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EarthCache

Franciscan Complex - Fossils and Ash

A cache by cmilono
Hidden : 11/20/2006
In California, United States
Difficulty:
1 out of 5
Terrain:
3.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

Beach Location - medium hike on level ground, or semi-strenuous hike from cliffs (safe), depending on your starting point. At the coordinates posted above, you will see two very interesting geological formations - an ash bed and exposed fossils!



What you are seeing is found in the Merced Formation, which was deposited between 3 Million to as recently as 400,000 Years Ago! There are some age differences between what you see here and at the Merced Formation at Mussel Rock; as you walk South, you go back in time!

About seven feet from the top of the cliff, you will see a white band of strata; this is the famous Rockland Ash Layer, from a volcanic eruption of a volcano near Mt. Lassen about 600,000 years ago. There is another ash layer near the bottom of the cliff, or under several feet of sand, depending on the season and tide; this second layer is from an eruption in the Long Valley Caldera.

By your feet, tide permitting, you are looking at fossils from approximately 2.5 million years ago! Though there are some petrified fossils (see photos) throughout the area, what you see here are not petrified. A bit farther south, you can see parts of the Colma Formation.


The Coordinates might be "wet", so check first! Tides.Info: Tide Predictions for San Francisco, California

There are several ways to get to this Earthcache - from Thornton State Beach at the foot of John Daly Blvd. in Daly City (finding GCGXHT - "Old One", or GCRRFN - "This should be WalruZ's Cache"), or from Fort Funston in San Francisco. The approach from the Thornton State Beach origin is difficult to describe, but if you try it, you will be going North. From Fort Funston, the North Parking lot is near Sloat and the S.F. Zoo, and the South access point is a steep climb up/down a cliff (N 37° 42.759 W 122° 30.026 - GCG504 - "Fort Funston Webcam"), but you can see hang-gliders and R/C gliders/planes - and you will be going South.

There are some large fossils at:
N 37° 42.215
W 122° 30.053

Terrain Rating:
*.5 or ** from North Fort Funston
** or **.5 from South Fort Funston
*** or ****+ from Thornton State Beach (see comment for Old One: not recommended in wet weather. Rope assist was in place!) The Thornton State Beach access is very difficult and not recommended for the faint of heart or the foolish!
Proceed at your own risk.


Send me an email on the size of the fossils, and remark on what kind you think they are; please log the number of people in your group, and whether you saw any other interesting geological sights during your walk. If at all possible, take a picture of you and/or your group and post it!

Additional Hints (No hints available.)

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Inventory

There are no Trackables in this cache.

 

Find...

74 Logged Visits

Found it 70     Write note 3     Publish Listing 1     

View Logbook | View the Image Gallery of 111 images

**Warning! Spoilers may be included in the descriptions or links.

Current Time:
Last Updated: on 9/3/2014 10:25:08 AM Pacific Daylight Time (5:25 PM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum