BY BEN RAINES
MOBILE, Ala. — An ancient forest found 60 feet underwater about 10 miles offshore of Alabama is much older than originally thought.
Al.com collected samples of the trees during a scuba diving expedition to the forest. Those samples were sent to the Lawrence Livermore National Laboratory for radiocarbon dating and found to be more than 50,000 years old.
Scientists who examined the trees remarked on how well preserved the wood was. Cut into a piece and the unmistakable aroma of newly sawn cypress blooms up, despite millennia spent at the bottom of the Gulf of Mexico. Some of the pieces still had bark on them. The forest was apparently buried under a thick layer of sand for eons until it was uncovered by giant waves during Hurricane Katrina.
"It is a little darker in color than a piece of modern cypress, but if I didn't tell you that it was over 50,000 years old, you wouldn't know it," said Kristine DeLong, the Louisiana State University researcher who prepared and sent the AL.com samples for analysis. "I showed it to some of the other professors and they couldn't believe the wood was that well preserved. It's amazing it has held up. When I cut into them, they smelled just like you were cutting into a cypress tree."
DeLong inspected the tree samples under a microscope and said the cell structure typical of cypress trees remained intact. Bits of sap appear to be present in photos of the freshly cut wood.
Paleontologists contacted by AL.com originally speculated the trees were between 8,000 and 12,000 years old, based on the present depth where the forest is located and the distance from shore. Those dates fit nicely with Gulf Coast sea levels during the most recent ice age. The new, older time frame links the trees to a much earlier ice age.
And, it provides evidence that coastal Alabama has risen between 60 and 120 feet in the last 50,000 years.
"Trees that are 50,000 to 80,000 years old, they should be down 120 feet to 180 feet underwater. But these are sitting at 60 feet. That means that coastline has come up about 60 to 100 feet. That's unusual," said DeLong.
Working from a variety of geological signs both above water and below, scientists have been able to create maps of where the Gulf shoreline was going back millions of years.
The trees have proven to be a conundrum. Places that are now 60 feet underwater were typically dry land about 12,000 years ago, DeLong said, which led several scientists to guess the trees were growing during an era known as the younger Dryas. But these trees proved to be too old for radio carbon dating, which means they are at least 50,000 years old. That means the trees were probably growing during an earlier ice age, one that occurred 50,000 to 80,000 years ago. There is an outside chance they are even older.
Scientists studying both ancient and modern day shorelines have documented that Louisiana is sinking. The research also shows that Alabama and a portion of the Texas shoreline have risen.
"If part is sinking, somewhere else, it has to rise," DeLong said. "We see that in Alabama, and out around Galveston, Texas. On our timescale, it might be rising a few centimeters a year. But over 20,000 or 30,000 years, that begins to add up."
DeLong said she was amazed at the condition of the wood samples when she received them. The outer edge of the pieces is pockmarked from marine worms and other creatures, but those damages are only on the surface of the wood. Inside, the trees are still so hard that even a knife dragged across them barely makes a scratch.
The samples were collected using a small handsaw. DeLong planned to dive the forest with an al.com reporter on a subsequent trip along with a couple of members of her research team, but the vessel broke down on the way to the site. The crew was carrying equipment to collect core samples from the trees, which would allow them to see how old the individual trees were. Another visit to the forest is planned when the weather warms up.
"If we get core samples, we can look at the tree rings and see what was happening with precipitation. We don't know what was happening with precipitation on the Gulf Coast during the ice ages," DeLong said. "We know that the area around the Great Salt Lake, and in Arizona and New Mexico, was very wet. That it rained a lot. And that is desert now. But we don't know what was happening on the Gulf Coast."
The relic forest hints at what the Mobile-Tensaw Delta looked like before man began cutting down the trees in the 1800s. Imagine a forest of giant trees, trees that rivaled the redwoods in California for size.
"It's a really cool find. That the trees are in the ocean and are that old, it floors me," DeLong said. "We didn't expect them to be that old. They were buried for a long time."