Miami-Dade County

Miami archaeological dig unearths evidence of sea rise

Archaeological and Historical Conservancy executive director Bob Carr, in blue, and archaeologist Ed Barberio survey the final stages of a dig in downtown Miami on the north bank of the Miami River where workers have found artifacts indicating more than a foot rise in sea level since the late 19th century. Scientists believe industrialization accelerated sea level rise over the last century.
Archaeological and Historical Conservancy executive director Bob Carr, in blue, and archaeologist Ed Barberio survey the final stages of a dig in downtown Miami on the north bank of the Miami River where workers have found artifacts indicating more than a foot rise in sea level since the late 19th century. Scientists believe industrialization accelerated sea level rise over the last century. Miami Herald Staff

In the shadows of a condo canyon rising around the mouth of the Miami River, archaeologists have unearthed what they say is concrete evidence of South Florida’s escalating rise in sea level.

Or brick evidence, to be more precise. Ten bricks. And some coconut palms.

“It’s the first line of evidence something had really changed here in terms of sea level,” archaeologist Bob Carr said Tuesday at the Met Square construction dig on Fourth Street where a team is excavating a 2,000-year old Tequesta Indian village in downtown Miami. The site will eventually be showcased in a towering entertainment complex — a compromise after a contentious debate last spring over preserving the city’s ancient history.

Carr and his team discovered the submerged bricks, dating to the Civil War, about four months ago along a slice of old shoreline long buried a few feet deep under a parking lot. The find was not unexpected — Carr knew Fort Dallas occupied the site in the 1800s before famed industrialist Henry Flagler built his Royal Palm Hotel and lush gardens at the end of the 19th century.

But when Carr started to piece together where the 1860s-era bricks were found — about a foot below the water table — and what he knew about construction, he came to a surprising conclusion: the artifacts provided proof that sea level in the area had risen more than a foot in the last century. Neither the bricks nor coconut palms would have existed on submerged land.

“Numbers don’t go back a long time in South Florida. So this is physical evidence,” he said as he toured the site, a moonscape of exposed bedrock pocked with holes.

Climate change occurred naturally over the eons because of organic causes — something scientists know by analyzing indirect measures like ice cores, tree rings, glacier lengths and ocean sediments. But after the Industrial Revolution began pumping carbon into the atmosphere, temperatures started climbing, said University of Miami geologist Hal Wanless. Finding the bricks supports the theory, he said, that sea levels started rising rapidly in South Florida because of the increased carbon.

Finding historic evidence, though, is rare.

At the time, frontier Florida was confined to a narrow strip of high ground perched between the Everglades and Biscayne Bay. The human footprint left behind was small, except at the Miami River.

“The Miami River has always been prime real estate,” said Wanless, who used oysters migrating up area piers three decades ago to track rises in sea level.

Carr, who has excavated Indian sites throughout South Florida, said he has found ancient evidence of changing sea levels but never relatively modern proof of the accelerating rise.

Carr, Miami-Dade County’s first archaeologist, began examining the site in 2004, two years after MDM Development announced plans to build the hotel and entertainment complex. Carr had discovered the Miami Circle, likely a ceremonial site used by the Tequesta, on the river’s south bank in 1998 and helped get the area designated as archaeologically sensitive. So he expected artifacts of the ancient tribe would turn up on the opposite bank. He eventually found 11 foundation circles, along with human remains and a trove of shells, pottery shards and discarded bones that provides a glimpse into Tequesta daily life.

He also expected to find remnants of Flagler’s hotel — well-documented in photographs of early well-heeled tourists — as well as the 19th century army fort. What was unexpected lay in a slice of excavated bank now well below the water table: a brick pier, possibly part of a building foundation, and an iron plate, along with the coconut palms.

Workers digging in units across the site have gradually excavated soil and sediment to reveal a sloping bank. They have found turtle bones, conch shells fashioned into shovels and shards of Fort Drum Punctate, a distinctive pottery used by the Tequesta.

At the southern edge, the bedrock or karst, has been chiseled into smooth solution holes, indicating it was once covered with water. Further north, the bedrock levels out, indicating dry land, Carr said. When Flagler arrived, the rocky shoreline snaked under what is now the Epic Hotel, sloping diagonally northeastward toward the bay. To create his lush garden, Carr said Flagler, “the first person to seriously create a landfill in Miami,” moved the Tequesta midden to level out the ground and plant trees. While Flagler used brick piers, the bricks Carr located were much older.

Carr also unearthed dozens of conch shells, which scientists will be able to study to determine changes in the environment and “reconstruct early history.”

“We’re getting pieces of an ancient jigsaw one post at a time,” he said. “It’s a huge reservoir of scientific information about the environment and prehistoric Miami.”

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