Welcome to Pantai Pasir Tengkorak, a lovely pocket beach with many geological features.
Type of EarthCache: Denudation / Tafoni.
Pantai Pasir Tengkorak is a pocket of fine white sandy beach in between rugged rocky outcrops comprising sandstone and shale. The gently dipping and warping sandstone and shale belong to the upper part of the Machinchang Formation. The sandstone contains some excellent internal cross-bedding and surficial ripple marks, while the interbedded sandstone-shale exhibits more interesting load related sedimentary structures such as load cast, flame structure, convoluted bedding, fluid-escaped features and truncated sandstone lenses.
Unique are the salt dessication originated honeycomb-like structures called tafone, particularly on the exposed shale. The relief of the tafone reflects the maturity of the structure while the shapes of the tafone usually depend on the joint patterns and the direction of the sea-sprays.
Toward the east, the beach is commonly rocky and pebbly. The rocky beach is formed by several erosion platforms. The geology is mainly made up of gently dipping sandstone with subordinate shale, in places severely faulted.
The sandstone contains some excellent cross-beds and ripple marks. The rocky beach exhibits several ancient wave erosional features including vast abrasion platforms with several elevated sea-caves, several metres above the present sea level. The formation of the sea-caves is clearly controlled by the presence of several nearly vertical fault planes, both of normal and reverse faults.
Other attractions to the beach are the diversity of pebbles distributed within pockets of pebbly beach and the presence of iron-filled fractures probably related to the emplacement of the quartz veins.
Tafoni
There is no real consensus on how tafone (plural: tafoni) are formed. Several theories have been presented to explain tafoni formation, including: freezing-thawing (unlikely in Malaysia), wetting-drying, and salt weathering. The most common explanation to explain the presence of tafoni in coastal areas is honeycomb weathering, a form of salt weathering. Honeycomb weathering occurs when salt collects on the surface of permeable rocks, deposited by ocean waves, mist, or wind. As the saltwater evaporates, the salt remains behind working its way into the rock pores, where it crystallizes and pushes the pores further open. These enlarged rock pores become susceptible to additional weathering, and after a significant amount of time, becomes noticeable in the form of tafoni. To explain tafone in coastal areas, it is believed that mollusks and other marine life may also initiate tafoni. They attach themselves to the host rock and create small holes to extract minerals. Eventually the mollusk, or other organism, drops off., leaving the hole exposed to the elements.
How to claim this EarthCache?
Send me the following;
1. The text "GC81GQA Pasir Tengkorak - Tafoni structures" on the first line.
2. The answers to the following questions;
- What are these tafoni made of, salt or rock? Explain your answer!
- When you knock on a tafone layer, what sound does it make?
- How do you see these tafoni evolve?
3. Provide a photo of yourself or a personal item to prove you have visited the site.*
References
* 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.
