Analysis of Mn deposits from Galicia Bank Leg 47

This report deals with results of the first stage of a complex study of the predominantly Lower Cretaceous sediments cored at Site 398 at depths from 945 to 1740 meters. The section studied is overlain by 35 meters of Cenomanian sediments, which are similar lithologically to the underlying sequence. In the upper part (Unit 3) a major rock-forming carbonate mineral is present in much of the section as calcite, often with distinct structural features indicative of a biogenic origin (nannofossils, skeletal detritus) and diagenetic recrystallization. Unit 3 is characterized by abundant authigenic minerals represented mainly by siderite and manganese-bearing carbonate minerals.