Smooth basalt and bubbly tuff?

Once again I was talking with Mike Widdowson who was explaining to me the new set of cores now being extracted at our new site and hole. I thought it was interesting because of the wide range of coloration from smooth grey to bubbly and chunky red.

Apparently it’s the basalt Will was looking for and volcanic tuff on top. If you look closely at the picture I’ve provided here, the top of the layers is a brownish and reddish base with what used to be bubbles that have filled with fluid (ocean water with all the mineral salts along with it), the volcanic tuff on top that I thought looked pretty cool. Below is the smooth grey rock which is a lava flow. If you look closely at the lower left of the picture, most tray there is an area of black, which indicates new lava flow where everything in that layer has burnt (I’m starting to get a hang of this!).

Now what the explanation is for this formation is very fascinating. As the lava flows out of the volcano head the gases bubble up and leave the grey area leaving it smooth (no vesicules), and makes it way to the top.  The bubbles fill with fluid that then solidify and also cause geochemical reactions that alter the chemical nature of the rock, and the origin can then be determined by geochemical analyses; this kind of rock can be very hard and difficult to drill through. The reddish coloration is due to oxidation processes, also a chemical alteration reaction to the rock that can only happen in a well-oxygenated environment. Using these clues, can you solve the puzzle?