18 November 2016,
Here it comes to the main aim of the trip, outcrops! We were asked to gather and have breakfast at the resort's restaurant and departed around 9 in the morning to our first ever location of the trip, Pulau Langgun!
For your information, Langkawi Island consists of a group of 104 islands in the Andaman Sea which is approximately 30km off the coast of northwestern of Peninsular Malaysia. It is the most interesting and strategic location for geology studies since it consists of all three major types of rocks which are igneous, sedimentary and metamorphic. As for the first location, Pulau Langgun, it is made up from Singa formation for which those that overlying the folded strata are red mudstone and interbedded quartize of the Langgun Red Beds.
Here are some of the pictures taken on the island:
One of the rock that can be found in Pulau Langgun is shale which is a source rock. It is a rock that is hard, contains organic material such as oil and gas, has fine grain, dark in color and structureless. It has two types of shale in which some are contain of quartz while some are calcite. Besides, fossils can also be found in shale.
| Our lecturer was explaining how the rocks are formed and its properties |
| The picture shows a fault in the rock |
Fault often happens because of tectonic effect. Convergence and divergence can cause the stone to be uplifted to onshore from offshore and this is how most of the rocks can be found onshore nowadays.
Next, sedimentary rock is formed when pressure and high temperature is inserted. There are two types of sedimentary rocks which are clastic and non-clastic. Some examples for clastic rock are sandstone, conglomerate, siltstone and shale while non-clastic are limestone and coal. Sometimes, shale and limestone can be alike and to differentiate and determine these two rocks, acid is used. Bubbles will form if it is a limestone because of the presence of calcium carbonate and it is vice versa for shale.
Secondary sedimentary happens only at the surface of the rock. Tafoni structure can also be found in Pulau Langgun which is a honeycomb-like structure that formed by salt dessication, particularly on exposed thick shale and fine-grained sandstone beds.
[MORE TO COME, TO BE CONTINUED...]
