This data set presents contents of the clay minerals smectite, illite, chlorite and kaolinite analysed on the clay fraction (<2 micrometer) of seafloor surface sediments. The sediments were recovered with a mega-corer (MC), box corer (BC), kasten corer (KC) or jumbo gravity corer (JGC) on the Amundsen Sea continental shelf in the vicinity of Thwaites Glacier and Pine Island Glacier. Sediment cores were collected during cruises NBP1902 (Jan-Mar 2019) and NBP2002 (Jan-Mar 2020) with RV/IB Nathaniel B. Palmer as part of the Thwaites Offshore Research (THOR) project on behalf of the International Thwaites Glacier Collaboration (ITGC) programme. The clay mineral contents are given in percentages and subbottom depth in centimetres (cm).

NERC grant NE/S006664/1 and NSFPLR grant no. 1738942. This data was collected as part of the NERC-NSF funded International Thwaites Glacier Collaboration (ITGC) program.