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UCMP's Spring Break 2015 southern California field trip, page 1

by Dave Smith, with contributions from Lisa White

Assistant Professor Seth Finnegan led an instructive and enjoyable field trip to the Kettleman Hills and Death Valley over Spring Break in 2014 and grad students and staff spent the rest of the year eagerly awaiting news about the next one.

Seth, in consultation with Assistant Professor and paleobotanist Cindy Looy, announced that the 2015 field trip would be to more localities in southern California. Seth's objective in offering these field trips has been to "give UCMP graduate students … experience in looking at fossils in the field," with an emphasis "on stratigraphy and interpretation of the depositional environment, taphonomy, ichnology and paleoecology."

By adding more structure to the 2015 field trip, the trip itself was the focus of a spring semester seminar in which grad students could enroll. In weekly meetings leading up to the trip, pairs of grad students researched the formations and regions that the group would visit and gave short presentations on those areas.

In early March, the itinerary was finalized, arrangements for lodging had been made, three SUVs had been rented, and the necessary supplies were obtained. On Saturday, March 21, 15 people rendezvoused at the West Circle on campus. After filling all water jugs and stowing the gear, the group — in two private vehicles and the SUVs — left campus around 9:00 AM and headed south. Assistant Director for Education and Public Outreach Lisa White was in her car with Museum Scientist Erica Clites; grad student Rosemary Romero rode with fellow student Renske Kirchholtes. Seth and grad students Dori Contreras, Zixiang Zhang, and Emily Orzechowski were in the white SUV; in the black one were grad students Ash Poust, Caitlin Boas, and Jeff Benca; and Cindy was in the silver SUV with graphic designer Dave Smith, and grad students Camilla Souto and Natalia Villavicencio. Like the previous year, each vehicle was equipped with a walkie talkie, courtesy of Lisa, which again proved invaluable.

The group arrived at its first locality on Arroyo Seco Road, just south of Soledad in Monterey County, right around noon. The cars parked on the shoulder at a point where the road cut through a southeasterly dipping sequence of siliceous, diatom-rich mudstones of the extensive Monterey Formation. Lisa had taken many a student group to this locality in the past and predicted that we'd find small pea crab fossils. Dori was the first to approach the exposure and she picked one (a crab fossil) up within a matter of seconds. This discovery was followed by many more, as the fossil crabs — each being about an inch across — were quite abundant. Lisa explained that these deposits had formed in a deep marine basin (the Salinas Basin) during the middle to late Miocene.

Going over our route at the West Circle Our first stop on Arroyo Seco Road Fossil pea crabs
Click on any photo in this story (with one exception) to see an enlargement. Left: Having gathered at the West Circle on the Berkeley campus, the drivers go over our proposed route on the map. Photo by Erica Clites. Middle: Our first stop along Arroyo Seco Road south of Soledad. The crab fossils were found in the road cut at the left. Photo by Erica Clites. Right: A slab containing several complete and partial crab fossils. Photo by Camilla Souto.

After a roadside lunch of sandwiches, the group moved about a mile farther down the road where a different assemblage of fossils were found. Here, in an older sequence of the Monterey Formation, a number of bivalves, gastropods, and brachiopods (an unusual find in Miocene rocks) were identified. The time spent at this locality was cut short when a nearby resident complained about where we'd parked our vehicles. So the caravan went into the town of Greenfield to gas up before continuing south on Route 101 for another three hours.

The group at the second Arroyo Seco locality
A nice bivalve fossil
Lisa with Emily and Rosemary
Fossil scallops
Dori with fossils
Caitlin with fossil scallops
Top left: The group looks for fossils in a second road cut along Arroyo Seco Road. Photo by Cindy Looy. Top middle: Lisa points out some fossils to Emily and Rosemary. Photo by Cindy Looy. Top right: Dori's found some cool fossils! Photo by Cindy Looy. Bottom left: A nice fossil bivalve. Photo by Erica Clites. Bottom middle: Nicely preserved fossil scallops. Photo by Erica Clites. Bottom right: Caitlin with more fossil scallops. Photo by Cindy Looy.

At Los Olivos, the group exited and made its way to the Sedgwick Reserve, a real gem in the UC Natural Reserve System. The group stayed in the reserve's sprawling Ranch House, surrounded by mixed oak woodland and grassy fields. There were plenty of sleeping spots for everyone, both indoors and out (some chose to pitch their tents). Lisa and Erica were the principal chefs this first night, preparing an amazing dinner of burritos.

The Ranch House at UC's Sedgwick Reserve
The awesome Ranch House at UC's Sedgwick Reserve where we spent two nights. Photo by Dave Smith.

Sunday, March 22
With everyone squeezing into four vehicles (Renske's car was left at the reserve), the group drove to Solvang to pick up grad student Lucy Chang, who had taken an overnight bus down from the Bay Area. After grabbing some coffee and pastries at Olsen's Bakery, everyone (we now numbered 16) drove on to Gaviota State Park, 33 miles west of Santa Barbara. With clipboards and makeshift Jacob staffs in hand, Seth took us out to the beach, where we walked east along the coastal cliffs. These were spectacular, south-dipping layers of more of the the Monterey Formation's siliceous facies. We were reminded that the Monterey Formation is the principal source of oil in California, a fact brought home by the presence of offshore drilling platforms. Although Miocene in age like the Salinas Basin rocks to the north, the Monterey rocks here accumulated in another basin, the Santa Barbara Basin, and at deeper depths. Seth and Cindy divided the students into groups of two and had them try their hands at measuring some sections using the Jacob staffs, with an emphasis on interpreting the origins of the layers they were examining.

After a quick lunch back at the vehicles, we returned to the beach and headed to the west side of the Gaviota pier. Here, Seth brought us to an exposure quite different from what we had seen earlier in the day. A dark mass of variable texture seemed to cut across the typical buff-colored rocks of the Monterey Formation. It was explained that we were looking at a marine channel fill. This and two other such fills farther along the beach were described in a 2007 paper by Surpless et al.1

Walking along the beach at Gaviota State Park
Jeff and Erica record their observations
Camilla and Caitlin measure a section
Seth splits the students into groups of two to measure sections
Offshore oil rigs remind us that the Monterey Formation is the primary source of oil in California
Lisa takes a strike and dip measurement
Checking out a submarine channel fill deposit
Top left: Walking along the beach at Gaviota State Park with its great exposures of the Monterey Formation. Photo by Cindy Looy. Top middle: Seth splits the students into groups of two to measure sections. Photo by Erica Clites. Top right: Lisa takes a strike and dip measurement. Photo by Camilla Souto. Center left: Jeff and Erica record their observations. Photo by Camilla Souto. Center, far right: Checking out a submarine channel fill deposit. Post-deposition infiltration of oil into the porous sediments is what gives it that black color. Photo by Cindy Looy. Bottom left: Camilla and Caitlin measure a section. Photo by Cindy Looy. Bottom middle: An offshore oil rig on the horizon reminds us that the Monterey Formation is the primary source of oil in California. Photo by Camilla Souto.

Fossils found at Gaviota State Park
Three fossils found at Gaviota State Park include (from left) an alga, fish head, and a fish scale. Photos by Camilla Souto.

From Gaviota, we attempted to gain access to the classic Naples Beach locality a couple miles west of Goleta, but it appeared to be private property, so we went to Plan B and drove to El Capitan State Beach, a few miles back along 101. Again, we encountered excellent coastal exposures of the siliceous Monterey Formation. We had seen some macrofossils at Gaviota, but they appeared to be more common at El Capitan. A few minutes of searching turned up fossils of algae, fish, and a few unidentifiable organisms.

We returned to the vehicles around 5:00 and drove back to the Sedgwick Reserve. Dori and Jeff collaborated on dinner preparation.

Enigmatic fossils from El Capitan State Beach Fossil fish vertebrae and ribs from El Capitan State Beach
Looking for fossils at El Capitan State Beach
Fossil algae from El Capitan State Beach
Fossil algae from El Capitan State Beach
Algae and unidentified fossil from El Capitan State Beach
Possible fossil bryozoan from El Capitan State Beach
Fossil fish vertebrae and tail from El Capitan State Beach
Preparing dinner in the Sedgwick Reserve's Ranch House
All the fossils pictured in this block were found at El Capitan State Beach. Top left: Unidentified fossil. Photo by Cindy Looy. Top right: Fossil fish vertebrae and ribs. Photo by Rosemary Romero. Center left: Looking for fossils at El Capitan State Beach. Photo by Dave Smith. Center middle (two photos): Nice specimens of fossil algae. Top photo by Cindy Looy; bottom one by Rosemary Romero. Center right: Fossil fish vertebrae and tail. Photo by Rosemary Romero. Bottom left: Another nice fossil alga. Photo by Cindy Looy. Bottom middle: Interesting, but unidentified, fossil; a bryozoan perhaps? Photo by Cindy Looy. Bottom right: Jeff (left) and Dave assist Dori in preparing dinner back at the Sedgwick Reserve's Ranch House. Photo by Cindy Looy.

Monday, March 23
People started moving around 7:00 AM, and after a simple breakfast and cleaning of the Ranch House, we were on the road by 8:30 or so. We drove north up 101, gassed up in Santa Maria, turned east on State Route 166 — a very scenic route — and hit Interstate 5 north of the Grapevine. We then turned south and exited a few miles south of Pyramid Lake on Golden State Highway2. We followed the road north as far as we could but barriers blocked the way a couple miles from Pyramid Lake Dam. We were now in Piru Gorge, near the western side of Ridge Basin, an elongate Miocene basin that filled with about 14,000 meters of sediment during a seven-million-year period. The basin formed by the stretching and sinking of crust along a bend in the San Gabriel Fault. The basin's sediments show a transition from marine to lake and river sources.

UCMP alum Daniel Axelrod (A.B., 1933; M.A., 1936; Ph.D., 1938) described some plant fossils collected in Piru Gorge in a 1982 paper3 and Seth and Cindy were hoping that we could rediscover some of his localities. After a quick lunch by the cars, we struck off north up the road to explore some likely (and accessible) exposures. Although some evidence of plant fossils was found, we soon came to the conclusion that finding Axelrod's localities would be like finding a needle in a haystack. It was at this point that Renske and Rosemary departed because of other obligations back in the Bay Area. The rest of us returned to the cars and crossed to the east side of I-5. Seth hoped to take us to a locality where Pliocene stromatolites, formed near the eastern shore of the lake occupying Ridge Basin at that time, could be seen. Unfortunately, a gate with multiple padlocks blocked the road, but all was not lost. Backtracking a bit down Old Ridge Route Road, we enjoyed examining road cuts that exhibited some very nice sedimentary structures. Also along the road, an enormous black feather was found — it was assumed to be from a condor, based on size alone. This probably was correct, since the Sespe Condor Sanctuary is located only about ten miles to the southwest.

Lunch at the cars in Piru Gorge Setting off to look for Axelrod's plant localities
What caused these ripple-like markings is unknown Erica looks for plant fossils on a slope east of the road A fossil oak leaf and twigs
Top left: Having lunch at the cars before exploring Piru Gorge. Photo by Cindy Looy. Top right: The group sets off to look for Axelrod's plant localities. Photo by Erica Clites. Bottom left: Unusual ripple-like markings on a rock in Piru Gorge. Photo by Dave Smith. Bottom middle: Erica looks for plant fossils on a slope east of the road. We were not far from I-5 — note the 18-wheeler driving by at the far left. Photo by Dave Smith. Bottom right: A fossil oak leaf and twigs from Piru Gorge. Photo by Cindy Looy.

A view to the north across the hills of the Ridge Basin A road cut exhibiting many nice geological features
Seth and Cindy examine the exposure
A bed with ripple marks on both top and bottom
A chunk of rock from the road cut that exhibits X Jeff holds a condor feather
Top left: A view looking north across the eroded hills of the Ridge Basin, as seen from Old Ridge Route Road. Photo by Dave Smith. Top right: A road cut east of I-5 on Old Ridge Route Road exhibiting many nice sedimentary features. Photo by Cindy Looy. Center left: Caitlin (left) looks on as Seth and Cindy discuss the geology. Photo by Dave Smith. Bottom left: In cross-section, the layer at the center is seen to have ripple marks on both its top and bottom surfaces. Photo by Dave Smith. Bottom middle: This chunk of rock from the road cut exhibits Liesegang rings. Photo by Cindy Looy. Bottom right: Jeff holds a condor feather that was found by the side of the road. Photo by Dave Smith.

That evening we were to be the guests of Integrative Biology grad student Shawn Shirazi, who generously offered to let us stay at his home in Yorba Linda, just northeast of Anaheim. Getting there meant crossing the Los Angeles basin, known for its many highways choked with slow-moving traffic, but for whatever reason, we were extremely fortunate and encountered few problem areas. Before heading to Shawn's, we all rendezvoused at a mall in Valencia where we had a nice dinner at The Fishtail Grill. From there it was a straight shot to Yorba Linda. Shawn's place was not the kind of lodgings field trip participants are used to (see photo on next page) but the hospitality and showers were most welcome!

1 Surpless, K.D., R.B. Ward, and S.A. Graham. 2007. Evolution and stratigraphic architecture of marine slope gully complexes: Monterey Formation (Miocene), Gaviota Beach, California. Marine and Petroleum Geology 26:269-288.
2 The Golden State Highway, or U.S. Route 99, was one of the first national highways commissioned in 1926. It ran from the Mexican border all the way to Canada, primarily along the present rout of Insterstate 5. Read more about this highway.
3 Axelrod, D.I. 1982. Vegetation and climate during middle Ridge Basin deposition. Pp. 247-252 in J.C. Crowell and M.H. Lisk (eds.), Geologic History of Ridge Basin, Southern California. Pacific Section, Society of Economic Paleontologists and Mineralogists.