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Archeopteryx lithographica

and

An Open-Cast Coal Mine

A bit of a break here: two unusual consulting assignments…

small and large…both related to structural geology

John A Hudson

Lecture 7

Wuhan – Feb 2008 – Unsolved Problems in Rock Mechanics and Rock Engineering

A fossil of

Archeopteryx

lithographica

in the Natural

History

Museum,

London, UK

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Tail feather

Approximately 0.5 m across

Wuhan – Feb 2008 – Unsolved Problems in Rock Mechanics and Rock Engineering 3

The Archeopteryx lithographica fossil is of a

transitional species between dinosaurs and birds.

The generic name, Archeopteryx, is developed from

the Greek words ‘ancient’ and ‘wing’; the specific

name, lithographica, alludes to the fact that the

fossil was found in the Solnhofen limestone in

Bavaria, this rock having been used for printing

purposes.

Imperial

College

Geological

Museum/

Natural History

Museum

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Wuhan – Feb 2008 – Unsolved Problems in Rock Mechanics and Rock Engineering

Archeopteryx lithographica: a bird-dinosaur

Natural History Museum

Some dinosaurs were large…

…but Archeopteryx lithographica

was only the size of a chicken

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The fossil was purchased in Victorian times by the Museum in

London, UK, because, as noted by Charig et al. (1986), it is “an

obvious and comprehensible example of organic evolution”.

However, in the 1980s, the authenticity of the fossil was

challenged by N.C. Wickramasinghe and F. Hoyle on the basis

that the fossil had been forged in the nineteenth century by

impressing a modern day feather into a layer of fresh plaster

spread over part of the fossil specimen.

Because dental instruments

had been used to expose

the fossil, it does have an

appearance somewhat of a

plaster model.

Solenhofen limestone used for

lithographic printing

The rock formation, and hence

the fossil, is of Late Jurassic

age, i.e., around 150 million

years old.

The rock has an extremely fine

grain.

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A Brazilian test on

Solenhofen limestone,

the central crack

illustrating

the rock’s fine grain

This accusation had some credibility because

a) both Wickramasinghe and Hoyle were well known scientists and

b) the specimen does superficially look as though it is made of dental

plaster because of the fine grained uniform nature of the

limestone.

Indeed, the Solnhofen limestone is used as a ‘type’ rock for rock

mechanics testing because of its uniformity and fine grain.

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In addition to the Museum’s own investigations, I was asked to study

the specimen from a rock mechanics point of view.

Did a part of the fossil appear to have been manufactured or not?

This Archeopteryx lithographica fossil is one of the most important in

the world and its authenticity is critically important for evolutionary

studies.

In particular, was the

tail feather impression

artificial? Had it been

created by pressing a

modern feather into a

coating of plaster on

top of a real fossil?

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Rock mechanics approach:

Obtain a core and study longitudinal

slices through the core…

Museum’s response:

Dr Hudson! You don’t understand

paleontological protocol!

Angela Milner

Dr Hudson: Please could

you prove that the rock is

genuine.

Crack traversing the feather barbs

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Calcite crystals have grown in the fracture.

A Victorian forger could not have artificially created such a

persuasive mineralised infill of the fracture.

In addition, as above, the en echelon nature of the fracture

formation is illustrated with a zone of staining around the

overlap, which is a phenomenon often observed on the larger

outcrop scale.

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The Museum also justified the fossil’s authenticity by “exactly

matching hairline cracks and dendrites on the feathered areas of

the opposing slabs, which show the absence of the artificial

cement layer into which modern feathers could have been pressed

by a forger”.

This conclusion is further supported by the fracture mineralisation.

This example is an unusual application of rock fracturing

knowledge, but one that once again demonstrates the value of

understanding the formation and characteristics of rock fractures.

Archeopteryx lithographica

A genuine fossil!

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Opencast Coal Mine, UK

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The

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Trucks used on site

The

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The

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Wuhan – Feb 2008 – Unsolved Problems in Rock Mechanics and Rock Engineering 19

Question: Our trucks are

using more fuel than we

expected, and much more

fuel than at a similar open-

cast site a few kilometres

away.

Please tell us why this is.

Is it our fault, or something

to do with the ground?

At a similar site 3 km

away, we didn’t have this

problem.

Wuhan – Feb 2008 – Unsolved Problems in Rock Mechanics and Rock Engineering 20 Listric faulting

Coal seam, low friction

The

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The

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It became apparent that the

near surface strata had

been disturbed by glacial

action.

This glacial action is

somewhat variable as the

glacier travels over irregular

ground: the near surface

ground at this site had been

disturbed…

…whereas that at the

adjacent site had not.

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Prof John Cosgrove explaining the effects of glacial

disturbance, e.g. the existence of small periclines at the site.

The

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So we weren’t able to save money on the use of the truck

fuel…

…but we were able to show why the near surface soft rock

conditions at this site were different to those at another site a

few kilometres awayi.e. because of localised glacial action.

End of Lecture 7

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