Abstract:
In the Earth’s history, there were five major glaciations, namely, Huronian (2,300 Ma),
Cryogenianor Sturtian-Varangian(850-635 Ma), Andean-Saharan (460-430 Ma, Karoo (360-260 Ma) and
the Quaternary (2.58 Ma to Present) that occurred between 2,300 Ma and 0.0114 Ma. It is revealed that
Gondwanaland emerged between the Huronian glaciation (2300-2100 Ma) in the Paleoproterozoic Era
and the Andean-Saharan glaciation (460-420 Ma) in the Early Paleozoic Era. During this time, most
continental land masses were clustered in the southern hemisphere, and Sri Lanka was part of the
Gondwanaland landmass comprising present day Africa, Madagascar, India and Antarctica. Within the
Ordovician (485.4-445.2Ma) to Permian Periods (299.0-254.2 Ma) there were signs of the breaking up of
Gondwanaland resulting in the severing of India and Sri Lanka together and subsequently Sri Lanka from
India. By end of the Permian Period (260 Ma) Karoo Glaciation had ended and the present Mannar Basin
developed within a deep canyon (about 4-7 km deep) on the Precambrian basement.
Although the island of Sri Lanka presently lies in the Indian Ocean between 5º 52´N-9º 54´N and
79º 30´E-81º 55´E, to the southwest of Bay of Bengal and southeast of Arabian Sea, it was positioned
within 67ºS-65ºS and 34ºE-43ºE during the Lower and Middle Jurassic Era (201.3-166.1 Ma). Huge rocky
blocks (erratic boulders) have been transported to different places by continental ice sheets due to climatic
changes in the Permian, Triassic and Jurassic Periods, but erratic pebbles (2 to 8 cm or more in size) and
streams fed deposits have been transported by glacifluvial processes. These glaciofluvial processes
occurred on four occasions during the Jurassic Period and Eocene, Miocene and Pliocene Epochs on Sri
Lankan landmass, which fallowed the climatic changes and sea level fluctuations that broke up the
sedimentary beds, initiating establishment of the present topography and structural configuration. As a
result, the earlier sedimentary deposits were obliterated from greater part of Sri Lanka. During the
Quaternary Period the erosional rate increased and the resultant erratic boulders along with
glaciofluvialdeposits can still be found on “Planated Surfaces”of Sri Lanka.
