Item 7.1 Att 4 (5) Ex A - Final_EACCS_Oct2010_Print - City of Dublin

Chapter 2 Environmental Setting
of the Miocene Briones Formation. East of the Calaveras fault, surface
exposures consist of surficial alluvial and landslide deposits of Holocene age
(Graymer et al. 1996).
The southern and eastern portion of the plan area encompasses the northern
Diablo Range, which is the easternmost principal uplift of the central Coast
Ranges province. The structure of the Diablo Range is broadly antiformal, with a
core of Franciscan rocks such as Eylar Mountain terrain (sandstone, siltstone,
conglomerate and chert), Melange terrane, and Undivided Franciscan
greenstone (Graymer at al. 1996), flanked by younger sedimentary strata (Norris
and Webb 1990). The Altamont Hills, in the northeastern-most corner of the
plan area, are characterized by the sands, pebbles, and white sandstone of the
Miocene-Age Neroly Formation and Cierbo Formation, as well as interbedded
deep marine sandstone and shale of Late Cretaceous age. South and west of
the Altamont Hills, the structure of the Diablo Range is largely influenced by the
presence of the northwest-striking Ortigalita fault, just east of the range’s crest.
The area directly on the fault juxtaposes conglomerate and sandstone of the
Panoche Formation (Great Valley Group) against Franciscan bedrock (Wagner et
al. 1991; Graymer et al. 1996). The Panoche Formation is overlain by an eastdipping
sequence of clastic sedimentary strata ranging in age from Eocene
through Quaternary of marine and shell marine origin (Sullivan and Waters
1980).
The Livermore Valley, containing the cities of Livermore and Pleasanton, lies
south and west of the Diablo Range and east of the East Bay Hills. This valley, an
east-west trending valley, unique to this area, is a deep alluviated depression
(Ollenburger 1986) containing sediments deposited as part of the Livermore
Gravels Formation. The Greenville fault forms the eastern border of this valley,
separating it from the western foothills of the Diablo Range. It is postulated
that the Greenville Fault is connected to the Concord Fault at depth by a buried
“blind” thrust fault system (Wetlands Research Associates 2004). It is this
interaction of the Greenville and Concord Faults that has created the Mount
Diablo uplift, a presently active (Crane 1995), Late Quaternary tectonic feature
located in the north-central portion of the study area. The bedrock structure of
the Mount Diablo uplift is composed of rocks of the Miocene Green Valley/
Tassajara Formation and is postulated to contain deposits of the Livermore
Gravels Formation (Graymer et al. 1996). The core of the Mount Diablo uplift,
located just north of the plan area, contains older Franciscan rocks, flanked by
east- and westward-younging sedimentary strata of Eocene through Pliocene
age.
2.3.3.3 Soils
Because of the geologic, microclimatic, and topographic diversity of the study
area, the soils are also very diverse, and a large number of individual soil units
have been mapped. These have been organized into four soil associations
East Alameda County Conservation Strategy 2-17 October 2010
ICF 00906.08