Unit: P18

image PAL-04

full-size image

annotated image

Within the mudstones of Unit 18 are feldspar-phyric basalts. Note the white, euhedral, early-formed plagioclase feldspar phenocrysts. In the bottom right is a circular section through an amygdale - an infilled gas bubble.

This is a close-up of the rock seen in images PAL-03 and PAL-11. This rather coarse-grained rock is found at the centre of one of the pillows.

  • The larger white crystals are plagioclase feldspar.
  • In between them are smaller crystals of darker minerals, mainly pyroxene.
  • What is the evidence for the order of crystallization of minerals from the magma?

  • In general terms, what was the composition of the magma - acid, intermediate or basic?

Scale: Coin is 15mm across

Grid reference: 980 275

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This page is maintained by Roger Suthren

Last Modified: 18 November, 2008