干旱区生态环境知识资源中心

Lithology, geochemistry, stable isotopes and integrated high-resolution biostratigraphy of the Berivotra and Amboanio sections provide new insights into the age, faunal turnovers, climate, sea level and environmental changes of the Maastrichtian to early Paleocene of the Mahajanga Basin of Madagascar. In the Berivotra type area, the dinosaur-rich fluvial lowland sediments of the Anembalemba Member prevailed into the earliest Maastrichtian. These are overlain by marginal marine and near-shore clastics that deepen upwards to hernipelagic middle neritic marls by 69.6 Ma, accompanied by and to seasonally cool temperate climates through the early and late Maastrichtian. An unconformity between the Berivotra Formation and Betsiboka limestone marks the K-T boundary, and juxtaposes early Danian (zone Plc? or Pld) and latest Maastrichtian (zones CF2-CF1, Micula prinsii) sediments. Seasonally humid warm climates began near the end of the Maastrichtian and prevailed into the early Danian, accompanied by increased volcanic activity. During the late Danian (zones P1d-P2), a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths. (C) 2002 Elsevier Science B.V. All rights reserved.