Structural evolution and strike-slip tectonics off north-western Sumatra

Abstract

Based on new multi-channel seismic data, swath bathymetry, and sediment echosounder data we present a model for the interaction between strike-slip faulting and forearc basin evolution off northwestern Sumatra between 2°N and 7°N. We examined seismic sequences and sea floor morphology of the Simeulue-and Aceh forearc basins and the adjacent outer arc high. We found that strike-slip faulting has controlled the forearc basin evolution since the Late Miocene. The Mentawai Fault Zone extends up to the north of Simeulue Island and was most probably connected farther northwards to the Sumatran Fault Zone until the end of the Miocene. Since then, this northern branch jumped westwards, initiating the West Andaman Fault in the Aceh area. The connection to the Mentawai Fault Zone is a left-hand step-over. In this transpressional setting the Tuba Ridge developed. We found a right-lateral strike-slip fault running from the conjunction of the West Andaman Fault and the Tuba Ridge in SSW-direction crossing the outer arc high. As a result, extrusion formed a marginal basin north of Simeulue Island which is tilted eastwards by uplift along a thrust fault in the west. The shift of strike-slip movement in the Aceh segment is accompanied by a relocation of the depocenter of the Aceh Basin to the northwest, forming one major Neogene unconformity. The Simeulue Basin bears two major Neogene unconformities, documenting that differences in subsidence evolution along the northern Sumatran margin are linked to both forearc-evolution related to subduction processes and to deformation along major strike-slip faults.

Chapter 13 Anatomy of the Andaman–Nicobar subduction system from seismic reflection data

“…Their evolution is therefore recorded in the depositional sequences as a series of subsidence and uplift events, directly associated with subduction processes (Berglar et al 2010;Ryan et al 2012), over millions of years. Furthermore, forearc basins are thought to play a role in the seismic cycle as well as during large earthquake ruptures.…”

Chapter 2 Active tectonics of Myanmar and the Andaman Sea

“…Between the fault-bounded highs are basins several kilometres deep, thought to be filled with Miocene-Recent sediments. Seismic reflection data along the southern portion of the West Andaman Fault Zone suggests that it was only active since the Middle Miocene or younger (depending upon how unconformities on the seismic data are correlated; Berglar et al 2010). Further north, however, long-distance extrapolation of horizons on seismic data from shallow-water wells east of the Andaman Islands suggests that fault activity may extend Barren Island and Narcondam Island are subaerial volcanic edifices west of the main Sewell Rise, forming seamounts within the region of strike-slip-transtensional faulting.…”

Deformasi Kompleks Di Pulau Simeulue, Sumatra: Interaksi Antara Struktur Dan Diapirisme

“…Ujung dari prisma akresi yang dekat dengan palung menunjukkan sesar anjak yang berarah ke palung dan ke darat (McNeill & Henstock, 2013). Sementara itu di bagian baratlaut Pulau Simeulue, perkembangan prisma akresi menunjukkan sesar anjak yang mengarah ke palung dimana bagian yang naik adalah blok yang berada di timurlaut (Berglar et al, 2010).…”

“…Pada kompleks prisma akresi, sesar yang dominan berkembang adalah sesarsesar anjak yang berarah palung dengan dip berarah cekungan (McNeill & Henstock, 2013). Pada penampang seismik di sekitar lepas pantai Simeulue tergambarkan bahwa kompleks prisma akresi Simeulue dominan berkembang sesar anjak berarah palung (Berglar et al, 2010;Singh et al, 2008;Shulgin et al, 2013) .…”