K-Pg boundary locations are found peppered throughout the world and are considered to be premier geological sites. They bear the signature of a major Earth cataclysm event that happened about 65 million years ago.
The element iridium was pivotal in these discoveries, as it is common in asteroids and comets, but uncommon in Earth rocks. Iridium is a siderophile. This means in the evolution in Earth's early geologic history most of it would come to reside primarily near or in the core. Scientists discovered a spike for this particular element at several geologic sites and it varied in intensity, depending on the location. So, it was not expected to be found on top of the Earth - but only deep underground. This became a geologic mystery.
The scientists who helped eventually put this geologic puzzle together were Walter and Luis Alvarez. Walter Alvarez was initially an oil geologist who traveled in Europe and Africa. He developed an interest in archaeological geology. He spent time in Italy researching Italian volcanoes and their influence on early Roman patterns of settlement. For Walter Alvarez "the spark" for the eventual Chixculub event answer actually began in Gubbio, Italy. Right outside of the town of Gubbio, Italy, lies the geologist's dream. The pink outcrops called the “Scaglia rossa” were once an ancient seabed where the tiny fossilized shelled creatures called foraminifera could be found. In one centimeter of clay, in these outcrops, there were no fossils found at all. In the older layer below the clay the forams were larger and diverse - and above the "no life" centimeter of clay - in the younger layer the forams were smaller and less diverse. The Gubbio formation was geologically dated and was found to span parts of both the Cretaceous and Tertiary periods. This is how this material came to be referred to as K-T boundary, and paleomagnetic with geomagnetic reversals and foraminifera (as index fossils) became the new tools that Walter and Luis needed to sort out the ongoing evolving complexities of the mystery.
After linking K-T boundary to Gubbio, with the help of the element iridium in the mix, Walter and his father Luis Alvarez went looking for similarly exposed sites like this. They visited Stevns Klint fishclay layer, in Denmark. The cliff face was mainly white chalk and full of all kinds of fossils. The thin K-T clay bed, however, was black, stunk of sulfur, and contained only fish bones. Walter deduced that during the time this “fish clay” was deposited, the sea was an oxygen-starved graveyard (see "Dr. Strangelove" ocean material). The Danish fish clay iridium levels were 160 times background levels.
This research all ties together into a neat bow when other geologists discovered the Chixculub impact site, through deep ocean drilling. Drill cores revealed a huge disturbance in the geological layers in the Yucatan region. It is thought that an asteroid big enough to scatter the estimated amount of iridium discerned in the worldwide spike at the K-Pg (previously K-T) boundary locations had to have probably been about 6 miles across. The Chixculub asteroid impact event has now been definitively linked to the demise of the "Age of the Dinosaurs" and a mass extinction in which 75% of plant and animal species went extinct. With the help of using other impact materials such as planar deformation features (pdf's), tektites, shocked minerals, and other features - scientists are now well-equipped to determine more geological aspects of Earth's cataclysmic history.
This specimen was collected at the K-Pg boundary at Iridium Hill, Montana.
Size: 38mm L X 25mm W X 15mm D, Weight: 14 grams.
Ships with tag, Certificate of Authenticity and a detailed information sheet about K-Pg boundary.
Obtained in a materials trade with a geological institution.
This material is moderately friable, but is stable. No repairs.
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