PHYSICAL ASPECT OF CAMBRIAN ROCKS IN EASTERN CANADA. 255 
region the prevalence of volcanic deposits, or of red and green 
mud beds, in the initial period of Cambrian time. If the former 
are not actual lava flows, or the cores of old volcanic cones and 
ridges, they are the compacted ashes, mud and stones from such 
a source. 
Resting on these volcanic deposits, though sometimes inter- 
calated with them, are beds of sand and mud that easily show 
their relation to such a source as the volcano, by the fact that 
this sand consists largely of feldsphatic particles, while the mud 
beds are pale green, or red accumulations of volcanic dust, that 
have fallen into or been swept into the sea. Hence it would 
appear that while the first volcanic eruptions occurred over land 
surfaces, the land soon sank, and the later ones were thrown 
into the sea. It is in the levigated volcanic material thus thrown 
into the sea, or swept into it by rivers, that we meet with the 
earliest organic remains of the Cambrian time. These levigated 
deposits are chiefly in the Etcheminian terrane, and contain 
a very ancient group of Cambrian organisms. They also 
exhibit a cycle of deposits corresponding to that of the St. John 
terrane above them, for they have in the middle coarse sandy 
sediments, that separate two groups consisting largely of mud- 
beds ; of these the lower has conglomerates and sandstones inter- 
calated, while the upper are found to contain flaggy sandstones. 
The principal sandstones, however, are in the middle member, 
which is comparatively barren of fossils, but contains much dif- 
fused hematite, giving the rock a markedly red color. These 
beds also, like those of the corresponding stage of the St. John 
terrane, frequently show ripple-marked layers replete with worm 
burrows, worm trails, and other marks of a shallow-water origin. 
The oscillations of land and sea jn this earlier part of Cam- 
brian time in the areas of Southern New Brunswick and Cape 
Breton exhibit the following succession of conditions : 
ist. — An emerged region that became loaded with volcanic deposits — lava, 
ashes and scoria. 
-2nd. — A sinking of the earth’s crust, so that later ejections were cast into 
the sea, and the wash from the still emerged surfaces added to 
the accumulating deposit. 
