Ages, lithologie descriptions and mineral analyses from different DSDP holes in the Indian Ocean

The present work is based on mineralogical studies of sand and silt layers from a number of Deep Sea Drilling Project sites in the Indian Ocean belonging to different physiographic provinces of different ages. The minerals can be grouped into two major associations: a hornblende-opaque association with varying amounts of pyroxene, garnet, epidote, zircon, etc. and a biotite-chlorite-muscovite assemblage. The dominance of unstable minerals indicates a first generation, though evidence of reworking is reflected in the zircon and tourmaline grains at some sites. A large variety of minerals at some sites indicates a complex source. The mineral composition is nearly homogeneous at different sites for the entire length of the core, indicating that they have been derived from the same source during the deposition of that interval. However, the provenance changed by tectonic activity, the effect of which has been reflected in the mineralogy of some sites. An attempt was made to describe the mineralogic characteristics and their tectonic interpretations in the Pliocene and Miocene periods in the Ganges and Indus fan sites and also in the Wharton and Mozambique basin sites. Similar attempts could not be made for other ages in other physiographic provinces as the numbers of samples were too few. Within the limited scope, some idea about the mineralogical character of different basins and different physiographic provinces can be obtained from the present study. Mineralogical evidence also suggests very long transport of sediments in the deep sea. Regional variation of mineralogy has resulted due to source, sea-floor configuration, selective removal, reworking by different agencies and the processes operating in the ocean. There is no relation between a particular age and a set mineral assemblage for the Cenozoic sediments of the Indian Ocean.

Chemical composition and K-Ar age of basalts from the floor of the Indian Ocean

Petrographic description as well as data on chemical composition and K-Ar age of basalts from the floor of the Indian Ocean are reported in the paper.

Chemical composition of ultrabasite and gabbro from the rift zones of the Arabian-Indian and Western Indian ridges

Results of petrographic studies of ultrabasite and gabbro from the rift zones of the Indian Ocean ridges are discussed using materials of R/V Vityaz Cruise 36. Rocks sampled from two sites 2700 km apart are close to each other in their composition. Petrographically ultrabasic rocks are divided into four subgroups: I - dunite; II - harzburgite, serpentinite; III - plagioclase lherzolite; and IV - metamorphically altered rocks. Petrographic description and chemical composition of basic rock varieties are presented as well as description of rock-forming minerals and their optical properties. Formation of pyroxene and plagioclase is shown to be related to autometasomatosis, which concludes the magmatic phase proper in rock mass formation accompanied by activity of residual intragranular liquid. Formation of ultrabasite in the rift zones is related to complicated processes.

Cenozoic record of continental mineral deposit on Broken and Ninetyeast Ridges, Indian Ocean

The mineral component of pelagic sediments recovered from the Indian Ocean provides both a history of eolian deposition related to climatic changes in southern Africa and a record of terrigenous input related to sediment delivery from the Himalayas. A composite Cenozoic dust flux record from four sites in the central Indian Ocean is used to define the evolution of the Kalahari and Namib desert source regions. The overall record of dust input is one of very low flux for much of the Cenozoic indicating a long history of climate stability and regional hyperaridity. The most significant reduction in dust flux occurred near the Paleocene/Eocene boundary and is interpreted as a shift from semiarid climates during the Paleocene to more arid conditions in the early Eocene. Further aridification is recorded as stepwise reductions in the input of dust material which occur from about 35 to 40 Ma, 27 to 32 Ma, and 13 to 15 Ma and correlate to significant enrichments in benthic foraminifer delta18O values. The mineral flux in sediments from the northern Indian Ocean, site 758, records changes in the terrigenous input apparently related to the erosion of the Himalayas and indicates a rapid late Cenozoic uplift history. Three major pulses of increased terrigeneous sediment flux are inferred from the depositional record. The initial increase began at about 9.5 Ma and continued for roughly 1.0 million years. A second pulse with approximately the same magnitude occurred from about 7.0 to 5.6 Ma. The largest pulse of enhanced terrigenous influx occurred during the Pliocene from about 3.9 to 2.0 Ma when average flux values were severalfold greater than at any other time in the Cenozoic.

Chemical composition of rocks from the Eastern Indian Ocean

The monograph presents results of comprehensive geological and geophysical studies carried out in 1973 and 1976 during Cruises 54 and 58 of R/V "Vityaz" in the Eastern Indian Ocean. On the base of obtained data a description of topography, magnetic and gravity fields, structure of the sedimentary series and deep crustal structure of the East Indian Ridge, Central, West Australian and Cocos Basins, the Sunda Trench has been done. Materials on petrography, petrochemistry and geochemistry of igneous rocks in the region have been summarized. New geological and geophysical information has been compared with with DSDP materials. Tectonics and geological history of the Eastern Indian Ocean are under consideration.

Planktological-chemical observation during the International Indian Ocean Expedition (IIOE) with RV "Meteor" in 1964/65

The present volume contains the planktological data collected during the expedition of the "Meteor" to the Indian Ocean in 1964/65. It was the main objective of the expedition to study the up- and downwelling conditioned along the western and eastern coasts of the Arabian Sea by the northeastern monsoon. It is from these areas that the greater part of the data here presented was obtained. A few values from the Red Sea have been added. As the title "Planktological-Chemical Data" implies, it was chiefly with the help of chemical methods that the planktological investigations, with the exception of the particle size analysis and phytoplankton counting conducted optically, were carried out. These investigations were above all devoted to a quantitative survey of particulate matter and plankton, the latter being sampled by water-bottle and net. The zooplankton hauls were taken with the Indian Ocean Standard Net according to the international guidelines laid down for the expedition. As a rule, double catches were made at every station, one sample being intended for laboratory analysis at the Indian Ocean Biological Centre in Ernakulam, South India, and the other for the Institut für Meereskunde in Kiel. In addition to determining the standing stock, the production rate of phytoplankton was measured by the 14C method. These experiments were mainly conducted during the latter half of the expedition. The planktological studies primarily covered the euphotic zone, extending into the underlying water layers up to a depth of 600 m. The investigations were above all directed towards ascertaining the quantity of organic substance, formed by primary production, in its relation to environmental conditions and determining whether or not organic substance is actively transported from the surface into the deeper layers by the periodically migration organisms of the deep scattering layers. Depending on the station time available, a few samples could now and then be taken from deeper layers. The present volume of planktological-chemical data addresses itself to all those concerned processing the extensive material collected during the International Indian Ocean Expedition. As a readily accessible work of reference, it hopes to serve as an aid in the evaluation and interpretation of the expedition results. The complementary ecological data such as temperature, salinity, and oxygen content as well as the figures obtained on abundance and distribution in depth of the nutrients essential for primary production may be found in the volume of physical-chemical data published in Series A of the "Meteor"-Forschungsergebnisse No. 2, 1966 (Dietrich et al., 1966).