Complex sentence: The West Kentucky Coal Field comprises an area in the west-central and northwestern part of the state, bounded by the Dripping Springs Escarpment and the Pennyroyal Plateau and the Ohio River, but is part of the Illinois Basin that extends into Indiana and Illinois.
Split into simpler sentences: The West Kentucky Coal Field comprises an area in the west-central part of the state, bounded by the Dripping Springs Escarpment. This area is bordered on three sides by the Pennyroyal Plateau and to the north by the Ohio River, but is part of the Illinois Basin that extends into Indiana and Illinois.