Fossils provide us with physical proof that there was life before humans. Fossils can provide information about what lived in the past, their environment (in comparison to its current counterpart), and they can be used as time indicators. The properties of fossils help us construct the “history of a continent”. It has been presumed that organic matter cannot survive fossilization, which is the process of geologically recording organic remains. Not all organisms meet the prerequisites for fossilization. Hardness of body parts, the environment, and predators can influence the process of fossilization. Most organisms that are well preserved are buried quickly, protecting them from the environment and depriving them of oxygen to limit the extent of the decay.
The belief that organic matter cannot survive fossilization has been challenged. Fossils have been discovered in Midwest America (Ohio, Indiana, and Iowa) of crinoids, or “sea-lilies”, in immaculate condition and dated back 350 million years, that contain the organisms’ original organic matter. This pristine condition of the crinoid fossils was possible because of the geography of the flat, vast plains of the Midwest that were unchanged by mountains or volcanism. The fossilized crinoids dated back to the carboniferous period (359 – 299 million years ago), a time when an inland ocean spanned the Midwest. According to Ohio State University geologists, the storms that occurred during this time rapidly buried the crinoids in many layers of fine sediments under the water, catalyzing fossilization.
Crinoids are composed of a porous calcite skeleton covered in living tissue. When the organism perishes, its tissue decays and calcite precipitates into the pores. Some organic matter that has not entirely decayed could become sealed in the pores by calcite, creating a “tomb” that is ideal for preservation. A professor in the School of Earth Sciences at Ohio State explained that the molecules in the organic matter found in the fossils, called biomarkers, are similar to quinones, which sometimes function as pigments or toxins. Interestingly, the crinoids had fossilized in different colors: blue-gray, dark gray, and white. The organic molecules were examined by a gas chromatograph mass spectrometer, which separates the molecules by electric charge and mass, and identified as molecules similar to quinones. The ancient quinone-like molecules were compared to those of the crinoids of today, showing that they occur in both specimens.
The next objective is to identify the exact quinone molecule in the crinoid fossils to then be able to determine what kind and how much information can be acquired about the individual species. The data we can derive from fossils is limited by technology. People noticed the color differences in the crinoids 100 years ago but the necessary technology was not available to analyze their composition. I can only imagine the discoveries that will be possible in the future with even more advanced technology.
Posted by Jessica Westover (3)