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CLOSE TO NATURE
THE FORMATION OF LIMESTONE CAVES IN KINTA VALLEY
Most of the sedimentary rocks of the Ipoh area were formed during this latter period, when the area was occupied by a warm sea in which marine animals were probably abundant. Occasionally the sea became muddy when sands and muds were deposited but these periods were brief and clear water conditions prevailed for the greater proportion of the time.
Outstanding exposures of this limestone can be seen today forming not only the bedrock in many of the open-cast alluvial tin-mines, but also picturesque hills indicate that an old, flat limestone surface once lay more than 1000 feet above the present valley floor, but that continual erosion during million of years has gradually worn away most of the limestone leaving the precipitous hills as remnants of the former large mass.
Discovering another gap in the record during Triassic times (225-180 million years age) suggested that any sediments which were then deposited have since been completely removed by erosional processes.
During the early time of Jurassic period (180-135 million years age), large masses of very hot molten granite were intruded into the rocks which then occupied the area. During the intrusion of this granite great pressure were developed which resulted in the overlying limestone being folded, crumpled, faulted and in some places shattered. At the same time the heat given off from the cooling liquid granite caused the limestone to slowly change to a hard white marble. These replacements contained valuable minerals that formed very close to the contact between the granite and the limestone, a fact which for many years has been well known to the local miners.
From Cretaceous times to the present day (roughly 135 million years), the original rocks in the Ipoh area have been subjected to almost continual erosion and slowly worn away. With the removal of the limestone, the underlying granite was gradually exposed as two large ridges, one west of Ipoh, forming the Kledang Range and the other to the east, forming the Main Range. That made Kinta Valley, sandwiched between two granite mountain ranges, pressed as one mammoth limestone slab, stretching from Padang Rengas in the north to Tapah in the south. The limestone slab has been slowly eroded away from the higher granite country, leaving only isolated limestone remnants protruding above the alluvial plain.
 From the middle of Quaternary times to the present day (roughly 35 million years) weathering of the granite has produced abundant detrital gravel and sand which has been carried down from the hills by streams and deposited on the flat valley floor.
The valuable metalliferous minerals, originally contained in the veins of the limestone and in the granite, also have been carried downstream and deposited with the sand and gravel. These loose, superficial deposits on the valley floor contained the concentrations of tin-ore which have been the prime reason for development of the Kinta Valley in general/particular.
Ipoh today is the centre of a flourishing mining industry based on the production of tin-ore, iron-ore, brick clay and road metal. There is also abundant limestone available for cement making.
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