Biostratigraphy and Isotopic Paleotemperature of some Deep-Sea Cores from the Indian Ocean

• Main Author: Oba Tadamichi
• Format: Report
• Language: English
• Published: Tohoku University 1969
• Subjects: Indian; Pacific; Planktonic foraminifera
• Online Access: http://hdl.handle.net/10097/28809; https://tohoku.repo.nii.ac.jp/?action=repository_uri&item_id=12006; https://tohoku.repo.nii.ac.jp/?action=repository_action_common_download&item_id=12006&item_no=1&attribute_id=18&file_no=1

Of the six deep-sea cores obtained from the central equatorial Indian Ocean along Long. 78°E. from Lat. 6°N. to Lat. 2°S., the northern three cores are composed of Globigerina ooze and calcareous clay and the other cores from 4,700-4,800 m in depth are of brown clay with some layers of secondary deposited sediments. Paleotemperature curves of the northern three cores based on the oxygen isotopic method showed two temperature oscillations with an amplitude of about 6℃. and resemble closely those of the many deep-sea cores from the Atlantic, Pacific and Caribbean Sea measured by Emiliani (1955, -1967) and Rosholt et al. (1961, 1962). The late Pleistocene chronology since the Mindel-Riss interglacial was considered on the basis of the paleotemperature curves, radiocarbon dates, and rate of sedimentation measured by the Io/Th method. Planktonic foraminiferal number in the sediments decreases generally with increasing depth. The coarser fractions larger than 74μ and calcium carbonate percentage in the sediment are proportional to the planktonic foraminiferal number, and are larger during the glacial stage than during the interglacial stage. Analysis of the planktonic Foraminifera of the cores showed that the fluctuation curves of the warm water fauna coincides roughly with the paleotemperature curves gained by the oxygen isotopic method. The planktonic Foraminifera in the cores obtained from relatively deep water are almost broken and the few perfect specimens are those of the species with thick shelled test. The rate of dissolution of the test was estimated from the damaged test of Globorotalia menardii, and the results were in good agreement with the percentage of the benthonic Foraminifera. The agreement is not due to the increase of benthonic Foraminifera but to the decreased number of specimens of the planktonic ones. The dissolution effect of the test was also found in the cores obtained from relatively shallow water. Factor analysis of the planktonic foraminiferal assemblages in the cores revealed the mutual ...