Similarity between martian sedimentary deposits and terrestrial microbial mats

Definitely interesting and a neat paper, but please keep in mind that this is _very_ speculative. (However, the authors do a nice job of stating that, and give plenty of specific tests that could be performed by Curosity or a similar rover.)

They're keying in on the top surface, but there's no strong evidence that it's a "clean" bedding plane. You get very similar structures from normal weathering. The authors make a few reasonable arguments to support the idea that there's no significant weathering, but I'm not convinced.

Ignoring geochemical signatures for the moment, a great visual test would be to take a closer look at the morphology of the laminae they mention. Stromatolitic laminations are fairly distinctive.

Caveat: I'm a geologist, but not in astrobiology.