Departmental Bulletin Paper Tethyan and non-Tethyan Early Cretaceous radiolarian faunas from West Timor, Indonesia: Paleogeographic and tectonic significance

Munasri  ,  SASHIDA, Katsuo

12pp.3 - 12 , 2018-03-25 , Doctoral Program in Earth Evolution Sciences Graduate School of Life and Environmental Sciences, University of Tsukuba
Abundant and well-preserved Early Cretaceous radiolarians were recovered from calcilutites and shales of the Nakfunu Formation, Kolbano area, southern West Timor. The Cretaceous to Pliocene sedimentary rocks of the Kolbano area are an accretionary complex stacked at the leading edge of the Banda Islands arc. Radiolarian faunas of the Nakfunu Formation are characterized by the presence of unknown taxa elsewhere except its similarity with those of samples from the ODP Leg 123 Cores 765, regarded as non-Tethyan faunas. Four radiolarian assemblages have been discriminated, which indicate the range of Berriasian to early Aptian with a trend from non-Tethyan to Tethyan deposits in progressively younger strata. Stratigraphically, however, these strata are not in ascending order. The formation was imbricated, which was shown by frequent and random repetition of radiolarian assemblages in the strata. We believe that the faunas were derived from the southern paleolatitude origin generated by the influx of circumantarctic current. During the arc-continent collision commenced in the early Pliocene, the sequences were frontally accreted at the subduction zone. This findings may provide new insights to reveal the paleogeographic and tectonic significance of the island that has a long standing controversy, i.e. the original (pre deformational) location of the various stratigraphic units now present on Timor.

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