My argument that at Porthalla there is a “passage” from hornblende-schist to serpentine; or rather that some beds of a common series have been changed into serpentine, others into hornblende-schist, and others again into a substance of intermediate character, is, I think, much strengthened by the fact that many such “apparent passages” are admitted to exist by all those who have examined the Lizard Coast with any degree of detail. De la Beche's description of that seen near the Lizard Town is as follows, and it would apply equally well to the others. “The hornblende slate,” he says, “supports the great mass of the Lizard serpentine with an apparent passage of the one into the other in many places—an apparent passage somewhat embarrassing,” that is, from his point of view; from mine it is perfectly natural. He goes on to say: “Whatever the cause of this apparent passage may have been, it is very readily seen at Mullion Cove, at Pradanack Point, at the coast west of Lizard Town, and at several places on the east coast between Landewednack and Kennick Cove, more especially under the Balk … and at the remarkable cavern and open cavity named the Frying-Pan, near Cadgwith.” At Kynance some of the laminse of serpentine are not more than one-tenth of an inch in thickness for considerable distances.
Combined potential field and airborne electromagnetic interpretation to unravel the geological history of the Curaca Valley Region, Bahia, Brazil
