification. The diversity of plant-eating dinosaurs in the Cretaceous was found to be especially high. Earlier studies, based almost entirely on North American dinosaur records, suggested a drop in dinosaur diversity in the 10 million years leading up to their extinction. However, analysis of a new database of global dinosaur records, that now includes new fossils unearthed in Asia and South America, shows that the diversity of dinosaur genera did not decrease . | |
| About 37,000 years ago, | the genetic diversity of bison living in what's now Alaska, Canada and Siberia decreased significantly, according to a review of DNA from bison fossils. Archaeological evidence (which may be wrong) shows humans did not inhabit those regions until more than 15,000 years later. So Indian hunters did not drive the buffalo to virtual extinction- it was climate change. This study also hints at the cause of the demise of the mammoths and other megafauna of America's Great Plains. to read more
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| An international team (old news) | of scientists has discovered the largest impact crater field ever found on Earth, uncovering the first evidence that the planet suffered from simultaneous meteor impacts in the recent past. Using orbital imaging radar, Philippe Paillou of Bordeaux University Observatory in Floirac, France and colleagues identified a large number of circular structures still partially buried beneath the sands of the southwestern Egyptian desert. Roundup of Ancient impact news and current research from October -November. to read more
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| November 19th: | An Open University research student will reveal her findings on what
caused one of the world's 'Big Five' mass extinctions at the Geological
Society of America's annual meeting in Denver, USA, this month. PhD student Charlotte Pearce will input into the debate as to whether a meteorite impact or volcanic eruption caused the Cretaceous Tertiary Boundary (KTB) mass extinction 65-million-years-ago. Between 50 and 60 per cent of marine and terrestrial life forms became extinct during the KTB extinction, including the dinosaurs. The cause of this mass extinction has received much attention from scientists over the last 25 years, since the detection of iridium-rich cosmic debris at the boundary layer around the world -- an element known to be rare on earth. This led to the theory that a meteorite impact could have been responsible for the debris and the mass extinction; the 180-km wide Chicxulub impact crater was eventually discovered in the Gulf of Mexico. However, on the other side of the world, massive volcanic eruptions, known as the Deccan Traps continental flood basalt province, were simultaneously reaching their peak, forming a 2.5km thick pile of lava. "Both the Chicxulub impact and the Deccan eruptions would have had the potential to induce detrimental environmental changes serious enough to significantly affect terrestrial ecosystems. Dust-induced darkness, acid rain, wild fires and global warming would all have played a role in inducing biospheric trauma, but the timescales over which these were effective would be expected to be different, dependent on the event that caused them.” Charlotte used chemical and isotopic fingerprinting techniques on molecular fossils from North America, and more recently from New Zealand, to investigate patterns which would establish whether there was instantaneous change (as the result of a meteorite impact) or gradual change within the ecosystem (as caused by prolonged volcanism). "Carbon isotopes can tell us a lot about the stability of an ecosystem and, together with the identification of molecular fossils, enables past variations in habitat, climate and biology to be investigated." The aim of the project is to compare and contrast samples from several terrestrial and marine KTB successions, at varying palaeogeographical distances from the locations associated with the two putative causes of end-Cretaceous environmental stress. In effect the project examines the effects of these two environmental disasters working outwards from the 'ground zero' locations. Results taken from samples in the Western Interior of North America show that the ecosystem experienced a short sharp shock at the boundary consistent with a meteorite impact. Early analysis of the New Zealand samples also point to a meteorite impact. | |
| Iron-60,
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found deep beneath the Pacific Ocean has the German scientists to speculate that a supernova explosion 3 million years ago might possibly have helped bring about human evolution. Gunther Korschinek and colleagues at the Technical University of Munich in Germany found debris from an exploding supernova that could have changed the climate on Earth around the time that humanity's ancestors first began to walk. to read more
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 Ancient impacts: |
Roundup of Ancient impact news and current research from October -November. to read more
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