Which AVA is described as having rocky-stony loam and heavy clay-silt in its valley center?

The correct choice refers to Calistoga, which is characterized by its unique soil composition that includes rocky-stony loam and heavy clay-silt found in the valley center. This particular soil type plays a crucial role in viticulture as it influences drainage, nutrient availability, and ultimately the flavor profile of the grapes grown in the area.

Calistoga is known for its warm climate, which, combined with these soil conditions, facilitates the growing of robust varietals, particularly Zinfandel and Cabernet Sauvignon. The presence of heavy clay provides moisture retention, while the rocky-stony aspects improve drainage, creating an ideal balance for vine health.

Understanding these soil characteristics helps illustrate why Calistoga has gained a reputation for producing high-quality wines, distinct to its geological and climatic conditions.