Sinus Aestum
This image shows one example of a large dark mantling deposit. It is
located in Sinus Aestum on the central nearside, and is just east of the
crater Copernicus. (Part of Copernicus lies on the leftmost edge of the
photo.) Note how the dark areas in this photo (arrows) resemble the
brighter highlands nearby. This suggests that the dark unit is relatively
thin, and that it was dropped uniformly across an older, non-volcanic
surface.
(Earth-based telescopic photo from the Consolidated Lunar Atlas).