They do look like mud cracks, don't they?

But we don't need alot of water for them to occur. Some of the best mudcracks I've seen have been in the desert a day after a small rain. Playa lakes and sabkhas are perfect enviroments for mud cracks. The thing 'bout these cracks - they appear to be deep, deeper than mudcracks I've seen. If they are mud cracks, they should also narrow to a point as they get deeper. I've not noticed that in the cross-section views I've seen of these features. I'll keep my eyes open. Oh, sometimes I think those linear voids might be contraction jointing features, similar to "tension gashes", but most of the time I think I'm nuts. Especially when I walk by the mineral cabinet and see the shapes of some gypsum crystals I collected in Utah.

More on the layers:

Just about all sedimentary processes involve the sorting of grains according to size and weight. Fill a jar half full of sand of different sizes, top it off with water, put on the lid, give it a good shaking, set it down, and watch the grains sort themselves out. The big and heavy grains will be the bottom layer. When preserved in a sedimentary deposit it is called a "graded bed". Some times you see a sedimentary rock that has layer after layer of graded beds, each representing a pulse of sediments. This grading also help one determine if a rock has been turned upside-down or not. (actually a big deal in this line o' work) The sedimentary pulse may be a flood, an underwater debis flow (turbidite), the annual turn-over of a lake... So they could be varves (annual deposits, as Nick suggests), or seasonal events, or regular short term events. Like wind storms.

Wind is very effective at sorting sediements. In a modern sand dune one can observe sets of sediemenary layers at this scale. Sometimes the size difference is small within the graded bed, but just a small differece can show it's effects under differential weathering. This is what I think is causing the layers. (And I'm gonna call 'em "beds" from now on. )

I don't think there was all that much "flooding", per se. Sure, a desert playa on earth has periods of a small amount of flooding then dries out. But I think this is more "wetting" where the water table rises, or water is constantly wicking to the surface through evaporation. BTW, a water table is great for preserving the lower sequence of a dune field; wet sand doesn't blow away.

Oh, nothing personal, but the word "slip" has a quite specific meaning in structuaral geology. It is a term describing movement of faults where you can discern a vector of movement. It is also used to describe the sliding of layers in a series of rocks as they are folded, like what happens between the pages when you bend a phonebook. Replace "slip plane" with "contact". (Sorry, I've done enough teaching to get rather pedantic at times, and my graduate thesis advisor would charge a six-pack of beer for confusing slip with separation! )

Enjoy your day...