1. "Inversion and Reverse Faulting, Santa Maria Basin: Offset Quaternary Fluvial Terraces at Santa Cruz Creek,
Faulting Rates Calculated Using Remote Sensing Methods and Optically Stimulated Luminescence Dating"
“Todd” Edward Tyler1, Dr. Nathan Onderdonk 2
California State University, Long Beach
Figure 1: Digital Elevation Model of SMB showing large-scale folds
and major faults which accommodate shortening of the basin, and
location of Figure 2 (box).
Figure 4: View east across SCC to
Terrace 2 (middle foreground) and
Terrace 3 (middle background).
Introduction Methods
1 todd.tyler@conservation.ca.gov, 2 Nate.Onderdonk@csulb.edu
Dibblee, T.W., 1987. Geologic Map of the San Markos Pass Quadrangle - Santa Barbara County, California.
Dibblee, T.W., 1993. Geologic Map of the Figueroa Mountain quadrangle – Santa Barbara County, California.
Dibblee, T.W., 1995. Geologic Map of the San Rafael Mountain quadrangle – Santa Barbara County, California.
Dibblee, T.W., and Ehrenspeck, H.E., ed., 1987. Geologic Map of the Lake Cachuma quadrangle, Santa Barbara, County, California.
Guptile, P.D., 1991. Los Alamos-Baseline fault trend, Santa Barbara County, California [Dissertation University of California, Santa Barbara, (unpublished)]
Tyler, E.P., 2013. Tectonic Geomorphology of Quaternary River Terraces at Santa Cruz Creek, Santa Barbara County, California [Thesis, California State University Long Beach].
References
Landslide
Teeth on Over-Thrust Side
Arrow Toward Plunge
Arrow Toward Plunge
The Santa Maria Basin (SMB) of Santa Barbara
County (SB) California (Figs.1 + 2) is being
inverted. Active north-south shortening here is
accommodated by reverse and thrust faults, and
multiple sets of east-west trending synclines and
anticlines (Fig. 1). SMB is a known petroleum
producing area with proven reservoirs.
Understanding deformational structures and
style leads to a better understanding of basin
evolution, reservoir characteristics, and seismic
hazard risk. Mapping in the Santa Cruz Creek
(SCC) area of the SMB (Fig. 3) reveals stacked
flights of strath type terraces suggestive of rapid
uplift, and evidences of poorly exposed faulting.
Identifying faults can be accomplished by
demonstrating deformation of terrace surfaces
through geomorphic analysis. Offset terrace
surfaces were dated using Optically Stimulated
Luminescence (OSL) to calculate the slip rate of
the Baseline/Los Alamos (BLA) fault zone.
Deformation of Quaternary terraces at the Little
Pine (LP) fault and BLA are also apparent.
Figure 2: Location map of the eastern SMB and Santa Cruz Creek, the
San Rafael Mountains, Cachuma Lake, and Santa Ynez Valley, CA.
Terraces and faults were identified by 1. Field and
ArcGIS mapping. 2. GPS surveys of terrace surfaces
and SCC channel gradient. 3. Published data were
digitized in GIS. 4. Test Pits were sampled and logged
5. Samples from test pits were analyzed in lab using
OSL to determine age of formation. 6. Incision/uplift
rates and fault deformation were determined by
geomorphic analysis of GPS survey data in Excel.
Figure 5: West view across SCC to
Terrace 1 future OSL Pit (front right)
and Terrace 2 surface (upper left).
Figure 3: Simplified Geologic map of SCC field area on the northeast side of
Cachuma Lake. Folds digitized from Dibblee, 1987, 1993, 1995, 2005). Active
faults from USGS active faults meta data, terraces and GPS points mapped in field.
Figure 6: OSL test pit in Terrace 1
shown in Figure 5 and location.
Figure 7: Composite Excel plot of GPS Terrace
surface and SCC active stream gradient profiles,
and correlated faults/syncline axis.
Figure 7 (inset): Close view of right end
(southeast) portion of profile and
diagrammatic map of area. An alternate
interpretation of BLA based on Guptile,
1993 and surface profile anomalies.
Geomorphic methods document deformation of three flights of Quaternary fluvial terraces crossing the poorly
exposed, tectonically active Baseline/Los Alamos fault zone and Little Pine fault on the northern margin of the
Santa Maria Basin at Santa Cruz Creek, CA (Figures 1 and 2). Field and GIS mapping, soils chronology, and GPS
differential elevation surveys of the terrace surfaces (Figures 3-6) were used to document deformation
(warping and tilting) and measure offsets to terrace surfaces across the faults (Figures 7 and 8). Optically
Stimulated Luminescence (OSL) was used to date terraces in order to obtain incision rates (analogous to area
uplift rates) and slip rates of offset features (Tables I-III).
Terrace 1 is dated at 19.3 ka with a revised incision rate of 1.82 to 1.89 mm/yr, Terrace 2 was dated at 32.9 ka
with a revised incision rate of 2.13 to 2.22 mm/yr (Table I). Based on these incision rates, and assuming the
long term incision rate from Terrace 2, an age of 47.1 to 47.3 ka is approximated for Terrace 3 (Table II). Offsets
to projections of the Terrace 2 and 3 surfaces at their mapped correlations to the Baseline/Los Alamos fault
(Figures 7 and 8) were used to calculate slip rates for that structure. A short term faulting rate for the
Baseline/Los Alamos fault of .91 mm/yr has occurred since the formation of Terrace 2, and a long term slip rate
of 0.68 mm/yr has occurred since the approximated formation age of Terrace 3 (Table III).
Evidence for Quaternary deformation at the Baseline/Los Alamos fault is demonstrated in Figure 7. The south
(right) end of Terrace 1 surface profile located on the up thrown/south side of the BLA fault appears over
steepening in the down stream direction when compared to the local SCC channel in the area. The Terrace 3
surface appears to have an upward warping at the mapped location of the fault and upward bulging/increased
irregularity to the surface at mapped location of the Baseline/Los Alamos syncline axis, Figure 7.
At the Little Pine fault shown in the north (left) portion of (Figure 7) deformation of all three terraces
correlates to the mapped fault location. The portion of the Terrace 1 surface situated on the up thrown side of
the fault demonstrates back tilting in the upstream direction when compared to the local SCC channel gradient
and the adjacent portion of terrace on the footwall block/downstream side of the fault (Figure 7). The
analogous older/higher fragments of Terraces 2 and 3 in the same portion of the profile suggest progressively
increasing back tilting in the upstream direction over time (Figure 7).
Discussion
Table I: Calculation of the
incision based on OSL ages
Table II: Estimated Terrace 3 age Table III: Calculated and
Estimated Faulting Rates
!["Inversion and Reverse Faulting, Santa Maria Basin: Offset Quaternary Fluvial Terraces at Santa Cruz Creek,
Faulting Rates Calculated Using Remote Sensing Methods and Optically Stimulated Luminescence Dating"
“Todd” Edward Tyler1, Dr. Nathan Onderdonk 2
California State University, Long Beach
Figure 1: Digital Elevation Model of SMB showing large-scale folds
and major faults which accommodate shortening of the basin, and
location of Figure 2 (box).
Figure 4: View east across SCC to
Terrace 2 (middle foreground) and
Terrace 3 (middle background).
Introduction Methods
1 todd.tyler@conservation.ca.gov, 2 Nate.Onderdonk@csulb.edu
Dibblee, T.W., 1987. Geologic Map of the San Markos Pass Quadrangle - Santa Barbara County, California.
Dibblee, T.W., 1993. Geologic Map of the Figueroa Mountain quadrangle – Santa Barbara County, California.
Dibblee, T.W., 1995. Geologic Map of the San Rafael Mountain quadrangle – Santa Barbara County, California.
Dibblee, T.W., and Ehrenspeck, H.E., ed., 1987. Geologic Map of the Lake Cachuma quadrangle, Santa Barbara, County, California.
Guptile, P.D., 1991. Los Alamos-Baseline fault trend, Santa Barbara County, California [Dissertation University of California, Santa Barbara, (unpublished)]
Tyler, E.P., 2013. Tectonic Geomorphology of Quaternary River Terraces at Santa Cruz Creek, Santa Barbara County, California [Thesis, California State University Long Beach].
References
Landslide
Teeth on Over-Thrust Side
Arrow Toward Plunge
Arrow Toward Plunge
The Santa Maria Basin (SMB) of Santa Barbara
County (SB) California (Figs.1 + 2) is being
inverted. Active north-south shortening here is
accommodated by reverse and thrust faults, and
multiple sets of east-west trending synclines and
anticlines (Fig. 1). SMB is a known petroleum
producing area with proven reservoirs.
Understanding deformational structures and
style leads to a better understanding of basin
evolution, reservoir characteristics, and seismic
hazard risk. Mapping in the Santa Cruz Creek
(SCC) area of the SMB (Fig. 3) reveals stacked
flights of strath type terraces suggestive of rapid
uplift, and evidences of poorly exposed faulting.
Identifying faults can be accomplished by
demonstrating deformation of terrace surfaces
through geomorphic analysis. Offset terrace
surfaces were dated using Optically Stimulated
Luminescence (OSL) to calculate the slip rate of
the Baseline/Los Alamos (BLA) fault zone.
Deformation of Quaternary terraces at the Little
Pine (LP) fault and BLA are also apparent.
Figure 2: Location map of the eastern SMB and Santa Cruz Creek, the
San Rafael Mountains, Cachuma Lake, and Santa Ynez Valley, CA.
Terraces and faults were identified by 1. Field and
ArcGIS mapping. 2. GPS surveys of terrace surfaces
and SCC channel gradient. 3. Published data were
digitized in GIS. 4. Test Pits were sampled and logged
5. Samples from test pits were analyzed in lab using
OSL to determine age of formation. 6. Incision/uplift
rates and fault deformation were determined by
geomorphic analysis of GPS survey data in Excel.
Figure 5: West view across SCC to
Terrace 1 future OSL Pit (front right)
and Terrace 2 surface (upper left).
Figure 3: Simplified Geologic map of SCC field area on the northeast side of
Cachuma Lake. Folds digitized from Dibblee, 1987, 1993, 1995, 2005). Active
faults from USGS active faults meta data, terraces and GPS points mapped in field.
Figure 6: OSL test pit in Terrace 1
shown in Figure 5 and location.
Figure 7: Composite Excel plot of GPS Terrace
surface and SCC active stream gradient profiles,
and correlated faults/syncline axis.
Figure 7 (inset): Close view of right end
(southeast) portion of profile and
diagrammatic map of area. An alternate
interpretation of BLA based on Guptile,
1993 and surface profile anomalies.
Geomorphic methods document deformation of three flights of Quaternary fluvial terraces crossing the poorly
exposed, tectonically active Baseline/Los Alamos fault zone and Little Pine fault on the northern margin of the
Santa Maria Basin at Santa Cruz Creek, CA (Figures 1 and 2). Field and GIS mapping, soils chronology, and GPS
differential elevation surveys of the terrace surfaces (Figures 3-6) were used to document deformation
(warping and tilting) and measure offsets to terrace surfaces across the faults (Figures 7 and 8). Optically
Stimulated Luminescence (OSL) was used to date terraces in order to obtain incision rates (analogous to area
uplift rates) and slip rates of offset features (Tables I-III).
Terrace 1 is dated at 19.3 ka with a revised incision rate of 1.82 to 1.89 mm/yr, Terrace 2 was dated at 32.9 ka
with a revised incision rate of 2.13 to 2.22 mm/yr (Table I). Based on these incision rates, and assuming the
long term incision rate from Terrace 2, an age of 47.1 to 47.3 ka is approximated for Terrace 3 (Table II). Offsets
to projections of the Terrace 2 and 3 surfaces at their mapped correlations to the Baseline/Los Alamos fault
(Figures 7 and 8) were used to calculate slip rates for that structure. A short term faulting rate for the
Baseline/Los Alamos fault of .91 mm/yr has occurred since the formation of Terrace 2, and a long term slip rate
of 0.68 mm/yr has occurred since the approximated formation age of Terrace 3 (Table III).
Evidence for Quaternary deformation at the Baseline/Los Alamos fault is demonstrated in Figure 7. The south
(right) end of Terrace 1 surface profile located on the up thrown/south side of the BLA fault appears over
steepening in the down stream direction when compared to the local SCC channel in the area. The Terrace 3
surface appears to have an upward warping at the mapped location of the fault and upward bulging/increased
irregularity to the surface at mapped location of the Baseline/Los Alamos syncline axis, Figure 7.
At the Little Pine fault shown in the north (left) portion of (Figure 7) deformation of all three terraces
correlates to the mapped fault location. The portion of the Terrace 1 surface situated on the up thrown side of
the fault demonstrates back tilting in the upstream direction when compared to the local SCC channel gradient
and the adjacent portion of terrace on the footwall block/downstream side of the fault (Figure 7). The
analogous older/higher fragments of Terraces 2 and 3 in the same portion of the profile suggest progressively
increasing back tilting in the upstream direction over time (Figure 7).
Discussion
Table I: Calculation of the
incision based on OSL ages
Table II: Estimated Terrace 3 age Table III: Calculated and
Estimated Faulting Rates](https://image.slidesharecdn.com/38cc1409-21f6-419f-a1c3-5461ea3e921c-150629184512-lva1-app6892/85/SCCFinal-1-320.jpg)
