Foraminifera Analysis of Long-term Surface Uplift History of the Incipient Banda Arc-Continent Collision, Rote and Savu Islands, Indonesia

Nova Roosmawati 
Geology Department, Brigham Young University, Eyring Science Center
Provo, Utah
nr63@email.byu.edu

Analyses of foraminifera from synorogenic deposits in Rote and Savu reveal the long-term surface uplift history of the incipient Banda arc-continent collision. Estimates of paleodepth are provided by benthonic forams and ages by planktonic forams.

The samples from synorogenic units of western Rote yield forams of N21 (3.1 – 1.8 Ma) and depth from 2500-3800 meters at the base of the section, and depths of 1200 meters near the top of the section. Similar ages were found in central and eastern Rote eastern with depth ranges of 2000 – 5000 meters. Because all of the sections are about the same elevation presently, long-term surface uplift rates are slightly higher (1.6 mm/yr) in eastern and central Rote than those in the western Rote.

These results indicate that the Banda arc-continent collision arrived in Rote after around 3 Ma. Long-term surface uplift rates, at a temporal scale of 10⁶ years, are similar to short-term rates measured using uplifted coral terraces, at temporal scales of 10⁴ – 10⁵ years. Most uplift was in a submarine setting and therefore involved minimal erosion. Uplift of Rote corresponds to its position at the boundary between the Sumba/Savu block moving mostly with Asia and the Timor block moving mostly with Australia. Uplift of Savu is responding to the northward propagation of the Savu thrust, which forms the near of the orogenic wedge. Uplift associated with these structures demonstrates how strain is partitioned away from the trench during the incipient stages of arc-continent collision.