The first building stone one of your relatives encountered in the United States was probably Salem Limestone, too. The off-white, fossil-rich stone trims walls and doorways at the immigration station at Ellis Island, built in 1900. Open until 1954, Ellis Island welcomed 12 million immigrants; over 40 percent of all Americans can trace their ancestry to those who walked through the island’s Salem-framed doorways. Perhaps a few geologically inclined emigrants backed up the line as they gazed thoughtfully at the fossils.
You are probably even carrying with you a picture of a building that incorporates Salem. Reach into your wallet and pull out a bill. If it is a five, a twenty, or a fifty, turn it to the back and look at the building. The White House and U.S. Capitol, although not built originally of Salem rock, have used the limestone extensively for repair work, and Abraham Lincoln sits on his marble chair surrounded by Salem Limestone.2 And if you don’t carry bills, then you have probably mailed a letter from one of the more than 750 post offices built with Salem blocks or perhaps paid a fine, obtained a marriage certificate, or watched a legislative session at one of the more than two hundred Salem-sheathed courthouses or twenty-seven state capitols.
“So many monuments and landmarks are made from the Indiana limestone that it is a holder Of American memory,” says limestone sculptor Amy Brier.3 She is right. Other stones are older, more beautiful, and have more noble pedigrees, but no other building stone forms as much a part of the collective cultural fabric of the United States as the Salem. No other stone has contributed more to giving our cities and towns a sense of elegance and pride. No other stone deserves to be called America’s building stone.
Three hundred and thirty million years ago, during the Mississippian Period, you could have sailed a boat across most of the middle part of North America. You would have floated over future Illinois, Kansas, Iowa, Colorado, Arizona, and Indiana, though you would not have moved fast because you were in the windless zone of the globe we now call the Doldrums. In addition, you would have needed plenty of sun-block, as your boat would periodically cross the equator, which, because North America tilted almost 90 degrees to the northeast, ran from about modern-day San Diego through Duluth,Minnesota. In many areas, particularly around Indiana, the water was less than twenty feet deep.
Geologists know all this because the equatorial sea deposited sediments preserved in rocks across the country. At the Grand Canyon, a several-hundred-foot-thick layer of rock known as the Redwall Limestone formed in this shallow sea and shares the Salem’s brachiopods, bryozoans, and crinoids. In eastern Colorado, geologists refer to their Mississippian Sea limestone as the Spergen, but in Kansas and Illinois the name reverts to the Salem Limestone, named from early quarries near Salem, Indiana.
As you sailed along, you could have traveled north and west for many days without seeing any land. Most of North America spread to the east and northeast, as a lowland now called Wisconsin and Canada. Far to the southeast, the eroding Acadian mountains rose out of the water. Staying in the south but moving west, you would have sailed off the platform of shallow water into a deep basin. The first landmass you would have seen was Gondwana, inching toward a collision with North America. Another range of mountains was also pushing up to the west, running at about a thirty-degree angle northeast from the equator. These mountains now stand in Nevada and are known as the Antlers.
Sailing along you would have noticed an additional facet of the water. Like the Bahamas, where modern limestone forms in a similar environment, the water would have been extremely clear because little or no sediment washed into the Salem sea. Any material that washed off of the mountains ended up in deep marine basins adjacent to the land.
The clear, warm, shallow water resulted in two characteristics of the Salem. One, the building stone section is nearly pure calcite, or calcium carbonate. All of the organisms that lived in the water had calcium carbonate skeletons or shells, and any sediment that accumulated consisted of calcium carbonate. Two, many of the sediments were round, like fish eggs. Known as oolitic grains, they formed when wave action rolled a particle and surrounded it in concentric layers of calcium carbonate, like what happens when you roll snow to build a snowman. Over the millions of years the sea covered the continent, it generated enough calcium carbonate to build up a ninety-foot-thick layer of limestone in Indiana.
If you had chosen to land on the shoreline abutting Indiana, the world would have seemed depauperate. No birds or mammals would have existed and the first dinosaurs were still almost 100 million years away. A few four-legged amphibians had traipsed out of the water, but scorpions, mites, spiders, and a host of insects would have dominated the terrestrial fauna. Ferns and low trees, including early conifers, would have formed extensive forests. Another 200 million years would have to pass before you could see the lovely deciduous trees that now flourish in Indiana.
Getting back in your boat on the shoreline, you would have sailed in a quiet lagoon, with a bottom covered in fine carbonate mud. Numerous invertebrates seeking food and building homes would have churned up the sediment and left faint traces of test-tube- and inverted-Y-shaped burrows, now preserved in the Indiana rock. If you climbed overboard and dropped into the oozy bottom, you could have collected a handful of mud, and if you had a microscope, you would have seen that although dead bodies made up most of the ooze, other life forms lived in the lagoonal graveyard. The microscope would have revealed a world populated by protozoans inhabiting one-twentieth-of-an-inch-wide shells, each made of a half dozen chambers coiled like a poorly made cinnamon roll.
Known as foraminiferas, they lived for a few months, died in the lagoon, and settled amid the billions of shells of their cohorts.4 Forams are an abundant fossil in some parts of the Salem, but because of their wee size they are rarely visible in the stone. When you see a Salem wall you are looking at a cemetery of epic proportions.
Floating out of the lagoon, you would have passed into a shoal complex that spread along the coast for tens of miles. These underwater sandbars and associated channels, called intershoals, would become the main rock units quarried for building material in the Belt. They were high-energy environments, shaped by daily tides, longshore currents, and periodic storms.
“We are now able to see primary sedimentary structures in the quarry walls. There are no other exposures in the world where you can see this level of sedimentary detail,” said Todd Thompson, another geologist at the Indiana Geological Survey.5 A change in cutting technology in the past dozen years has allowed Thompson and his colleague Brian Keith to trace the ancient ripples and troughs of the shoals. They follow the dune migrations in the protean sea by holding chalking parties where students mark features of individual shoals and intershoals at the quarries. “We have to move quickly because the quarrymen are pulling the stone out so fast that the evidence disappears almost immediately,” said Thompson.
By tracing out the bedding surfaces, the geologists can see the three-dimensional architecture of the ancient sandbars better than they could in any modern environment. At one quarry, Thompson found bedding with distinct thickening and thinning in groups of fourteen, which he interpreted as corresponding to fourteen days of deposition during the Mississippian Period.
One of Thompson and Keith’s goals is to understand the geometry of the shoals so that they can help quarry owners quarry the best stone with the least amount of waste. Despite their best intentions, however, “There is no geology in the stone business,” said Keith. Because habits and tradition guide the quarrying process, the quarrymen cut the walls in a rectilinear grid regardless of the geologists’ advice that the shoal bedding doesn’t follow precise lines.
Look at most any building with Salem rock and you will see Thompson and Keith’s complex pattern of bedding, with some flat, some angled, and some concave upward beds. I say most because the most expensive stone has fewer recognizable geologic features, which may make for “better” building material but more boring rocks, in the eyes and hearts of geologists.
Not all fossil-rich limestone got pitched aside; if it did builders would have little to work with. Many years ago, or so the story goes, two Chicago women traveled to Bloomington to look at limestone. They came across several discarded blocks loaded with fossils. The quarry owner told the women the stone was very rare and expensive. They bought the blocks. Ironically, one of the more highbrow social clubs in Seattle incorporates some of the better fossil-rich blocks of Salem Limestone that I have seen. Not wanting to cause a social brouhaha in my hometown, I haven’t pointed out to the fine folk of the club that they have what builders consider “inferior” stone.
Few of the fossil animals found in the Salem building stone inhabited the high-energy shoal environment. Instead, they lived farther out to sea, in slightly deeper and quieter water. If you had pulled yourself away from the microscope you could have swum down to the sea bottom and found Brian Keith’s trio of Mississippian beasties forming vast communities seaward of the Salem shoals.
Crinoids, also known as sea lilies, would have been the most obvious. They are one of the classic fossils found in limestones around the world. Widespread and abundant for hundreds of millions of years, only one group of crinoids has survived to the present and they now inhabit deep water. Crinoids anchored themselves to the substrate by a rootlike structure called a holdfast, out of which extended a stalk of stacked disks. The stalk supported the body, which consisted of a cuplike calyx and arms, usually 10 but ranging up to 250. The arms, which helped catch suspended food particles, were flexible and often broke. When they did, two new ones emerged. A fully erect Salem crinoid, what one crinoid specialist called a “a feathery starfish on a stick,” could be twelve inches tall.6
Cruising along the sea bottom, you also would have seen housing colonies of interconnected rooms that looked like ice-cream cones anchored to the substrate, although some would have looked like an ice-cream cone twisted into a corkscrew. Inside each pinhead-sized room would have lived a tubular bryozoan. Water flowing across the netlike structure provided food for the hundreds or thousands of tentacled bryozoans that formed the colony. The delicate fronds might be compared to brownstone row houses—squat and extensive—relative to the sleek crinoids that towered above the three-inch-tall bryozoans.
You wouldn’t have had any problem locating the final member of the trinity. Brachiopods look like clams, but like bryozoans, to which they are closely related, they wouldn’t have moved. Often called lamp shells, for their resemblance to bowl-like oil lamps, brachiopods were one of the most abundant invertebrates of the marine world and could form dense colonies. At least twenty species of brachiopod dwelled in the Salem waters.
The Salem sea, however, was not an inert world populated only with immobile invertebrates. Numerous snails slithered across the seafloor, periodically stopping for a bite off a brachiopod or bryozoan. And you could have been a meal for the sharks that plied the waters. The largest ones had teeth over two inches long and bodies the length of an SUV.
When the invertebrates died, and they died by the billions, currents would have transported them out of the deeper water up toward the shoals and channels. Wave action then blenderized the bodies as shells and exoskeletons crashed against each other and broke into hundreds of pieces. The battered beasts piled up in an unsorted stew of body parts, comparable to the coquina used at Castillo de San Marcos, except the Salem sediments were finer grained.
Over time the unconsolidated Salem shells and skeletons compressed under the weight of more bodies and became denser and harder. What had started as a coquina had been converted over millions of years to a limestone. You can still recognize the shells and skeletons, but they look like fossils and not like recently dead animals, as they do in the walls of the castillo.
Salem Limestone shares one other characteristic with the Florida coquina. Cutters, carvers, and sculptors can work the Salem in any direction. The rock is so pure and homogenous that its bedding has little effect on how one shapes the stone. No matter how quarrymen slice or carve the rock, it has the same strength and durability. This feature, more than any other physical asset, helped make the Salem popular with everyone from Odd Fellows to opera fans, or at least to the people who designed buildings for them.
Historians recognize one Richard Gilbert as the first to quarry Salem Limestone. Starting in 1827, his small ledge along a creek at the northern end of the Belt provided stone for chimneys, monument bases, and bridge piers. Toward the southern end of the Belt, Dr. Winthrop Foote established the quarrying industry in Bedford in 1832, when he hired a man named Toburn, a stonemason from Louisville,Kentucky. Toburn’s best-known work is the Foote family tomb, cut directly into a ledge of limestone. The tomb, reached by taking a side road east of town and walking a hundred feet down a beer-can-strewed path in the woods, no longer has crisp edges but has otherwise weathered well its many decades of rain, snow, ice, heat, and parties.
Like most other building stone, Salem Limestone remained a local product during its early decades of use. Not until 1853, when a rail line extended seventy miles south from Louisville, did much stone leave the Belt. By 1870 good railroad connections had been established north to Chicago and east to markets such as Boston and New York, and by the end of the century, train tracks snaked across the Belt, pushing in or near to dozens of quarries.
Early Salem quarries were primitive—meaning human powered— and dangerous workplaces. After locating an exposed face, men first had to pick and shovel the overburden, some of which was soil and some of which was inferior rock called “bastard stone.” The men removed the overburden in wheelbarrows and carts, which gave them a ledge to work. To get good stone out, they cut a dozen ten- to twenty-foot-deep vertical holes with hand drills down into the wall of stone, which could take months; shoved in black powder; and blasted out massive blocks. A single explosion could provide a year’s worth of work, if the block didn’t shatter into too many pieces upon detonation.
By the end of the Civil War, machines had replaced manpower. First to arrive were the multibladed gang saws. They replaced the single-blade crosscut saw, which required two men to cut through a block, as if it were a piece of wood. The mechanical gang saws needed only one man, who fed water and sand that were ground into the blocks by the metal blades, enabling him to cut multiple slabs at one time.
Much more important to quarrymen was the development of the steam channeler, which looked and worked like a cross between a sewing machine and a small-scale locomotive. The cutting tool consisted of five steel bars, each tapered at one end to a sharp chisel edge. Steel bands held the bars together in a row, so that from the side the bar ends looked like fingers of a hand.7 Steam power drove the sharpened bars into the limestone at up to 150 strokes per minute.8 Creeping along a set of tracks the channeler took two days to chisel a 7-foot-deep by 50-foot-long by 13/4-inch-wide cut.9
Much safer than blasting, channelers also reduced waste and cost between one-sixth and one-eighth as much as hand tools. Channelers made men more efficient, too, with two men now able to do the work formerly done by twenty-five, which made the quarry owners happy.10 They could pay the workers the same rate, get more work out of them, and make more money. But the unremitting pounding of steel on stone made men deaf, and the coal-powered channelers produced smoke “thicker than hell,” as one quarryman recalled.
“Everything was done with hand signals in the quarries,” said George Jones, general manager of Indiana Limestone Company (ILCO).11 We were standing on the edge of the company’s massive quarry north of the small town of Oolitic and watching men quarry stone about two hundred feet away. “I knew this one guy who had worked the Reed Quarry. He was in the hospital with cancer and couldn’t
talk. His family communicated with him by hand signals,” said Jones. As we watched, he said that two of the guys below just told each other that they would turn the cut in eight minutes. They did.
Because removing the overburden was expensive and time consuming, quarries generally did not grow horizontally; why remove waste when you could cut down and use all the rock you cut? Vertical cutting, however, led to a small challenge. During channeling, quarrymen typically cut their 13.4-inch-wide grooves from one end of the quarry to the other and across in a perpendicular pattern, so that the ground looked like sliced, rectangular brownies in a pan. How then to remove the first piece, which would let the quarrymen access the surrounding material? Simply modify Mr. Tarbox’s method and pound wedges into the channel on the long side of a block until it snapped at its base. This key block may not have broken cleanly, but the quarrymen could drill into the snapped block’s upper edges, attach hooks, also known as dogs, and lift it out with the derrick, now also powered by steam.
Into the hole created by the removal of the key block, or more often key blocks, men took the next great power tool, the steam drill. They cut horizontal holes every six inches at the long base of an adjoining block, inserted more wedges, and pounded the wedges with a hammer until the block separated from the rock below. Hookers then attached dogs to the massive block, which could be four feet wide by seven feet high by thirty or forty feet long, and pulled, or turned, it onto its side with ropes attached to the derrick. Another set of guys split the now horizontal block into smaller pieces with more holes, more wedges, and more pounding. Finally, hookers attached the block to the derrick and everyone hoped the block wouldn’t fall and crush them.
Stories in Stone Page 15
