Tuesday, August 8, 2017

Axel Heiberg Adventures Part II

                Hello, hello, and welcome to Part II of our Axel Heiberg field adventures! As mentioned last post, we moved campsites about half-way through the trip. The plan was to move from Lost Hammer Spring to South Fjord Diapir. South Fjord is the largest salt dome on the island at a monstrous 5 km diameter! We were to make the move in three trips by helicopter. Oz and I would go first with our personal tents and some other essential gear, the helicopter would return and pick up a net load (literally, in a hanging net) of other gear including the fat bikes, and then on the third trip would bring Mike and Mark with the communal tent and the remaining gear. So Oz and I took off, needing to scout for a place to land that would be safe, accessible, and geologically interesting. But in a 5 km-wide mountain of continually rising and crumbling salt, what could not be interesting?

Until we got there.


That’s, um.  Hmm.

Well, at least we can confirm South Fjord Diapir has rough surfaces.
There is too much snow! We can’t possibly land here! Oz is shocked – it is mid-July and South Fjord Diapir is a winter-wonderland. He said that he visited this site in late June some-years ago, and there was nowhere near this much snow. This has some interesting implications for remote sensing work. Snow and ice can heavily influence radar response – what if South Fjord dome was blanketed in snow when our radar images were taken? I resolve to check Landsat images taken around the dates our radar images have been taken. I have done this since returning – it does look like one of our six images might be affected – perhaps I should mask out the ice and snow and redo the radar zonal statistics extraction!

What do we do? We flew around the dome for a bit, taking pictures while deciding where our backup camp will be. Remember that helicopter time is a valuable resource, so we need to decide quickly. Oz asks if there is a diapir near the end of Strand Fjord. I recall that there is, but I don’t know the distance to it. As we begin to fly over there, I pull out the field laptop that I had in my backpack. I’ll admit, I felt pretty cool flying in a helicopter while measuring distances in ArcGIS to make quick decisions where to land. I determine that Strand Diapir is approximately 6 km from the shoreline, and we deem this close enough to hike to.  We’re off to land in Strand Fjord!

And oh, what a beautiful campsite it was!

Icebergs in the Fjord, a low fog is rolling through. The dark rock unit is an folded igneous sill.
The brown rock is gullied the surface has undergone solifluction.
Strand Fjord, near our campsite.
The sandy banks have compositional layering.
I honestly think this is the most wonderful place I’ve ever camped. We had glaciers and ice bergs and beautiful sharp mountains with intense solifluction. It was beautiful. I did some soil sampling between our camp and the Fjord on one of our off days. 
Again, we saw patches of precipitated salts. Interestingly, these salts tended to be concentrated along the rims of wet/dry sand boundaries. The whole fjord area shows up in the TIR images as having VERY STRONG gypsum/anhydrite signatures, all deriving from the nearby Strand Diapir. Mike, Mark and I went on a hike to visit the northern half of the diapir exposure one day. 

The inland-area of the Fjord appears to be a glacially carved U-shaped valley, so Strand Diapir is split into two main outcrops across the valley. The salts in Strand Diapir are also interacting with some volcanic intrusions, causing some beautiful iron staining.

Behind me is the glacier that carved the U-shaped valley and provides the meltwater for the river.

The brilliant colours are from oxidation reactions between igneous rocks and the diapir.
The igneous rocks provide the metals, the anhydrite provides sulphur.
A reoccurring theme, the outcrops show some exposures of intact rock salt, but the majority of the surface has weathered into the highly vuggy gypsum crust that is characteristic of the Axel Heiberg Island anhydrite diapirs. Part way up the valley wall, the anhydrite is interbedded with what I think is limestone. I haven’t exampled the sample yet, but the dark colour and texture looks like a carbonate and past literature states that limestone is commonly interbedded with the Otto Fjord Formation salts. On a regional scale, the diapir material is stratigraphically overlying the orange stained unit, which I think is a volcanic sill, and has since undergone synclinal folding.

Flying in a helicopter never gets old
Something that I really appreciated this trip was being able to finally investigate the mystery of the radar-dark bright region, mapped as Isachsen Formation (quartz sandstone with some igneous intrusions). As a weather front was rolling in, our helicopter pilot asked if we wanted to make any last quick visits. I gave him the coordinates at the centre of the feature – the peak of a broad mountain range. He looked westward, and observed that that was where the storm was the thickest, and he wouldn’t be able to land there. Nonetheless, we headed that way along the coast, wary of the thick clouds in the distance. The very peaks were shrouded in clouds, but he asked if seeing the sides were enough. Elated to be there, I said yes, and to my delight we made a full perimeter tour around the feature before heading back to the safety of our campsite. Many photos were taken, and the verdict is that these slopes are COVERED in cobble-sized talus that would effectively scatter RADARSAT-2’s 5.6 cm radar beams. Since these are also high elevation peaks, snow and ice is admittedly also a possibility. I’m going to check the Landsat images soon to investigate. Sadly because we couldn’t land I wasn’t able to sample, or get good scaled photos. -sobs-
In addition to the fist-sized rocks everywhere,
take a moment to appreciate that sweet folding.
Travertine terraces from perennial spring from Colour Peak
Finally, one of the highlights of the trip was scaling the 550 m Colour Peak. Colour Peak has been part of the epitome for my thesis, showing that salt diapirs are radar-rough, whereas the materials that erode off of them and reprecipitate elsewhere are radar-smooth. Mark and Mike spent the day sampling the calcite-rich perennial springs effusing from the base of the mountain. The springs are building terraces of black travertine – the type of calcite that precipitates from cold water springs. 1-3 mm cubic halite crystals lined the edges of the streams. Mike founds some really cool crystals in a small cave – the sample he gave me is decorating my coffee table as I write this. The smell of H2S was pungent, and I found myself craving egg salad whilst down there. 
Oz and I, however, journeyed up to climb the massive diapir.  The best exposures of salt textures were at the top, with the flanks being either covered in soil, talus, or completely weathered and crusty outcrop.  The ascent was tough.  The diapir is steep sided covered in poorly sorted colluvium. The skree contains sand to boulder-sized rocks. We also found some palm-sized fragments of clear selenite crystals amongst the soil patches. I think the anhydrite colluvium and gypsum-rich soil is enough to product the spectral signature seen in the ASTER TIR image downslope of Colour Peak without us needed to appeal to the perennial spring. Because much of the slope material was unconsolidated, our feet were prone to slipping down as we moved upwards. I’m very fortunate that Dr. Osinski is an experienced climber, and I was able to follow where his footsteps packed down the debris.  Frequently we would take a step on what seemed to be solid ground, only to have our foot punch through the weathered gypsum crust into a 20 cm deep vug.  
Rough, steep, the return of slightly karst-y topography.

Close to the summit are outcrops of solid anhydrite or gypsum. Unlike at Wolf Diapir, where the solid salt was powdery and friable, here the salt is crystalline.  Erosional processes are carving the solid salt into points like the rillenkarren seen on halite diapirs and in karstic carbonates. The rillenkarren are smooth at the mm scale, but undulate at the cm scale and would appear rough at C and L-Band SAR. 
Rippled rillenkarren textures on crystalline anhydrite sample.

The sharp, solid salt looks beautiful up close.  Of course, nothing compares to the stunning, beautiful view from the summit!


An excellent view across Expedition Fjord,
            and the travertine perennial spring down below


The rocks up here are mostly blocky, partially weathered, and the ground is covered in colluvium. Once again we are able to confirm that salt diapirs are rough on the ground, not just in radar.

Very blocky, rough, and sadly too unstable and dangerous to venture farther.
You can see where Colour Diapir ends, and the adjacent mountain begins
based on surface texture alone. 
  Any discussion of Colour Peak would be incomplete without explaining how it got its name. The colluvium also includes rubble and gravel of angular igneous lithologies, including what is ostensibly dacite and diorite. Some of the volcanic material is oxidizing to form gossans. The gossans are dazzling zones of vivid orange, yellow, and brown alteration. These are found in close association with diapirs on Axel Heiberg Island, including North Agate Fjord and Junction Diapir where basaltic intrusions from the Isachsen Formation are altering to form copper and iron sulphides and secondary copper sulphates (Williamson 2011). The calcium sulphates in the diapir provide the sulphur for these alterations to occur. Remember, we saw this same alteration at Strand Diapir!  We collected some samples of yellow rhombohedral crystals have been taken to the lab to for analysis

The journey home was bittersweet. I’m going to miss this place.

And such concludes my 2017 Axel Heiberg adventure.
Elise xx

Tuesday, August 1, 2017

Axel Heiberg Adventures Part I

Okay, now that I’ve had a week to recover and sort through things, I am delighted and excited to share some of my field experiences with you!  July 5th-20th marked a two-week adventure into the Canadian High Arctic. Our goal: Axel Heiberg Island.  This is why this blog is called, “Arctic Resolution” after all! In a sense, this trip is the epitome of my M.Sc thesis because it gave me the opportunity to “ground-truth” all the observations and analysis I’ve been doing remotely up to now. In essence, I got to see what my radar and spectroscopy images look like in person! It was seriously cool to be able to have that opportunity.

If you need to recap quickly what my thesis is about you can watch me explain it in three minutes:

We are trying to see how radar can be used for remote predictive geological mapping. Remote predictive mapping is not only useful on Earth to save time and money – it is often the only way we are able to learn about the surfaces of other planets and moons. The techniques we are developing are important for planetary science, as Earth is the only planet humans like us can go and check in person. Thus the need for terrestrial analogue studies, which is one of the focuses and strengths of the University of Western Ontario’s Centre for Planetary Science and Exploration. My project is largely grounded in economic geology (salt diapirs -> petroleum + ore deposits -> $$$ = 😊), but I like that this project also has potential analogues for radar mapping and is helping me develop skillsets vital to planetary sciences.

So, what did we see?

This blog post, for the sake of avoiding rambling on and on, will contain summaries of Part I of our field adventures. About half way through our time on Axel Heiberg we moved campsites from Lost Hammer Spring to Strand Fjord, so I will cover our work done around the first campsite.
We found one of our first scientific findings before the Twin Otter even landed. Remember how I was puzzling over the nature of secondary salts? The strong ASTER thermal infrared spectral signatures for gypsum or anhydrite that weren’t confined to salt domes, but rather in gullies and river floodplains? I was wondering if those signatures were the result of:
1. Rubble and gravel of mechanically eroded diapir materials (chunks of salt rock)
            2. Precipitated salt minerals that geochemically dissolved out through water flow

Number 2 is our winner! Just looking out the Twin Otter windows the secondary, precipitated salt is abundant and widespread. 
Salt minerals precipitating in gullies and floodplains
Of course, we confirmed that it is salt minerals on the ground later, and have collected many samples that we will XRD to identify, but it is incredible that we solved one of our biggest field objectives before even landing! These hillslopes and floodplains are predominantly radar-smooth soils, with some colluvial or fluvial pebbles and cobbles.  The salt bearing gullies and stream channels contain larger pebbles, cobbles, and sporadic boulders, but I think these features are too localized to affect the CPR images at the scale of RADARSAT-2 or PALSAR-1 multilooked CPR image resolution. The salt encrustations are <1 mm in thickness on the surfaces. Although boulders and cobbles of salt have mechanically broken off diapiric structures, like the flanks of Wolf Diapir, these likely contribute to the rougher radar signatures seen in the CPR images in association with the diapirs. Later, I also found that there are at least two types of salt minerals precipitating: halite, and what is likely gypsum or anhydrite. I discovered the halite using the classic method all new students learn in Earth Science 101 – licking the samples.
However, what sort of surprised us was the weather-dependence of these surficial salts. When we first arrived, on a beautiful, clear, sunny day, these salts were very sharp in contrast against the landscape. When I walked up the stream at our first campsite, the rocks in the riverbed exposed above water were coated in a white crust. Then the rain and snow came. After three days of snow, almost all of the white encrustations disappeared! There were still white patches on the hillslopes and in gullies, but they weren’t nearly as stark as before. After a day or two of the weather clearing up, the white minerals appeared again, almost as abundant as when we arrived. We think the snow and rain dissolved the salt minerals and they were able to precipitated again from the surface water after the ground was able to start drying.
Salt minerals encrusting some rocks on hillslope

Our first campsite was at Lost Hammer Spring. Lost Hammer Spring is a perennial spring, one of many places on Axel Heiberg Island where brines upwell to surface and deposit large precipitated structures of salt. It is entirely possible that the source of the salt in these fluids derives from the core of the adjacent Wolf Diapir, but this has not been conclusively proven. The salt that makes up Lost Hammer is very sodium rich, implying that the groundwater has interacted with subsurface halite (i.e. table salt) (Battler et al. 2013) but no halite has yet been found at Wolf Diapir. The only diapir at which halite has been found is at Stolz Diapir, which we visited and sampled later in the trip. It is entirely likely that many diapirs on Axel Heiberg Island contain halite in their cores, and that this is simply not exposed at surface. Curiouser and curiouser! Halite was even found precipitating in small patches a few kilometers downriver from Lost Hammer. Like the secondary salts, Lost Hammer Spring exhibited a similar wet/dry cycle. Upon arrival to the field site, the Lost Hammer Spring was a dazzling white, but during the snowfall the spring became greyer and muddier. Either the surface layer of salt was exfoliated, or mud was transported onto the spring during the wet interval. 

Not a snow bank, this is all salt! Lost Hammer Spring (aka Wolf Spring) has accumulated an almost 2 m high vent of halite, calcite, gypsum,
thernardite, and microbilite. The shape of the perennial spring changes seasonally, with periods of partial dissolution and reprecipitation

               Wolf Diapir is characterized by having steep slopes and heavy erosion compared to surrounding rocks from the Isachsen Formation and the Invisible Point Member of the Christopher Formation. The contrast in surface texture is sharp between Wolf Diapir and the other formations. Whereas the adjacent rock formation has regularly distributed gravel in soil, the flanks of the Wolf Diapir are characterized poorly sorted very angular colluvium from sand to block sized particles. Two textures were pervasive amongst all the diapirs we visited this trip - solid, crystalline anhydrite, and weathered, heavily altered vuggy gypsum. 
Wolf Diapir. You can see how the surface of the mountain is far rougher and more gullyied than the surrounding hills.

Close up, you can see how heterogenous and blocky the surface of the diapirs are. Broken fragments range from granule to block sized. It is frequently difficult to determine which blocks are in situ or broken

This weathered, vuggy crust is pervasive across all diapirs we visited.

Other intact anhydrite (or gypsum?) has different lithologies across different diapirs.
At Wolf, the crystalline material was very friable (likely still altered) and highly veined with what might be limestone.

A long gully with 2 m high levees made up of large angular boulders runs down the eastern flank of the structure. We mapped this using a portable LiDAR system.
Dr. Osinksi stands adjacent to the 2 m high colluvial levee flanking a prominent gully coming down Wolf Diapir
              On one of our helicopter traverse days, we could visit Stolz and Whitsunday Bay diapirs are located outside of the WABS region, on the eastern side of the island. Right now we don’t have  RADARSAT-2 or PALSAR-1 coverage over these sites, but I contacted a gentleman at the CSA about using our SOAR-E proposal to get some. For now, we are interested in their chemistry and spectral responses. The top of the diapir is encrusted with a thick, weathered crust of gypsum/anhydrite.  The slopes are steep, with large blocks broken off on the flanks and in the valleys. The topography on Stolz Diapir is karstic, with tall, jaggaed pillars of eroded diapir material.
In some places, the erosion characteristics of Stolz Diapir appeared karstic in nature.
We saw some of this later on at Colour Peak as well.
Like Wolf, Stolz Diapir is very rough and blocky.
                Large vugs within and beneath the altered crust and small dissolution caves run throughout. Two streams run through the structure, converging along the eastern flank. These two streams have different water chemistries and sediment load. One stream has distinctively more halite than the other, and likely runs through Stolz’s halite core. Halite is exposed in outcrop downstream of where the streams converge. Textures within the halite range from white powdery massive structureless to colourless/grey clear crystalline halite with perfect cubic cleavage. Some areas of crystalline halite are green tinged from localized yellow spots which may be endolith colonies.
Dr. Osinksi stands in front of large halite outcrop

In certain places, the halite could be seen growing in framboidal bulbs of small cubes

There are extreme, extensive, thick perennial springs deposits downstream.  They are seriously insane. It looks and feels like walking through snow! These salts have varying textures, colours, banding, and crystal structure. Upstream are alternating light and dark grey salts. Downstream by a pool are pure white, snow-like salts with bladed/rod crystal structures. The strength of anhydrite/gypsum over the spring deposits is notably weaker than the signature over the diapir itself, likely because the spring is predominantly formed from precipitated halite or calcite travertine.

Extensive, massive perennial springs! The white and grey is all salt!
Note the differences in colour and texture between the white and grey salts.
Mark sampled each, and so hopefully he'll be able to tell us what they are.

Salt salt salt!  Everywhere! So that concludes the first part of Arctic updates. Stay tuned for part II within the next fortnight.