I'm getting a lot of dog barf fungus this year. After it goes through the barfy look phase, it turns dark brown like what you have. Here's a pic from the barf look before turning dark brown.

Also it become very hydrophobic once it turns brown. If you try to wash it down, it just blows away. For size reference, those are 4-ft long carpet tack strips in the picture.

Dog barf fungus seems to be harmless to the garden, but I stay away from it on a windy day.

Are we talking about that brown patch in the photo as the "weird fine powder"? It doesn't look like any mold to me (nor is there any actual lawn to be seen in your photo ;-)) It looks more like some soil that has been pushed up between the weeds, perhaps by some burrowing creature. Or even a scrunched or stepped on worm casting. Is there more than just that one?

I believe we are talking about the brown patch. My theory is that it is the dog vomit fungus, which, according to this page, is really a mold. The brown stage is the spore stage. Here is the wiki page. I'll see if I can get a picture of the spore stage tomorrow. The spore stage is highly unimpressive compared to the puffy yellow vomit stage.

It's been raining all night. Everything looks the same color of brown. If it dries up I'll get a picture.

Thanks for the replies. I should mention I live in South Carolina and didn’t get much or really any snow this winter. It’s also in an area of very infrequent foot traffic. It’s weird to me because when I poked it with a stick(yeah, I couldn’t help myself) a ploom came out as if it were smoldering ash.

That plume was a huge burst of spores. But it would have been released anyway when the fungus dried out, so no matter.

The very vast majority of fungi are opportunistic and don't go anywhere, like a sudden spate of mushrooms in the gardens. They appear, they do their mushroomy thing, they go away until the next extended rainy period. Most of the "dog vomit fungi" (I love that) are in that category, so unless you see it spread, don't worry too terribly much.

Warming weather should take care of it.

It finally stopped raining. Here's my dog barf fungus in the late stage.