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Samarinda: And so it begins...

Posted by Lil Stevens on Dec 8, 2010 11:32:36 PM

By Nick Fraser, Christian-Albrechts University of Kiel


Hi, I’m Nick Fraser, a marine geochemist based at Christian-Albrechts University of Kiel, Germany. My main goals on this trip

are to collect microscopic fossils known as foraminifera, which live in a broad range of ocean environments. By identifying key types of foraminifera and later performing chemical analysis on their shells, it is possible to recreate past ocean circulation, an important step in understanding the Indonesian Throughflow in the past.


After a long journey from Bandung culminating in a 4am bedtime, the group arrived in Samarinda on the Island of Borneo, our `base camp´ for the main portion of the fieldwork. Waking up groggy and bleary-eyed, but nonetheless enthusiastic to get into

the field, the group quickly got ready and departed for our first locality- the `Stadium Section´.


Stadium Section.JPG
The whole Stadium section – lots to work with!



This section, a roadcut carved in 2006 to allow access to a sports stadium (the largest in South East Asia) perched imposingly

at one end of the outcrop, provides a range of lithologies. Thick, dark grey mudstones beds, occasionally with the presence of fossilised oysters, are capped with lignite (coal-rich) beds and overlain by channeled sandstone deposits. Lateral variations in thickness of the sandstones are observed, with plenty of well preserved cross bedding, ripple marks and flaser laminations (discontinuous mud laminations within a sandstone bed). A wide-scale cyclicity is noted within the bed structure, indicating a repeated change in depositional environments. A tentative interpretation would be of a delta environment exhibiting sea level cyclicity, but I will leave this for the stratigraphers to comment upon more!


Cross bedding.JPG
Cross-bedded sandstone at the Stadium section



After this, with storm clouds threatening (though they narrowly missed us in the end!) we proceeded further down the section to some larger carbonate deposits. The keen palaeontologists wasted no time in identifying a range of fossils- coral reefs

(branching and platy), molluscs, bryozoans, algae and large benthic foraminifera. This will no doubt be a section many will be revisiting in the coming weeks!


After a brief lunch, we had a short group logging exercise on the first section. Learning to log stratigraphic units is an incredibly useful tool for palaeontologists and geologists alike, and so this exercise proved to be a revelation for many in the group without

a geological background. With the group  beginning to wane in the strong Indonesian heat, we returned to the hotel for some well earned food and sleep, looking forward to further surprises this complex area of Indonesia holds.


Group work.JPG
Researchers interpreting the stratigraphy of the section

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