M.S. (Master of Science)
Department of Geology
Foraminifera; Fossil--Indian Ocean; Paleontology--Indian Ocean--Eocene
Site 267 was one of five sites drilled during phase 2 of DSDP Leg 28. This phase investigated the development of Antarctic oceanology through the Tertiary. Less than 0.5 m of chalk of Late Eocene age was recovered in Core 10 of the third hole, Hole 267B, drilled at Site 267. This thin chalk unit, immediately overlying the basaltic basement, yielded a diverse foraminiferal fauna. The foraminiferal assemblage is a modified biocoenosis containing large planktonic and benthic faunas. The planktonic fauna is a high diversity-low dominance fauna comprising twenty species. The dominance- diversity relationship indicates the planktonic assemblage originated in temperate surface waters. The presence of the temperate taxon Globigerina angiporoides (Hornibrook) and the absence of any tropical taxa support that conclusion. The benthic assemblage is a high dominance fauna with very high diversity (Over 60 species) . The benthic assemblage, which consists mainly of calcareous benthic taxa, is typical of faunas of lower bathyal depths. The dominant taxon, Globocassidulina subqlobosa (Brady), is common in deep water assemblages throughout the Tertiary and in Recent faunas as well. Most other taxa present are also present in Miocene to Recent deep-water assemblages. Few exclusively Paleogene taxa are present. The benthic fauna is relatively stable in abundance, preservation, dominance and diversity throughout the section studied. This stability probably indicates that relatively stable bottom conditions prevailed throughout the period of deposition. The planktonic fauna, on the other hand, decreases in abundance down hole and exhibits changes in dominance, diversity and preservation. The proportion of fragmented planktonic tests increases greatly as the contact with the basalt is approached. Whole planktonic tests are well preserved in the upper intervals, but in the lower intervals tests are etched and show other signs of dissolution. Such dissolution is generally attributed to syndepositional dissolution while the tests settle through the water column. Unfortunately, present paleoecologic and tectonic theory regarding Eocene conditions in the area does not support syndepositional dissolution in this instance. Examination of dominance-diversity relationships among the ten dominant planktonic taxa reveals that certain taxa are selectively removed from the assemblage while others increase in relative dominance. Such selective changes in relative dominance have been associated with diagenesis, but they usually occur over tens or hundreds of meters. Several mechanisms are possible for this compression of diagenetic effects. One of the most interesting of these possible mechanisms is heat flow from the underlying basalt, which biostratigraphic evidence indicates was extruded within two million years of the initiation of sedimentation. Other possible mechanisms are fluid flow along the basement-sediment contact or abrasion during slumping of unconsolidated sediment.
Styzen, Michael J., "Late Eocene foraminiferal systematics, biostratigraphy and paleoecology of DSDP Hole 267B, Southeast Indian Ocean" (1980). Graduate Research Theses & Dissertations. 3761.
vi, 167 pages
Northern Illinois University
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