How Deep is the Energy Well?

Monday, February 11, 2008

Just when you thought you knew the age of your favorite fossil (give or take a million years), Paul Angiolillo, Ph.D., and Nora Graneto '06, can prove that your mineralized little friend may have misled you – possibly by as much as 100 to 200 million years.

Angiolillo, chair and professor of physics, and Greneto, his former student, recently published an article in Applied Radiation and Isotopes about a technique they developed using electron paramagnetic resonance (EPR) spectroscopy to extend the dating of objects from the paleontologic record – e.g., your fossil.

Titled "Characterization, Stability, and Origin of Natural Radiation-Induced Defects in the Biogenic Calcite of Belemnitella americana from the Upper Cretaceous: An Electron Paramagnetic Resonance Study," the experiments measured the number of spins of inorganic radical species (electrons) that reside in energy traps in the biogenic calcite – a crystal form of calcium carbonate – which are extant in the rostrum of the prehistoric squid Belemintella americana.

The 3-6 inch rostrum – which has been described as a body part resembling a bird's beak – is all that remains of the 65 million-year-old squid. Scientists believe the rostrum acted as a counterbalance for movement. Angiolillo collects fossils as a hobby, and found the rostrum fragments he used for the study in dredge materials from the Chesapeake and Delaware Canal.

Angiolillo and Graneto discovered that the energy traps in the calcite were significantly deeper than previously determined – in other words, this is where your fossil's prevarication comes in. Their technique for determining the extent of the energy trap – which he likens to a well – allowed them to push the dating back, because these particular wells are so deep – and old.

Though he thinks the findings of the experiment are intriguing – they have generated a further study of fossils from the Jurassic Period, which are approximately 200 million years old – Angiolillo says the story of the way the initial study came about is most interesting to him, because it says something about the nature of a Saint Joseph's education.

"Nora was a Summer Scholar in my lab in 2004, looking at organic conducting materials," he said. "During a subsequent Summer Undergraduate Research Fellowship at the National Institute of Standards of Technology, she worked in ionizing radiation labs, using electron spin resonance to study radioactivity. When she returned to my lab that fall, she wanted to use this technique, and even though I wasn't working on spin resonance dating, I went to the literature and tailor-made a project for her."

Angiolillo added, "This was a great opportunity for an undergraduate student to publish meaningful research in a prestigious journal. The close attention and concern for the interests of the students is what makes a Saint Joseph's education distinctive."

Graneto is now working as a nuclear physicist for the energy giant Exelon, and is considering pursuing a graduate degree in physics.

--Patricia Allen

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