Figure F4. A scanned image of thin sections from the OAE1a interval in Hole 1207B. Prior to thin section preparation, billets were impregnated with blue-dyed epoxy. Encasing epoxy is darker blue, whereas the shade of blue within the rock sample is a function of the relative percentage of microporosity. Some samples are highly porous (e.g., nannofossil chalk in Sample 198-1207B-44R-2, 15 cm) whereas others are nonporous (e.g., partly chertified calcareous porcellanite in Sample 198-1207B-44R-2, 1 cm, and brown organic-rich shales). Contacts between nonporous and porous lithologies within the thin section are emphasized (e.g., Sample 198-1207B-44R-1, 114 cm). In some instances these porosity contrasts define burrows (e.g., Samples 198-1207B-44R-1, 47 cm, and 44R-1, 54 cm). Lighter areas in the brown organic-rich samples (Samples 198-1207B-44R-1, 62 cm, 44R-1, 74 cm, and 44R-1, 96 cm) are clay or porcellanite. Note gradational contact in Sample 198-1207B-44R-1, 96 cm (lighter on top).

Figure F4. A scanned image of thin sections from the OAE1a interval in Hole 1207B. Prior to thin section preparation, billets were impregnated with blue-dyed epoxy. Encasing epoxy is darker blue, whereas the shade of blue within the rock sample is a function of the relative percentage of microporosity. Some samples are highly porous (e.g., nannofossil chalk in Sample 198-1207B-44R-2, 15 cm) whereas others are nonporous (e.g., partly chertified calcareous porcellanite in Sample 198-1207B-44R-2, 1 cm, and brown organic-rich shales). Contacts between nonporous and porous lithologies within the thin section are emphasized (e.g., Sample 198-1207B-44R-1, 114 cm). In some instances these porosity contrasts define burrows (e.g., Samples 198-1207B-44R-1, 47 cm, and 44R-1, 54 cm). Lighter areas in the brown organic-rich samples (Samples 198-1207B-44R-1, 62 cm, 44R-1, 74 cm, and 44R-1, 96 cm) are clay or porcellanite. Note gradational contact in Sample 198-1207B-44R-1, 96 cm (lighter on top).