Abstract

From Jurassic through Early Miocene there was active rifting of the south China and north Australian continental margins. Magnetic anomalies of the marginal seas indicate that microcontinents were drifted as far as Borneo. Together with island orcs, these microcontinents formed the nuclei against which distal turbidites accumulated, with their source perhaps as far away as the Mekong Delta.

The post Oligocene convergence of Australia and the Philippines against Indonesia, effected by subduction of extinct marginal sea lithosphere, resulted in uplift of the ancient microcontinents and their turbidite drapes to form new provenance landmasses for shallow water sedimentation in adjacent basins.

Plate tectonic basin classification cannot be successful unless the important role of the microcontinents is recognised. Their presence in the Southeast Asian developing orogen hinders the formulation of an elegant classification.