NEW ORLEANS (AP) — An archaeological project arising out of Hurricane Katrina's floods has turned up bits of pottery fired about 1,300 years before the first French colonists slogged into south Louisiana swamps.

The project also has turned up artifacts from later Native Americans, Spanish and American fortifications, as well as a hotel and amusement park near the mouth of Bayou St. John, once an important route from Lake Pontchartrain to New Orleans.

"It's very exciting," said state regional archaeologist Robert Mann, who was not involved in the dig but said he has looked at photographed artifacts. The pottery bits, he said, are from what is known as the Marksville period, from about A.D. 1 to A.D. 400, he said. The shards — or, as archaeologists call them, sherds — are incised with broadly spaced lines, making their age clear.

"They just yell out Marksville," Mann said.

Patterns stamped between the lines on the pottery pieces narrow the period to the late Marksville, between about A.D. 300 and A.D. 400, said state archaeologist Charles "Chip" McGimsey.

When the pottery was made, Southeast Louisiana was populated by hunter-gatherers. Most of their artifacts are found in trash heaps, made up mostly of shells from a freshwater clam that they ate by the billions. Some shell middens, or dumps, were a quarter-mile long and 10 to 20 feet high, McGimsey said.

At one time, such middens probably ringed Lake Pontchartrain, said Jerame Cramer, the Federal Emergency Management Agency's deputy environmental liaison officer with the Louisiana Recovery Office. Some evidence remains on the north shore but almost none on the south shore, he said.

The shells were mined as construction material into the early 20th century, McGimsey said. Cramer said other heaps washed away or were buried under concrete when the lakefront was armored against erosion.

Cramer and FEMA were involved in the dig because of a hazard mitigation grant program to raise and otherwise protect houses from storms after Hurricanes Katrina and Rita. More than 37,000 homeowners applied statewide, most of them in the New Orleans area.

Before the start of any construction project using federal money, the agency must investigate its effects on potential historic property.

FEMA, state and Native American officials agreed that, rather than going door to door, archaeologists should concentrate on public lands that might be used for emergency housing or temporary debris dumps. As part of the program, they would also check a few known archaeological sites and reanalyze some existing collections.

"The goal was to have people get their elevation grants as quickly as possible," Cramer said. "This is a very unique type of mitigation program. But Katrina was a very unique event."

The new pottery pieces were discovered at a site now called Old Spanish Fort. The French built a small, crude fortification there in the early 1700s, and the Spanish built a true fort in about the 1770s, Cramer said. Americans added a brick wall in the early 1800s, apparently digging deeper into the shells for a fresh foundation. A hotel was built there in 1829, and a casino and amusement park were added later.

It looks as if the Spanish leveled a shell mound, building their fort on the newly flattened area and using the shells they removed to raise low areas and make walkways, said Jason Emery, lead FEMA archaeologist on the project.

"I don't think any of us even knew there was a shell midden there originally," McGimsey said. "And to realize that so much of it was still undisturbed ... the fact that the fort was there has preserved it all these years."

Notes from earlier excavations at Old Spanish Fort had been lost, and cataloging those artifacts also was part of the project, Cramer said.

Emery said a preliminary estimate is that the archaeologists found about 100 sherds, about a dozen with decorations that can help identify when they were made. McGimsey said charcoal or shells from long vertical samples of soil will be carbon-dated to double-check the age.