Tuesday, September 7, 2010

Toll House

I have seen quite a bit of the geology of Curry County and started to look into the literature. Also, I have ideas about GIS innovations and here are a few emergent technologies that are worth mentioning.

ArcGIS for iPhone   |   Photosyth   |   Seadragon

My interests remain the development of a new software paradigm for digital photogrammetry that builds elevation models from historic air photos as well as traditional photography, and excitingly, hand held digital photography (photosynth).

Time for dessert!
Toll house cookies, Andrew D. Barron ©9/7/10
Toll house cookies, Andrew D. Barron ©9/7/10

The connection is that a Toll House cookie is analogous to rocks of the Gold Beach terrane. Many different ingredients from very different places combined, stirred, heated, and their consistency changed. Then moved from a pile of dough to be baked (metamorphosed), and come out as cookies (outcrops). Can you imagine tracing the source of one chocolate chip in one of the cookies or a speck of baking powder? That is what geologists are often working with.

I spend a lot of time between Sisters Rocks and Otter Point and think of this geology as a Franciscan-type chaotic mélange. The rocks remind me of my work on the western edge of Tehama county in 1996. For that project, I developed my first GIS. That paper is available here, though without figures. Turns out that the Otter Point formation probably is Franciscan mélange. Paleomagnetic work by M.C. Blake suggest significant northward translation (1200-1400 km) of the Gold Beach terrane. It's Californian! Work is still being done on the terrane's origin. It's a little hard for the curious geologist without access to Georef to chase the literature very far.

Here is what Ernest H. Lund had to say about the Otter Point formation, from April 1975's, The Ore Bin.

The Otter Point Formation crops out in a belt that extends from Whalehead Cove on the south to Sisters Rocks on the north. It is not continuous along the shore over the entire distance but is interrupted at a number of places by younger formations. To the north, it crops out in The Heads at Port Orford; most of the reefs and sea stacks from Mack Reef northward are of Otter Point rocks.

The Otter Point Formation consists of a very complex mixture of folded and sheared mudstone, sandstone, conglomerate, and volcanic rock. During deformation, serpentinized peridotite, phyllite, and glaucophane schist from other formations mixed with the Otter Point rocks; the whole assemblage has been aptly referred to as chaotic.

The name mélange has been applied to churned-up assemblages of this type. The Otter Point Formation has been lightly metamorphosed. Where the rock is not sheared, it is hard and very resistant to erosion, especially the volcanic units, but where it is severely sheared, it has little strength and is easily eroded. Weathering further weakens the sheared rock, making landslides a serious problem. Landslides have damaged the highway at numerous places where it crosses this formation.

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