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Southern California Areal Mapping Project


Geologic Framework of the Santa Barbara Coastal Plain

| Selected references (coming soon) |
The geology of the Santa Barbara coastal plain is dominated by variably deformed Cretaceous through late Cenozoic marine and nonmarine sedimentary strata. These strata record a long history of continental-margin sedimentation, and deposits as young as Quaternary have sustained strong deformations that include folding, thrust and reverse faulting, and rotations of crustal blocks about steep axes. Quaternary deformation in this area has produced a series of uplifted and folded coastal terraces and alluvial fans that form a substrate for the rapidly growing Santa Barbara-Goleta urban corridor. regional index map

Click to enlarge regional index map.

Potential seismic sources of the onshore Santa Barbara fold and fault belt


Figure 2. Potential seismic sources of the onshore Santa Barbara fold and fault belt (SBFFB) showing south-dipping reverse faults, some of which are blind, with associated north-verging hanging-wall anticlines and footwall synclines. The Mission Ridge fault system is subdivided into the More Ranch (MrR), Mission Ridge (MsR), and Arroyo Parida segments. Additional onshore reverse faults include the Dos Pueblos (DP), Carneros (CF), San Jose (SJ), San Pedro (SP), Lavigia (LF), Mesa (MF), Santa Barbara Cemetery (SBC), Ortega Hill (OH), and Loon Point (LP) faults. Figure modified from Keller and Gurrola (2000) 5.7 MB PDF.
The Santa Barbara coastal plain is transected by numerous active and potentially active folds and partly blind reverse faults of the Santa Barbara fold and fault belt (SBFFB) (Fig. 2). Strong earthquakes that occurred in the region in 1925 (M 6.8) and 1978 (M 5.1) are evidence that such structures pose a significant earthquake hazard to the 200,000 people living on the coastal plain. Recognizing this, FEMA designated the Santa Barbara area as a Project Impact Site warranting future focused hazards research. Young landslide deposits along the steep lower flank of the Santa Ynez Mountains indicate that slope failures and mass movements have, and may continue to, threaten urbanized parts of the coastal plain. In addition, the coastal plain is subjected to limited groundwater resources and poor water quality due to salt-water contamination. To address these societal issues and to synthesize Quaternary geologic history, SCAMP is mapping and analyzing geologic structures and deposits in the coastal plain region.

Geologic mapping investigations

Ongoing surficial and bedrock geologic mapping at a scale of 1:24,000 on the Santa Barbara coastal plain will provide a uniform geologic digital database of the region that will include detailed documentation of potentially active folds and faults. This database will highlight potentially seismogenic neotectonic deformation as well as recent landslides in urban and suburban environments. The new data, and the derivative subsurface interpretations, may be used to constrain three-dimensional hydrogeologic framework models of the Santa Barbara coastal plain area.
Initially a geologic strip map of the coastal plain and fold belt within the Santa Barbara and Goleta 7.5' quadrangles is being compiled at a scale of 1:24,000 (fig. 3). Later mapping will extend westward into the Dos Pueblos quadrangle and eastward into the Carpinteria quadrangle.



Figure 3. Satellite image of Santa Barbara coastal plain region showing extent of current and planned mapping relative to the SBFFB (northern margin shown in red).

Supporting investigations

Several topical investigations are being conducted in support of the geologic mapping:
  • Analysis of slip history of potentially active faults and associated folds.
  • Studies of Cenozoic fossils to refine ages of selected sedimentary units and to facilitate regional stratigraphic correlation.
  • Dating of landform surfaces on geologically young deposits to constrain timing of recent deformation and landsliding.
  • Tectonic geomorphic studies of deformed landforms on the Santa Barbara coastal plain.

Cooperative Interactions

  • California Division of Mines and Geology (landslide/seismic hazard studies)
  • University of California at Santa Barbara (tectonic geomorphology, marine-terrace chronology, surficial geologic mapping, ground water). See Keller and Gurrola (2000) 5.7 MB PDF.
  • Thomas W. Dibblee, Jr., Geological Foundation (regional geology)
  • University of California at Riverside (optical stimulation luminescence dating)


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This site last updated September 3, 2004 (ps)

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