While the causes of some of the earlier extinction events have been identified and explained, the most recent one; the Pleistocene, has remained a controversial event without a clear cut answer. That is no longer the case, as there is a clear answer supported by the evidence that reveals exactly what happened to wipe out so many animal species over the entire globe. While a gradual extinction taking place over thousands of years has been the favored theory since it is a better fit for the current two popular extinction theories; climate change and/or over hunting, the evidence is actually more supportive of a sudden extinction event that occurred Earth wide at the same time.
"The extinction chronology of North American Pleistocene mammals therefore can be characterized as a synchronous event that took place 12,000-10,000 radiocarbon years B.P. Results favor an extinction mechanism that is capable of wiping out up to 35 genera across a continent in a geologic instant."
What occurred in North American, would logically have occurred Earth wide, since the Pleistocene was a global event and was not limited to North America.
A sudden global extinction event is of course in complete conflict with both the Climate change theory and the Over Hunting theory, neither of these theories can account for such an event. The timing of this sudden extinction has also always been linked to the end of the Pleistocene and the beginning of the Holocene since it is the extinction event itself that is the dividing marker that separates the two periods of geological time and marks the end of the last Ice Age. The lost of the Ice Age ice sheets is tied to the extinction event, and this connection is not coincidental.
Sudden events require a sudden trigger event that sets them off. Increasing evidence has been mounting in the last few years, that tie a comet impact to the Pleistocene extinction event and the end of the Ice Age. Evidence has come to light that indicates that a comet impact occurred on the Canadian Ice Sheet during the last stage of the Ice Age, the Younger Dryas, which was approximately 1,500 years long. (see link section on original page) Currently it is theorized that the comet impact occurred at the beginning of the Younger Dryas cooling period and caused the down turn in temperature and caused at least some of the extinctions by climate change rather than just by direct impact destructive events. As the evidence is considered, it is clear that the impact event occurred not at the beginning of the Younger Dryas, but at the end of it, which puts the Pleistocene Extinction event squarely where it has always been believed to have occurred. One of the key reasons for this, is the association of Mega or Super floods which occurred at the end of the Younger Dryas as the Ice Age ended, with the expected results of a series of comet impacts on an Ice Sheet. Those huge erosive drainage events are what sets the end of the last Ice age advance apart from other stages of the Ice Age, for those huge releases of water created landforms that were not created by earlier retreats of the Ice Sheets. These huge and unique landforms are seen in the vastly oversized river valleys that drain from areas once covered by the last advance of the Ice Sheets like the Mississippi river valley, and in streamlined land forms which were subjected to sheet flooding and glacial drainage valleys which today remain like isolated canyons with no rivers that flow through them.
What happen is the Ice Sheet impacts caused a very large and sudden release of glacial melt water which flooded out across the surrounding landscape and flowed into the seas. The largest out pouring occurred in the Hudson Bay area where the impact triggered the release of ice that had been backed up and trapped in the bay. This sudden emptying of the bay is seen in ocean floor sediments across the floor of the Atlantic Ocean which contains a layer of small stones dropped from icebergs as they melted and dropped the stones which had been carried in the ice. This huge release of ice from Hudson Bay affected global sea levels and trigged a massive surge event into the empting bay. Combined with the very large releases of glacial melt water from other parts of the Ice Sheet, enough water poured into the oceans to noticeably raise global sea levels. This rise in sea level flooded the edges of Ice sheets and glaciers in other parts of the world, which at the end of the Ice Age, were already prone to surging, to surge en masse in a global event. Like a row of giant dominos, huge sections of the former Ice Sheets surged into the rising seas, creating a run away chain reaction of flooding and surging.
As the seas rose, the water began to back up the rivers causing them to over flow their newly created banks and flood the surrounding land, as shown by glacial drop stones being found on these banks, showing that the rivers backed up while carrying rock bearing glacial ice. Further evidence for this flooding is seen in the discovery of whale bones in the state of Michigan and in other recent marine fossils which are sometimes found far from the sea in places where they could not have reached in any other way. Another proof of the occurrence of the extent of this late glacial flooding event is the presence of marine diatoms found in the upper Midwest. Marine diatoms are used as a marker to identify past marine flooding events, and the evidence shows that the sea water rose high enough to reach the edges of the retreating Ice Sheets, effectively flooding the world for a brief period of time until the Earth's crust shifted and land areas rebounded and the sea floors where depressed back down to their pre-Ice Age positions.
The evidence indicates that the Pleistocene Extinction event was caused by a global impact triggered Ice Age out burst flood event, which is why it was global, sudden and small animals survived more than large animals. This explains why the Clovius culture disappeared, what happened to the Ice Age hunting groups and how they were replaced by the later farmers. The Pleistocene was flushed away and replaced by the Holocene as the water drained and the survivors inherited a largely emptied landscape. It was a restart, and why we see a major break in the geological record at the Pleistocene/Holocene boundary.
More evidence and supporting references are found at; http://www.squidoo.com/solving-the-myster
Sincerely Yours; Wm Scott Anderson