Prince of Wales Island piques interest of paleontologists worldwide
KETCHIKAN - The sun has barely risen over Prince of Wales Island, and Tongass National Forest geologist Jim Baichtel has solved one small scientific riddle.
"Sue Karl, this is Heceta," he calls to his colleague from the U.S. Geological Survey.
Baichtel is standing on top of a cliff in a rock pit somewhere near Coffman Cove, peering at part of a clam-like fossil called a brachiopod.
Heceta refers to a type of limestone found on Prince of Wales Island.
"The reason why they call them brachiopods is they have that structure that holds their gills in the inside, that structure is the central line right here," he said, pointing to the fossil.
"There's only one brachiopod that exists in these rocks that has that central line and it's limited to one age unit. It's a Kirkidium."
A minute later, Baichtel and Karl spot a tiny circle in the rock - a sponge commonly found in Heceta limestone that cinches the verdict. The two will mark the type of rock, along with the GPS coordinates, on a map.
Karl said the work is a bit like playing Sherlock Holmes. And the mystery is where this section of Southeast Alaska - which geologists call the Alexander terrane - was about 420 million years ago.
"If these beds are dipping like this, we should be able to go for miles in that direction and that direction. If that doesn't happen, you have to figure out where the faults are that are preventing us from tracking them," she said.
"Now we've got them on a map, and we're starting to have a logical, sensible understanding of why the limestones are breaking up. And that's the fun part. Trying to put the puzzle together to make sense."
Prince of Wales Island fossils are attracting growing interest from paleontologists worldwide.
Recent research has connected Southeast Alaska's Alexander terrane with fossils in Siberia and the Ural Mountains and with Southwest Alaska.
The Alexander terrane, which starts near Prince Rupert, includes Prince of Wales Island, Kuiu Island, Chichagof Island and part of Glacier Bay. The land mass stretches toward the Yukon, though not everyone agrees where it ends.
Robert B. Blodgett, an invertebrate paleontologist at Oregon State University in Corvallis, is leading a team of paleontologists studying Prince of Wales Island fossils.
He said geological literature noted similarities between fossils from Southeast Alaska and Russia as far back as 1907, but a direct connection only has been suggested in the past decade. Previously, scientists believed this part of Southeast Alaska came up from northern California, he said.
"The Alexander terrane was a volcanic island arc like Hawaii," Blodgett said. "The only analogs they have are in the Ural Mountains, and the same thing in Southwest Alaska. They all were probably close together, probably the margins of a single continent, probably Siberia, and have nothing to do with North America."
Several papers on Prince of Wales Island paleontology were presented at a meeting of the Geological Society of America's Cordilleran Section meeting in Puerto Vallarta, Mexico, in April. More publications are planned, Blodgett said.
"It's really caught on, and I think it has 80 to 85 percent acceptance as a working model," he said. "Nothing is ever 100 percent, but all the best evidence points here."
Much of Alaska appears to have been part of Eurasia, added to the margin of western North America through a process of sea-floor spreading, said Blodgett.
One exception - a triangular portion of east-central Alaska bound on the northwest by the Porcupine River and on the southwest by the Yukon River - was part of ancient North America, he said.
During work on Prince of Wales last month, Karl and Baichtel searched for new rock outcrops as they drove along the island's bumpy logging roads in a Forest Service pickup. Each stop offered new clues.
"What we're trying to do with the fossils is unravel what's happening here 420 million years ago, during the Silurian (period)," Karl said. "We know during the Ordovician around here, which was 450 million years ago to 490 million or so, it was deep water. But then it got shallow and there were these big reefs with all these fossils and sponges. It got shallower during the Devonian because these rocks are fluvial; they're from rivers."
Parts of Prince of Wales Island are rich with fossils. The Heceta limestone contains algae and sponges, along with brachiopods, corals, bivalves and ornate snail-like gastropods. A younger formation called Wadleigh limestone near Craig and smaller islands to the west of Prince of Wales contains corals, brachiopods, gastropods and an extinct group of squid-like ammonoids.
"It's really world-class preservation, better than anything you'll get anywhere in western North America," Blodgett said. "It's better than Nevada for the Devonian and the Silurian."
The work offers clues about the area's paleobiogeography, or the ancient geographic distribution of fossil animals and plants. It also gives scientists a better understanding of how the margins of the ancient Pacific Ocean called Panthalassa evolved, Blodgett said.
Area residents can expect to see geological tourism increase, Blodgett said. He encourages residents to think about developing a regional museum of natural history.