These two flagship appellations of the Centre-Loire share Sauvignon Blanc as their sole grape variety, but their terroirs give them very distinct characters. Sancerre is distinguished by its three soil types — fossiliferous limestone (caillottes), clay-limestone (terres blanches), and flint — which bring tension, minerality, and fresh fruitiness. Pouilly-Fumé, produced on the opposite bank of the Loire, is more markedly influenced by flint and Kimmeridgian limestone soils, offering that characteristic smoky character and a generally rounder texture.