Plio-Quaternary Seismic Stratigraphy of Ross Sea Eastern Basin (Antarctica): Implications to Glacial History and Basin Evolution

ALONSO, M. BELEN, Ins. Ciencias del Mar, Barcelona, Spain, JOHN S. ANDERSON, Rice University, Houston, TX, JOSE I. DIAZ, Ins. Ciencias del Mar, Barcelona, Spain, and LOU BARTEK, Rice University, Houston, TX

From air-gun and water-gun high-resolution single-channel seismic records, seven seismic units are defined, overlying the Ross Sea Unconformity, in the Plio-Quaternary sequences of the Ross Sea Eastern basin. These units are up to 600 m in thickness and generally thin onshore, disappearing near the western limit of the basin. The units are separated by smooth erosional surfaces characterized by continuous, high-amplitude reflectors. By correlation to DSDP Site 272, seismic units I and II are Pliocene in age, and the overlying units (III to VII) are Quaternary in age. Units I, III, and VII are basinal in extension and the others are confined to the central part of the basin. Thickness of the units ranges from 50 to 120 m, and they are mainly characterized by lenticular and wedge geomet ics. Three acoustic facies are discerned: stratified, semitransparent, and chaotic. Wide (7 km) lenticular deposits, containing chaotic facies, are incised by U-shaped channels in seismic units II, III (both up to 0.5 km wide), and VI (2 km wide), The spatial distribution of these channels indicates a paleodrainage system in which ice streams followed flow paths similar to those of the present.

The major geological events that occurred on the continental shelf during Plio-Quaternary time were: (1) the first channel incisions are identified near the boundary of the late Pliocene-Quaternary; (2) the advance and retreat of the ice sheet resulted in widespread erosion processes alternating with deposition of glacial and glaciomarine sediments; (3) the largest depocenter has been always situated in the shelf break environment, near the western limit of the basin; and (4) the only important progradation of the shelf occurred during the late Pliocene, and since then the shelf has been aggradational.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)