The Paso Robles Divide

[Rebel Rose]

Lines are being drawn and tempers are heating up as the TTB considers two separate petitions for new AVA's in the large Paso Robles region.

Full article at Appellation America.

For anyone interested, here is an excerpt from an interview with soils scientist Dr. Tom Rice about the soils of Paso Robles:

MB: What are the basic differences and similarities between the terrains of East Paso versus West Paso?

TR: Soils planted to vineyards west of the Salinas River are mainly derived from the Monterey Formation, which is composed of shale, mudstone, siltstone and limestone. They are both calcareous (carbonate-rich) and siliceous (silica-rich).

Soils planted to vineyards east of the Salinas River are derived from a wider variety of parent materials. The river bench areas are mainly alluvial sediments from the Paso Robles Formation and have varying depths of clay, gravel and sand. Compacted subsoil horizons often restrict downward water flow and limit vine root growth. However, there are also many upland hillside soil areas on the east side which are derived from the Monterey Formation and resemble the soils on the west side of the river.

There’s more homogeneity on the west side; soils on the east side are more diverse with no single dominant soil type.

MB: What is your response to the charge that there is no limestone in West Paso Robles?

TR: Limestone does exist throughout Paso Robles, but not in huge formations like boulders or cliffs, as in parts of France. On the east side, it’s usually found at depths of five feet or more, buried by the Paso Robles Formation sediments. These strongly effervescent lime layers exist closer to the water table and may take the form of a stickier subsoil. Western Paso Robles rocks are a combination of calcareous and porcelainous (silica-containing) mudstone and calcareous shale, but there’s also dolomite and other carbonate rocks. Limestone layers in west Paso Robles exist as thin one or two-foot thick ribbons, laced throughout the other calcareous soils. Because of the more rugged topography, you can often find layers of limestone on eroded ridgetops, and the boulders you see dug up for walls are often large chunks of limestone and calcareous sandstone. They are sometimes displaced and sandwiched between porcelainous sedimentary rock beds. Parts of Paso Robles have been so folded they look like overturned omelets.