Results of onshore methane analyses and comparison with shipboard data from Geoservices. Methane determined by (A) the QMS (C1-QMS; red dots) and by GC (C1-GC, black triangles) compared with shipboard methane data from Geoservices (C1-Geo; blue squares and line). Please be aware of the different scales of the individual x-axis at the bottom and at the top. B: Lithological column, modified from . “Underreamer depth” denotes the position of borehole widening and potential additional gas release caused by the underreamer. Borehole widening took place around 40 m above the borehole depth. See Methods section.