Cores from the eastern part of the area bounded by the Kane and Atlantis fracture zones, in the NE Atlantic Ocean, have been studied for their mineralogical, biostratigraphical and radio-chronological characteristics. Two of them contain a systematic association of pure palygorskite layers with ferro-manganese oxide concretions, alternating with normal carbonaceous sedimentation. Another contains manganese nodules having a nucleus of palygorskite. The possible origins of the palygorskite are discussed, and it is concluded that it is of hydrothermal origin. The close association of the palygorskite with the Fe-Mn concretions suggests a hydrothermal origin for these too. The episodic character of the deposits shows that hydrothermal activity occurred during relatively short periods, and that the last episode probably took place less than 100,000 years ago.