One of the most distinguishing features of the Los Olivos District relative to other California AVAs, is the uniformity of its geology and soils. The District can be described as a fairly broad alluvial bench composed of a gently to moderately sloping terrain with the vast majority of the area underlain by terrace deposits including Orcutt sand, as shown in the Geologic map of the Santa Ynez River Basin.
As one can see in the map, the geologic uniformity of the Los Olivos District (LOD) contrasts with the variegated geology of both the Happy Canyon (HC) area ( partially mapped out ) and the Ballard Canyon (BC) area. The Sta Rita Hills area ( not shown ) also has a highly variegated geology.
There are 14 principal soil associations found in Northern Santa Barbara County, and about half of them are found in the Santa Ynez Valley AVA. The Los Olivos District is quite uniform in its soil profile, with over 95% of the area consisting of the Positas-Ballard-Santa Ynez soil association, and directly linked to the underlying geology.
The Positas series consists of well-drained fine sandy loams that have a clay subsoil. These soils are in the upper Santa Ynez Valley on smooth, bench-like terraces that are broken by narrow, steep-sided drainage-ways, with elevations ranging from 400 to 900 feet. The Ballard series consists of well-drained fine sandy loams and gravelly fine sandy loams that formed in alluvium derived from acid shale and sandstone. These soils are located on remnants of old terraces that have been somewhat dissected by drainage-ways, with elevations ranging from 500 to 1000 feet. The Santa Ynez series consists of moderately well-drained gravelly fine sandy loams underlain by gravelly clay sub-soils that developed on terraces with elevations ranging from 600 to 800 feet.
The Soil Map ( on the right ) shows this homogeneity of the soil profile of the Los Olivos District in contrast to the soil profiles of the other areas of the Santa Ynez Valley. The Ballard Canyon area is also relatively uniform ( but with a different soil association ), while both the Happy Canyon and Sta Rita Hills areas are diverse and composed of several soil associations each.
The soils found in the los Olivos District are characterized as being relatively well drained without being excessively well drained, and with low to moderate fertility, which is favorable to quality viticulture.
In addition to uniform geology and soil profile, the Los Olivos District enjoys a relatively uniform topography in the form of an expansive south-facing alluvial terrace plain ( see Figure below ), and the only broad alluvial plain along the entire Santa Ynez River Valley. Elevations range from 1000 feet along the base of the foothills of the San Rafael Mountains to approximately 400 feet along the Santa Ynez River. This range in elevations corresponds with the elevations in which the Positas-Ballard-Santa Ynez soil association is found.
In summary, the Los Olivos District viticultural area is a unique geographical and geological feature characterized as that section of the Santa Ynez Valley River which describes a broad valley between the Purisima Hills above Solvang and the western flank of the Happy Canyon area. The uniformity of geology, soil profile, topography, and climate is unparalleled when comparing it other AVAs in California.