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“Oldest” fossilized forest revealed

March 3, 2012
Courtesy of Cardiff University
and World Science staff

A fos­sil for­est in the Cats­kill Moun­tains in up­state New York is not only the old­est forest known—it’s also much more com­plex than once thought, re­search­ers are re­port­ing.

The Gil­boa fos­sil for­est is be­lieved to date back 385 mil­lion years. Nor is it new to sci­ence: fos­sils of hun­dreds of large stumps of a type of tree dubbed the “Gil­boa tree” first turned up in the 1920s dur­ing ex­cava­t­ion of a quar­ry to ex­tract rock to build the near­by Gil­boa Da­m. But only lim­it­ed in­forma­t­ion was recorded at the time, and the quar­ry was soon back­filled.

Chris Berry of Cardiff University studies the stump of a Gil­boa tree. (Cour­tesy of Car­diff U.)


In May 2010, the quar­ry was par­tially emp­tied as part of a da­m main­te­nance proj­ect. Re­search­ers were mon­i­tor­ing the site with con­trac­tors and found where the orig­i­nal quar­ry floor had been ex­posed, and the roots and po­si­tions of the trunk bas­es pre­served. 

“We were able to ar­range for about 1,300 square me­ters to be cleaned off for in­ves­ti­ga­t­ion. A map of the po­si­tion of all the plant fos­sils pre­served on that sur­face was made,” said Chris Ber­ry, an earth sci­ent­ist at Car­diff Uni­vers­ity in Wales.

The find­ings by Ber­ry and col­leagues are pub­lished in the March 1 is­sue of the the jour­nal Na­ture. They de­scribe bas­es of the “Gilboa trees” as spec­tac­u­lar bowl-shaped pits up to nearly two me­ters (yards) wide, sur­rounded by thou­sands of roots. These are be­lieved to be the bas­es of trees up to about 10 me­ters high, that looked some­thing like a palm tree or a tree fern.

One of the big­gest sur­prises was that the re­search­ers found many woody, horizontally-lying stems, up to about 15 cm (6 inches) thick. The in­ves­ti­ga­tors de­ter­mined that these were ground-running trunks of an­oth­er type of plant called an aneu­ro­phy­ta­lean pro­gym­no­sperm, only pre­vi­ously known from up­right branches. They al­so found one large ex­am­ple of a tree-shaped club moss, the type of tree that com­monly forms coal seams in young­er rocks across Eu­rope and North Amer­i­ca.

“All this demon­strates that the ‘old­est for­est’ at Gilboa was a lot more eco­logic­ally com­plex than we had sus­pected, and probably con­tained a lot more car­bon locked up as wood than we pre­vi­ously knew about. This will ena­ble more re­fined specula­t­ion about the way in which the ev­o­lu­tion of for­ests changed the Earth,” Ber­ry said. “Per­son­ally, the chance to walk on that an­cient for­est floor, and to im­ag­ine the plants that I have been stu­dy­ing as fos­sils for more than 20 years stand­ing alive in the po­si­tions marked by their bas­es, was a ca­reer high­light.”


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A fossil forest in the Catskill Mountains is the oldest one known, and is more complex than once thought, researchers are reporting. The Gilboa fossil forest, in the Catskill Mountains in upstate New York, is believed to date back 385 million years. Nor is it new to science: fossils of hundreds of large stumps of a type of tree dubbed the “Gilboa tree” first turned up in the 1920s during excavation of a quarry to extract rock to build the nearby Gilboa Dam. But only limited information was recorded at the time, and the quarry was soon backfilled. In May 2010, the quarry was partially emptied as part of a dam maintenance project. Researchers were monitoring the site with contractors and found where the original quarry floor had been exposed, and the roots and positions of the trunk bases preserved. “We were able to arrange for about 1,300 square meters to be cleaned off for investigation. A map of the position of all the plant fossils preserved on that surface was made,” said Chris Berry, an earth scientist at Cardif University in Wales. The findings by Berry and colleagues are published in the March 1 issue of the the journal Nature. They describe bases of the “Gilboa trees” as spectacular bowl-shaped pits up to nearly two meters (yards) wide, surrounded by thousands of roots. These are believed to be the bases of trees up to about 10 meters high, that looked something like a palm tree or a tree fern. One of the biggest surprises was that the researchers found many woody horizontally-lying stems, up to about 15 cm (6 inches) thick. The investigators determined that these were ground-running trunks of another type of plant called an aneurophytalean progymnosperm, only previously known from upright branches. They also found one large example of a tree-shaped club moss, the type of tree that commonly forms coal seams in younger rocks across Europe and North America. “All this demonstrates that the ‘oldest forest’ at Gilboa was a lot more ecologically complex than we had suspected, and probably contained a lot more carbon locked up as wood than we previously knew about. This will enable more refined speculation about the way in which the evolution of forests changed the Earth,” Berry said. “Personally, the chance to walk on that ancient forest floor, and to imagine the plants that I have been studying as fossils for more than 20 years standing alive in the positions marked by their bases, was a career highlight.”