1 - Cochin University of Science and Technology

opposite
origin of
features
valleys
cited to
flowing drainage systems as responisble for the
the Gap. The tectonic- framework, geomorphic
and development of soil types typical of river
in the Gap area as reported by the authors, were
reiterate this line of argument. Rejuvenation
features observed along the river courses of the three
physiographic horizons identified within the Gap area were
taken as probable indications of similar rejuvenation of the
Gap proper.
Recent
correspondence
investigations point to
between P-T data on rocks
the lack of
lying south and
north of the Palghat-Cauvery 'shear zone' (Harris et aI,
1982; Janardhan et aI, 1982; Raith et aI, 1983; Chacko et aI,
1987) facilitating arguments in favour of its being a
tectonic boundary between two distinct terranes within the
southern shield (Ramakrishnan, 1988), a view which concurs
with the gravity data (Mishra, 1988) also.
Drury et aI, (1984) envisaged it as a zone of strong E-I,J
striking planar tectonic fabric connected to the N-S
system of the Eastern Ghats by many arcuate shears
thrust
at its
eastern extremity (Drury & Hol t, 1980). Its relation to the
Eastern Ghat mobile belt was also emphasised by curving of
the N-S fabric of the northern block into the E-I,J shear
system, which is consistent with an E-I,J crustal shortening
(Mukhopadhyay, 1986; Reddi et aI, 1988) and a dextral sense