49 Processes in Biogeochemistry and Biomineralization (Posters)

Tuesday, 22 March 2016
1:30 PM - 5:30 PM
Convention Hall

CHEMICAL CHARACTERIZATION OF TOOTH TISSUES IN MODERN AND FOSSIL SHARKS: IMPLICATIONS FOR PALEOCEANOGRAPHIC STUDIES IN THE ATLANTIC AND GULF COASTAL PLAINS DURING THE CENOZOIC

Paper number: 49-6
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Tooth tissues from an assemblage of modern and fossil sharks from the Atlantic and Gulf Coasts were analyzed utilizing Fourier transform infrared spectroscopy (FTIR), electron disruptive spectrophotometer (SEM/EDS) and X-ray diffraction (XRD). Modern teeth were collected from sharks captured off the coasts of New Jersey and Florida and included the lamniform Isurus oxyrinchus Rafinesque, 1810 and carcharhiniform Carcharhinus brevipinna (Müller and Henle 1839). Fossil teeth were collected from middle Cenozoic sediments in New Jersey and Alabama and included the lamniform Striatolamia macrota Agassiz, 1843 and carcharhiniform Physogaleus secundus (Winkler, 1876).

Chemical analysis revealed differences between the fluoroapatite Ca5(PO4)F comprising the enameloid and dentine in both modern lamniform and carcharhiniform teeth. We attribute these differences to varying amounts of chemical substitutions of phosphate by carbonate and fluoride by hydroxide in the crystal lattice of the more porous and permeable dentine tooth tissues. These chemical differences were not observed in the fossil lamniform and carcharhiniform teeth. We interpret this to represent groundwater percolation, solutioning and diagenesis in the burial site. This fossilization process, which commonly stains shark teeth, has resulted in uniform recrystallization throughout the enameloid and dentine.

A growing body of literature has identified the potential utility of shark teeth as proxies for chemical paleoceanography. Our results demonstrate the need for careful laboratory cleaning and protocol in order to remove the potentially adverse effects of staining and recrystallization in the burial site. Modern lamniform and carcharhiniform teeth from locations with known ocean temperature and chemistry hold the key to utilizing analogous fossil taxa in reconstructing ancestral seawater chemistry and temperature.

Geological Society of America Abstracts with Programs. Vol. 48, No. 1

doi: 10.1130/abs/2016NE-272731

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