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Eight sites were drilled on Leg 22 in the northeastern Indian Ocean. Three sites (214, 216, 217) on Ninetyeast Ridge penetrated a thick sequence of mostly Tertiary calcareous oozes passing down into shallow-water sediments with volcanogenic material in Sites 214 and 216. The age of the basal sequence increases northwards from Paleocene (214) through Maastrichtian (216) to Campanian (217). A nonmarine sequence of volcaniclastics and lignite overlies basalt at 214. Drilling terminated in a dolomite chert sequence at 217 before basalt was encountered. Two sites (213, 215), in deep water on either side of Ninetyeast Ridge, showed calcareous ooze of Paleocene to early Eocene age overlying basalt passing up into brown clay and finally siliceous ooze of late Miocene and younger age. A major hiatus centered in the Oligocene occurs at both these sites. One site (212), drilled in the deepest part of the Wharton Basin, penetrated a brown clay sequence interbedded with several thick calcareous units, each of a very short time duration. Evidence from sedimentary structures and calcareous microfossils indicate that these calcareous sediments deposited below the calcium carbonate compensation depth (CCD) have been reworked from shallower water. The age of basement at Site 212 is estimated at about 90 to 100 m.y. Site 211, situated in the northern part of the Wharton Basin, recovered Campanian calcareous ooze overlying basalt. An undated brown clay sequence lies between the calcareous ooze and a thick Pliocene section of terrigenous sediments, representing the distal portion of the Nicobar Fan. Siliceous ooze with some rhyolitic ash beds, presumably derived from the Indonesian volcanic arc, indicate cessation of terrigenous sedimentation here since the late Pliocene. Similar ash beds were also seen in Pleistocene sediments at Site 216. Site 218 was drilled in the central portion of the Bengal Fan, which here comprises a thick sequence of terrigenous sediments at least as old as middle Miocene. Variations in sand-silt-clay ratios coupled with the occurrence of interbeds of calcareous ooze in places indicate four major pulses of terrigenous sedimentation. Two thin beds of terrigenous sediments penetrated at Site 215 show that the distal portion of the Bengal Fan reached as far as 8 S in the late Miocene. Introduction General Source of Data Review of Main Results Site Summaries Regional Patterns of Sedimentation Distribution of Components and Structures Calcareous Nannofossils Foraminifera Other Calcareous Fossils Siliceous Fossils CONTENTS 718 718 718 718 718 723 725 725 726 729 729 Clay Minerals Detrital Minerals Zeolites Manganese Iron Oxides Glauconite Sedimentary Structures Major Sedimentary Facies Calcareous Ooze Siliceous Oozes Terrigenous Sediments 729 731 733 737 737 737 737 739 739 742 743

Sedimentology and History of the Northeastern Indian Ocean from Late Cretaceous to Recent