The Geology of Indonesia/Stratigraphy/Paleozoic

Summary map of the distribution of key Paleozoic and Mesozoic outcrops in Indonesia. First published in Darman & Sidi, 2000

• Silurian

Hallysites wallichi REED is the oldest of the fossils found to date in the Indian Archipelago (VAN BEMMELEN, 1949). It occurs in limestone boulders in the Snow Mountain Range of New Guinea and has been described by TEICHERT (1928) and MUSPER (1938). This fossil points to Upper Silurian and it represents the oldest fossil-bearing strata in the circum-Australian Mountain System.

• Devonian

The oldest fossil-bearing strata of the Sunda area (i.e. the Asiatic part of the archipelago) have a lower-Devonian age. This has been stated by M. G. RUTTEN (1940, 1947), who found Clath- rodiction d. spatiosum BOEHNKE and Heliolites porosus OLDFUSS in the "Danau Formation" of East Central Borneo (Telen area). SUGIAMAN and ANDRIA (1998) have revisited and analyzed the fossils from this area.

In the Central Ranges of New Guinea the Silurian is succeeded by Devonian strata. The Devonian fossils have been described by MARTIN (1911), FEUILLETAU DE BRUYN (1921), STEHN (1927), and TEICHERT (1928) in the upper part of the Modio Limestone Formation. The result of reset age of zircon fission-track (ZFT) showing age of 650±63 Ma (Quarles van Ufford, 1996). OLIVER et al, 1995 found Late Devonian (Frtasnian) corals in the Modio Limestone.

The Modio Formation is interpreted as a transgressive sequence deposited from tidal to marine shelf. The upper contact with Aiduna Formation is not well exposed and is interpreted to be disconformable (UFFORD, 1996).

Papua Stratigraphy, Sapiie, 2000

• Permo-Carboniferous

Much more is know about the distribution of permo-carboniferous rocks. Characteristic fossil faunas and floras have been found in several islands. It is not always possible to separate with certainty the Permian from the Carboniferous and, therefore, often the name "Permo-Carboniferous" is used in the literature. In the western part of the Archipelago (Malaysian Peninsula, Sumatra and Borneo), carboniferous, permo-carboniferous, and Permian fossils have been found. VON L6czy (1934) and VON KUTASSY (1934) presume the presence of Young Paleozoic in the East arm of Celebes (Tokala Mts); but HETZEL (1935, p. 30) remarks that VON KUTASSY'S plate, illustrating the concerning fossils, is too indistinct to convince the reader of the correctness of the determinations. In the outer arc of the eastern part of the Sunda Mountain System, the islands of Timor, Savu, Roti, Leti, Luang, Babar are renowned for their rich Permian fauna, especially the former. From the Snow Mountain Range of New Guinea, upper- carboniferous and Permian fossils have been described. For a summary of the above mentioned occurrences we may refer to BROUWER (1931, pp. 553-563) and UMBGROVE (1935 a, pp. 125-128). The fossils come from neritic and littoral sediments. Most probably in young paleozoic time some islands or larger land areas lay scattered in a shallow sea, which submerged at that time the East Indian region. Only in the Permian of West Borneo there are indications (radiolarian cherts and ophiolites in MOLENGRAAFF'S Danau Formation), for the presence of a deep-sea trench. In the following paragraph are quoted some recent advances of our knowledge on the carboniferous flora in New Guinea and of the Permo-Carboniferous in West Borneo. For the Permian of Timor see under Mesozoic. For further information on the occurrences of young-Palaeozoic strata in Sumatra and Malaya, the reader is referred to the regional geological descriptions.

1. PERMO-CARBONIFEROUS OF NEW GUINEA

An important contribution to our knowledge of the distribution of the Glossopteris-flora was recently given by JONGMANS (1940, 1941).

The Glossopteris-flora of the Southern hemisphere is found between India and Australia (where it has been known for considerable time). A former report of its occurrence in British North Borneo proved to be erroneous,

The flora of the Carboniferous of the Northern hemisphere (Europe, Asia, North America) can be distinguished jnto two groups: the Eurameric Flora (North America, Europe, western Asia) and the Cathaysia Flora (China and Korea). The difference between these two does not develop before the younger Carboniferous. It does not exist up till Westphalian D, but becomes apparent in Westphalian E and especially in the "Rotliegendes". The Djambi Flora (Sumatra) corresponds with the Cathaysia group in many respects, but the European character of this Djambi Flora is more pronounced than that of the typical Cathaysia Flora because it belongs to Westphalian E thus being older than the typical development of the latter. Also in the Malay Peninsula and Borneo, floras with a European character are known. Mixtures of the Eurameric Flora with the Glossopteris Flora of the southern hemi- sphere have been found in North Africa, Brazil and Central Africa. Up till 1940 no mixing of the Cathaysia with the Glossopteris Flora. was known; but now this has been demonstrated by JONGMANS for material from the southern slope of the Snow Mountain Range of New Guinea. Here have been 'found, Vertebraria (a typical element of the Glossopteris Flora) and Pecopteris- and Taeniopteris species (belonging to the Cathaysia Flora); the age is probably Westphalian E due to the presence of some Euramerian elements. This proves that also the Cathaysia Flora existed on the southern side of the Tethys where it could mix with the Glossopteris Flora of the Gondwana Land. During the younger Carboniferous the western part of the Archipelago had land connections with East Asia (China) and the eastern part with Australia.

JONGMANs(1941) also described some recent finds of up per- carboniferous plants (Westphalian D-E) from Borneo.

KEYZER (1941), summarized our knowledge of the fossiliferous Paleozoic in the Snow Mountain Range of New Guinea as follows:

Permian: Gray marly sandstones with coral limestones containing: Lonsdaleia fliegeli (ZWIERZYCKI); limestone with? Productus (HUBRECHT); ? Bryozoa-limestones (TEI- CHERT).

Upper-Carboniferous: dark shales with a Cathaysia Flora (JONGMANS); dark limestones with Martinia sp., Subulites sp., etc.; coarse micaceous calcareous sandstone with Chonetes sp., Proetus sp. (TEICHERT). South of the Carstensz summits a complex of conglomeratic, sandy and clayey rocks with Brachiopoda (Dozy). Devonian.

Upper-Devonian: Brown, beige, and white sandstones with Spirifer (Ado/jia), Retzia sp., Wi/sonia sp., Goniophora sp., etc. (FEUILLETAU DE BRUYN, TEICHERT).

Middle- (and? Lower-) Devonian: Gray, fine calcareous limestones with Favosites reticulatus (DE BLv.), Fav. sp. GERTH 1927, Cystiphyllum sp., Cyathophyllum douvillei FRECH, and Brachiopoda; dark gray sandy limestones with Heliolithes barrandei PEN.; Favosites sp. GERTH 1927, and Cystiphyllum, Silurian.

Upper-Silurian: Green limestones with Hallysites wallichi REED (TEICHERT, MUSPER).

The thickness of these Palaeozoic deposits in the geosyncline of the Snow Mountain Range is prob- ably considerable. In the section of the southern slope of the Carstensz summits drawn by Dozy (1939), the Palaeozoic strata have a thickness of 1500 m, presumably only representing a part of the Young Paleozoic.

2. PERMO-CARBONIFEROUS OF BORNEO According to ZEYLMANS VAN EMMICHOVEN (1938, p. 37), the Permo-Carboniferous of West and Central Borneo occurs in a volcanic and a non- volcanic facies:

"The normal sedimentary facies is especially characterized by frequent occurrence of siliceous rocks (chert, siliceous slate, jasper and jasperoid), Non-silicified rocks are phyllites, slates, light coloured dense clay stones, marls and limestones. The cherts may have originated by a later intensive silicification of clay shales, which are locally coaly limestones and volcanic rocks. The original rocks of the Permo-Carboniferous were predominantly clays (locally with coal beds, elsewhere with many plant remains), fine granular clay-sandstones, and subordinate limestones. No primary siliceous rocks were deposited, as was assumed by MOLENGRAAFF (1900) for the Danau Formation, at least not in the greater part of this area (Sanggau and the adjacent part of Sarawak). Rather striking is the absence of coarser clastic sediments; only very sporadically detrital material of schists were encountered. The permo-carboniferous age is proved in various places by Fusulinidae, found by KREKELER (1932, 1933), determined by ZEYLMANS V. E. and confirmed by TAN SIN HOK, in limestones, marbles, jasperoids and combust- ible clay shales, silicified into cherts. Furthermore plants, determined by JONGMANS as quite probable Calamites, possibly from the group of leioderma, and Pecopteris from the group of arborescens. Only the latter fossil plant enables a more accurate determination of the age, namely youngest Upper Carboniferous. . The volcanic facies of the Permo-Carboniferous consists of basic effusiva and ejectamenta. They are nearly always intensively decomposed and altered). These rocks are completely identic to the igneous rocks of the Pulu Melaju Zone of MOLENGRAAFF'S Danau Formation. These volcanic complexes have in numerous places supplied their detritus to upper-triassic deposits, which proves their pre-upper-triassic age. Moreover, in some places, their transition into and association with the permo-carboniferous cherts is quite probable. Therefore, their permo-carboniferous age can hardly be doubted.