A dozen scientists from Sweden, Australia, France, Japan and the U.S. stood in a meadow in northern Harford County yesterday and pondered a 6-foot deep pit carved out by a backhoe.
Did bathmat-sized wedges of red dirt in opposite walls of the pit represent a scar from the last ice age, when glaciers crept as far south as Allentown, Pa., and Maryland was as cold and barren as Siberia?
Bloomsburg State University geologist Duane D. Braun and Maryland state geologist Emery T. Cleaves, who found the wedge during a routine soil survey June 1, argued that it was a crack caused by freezing and thawing of the ground toward the end of the last ice age, about 25,000 years ago.
The wedge appears to be the long-expected but never previously found proof, said Dr. Cleaves, that Maryland's piedmont was part of a periglacial area, or region bordering a glacier.
"This is the first time we've had any evidence that, yes, the piedmont was effected by the glaciers too," said the 56 geologist, now director of the Maryland Geological Survey.
Friday's visit from a delegation of international geologists, all attending the International Geographical Congress in Washington, was seen as the acid test for the discovery. They pulled up in a caravan of minivans in the afternoon, bouncing across the forest-ringed meadow in Palmer State Park, just outside a rural crossroads called McCann's Corner.
French geologist Jean-Pierre Lautridou, a cigarette dangling from his lips, circulated through the small crowd, pulled a 3-inch pocket knife out of his shapeless white cotton jacket and scratched a wall.
"There is a problem here," said Dr. Lautridou, president of the International Geographical Union's committee studying frost action.
The red claylike dirt inside the wedge, he said, looked too much like the surface soil. "This is not relic soil," he said.
"What's the point?" asked an uneasy Dr. Braun, who was squatting in the pit.
Also, Dr. Lautridou continued calmly, the edges of the wedge were not pushed upward near the surface, which is typical of periglacial wedges. Instead, he said, the ledge might merely be a gully carved out of the surrounding claylike rock, called saprolite, in relatively recent times.
The only way to be sure would be to dig up more of the field, to see if the cracks formed a telltale hexagonal pattern. Dr. Braun objected that this would be an enormous task and insisted the evidence was consistent with an ice wedge.
"I don't believe it's a gully for a minute," agreed Bob Galloway, a lanky, white-haired geologist from Australia.
As his colleagues boarded the vans, Takuma Arii of Taisho University in Tokyo quietly approached Dr. Cleaves, smiled broadly and congratulated him on his find.
"You had the inspiration?" Dr. Arii asked.
Dr. Cleaves admitted he had, along with two colleagues. But, Dr. Cleave added, he was just trying to map soils of a portion of Harford County when he found it.
"This is just luck," he said.