Chap. XII.] 
KODUBITE SETRIES : IGNEOUS ORIGIN. 
247 
occur at any definite horizon in this succession. Sometimes they are 
most closely associated with the calcareous gneisses and sometimes with 
rocks of the khondalite series. 
This prepares the way for the hypothesis that the rocks of the kodurite 
series are of igneous origin intrusive in the khon- 
The kodurite series of dalites and the calcareous gneisses. As will be 
Igneous ongiD. shown later, the chenaical and mineralogical 
composition of these rocks point very strongly to their igneous 
(plutonic) origin. As they have nowhere been seen in contact with 
the gneissose granites it is impossible to say which is the older series. 
If the granites be the older then it is evident that the manganese- 
intrusives must have intruded themselves into the calcareous gneisses and 
khondalites as being less massive rocks. It is evident that with such 
well-bedded rocks as the calcareous gneisses and khondalites, the path of 
least resistance for the intrusions, would be, wherever the rocks were 
dipping at moderately high angles, along the bedding planes. This 
would account for the fact that everywhere the strike and dip, when 
observable, of the manganese-bearing rocks conforms to that of the neigh- 
bouring calcareous gneisses or khondalites. As an example of the way 
in which this intrusion may be supposed to have occurred, two alternative 
hypothetical sections across the Kodur kodurite-belt at Sandananda- 
puram are given on page 1053.1 The second of these sections is construc- 
ted on the hypothesis that the kodurite intrusions took place subsequent 
to the consoUdation of the gneissose granites. It may be thought that the 
very fact of the non-observance of any trespass of the kodurite 
series across the boundaries of the other rocks should be taken as an 
argument against the igneous origin of these rocks. It is therefore 
necessary to notice that — 
(1) very few contacts of the kodurite series with other rocks 
have been noticed^ ; 
(2) the kodurite series has evidently, in at least some cases, 
such as Taduru, Chintelavalsa, and Garbham (see fig. 88, 
page 1088), been subjected to earth-movements whilst 
included between the present wall rocks, and such move- 
ments would tend, especially if the rocks were still deeply 
buried in a region of high temperatures and pressures, 
1 See also Trans. Min. Ged. Inst. Ind., I, p. 90, (1906). 
2 Even the Taduru and Chintelavalsa sections are constructed from the outcrops 
of the rocks and not from any clear section exposed by a stream cutting through the rocks. 
