when a pre-existing anticline (or antiform) is intruded. Tends to be linear, following the fold.

laccolith
when an intrusion causes the anticline. More of a dome, really.

Just some vocabulary, and two of my favorite geologic terms. :-)

These rocks, at least some of them, weather and look like "Wishstone" It is capped by "Peace" looking material, which turns out is a mix of mafic mineral clasts and Mg sulfates. (what's interesting, is that Squires says the clasts include olivine - and other minerals unstable in water-, yet the cement is sulfate. Is there a problem with that? That the cementing fluid was not effective at weathering all the olivine? What does that say about the pervasive nature , or longevity, of the cementing fluid?)

About Peace Rock:

Observations by Spirit show the rock contains significant amounts of the minerals olivine, pyroxene and magnetite, all of which are common in some types of volcanic rock. The rock's texture appears to be sand-size grains coated with a material loosely binding the rock together. Spirit's rock abrasion tool dug about 1 centimeter deep (0.4 inch) in two hours.

"It looks as if you took volcanic rocks that were ground into little grains, and then formed a layered rock with them cemented together by a substantial quantity of magnesium-sulfate salt," Squyres said. "Where did the salt come from? We have two working hypotheses we want to check by examining more rocks. It could come from liquid water with magnesium sulfate salt dissolved in it, percolating through the rock, then evaporating and leaving the salt behind. Or it could come from weathering by dilute sulfuric acid reacting with magnesium-rich minerals that were already in the rock. Either case involves water."

Sounds like cemented eolean deposits to me.

I've seen some suggestion that there is a broad anticline in the Columbia Hills but I'm waiting for a good panorama to discern if it is there or if it is an artifact of perspective.. This could be from the impact that created the crater itself, or, it is intrusion related.

I believe Wishstone is a piece of "float" of a rock unit that we may now be seeing in-situ as bedrock. The "peace" looking material is a weathering product of this unit (maybe with a basaltic component. I still lean towards a Carbonatite or Anorthosite for wishstone, or another late stage differentiate of basaltic magma.)

But what if this unit (wishstone) is a melt related to the impact that created Gusev crater?

Oh, I mapped a small breccia pipe associated with the carbonatite I've mentioned before. It was about an acre in size, and really, really brecciated. Nice chunky blocks of various rock types. Sometimes there are breccia pipes that are epithermal gold deposits (the the pipe of a hot spring at the boiling level). there are other intrusions that occur as breccia pipes (diatremes, kimberlites) but I don't see those textures here. It could be a small pipe like intrusion, but not specifically a breccia pipe. If it is a sill, then we should see it as a layer between the layers of basalt, a dike will be a tabular body that crosses the regional structure.

jms