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Department of Geological Sciences

18111 Nordhoff Street
Northridge
CA 91330-8266

Phone: (818) 677-3541
E-mail: geology@csun.edu

LO 1202

Hours:
Mon-Fri 8:00am-5:00pm

Our first stop was near the beach at Loon Point. Dick Heermance gave an overview of the regional geology and explained how the Santa Barbara fold-and thrust-belt is effected by compressional shortening as a result of the bend in the San Andreas fault.

Along the beach we looked at the exposure of the Loon Point fault (which runs from upper left to near bottom center of photo). The fault places the terrestrial Pleistocene Casitas formation (right side in photo) with its overlying marine terrace deposits over the marine Santa Barbara formation (left side in photo).

Farther up the coast we stopped at Vandenberg Air Force Base to look at the Point Sal ophiolite. Base geologist Kathy Gerber (CSUN Geology '83) coordinated our efforts to get on the base and visit Point Sal. At our first stop near the foot of Lions Head Doug Yule gave an overview of the Coast Range ophiolite, Franciscan assemblage, and Great Valley sequence.

Along the seacliff in the lower cumulate section of the ophiolite we saw mostly serpentinized peridotite and altered microgabbroic dikes (of the lower dike series). Many of the dikes have been altered to rodingite.

At the next stop we encountered gabbro with a conspicuous igneous lamination. Here Elena Miranda talks about the interaction between the gabbro and the dark inclusions composed of peridotite.

At Point Sal beach we walked along the sand and watched the sea lions and dolphins frolicking in the ocean.

A dike complex is exposed in the cliffs at the far end of the beach. This mass of dikes separates the diorite and gabbro rocks from the overlying volcanic rocks. Here a student photographs of one of the dikes with chilled margins.

Access to some of the outcrops was challenging. Here Doug Yule takes an alternate route up the cliff.

We camped at Montana de Oro State Park. The next morning we did some beach combing. Most of the surrounding outcrops consisted of Monterey Shale.

Doug Yule gave a summary of the regional geology and then presented three competing models for the origin of the Coast Range ophiolite.

Our next stop was Morro Rock. The Morro Rock-Islay Hill intrusive complex consists of a chain of 25 Ma dacite to rhyodacite hypabyssal intrusions. Magma for these intrusions may have been generated by decompression melting of an upwelling mantle within a slab window that was proximal to a ridge-trench boundary.

At the beach at Cayucos Elena Miranda points to the "tail" on the bottom of a pillow lava. She explained that new pillows while still hot and somewhat plastic will conform to underlying surfaces. If a new pillow flows over two existing pillows it will fill the triangular void between them forming a "tail". This feature can be used as a top indicator.

At Wallace Creek on the Carrizo Plain Doug Yule spoke about stream channel offsets, fault slip rates, and how recurrence rates are determined. We walked along the trace of the San Andreas fault and looked for the offset from the 1857 earthquake.

In a little valley at the southern end of the Elkhorn Hills we stopped to view a sag pond (green area near center of photo) and a rhombochasm (white area at center left) along the San Andreas fault.

We camped in the San Emigdio Mountains. The next morning we drove through a lot of Sespe and Matilija rocks then stopped at Wheeler Gorge.

Dick Heermance describes the Cretaceous deep-water system. The rocks are interpreted to be a levee-channel complex of a deep-water fan.

Students inspect the cobble and pebble conglomerate. The conglomerate is interpreted as fill within the levee-channel complex.

Dick Heermance describes the submarine channel and Bouma sequence turbidites.

Vicki Pedone explains the significance of graded bedding and flame structures as top indicators in the turbidite.

Near the east end of the Casitas Reservoir we stopped to look at the Ventura River terraces. The terraces have been uplifted as a result of active faulting and folding over the last 2 Ma. Terrace ages and uplift rates have been used to infer slip rates on local faults. Dick Heermance explained how the terraces are dated. His recent cosmogenic dating of terrace boulder samples indicate that the slip rates may be higher than previously determined.

At the conclusion of the Fall Field Frolic we had a barbecue in the CSUN Botanic Gardens.