OUTLINE OF QUATERNARY TECTONICS OF INDONESIA

Abstract

Quaternary teetonics in fndonesia is conveniently grouped into four types comprising ( 1) uplift and subsidence, Q)warping and folding, (3) horizontal displacements, and (4) volcanotectonic deformations. Quaternary age of the various deformations is mostly inferred from horizontal to subhorizontal attitudes of strata or erosion surfaces, percentage of living mollusc and/or coral species in fossil assemblages, mammalian fauna, imglements, incomplete recrystallization or compaction of sediments, and incomplete devellopment of post Glacial "Daly levels". Radiometric dates for fndonesian Quaternary deposits are rare. Uplift is generally intermittentas is indicated by the presence of multfple coral reef terraces and other types of marine phenomena. The maximum uplift has exceeded 750 meter during the Quaternary. Subsidence implies similar rates of displacement but results in greater depths through absence of denudation. Quaternary folding has raised the land to about 300 meter elevation. Warping has even affected the "stable" regions like e.g. the Sunda Shelf. Horizontal displacements are important along transcurrent faults; e.g. the Lembang Fault near Bandurg, Java, displays a mean horizontal shift of L40 m in the last 6,000 years or even shorter. Vertical displacement through volcanotectonic collapse of the volcanoes and resulting folding through gravity tectonics of the bases are common features and has continued into subhistorical time. Contemporary tectonic diastrophism such as uplift and faulting is especially apparent in the Moluccas.