By: Ronda Kaysen
MANTUA TOWNSHIP (REUTERS).- Paleontologist Kenneth Lacovara is looking deep in a New Jersey silt mine for the exact moment, 65 million years ago, when all dinosaurs perished.

That secret could be harder to uncover if the fossils here can no longer be unearthed after a housing and retail development is built on this open pit.

Lacovara, an associate professor of biology at Drexel University in Philadelphia, looks at this 40-foot deep hole at the end of a dirt road and sees a line in the sand where the Cretaceous period begins and ends. Below that line are dinosaurs, above it, not a single one.

He thinks that the creatures his team has been uncovering here all died en masse when a meteor struck the earth and changed the course of geologic history. If his theory proves correct, it would be the only burial ground of its kind and provide scientists with a living laboratory to study how the dinosaurs became extinct.

New Jersey is the birthplace of dinosaur paleontology. The first nearly complete dinosaur skeleton ever discovered was a Hadrosauraus found in Haddonfield in 1858. But over the years, the numerous silt mines that made for great dinosaur digging were replaced with housing developments and strip malls.

Today, this site in a southwestern corner of the state is the only remaining mine for greensand, a silt used for fertilizer and water softener. It's also the only access to the late Cretaceous period on the entire eastern seaboard.

Scientists have been digging here for nearly a century, uncovering prehistoric sharks, crocodiles and even saber tooth herring. Two weeks ago, the team uncovered an 800-pound sea turtle estimated to be 65 million years old.

"This site is the last existing window into the ancient Cretaceous period in the eastern half of the United States. It's extraordinary," said Lacovara, who recently discovered a new species of dinosaur in Patagonia that is believed to be the second largest dinosaur ever found.

But the township of Mantua, a community of 15,000 people, has other plans for the site. Township officials would like to see the mine closed and a retail and lower cost housing development built in its place. A developer has drawn up plans that include shops and affordable housing.

At a meeting scheduled for July 15, they will discuss, among other things, the historic nature of the site and steps toward development.

Inversand, the mine's owner, has been operating the site since 1926, digging greensand. For years, the company has had a close relationship with paleontologists, alerting them when they came across large fossils.

"If we find something beyond the routine shark tooth or clam, we call them up," said Inversand president Alan Davis.

The biggest find he recalls happened in the 1960s, when workers came across the skull of a Mosasaurus, a giant sea lizard, that now resides at the New Jersey State Museum in Trenton.

Mining for greensand is no longer economically viable for Inversand and the company would like to end operations. If the mine were to shut down and the pump that continuously clears groundwater out of the area were to turn off, the hole would completely fill with water in a matter of weeks, transforming it into a lake. Davis says the mine could shut within three years.

Facing a looming deadline, Lacovara and his team have stepped up their efforts to dig, applying for grants and enlisting students and amateur paleontologists to shovel the gray, muddy sand for pieces of natural history.

"I love it. It's instant gratification," said Aja Carter, a freshman at Drexel University, who was volunteering at the site. She recently found a shark vertebra.

The scientists worry that without this pit, they'll lose a historic treasure trove.

"It will be devastating. It will be the end of an era for so many different reasons," said Jason Schein, assistant curator of natural history at the state museum and one of the lead scientists on the dig.

"Every season we find things here that are new to science."

(Editing by Barbara Goldberg and Greg McCune)