Biochronologic and Magnetochronologic Synthesis of Leg 119 Sediments from the Kerguelen Plateau and Prydz Bay, Antarctica

Abstract

This paper summarizes the biostratigraphy and magnetostratigraphy of the 11 sites drilled on the Kerguelen Plateau and in Prydz Bay, Antarctica, during ODP Leg 119. Excellent magnetobiochronologic reference sections were obtained at deep-water Sites 745 and 746 (0-10 Ma) and at intermediate depth Site 744 (0-39 Ma) on the southern Kerguelen Plateau. Site 738, an intermediate depth companion site for Site 744, contains a nearly complete lowermost Oligocene to Turonian carbonate section including a continuous sequence across the Cretaceous/Tertiary boundary. Northern Kerguelen Sites 736 and 737 (ca. 600 m water depth) constitute a composite middle Eocene to Quaternary reference section near the present-day Antarctic Polar Front. Biostratigraphic control is limited in Prydz Bay Sites 739-743. Glacial sequences cored on the continental shelf at Sites 739 and 742 appear to form a composite record, possibly from the uppermost middle Eocene to the Quaternary; the entire upper Oligocene and most of the Miocene, however, are removed at an unconformity. Preglacial sediments at Site 741 contain Early Cretaceous pollen and spores, but the red beds cored at Site 740 are unfossiliferous. Poorly-fossiliferous glacial sediments of probable Quaternary age were sampled on the upper slope at Site 743. A magnetobiochronologic time scale is presented for the Late Cretaceous and Cenozoic of the Southern Ocean based on previous studies and the results of Leg 119 studies.

Significance of clay mineral assemblages in the Antarctic Ocean

“…The age of the sediments ranges from early Oligocene (possibly late Eocene) to Holocene. The total lack of microfossils in parts of the core and the lack of age-diagnostic microfossils through extended core intervals allowed only a rough dating of the sedimentary sequence (Barron et al, 1991 ).…”

Oligocene-Pleistocene Calcareous Nannofossils from Southern Ocean Sites 747, 748, and 751

“…This datum occurs at ~ 11.1 Ma, as calibrated with magnetostratigraphy at Site 744 Barron et al, 1991), an age similar to that of the LO of Cyclicargolithus floridanus at lower latitudes (11.6 Ma; see further discussion by Wei and Wise, this volume).…”

“…macintyrei was placed between Samples 120-747A-11H-1, 58-62 cm, and -11H-2, 10-11 cm. This datum has been correlated with magnetic Chron C5D (-18.2 Ma) at Site 744 Barron et al, 1991), and is a useful datum in the southern Indian Ocean (Wei and Wise, this volume).…”

“…This datum has been calibrated with magnetostratigraphy at ODP Site 744 on the Southern Kerguelen Plateau at about 3.8 Ma Barron et al, 1991), very close to the age of the LO of Reticulofenestra pseudoumbilica (3.5 Ma; Berggren et al, 1985). This is not surprising because R. gelida differs from R. pseudoumbilica mainly in its smaller central opening, and many workers consider the former species to be a junior synonym of the latter (see detailed discussion by Backman, 1980;Wise, 1983;Perch-Nielsen, 1985).…”

Pleistocene Radiolaria from Leg 119 Site 738B (Sections 1H1-1H2): Systematics and Biostratigraphy

“…[40] identified two new genera and seventeen new species from the Neogene sediments of the Kerguelen plateau. [41] carried out work on the biochronology and magnetostratigraphy of the Antarctic sediments. [42] established radiolarian from Eocene to Recent biostratigraphy, biogeography, diversity, and history of Southern Ocean.…”