GEOLOGY FIELD VISIT, WEST JAVA 2010
6TH – 7TH NOVEMBER 2010
Gunung Putri – Jonggol – Ciloto – Rajamandala
West Java, Indonesia
Recently, University of Indonesia – Student Chapter of American Association of Petroleum Geologists was held Geology field trip to West Java on 6th – 7th November 2010. This is an elementary field trip which related to credits on Basic Geology also Structural & Tectonics Geology Class that taught by Mr. Kris Hendardjo. Initially, this field trip planned to be held on 30th – 31st October 2010 and lead by Mr. Kris Hendardjo and Mr. Supriyanto. But actually, due to Mr. Kris Hendardjo’s unhealthy condition, this event had been postponed for a week. As consequences, Mr. Supriyanto could not join Mr. Kris Hendardjo to lead this field trip due to his tight schedule.
This is a closed event which could attend only by students who registered on Basic Geology also Structural & Tectonics Geology Class with Mr. Kris Hendardjo. Our main track for this field trip is Jonggol – Gunung Putri – Ciloto – Rajamandala. There were 47 students who participated to this event, consists of 43 junior students and 4 sophomore students, also assisted by 3 senior students. We split our main track into 2 days, 6th November 2010 to Jonggol (Cipamingkis river) and Gunung Putri; then 7th November 2010 to Rajamandala (consists of: Ciloto, Cipatat, Cibogo, and Citatah).
FIRST DAY (6th NOVEMBER 2010)
Track for the first day is Jonggol (Cipamingkis river) – Gunung Putri – Ciloto. But due to limited time, committee has to postpone track to Ciloto until the second day.
# First Track: Jonggol (Cipamingkis River)
At the time we arrive at Cipamingkis River, Mr. Kris Hendardjo challenges all participants to determine what kind of fault that present there. In order to do that, participants get basic recognition of using geological compass. It is important to practice this, because we have to measure joint direction to know where its main force come from then determining type of fault that present there. We are doing the measurement for 200 times because we need at least hundreds data for using the Rosette Diagram then determine where fault’s main force come from. But, due to limited geological compass, our measurements only reach a hundred data. Nevertheless, finally, we know that Jonggol has a normal fault.
Besides determining fault types, participants also saw some structural geology model and channel deposit. Structural geology that present there are Angular Unconformity, Graded Bedding, and Mud Crack. We are also saw Channel Deposit, a kind of river deposition which caused by archeological river that left behind because of fault events.
Mr. Kris Hendardjo and the three assistants also informed that there is such interesting condition that present in Jonggol but not happens in the last year. There are several boulders in the river, probably caused by flash flood that rolling those boulders from the upper land (mountain).
# Second Track: Gunung Putri
Not by far, participants arrived at Gunung Putri in the late afternoon. Our main target is the primary structure of igneous rocks, which is Columnar Joint that occurred caused by cooling and cracking of nearby dyke. Another focus in this track is learning how to do rocks description, especially igneous rock description, and also focusing in understanding Bowen Series.
SECOND DAY (7th NOVEMBER 2010)
Field track on the second day starts from Ciloto – Rajamandala. Rajamandala itself consists of 3 different location, those are Cipatat, Cibogo, and Citatah.
# Third Track: Ciloto
In Ciloto, participants are focusing in a Landslide phenomenon and how it could occur. Landslides itself could describe as the movement of rock, debris or earth down a slope. There are some probabilities about why it could happen; one other thing is caused by geomorphology of this area. Yes, this is such a steeping area. Other probabilities might be caused by gravity, soil characterization, heavy rainfall, and busy highway in the upper land.
# Fourth Track: Cipatat
From Cipatat village, participants could see almost the whole outcrops of Rajamandala formation. This area is a tertiary marine rock formation, consists of Batuasih claystone formation, Rajamandala limestone formation, Citarum claystone-sandstone formation, and Saguling breccias-volcanic formation. The main morphology of Karst rocky area in Tagogapu-Citatah-Saguling areas is the Rajamandala formation.
Mr. Kris Hendardjo told us about the Rajamandala history in such interesting way. Another focus line for participants is learning about orientation, which is determining our current location on geologic map by shooting Guha and Balukbuk Mountain using geological compass then plot its azimuth in geologic map.
# Fifth Track: Cibogo
We are focusing on spheroidal weathering in here, which is a chemical process that occurs in large blocks of rock. Onion-like layers form as the joints of the rock wear away. The result is jagged layers of rock, rounded edges and a concentric-like weathering. We also saw Travertine in Cibogo river, where the only way to reach to is by using rope. Travertine is a form of limestone (carbonate) deposit by mineral spring. Travertine often has a fibrous or concentric appearance and exists in white, tan, and cream-colored varieties.
# Sixth Track: Citatah
In Citatah, participats could saw the fault boundaries between Rajamandala limestone formation and Batuasih clay stone formation. Again, Mr. Kris Hendardjo challenges us to determine its fault boundaries. Complex mixed area between Rajamandala and Batuasih made fault boundaries in here is more difficult to determine than fault boundaries in Jonggol. But finally, we could see its fault boundaries quite clearly, which is lying from southwest to northeast, well-marked by main highway.
Participants are also enjoying in finding fossil in limestone of Rajamandala formation. It was quite difficult, but some participants finally found some plant fossil.
Overall, this elementary field trip is very helpful especially for the sophomore and junior of Geophysics UI students in understanding basic geology, structure, and tectonics in such fun way. Hopefully, someday UISC AAPG could facilitate every field trip with sufficient number of geological equipment; such as geological compass, hammer, and magnifying glass. So, all participants could effectively practice all geological concepts that related to.