PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 225 



Conglomerate. Diabase.] 



No. 155. CONGLOMERATE. ( Red 2)ebbles. ) 



The rock of Palisade rock No. 2 continues easterly with irregular dip, and is seen to contain an intrusive 

 sheet of diabase at about half a mile from the rocky sharp point formed by it. Then succeed, easterly, alterna- 

 tions of trap and amygdaloid, which continue to an exposure of this conglomerate, which dips north at an angle 

 of 8 or 10, the exposure being thirty feet high. The stones are occasionally a foot in diameter. Toward the 

 east it is metamorphosed by intruded diabase. 



Ref, Annual Report, ix, page 39; Annual Report, x, page 42. 



Some of the pebbles are of brown-red amygdaloid, and some are of a grit- 

 rock, made up of the same materials as the pebbles in No. 149, viz.: of clastic grains 

 of apobsidian. The larger pebbles are of this latter sort. Indeed, the large majority 

 of the pebbles are of a clastic rock, apparently a volcanic grit; a calcite cement runs 

 through it. This conglomerate may have been accumulated by some abrasive agent 

 operating .on the upturned beds of alternating trap and amygdaloid, such as the 

 Agate Bay series, since in the amygdaloids of that series, and in connection with 

 other amygdaloids further west, a frequent ingredient is a clastic accumulation of 

 devitrified glass. There is in No. 155, as collected, no evidence of the immediate 

 presence of the Palisade rock itself, but the devitrified glass, apobsidian, has supplied 

 a large ingredient in accord with the stratigraphic hypothesis under which the rocks 

 of the lake Superior shore have been divided into Cabotian and Manitou, which 

 requires that the quartz-porphyries, etc., be older than this break and should have 

 furnished debris to such a conglomerate. (See No. 155A.) 



No section. 



Af/e. Puckwunge. N. H. w. 



No. 155A. RHYOLYTE CONGLOMERATE. 



The eastern extremity of No. 155, where hardened and blackened by an intrusion of diabase. Were it not 

 for the visible continuance of the lines of stratification from No. 155 into this it would not be noticed that thi* 

 is really a conglomerate without close inspection. 



Kef. Annual Report, ix, page 40. 



ir/'g. The pebbles are drawn and flattened, but between them is a finer matrix 

 of different composition. Some of the clastic elements are apparently from a fine 

 shale, and one large one is a plain quartz- porphyry. 



No section. 



Age. Puckwunge. N. H. w. 



No. 156. DIABASE. 



East of Baptism river. A massive, heavy rock, with a considerable ingredient of red, with jointed and 

 contorted lamination, or in heavy, massive beds. It has much aniphibole and much magnetite. In other places 

 it contains orthoclase and laumontite, the latter mineral causing an easy, natural disintegration. This is termi- 

 nated eastwardly by a doleryte dike fifty feet wide. It seems to be partly derived from the igneous rocks them- 

 selves, mixed in eruption with fused portions of the sedimentaries. 



Ref, Annual Report, ix, page 40; Bulletin ii, page 79. 



Mil/. There are two hand samples. The first is a coarse, crumbling rock com- 

 posed of pinkish and gray feldspar and a dark mineral with glistening metallic 



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