* Astronomy

Scientists have found rare fossils that are shedding new light on what wiped out the dinosaurs at the end of the Cretaceous period 65 million years ago.
For more than a decade, the standard view has envisioned a speeding object from space that crashed into the earth and kicked up enough dust and rock around the globe to blot out the sun. The smoking gun seemed to be the discovery beneath the Yucatán peninsula of Mexico of a 110-mile-wide crater called Chicxulub, after a nearby town.

But lately, doubters have argued that Chicxulub formed 300,000 years before the mass extinction - too early to have played a role in the demise of the dinosaurs and hundreds of other plant and animal species that vanished at the end of the Cretaceous.
The team of scientists zeroed in on Cuba as an ideal place to seek clues, having heard from Cuban colleagues of a possible trove of fossils of the right age. The Cuban zone was 600 miles from the Mexican crater.
Now, in the September issue of Geology, the scientists, from Spain, Cuba and Mexico, report that they have discovered a highly disturbed bed of fossils that bears numerous signatures of Chicxulub's mayhem. The date of the disturbance, 65 million years ago, is exactly at the end of the Cretaceous.


Courtesy of Dr. Laia Alegret

"The site is located opposite a military base. So it's almost impossible to get a work permit" - Laia Alegret, a team geologist at the University of Zaragoza in Spain.

The discovery was outside Santa Clara, a city in central Cuba whose nearby air base drew scrutiny in 1962 when American spy planes spotted Soviet jets and antiaircraft missiles.

"It was definitely a hot spot" - Timothy Naftali, a cold war historian at the University of Virginia.

Starting around 2000, Dr. Alegret and her European colleagues repeatedly sought work permits for a nearby hill but always met with stultifying delays, if not outright rejections. Finally, they slipped into the site with their Cuban colleagues, going in late 2000, 2002 and 2003. At other times, the Cubans went in alone.
A rocky outcrop on the hill showed an exposed bed of sedimentary rock made up of broken bits of minerals and fossils. It was more than 30 feet thick. The team took 66 samples. Examination with microscopes showed quartz deformed by high temperatures and pressures, as well as tiny spheres of glass, both clearly debris from a spectacular fireball.

Microscopic study also revealed the presence of thousands of tiny fossil creatures, most especially foraminifera. Those one-celled animals have a bewildering array of minuscule shells. Forams, as they are known, evolve so fast that geologists, palaeontologists and oil companies use their shifting appearance as reliable guides to geologic dating.

"They told the age of the sediments. So we've definitely confirmed the age of these deposits" - Laia Alegret.

At the end of the Cretaceous, the rocky bed now in Cuba formed on the ocean bottom at a depth of perhaps 3,300 feet, over a few days or weeks as tons of debris rained down from the sky and huge waves generated by the Chicxulub event washed land out to sea.

"It was geologically instantaneous" - Dr. Laia Alegret.

Earth movements over the ages turned that part of the seabed into land.
Dr. Alegret's co-authors include Ignacio Arenillas, José A. Arz, Alfonso Meléndez, Eustoquio Molina and Ana R. Soria of the University of Zaragoza; Consuelo Díaz of the Institute of Geology and Paleontology in Havana; José M. Grajales-Nishimura of the Mexican Institute of Petroleum in Mexico City; and Reinaldo Rojas of the National Museum of Natural History in Havana.
Dr. Alegret said that because of the site's importance, her Cuban colleagues were talking with the government to have it protected from rain and erosion. The aim is to save the outcrop for scientific study.

Adapted from source

The catastrophe that wiped out the dinosaurs and many other species 65 million years ago has been clarified.
The meteorite that caused their deaths left its largest evidence in Cuba.



Today it seems to be definitely accepted, said Dr. Manuel Iturralde to Sol y Son. Dr. Iturralde, a specialist with Cuba`s National Museum of Natural History, explained that the massive extinction 65 millions years ago in which dinosaurs disappeared was caused by the meteorite of Chixculub, Mexico.
The hypothesis of the `killer meteorite` emerged in 1979 when physicists Harold Urey and Luis `lvarez found abnormal concentrations of iridium in sediments from the late Cretaceous period Iridium is rare on Earth, but there is plenty of it in asteroids and it is thought that the impact of one with a diameter of over six miles induced earthquakes, volcanic eruptions and a `nuclear winter` with a sudden drop in temperature.

Such an impact would make a crater with a 240 km diameter. Since none like that was found on land, they looked for it at sea.
In 1990, Bohor and Seitz, two US geophysicists, discovered that 650 thousand centuries ago a giant meteorite fell in Chixculub, in the Yucatan peninsula, Mexico, near the south-western coast of Cuba.
The evidence should be in the geological strata of the late Cretaceous or early Tertiary periods, (K-T layer, according to experts), for its lower part contains fossils of the disappeared animals, which were not present in the upper part.
Also there should be quartz particles crushed by the impact, as well as microtectites, or crystal balls formed when the molten rock solidifies, usually found around meteor craters. And, of course, iridium.

Cuban Evidence

Iturralde`s attention was caught by a paper published in Nature magazine. "I went to the Cuban areas where allegedly were fragments of the impact, but the rocks there were not originated by a meteor. Two years later I published a paper on the subject in Earth and Planetary Science and Letters."
In 1996 Dr. Takafumi Matsui, from the University of Tokyo, visited Cuba with a project on the Tertiary geological limit and signed a collaboration agreement with the Museum of Natural History and the Institute of Geology and Paleontology.
During the past five years several expeditions studied the K-T layer in the provinces of Pinar del Ruo, Havana, Matanzas and Villa Clara.

Unique cuts were found, for if the deposits in Mexico and other countries of the area are 6 to 10 feet deep, in Cuba they go down to almost three thousand.

"They are unique, and indicate the most complete vestiges of the impact and its consequences." - Dr. Manuel Iturralde

What produced such unusual thickness? When the meteorite fell in Yucatan, what was then the bottom of the Caribbean and the edge of the peninsula is now what is found in Pinar del Ruo, Havana and Matanzas.
That is, Cuba has rocks that were part of the bottom of the Caribbean Sea and the Yucatan shores.

An Extraterrestrial Earthquake

According to Iturralde the impact generated a shock wave with an earthquake way beyond any of terrestrial origin, so great that it provoked an enormous crumbling of the continental edge in Yucatan, the Bahamas platform and the then existing islands, which at present are the foundation of Cuba. The crumbling made deposits hundreds of feet thick, gaps with enormous blocks torn from the near emerging areas.

"Gigantic tsunamis crashed on the Caribbean coasts rolling over small islands and low areas, with billions of tons of dust and sand. When they settled, that material when to the bottom of the sea and created the huge layers that we have found" Dr. Manuel Iturralde.

The impact pulverized the meteorite, rocks were fused and flew to the atmosphere, which received that iridium-rich dust, crystals generated by the fusion and cooling of the rock, and also laminar quartz. Due to the impact, all that is on Cuban rocks

Prehistoric Nuclear Winter

"Most probably all sea organisms in the Caribbean did not survive. Not only dinosaurs were extinguished" - Dr. Manuel Iturralde.
At the International Congress of Geology held in Havana, Dr. Ryuji Tada, a researcher from the University of Tokyo, said that science links the impact with a world environment crisis - acid rains, fragments falling from the sky and cooling for a long period, because the particles in the atmosphere blocked solar radiation, a kind of `prehistoric nuclear winter.`

This brought massive deaths that in turn generated plagues, bacteria, fungi and diseases for wildlife and flora, which in turn contributed to the death of more species. The destruction of plants and forests left them without food, the massive fallout and acid rains generated chemical changes in the composition of the water in the seas, rivers and lakes.

Many species survived, but also many were totally extinguished, like dinosaurs. At present there is a second project with universities from Spain and Mexico, led by Reinaldo Rojas, the Museum`s director, which will study marine life before and after the impact, something that was not done during the previous research.

"People sometimes wonder. why so much money is spent on studying the past when there are so many problems today, but those studies allow us to better know the whys of the present and prepares us for the future. What happened in the past on Earth could happen again, and all that history is in the rocks, so if we study them we`ll know what happened, what could happen and how to find ways to be prepared for tomorrow." - Dr. Manuel Iturralde.

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