The Dinkey Creek Roof Pendant
Posted by: Groundspeak Premium Member TerryDad2
N 37° 09.078 W 119° 06.275
11S E 313102 N 4113730
Quick Description: The Dinkey Creek Roof Pendant is described as the remnant of a layer of meta-sediments that were above the Dinkey Creek Pluton that intruded underneath them. These rocks have been folded three different ways.
Location: California, United States
Date Posted: 1/1/2010 9:01:38 PM
Waymark Code: WM8078
Published By: Groundspeak Premium Member condor1
Views: 9

Long Description:
The Dinkey Creek Roof Pendant is accessible by unpaved Forest Service access roads. The roads do get pretty rough, so a high clearance vehicle would be a very good idea. There is a large parking area near the coordinates. There are a number of coordinates to visit that are all within 0.2 of a mile, but are on relatively steep slopes. Because you will be looking at the rocks, the Waymark is unavailable during the winter since the rocks will be covered with snow.

The Dinkey Creek Roof Pendant includes, schist, quartzite, hornfelds, calc-silicate rocks, and marble. These rocks are thought to have been originally deposited sometime between the Paleozoic (visit link) and the Cretaceous Period (visit link) of the Mesozoic (visit link) in a shallow marine area. That age range would be anywhere between 524 to 146 million years ago.

Following deposition, the sediments underwent a series of deformations. First they were folded at least 3 times. Then, with the intrusion of the Dinkey Creek Pluton, the sediments were subjected to contact metamorphism (visit link) becoming the meta-sediments we see today.

Then, the Sierra Nevada Mountains were uplifted and erosion removed the overlying meta-sediments. Today almost all of the meta-sediments have been eroded leaving the granite of the Dinkey Creek Pluton exposed at the surface. Only the roof pendants, the portions that stuck down into the Dinkey Creek Pluton, remain.

So what is a Roof Pendant? When the Dinkey Creek Pluton expanded out horizontally, it flowed along a contact between an existing pluton and the series of meta-sediments that overlied the older plutonic body. Since the meta-sediments were on top of this magma that would become the Dinkey Creek Pluton, the meta-sediments are considered the roof of the intrusion. The roof was not completely flat, so portions protruded down into the magma like a necklace pendant. Putting the two descriptions together, we get a roof pendant.

The following is a short description of the rocks in the Dinkey Creek Pluton (in order from oldest to youngest)

The Marble (visit link) (N37 09.125 W119 06.265)
This is a grayish rock that I found to have no distinct characteristics except for the many quarts veins running through it.

The Calc-Silicate Rocks (A, N37 09.010 W119 06.253 and N37 09.072 W119 06.199)
This group of rocks is separated into a lower and upper member separated by a sill of diorite (visit link) The lower (older) member is made up of layers of marble and two types of hornfels (visit link) The marbles are grayish and the hornfels are reddish-brown. The upper (younger) member also is made up of marble and hornfels. But the marble is a light tan to gray and the hornfels are greenish. The multiple episodes of folding can be seen throughout the calc-silicate rocks

Biotite-Andalusite Hornfels (N37 09.055 W119 06.155)
Originally this rock was a shale or mudstone that was very uniform. Now the individual beds are very difficult to discern so the rock looks like a gray non-descript rock. You can find the folding when looking carefully and from the fracturing.

White Quartzite (visit link) (further to the east)
This is a light gray to light tan rock. Crossbeds can still be found within the metamorphosed sandstone.

Schist (visit link) (East of the Quartzite)
This rock composed of layers of dark schist and light tan quartzite. Much of the layering in this rock has been affected by the folding and contact metamorphism such that it is not readily recognizable.

Sources:
Kistler R.W, and P.C. Bateman; Stratigraphy and Structure of the Dinkey Creek Roof Pendant in the Central Sierra Nevada, California; Geologic Survey Professional Paper 524-B; includes foldout map; 1966
Petford, N., Cruden, A., McCaffrey, K and Vigneresse, J-L., Granite magma formation, transport and emplacement in the Earth's crust, Nature, V. 408, p. 669-673, December 2000.
Waymark is confirmed to be publicly accessible: yes

Requires a high clearance vehicle to visit.: yes

Requires 4x4 vehicle to visit.: no

Public Transport available: no

Website reference: [Web Link]

Parking Coordinates: Not Listed

Access fee (In local currency): Not Listed

Visit Instructions:
No specific requirements, just have fun visiting the waymark.
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