September 9, 2008

Ancient Forest Discovered in Mines

Researchers from the US and the UK have found a fossil forest in the coal mines of Illinois.

The team reported a similar discovery last year, but has recently found five other examples.

The petrified vegetation is visible in the mine ceilings covering thousands of hectares.

Dr. Howard Falcon-Lang believes they are among the first forests to evolve on Earth.

"Theses are the largest fossil forests found anywhere in the world at any point in geological time," Dr. Falcon-Lang said.

"It is quite extraordinary to find a fossil landscape preserved over such a vast area; and we are talking about an area the size of (the British city of) Bristol."

The forests are stacked on top of each other in the rock, and grew just a few million years apart.

The forests appear to have suffered many periods of flooding and subsidence.

The forests have become visible thanks to extensive mining in the border region between Illinois, Indiana, and Kentucky.

When the coal seams are removed, researchers are able to see the forests from the bottom-up.

"It's kind of an odd view looking at a forest bottom-up. You can actually see upright tree stumps that are pointed vertically up above your head with the roots coming down; and adjacent to those tree stumps you see all the litter. We found 30m-long trunks that had fallen with their crowns perfectly preserved," researchers reported.

The team believes the study of these forests could give clues as to how modern rainforests might respond to a warmer world.

The forests are believed to have thrived during a period 306 million years ago that saw an icy climate with large ice caps warm to a greenhouse climate with melted ice caps.

"The fascinating thing we've discovered is that the rainforests dramatically collapse approximately coincident with the greenhouse warming," said Dr Falcon-Lang.

"Long-lived forests dominated by giant club moss trees almost overnight (in a geological sense) are replaced by rather weedy fern vegetation."

The next step of the research is to find the correct timings of the events, and work out the exact conditions that existed.  The findings could then be compared with current conditions.


Image Caption: Fossilised ferns were preserved in the tunnels of more than 50 coal mines in Illinois, U.S (Univeristy of Bristol)


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