Annotated record of the detailed examination of Mn deposits from DSDP Site 172, Leg 18 (Cores 172-1, 172-2)

Site 172 was continuously cored to a depth of 24 meters in a sediment pond 140 kilometers south of the Murray fracture zone. The upper 9 meters consist of a moderate brown pelagic clay which changes to a zeolite-rich brown clay, brown clay zeolitite and zeolitite in the lower 9 to 24 meters. An Early Oligocene (35 to 38 my) nannofossil horizon occurs near an extrusive basalt encountered at 24 meters. These sediments are older than the 29 my age indicated by a recent identification of magnetic anomaly 8 in the "disturbed" zone. The age discrepancy suggests that the magnetic anomalies in the "disturbed" zone are still not identified correctly.