NL - Last Granite EarthCache

This is an earthcache.  That means there is NO container.  There is instead a geology lesson to be learned.  There is a 1.5 round trip hike/beach walk to GZ.

Lumsden is home to one of the neatest example of what post-tectonic granite looks like when the conditions exist to let the crystals form over a long period of time.

Logging Requirements:

1. Find the outcrop.  Determine the following:
   1. Which of the minerals (mentioned in the description) is the most dominate in the exposure?
   2. How large are the largest crystals at GZ?  Why do you believe they are that size (see description)
   3. Are the largest crystals well ordered  (in neat “similar sized rows”) or randomly arranged with a wide range of sizes and vertical orientations?  Why?

Geology:

The Gander Zone, of which Lumsden is near the Northern terminus, houses the very northern part of the Appalachian Mountains that spread from Georgia USA to Maine USA and northward into Canada – Newfoundland.

Here in Lumsden, the story ends at the bay’s shore.  There’s granite here, just like there is in a lot of the rest of the mountain chain…but this is different.  Whereas  lot of the Appalachian granites show stresses from tectonic action, volcanic action, and other forces upon it, the Lumsden granites demonstrate a calm period of geology.  After all, the Iapetus ocean has closed, Avalonia is no longer floating but is attached to Laurentia,   Also, the nearby Dover fault has ceased its movement.  The minerals to create the granite are in place, and with time they form this unique granite.

You are fortunate.  Unlike the granite in “The Smokies” of the southeastern USA, where moss and greenry cover the majority of the granite faces, the ocean waers have kept this clean for your viewing.

So what do you see?  You see granite – composed of pink potassium feldspar, white plagioclase feldspar, grey quartz, and black biotite.  Information needed for Logging requirements -- If there is pressure the crystals tend to be small and well ordered.  If there is no pressure/stress on the granite, crystals tend to grow larger and are not well ordered. 

Now you’ve seen post-tectonic granite – and if you get a chance you should visit the mined granite from a site near here that was used to construct the Alexander Murray Building on the campus of Memorial University, St. John’s campus.

References:

Hild, Martha Hickman., and Stephanie Porter. Geology of Newfoundland: Touring through Time at 48 Scenic Sites. Portugal Cove-St. Philip's, N.L.: Boulder Publications, 2012. Print.