| Summary: | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. Includes bibliographical references. Issued also on microfiche from Lange Micrographics. Moderately well-preserved coccoliths are present in late Neogene to Quaternary sediments recovered during DSDP Leg 94 and ODP Leg 108 in the North Atlantic Ocean. 'They were examined to recognize coccoliths response to the late Neogene glaciation in the North Atlantic Ocean. Even though the two study sites cover different time spans and geographic localities, the diversity of coccolithophores shows very few differences in assemblages. For biometric study of the late Neogene coccoliths, four parameters of reticulofenestrids were measured and related to the environmental factors and changes. A very small size of the reticulofenestrid maximum inner diameter represents cooler water (Backman and Hermelin, 1986), and in this study results from measurements of this parameter suggest response of reticulofenestrids to cooler water during times of glaciations at both sites in North Atlantic Ocean. The size of maximum outer diameter of living coccolithophores is closely related to the temperature; coccoliths usually become larger when temperature is higher (Watabe and Wilbur, 1966). Maximum outer diameter values of reticulofenestrids from the study sites vary between sites and through time. The largest individual values of reticulofenestrid maximum outer diameter from Site 664 occur between 2.4 and 2.6 Ma, during a glacial period; however these sizes may have been affected by reworking. Decrease in water temperature is supported by the occurrence in Site 664 of Coccolithus petagicus. This coccolithophore species now occurs mostly in cool waters of high latitude Atlantic Ocean; its occurrence at equatorial sites during the late Pliocene is explained by the lower surface water temperatures. Based on the results of reticulofenestrid measurements the following interpretation of the North Atlantic environmental changes are inferred: a decrease of surface water temperatures occurred during the Pliocene/Pleistocene in the North Atlantic and was connected with formation of North Atlantic Deep Water.
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