Relative abundance of archaeal (domain) sequences (red diamonds) and three featured subclassifications of archaeal taxa. The percentage values were calculated as a proportion of “indigenous” prokaryotic sequences, which excludes eukaryotic, not classified, and nonindigenous bacterial sequences. The black diamond represents the sample from Site C0015. Anaerobic methanotrophic archaea (ANME, orange squares) are classified within the Euryarchaeota phylum, while the MCG/Bathyarchaeota (dark blue circles) and Terrestrial Hot Spring Crenarchaeotic Group (THSCG, light blue circles) are within the Thaumarchaeota. Archaeal sequences were not detected below 16.14 mbsf in this study. The red shaded region corresponds to horizons composed of a hydrothermally altered clay lithology.