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Brecciation problem

Thought I'd throw this out to the list...
We were discussing collapse breccias yesterday in my mineral deposits
class.  These are breccias formed when tube of material collapses from
dissolution of material below.  The fragments come to rest,
unconformably, on the surface below. Basically there is a flat surface
overlain by a pile of fragmented rocks.  Then I thought of my
Millbillillie specimen with the breccia on one half and the "basalt" on
the other, two different textures. Most meteoriticists claim this formed
from an impact.  I may disagree, as they may be collapse features from
the surface of an asteroid-not impact features related to evacuation of
a chamber below. Plus there are no impact induced shock veins in
Millbillillie. Does anyone have any other thoughts on this? I am
curious.

Best,
Matt Morgan
http://www.mhmeteorites.com