7 August 2014
I’ve got some student work to share with you today. Like yesterday’s guest post on deltas growing into Canadian Rockies glacial lakes, my Rockies students are turning in their final projects – digital products that aim to serve the world at large by introducing key places in the Canadian Rockies to a wider audience. The idea is to go from outcrop-scale observations to the larger context, to tell the interpretive story of the Canadian Rockies through the context of key places we visited on the trip.
Marissa D. found the Frank Slide to be an impressive place. She made this Tumblr to delineate its geology.
Zack S. made this Google Earth tour of the Crypt Lake trail. Zack offers the following instructions:
- Save the KMZ file to your computer.
- Open Google Earth.
- Double-click the KMZ file to place the tour folder into Google Earth.
- Please hide all “layers” except for the “borders and labels” layer.
- Please hide all other “places” besides the tour folder.
- Click the “play tour” button below the “places” box.
- Pause the automated movement of the tour at each stop.
- Click the alphabetized marker at each stop (each stop has only one associated marker).
- When you are done with a particular marker, close the pop-up box and un-pause the tour.
- I have provided an online playlist of ambient music to add to the tour as well. I highly recommend using it, as it adds to the atmosphere of the tour. Just click here, http://8tracks.com/anon-1089753594/tour-ambiance, and hit the “play” button.
Jeffrey R. also focused on Crypt Lake. He made a website to explain it.
Sean B. was entranced by the outcrop of Bison Creek Formation with distinctive tension gashes. So he made this Prezi to explain it.
Davis M. also picked the Bison Creek Formation outcrop, but for him it was one of three examples of places where we observed tension gashes on the trip. Check out his tension-gash-themed website to explore them.
Soo L. looked at the evidence of last year’s flooding in Canmore, with some bonus time up on the lakes west of the Icefields Parkway. She made a Tumblr, too – so start at the bottom.
There will be more to come in the coming days (as feedback and edits are incorporated), but consider this a little taste of some of the most prime-time-ready projects.
6 August 2014
[guest post by Maddy Rushing, George Mason University, one of Callan's students this year in Regional Field Geology of the Canadian Rockies]
The Canadian Rockies are well known for their superb glaciated landscapes and active ice fields. Not so well known, are the glaciated landforms that lay beneath the surface. Observing the rock record and numerous outcrops throughout these mountains, one can find a map of the past.
First, we will take a look at modern day glacial deltas to be seen in the Canadian Rockies today. Peyto Lake in Banff National Park, Alberta. The image below from Google Maps depicts Peyto Lake as a glacial-fed lake having its primary inflow from Peyto Creek which drains water from the Caldron Lake and Peyto Glacier and finally flows north, into the Mistaya River.
The delta of focus is located at the southern most end of Peyto Lake. This delta is of ice-contact variety for its deposition occurs at the margin of the glacier. The sediment being deposited at this delta accumulates from various locations regarding the glacier. Most of the sediment travels through subglacial rivers or streams, however the glacier itself transports some sediment on its own.
Here is a closer look at the delta: (zoomed in from Google Maps)
The GigaPan below (by Callan) shows the delta from a profile view. Looking closely, you can see the dendritic drainage system typical of deltas.
And as you can see, the location is quite beautiful.
Outcrops can provide a great visual representation for how these deltas form and show what they look like so that geologists may be able to find them in other locations to better understand the geological changes that a certain area has undergone. The following outcrop was found in Kootenay National Park, right outside of Radium Hot Springs.
These are sediments we interpreted as having been deposited by a prograding glaciolacustrine delta. The delta likely was formed during one of the more recent of numerous glaciation periods in the Canadian Rockies; perhaps the Illinoian? Considering the outcrop has not been dated and assuming it was in fact formed during the Illinoian Glaciation, it is reasonable to infer that the approximate age of this outcrop is 130,000 years. This delta is a coarse grained lacustrine delta as opposed to a marine delta with gentle slopes and fine grained sediment such as the Mississippi Delta. These coarse grained deltas are known as Gilbert Deltas (named after Grove Karl Gilbert of USGS) and are characteristic of rivers or streams coming into contact with freshwater lakes. Gilbert Deltas have three stratigraphic components: a topset, foreset, and a bottomset. The picture below shows the orientation of these beds.
Topset beds are deposited by streams or distributaries, typically consisting of coarse- grained sediment that leaves a horizontal layer across the top of a delta. Foreset beds are found below the topset beds and are deposited by sediment that was carried down the end of a delta into deeper waters than the topset beds and thus are a bit more fine-grained as well. Foreset beds characteristically have a slight angle that suggests the direction of flow and delta growth. Finally, the horizontal bottomset beds underlie the foreset beds and are deposited in deeper, calmer waters leaving the finest delta sediment. The sequence of these beds provide an exquisite deltaic cross-section such as this one on Kootenay Highway.
The image below is a better look at this outcrop:
Unfortunately, there was not ample enough time to spend at this outcrop to get images of better quality or ones that incorporate scale (here’s a link to GoogleMaps StreetView of the outcrop: Kootenay Hwy Glacial Delta Outcrop). Regardless, the stratigraphic relationship is clearly recognizable. An annotated image of a zoomed in portion of this outcrop is depicted above, showing the relationship between the three stratigraphic components.
Observing this outcrop, allows us to interpret this area as a pervious glaciolacustrine delta similar to the modern day glaciolacustrine delta seen at Peyto Lake. Making these observations is important within the geological field because it allows us to compare and contrast the type(s) of environment(s) a particular area has confronted, ultimately to better understand the geological changes of that area. The Canadian Rockies is a great place to go to make these observations as well as enjoy the area on it’s own.
1 August 2014
My student Mercer Parker shot this one over to me the other day:
Those are the slim strata of the Rome Formation (a.k.a. Shady*), strongly deformed in the region adjacent to the Max Meadows (“M&M”?) Fault.
* Will the real slim Shady please stand up?
24 July 2014
I’ve had a great three weeks in the Canadian Rockies, but now I’m heading out.
It’s been an honor and a privilege to teach in these fine mountains, among amazing rocks with talented colleagues and thoughtful students, and I’ve really enjoyed the past week of GigaPanning with my colleague Aaron Barth.
Yesterday, Aaron and I saw these bear tracks in the mud next to a creek where we were GigaPanning. The Canadian Rockies have imprinted themselves on me in a similar way. I’m leaving with more than 50 new GigaPans and an uncountable number of positive memories.
12 July 2014
Greetings from the field… here’s a scene I contemplated yesterday…
4 July 2014
A final guest Friday fold from reader Howard Allen, who I’m pleased to be meeting up with in Banff late next week…
Howard writes the following in describing this lovely scene:
Warspite Anticline, Peter Lougheed Provincial Park, Alberta. Photo is a telephoto shot (hence the strong blue alpine haze–the colour cast is an accurate rendition of the original daylight Kodachrome slide), looking southwest at an angle to regional strike. The peak at top centre is Mount Joffre, the highest peak in the area. The dark peak in centre, on the left limb of the anticline, is Mount Warspite. Photo was taken in 1998 from the summit of the north end of “Kent Ridge” (= the western ridge of Mount Inflexible) at 50.7706, -115.2210. The peaks in the middle ground, with nearly vertical bedding, between Mt. Warspite and Mt. Joffre, belong to Mount Lyautey. This view shows the opposite (north) side of Lyautey, and the Lyautey Syncline. The syncline axis is hidden in this view by the peak of Mount Warspite, but you can see it on the next range south, forming a snow-covered col on the left side of the photo, about 1/3 the way down from the top.
Thanks, Howard! See you next week!
To everyone else:
- Happy Friday!
- Happy American Independence Day!
- Happy Final Friday Fold For Now… I’ll resume the blogging in August after I get back from travels out in these same mountains.
3 July 2014
What are these Border to Beltway students up to?…
Clearly, they are all immersed in their field notebooks, sketching away. This was in March, in west Texas.
There must be something worth drawing at this road cut…
A clue can be seen on the wall of rock behind them. There, you can find features such as this:
Those are outsized clasts of gray limestone in fine-grained tan limestone. …An interesting mixture! How could such a mixing occur? Perhaps the outcrop has some more clues to share, something to inform our thinking before we rendered an interpretation…
So we asked the students to sketch out what they observed, at several scales, before we began to discuss it.
The clast-rich unit was overlain by a graded bed of limestone “breccia”…
Which fined upward…
And got finer and finer, but still part of one massive bed…
And then that massive bed was overlain by alternating layers of shaly limestone and ~2″ thick limestone beds:
We interpreted this ensemble, which was in the deep water basin seaward of the forereef of the Permian reef complex which sees expression in the Guadalupe Mountains a few miles to the north, as a massive submarine landslide, bringing big blocks of reef material avalanching down into the deep, where the big chunks were included in unlithified carbonate mud.
Thus, something as innocent looking as this…
…can imply a massive, chaotic, underwater catastrophe in the ancient past.
This is why I love geology – acquiring the ability to read the clues allows one to deduce fascinating stories about the otherwise inaccessible past.
Spotted in the yard this morning:
One fungus (yellow, cracked like a breadcrust) being consumed by another (whitish, hairy wisps).
2 July 2014
Here’s a breccia that Dan Doctor and I found in a tabular zone within the Helderberg Group (Devonian limestones) in one of the massive new roadcuts along Corridor H.
Is it a fault breccia or a sedimentary breccia? The breccia was bedding parallel, which suggests it could be just another bed, but it’s so darn coarse and angular (unlike the rest of the Helderberg) that we were skeptical. Indeed, pulling out a chunk (the sample you see above) and examining the bottom (the view you see below), brought additional evidence into consideration:
Those are slickensides! They are most prominent in the vein calcite patch on the left side. Zoom into this macro GigaPan by my student Robin Rohrback and check it out.
It’s a fault breccia. The fault happens to be parallel to bedding (because bedding planes are planes of weakness in sedimentary rocks), but it’s not actually a bed itself.
27 June 2014
Some folds this week from coastal exposures in western Boothbay Harbor, Maine, where I’m on vacation for one more day…
Acadian metamorphics (schist, gneiss), with injected granite pegmatite that has also been folded (and boudinaged):