Date of Award

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geology and Geophysics

First Advisor

Barun K. Sen Gupta

Abstract

This study focuses on Quaternary benthic foraminiferal distribution in the Ross Sea, and its relationship to oceanography and ice-shelf retreat. It is the first study of benthic foraminiferal distribution that takes the retreat history of the Ross Ice Shelf into account. This is also the first time foraminifera from a cold-water carbonate bank have been described. There are three foraminiferal faunas in the Ross Sea: Pleistocene carbonate-bank fauna, Modern-calcareous fauna, and Holocene agglutinated fauna. Numerically significant species in the carbonate-bank and Modern-calcareous faunas include Angulogerina earlandi, Cibicides lobatulus, Discorbis vilardeboana, Ehrenbergina glabra, Epistominella exigua, and Globocassidulina crassa . The carbonate-bank fauna has higher diversity and greater numerical abundance than the Modern-calcareous fauna. The agglutinated fauna, which is seen in Holocene sediments, contains Bathysiphon sp. A, Hormosinella ovicula, Miliammina earlandi, Textularia wiesneri, and Trochammina quadricamerata. The Modern-calcareous fauna is found where Warm Core Water upwells into the photic zone, causing an increase in phytoplankton productivity. The agglutinated fauna is found in water depths below the CCD and where Warm Core Water does not upwell in the photic zone. The carbonate-bank fauna probably formed during a period of increased upwelling in the northwestern Ross Sea. The utility of benthic foraminifera as a tool for distinguishing glacial environments is also tested. Ice-shelf proximal and distal environments could not be distinguished by benthic foraminiferal assemblages, which contained the agglutinated species Miliammina earlandi, reworked calcareous forms, and rare other agglutinated specimens. In addition, some samples with an abundant agglutinated assemblage were found in an open-water environment. This research also included a brief study of the distribution and formation of concentrically layered opaline spherules found in Antarctic sediments. These tiny spherules are found in association with calcareous foraminifera in the Ross and Weddell Seas and appear to form through precipitation as seasonal sea ice melts, causing freshwater to mix with saltwater, thus decreasing silica solubility in surface waters.

ISBN

9780599474628

Pages

358

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