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Geological Society, London, Special Publications; 1986; v. 21; p. 205-218;
DOI: 10.1144/GSL.SP.1986.021.01.15
© 1986 Geological Society of London

Neogene Deep and Surface Water Palaeoceanography

Early to Middle Miocene benthic foraminiferal faunas from DSDP Sites 608 and 610, North Atlantic

Ellen Thomas

Scripps Institution of Oceanography, La Jolla, California 92093, USA
Present address: Lamont-Doherty Geological Observatory, Palisades, New York 10964, USA

Benthic foraminifera were studied in lower and middle Miocene cores from DSDP Site 608 (3534 m, 42°50'N., 23°05'W.) and Site 610 (2427 m, 53°13'N., 18°53'W.), north-eastern North Atlantic Ocean. There were extremely high relative abundances of Bolivina spp. between about 19.5 and 17 Ma at both sites. These high abundances were probably caused by oxygen deficiency in the bottom waters, which is suggestive of sluggish circulation.

Some changes in the faunal composition occurred at the beginning of the period of sluggish circulation (20–19 Ma), and between about 15 and 14 Ma, at which time there was a global increase in oxygen isotopic ratios in benthic foraminiferal tests. The changes in faunal composition involved less than 20% of the total fauna. Most first and last appearances of benthic species were not coeval at the two sites. The first appearance of Cibicidoides wuellerstorfi is an exception and occurred at the same time as the middle Miocene increase in oxygen isotopic ratios.





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[Abstract] [PDF]