THE USE OF TERNARY DIAGRAMS IN RARE EARTH ELEMENT (REE) ANALYSIS OF FOSSILS AND INTERPRETATION OF THE ORIGINAL PALEOENVIRONMENT

Rare Earth Elements (REE) analysis on fossil bones has recently been used to interpret reworking, time averaging, and fossil provenience. Data have been displayed in NASC normalized spider diagrams. The REE patterns define a "signature" for each of the studied specimens. These signatures can be interpreted as "fingerprints" for stratigraphic units. REE signatures reflect the original waters of deposition and therefore can be used for paleoenvironmental interpretation. A better method for visualizing variations in REE patterns is by use of a ternary diagram. Representative Light (LREE), Middle (MREE) and Heavy (HREE) rare earths occupy the vertices of the triangle. We use Pr or Nd, Gd, and Yb as the representative end members. The ternary diagram allows the basic shape of the REE pattern to be represented by a single point. Mixing lines between environmental end members may be shown in such diagrams. These ternary diagrams can be compared with natural waters to infer the original water conditions. Examples of mixing as a function of stratigraphic level in the Cretaceous Pierre Shale of South Dakota and the Pleistocene of Fossil Lake, Oregon, will be presented.