Figure F12. Close-up photograph of interval 183-1141A-18R-2, 9-19 cm, from the dense interior of basement Unit 4. The groundmass in this interval appears finer grained upon visual inspection of the core, leading to the suggestion that this is a dike. However, the presence of vesicles and the sheet of segregated material, from 13.5 cm on the left to 9.5 cm at the top surface of the core on the right, are more consistent with the massive interior of a thick inflated flow.