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Crystal Bridges is open Wed. through Mon. Reserve your free, timed tickets.

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Founder's Tour


Ms. Jacob Franks

Mrs. Jacob Franks (Abigaill Levy)

Attributed to Gerardus Duyckinck I (1695 - 1746)
ca. 1735
45 1/4 x 35 13/16 in. (114.9 x 91 cm)
Oil on canvas
Crystal Bridges Museum of American Art, Bentonville, Arkansas, 2005.8

Audio Transcription

The limestone on Crystal Bridges’ Rock Ledge Trail was formed many millions of years ago on the floor of a warm, shallow sea. The calcium exoskeletons of sea creatures such as crinoids and bryozoans sank to the bottom where they were crushed, compacted, and fossilized into stone over time. When ground water mixed with carbon dioxide enters through cracks in the limestone, the acidic solution gradually dissolves the stone, widening the cracks to eventually form the caves and crevices common to the Ozark landscape. Specimen from the UA Museum Collections.

DR. VAN BRAHANA: The limestone itself was deposited in a shallow marine environment. That's an oceanic environment. We look at the actual preservation of the fossils that are found inside the rock, and that allows us to see that these are animals that only live in the ocean, historically, and for other reasons, maybe five feet deep, nowhere generally greater than 10 to 15 feet deep water. And the result is that we've got multiple sources of material that has been deposited, but the limestones themselves are made up mostly of animal shells and organisms that are associated with these.

The types of fossils are also indicative of how much energy is in the system—was this like a coastline? And for the most part, it's a shallow inland sea. And that kind of information is determined from, basically, it comes from the fact that the shells are not destroyed or they're not rounded or they're not nicked up very much. They're essentially just as they existed in life, but they've turned from a shell into an actual rock. And that's what the fossilization process is about.