Category: StreetSmartNaturalist

The Unconformity at Yankee Stadium

Recently there has been much bother and brouhaha about the opening of the new stadium for the New York Yankees. The New Yorker’s fine architectural critic Paul Goldberger wrote that the building has “the self important air of a new courthouse built to look as if it had been there since William Howard Taft was President.” Perhaps of more importance, at least to some, Goldberger noted that the stadium “finally [has] sufficient bathroom facilities.” He discussed sight lines, historic homages, and luxury boxes, but what he failed to notice is the unconformity that greets all who enter.

Up close with the Yankees’ unconformity (from Wikipedia)

The base of the stadium is a gray, lightly lavender granite quarried from Crotch Island, Maine. Sitting atop it is the Salem Limestone, quarried in Bedford, Indiana, just around the corner from the hole that provided the stone for the Empire State Building. The missing time gap is about 40 million years, a relatively short span considering what could occur in architectural unconformities. (One of my favorites is the three-billion-year gap between the formation of the Morton Gneiss and the deposition of the Kasota Limestone, the two rocks abutting each other on the Art Deco Qwest Building on Minneapolis.)

Such geologic incongruities are common in architecture. Half-billion-year old slates butt against 150,000-year-old travertines. Sandstone that formed in Connecticut sits on top of marble that formed in Italy. Metamorphic rocks interfinger with sedimentary rocks. Fossil-rich, sea-deposited limestones juxtapose mineral-rich, subduction-created granites. The collection of building stones in any downtown area is as complex as any assembled by plate tectonics.

But back to the rock of Yankee stadium. Since the middle 1800s, Maine has been a major source of granite in the building industry. By 1889, Maine had 153 granite quarries, including one in Vinalhaven that employed 1,500 people. Quarries combined good, hard rock with easy transportation. Most of the important quarries were on the islands on the south central coast. Maine granite went into structures throughout the eastern seaboard, such as the Brooklyn Bridge, the U.S. Treasury Building in Washington, D.C., and Boston’s Harvard Bridge. Now, however, only one island quarry remains, the one on Crotch Island, owned by the Deer Isle Granite Company. (If you want to own the same rock as the Yankees, they’ll be happy to sell you some.)

Deer Isle granite items for sale from Deer Isle Granite Company

The Deer Isle granite solidified about 371 million years ago, as part of an extensive array of granites that formed during two periods of extension associated with the Acadian Orogeny. The rock on Crotch Island sat at the top of the magma chamber. Unlike other granites within the Deer Isle complex, the Crotch Island has few enclaves and no hornblende. It is one of the lighter colored of Maine’s granites, as well, due mostly to buoyant silicic minerals getting concentrated near the roof of the chamber.

Forty million years after the formation of the Deer Isle rock, a quiet sea covered much of the central part of North America. The hundreds of feet of limestone that developed from the mid-continental sea have been exploited widely as quarries, none more famous than those in and around Bloomington and Bedford, Indiana. The Salem Limestone, often called the Indiana limestone, basically consists of the broken up shells of billions upon billions of marine invertebrates, primarily crinoids, forams, bryozoans, and brachiopods. As I have noted before, it is the most commonly used building stone in America.

Now, I have to admit I am not a Yankees fan. Nor, am I a fan of any baseball team but next time I am in New York, I think I would go out to the ballpark. I wouldn’t actually go to see a game, and if no one was there that would be even better, but I would like to see the unconformity.

Cambrian Life in Wisconsin

As I have noted earlier in regard to the footprints in Mexico and the basalt in India, quarries often open up windows into stone that help geologists better understand the world. One of those revelatory quarries is found in Wisconsin, about 200 miles northwest of Milwaukee, where paleontologists found a beach-load of jellyfishes that died 510 million years ago. Each jellyfish resembles an aerial shot of a crater with a slightly raised center, the bell of a jellyfish, surrounded by a concave ring that ends in a prominent rim. The biggest are up to 70 centimeters in diameter.

Fossils from Wisconsin. Fossil D=70cm. From Geology Feb. 2002.

Fossil dealer Dan Damrow discovered the jellyfish in 1998 and four years later co-wrote an article (Geology, February 2002) describing the animals with paleontologist James Hagadorn. Technically known as medusae, the jellyfish were pelagic carnivores that moved into the littoral zone to hunt but a receding tide could trap the animals in great masses on the beach. As the tide ebbed and returned, fine-grained sediment covered the jellyfish, preserving the rarely preserved soft tissues. Ripple marks surround and in a few cases pass through the fossils. Damrow and Hagadorn report that the fossils were found in seven, flat-lying beds, which covered perhaps a million years of time, and that they provide new insights into the Cambrian.

The Krukowski family own the quarries and sell the fossiliferous rock under the trade names Highland Brown Antique, Sandy Creek and a sawn version called Cambrian Cream. Uses include architectural veneer stone, thin veneers, outcropping, steps, flagstone, and landscape retaining walls. The sawn version is transferred into countertop slabs, cladding, flooring and a variety of architectural and landscaping products. Because no one had recognized the fossils until the Damrow saw them, many people could have the fossils in their homes without knowing it.

Climactichnites (from Wikipedia)
Paleontologists have also found another unusual fossil at the Krukowski site. Known as Climactichnites, the fossils resemble tire tracks and have been described as both trace fossils and body impressions of a gelatinous zooplankter. More recently, a graduate student of Hagadorn’s has reexamined the traces from Wisconsin and other sites, and interpreted them as gastropod tracks, possibly from some of the earliest terrestrial animals. Apparently life in the Cambrian in what became Wisconsin was rather interesting.