GeoTrek IV-F

GEOTREK IV-F
EASTERN SANTA SUSANA MOUNTAINS

Saturday, April 30, 2011

Topic: Upper Tertiary and Quaternary sedimentary and structural history of the Santa Susana Mountains.

Participants: Bob Ableson, Nellie Cussworth, Gene Fritsche, Sue Fritsche, Mark Karagianus, John Klutke, Fred Nuesca, Syrus Parvizian, Vicki Pedone, Lynn Sosa, Dick Squires, and Brian Swanson. See the first photo below (the group photo) to pick out these people.

Distance and Route: Total distance was about 9.5 miles. We started with a short walk along The Old Road to study the Saugus Formation. Then we took a short 2-mile hike to study the Towsley Formation in Towsley Gorge. Finally we went on a 7-mile traverse across the Santa Susana Mountains following the East Canyon Motorway and the Corral Sunshine Motorway to O'Melveny Park in Granada Hills. See Google Earth route map below.

Profile: On the profile below the start of the hike is on the left end. Elevation gain was 1,553 feet; elevation loss was 1,657 feet.

Geology: The entire hike was on the Dibblee Oat Mountain & Canoga Park (North 1/2) quadrangle (DF-36). Formations we saw included the upper Miocene Monterey Formation, the Miocene to Pliocene Sisquoc Formation, the Pliocene Towsley Formation, and the Pliocene to Pleistocene Saugus Formation. Depositional environments, stratigraphic problems, and structural history of the area were discussed.

PHOTOS TAKEN IN THE EASTERN SANTA
SUSANA MOUNTAINS ON GEOTREK IV-F
Photos taken by Gene Fritsche and Brian Swanson.
Click on the small picture to see an enlargement.

GeoTrek IV-F participants gathered at the entrance to Towsley Gorge for a group photo. In the back row, left to right, are Mark Karagianus, John Klutke, Dick Squires, Sue Fritsche, Vicki Pedone, and Brian Swanson. In the front row, left to right, are Nellie Cussworth, Bob Ableson, Fred Nuesca, Lynn Sosa, and Syrus Parvizian. Gene took the photo.
Roadcut on The Old Road north of Calgrove Blvd. near the contact between the Pliocene Pico Formation that was deposited in shallow ocean water and the younger Plio-Pleistocene Saugus Formation that was deposited by rivers on land. During the time of deposition the shoreline was migrating back and forth so that some of the rocks in this exposure were deposited in very shallow ocean water and others were deposited above the beach on land.
Fossils found in the roadcut shown in the previous photo. The fossils are broken fragments of clams (bivalves) and snails (gastropods) that lived in very shallow water just on or below the beach.
Sandstone and conglomerate in the Plio-Pleistocene Saugus Formation. The conglomerate was likely deposited in river channels right near the beach.
After studying the Saugus Formation on The Old Road, we drove a short distance to the Ed Davis Park parking lot and hiked a short distance from there to Towsley Gorge. Here the group studies an excellent outcrop of the lower Pliocene Towsley Formation exposed in Towsley Gorge. The gorge formed because the Towsley Formation is much more resistant than the shale of the underlying Sisquoc Formation and the shale of the overlying Pico Formation.
Interbedded sandstone (brown) and shale (gray) of the lower Pliocene Towsley Formation. The resistant areas that stick up above the rest of the rock are called concretions. They are more resistant because they contain a greater concentration of cement than the rest of the rock.
Closeup of the Towsley Formation showing some thin shale beds that were eroded on the edge of a channel when the rock was deposited. Deposition was under the influence of turbidity currents in deep ocean water. As a turbidity current races down the ocean slope it erodes channels in the bottom sediment, as shown by the truncated (eroded) shale beds in this photo.
Gene climbs up the outcrop to get a closer look at the sedimentary structures that were formed during deposition of the Towsley Formation. In front of his left leg is the flame structure shown in the next photo.
In this photo, the older layers are on the left and the younger ones on the right. The structure shown is called a flame structure. The coarse-grained material in the center washed down the ocean slope in a dense turbidity current over the finer material on the left that was still unconsolidated and had a high water content. As the dense, coarse sediment deposited on the bottom it settled into the underlying sand which squirted up into the coarse sediment to form what looks like a flame.
Luckily the creek in Towsley Gorge was small enough to hop across without getting our feet wet. Hiking through the gorge and seeing excellent exposures of the Towsley Formation was a pleasant and rewarding experience.
After seeing Towsley Gorge, we drove to the East Canyon Motorway trailhead where the day's main hike started. The trail went uphill rather gently at first and was shady in some places. The Towsley Formation in this area was not as resistant and well exposed as it had been in Towsley Gorge.
We found a spot in the shade on the East Canyon Motorway for lunch. From left to right are Sue, John, Brian, Vicki, Fred, and Lynn. The sandstone behind them belongs to a nonresistant part of the Towsley Formation.
The Big Cone Fir in the center of the photo marks the trace of the hinge surface of the Oat Mountain Syncline. The photo is looking west from the East Canyon Motorway. The light colored, resistant beds in most of the photo belong to the lower Pliocene Towsley Formation. Rocks on the far edges of the photo belong to the upper Miocene Sisquoc Formation that contains deep-water, siliceous diatoms that were deposited in a basin plain environment. Where would you suggest that the contact between the two formations might be?
Monkey Flowers were common along all the trails we walked on today.
View of the western San Fernando Valley from near Mission Point. On the right in the foreground are roads of the Aliso Canyon Oil Field which is now used as a natural gas storage facility. Pore spaces in the rock that were previously filled with oil were evacuated when oil was pumped out of the Aliso Canyon Oil Field. Natural gas from various places in California is now being pumped into those pore spaces where it is stored until needed. The obvious road in the middle of the valley is Reseda Blvd. and the Santa Monica Mountains are in the background. GeoTrek IV-C began near the top of the Santa Monica Mountains near the end of Reseda Blvd.
Hiking on the Corral Sunshine Motorway near Mission Point. Rocks in this area belong to the upper Miocene Monterey Formation which is slightly older than the Sisquoc Formation. Like the Sisquoc Formation, it was deposited in a deep-water basin plain environment.
We had to follow a short detour along a narrow trail through the grasslands in order to get around the fence at the edge of the natural gas storage facility. The fence was put up after 9/11 to protect against terrorist incursions into the facility.
The group pauses on the Corral Sunshine Motorway for a view of the San Fernando Valley.
The trail between Mission Point and O'Melveny Park is very steep downhill and some of the participants started getting sore knees.
View of the northern San Fernando Valley. In the midground are the Van Norman Reservoir and the city of San Fernando; in the background are the San Gabriel Mountains.
View of the Sunshine Landfill in the eastern Santa Susana Mountains. This is where nonrecyclable trash from the San Fernando Valley is being deposited. In the background are the eastern Santa Monica Mountains.
On the home stretch toward O'Melveny Park. As we approached Bee Canyon, the trail leveled out and became a very pleasant walk.
We paused at the end of the hike near the trace of the Santa Susana Fault Zone while Gene discussed the possible origin of the fault and the adjacent fold structures. It was a good day on GeoTrek IV-F.

Return to the GeoTrek IV index.
THIS PAGE LAST MODIFIED ON JULY 2, 2011
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	GeoTrek IV-F participants gathered at the entrance to Towsley Gorge for a group photo. In the back row, left to right, are Mark Karagianus, John Klutke, Dick Squires, Sue Fritsche, Vicki Pedone, and Brian Swanson. In the front row, left to right, are Nellie Cussworth, Bob Ableson, Fred Nuesca, Lynn Sosa, and Syrus Parvizian. Gene took the photo.
	Roadcut on The Old Road north of Calgrove Blvd. near the contact between the Pliocene Pico Formation that was deposited in shallow ocean water and the younger Plio-Pleistocene Saugus Formation that was deposited by rivers on land. During the time of deposition the shoreline was migrating back and forth so that some of the rocks in this exposure were deposited in very shallow ocean water and others were deposited above the beach on land.
	Fossils found in the roadcut shown in the previous photo. The fossils are broken fragments of clams (bivalves) and snails (gastropods) that lived in very shallow water just on or below the beach.
	Sandstone and conglomerate in the Plio-Pleistocene Saugus Formation. The conglomerate was likely deposited in river channels right near the beach.
	After studying the Saugus Formation on The Old Road, we drove a short distance to the Ed Davis Park parking lot and hiked a short distance from there to Towsley Gorge. Here the group studies an excellent outcrop of the lower Pliocene Towsley Formation exposed in Towsley Gorge. The gorge formed because the Towsley Formation is much more resistant than the shale of the underlying Sisquoc Formation and the shale of the overlying Pico Formation.
	Interbedded sandstone (brown) and shale (gray) of the lower Pliocene Towsley Formation. The resistant areas that stick up above the rest of the rock are called concretions. They are more resistant because they contain a greater concentration of cement than the rest of the rock.
	Closeup of the Towsley Formation showing some thin shale beds that were eroded on the edge of a channel when the rock was deposited. Deposition was under the influence of turbidity currents in deep ocean water. As a turbidity current races down the ocean slope it erodes channels in the bottom sediment, as shown by the truncated (eroded) shale beds in this photo.
	Gene climbs up the outcrop to get a closer look at the sedimentary structures that were formed during deposition of the Towsley Formation. In front of his left leg is the flame structure shown in the next photo.
	In this photo, the older layers are on the left and the younger ones on the right. The structure shown is called a flame structure. The coarse-grained material in the center washed down the ocean slope in a dense turbidity current over the finer material on the left that was still unconsolidated and had a high water content. As the dense, coarse sediment deposited on the bottom it settled into the underlying sand which squirted up into the coarse sediment to form what looks like a flame.
	Luckily the creek in Towsley Gorge was small enough to hop across without getting our feet wet. Hiking through the gorge and seeing excellent exposures of the Towsley Formation was a pleasant and rewarding experience.
	After seeing Towsley Gorge, we drove to the East Canyon Motorway trailhead where the day's main hike started. The trail went uphill rather gently at first and was shady in some places. The Towsley Formation in this area was not as resistant and well exposed as it had been in Towsley Gorge.
	We found a spot in the shade on the East Canyon Motorway for lunch. From left to right are Sue, John, Brian, Vicki, Fred, and Lynn. The sandstone behind them belongs to a nonresistant part of the Towsley Formation.
	The Big Cone Fir in the center of the photo marks the trace of the hinge surface of the Oat Mountain Syncline. The photo is looking west from the East Canyon Motorway. The light colored, resistant beds in most of the photo belong to the lower Pliocene Towsley Formation. Rocks on the far edges of the photo belong to the upper Miocene Sisquoc Formation that contains deep-water, siliceous diatoms that were deposited in a basin plain environment. Where would you suggest that the contact between the two formations might be?
	Monkey Flowers were common along all the trails we walked on today.
	View of the western San Fernando Valley from near Mission Point. On the right in the foreground are roads of the Aliso Canyon Oil Field which is now used as a natural gas storage facility. Pore spaces in the rock that were previously filled with oil were evacuated when oil was pumped out of the Aliso Canyon Oil Field. Natural gas from various places in California is now being pumped into those pore spaces where it is stored until needed. The obvious road in the middle of the valley is Reseda Blvd. and the Santa Monica Mountains are in the background. GeoTrek IV-C began near the top of the Santa Monica Mountains near the end of Reseda Blvd.
	Hiking on the Corral Sunshine Motorway near Mission Point. Rocks in this area belong to the upper Miocene Monterey Formation which is slightly older than the Sisquoc Formation. Like the Sisquoc Formation, it was deposited in a deep-water basin plain environment.
	We had to follow a short detour along a narrow trail through the grasslands in order to get around the fence at the edge of the natural gas storage facility. The fence was put up after 9/11 to protect against terrorist incursions into the facility.
	The group pauses on the Corral Sunshine Motorway for a view of the San Fernando Valley.
	The trail between Mission Point and O'Melveny Park is very steep downhill and some of the participants started getting sore knees.
	View of the northern San Fernando Valley. In the midground are the Van Norman Reservoir and the city of San Fernando; in the background are the San Gabriel Mountains.
	View of the Sunshine Landfill in the eastern Santa Susana Mountains. This is where nonrecyclable trash from the San Fernando Valley is being deposited. In the background are the eastern Santa Monica Mountains.
	On the home stretch toward O'Melveny Park. As we approached Bee Canyon, the trail leveled out and became a very pleasant walk.
	We paused at the end of the hike near the trace of the Santa Susana Fault Zone while Gene discussed the possible origin of the fault and the adjacent fold structures. It was a good day on GeoTrek IV-F.