18O studies. Presence/absence and features of the benthic component are used to divide the section into six units:
Foraminifers are reported from Ocean Drilling Program (ODP) Leg 188, Sites 1165, 1166, and 1167 in and near Prydz Bay, off East Antarctica. Assemblages are generally sporadic and do little to provide a chronostratigraphic framework for the aims of Leg 188. Dissolution below the carbonate compensation depth (CCD) has been a major factor controlling preservation of some assemblages. Descriptions of each section include reference to the significance of accessory components such as other non-foraminifer microfossils and some minerals.
The composition of the early Miocene and younger assemblages at Site 1165 suggests that they are in situ or are at the depth where they accumulated. The occurrences, apparently in situ, of Globigerina bulloides in Sample 188-1165A-1H-CC and an assemblage (also recorded on southern Kerguelen Plateau) including Globorotalia puncticulata and Globorotalia scitula in Quaternary sediments of Sample 188-1165B-2H-2, 70-75 cm, support the longer range for G. puncticulata and indicate a short interval of warmer-water conditions in the early Pleistocene. Accessory microfossils are important indices in the section. A major change in environment is obvious in Core 188-1165B-25X (middle-late Miocene transition; approximately Chron C5R). Above this level glauconite becomes a regular component of samples, possibly reflecting an influx of reworked material from Paleogene sediments on the nearby Mac. Robertson Shelf. Another change is evident at the base of Core 188-1165B-58X (latest early Miocene; Chron C5Dr) where sponge spicules and orosphaerid radiolarians become regular components, perhaps marking a significant cooling event. These radiolarians disappear uphole at Section 188-1165B-34X-CC within the middle Miocene (Subchron C5Abr-Acr).
Site 1166, although penetrating rocks as old as Cretaceous, yielded foraminifers only from the Neogene. The total benthic assemblage is diverse, but agglutinated species are rare. Conditions of deposition were fully marine through the Neogene in an open shelf environment. No effects of dissolution are obvious; the planktonic Neogloboquadrina pachyderma dominates. Recycled Permian coal is a normal accessory throughout the section, and younger fossil wood and lignite are present at and below Section 188-1166-17R-CC. Foraminifer linings in palynological residues in the Paleogene section are consistent with estuarine conditions at that time.
Foraminifers are recorded throughout the 447.5-m Quaternary section in Hole 1167A on the mid-continental slope north of Prydz Bay. The foraminifer assemblages alone are of little value in establishing the age of the section but yielded enough for Sr dating and 18O studies. Presence/absence and features of the benthic component are used to divide the section into six units:
Foraminifer numbers are low, and other biota are represented by fragments. Opaline siliceous fossils are virtually absent. Most Site 1167 assemblages have moved from the continental shelf, where they lived, to the continental slope, where they accumulated. Benthic assemblages are dominated by spherical and tapered infauna that probably lived at ~250-400 m water depth and have been transported to current depths through the mechanism of debris flow. A few thin horizons contain assemblages that are consistent with accumulation in the mid-bathyal realm and thus may not have moved since deposition. The site is near the current CCD, and movement of this surface over time probably accounts for many of the absences.
1Quilty, P.G., 2003. Neogene foraminifers and accessories, ODP Leg 188, Sites 1165, 1166, and 1167, Prydz Bay, Antarctica. In Cooper, A.K., O'Brien, P.E., and Richter, C. (Eds.), Proc. ODP, Sci. Results, 188 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/188_SR/009/009.htm>. [Cited YYYY-MM-DD]
2School of Earth Science, University of Tasmania, GPO Box 252-79, Hobart TAS 7050, Australia. p.quilty@utas.edu.au
Initial receipt: 22 July 2002
Acceptance: 19 May 2003
Web publication:
27 August 2003
Ms 188SR-009
