1,500 to 170 Million Years Ago
The Rocky Mountains to the west were once horizontal layers of marine sediments (sand, silt, mud, animal and plant matter) lying at the bottom of the ocean just off the shore of the barely-recognizable North American continent. This sediment got here due to the runoff from rivers flowing across the continental plate and the reefs that grew and died on the ocean floor. The immense weight of all of the sediments compressed the oceanic plate and actually deflected it downward, which in turn resulted in the collection of more sediments (Mussieux & Nelson, 1998).
Steno's Principles
In 1667, Nicolaus Steno, a Danish scientist, proposed two rules when it came to dating the layers in a rock formation.
1.) The principle of original horizontality: This principle states that sediments are deposited under the influence of gravity in nearly horizontal layers. If the layers are not horizontal, or are bent, this means that the rock was either faulted or tilted due to tectonic forces.
2.) The principle of superposition: This principle states that a deposited layer is younger than the layer below it, but older than the layer above it. A younger layer cannot be deposited below an older layer. Therefore strata can be layered from the oldest rock at the bottom to the youngest rock at the top.
170 to 55 Million Years Ago
(Grotzinger, Jordan, Press, & Siever, 2006)
The Rocky Mountains started to grow when the Pacific Plate collided with the North American plate and components of the Pacific Plate were "scraped" off and welded to the North American plate (Mussieux & Nelson, 1998). As the Pacific Plate was forced underneath North America, the North American plate was compressed and scrunched. As a result of the plate being deflected upward for mountain building, the region which is present-day Alberta was bent downward. The ocean flooded in from the present-day arctic and Texas/Louisiana. A shallow, warm sea now covered North America (Mussieux & Nelson, 1998).
The Inland Sea covers North America all the way from North to South.
65 Million Years Ago
Later a further continental collision resulted in the Interior Plains rising up and the inland sea disappeared (Mussieux & Nelson, 1998). When the mountain building was finally slowed, the mountains towered high into the sky and continent had been reduced 200 km in length. Millions of years of reef building and the cycle of life and death created a thick layer which now form the oil and gas reservoirs of Alberta (Mussieux & Nelson, 1998).
The Inland Sea was on its way out by the end of the Cretaceous
What are We Seeing Here?
As previously discussed, the layers in a strata are deposited over long periods of time. The type of rock layers deposited can also vary over time resulting in physically and visually distinct layers.
What happened here was that the strata of the future Siffleur Canyon was deposited horizontally 350-360 million years ago and then the tectonic forces through mountain building tipped the whole strata (Mussieux & Nelson, 1998). From GZ you can see the mountain to the north that has layers tilted the exact same direction.
There is a layer of Banff Formation between two very hard, very erosion resistant layers of limestone. At some point there was a weak spot in a section of limestone that allowed a stream to gain a foothold and wear its way through. Once the water got through the layer of limestone, it had access to the weaker Banff Formation (shale, marlstone, chert, and sandstone) the water kept carving away at this weaker layer much faster than the surrounding limestone (Mussieux & Nelson, 1998). As a result, this river through the canyon is almost dead straight since it follows the path of least resistance, the Banff Formation.
To Log This Earthcache
To log this Earthcache you must send me the answers to the following questions below to prove your visit to the site through the geocaching.com messenger. Visitors who log and do not send me an answer within a reasonable amount of time will have their log deleted.
1.) What is the strike of the canyon
2.) What is the dip of the canyon
3.) Is water in the bottom of the canyon clear, milky, or some other color? Why is this so?
4.) Do the surrounding mountains and rocks match the strike and dip of the canyon?
5.) Do Steno's two principles apply here and how so?
References
Musieux, R., & Nelson, M. (1998). A Traveller's Guide to Geological Wonders in Alberta. Edmonton, AB: Provincial Museum of Alberta.
Grotzinger J., Jordan, T., Press, F., & Siever, R. (2006). Understanding Earth. New York, NY: W.H. Freeman and Company.
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