Wednesday, July 2, 2008

History Of The Frick, Switzerland Site


In the town of Frick, which is situated in the Jura Mountains of northwestern Switzerland, a clay pit has been exploited for the production of brick since the early 1900s. The sediments the factory exploits are from the Late Triassic and Early Jurassic, and span about 27 million years, from 217-190 million years (get stratigraphic timetable here). In 1961, the factory lab chief found what later turned out to be the first dinosaur bones.


> Zoomable satellite map of the Frick clay pit. View Larger Map

The bones were from strata deposited in the Norian Stage of the Late Triassic, about 205 to 210 million years ago. More bones turned up in the following years and in 1976 and 1977, first excavations began. It became obvious that the excavated dinosaur bones belonged to Plateosaurus engelhardti, a prosauropod of about 6-10 metres (18-30 feet).

> Plateosaurs. Copyright painting by Raúl Martín.

In 1979 and 1984/1985, more excavations were organized. The latter excavation yielded an almost complete skeleton which is now on display in it's finding position in the Frick Dinosaur Museum (website in German only).

> Almost complete Plateosaur specimen unearthed in 1985 on display in the Frick Dinosaur Museum. See more photos from the Frick Dinosaur Museum in this post.

Further excavations took place in 1988, 1995, 2006 and 2007. The different successive excavations yielded about a dozen more or less (in)complete plateosaur skeletons, as well as a number of theropod theeth.

> Foto from the 2007 dig. See more photos from this dig here.

The 2006 dig for the first time revealed a theropod find which is currently studied at the University of Zurich (read more about the 2006 theropod find here). The skeleton is a small, yet to be determined coelophysoid (Coelophysis, Liliensternus,...?).

> The 2006 coelophysoid theropod remains. Copyright photo: Dr. Ben Pabst.

Associated finds include small scattered remains such as lung fish teeth, crocodile dermal denticles, as well as remians from fish and even freshwater sharks. The sedimentologic and taphonomic study revealed that the region was once a broad, arid coastal mud flat which was episodically affected by mud flows from flash floods in nearby wadis (see late triassic paleogeography in this post). The excavated Plateosaurs most certainly got stuck in mud traps.

> Plateosaurs stuck in a mud trap. Copyright painting by Raúl Martín.

This is evidenced by the fact that most Plateosaur finds are embedded in the same position; lying on their belly, with their spread out hind legs below the body. Also, many finds only consist of the lower half of the body. Aparently, small predators were eating away the upper body of many of the trapped Plateosaurs. Accordingly, many shattered bones from the upper bodies as well as predator theet have been found all around.

> Note the height differences in the 1985 specimen's body parts, pointing to a deposition in a mud trap.

Considered all the finds, Frick is one of the most important Plateosaur finding sites in the world and (unlike the German Trossingen) the only major European site that currently delivers fossils.

> Section of the Frick clay pit by Dr. H. Furrer. Measurments are in metres, time is indicated in million years.

Other interesting findings include the fact that the bones have been preserved in the form of the iron phosphate mineral vivianite. Vivianite has also been found in many archeologic sites where bodies have been deposited in dysoxic conditions and it is known to form within few years. The preservation of the bones is indeed exceptional and even microscopic bone structures have been preserved. The bones have also been found to be enriched in rare earth elements.

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