Proceedings Chapter
Reference
Upper Triassic reefal facies in E Sulawesi, Indonesia
MARTINI, Rossana, et al.
MARTINI, Rossana, et al . Upper Triassic reefal facies in E Sulawesi, Indonesia. In: Sediment 96. 11th Meeting of Sedimentologists . Wien : Universität Wien, Institut für Geologie - Institut für Paläontologie, 1996. p. 109
Available at:
http://archive-ouverte.unige.ch/unige:4766
Disclaimer: layout of this document may differ from the published version.
1 / 1
SEDIMENT ' 96
11 .Sedimentologentreffen
UPPER TRIASSIC REEFAL FACIES lN E SULAWESI, INDONESIA
MARTINI, R.1I, VACHARD, 0.21, ZANINETTI, L.1I, CIRILLI, 5.31, CORNÉE, J.-J.41, LATHUILIERE, B.51 and VILLENEUVE, M.41
1)Département de Géologie et Paléontologie, 13 rue des Maraîchers, 1211 Genève 4, Switzerland 21 CNRS URA 1365, Univ. de Lille, 59655 Villeneuve-d'Ascq Cedex, France
3)Dipartimento di Scienze della Terra, 4 piazza Università, 06100 Perugia, Italy
4)CNRS URA 1208, Univ. de Provence, 13331 Marseille Cedex 03, France
5)CNRS URA 157, B.P. 239, 54506 Vandoeuvres-Lès-Nancy Cedex, France
The investigated area is located between Kolonodale and T omata on the western margin of the Ophiolitic Zone, represented by the eastern and southeastern arms of Sulawesi. This Zone is composed of a dismembered ophiolitic complex which was obducted into Mesozoic and Coenozoic sedimentary rocks. Although the sedimentary rocks are poorly known, they are generally considered as Australian in type.
ln this area of Sulawesi, we recently investigated a widely outcropping Late Triassic reefal carbo- nate platform, which appears today as an important witness for geodynamic reconstructions in Indonesia, as other fragments of Late Triassic carbonate platforms were also recorded around the Banda Sea.
The Upper Triassic (Late Norian-Rhaetian) age of this carbonate complex is based on a rich assemblage of benthic foraminifera, and also on the occurrence of the youngest Mesozoic (Uppermost Sevatian to Upper Rhaetian) conodont Misikella posthemsteini KOZUR & MOCK. A rich palynological assemblage contains Late Triassic-Early Liassic palynomorphs mostly repre- sented byNeoraistrikia spp., Uvaesporites verrucosus and Combaculatisporites baculatus.
The paleodepositional environ ment is characterized by patch reefs, lagoonal areas, oolitic bars, tidal flats with algal mats and higher energy stone deposits. Most of the limestones are interpreted as bioclastic accumulations, the organic carbonate production being represented by small buildups developed in protected areas, and by the algal mats.
The micropaleontological analysis emphasizes the presence of two - a lagoonal and a reefal - foraminiferal associations. The lagoonal association, dominated by Triasina hantkeni and other Aulotortidae, is characteristic of the mud facies with megalodonts. The reefal association contains dominant porcelaneous foraminifers such as the genus Galeanella, typical of the algal-coral boundstone; the infralittoral branching coral Retiophyllia seranica and the massive chaetetid sponge Blastochaetetes intabulata, together with solenoporacean algae, are the main framebuilders in this facies.
The who le Upper Triassic carbonate series of the Kolonodale area shows a general regressive sequence documented by a graduai environment evolution from an outer to an inner platform. The shallowing upwards trend is emphasized by the transition from patch reefs and lagoonal mud to intertidal/supratidal algallaminites. The palynofacies of intercalated maris, at the top of the platform, dominated by a high percentage of thick walled sporomorphs, large fragments of cuticule remains and other palynomacerals, is indicative of a shallow water environ ment near the shoreline.
The relationship between microfaunal distribution and séquence analysis is discussed. As generally observed in Triassic localities, abundant microfaunas are located within the TST/HST of the sequences, independently of the stratigraphie interval. Thus major foraminiferal diversity appears to be related to a sea level rise, with the development of carbonate platform facies. As already mentioned in the cc Atlas Tethys »by MARCOUX et al. (1993), cc a Late Norian highstand system is weil demonstrated by strongly prograding carbonate plattorrns » within the western Tethys. This HST of the UAB-1 second-order cycle (215 - 211 Ma), also identified in the Upper Triassic of Sulawesi, seems to correspond to a major global event being recognized in the eastern Tethys as weil. The algal-fenestral limestone, which overlies the carbonate platform, may reflect a relative sea-Ievel lowstand (LST) at the base of the UAB-2 second-order cycle.
The Kolonodale Upper Triassic foraminifers and palynomorphs confirm the affinities of this area of Sulawesi with the Australian-Indonesian southern Tethyan domain.
109
