Island’s buried treasures emerge as sands of time erode away
Last spring, my wife, Nancy, and I joined archaeologist Darrin Lowery and historian Dr. Ralph Eshelman and crossed the Delmarva Peninsula from Chesapeake Bay to offshore barrier islands.
Spring arrives more quickly along the Chesapeake than the Atlantic Coast. The land surrounding the Bay warms as the days lengthen and rivers filled with spring rain flow out to temper the Bay’s winter cold. Because the ocean takes months longer to reach warmer temperatures, the spring wind is sharp when it comes off that great reservoir of cold.
That environment is the distant future of the Chesapeake region; it has also been its distant past.
Lowery, executive director of a nonprofit foundation for archaeological research, took us down one of Virginia’s thousands of numbered country lanes to a local landing.
We ran out at flood tide aboard his small research vessel through the Shore’s labyrinth of salt marsh sloughs, then ran the boat up on a sandy inlet. Roiling whitecaps broke around us as the ebb tide rushed out against a stiff sea wind. The “U.S. Coast Pilot Volume 4” describes these inlets as having a “changeable entrance channel…unmarked and (which) should not be entered without local knowledge.”
We passed the weathered bones of a 19th century schooner wreck, her timbers held together by wooden treenails tightened with wooden wedges driven in to secure them.
Within minutes, Lowery picked up a piece of English lead-glazed slipwear, used in the 18th century to cool fresh milk and slow its spoilage. Lowery and Eshelman presumed that it came from a shipwreck and was originally part of a shipment of trade goods bound for the Colonies.
Lowery mentioned that he once found a broken brass ramrod more than a foot long. It had a small cannon bore of about 2.5 inches, and was perhaps used with a three-pounder. “It was bent,” he said, “and I’ll bet it was thrown overboard.” We crossed the island until we reached the rim of the ocean. As we stood there with the sea licking at our feet, I realized that I was looking at the Bay’s future, or more precisely, the end of the Chesapeake.
In the 1970s, the U.S. Army Corps of Engineers proposed to dredge channels to connect the tidal lagoons behind the Eastern Shore’s barrier islands and make them into links in the nation’s Intracoastal Waterway. The Corps’ proposal, which had various levels of support and opposition, pointed out that at current rates of sea-level rise, any concerns about societal effects would be moot, as the entire Eastern Shore would eventually disappear in the distant future. The impressive cliffs of Calvert would be washed away by surf and my home on the Patuxent River would be valuable oceanfront property.
Geologist/philosopher Jerry Schubel wrote about that prospect in the 1970s, noting that in terms of the planet’s history, the Chesapeake Bay is a very ephemeral feature. (He was unfairly called down by some who claimed that he had somehow excused the destructive human forces at work around the Bay.)
But Schubel’s time frame was right. The Bay is at best only 10,000 years old, and recognizable to our eye for only about the last 5,000.
In a future epoch, the Miocene and Eocene fossils for which Maryland and Virginia’s cliffs are so noted will tumble— along with the bones of extinct pleistocene mammals and the remains of colonial and industrial societies without regard to age— and be swept away.
Still, life burgeoned among our footfalls and we needed to tread carefully lest we destroy the artfully camouflaged eggs of black skimmers and oystercatchers, laid in couplets or triplets, on the open sand.
The beach, like most of these islands, has been eroding for hundreds of years, but perhaps more rapidly in the last century because of accelerated sea level rise.
Far to the island’s south, Virginia junipers and a tangle of maritime forest species could be seen as distant dark shapes. The up-wind and up-current southern end, though, is being swallowed as the sea sweeps sand away and consumes the forest.
The beach was desolate of vegetation save a few clumps of reed which caught blowing sand to form little dunes, creating a blown-out depression behind them.
We discussed the possible formation of the Delmarva bays: strange, circular water-filled depressions on the Eastern Shore. Mark Demitroff, a geologist has written that these were created by icy, semi-desert winds at the end of ancient glaciers. The discussion inspired Lowery to exclaim, “There’s one forming now!” as he pointed to the analogous process occurring here in the dry sands of an ocean beach.
Sand, in this case, is swept north along the barrier island faces, blowing off the island’s end into the water where it forms a point bar until tide and storm waves throw it back on the beach.
This winnowing process sorted some sands by density. There were bands of black sand, likely titanium-bearing grains of ilmenite, and one glistening area of purple. Eshelman identified it as garnet, its crystals tinted by manganese. Garnet was commercially mined through the 1950s and cemented to backing as abrasive garnet or sandpaper. Today, garnet is considered a semiprecious stone and is too costly to be wasted in such uses. Some gem quality garnets are found in Virginia granites from the Piedmont far to the west. Someday far distant, the sea will reach them.
Wind scour across the beach had exposed millions of objects: tens of thousands of shells, including large conches. Two species of conch were commercially harvested on the Shore for decades: the channeled whelk, Busycon canaliculatum and the knobbed whelk, Busycon carica, the shells of which can reach 5.5 by 8 inches and weigh more than half a pound.
Lowery pointed out that the spiral whorls of some knobbed whelks twisted opposite of the others. Until the 1970s, this was thought to be a separate species, the lightning whelk, Busycon contrarium. They are reported to reach 10–15 inches.
Today it’s known that they are probably the same species as the knobbed whelk. When the juveniles are exposed to higher temperatures, they occasionally develop a left-hand spiral.
All three whelks were greatly valued by native Americans. After eating the meats, they could carve beads of wampum from the twisted central columella. Even the unworked shell was traded with mainland and far-inland tribes until manufactured European glass beads destroyed the market.
Most remarkable on the beach, though, were the thousands of fossils. It is not easy to age these, because as these islands are rolled back by the sea, deeper layers containing fossils are torn from their matrix in the sea floor beneath the plane of the islands and cast ashore, destroying the stratigraphy by which fossils are usually aged.
There was a great variety in the jumble: 2-foot long fossil burrows, some of which preserved the scratchings from the crablike legs of their creators, the ancient the mantis shrimp Squilla. The burrows are casts where mud flowed into the vacant burrows and was gradually silicified into mudstone.
Fossil crabs emerge in the mudstone, too. We find many parts, but Nancy, to the envy of Eshelman and Lowery, comes up with a whole crab encapsulated in mudstone, its claws almost showing color as they peek out of the rock. Its points and crenellations on the carapace show clearly.
“Watermen on the Shore,” said Lowery, who was one himself, “claimed that these were crabs struck by lightning, a geologist would call them fulgerites, but we know better!”
Later, when geologist Rick Berquist examined the fossils, he explained that items like these were originally located on the back bay of the island, but because of the island eroding over itself, they are now found on the ocean side. He estimated that the crab fossils are 60,000–90,000 years old. Lowery, on the other hand, guessed that it could be from the boundary of the late Pliocene and the early Pleistocene, 2.2 million—1.8 million years old or then again, 400,000 years ago.
Mudstone varies in hardness from a chalky material that can be scraped with a fingernail to harder fragments worn flat in the surf that “tinkle” when struck with another stone. The tinkle, Lowery said, comes from silica in the rock and is called young coastal plain chert.
Given 100 million years or so, under the pressure of overlying sedimentary rock, it would become the gray chert found further inland that was once traded by Native Americans in those regions to tribes on the coast for projectile points. Some of those points, made from harder, more ancient stone, and dating back 13,000 years, are found on these islands.
Lowery, well-versed in Native American skills, took one of the cherts, and using a round hammer stone, flaked off pieces much as one would knap flint for a spear point. As we walked, he described the process, how he got the angles right, and by first blunting the edge, made a bi-face tool.
“Here,” he said, handing it to me, “you could clean a fish with this! Don’t let anyone tell you there aren’t tool-making resources out on these islands!” I attempted to make a similar tool, only to break it while chipping off the last flake.
Lowery talked about his foundation’s excavations on another island in the chain. In one ancient Indian encampment, he found the remains of shark and sea turtles that were perhaps butchered with tools such as the ones just made.
Eshelman and Lowery once found a blue whale jawbone in the inlet during an unusually low perigean tide. It was too heavy to carry and ferry back, and while they can point to where it is—or was—the tide has never been low enough to recover it for the Smithsonian Institution. (Eshelman and Lowery have an agreement with the museum to turn over any artifacts found on these islands.)
On this walk, Eshelman discovered two dolphin vertebrae. One, from thousands of years ago, is scored a dozen times by shark’s teeth. Was it a kill? A scavenged carcass? It’s in the Smithsonian now, part of the growing data on the predation of sharks upon marine mammals over the eons.
Lowery has found other amazing mammalian fossils that some geologists say really shouldn’t be found on these islands. Lawrey reels off a list of Pleistocene macrofauna: giant horned bison, perhaps Bison antiquus from two ice ages ago; a 13,000-year-old Columbian mammoth Mammuthus columbi, larger, more ancient than its American mastodon cousin, Mammut americanum; the skull and tusk of a walrus with a bone collagen date of 42,000-45,000 years; and a rear molar from the immense, extinct dire wolf Canis dirus. “One serious predator,” Lowery mused.
Beneath these substantial fossils and active modern geology, though, is the deep history of even more ancient times.
Signs of previous estuarine systems—fossil Chesapeake Bays—or more properly the mouths of Virginia Capes, are entombed beneath the present landscape. Geologist Jeff Halka, and two colleagues have used seismic techniques borrowed from petroleum exploration to map these ancient channels.
These connections to the Atlantic pierced, and the sea continues to jumble, fossil deposits from the past 10 million years or so, in the shallows and on the beaches.
The modern whelks and hard clams at my feet were interspersed with ancient Venus clams that John Weymiller at the University of Delaware aged at 2.1 million to to 2.2 million years old.
A collector might view this beach as an amazing cabinet of curiosities while for the serious scholar it would be a bewildering nightmare!
Lowery put it in context for a future glaciation: “Just assume some huge pump has sucked down the Chesapeake and adjacent sea by about 60 feet and you can view the landscape around today’s Bay mouth as what lies beneath us here.”
Given what we know, it’s likely that in the future, the region will repeat history and alternately be swallowed by the sea and then be withdrawn to some wild and arid post-glacial landscape again.
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