Halo eric tolongin bony yaaa makasi eric wijayaa

India- Asia CollisionBased on Extrusion ModelTapponier (1986)

TECTONIC EVOLUTION

Daly, et al., 1991

TECTONIC EVOLUTION OF WESTERN INDONESIA

• Clockwise Rotation

Hall, 1996• Counter Clockwise Rotation

TAPONIER, 1982

Model Tektonik Asia Tenggara Menurut Taponier (1982) • Usaha orang untuk merekonstruksi tataan geologi masa lampau di Asia Tenggara (termasuk

di dalamnya Indonesia bagian barat) sempat terpengaruh oleh kemuculan ‘model ekstrusi’ yang diajukan oleh Tapponier drr (1982). Model ini menggambarkan tumbukan India terhadap Eurasia yang berakibat terdesaknya bagian tenggara Asia. Model ini menurut beberapa lawan ilmiahnya kurang seimbang dalam ukuran, selain itu langkanya gerakan sesar mendatar yang aktif (Sesar Sungai Merah di Vietnam) tidaklah menunjang, demikian pula perpendekan kerak bumi di Tibet tidak dipertimbangkan (Daly drr., 1986).

• Molnar dan Taponier (1975) dan Taponier et al (1982), menyatakan bahwa tektonik Indonesia bagian barat dipengaruhi oleh tumbukan lempeng anak benua India dengan lempeng benua Eurasia yang terbentuk pada zaman Kenozoikum. Peristiwa ini menyebabkan terjadinya perpindahan sejumlah blok ke arah timur atau tenggara. Perpindahan blok tersebut melalui sesar-sesar mendatar, antara lain melalui sesar Sumatra (Huchon dan Le Pichon, 1984).

TAPONIER, 1982

TAPONIER, 1982

Clockwise Rotation Daly et al 1991

Clockwise Rotation Daly et al 1991During the period studied, the tectonic configuration of the Indonesian area underwent several profound changes. These are listed below as the major events influencing the tectonic evolution of Indonesia during the Tertiary. (1) At about 50 Ma, the southern Eurasian margin changed from being a convergent margin to

a continent/continent collisional orogenic belt as India collided. (2) At 42 Ma, the Pacific plate motion changed from NNW to WNW, relative to the hot-spot

frame of reference. (3) At about 40 Ma (Middle to Late Eocene), extension generated the Sumatran basins in a back

arc setting. During the Late Oligocene the southernmost of these basins experienced a major contractional event due to reversal of the arc and closure of the back arc basin.

(4) At 32 Ma, ocean-floor spreading began in the South China Sea, with concomitant subduction in NW Borneo.

(5) At about 25 Ma, the northern passive margin of Australia came into direct contact with the Pacific plate.

(6) At 17 Ma, ocean-floor spreading ceased in the South China Sea as Palawan and the Reed Bank Terrane collided with Borneo.

(7) At about 8 Ma, the Banda Arcs collided with northern Australia.

70 Ma reconstruction, Late Cretaceous

70 Ma reconstruction, Late Cretaceous

India at this time had separated from Africa, and was moving rapidly NNW, converging on Eurasia with a velocity of between 150 and 200 mm/yr (Patriat and Achache, 1984). Oceanic crust of the Indian plate was being subducted to the north beneath Eurasia. Australia was drifting slowly eastwards. The reconstruction shows the southern margin of Eurasia restored as a WNW trending magmatic arc. This configuration emphasises the effects of the Indian collision with Eurasia. During the Late Cretaceous, the southern and eastern margins of Eurasia were dominantly subducting margins. These arcs are today seen as the Cretaceous Trans-Himalayan batholith (Zhang et al., 1984) and the I-type granites of Burma, Malaya and China (Cobbing et al., 1986).

55 Ma reconstruction, End Paleocene

55 Ma reconstruction, End Paleocene