Looks like rock too me. I don’t think that would be trunk tissue, since fossilized tissue almost never fossilizes, esspecially in a coarse rock like that. The impressions look like they are probably from erosion or fracturing, and this rock looks either igneous or metamorphic. Some fossils including the hollow mold of the body of a pliocene rhinoceros which drowned in lava, have been found, but those are incredibly, incredibly rare.