Résumé
The Upper Triassic limestones of central and western and Seram, were deposited on an extensive carbonate platform, already identified in various localities all around the Banda Sea: Sinta Ridge, central–east Sulawesi, Buru, Misool and the Wombat Plateau (off NW Australia). The Triassic deposits are found in the parautochthonous, as well as in the allochthonous series of Seram; the facies of the two series are of Gondwanian–Australian type in the Parautochthonous and of Laurussian–Asian type in the Allochthonous. The Asinepe Limestone (=Manusela Formation), on which this study is based, has been considered as part of the allochthonous series.
The Triassic reefal lithotypes can be divided into four main facies, as follows: (1) the boundstone facies forming the buildup cores; (2) the oncolitic grainstone-rudstone facies, indicating high energy conditions; (3) foraminiferal packstone-grainstone facies, characteristic of moderate to high energy conditions; and (4) the foraminiferal-megalodont mudstone facies, inferred to have accumulated in a quiet lagoonal environment. Forming the buildup cores of about 4 m long, 2 m high; they are separated by depressions filled with reef detrital sands;
The Asinepe Limestone was deposited during the Late Triassic (Carnian–Norian to Rhaetian). This range is corroborated by foraminiferal and palynological data, and the coral framebuilders give evidence for a Norian–Rhaetian age.
There is a some consensus that Seram and the Island of Buru, located west of Seram, belong to the same tectonic block (Seram-Buru Block). According to geochemical and geodynamic interpretations, the Seram-Buru Block is derived from Irian Jaya or from Papua New Guinea. The palynological results are consistent with reconstructions that place the Seram-Buru Block in a palaeogeographic zone distinct from that of Sulawesi, and therefore from the Kolonodale Block. For these reasons, it is here proposed that, during the Upper Triassic, the Seram-Buru Block and the Kolonodale Block were two separated entities, the former located in a more tropical position than the latter. In addition, the Seram palynological association shows a composite microflora of the warm Onslow and the cold Ipswich-types, suggesting that the Seram microcontinent moved progressively to the north and crossed the boundary between the temperate and the warm subequatorial belts at one point in the Late Triassic–Early Jurassic.