November 22nd, 2017 ~ Vol. 87 No. 47
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Looking Back - John Kinnear
Rocks of Ages, Speak to Me
Looking Back
By Georgialh (Own work)
[CC BY-SA 4.0], via Wikimedia Commons
Blairmorite: The amber colored mineral in pic is analcime, the pale mineral is sanidine and the small black minerals are melanite garnets
Being of Scottish descent I tend to walk about with my head down, looking for loose change and lost things. I think I missed my calling. I should have been a geologist. They’re always casting about, studying what’s at their feet.

They have in fact one of the best jobs there is. To be able to explore and study rocks and landforms with new insight is not necessarily relegated to the professional eye though. It is something any one of us can proceed with if we choose to educate ourselves.

With that thought in mind I’d like to share some of my acquired geological knowledge as I investigate from time to time the mineralogy and formations in and around the area of the Crowsnest Pass and Southern Alberta.

Firstly I have noticed, on occasion, van loads of students parked at the rock bluffs just west of Coleman, a spot some refer to as the government shed corners. They are university students there to get a first hand look at the Crowsnest Formation Volcanics, one of the few exposures of volcanic rock in the Rocky Mountains.

A bit of research reveals that this anomaly is a result of an ancient explosive eruption of solid rock debris, ash and gas from a vent somewhere north and west of Coleman. There the volcanic rock is 425 meters thick and thins in every direction from this spot, which has never been exactly located. (See passherald.ca my archives April 30, 2014 –Geology Rock – Literally – Part two for more on the volcanics)

There are a great variety of rock types in the Crowsnest Volcanics with names like analcime and sanidine. Analcime was once called Blairmorite, after the town of Blairmore but was renamed. That is because geologists now name igneous rocks after the major mineral forming them instead of the locality in which they are found. An interesting side not is that analcime is a zeolite. Zeolites, I have learned, are a classification of minerals that occur both in volcanic and sedimentary rock. They are a extremely stable porous mineral, resistant to heat and doesn't dissolve in water They have all kinds of interesting uses, from water softeners and water filters to cat litter, animal food and as industrial catalysts. They are, as you probably know, a great additive to plant soil.
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Also found within the volcanics are black melanite crystals known as phenocrysts which are basically crystals that have grown in the igneous rock. As a young boy I used to work hard to dig out these mini “black diamonds” from their matrix stone. Most didn't survive the pounding.

Perhaps some of you will recall the so called “gold rush” here in 1988 when a geological technician with the University of Alberta announced he had found gold traces in the volcanics. Everybody got all worked up until it was revealed that alas .074 ounces of gold per ton of rock was way too low for exploitation. Thank God for that. Can you imagine what the bluffs would look like if it had been worth mining?

The welded tuff (consolidated volcanic ash) in the road cut of Iron Ridge: “contains abundant mafic fragments rich in pyrite which are the most likely source of the transported gold anomalies.” Too much geology jargon! Bottom line for me is that the volcanics were a great, strategic place to stand and face that nasty forest fire a few weeks back.

My younger brother Bill is also a rock hound and must be part Italian as he feels bound to collect and build walls and flower beds with any interesting looking specimens he comes across. I spied a couple of unusual pieces carefully worked into his rock works a few years back and queried him as to their origins. He informed me they came from the South Drywood Creek area north of Waterton Park where he has found all manner of fascinating looking mineralogy.

In order to identify and understand how a couple of his treasures came to be I emailed their images to a well known Elk Valley geologist by the name of Bob Morris. He responded with his usual “I love rocks” enthusiasm and provided Bill and I with some amazing insights. The first geometrically patterned image shown in this article is a remarkable almost man-made looking composition he simply described as mud cracks: “the darker colored material is the original mud, which had dried, while the pink material is the infilling mud in the cracks. These are Purcell aged sediments, about 1.2 billion years old.” Wow, that’s really old.
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The Purcell group, I discovered, contains the only other Rocky Mountain volcanic rocks (Purcell lavas), these being formed by gentle lava flows something like what we see going on in Hawaii today. They are principally basalt, a type of rock rich in iron and magnesium and commonly full of holes created by air bubbles in the lava. There are some wonderful exposures up Drywood Creek, west of Shell’s Pecten gas plant. There you can also find bulbous shapes in the basalt known as pillow lava. This phenomenon only occurs in an underwater environment as lava flows into water forming ever-branching pillow lobes.

Next to Bill’s mud crack collection I found a patterned rock that looked for all the world like fossilized flowers. Geologist Morris described them thusly; “This rock is from the Moyie sills, a dark green mafic rock (diorite) with feldspar porphyroblasts (crystals growing in the diorite).” Sounds like Greek to me. He went on to say they typically call them “bird foot porphyry” but that this particular specimen could be called “flower porphyry”. Again he indicated they are part of the Purcells and are over 1 billion years old.

Porphyry shows up in several variations, which carry local names such as flowerstone, snowflake, Chinese writing, and so on and are descriptive of the way the feldspar crystals look in the porphyry, arranged in light-coloured pattern against the dark background rock. The feldspar crystallized as this once-molten rock was slowly cooling.

Incidentally, sills such as the Moyie, are defined as being formed when magma moves upwards through subsurface cracks and then parallel through fractures in bedding. There is a wonderful example of a sill at Waterton Park. It runs through Mt. Blakiston and is a thin black band in this grey limestone mountain. The edges of the sill appear white as the molten rock of the sill cooked the limestone that borders it and turned it to marble.
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There are in fact fossils or should I say fossil traces to be found in the South Drywood area that take us back literally to some of earth’s earliest life forms. They are known as stromatolites and are the fossil deposits from microscopic organisms called cyanobacteria. These bacteria grew in enormous colonies resembling giant cabbage heads. Each colony was like a mat from 10-20 centimeters in diameter and grew and died beside and on top of each other forming giant reef accumulations up to 10 meters high. Cyanobacteria were responsible for creating a major source of earth’s oxygen and allowed higher life forms to evolve. Viewing the Drywood stromatolites literally takes you back to some of life’s most primitive stages.

So there you have just a taste of some of the amazing rock stories that are literally staring us in the face. We are pretty preoccupied about presenting our social history as an attraction these days. Methinks we ought to also consider interpreting our geology in a big way in this amazing place we call the Pass. A series of roadside stops with interpretive signs and perhaps a nice colour brochure with locations that one can follow throughout southern Alberta.
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November 22nd, 2017 ~ Vol. 87 No. 47
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