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Illinois IGB

Core Facilities

Core: Image of the Month

  • December 2015

    Reef-building corals continuously deposit calcium carbonate under the form of aragonite, forming skeletal growth bands of varying density as they are precipitated under different environmental conditions. Therefore, the coral skeleton potentially represents a long-term record of the environmental conditions at the time of the skeletal deposition. This has resulted in corals being utilized in many paleothermometry studies to reconstruct historical sea surface temperatures.  

    Coral skeleton density banding (CSDB) patterns, as revealed by standard X-radiography (XRD), provides the fundamental spatial and temporal framework in which O-isotope paleothermometry is completed for the reconstruction of sea surface temperature (SST). Accuracy in these historical SST estimates requires that mechanisms controlling the thickness, frequency and density of CSDB deposition are well understood. However, many aspects remain unknown, including whether CSDB is consistent within individual coral heads, as well as how many high-density bands (HDB) and low-density bands (LDB) are formed seasonally.

    Image analyses applied to the 5 mm-thick billet 2 from the O. annularis coral head. Photograph (P) of coral billet. Original XRD image of coral billet. CLAHE (CLH) image of coral billet. Matrix kernel vertical (MKv) and horizontal (MKh) images of coral billet. Fast Fourier transform vertical (FFTv) and horizontal (FFTh) images of coral billet. Average intensities are derived from measurement of a 19.2 mm-wide (120 pixel-wide) swath centered along the length of each billet image. Intensities are normalized and arbitrary.