The main rock formations in the Lackawanna River watershed contain sandstone and shale, with rich coal deposits. For instance, the Llewellyn Formation contains anthracite in the watershed, along with sandstone and shale. Under this rock formation lie the Pottsville Formation, the Pocono Formation, the Mauch Chunk Formation, and the Catskill Formation. The first of these is made of coal, shale, sandstone, and conglomerate, while the second contains red sandstones and shales. The Pocono Formation contains dense sandstones and conglomerates and occurs in outcrops on the Moosic and West Mountains. The Catskill Formation mainly occurs on the fringes of the watershed. A total of 67 percent of the rock in the watershed is interbedded sedimentary rock, while the remaining 33 percent is sandstone.