I used to get to see Mark quite a bit in the early 80s in Boston. It would seem that he would have been a serious Jaco clone, given that he studied with Jaco and then took over his gig, but he's got his own voice. What's weird is that Jeff, a great bassist as well, doesn't even have to play fretless to invoke the voice of Jaco. He is a pugnacious SOB, but that's part of his charm.
Edwin
Who is on Jeff's killfile for protecting free speech.