A phytoplankton bloom dominated by the pennate diatom Nitzschia curta (Van Heurck) Hasle was observed during January-February 1983 at a receding ice-edge in the Western Ross Sea, Antarctica. The core of the bloom was found between 100-150 Km from the ice-edge. Nitzschia curta cell densities up to 22 x 10⁶ cells/1 were observed. The nanoplankton contributed to 18% (average) of the total biomass. The contribution of another pennate diatom, Nitzschia closterium (Ehrenberg) W. Smith, was significant in two offshore stations (22% and 90%). Other diatom species, dinoflagellates and other phytoplankton groups were very few in number. A wind-driven upwelling event occurred along the ice-edge. The presence of off-shore species (e.g. Nitzschia kerguelensis) close to the ice suggests the existence of an eddy circulation. Results of elemental composition experiments with 10 Antarctic diatoms showed that the C:Si:N ratio for Antarctic diatoms, when compared to the Redfield-Richards ratio for diatoms of other environments, have less carbon and more silicon per unit nitrogen. Comparison of laboratory results with the field data confirms the anomalous elemental composition of the major bloom species observed in the Ross Sea. Blooms like the one observed in this study seem to be restricted to the Western part of the Ross Sea and appear to be produced in inshore waters late in the austral summer. / Graduation date: 1985

Thesis (Ph. D.) -- Lincoln University, 2010. / Also available via the World Wide Web.

Thesis (M.S.)--Indiana University, 2008. / Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Kathy J. Licht, Andrew P. Barth, R. Jeffery Swope, Gabriel M. Filippelli. Includes vitae. Includes bibliographical references (leaves 182-191).

Indiana University-Purdue University Indianapolis (IUPUI) / Petrography of the sand fraction, particle size analysis, and detrital zircon U/Pb isotope data, and pebble count data were collected from Byrd Glacier moraines and central/western Ross Sea till in order to study the glacially-driven sedimentological dynamics of the Byrd Glacier and to trace material transported from the Byrd Glacier into the Ross embayment. Most of the petrographic data show evidence of local derivation with the exception of the sites from the Lonewolf Nunataks as indicated by exotic rock types within the sand and pebble fractions. This, in conjunction with particle-size data of the samples from the Lonewolf Nunataks indicate that material from underneath the East Antarctic Ice Sheet (EAIS) is being transported to the surface and deposited in this area. The U/Pb ages of zircons from the Byrd Glacier show dominant populations of Ross to Pan-African ages (~533 - 610 Ma) with varying populations of older (Grenville to Archean) zircons. Late Precambrian (~588 – 610 Ma) aged detrital zircons in samples from the head of the Byrd Glacier are older than other dated grains found in the vicinity and may be evidence of early development of the Ross belt or represent evidence of sub-glacial extension of the Mozambique structure found in Dronning Maud Land. The west central Ross Sea till samples have a variety of mineral and lithic fragments that include a dominant population of polymict at certain depth intervals. Detrital zircon data suggests the potential provenance of two of these intervals may be derived from Marie Byrd Land and possibly the Byrd Glacier. Using sand petrography and U/Pb detrital zircon age dating, positive correlation was found between specific samples from the head of the Byrd Glacier and the western Ross Sea. The ice-sheet flow models of Stuiver et al. (1981), Licht and Fastook (1998), and Licht et al. (2005) each show potential support from aspects of this study. It is possible that dynamic ice-flow regime changes of the West and East Antarctic Ice Sheets into the Ross Sea may have occurred some time during the LGM as suggested by geochemical and petrographical evidence found within intervals of central and western Ross Sea cores.

Indiana University-Purdue University Indianapolis (IUPUI) / U/Pb and (U-Th)/He (ZHe) dating of detrital zircons from glacial till samples in the Ross Embayment, Antarctica records cooling after the Ross/Pan-African orogeny (450-625 Ma) followed by a mid-Jurassic to mid-Cretaceous heating event in the Beacon basin. Zircons were extracted from till samples from heads of major outlet glaciers in East Antarctica, one sample at the mouth of Scott Glacier, and from beneath three West Antarctic ice streams. The Ross/Pan-African U/Pb population is ubiquitous in these Antarctic tills and many Beacon Supergroup sandstones, thus 83 grains were analyzed for ZHe to subdivide this population. Two ZHe age populations are evident in East Antarctic tills, with 64% of grains 115-200 Ma and 35% between 200-650 Ma. The older population is interpreted to be associated with the Ross/Pan-African orogeny including cooling of the Granite Harbour Intrusives and/or exhumation of the older basement rocks to form the Kukri Peneplain. The lag time between zircon U/Pb, ZHe and 40Ar/39Ar ages from K-bearing minerals show cooling over 200 My. Grains in East Antarctic tills with a ZHe age of 115-200 Ma likely reflects regional heating following the breakup of Gondwana from the Ferrar dolerite intrusions, subsidence within the rift basin, and a higher geothermal gradient. Subsequent cooling and/or exhumation of the Transantarctic Mountains brought grains below the closure temperature over a span of 80 My. This population may also provide a Beacon Supergroup signature as most of the tills with this age are adjacent to nunataks mapped as Beacon Supergroup and contain an abundance of vi Beacon pebbles within the moraine. Nine zircons grains from three Beacon Supergroup sandstones collected from moraines across the Transantarctic Mountains yield ages from 125-180 Ma. West Antarctic tills contain a range of ZHe ages from 75-450 Ma reflecting the diverse provenance of basin fill from East Antarctica and Marie Byrd Land. ZHe and U/Pb ages <105 Ma appear to be distinctive of West Antarctic tills. The combination of U/Pb, ZHe and 40Ar/39Ar analyses demonstrates that these techniques can be used to better constrain the tectonic evolution and cooling of the inaccessible subglacial source terrains beneath the Antarctic Ice Sheet.