The Bantimala Complex of South Sulawesi, Indonesia is an assemblage of northeastdipping tectonically stacked slices. The slices consist mainly of high pressure metamorphic rocks, radiolarian chert, breccia, sandstone and shale, and melange. In order to understand the tectonic evolution of the Bantimala Complex, we have investigated the lithology, age, stratigraphy, structure and relationships of the components. The K-Ar ages of high P-low T metamorphic rocks suggest that an oceanic plate subducted beneath the Sundaland continent during the Late Jurassic or earliest Cretaceous. The subduction ceased during the Albian, and the high pressure schists were exhumed and eroded at the surface before and during the deposition of middle Cretaceous radiolarian chert. The exhumation of the schists was related to the collision of microcontinents derived from Gondwanaland. The Jurassic shallow marine sedimentary rocks in the Bantimala Complex are possibly remnant fragments of the collided microcontinent. Tectonic stacking of the Bantimala Complex was caused by Neogene subduction and collision of another continental fragment further to the east.

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The Bantimala Complex of South Sulawesi consists mainly of mklange, chert, basalt, ultramafic rocks and high pressure type metamorphic rocks. Well-preserved radiolarians were extracted from 10 samples of chert, and K-Ar age dating was done for muscovite from five samples of schist of the Bantimala Complex. The radiolarian assemblage from chert is assigned middle Cretaceous (late Albian-early Cenomanian) age, while the K-Ar age data from schist range from 132 Ma to 114 Ma except for one sample with rare muscovite. The radiolarian chert is unconformably underlain by schist in the Bantimala Complex. The stratigraphic relationship and the time lag of these two kinds of age data from chert and underlying schist suggest short-time tectonic events immediately followed by a quick waning tectonism in this region during the Albian-Cenomanian transgression.

Rocks of the Lok Ulo Complex crop out over a small area in the vicinity of Karangsambung in central Java. They are part of a belt of Cretaceous accretionary-collision complexes that appear sporadically in an arc extending from Java to Kalimantan and Sulawesi. The complex consists of dismembered ophiolites, sedimentary rocks, and crystalline schists and gneisses occurring as tectonic slabs in a black-shale matrix tectonic mélange. High-pressure rocks such as eclogite, glaucophane rock and blueschist crop out in a thin zone between the low-grade schists and a serpentinite zone along the Muncar and Gua rivers. Some of the eclogite blocks contain tourmaline, which is restricted to the outer shells of-and veins in-such blocks.The early metamorphic stage (stage I) of the Lok Ulo eclogites comprises garnet (core) and omphacite + Ca-Na amphibole + phengite + rutile + epidote inclusions in the garnet core. Stage II is characterized by garnet (rims of porphyroblasts) + omphacite + rutile + phengite + Ca-Na amphibole. The matrix constituents, which are similar to those of stages I and II, are related to stage III (late or "peak" eclogitic stage). The blueschist overprint of the eclogites occurred during stage IV. The corresponding assemblage is Na amphibole + chlorite + albite + epidote + quartz + titanite + ilmenite. Subsequently, poikiloblastic tourmaline and apatite grew at the expense of chlorite, epidote, and other minerals in some eclogites (stage V).The P-T path of tourmaline-bearing eclogites is characterized by rising pressures at decreasing temperatures (stage I to stage III: P = 22.5 kbar and T = 365°C), whereas the normal eclogites show rising temperatures at increasing pressure (stage III: P = 20.5 kbar and T = 410°C). Thus, these eclogites were subducted to ~70 km depth at a geothermal gradient of ~6 C°/km. Stage IV is limited to the P-T range of 8-10 kbar and 350-400°C for both eclogite types. The different P-T paths (counterclockwise and clockwise) are explained by metamorphism within a subduction channel. The low geothermal gradient is probably due to a high rate of subduction of a cold oceanic plate.

This paper contains extended abstracts of the seven papers presented at the symposium 'Radiolarians and Orogenic Belts' held at the seventh meeting of the International Association of Radiolarian Paleontologists (INTERRAD). Important results of the symposium include the following: (1) Upper Paleozoic and Mesozoic cherts are widely distributed within accretionary complexes in the circum-Pacific orogenic belt. Radiolarian dating reveals that long durations of chert sedimentation in a pelagic environment are recorded on both sides of Pacific-rim accretionary complexes (e.g. New Zealand, Japan, Russian Far East, Canadian Cordillera). (2) Triassic radiolarian faunas from New Zealand and the Omolon Massif, northeast Siberia are similar in composition and are characterized by the absence of typical Tethyan elements. This suggests that radiolarian faunal provincialism may have been established as early as the Triassic. High-latitude radiolarian taxa exhibit a bi-polar distribution pattern.(3) The Lower Triassic interval in chert dominant pelagic sequences is mechanically weaker than other levels and acted as a dkcollement in accretionary events. This lithologic. contrast in physical property is considered to reflect radiolarian evolution, such as the end-Permian mass extinction.

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Moderately well-preserved Middle Triassic radiolarians were recovered from bedded limestone exposed at about 3 km west of Kefamenanu, West Timor, Indonesia. This limestone probably from the Aitutu Formation is considered to be an allochthonous block and is embedded in the Neogene Bobonaro Complex. The radiolarian fauna in this limestone is characterized by abundant radiolarians of typical Tethyan forms and is identical to that of the early Fassanian (early Ladinian) of European Tethys and other related faunas reported from the Philippines, Russian Far East, and Japan. The Aitutu Formation is thought to be deposited in an ocean environment dominated by a warm-water current system originating from the low latitude Tethyan realm. Fifty-nine species belonging to 34 genera, including five unidentified genera, are systematically treated, among them, five new species; Parentactinia suparkai, Pseudostylosphaera timorensis, Cryptostephanidium? megaspinosum, Tetrarchiplagia compacta, and Planospinocyrtis kefaensis.

The Luk Ulo Mélange Complex (LUMC) is composed of tectonic slices of rocks that surrounded by scaly clay matrix. These rocks consist of serpentinite, gabbro, diabase, and basalt, eclogite, blueschist, amphibolite, schist, gneiss, phylite and slate, granite, chert, red limestone, claystone and sandstone. The LUMC was formed since Paleocene to Eocene, gradually uplifted of HP-UHP metabasic-metapelite (P: 20-27kbar; T: 410-628°C) to near surface mixed with hemipelagic sedimentary rocks. The metamorphic rocks were formed during 101-125 Ma (Early Cretaceous) within 70 to 100 km depth and ∼6°C/km thermal gradient. It took about 50-57 Myr for these rocks to reach the near surface during Paleocene-Eocene, with an uplift rate at ∼1.4-1.8 km/year to form the mélange complex. The low thermal gradient was due to subduction of old and cold oceanic crust. The subducted oceanic crust (MORB) as protolith of Cretaceous metabasic rocks must be older than Cretaceous. The data show that the basalt of oceanic crust is Cretaceous (130-81 Ma) comparable to the age of the cherts (Early to Late Cretaceous). Therefore, we consider that neither oceanic crust exposed in LUMC nor all of part of the old oceanic crust is the protolith of LUMC metabasic subducted beneath the Eurasian Plate. These oceanic rocks possibly originated or part of the edge of micro-continental that merged as a part of the LUMC during the collision with the Eurasian margin.