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City-sized fossilized forest found

April 23, 2007
Courtesy University of Bristol
and World Science staff

Re­search­ers have found a cit­y-sized fos­sil­ized for­est in an Il­li­nois coal mine, and they say it trans­forms our un­der­stand­ing of the Earth’s first rain­for­ests.

No­where else, sci­en­tists say, can one lit­er­al­ly walk through such a huge swath of rain­for­est from the Car­bon­if­er­ous era. That was a time 360 mil­lion to 290 mil­lion years ago when true rep­tiles ap­peared, gi­ant dra­gon­flies buzzed and vast swamps spread, which lat­er formed coal.

De­tail of a pter­i­do­sperm, an ex­tinct seed-pro­duc­ing fern-like plant. The im­age shows an area about six cm (2.4 inch­es) in height. (Cour­te­sy How­ard Fal­con-Lang)

A huge earth­quake 300 mil­lion years ago caused the whole re­gion around this for­est to col­lapse be­low sea lev­el, ac­cord­ing to the sci­en­tists. Mud then bur­ied the ter­rain and pre­served it for­ev­er.

The for­est offers a bi­zarre med­ley of ex­tinct plants. They in­clude plen­ti­ful club mosses, or pri­mi­tive moss-like plants, more than 40 me­tres (131 feet) high. These tow­ered over mixes of tree ferns, shrubs and tree-sized horse­tails.

The for­est was found by How­ard Falcon-Lang of the Uni­ver­si­ty of Bris­tol, U.K., and U.S. col­leagues. The find­ings are pub­lished on­line Ap­ril 23 in the re­search jour­nal Ge­ol­o­gy.

“It was an amaz­ing ex­pe­ri­ence. We drove down the mine in an ar­moured ve­hi­cle un­til we were a hun­d­red me­tres” or 109 yards un­der­ground, Fal­con-Lang said. 

The for­est was root­ed a­top the coal bed, “so where the coal had been mined away the fos­sil­ized for­est was vis­i­ble in the ceil­ing of the mine,” he added.

Mod­ern club moss. Its an­ces­tors reached the height of trees dur­ing the Car­bon­if­er­ous. (Cour­te­sy Na­tion­al Park Serv­ice)

“We walked for miles and miles along pitch-black pas­sages with the fos­sil for­est just above our heads. We were able to make a map of the for­est by the light of our min­er’s lamps.”

The larg­est fos­sil for­est known, it co­vers an ar­ea 10 km by 10 km (six miles by six miles), he said. This would co­ver the city of Bris­tol, U.K. The fos­sils pre­serve a unique snap­shot of what trop­i­cal rain­for­ests were like 300 mil­lion year ago, he re­marked.

“As there is noth­ing like it around to­day, be­fore our work we knew very lit­tle about the ec­o­log­i­cal pref­er­ences and com­mu­ni­ty struc­ture of these an­cient plants,” Fal­con-Lang said. 

“This spec­tac­u­lar disco­very al­lows us to track how the spe­cies make-up of the for­est changed across the land­scape, and how that spe­cies make-up is af­fect­ed by sub­tle dif­fer­ences in the lo­cal en­vi­ron­ment.”

The study re­con­structs a Car­bon­if­er­ous rain­for­est on the larg­est scale ev­er at­tempted. The fos­sils show that the Earth’s first rain­for­ests were high­ly di­verse and that the types of trees changed across the an­cient land­scape, he said.

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Researchers have found a city-sized fossilized forest in an Illinois coal mine, and say it transforms our understanding of the Earth’s first rainforests. Nowhere elsewhere, scientists say, can one literally walk through such a huge swath of rainforest from the Carboniferous period—an era 360 million to 290 million years ago, when true reptiles appeared. So did vast swamps, which later turned to coal. A huge earthquake 300 million years ago caused the whole region of the forest to collapse below sea level, whereupon mud buried it and preserved it forever, according to the scientists. The forest contains a bizarre medley of extinct plants: abundant club mosses, more than 40 metres high, towering over a sub-canopy of tree ferns, intermixed with shrubs and tree-sized horsetails. The forest was found by Howard Falcon-Lang from the University of Bristol, U.K., and U.S. colleagues. The findings are published online today in the research journal Geology. “It was an amazing experience. We drove down the mine in an armoured vehicle until we were a hundred metres (109 yards) below the surface. The fossil forest was rooted on top of the coal seam, so where the coal had been mined away the fossilized forest was visible in the ceiling of the mine,” Falcon-Lang said. “We walked for miles and miles along pitch-black passages with the fossil forest just above our heads. We were able to make a map of the forest by the light of our miner’s lamps.” The largest fossil forest known, it covers an area 10 km by 10 km (six miles by six miles, which would cover the city of Bristol, U.K.) The fossils preserve a unique snapshot of what tropical rainforests were like 300 million year ago, he said. “As there is nothing like it around today, before our work we knew very little about the ecological preferences and community structure of these ancient plants,” Falcon-Lang said. “This spectacular discovery allows us to track how the species make-up of the forest changed across the landscape, and how that species make-up is affected by subtle differences in the local environment.” The study reconstructs a Carboniferous rainforest on the largest scale ever attempted. The fossils show that the Earth’s first rainforests were highly diverse and that the kinds of tree species changed across the ancient landscape, he said.