188 TRANSACTIONS OF THE [APR. 16, 
known to occur outside the limits of the accompanying map, 
but the rock is not a common one in New Brunswick. 
I. GRANITE-DIORITE. 
The typical locality for this rock is a band which rises from 
under surface deposits about a mile and a half west of Indian- 
town, thence, crossing the river, stretches northeast for three 
miles, when it thins out and disappears. It is 2 mile wide at its 
western end, but narrows considerably cone the other. The 
rock is pretty uniform throughout, though coarser to the west 
of the river, and is, as already noted, coarse grained, with por- 
phyritie feldspar crystals. 
Besides the main band, there are several other areas within 
the limits of the map. A narrower band lies about + to 4 mile 
to the north and another a mile or more further, the last being 
an interrupted one along the edge of Kennebecasis Bay, and 
forming for the most part a mere facing for the steep shore cliff. 
At the eastern end it thins out so as to be not wider than a 
heavy dike. These two northern bands are finer grained than 
the southern one, and the porphyritic feldspars are wanting. 
At Poverty Hall Point, on Kennebecasis Bay, is a little area of 
the same rock, apparently a remnant of a much larger mass. 
It is in part quite coarse and porphyritic. To the east of the 
southern band, another wider intrusion comes in, of which only 
the western end is known to the writer. It is coarser than any 
of the others, and contains enough orthoclase to make it a true 
hornblende-granitite. 
Microstructure. It is largely on internal evidence that the 
granite-diorite has been set down as intrusive, for with excep- 
tions to be described later, the contacts between it and the 
surrounding rocks are invariably faulted. 
Fig. 1 represents the appearance of a nearly typical thin sec- 
tion from a little quarry on the Sand Point EID in the south- 
ern band. The rock may be described as follows 
Quartz is present in large amount, forming 4 to 4 of the whole 
mass. It occurs in large grains and is always s allotriomorphiec. 
Plagioclase is in more or less well-defined crystals, rarely en- 
tirely allotriomorphic, except near the edge of the intrusion. 
The crystals sometimes show a zonal structure , but this is not 
very pronounced. 
Orthoclase is much less abundant than plagioclase, with the 
exception noted above. It is almost all in the form of strongly 
zonal crystals, often broken or corroded, averaging + to $ inch 
long. A little orthoclase occurs in small irregular grains, es- 
pecially near the edge of the mass, where the phenocrysts are 
