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THE KT BOUNDRY AND THE EXTINCTION OF THE DINOSAURS

    The KT boundary the division between the cretaceous and Tertiary periods and also the boundary between the Mesozoic and Cenozoic is a major division in the history of life and of earth’s history. During this brief but important time the Dinosaurs and many other kinds of life became extinct. Seventy five percent of species became extinct ninety percent of plankton disappeared. Thirteen percent of fish became extinct. Pterosaurs, ichthyosaurs and plesiosaurs disappeared. Marsupial mammals, coiled ammonites and certain types of mollusks disappeared from the scene.

     All kinds of theories have been put forward as to why the extinction took place. They range from disease to geographic and climate change and from volcanoes to comets, asteroids and meteorites. Sixty five million years ago at the time of the great extinction the oceans levels fell drastically and the temperatures which were warm for most of the Cretaceous fell drastically as well. An article that I read the other day seemed to explain the fall in ocean levels. To paraphrase ,it said the oceans started to deepen starting about sixty five million years ago and that this is mostly due to the ocean trenches getting deeper.  This could explain the disappearance of the ancient sea that spread east from central Utah into Colorado and Kansas during late cretaceous times and others seas around the globe that existed at the  time. During the time of the cretaceous no polar ice caps formed.

     In 1980 Luis Alverez along with his son Walter found a clay layer that was deposited very near the KT boundary in Italy containing very high concentrations of iridium an element very common in asteroids, meteorites and comets and may or may not have come from volcanoes as well. More research was done and many more sites were found around the earth containing the same element iridium along with a burnt layer of ash and shock quartz an item only found around huge explosive forces such as atomic bomb drop sites or large meteorite impacts sites. For more information see T-REX AND THE CRATER OF DOOM (a book by Walter alverez). The search was on to find the impact crater some where that could explain the event the father Luis and son Walter had found.  Finally in the nineteen nineties a crater was found that might explain the iridium layer. The crater was found on the north side of the Mexican Yucatan peninsula partly in the ocean and partly on land. It was 180 mile diameter crater buried by younger deposits it has been given the name chicxulub for a town that is near by. It is estimated the meteor was six miles across and produced an explosion equal to 100 trillion tons of TNT. It is thought that global fire storms were ignited around the globe as hot rocks and debris rained down all around the earth and that large tsunamis were rushing out in every direction after the initial blast and shock wave.

     The only formation that was being deposited in Utah at this critical time was the North horn formation of central and eastern Utah with dinosaur remains in the lower part and only mammal remains in the upper part. No definite place marking the KT boundary has been found in Utah. But in Colorado, Wyoming, Montana and South Dakota some sites have been found. Much research still needs to be done concerning the impact theory and the KT boundary its self.