4 A SKETCH OF THE GEOLOGICAL STRUCTURE 



We find an answer to this in the second type of mountain 

 ranges, the limestone hills. These are part of a wide-spread 

 formation of limestone and calcareous clay-slates that are 

 known to he of Carboniferous or perhaps Permo-Carboniferous 

 age, as far as the exposures in Pahang are concerned, and 

 which are probably of the same age elsewhere in the Peninsula. 

 The nature of these rocks, the abundant remains of shells, 

 corals and crinoids in the limestone where it is not crystalline, 

 and the fine grain of the calcareous clay slates, point to their 

 having been deposited farther from the shore than the 

 Gondwana rocks and in a deeper, clearer sea. We also know 

 from volcanic rocks associated with these calcareous rocks, 

 that the sea floor during this period was from time to time 

 torn open by eruptions and covered with layers of ash and 

 lava. 



This takes us one step farther back, and could we accept 

 the statements that have been made by some writers about 

 Archaean rocks occurring in the Peninsula, we should be able 

 perhaps to glean a wealth of information about land and sea 

 prior to the Carboniferous period, but unfortunately our 

 knowledge, but recently acquired, of the pre- Carboniferous land 

 and sea is small, although of extraordinary interest. Before 

 discussing this, however, there are other points that claim at- 

 tention. 



Two types of mountain ranges give us information about 

 the earlier history of what is now the Peninsula, the third 

 type, the big granite ranges, carries us on to later times. The 

 granite of all the Peninsula ranges is, as far as we know, 

 younger than the Gondwana rocks and the calcareous rocks, 

 it is but again, as far as we know, the youngest rock in the 

 Peninsula with the exception of a few later igneous dykes 

 intrusive into it; and the recent surface deposits. In geological 

 chronology we cannot fix its date exactly, but without giving 

 the evidence in detail it may be said to be probably cretaceous. 

 As the granite is the latest, with the above reservation, of the 

 rocks to enter into the composition of the Peninsula, it would 

 be safe to assume that the events which led to its intrusion 



Jour. Straits Branch 



