This EarthCache will bring you to Gunung Rapat, the 5th highest of 45 limestone hills in Kinta Valley.
Type of EarthCache: Fold feature.
Gunung Rapat
At 381 m high, Gunung Rapat is the fifth highest of the 45 limestone hills found in the Kinta Valley, Perak, Malaysia (Malayan Nature Society, 1991). It is approximately 5 km south of Ipoh.
Geology of Gunung Rapat
Ingham and Bradford (1960) classified Gunung Panjang as in the Calcareous Series that formed limestone hills consisting almost entirely of crystalline limestone, which is lacking in fossils, of possible Permo-Carboniferous age (Figure 1). Later work by Suntharalingam (1968) on fossiliferous limestone beds in Kampar established an age range of Silurian to Lower Permian for the Kampar Limestone. Currently, through correlation, the Kinta Limestone is taken to be of the same age as the Kampar Limestone giving a possible age of Gunung Panjang as Silurian to Lower Permian.
Figure 1: Geological map of Kinta Valley - Gunung Rapat
(After Ingham and Bradford (1960)
The youngest dated Palaeozoic sedimentary rocks in the Kinta Valley are Upper Permian. K-Ar dating of the Kuala Dipang granite gives a radiometric date of 232 ± 10 Ma, indicating an end-Permian intrusion (Snelling, 1967) that preceded the intensive deformation of the limestone in the Kinta Valley in the Late Permian. Triassic sediments are absent in the Kinta Valley (Lee, 2009).
Because of this intensive deformation many types of fold can be seen in the limestone hills of the Kinta Valley as evidences of the tectonic event. A number of these folds can be seen in Gunung Rapat.
Types of Fold
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved because of permanent deformation.
There are various types of fold:
- Anticline: linear, strata normally dip away from axial centre, oldest strata in centre.
- Syncline: linear, strata normally dip toward axial centre, youngest strata in centre.
- Antiform: linear, strata dip away from axial centre, age unknown, or inverted. Unlike an anticline, antiform is a purely descriptive term for any fold that is convex up but the age relationships (i.e. younging direction) between various strata are unknown.
- Synform: linear, strata dip toward axial centre, age unknown, or inverted. Unlike a syncline, synform is a purely descriptive term for any fold that is concave down but the age relationships (i.e. younging direction) between various strata are unknown.
- Dome: nonlinear, strata dips away from centrw in all directions, oldest strata in centre.
- Basin: nonlinear, strata dips toward centre in all directions, youngest strata in centre.
- Monocline: linear, strata dip in one direction between horizontal layers on each side.
- Chevron: angular fold with straight limbs and small hinges.
- Recumbent: linear, fold axial plane oriented at low angle resulting in overturned strata in one limb of the fold. For image of recumbent fold, see Geologic Structures.
- Slump: typically monoclinal, result of differential compaction or dissolution during sedimentation and lithification.
- Ptygmatic: Folds are chaotic, random and disconnected. Typical of sedimentary slump folding, migmatites and decollement detachment zones. See link for further explanation and description on ptygmatic folds.
- Parasitic: short wavelength folds formed within a larger wavelength fold structure - normally associated with differences in bed thickness. See further explanation and examples of parasitic folds in link and link .
- Disharmonic: Folds in adjacent layers with different wavelengths and shapes. See link for further explanation and example of disharmonic folds.
- A homocline involves strata dipping in the same direction, though not necessarily any folding.
How to claim this EarthCache?
From the EarthCache coordinates, look southwest towards the limestone hill. Examine the hill face for a tectonic structure. Identify the type of fold you observe. From Additional Waypoint TSGR2, look north towards the limestone hill face. Examine the hill face for tectonic structures. Identify the types of fold you observe. From Additional Waypoint TSGR3, look at about 30o towards the limestone hill face. Examine the hill face for a tectonic structure. Identify the type of fold you observe.
Send me the following;
1. The text "GC7CJH0 Gunung Rapat - Tectonic Structures" on the first line.
2. The answers to the following questions;
- Name the type of fold you observed at the EarthCache coordinates.
- Name the types of fold you observed at Additional Waypoint TSGR2.
- Name the type of fold you observed at Additional Waypoint TSGR3.
3. Provide a photo of yourself or a personal item to prove you have visited the site.*
References
1 Ingham, F.T. and Bradford, E.F., 1960. The geology and mineral resources of the Kinta Valley, Perak. Federation of Malaya Geological Survey District Memoir, 9, 347 pp. 2 Lee, C.P., 2009. Palaeozoic Stratigraphy. In: Hutchison, C.S. & Tan, D.N.K. (eds.). Geology of Peninsular Malaysia. UM & GSM, Kuala Lumpur, Malaysia, 479 pp. 3 Malayan Nature Society, 1991. Conservation Assessment of Limestone Hills in the Kinta Valley, 202 pp. 4 Snelling, N.J., 1967. Age determination Unit. Summary of results from the Pacific and S.E. Asia. Institute of Geological Sciences Annual Report for 1966, 32-33. 5 Suntharalingam, T., 1968. Upper Palaezoic Stratigraphy of the area west of Kampar, Perak. Geological Society of Malaysia Bulletin, 1, 1-15.
* Effective immediately from 10 June 2019, photo requirements are permitted on EarthCaches. This task is not optional, it is an addition to existing logging tasks! Logs that do not meet all requirements posed will no longer be accepted.
For additional information, visit; Geosociety.org, Geocaching.com Help Center and Geocaching.com Forum.
Finding the answers to an EarthCache can often be challenging, and many people tend to shy away from these caches because of this. However, it is my opinion that geocaching is also meant to be a fun family experience that simply aims to introduce interesting and unique locations such as this one. Flexibility on logging requirements, however, can only be applied if it can be established that you have actually taken the time to visit the site. For this reason, a proper log describing your adventure accompanied by a good number of photos would be much appreciated.
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