Facies analysis and palynology of upper Miocene to Pliocene sediments exposed at Timika–Tembagapura section, Papua, Indonesia

Abstract

This study reports on the recent sedimentological and palynological analysis of the rock unit outcropping at the road between Timika and Tembagapura from KM 73 to KM 92, Papua, Indonesia. The unit has been previously regarded as being late Proterozoic to Permian in age. Sedimentary facies analysis suggests a non-channelised deep-lacustrine slump and debris-flow dominated environment consists of delta front, slump, debrite, turbidite and lacustrine mud deposits. New palynological data designated a late Miocene to Pliocene age for the analysed samples, based on the occurrence of Nothofagus brassii type pollen, Stenochlaena milnei type spores (Stenochlaenidites papuanus), Dacrycarpus pollen (Dacrycarpites australiensis) without Proteaceae pollen (Proteacidites spp.). The palynomorph assemblage is interpreted to consist of two main groups: autochthonous and allochthonous components. The autochthonous component is dominated by freshwater algae with the co-occurrence of diatoms, freshwater sponge spicules, Pseudoschizaea, testate amoebae and aquatic plants. The allochthonous pollen component is derived from five major vegetation types: lowland rain forest, lower montane forest, upper montane forest, swamp forest and scrub/grassland. The palynomorph assemblages support the notion of a fluvial–lacustrine depositional environment in an inland position away from marine influences. Furthermore, the studied rock unit is considered to be deposited in the piggyback basin between Papuan Fold and Thrust Belt during the Central Range orogeny. KEY POINTS The section has been previously regarded as being late Proterozoic to Permian in age. New palynological data indicate a late Miocene to Pliocene age for the analysed samples. Sedimentological features and palynomorph assemblages suggest a fluvial–lacustrine depositional environment in an inland position away from the influence of the sea. The studied rock unit is considered as being deposited in the piggyback basin between Papuan Fold and Thrust Belt during the Central Range orogeny.