GeoTrek IV-H

GEOTREK IV-H
WESTERN TOPATOPA MOUNTAINS

Saturday, May 14, 2011

Topic: Cretaceous and Eocene sedimentary and structural history of the Topatopa Mountains. Traverse from Sespe Creek at Lion Canyon to Ojai.

Participants: A record number of 24 participants attended GeoTrek IV-H, including Bob Ableson, Peggy Ahlstrom, Carrie Bender, Bob Blackmur, Ted Carlson, Joze Del Angel, Gene Fritsche, Doug Hammond, Connie Hanstedt, John Harris, Bill Harz, Dick Heermance, Pam Irvine, John Klutke, Jerry Nichols, Muriel Norton, Syrus Parvizian, Jane Rollins, Trevor Santochi, Yonni Schwartz, Mike Stella, Brian Swanson, Christine White, and Jeff Zane. See the first photo below (the group photo) to pick out these people.

Distance and Route: About 11 miles along the following trails: starting at Middle Lion Campground, east of Rose Valley and south of Sespe Creek, go south on Lion Canyon Trail (22W06), west on Nordhoff Road (5N08), and south on Horn Canyon Trail (22W08) to Thacher School. See Google Earth route map below.

Profile: On the profile below the start of the hike is on the left end. Total elevation gain was 2,498 feet and total elevation loss was 4,180 feet.

Geology: The hike was on the Dibblee Lion Canyon quadrangle (DF-14) and the Ojai quadrangle (DF-13). Formations we saw included an unnamed Upper Cretaceous marine unit, the lower to middle Eocene Juncal Formation, the middle to upper Eocene Matilija Formation, and the Sana Ynez Fault. Depositional environments, stratigraphic problems, and structural history of the area were reviewed.

PHOTOS TAKEN IN THE WESTERN
TOPATOPA MOUNTAINS ON GEOTREK IV-H
Photos taken by Gene Fritsche, Doug Hammond, Jane Rollins, and Brian Swanson.
Click on the small picture to see an enlargement.

Group photo at the start of GeoTrek IV-H at Middle Lion Campground near Sespe Creek. There were 24 participants on this hike, the largest number to ever attend one of the GeoTrek hikes.
Immediately after leaving the parking area at Middle Lion Campgound we came to Lion Creek, which had to be crossed. In this photo some of the group are looking for the best route.
Some of the group were able to boulder-hop across the creek; others took the more secure, but wetter route.
After crossing Lion Creek we began our climb up to the Topatopa Mountains crest, which was half a day away. A group on horseback caught up to us, so we moved over and let them pass.
The Ceanothus bushes along the trail were in full bloom and the flowers that at first bloom are white, had turned to purple.
The Ceanothus blossoms made the trail quite colorful.
The group pauses along the trail while Gene describes a landslide-dammed Pleistocene lake that used to exist in this area. Unfortunately the lake deposits were overgrown with so much brush that we could not get to them.
At this point Gene missed a fork in the trail. As a result we walked an extra half a mile. Here we stopped to regroup and Gene points to the correct trail thanks to the help of those who saw the correct trail the first time we went by it.
South of the Santa Ynez Fault we crossed into an unnamed Cretaceous unit. It consists of interbedded conglomerate, sandstone, and shale beds that were deposited in a submarine fan and channel environment. In this photo the group pauses to study an exposure of the conglomerate.
Closeup view of the Cretaceous conglomerate. These rocks were most likely deposited in a submarine fan channel.
Typical exposure of the black, thin-bedded shale in the unnamed Cretacous unit.
Closeup view of the shale in the unnamed Cretacous unit. The shale was likely deposited on the distal fringe of a submarine fan lobe.
Closeup view of some sandstone beds in the unnamed Cretacous unit.
Contact between the unnamed Cretaceous unit on the left and the lower to middle Eocene Juncal Formation on the right. The Cretaceus unit is mostly shale here, whereas the Juncal Formation contains interbedded sandstone units. Where would you draw the contact? See next photo.
Gene would draw the contact as shown by the black line. This decision is based on vegetation and color differences on the side of the mountain and would have to be checked by actually crossing the canyon and looking at the rocks.
The group takes a break while studying the contact seen in the previous photo. The rocks under their feet are shale beds of the Juncal Formation. They are similar to shale beds in the Cretaceous rocks, but can be differentiated by the microfossils they contain.
A thick-bedded sandstone portion of the Juncal Formation. Thick sandstone units such as this do not occur in the Cretaceous rocks.
Mountainside exposure of the lower to middle Eocene Juncal Formation. The formation consists of alternating portions of slightly more resistant, less vegetated sandstone and less resistant, vegetated shale.
A typical exposure of the lower to middle Eocene Juncal Formation, like this one, consists of alternating beds of sandstone and shale. Like the Cretaceous rocks, the Juncal Formation was deposited in a submarine fan environment.
Closeup view of a Juncal sandstone bed.
We reached the crest of the Topatopa Mountains, the high point on our hike, and immediately settled down for lunch. It wasn't a greatly picturesque spot sitting along the edge of the ridgetop road, but we were starved by the time we got there and couldn't go a step farther.
During lunch the cloud tops of the marine layer reached the ridgeline. During the rest of the afternoon we were mostly under the clouds of the marine layer.
For a short time after lunch we hiked along the road on the ridgeline where the hiking was more level. The morning had been mostly uphill and soon we would be going mostly downhill.
In addition to the purple Ceanothus, this yellow-flowered bush was very common along the trail.
Closeup of the flowers on the yellow-flowered bush.
We leave the ridgeline road and begin our downhill hike to Ojai. The clouds were still waiting ahead to hover over our heads.
A time of rejoicing came when we discovered that we had completed 7 miles and only had 4 miles to go to Thacher School.
We stopped for a second group photo at the "four-miles-to-go" sign. The most important thing was that there were still 24 of us.
Purple pom-pom flowers of the buckwheat plant, which is common throughout southern California.
This white Mariposa Lily with a red center was especially beautiful. Unfortunately there were very few of them.
As we continued on down the trail the folks at the front of the pack were still smiling (at least for the camera), but the distance from the front to the back of the pack was lengthening.
We found this purple-flowered bush along the trail as we got to lower elevations.
The beauty of these flowers is enhanced by the contrast of the yellow centers with the purple flowers.
We took a break at The Pines Camp in order to let the back of the pack catch up. We still had two miles to go.
Eventually we reached a point where we could see the Ojai Valley below us. Many in the group were looking forward to the finish.
Outcrop of the middle to upper Eocene Matilija Formation in Horn Canyon. The Matilija Formation is the most resistant formation in this part of the Transverse Ranges and is composed mostly of thick beds of sandstone.
Connie Hanstedt, one of the hikers, works at Thacher School. She arranged to have "snacks" available for us at Thacher when we finished the hike. The snacks, including sandwiches, salads, and fruit punch, turned out to be enough for dinner. We all thank Connie for a delightful end to GeoTrek IV-H.
This hike over the Topatopa Mountains was probably the most difficult of the GeoTrek IV series, but even though our feet and legs were tired, our full stomachs brought smiles to our faces. Connie, our dinner provider, is on Gene's right side.

THIS PAGE LAST MODIFIED ON JULY 20, 2011
If you have questions or comments, you may leave a message at:
geneandsuef@dslextreme.com

	Group photo at the start of GeoTrek IV-H at Middle Lion Campground near Sespe Creek. There were 24 participants on this hike, the largest number to ever attend one of the GeoTrek hikes.
	Immediately after leaving the parking area at Middle Lion Campgound we came to Lion Creek, which had to be crossed. In this photo some of the group are looking for the best route.
	Some of the group were able to boulder-hop across the creek; others took the more secure, but wetter route.
	After crossing Lion Creek we began our climb up to the Topatopa Mountains crest, which was half a day away. A group on horseback caught up to us, so we moved over and let them pass.
	The Ceanothus bushes along the trail were in full bloom and the flowers that at first bloom are white, had turned to purple.
	The Ceanothus blossoms made the trail quite colorful.
	The group pauses along the trail while Gene describes a landslide-dammed Pleistocene lake that used to exist in this area. Unfortunately the lake deposits were overgrown with so much brush that we could not get to them.
	At this point Gene missed a fork in the trail. As a result we walked an extra half a mile. Here we stopped to regroup and Gene points to the correct trail thanks to the help of those who saw the correct trail the first time we went by it.
	South of the Santa Ynez Fault we crossed into an unnamed Cretaceous unit. It consists of interbedded conglomerate, sandstone, and shale beds that were deposited in a submarine fan and channel environment. In this photo the group pauses to study an exposure of the conglomerate.
	Closeup view of the Cretaceous conglomerate. These rocks were most likely deposited in a submarine fan channel.
	Typical exposure of the black, thin-bedded shale in the unnamed Cretacous unit.
	Closeup view of the shale in the unnamed Cretacous unit. The shale was likely deposited on the distal fringe of a submarine fan lobe.
	Closeup view of some sandstone beds in the unnamed Cretacous unit.
	Contact between the unnamed Cretaceous unit on the left and the lower to middle Eocene Juncal Formation on the right. The Cretaceus unit is mostly shale here, whereas the Juncal Formation contains interbedded sandstone units. Where would you draw the contact? See next photo.
	Gene would draw the contact as shown by the black line. This decision is based on vegetation and color differences on the side of the mountain and would have to be checked by actually crossing the canyon and looking at the rocks.
	The group takes a break while studying the contact seen in the previous photo. The rocks under their feet are shale beds of the Juncal Formation. They are similar to shale beds in the Cretaceous rocks, but can be differentiated by the microfossils they contain.
	A thick-bedded sandstone portion of the Juncal Formation. Thick sandstone units such as this do not occur in the Cretaceous rocks.
	Mountainside exposure of the lower to middle Eocene Juncal Formation. The formation consists of alternating portions of slightly more resistant, less vegetated sandstone and less resistant, vegetated shale.
	A typical exposure of the lower to middle Eocene Juncal Formation, like this one, consists of alternating beds of sandstone and shale. Like the Cretaceous rocks, the Juncal Formation was deposited in a submarine fan environment.
	Closeup view of a Juncal sandstone bed.
	We reached the crest of the Topatopa Mountains, the high point on our hike, and immediately settled down for lunch. It wasn't a greatly picturesque spot sitting along the edge of the ridgetop road, but we were starved by the time we got there and couldn't go a step farther.
	During lunch the cloud tops of the marine layer reached the ridgeline. During the rest of the afternoon we were mostly under the clouds of the marine layer.
	For a short time after lunch we hiked along the road on the ridgeline where the hiking was more level. The morning had been mostly uphill and soon we would be going mostly downhill.
	In addition to the purple Ceanothus, this yellow-flowered bush was very common along the trail.
	Closeup of the flowers on the yellow-flowered bush.
	We leave the ridgeline road and begin our downhill hike to Ojai. The clouds were still waiting ahead to hover over our heads.
	A time of rejoicing came when we discovered that we had completed 7 miles and only had 4 miles to go to Thacher School.
	We stopped for a second group photo at the "four-miles-to-go" sign. The most important thing was that there were still 24 of us.
	Purple pom-pom flowers of the buckwheat plant, which is common throughout southern California.
	This white Mariposa Lily with a red center was especially beautiful. Unfortunately there were very few of them.
	As we continued on down the trail the folks at the front of the pack were still smiling (at least for the camera), but the distance from the front to the back of the pack was lengthening.
	We found this purple-flowered bush along the trail as we got to lower elevations.
	The beauty of these flowers is enhanced by the contrast of the yellow centers with the purple flowers.
	We took a break at The Pines Camp in order to let the back of the pack catch up. We still had two miles to go.
	Eventually we reached a point where we could see the Ojai Valley below us. Many in the group were looking forward to the finish.
	Outcrop of the middle to upper Eocene Matilija Formation in Horn Canyon. The Matilija Formation is the most resistant formation in this part of the Transverse Ranges and is composed mostly of thick beds of sandstone.
	Connie Hanstedt, one of the hikers, works at Thacher School. She arranged to have "snacks" available for us at Thacher when we finished the hike. The snacks, including sandwiches, salads, and fruit punch, turned out to be enough for dinner. We all thank Connie for a delightful end to GeoTrek IV-H.
	This hike over the Topatopa Mountains was probably the most difficult of the GeoTrek IV series, but even though our feet and legs were tired, our full stomachs brought smiles to our faces. Connie, our dinner provider, is on Gene's right side.