Of the three wells drilled in Canada's Arctic Islands, one at Winter Harbour in the Parry Islands encountered 2,000 feet of the (?)Ibbett Bay Formation. Core from interval 9790 to 9811 feet comprises finely laminated calcareous shales and limestones, a little silicified. Nodular forms of micritic limestone, with an occasional rind of silica, show horizontal bedding extending into adjacent shales, where abrupt thinning indicates compaction. Above and below each nodule, the compacted shales bend around it. In other parts of the core compaction is due to lateral variation in percentage of CaCO 3 ; the more calcitic nodules were cemented early enough to resist compaction. Sutured stylolites, most of them vertically oriented in thin laminations in argillaceous limestone, suggest post-compaction and lithification associated with the tectonic folding.