High-resolution altimetry and imaging have revealed the presence of a meters-thick sedimentary layer at middle to high northern and southern latitudes presently covering at least 23% of the planet. The layer is interpreted to be water-ice-rich, and to undergone degradation recently. Its activity very likely coincided with the last major obliquity excursion a few hundred thousand years ago. The majority of the layer at higher latitudes, however, persisted for a much longer time in the Late Amazonian. Stratigraphic analysis suggests a complex history of successive episodes of deposition and removal. Repeated deposition and removal of the mantles are interpreted to be responsible for the unusual statistical properties of kilometer-scale topography in the transitional mid-latitude zones.