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Identifying Geological Structure of Raja Mandala Formation
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Day One : Class Session, February 15th 2013.

The class session began at 08.00 WIB.  Hardcopy material and map were distributed to the participants.  The lecturer was Ir. Kusnadi Sumantri and the theme of class session is about identifying geological structure of Rajamandala Formation on topographic map. This session was an introduction and familiarization to the geological structure with fault as the main focus with all its indication so the participants were able to applied it on the site.

It was explained that fault is related to the geology structure, and the geology structure related to the tectonic.  Also the lecturer elaborate about tectonic plate is related to structure and lithology, where lithology can be recognized by its contour shown in the map. The tectonic plate is important for helping to recognize the plate direction in contour map (Java Island for an example with a normal concept force  from west to east) and what kind of plate that influenced it.  Because tectonic plate produce landform, whereas the landform that are now on the map will have syncline, fault and others.  Also the lecturer explained the process that work on earth such as gradation (divided into aggradations and degradation), diastrophism and volcanism.  There are no result from the structure of volcanism result because there were recently happened.

Then, Ir. Kusnadi Sumantri also said a way to detect structure in topographic map using the overlay method with geological maps. He also explained the difference between the strike fault and strike slip fault, where a strike fault is parallel to the direction of layer, whereas a strike slip fault move in the same direction with the layer field. He also gave tips for searching for outcrop area less obsolescent by looking for   narrow and dense  contours on topographic map, for the participants to find and measure the strike easier. In addition it was also explained that the fault breccias often found in the fault zone which is characterized with a lot of fracture.

The session ended at 10.45 WIB. and continued with technical meeting session. At this session, the committee explained the list of equipment that needed on the field. After reading the closing prayer, the event ended at 11.00 WIB.

Day Two : Field Trip, February 16th 2013.

Because of the river condition was flooded, The field trip had to moved  location  from Raja Mandala, West Bandung District, West Java Province, Indonesia  to Cibadak and Cikembar, Sukabumi District, West Java Province, Indonesia which still has similar formation, that is a Rajamandala Formation.
 
All participants and committee are expected to be ready in front of Building D, Campus A, Trisakti University at 5.30 WIB.  After all the participants arrived, the committee started with some technical preparation and divided the participants into groups (9 groups) and distributed chisel and compass to each group.

At 07.00 WIB we departed by bus, the weather was cloudy but fortunately the trip was uneventfully and by 10.52 WIB, we arrived at our first destination, Sukabumi Police Resor / Cilandak Sector.  After all groups introduced to their Field Supervisor (Assistant), the trip began at 11.12 WIB by walking to the first observation area.

By 11.16 WIB we arrived at the observation area, Gadung Mountain, Cikembar, Sukabumi District, West Java Province, Indonesia. The mountain is known to have fault breccias with the direction near west to east direction and tectonic transport from the south.

With the guidance from the Lecturer about the observation area condition, we then continue to do some plotting and mapping helped by the field supervisor.  The plotting and mapping took about 5-10 minutes and then continued the trip to the second stop site.

We arrived around 12.04 WIB at the second observation area.  After short briefing from the Lecturer about how the fault formed, all participants started to do the strike and dip  measurement from the fault zone found. Then moved to the next location, the 3rd stop site.

The participants arrived at the 3rd stop site at 12.34 WIB. In this area we found the drag reverse around the area with normal fault release and also many slicken lines found on the secondary structure formed from the fault in the footwall area closed to the fault zone. The lithology is recognized as zeolith. Then we continued to the fourth stop site and arrived around 12.52 WIB.

In the 4th stop site, gauge was found on the side of the fault as resulted from the fault movement that happened because of the resistance to the force. The gauge is result from the fault friction itself. After that, all participants continued to the fifth site.

The participants arrived at the fifth stop site at 13.05 WIB. This location is only located 15-20 meters from the previous stop site. We also found the gauge at the hanging wall of the fault. After that, the participants returned to the site where we started from at 13.15 WIB to had lunch break.

The lunch break ended at 14.10 WIB, then we continued the trip to the site of the second observation area by bus. The bus departed at 14.15 WIB and arrived at the second destination at 14.10 WIB.

In this observation area, we found microfold (drag fold) that was predicted caused by slump or tectonic, and also fault breccias on the microfold resulted from the drag movements of the transform fault. We also found some area of the outcrop that affected by shearing. Then participants conducted measurement of the line structure of the microfold using compass and clipboard. After that, the participants continued walking to the next observation area.

At the third observation area we  found fault breccias as resulted from the transform fault and also slicken lines as resulted from reverse fault.

At the end of the fieldtrip, the lecturer made an evaluation of the whole trip and gave a closing speech. There was also a momento session followed by photo session, then the field trip was ended by pray together. After that we headed back to Jakarta.

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