Objectives:
 

(1) Mass extinctions on Earth

(2) Asteroid Impact and the K-T Event

(3) Dr. Elliott's work at Stevns Klint

The Earth has suffered a series of mass extinction events recorded in the geological record. These probably had both TERRESTRIAL (climate change, flooding, volcanic activity, disease, loss of biological diversity) and EXTRATERRESTRIAL (asteroid impacts) causes.

The most recent event occurred 65 million years ago at the boundary of the Cretacious - Tertiary ages (K-T) in which 11 percent of all species were lost (including the demise of the dinosaurs).

The evidence now points to an impact of a 10 km size body near the Yucatan peninsula in Mexico (crater now covered by 2 - 3 km of sediments). The impact destroyed the asteroid and sent a cloud of debris into the stratosphere (which settled all around the globe).

• shocked quartz found near the site
• worldwide deposition of high levels (10 - 80 ppb) of Iridium (found in meteorites but only in trace amounts, 0.06 ppb, in crustal rock)
• ratios of Platinum Group Elements (platinum, iridium, gold) in K-T boundary are similar to those in chondritic meteorites
• exotic mineralogies (including microscopic fragments of the meteorite)

Dr. Elliott investigated the clay deposits found in exposed K-T boundary rocks (debris from the impact) at Stevns Klint in Denmark.

He studied the smectite clay and found evidence of meteoritic proportions of iridium and gold. High magnification images of the samples show evidence of glasses formed in the impact which slowly tranform into smectite.

He also found evidence of small dark patches of iron oxides with meteoric proportions of metals. These are probably remnant fragments of the actual asteroid that collided with Earth.