Post-Archaean Average Shale (PAAS) normalized REE profiles for Marcellus Shale outcrop and core samples. a Representative REE profiles of samples from this study exhibiting HREE-, MREE-, and LREE-enrichment. b Averaged, element ratio biplot. Points summarize the averaged, PAAS-normalized, interelement ratios for each sample. The square, diamond, and triangle in (b) correspond to the REE profiles plotted with matching markers in (a) while circles represent all remaining samples. Filled symbols (N = 7) indicate core samples, while open symbols (N = 11) indicate outcrops. The generic order of normalized REE weight ranges (HREE, MREE, LREE) are given in grey (e.g. “H > M>L” in the upper right portion of the plot); see Stolpe et al.  and Noack et al.  for further interpretation.