Tectonic implications of new age data for the Meratus Complex of south Kalimantan, Indonesia

Abstract

Cretaceous subduction complexes surround the southeastern margin of Sundaland in Indonesia. They are widely exposed in several localities, such as Bantimala (South Sulawesi), Karangsambung (Central Java) and Meratus (South Kalimantan). The Meratus Complex of South Kalimantan consists mainly of mélange, chert, siliceous shale, limestone, basalt, ultramafic rocks and schists. The complex is uncomformably covered with Late Cretaceous sedimentary‐volcanic formations, such as the Pitap and Haruyan Formations. Well‐preserved radiolarians were extracted from 14 samples of siliceous sedimentary rocks, and K–Ar age dating was performed on muscovite from 6 samples of schist of the Meratus Complex. The radiolarian assemblage from the chert of the complex is assigned to the early Middle Jurassic to early Late Cretaceous. The K–Ar age data from schist range from 110 Ma to 180 Ma. Three samples from the Pitap Formation, which unconformably covers the Meratus Complex, yield Cretaceous radiolarians of Cenomanian or older. These chronological data as well as field observation and petrology yield the following constraints on the tectonic setting of the Meratus Complex. (1) The mélange of the Meratus Complex was caused by the subduction of an oceanic plate covered by radiolarian chert ranging in age from early Middle Jurassic to late Early Cretaceous. (2) The Haruyan Schist of 110–119 Ma was affected by metamorphism of a high pressure–low temperature type caused by oceanic plate subduction. Some of the protoliths were high alluminous continental cover or margin sediments. Intermediate pressure type metamorphic rocks of 165 and 180 Ma were discovered for the first time along the northern margin of the Haruyan Schist. (3) The Haruyan Formation, a product of submarine volcanism in an immature island arc setting, is locally contemporaneous with the formation of the mélange of the Meratus Complex.

Early Cretaceous Radiolarians in Manganese Carbonate Nodule From the Barru Area, South Sulawesi, Indonesia.

“…However, most of species member within these assemblage are different with those in the Barru Complex, except for Pseudodic tyomitra carpatica and Pantanellium squinaboli. Wakita et al (1998) also found manganese carbonate nodule in melange of Laut Island, but lack of radiolarian or very poorly preserved. This difference may be influenced by sedimentation environment and/or paleo-current that bring nutrient for radiolarians life.…”

“…Radiolarian assemblage of the similar age to that in Barru Complex is also occur in Laut Island, Meratus Complex in South Kalimantan (Wakita et al, 1998). Radiolarians in Laut Island were extracted from chert and siliceous shale in the melange.…”

“…Radiolarian occurrences were reported mainly from Mesozoic strata (Okamoto et al, 1994;Wakita et al, 1994aWakita et al, , 1994bWakita et al, , 1998Sashida et al, 1996Sashida et al, , 1999aSashida et al, , 1999band Jasin and Haile, 1996). All of these radiolarians were extracted from chert, siliceous shale or siliceous Sukamto, 1982 andWakita et al, 1994b).…”

Stable platform and dynamic oceanic palaeogeography

“…-Scattered occurrences of Jurassic and Cretaceous mélange yielding bedded radiolarian cherts, as well as limestones, basalt and ophiolitic rock types occur in the Lok Ula Complex on Java, the Meratus Complex on Kalimantan and the Bantimala Complex on Sulawesi (Wakita 2000;Wakita et al 1998. Pessagno & Hull (2002) described Northern Austral Province Oxfordian radiolarians from the Sula Islands, close to eastern Sulawesi.…”

Subsidence and uplift by slab-related mantle dynamics: a driving mechanism for the Late Cretaceous and Cenozoic evolution of continental SE Asia?

“…Rosidi et al 1976). In SE Borneo there are andesitic lavas, tuffs and volcanic breccias that are assigned entirely to the Haruyan Formation by Wakita et al (1998) or placed within the Alino Group by Sikumbang & Heryanto (1994) and Yuwono et al (1988) that are interpreted to represent a volcanic arc suite. These lithologies are approximately Late Aptian to Cenomanian in age (115 -93.5 Ma) (Yuwono et al 1988;Wakita et al 1998).…”