Abstract:
The contact boundary between two major lithological units of sri lanka known as
the Highland Complex and the Vijayan Complex is one of the most striking features of
geology of Sri Lanka. An interpretation of Bouguer gravity anomalies has been carried
out to produce a detailed three - dimensional model for the crustal structure beneath this
boundary as well as the central highlands of the country assuming the Highland and the
Vijayan Complexes of rocks have two different densities. Further, it has been assumed in
this study that the Highland Complex is underlain by the Vijayan complex which acts as
a tectonic basement to the Highland Complex. Results show that the maximum thickness
of the Highland Complex is 7 km and the maximum thickness of the crust over this
region is 36 km. The crustal thickness is comparatively higher beneath the central
Highlands and beneath the boundary between the Highland and the Vijayan rock units
indicating the presence of a crustal root. A study of the isostatic equilibrium of this
region has also been carried out and found that the region is more or less in the
equilibrium.
