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Iridium Chalk


Iridium Chalk

Classic Locality

Description Tabs

Stevns Klint, Zealand, Capital Region, Denmark
Size Range: 
Thumbnail (1-3cm)
2 × 1.2 × 1.2 cm

Iridium rich layer at the Cretaceous/Paleogene boundary - Chalk Cliffs - Stevens Klint - Denmark

Glass Bottle Size : 20 x 12 mm - Clay : 1.20 gr  - Total  Weight with bottle : 2.50 grams

(courtesy of Wikipedia)

Stevns Klint is a white chalk cliff located some 6 km (3.7 mi) southeast of Store Heddinge on the Danish island of Zealand. Stretching 17 km (11 mi) along the coast, it is of geological importance as one of the best exposed Cretaceous-Tertiary (K/T) boundaries in the world. Subject to frequent erosion, the cliff rises to a height of up to 40 m (130 ft). The cliffs are a UNESCO site.

The cliff reveals sections from the uppermost part of the Maastrichtian stage (72 to 66 million years ago) and from the lowermost part of the Danian stage (66 to 62 million years ago). The dark layer of Fiskeler, mainly five to ten centimeters thick, clearly marks the Cretaceous-Paleogene boundary. The Fiskeler is enriched in iridium, a fact used as an argument for the Alvarez hypothesis that the worldwide Cretaceous–Paleogene mass extinction was caused by the impact of an asteroid. The layers can also be seen deep in the tunnels of Stevnsfortet, a cold-war fortress constructed in 1953. The bryozoa chalk in the cliff is highly shock resistant to both conventional and nuclear weapons

AS IMCA member 8039 I gaurantee the authenticity of the specimen, a sample of what I collected has been sent to the university in Aachen to determine the exact  percentage on iridium in the sedimentary  clay 

In 1980, a team of researchers led by Nobel prize-winning physicist Luis Alvarez, his son, geologist Walter Alvarez, and chemists Frank Asaro and Helen Vaughn Michel discovered that sedimentary layers found all over the world at the Cretaceous–Paleogene boundary(K–Pg boundary; formerly called Cretaceous–Tertiary (K–T) boundary) contain a concentration of iridium hundreds of times greater than normal. Iridium is extremely rare in the Earth's crust because it is very dense and has the affinity for iron that characterizes the siderophile elements (see Goldschmidt classification), and therefore most of it sank into the Earth's core while the earth was still molten. The Alvarez team suggested that an asteroid struck the earth at the time of the Cretaceous–Paleogene boundary.

In a 1953 publication, geologists Allan O. Kelly and Frank Dachille analyzed geological evidence from around the earth and concluded that one or more giant asteroids impacted the earth, causing an angular shift in the earth's axis, global floods, fire, atmospheric occlusion and causing extinction of the dinosaurs. There were other earlier speculations on the possibility of an impact event, but no evidence had been uncovered at that time

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