Exploring Precambrian to Lower Paleozoic Carbonates in Indonesia: Lessons from their Modern Analogues of Stromatolitic Reefs In the SatondaIsland Crater Lake, North Sumbawa

Proceedings, Indonesian Petroleum Association
Thirty-Fourth Annual Convention & Exhibition, May 2010

Exploring Precambrian to Lower Paleozoic Carbonates in Indonesia: Lessons from their Modern Analogues of Stromatolitic Reefs In the Satonda Island Crater Lake, North Sumbawa

Awang Harun Satyana*, Nugrahani Pudyo*, Heryadi Rachmat**, Agus Hendratno***, Salahuddin Husein***
* BPMIGAS
** Nusa Tenggara Barat Province
*** University of Gadjah Mada

Abstract
Newly acquired seismic data in the Arafura Sea to the south of Aru Islands, Eastern Indonesia reveal the presence of very thick Pre-Cambrian to Paleozoic beds. Regional correlation with the Paleozoic and Pre-Cambrian proven sections in offshore and onshore areas of Australia indicate that the Arafura Sea may also have these proven sections.

One of the potential sections in the Arafura Sea come from dolomitic carbonates correlatable to Cambrian-Ordovician Goulburn Group and Pre-Cambrian (Middle Proterozoic) McArthur Group in Australian areas. The carbonates are considered to be composed of blue-green algae (cyanobacteria) binding calcareous sediments forming microbial mats commonly known as stromatolites. Stromatolites were the dominant reef-building organisms during the Pre-Cambrian to the Lower Paleozoic.

Exploring stromatolites for petroleum is something new in Indonesia. We need a modern analogue of these deposits to study sedimentation model and reservoir characteristics. Fortunately, although there are no many places on modern Earth for development of stromatolites due to requirements of extreme environment (isolated body of water, high alkalinity-salinity, soda ocean), there is a place in Indonesia where modern stromatolites grow. It is the SatondaIsland, a small remnant volcanic island located to the north of Sumbawa at the FloresSea. The island has a crater lake filled with seawater. Because the lake has lost all direct connections with the surrounding sea due to tectono-volcanic events, the lake environment has changed to be extreme. Stromatolites grow within the lake.

Our recent field work there found calcareous reef-like structures composed dominantly of blue-green algae forming mats of in-situ calcifying microbe of cyanobacteria. We studied the geology of the lake and sedimentation as well as reservoir characteristics of living and dead stromatolites. The data we acquired, analyzed, and interpreted on stromatolites of the SatondaIsland may significant for exploring their ancient counterparts beneath the Arafura Sea.

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