期刊
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
卷 206, 期 1-2, 页码 75-102出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.palaeo.2003.12.020
关键词
Seram; Upper Triassic; reefal carbonates; foraminifers; corals; palynomorphs; palaeobiogeography; plate tectonics
The Upper Triassic limestones of central and western and Scram, were deposited on an extensive carbonate platform, already identified in various localities all around the Banda Sea: Sinta Ridge, central-east Sulawesi, Burn, 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 (Camian-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 Scram 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 Serant-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 Scram 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. (C) 2004 Elsevier B.V. All rights reserved.
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