The lower Paleozoic sedimentary sequence in the Malay Peninsula begins with Upper Cambrian rocks and can be traced through a series of well-defined geosynclinal deposits to the Lower Devonian. The strata include shelf-limestone facies and a euxinic-basin facies deposited in the miogeosyncline, a mixed facies deposited over the geanticlinal upwarp, and a flysch-type eugeosynclinal sequence. Acid pyroclastic rocks and an ophiolitic suite of igneous rocks are associated with the deposits of the eugeosynclinal trough. True geosynclinal conditions seem to have been arrested in middle Paleozoic time by mild orogenic uplift in the northwest with subsequent eastward migration of the geosynclinal belt. The early Paleozoic geosynclinal pattern possibly played an important structural role in the siting of some of the larger granite batholiths emplaced during the main orogenic phase in middle Mesozoic time.