This stuff always fascinates me. What really happened on this earth to create massive extinctions not once but at least 5 different times.
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Originally Posted by Wikipedia
In the past 540 million years there have been five major events when over 50% of animal species died. Mass extinctions seem to be a Phanerozoic phenomenon, with extinction rates low before large complex organisms arose.
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Some of it points to asteroid bombardment. Things like tektites are basically what's being described in this report by the glass ferules.
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Originally Posted by Wikipedia
Tektites (from Greek τεκτός tektos, molten) are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact of large meteorites on Earth's surface. Tektites are typically black or olive-green, and their shape varies from rounded to irregular.
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There is no other known natural method that produces tektites.
The evidence of a deep impactor at Chicxulub crater was discovered while searching for oil through geologic surveys. The fractured crust deep in the earth could only be caused by a meteorite hitting the earth so hard that it went into the earth deeply. Chicxulub is not the only evidence of deep impactors. They are all over the earth, the damage to underground strata still there, long after the surface has weathered over the damage. Deep impactors are caused by large meteorites hitting the earth at steep angles.
Some have been shown in searching for why salt water had intruded into the fresh water aquifer. Some have shown up in other oil surveys. Enough have been found to leave no doubt the complete earth has been hit, often and hard in it's early days.
I will end this with one worrying little tidbit. Today, many scientists think the evidence indicates a sixth mass extinction is under way. The blame for this one, perhaps the fastest in Earth's history, falls firmly on the shoulders of humans. By the year 2100, human activities such as pollution, land clearing, and overfishing may have driven more than half of the world's marine and land species to extinction.