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ROCKS OF THE UPPER ST. CROIX. 247 
Professor Pumpelly on page 32, and identical with stratum 108 of the Eagle river 
section. It is found in the N. E. 4 of Sec. 14 and the N. W. 4 of See. 27, T. 44, R. 15 
W., the N. W. 4 of See. 28, T. 43, R. 14 W., and at the falls on Chase’s brook, in the 
N. E. 4 of the.N. W. 4 of See. 16, T. 42, R. 15 W. 
The first three of these may be joined by a nearly straight line about 12 miles in 
length, whose course will be about N. 48° E., or nearly the average observed strike. 
If this line be projected it will pass to the southeast of the melaphyr exposure on 
Chase’s brook, and, if extended in the opposite direction it will pass about an equal 
distance from an outerop of precisely similar rock found on Moose creek, in the N. E. 
4 of the N. W. 4 of Sec. 2, I. 44, R.13 W. It would appear highly probable, then, 
that the first three exposures belong to the same stratum, and that the remaining two 
represent a lower bed. This is confirmed by the existence of a similar melaphyr near 
the center of the west line of the N. W. 4 of See. 21, T. 43, R. 14 W., and also one in 
the S. W. 4 of Sec. 10, either of which might readily be referred to the lower bed, 
though it is not so apparent that both could. Entering more into detail, we observe 
that the outerop of the melaphyr in the N. W. 4 of the N. E. 4 of See. 27, T. 44, R. 
13 W., rises only about 10 feet high and forms the bank of a creek. The rock 
agrees completely with the description of the typical Keweenaw rock previously 
referred to. The formation crops out quite continuously along the stream as far as 
the forks in the N. E. 4 of Sec. 28. Here it is found to be dark, coarse-grained, rather 
soft, containing much chlorite, and crumbling readily on weathering, and no longer 
possesses the distinctive melaphyr characters. On the line between Sees. 22 and 27 
we, however, find the typical melaphyr again. 
Following the line of strike into the S. E. 4 of the N. E. 4 of Sec. 14 of this 
township (T. 44, R. 13 W.), we find on Moose creek the same melaphyr. Its dip 
here appears to be about 18° to S. 309 EK. A few yards below the ledges are traversed 
by veins of epidote, with some indications of copper. 
The rock is here very amygdaloidal, carrying chlorite as a cell-filling, dip 20°. A few 
rods below we find a heavy, firm, fine-grained, dark-greenish, diabase-like rock. The 
surface of this presents very finely preserved glacial grooves, having a direction S. 15° 
W. Some are wide and shallow, while others are narrow, sharply-defined hair lines. In 
the N. W. fof the S. E. 4 of this section there are also some small ledges of fine-grained 
diabasoid rock, and in the S. W. 4 of the S. E. 4 of the section we encounter the con- 
glomerate before described. Following up Moose creek to Sec. 2, we find in the N. W. 
tof the S. E. } first a very hard, fine-grained, nearly black diabase, above which, 
about 100 yards, there appears a coarser crystalline diabase and diabase pseudo- 
amygdaloid, containing patches of epidote, quartz and considerable calcite, though the 
rock is not generally amygdaloidal. There are to be found occasionally specks of mala- 
chite. The dip measurements were 17° and 2098S. E. The ledges are much fissured 
and broken in all directions. Near the center of the section, low ledges, along the 
west side of the stream, exhibit a coarse-grained rock, somewhat resembling the mela- 
phyr found farther up the stream, presently to be described. Above this in the N. W. 
4 of the section, there first appears a diabase of medium grain and greenish-gray color, 
and about 100 yards farther up, on the left bank of the stream, a low outcrop of soft, 
very dark, diabase pseudo-amygdaloid, containing chlorite, quartz, orthoclase and 
1 See Geological Survey of Michigan, 1869-1873, Vol. I, Part II, p. 186. 
