View source for Basal conglomerate

A well-sorted, lithologically homogeneous conglomerate that forms the bottom stratigraphic unit of a sedimentary series and that rests on a surface of erosion, thereby marking an unconformity; esp. a coarse-grained beach deposit of an encroaching or transgressive sea. It commonly occurs as a relatively thin, widespread or patchy sheet, interbedded with quartz sandstone.  <i>AGI </i>

Source: Dictionary of Mining, Mineral, and Related Terms