ra

must extend to considerable depths and they are considered on
this account to be the master joints of the region. Into these
deep fissures the magma was forced under enormous pressure,
filling them with great rapidity. The fact of the occurrence of

Figure 8. Irregular andesite dyke cutting shaly sandstones on beach west
of Haida point, illustrating also the baking of the sediments.

such thin bodies of igneous rock so far from their source proves
two things: a large amount of superheat in the magma, and a
very rapid intrusion.

Age. The Etheline sills and dykes cut the Upper Cretaceous
beds of the Queen Charlotte series, and are, therefore, younger