PALEOSOLS IN PERMO-TRIASSIC CONTINENTAL SEDIMENTS FROM PRYDZ BAY, EAST ANTARCTICA

ODP Leg 119 drilled a sequence of ?Permo- Triassic continental red bed s 58 m thick containing paleosols in Prydz Bay, East Antarctica. The p aleosols, mainly in overbank siltstones and mudstones, are characteriz ed by extensive destruction of sedimentary structures and the presence of mottles, rootlets, and rare chalky caliche. BecaUse Of the shallow depth of burial and limited compaction and diagenesis. the paleosols have retained most of their original microstructure and fabric. Microm orphological analysis of the paleosols reveals the presence of phreati c monopodial root systems, nodules, and a variety of soil structures a nd fabrics as well as a micritic root structure with alveolar texture. Most of the paleosols are weakly developed, with small, incomplete pe d structures and lack of illuviation. They resemble weakly developed a lluvial soils with A-C and B(C) profiles, and are similar to modern ba se-deficient inceptisols. The nature of the paleosols suggests relativ ely high permeabilities and water circulation during soil formation an d a relatively mobile water table, with little reduction of iron excep t locally on the less well drained parts of the alluvial plain. Extens ive pedogenic carbonate formation was precluded by the soil-moisture r egime and relatively wet climate. During Late Permian and Early Triass ic times Prydz Bay, which lay some 30' south of the Equator, experienc ed climatic conditions broadly similar to parts of the contemporary tr opics, dominated by a subtropical high-pressure system, easterly winds . and seasonal rainfall.