Discontinuously rising Late Cainozoic eustatic reference to Sundaland, Southeast Asia

Abstract

A Late Cainozoic global eustatic sea-level rise, of greater magnitude and opposite trend to previous schemes, is indicated, with important consequences on climates, sedimentation, pedogenesis, oceanographic features and biological distributions, especially for Sundaland and other equatorial regions. An abrupt sealevel depression during the late Middle Miocene to around 1000 m below present, is correlated with an emergent Sundaland continent. Increased land/sea area ratio resulted in more seasonal semi-arid climates facilitating savanna expansion and laterite clevelopment. A major Miocene discontinuity in sundaland is paralleled worldwide by contemporaneous unconformities or facies changes on continental terraces, reduced oceanic sedimentation and truncation and pedogenesis on Pacific reefs. Sea levels have since risen discontinuously at around 10 cm/103 a with maximum transgression in the late Quaternary. Sea-level curves are constructed assuming that eustasy is mainly due to superposition of glacio-eustatic fluctuations on a linear tectono-eustatic trend, adjusted to fit Sundaland data. Before the Middle Pleistocene Sundaland coastlines changed very little. once since then did seas rise above the shelf-break causing major coastline shifts, dramatically affecting sedimentation climates' and Extinctions of savanna-adapted mammals resulted from their geographical isolation and unsuitability of increasingly homogeneous rain-forest habitats. Intervening glacials temporarily restored former continental environments.