Late cenozoic vertical movements of non-volcanic islands in the Banda Arc area

• Published in: Netherlands journal of sea research 1989-11, Vol.24 (2-3), p.263-275
• Main Authors: De Smet, M.E.M., Fortuin, A.R., Tjokrosapoetro, S., Van Hinte, J.E.
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Stratigraphy; Tectonics. Structural geology. Plate tectonics
• ISSN: 0077-7579
• DOI: 10.1016/0077-7579(89)90153-1

During onshore campaigns of the Snellius-II Expedition late Cenozoic sections were recorded and systematically sampled on the non-volcanic outer Banda Arc Islands of Timor, Buton, Buru, Seram and Kai. Microfaunal studies provided age and palaeobathymetric data to construct geohistory diagrams. Geohistory analysis of field and laboratory data allows to calculate rates of vertical movements of the island basements. The vertical movements were intermittent and differed widely from place to place in the arc; short periods of uplift alternated with longer periods of tectonic rest or subsidence and lateral variations in timing and magnitude seem to be more the rule than the exception. Movements affected larger segments of the arc at about the same time, especially since the late Pliocene, when widespread vertical movements started, which led to the present configuration of the arc. Rates of uplift or subsidence differed within each segment. On an intermediate scale, deformation has the character of tilting or doming of whole islands or parts of islands. On a local scale, various types of deformation occur. Calculated duration of uplift pulses is in the order of a million years where less than 50 cm·ka−1 of vertical movements are involved. Sections, however, with a high time stratigraphic resolutions show pulses of uplift with a duration of only some hundreds of thousands of years and rates of more than 500 cm·ka−1. The duration of such pulses therefore is comparable to that of eustatic third order sea level changes. But because their amplitude is an order of magnitude larger, this implies that in tectonically active areas eustatic signals, preserved in the sedimentary record, will be overprinted by tectonics, i.e. will be difficult to disentangle from the tectonic signal.