The Burnley Coalfield, separated from the South Lancashire Coalfield, is in the form of an oval bowl extending north-east from Blackburn, past Colne to the Pennine Hills. Bounded by the Pendle monocline to the north and the Rossendale Valley anticline to the south, the coalfield is dissected by a series of predominately north-westerly trending faults, the most significant fault is the Cliviger Valley Fault at Burnley with a throw of up to in Cliviger valley. The intersecting Theiveley Lead Mine Fault is one of a smaller number of easterly aligned structures. Unlike South Lancashire, only the Lower Westphalian coal measures are available. The hills above are formed of Carboniferous sandstones, ranging from millstone grits to finer grained stone such as the Dyneley Knott flags and the Dandy Mine Rock. The drift cover consists primarily of glacial till deposits, which cause poor-drainage soils.