TAPIA PARK TO
Monday, March 22, 2004
KANAN DUME ROAD
Monday, March 22, 2004
|Geological map above is from Thomas W. Dibblee Geological Foundation Maps DF-47 and DF-48. These maps may be purchased online from the Dibblee Geological Foundation branch of the Santa Barbara Museum of Natural History at: http://www.sbnature.org/dibblee/newweb/orderinfo.html.|
Participants met at the trail-head parking south of Tapia Park on Malibu Canyon Road and began the hike at 8:40 a.m. The hike was 12.0 miles in length and was exclusively on dirt roads and trails.
Everyone arrived on time for Day 5 of the hike and we started up the trail toward Castro Crest at 8:40 a.m. Participants for Day 5 are, left to right, John Alderson, Stan Walker, Sue Fritsche, and Gene Fritsche.
The trail proceeds up the north slope of the mountain to the crest and there are lots of shady areas in the oak and chaparral forest.
Looking back toward the east from half way up the mountain provides a view down into fog shrouded Malibu Canyon. The mountain top in the upper left is Saddle Peak which we passed on the north side on Day 4.
After reaching the crest of the mountain, the hike is more in the sun. It was a very warm day and we consumed a lot of water.
We passed the high point on our day's hike and after starting downhill we found a shady spot under some oak trees for lunch.
When we reached the Corral Canyon trailhead we were surprised to find a reporter, Augustín Durán, and a photographer, Chris Martinez, from La Opinión waiting for us. Here Gene is being interviewed by Augustín. After the interview in the trailhead parking area, Augustín and Chris accompanied us down the trail for about a quarter mile while Chris took abundant photographs and Augustín continued the interview. They were very pleasant people and a very nice article with a photograph appeared in the March 23, 2004 edition of La Opinión.
We reached the end of our longest day so far, 12 miles, at 5:15 p.m. We felt a little tired and grubby, but it had been a good day.
Adding to the flower pictures that were posted on Day 4, is this Prickly Phlox, that we saw commonly along the trail during Day 5. The scientific name is Leptodactylon californicum.
The Middle Topanga Formation, seen on Days 1 and 2, which consists of interbedded volcanic flow rocks and sedimentary shale and sandstone, is referred to in this vicinity as the Conejo Volcanics because the volcanic flow rocks dominate over the sedimentary rocks. In this photo, taken just west of the trailhead parking area, a dark gray basaltic lava flow on the left is overlain by sandstone and shale beds that are about 17,000,000 years old.
As the trail proceeds westward, it passes into older and older rocks. Underneath the Conejo Volcanics is the Lower Topanga Formation, which can be seen here to consist of alternating layers of shale (dark brown) and sandstone (light brown to light gray). These rocks range in age from 25,000,000 to 18,000,000 years old and were deposited in a shallow ocean environment, which is substantiated by the fossils which are illustrated below.
This photo shows where Lower Topanga Formation sandstone beds (white) were intruded along a fracture by a thick dike of melted rock that cooled to form the igneous rock called diabase (brown).
This Lower Topanga sandstone bed has sole marks on its bottom liked those described on Day 4. These marks are called flutes and were created by a current that flowed from upper left to lower right.
These fossils of assorted marine clams and snails prove that the Lower Topanga Formation was deposited in the ocean. Note that the shells of the fossils have all dissolved out of the rock leaving empty holes in their places. These holes in the rock are referred to as moldic porosity because each hole is a mold, which, if filled with some substance like plaster, would recreate the shape of the shell.
This photo shows two razor clams belonging to the genus Tagelus on the right and several, more rounded shells of the genus Dosinia on the left. Note that the shells of the clams have been disarticulated, indicating that they were transported in a moderately strong current for some distance before they were deposited.
This picture shows a large barnacle fossil in the Lower Topanga Formation along with fragments of several others. The scientific name of the genus is Balanus and these fossils prove that the water was very shallow.
The scientific name of this marine snail is Turritella ocoyana. These fossils only existed on the Earth for a short period of time, so they can be used to determine that these rocks were deposited during the middle part of the Miocene Epoch.
Underneath the Lower Topanga Formation are these pinkish-colored sandstone deposits called the Sespe Formation. They were deposited on a river floodplain during the period from 41,000,000 to 28,000,000 years ago.
Below the Sespe Formation is a dark shale unit called the Llajas Formation. The Llajas Formation was deposited in a quiet ocean environment between 50,000,000 and 48,000,000 years ago.
Near the end of the hike, we crossed the Malibu Bowl fault. A fault exists where rock units have broken (fractured) and the rocks have slid past one another along the fracture. When this happens, the rocks in some places along the fracture are broken into small fragments creating a rock called a breccia, like the one shown in this photo. In this area the rocks on the east side of the fault are the Sespe Formation and those on the west side are the Monterey Formation (see next photo).
The shale unit shown in this photo is called the Monterey Formation. It was deposited in a very deep ocean basin between 12,000,000 and 4,000,000 year ago. It is the same rock unit that was seen along Mulholland Drive on Day 2 of the hike.
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THIS PAGE LAST MODIFIED ON MARCH 23, 2004
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