Working on Tertiary strata in the Gravelly Range, southwestern Montana, is sometime daunting to do. The Lion Mountain Tertiary section shown in the photo to the right is one of those places that makes for a grueling day or several days of field work. The Tertiary section unconformably overlies various Paleozoic units, such as Mississippian Madison Group carbonates, Pennsylvanian-Permian quartzite, and Triassic carbonates and red mudstone. And the ascent from these pre-Tertiary rocks to the top of the Tertiary section is worth it – for both vertebrate paleontology and sedimentary features. Current work status in the project that I’m working on with the Raymond M. Alf Museum, Claremont, CA, is that the section contains vertebrates ranging in age from about 40 million years to about 31 million years in age. A tuff unit near the top of the section that we collected has an Ar/Ar age of 31.4+- 0.7 million years. The capping basalt (the dark zone on the top of Lion Mountain) has a reported K-Ar age of 30.8 +- 0.7 million years. Sedimentary features include massive aeolian units and some channeling near the top of the section. A basal surge deposit occurs about 25 m below the capping basalt, signalling the initial pulse of extensive basaltic volcanism in the Lion Mountain locale. Several photos of my most recent Lion Mountain climb illustrate the section’s features and are shown below.
Amy Atwater is the Paleontology Collections Manager/Registrar at the Museum of the Rockies in Bozeman, Montana – and more importantly, is an amazing scientist. Her discussion of archaeology/paleontology, deep time, stratigraphy, etc., with the “cowboys of science” in episode #5 of their Life In Ruins podcast series (embedded below) is a must listen! More information about Amy and her work is also available on the Archaeology Podcast Network’s website: Episode#5
The Lake Myvatn area, located in northeast Iceland, has an amazing, and truly beautiful, volcanic landscape. This area lies within Iceland’s North Volcanic Zone, which is a part of the Mid-Atlantic Ridge – the spreading rift between the Eurasian and North American plates that slices through Iceland. Lake Myvatn is the fourth largest lake in Iceland, and is quite shallow, with the deepest part being only about 4 meters. This area is also renown for its wetlands and birdlife, with the lake’s numerous bays and its outlet to the north-flowing river Laxa being host to a multitude of birds.
My favorite experience at Lake Myvatn was riding an Icelandic horse around the pseudocraters in the Skútustaðagígar area of Lake Myvatn (southwestern part of the lake). Pseudocraters are unusual in that they are rootless volcanic cones that formed in this area about 2300 years ago when basaltic lava flowed over the water-logged lake sediment, resulting in the cones being built from steam exploding through the lava. So -not only did I want to see pseudocraters, but I also wanted to lean how to tolt because this is a natural gait exclusive to Icelandic horses. According to Riding-Iceland.com,
“the Tölt is a natural, fluid gait of the Icelandic Horse, during which at least one foot always touches the ground. Foals often tölt in pastures at an early age. The tölt is an extraordinarily smooth four-beat gait, which allows the rider an almost bounce-free ride, even at 32 kmh (20 mph). “
I contacted Safari Horse Rental (located just off the main road in the Skútustaðagígar area) and set up a two hour ride. Gilli was my guide, and he took me through mostly private land to both look at pseudocraters and to teach me how to tolt. It did take me awhile to understand how to let my horse know it was time to break into the tolting gait, but when we both got it figured out, wow! what a way to see pseudocraters! I’d urge anyone who loves to ride horses to try this!
Again – I’ll highly recommend that the best way to view Lake Myvatn’s pseudocraters is by tolting on an Icelandic horse!
While I am in awe of Iceland’s mid-Atlantic ridge system volcanics and its glacial geology, I still like to see sediments and fossils. So – as I was doing my pre-trip research into Icelandic geology, I found that there are about 500 meters of Pliocene strata exposed on the west coast of the Tjornes Peninsula in northern Iceland. Needless to say, the Tjornes Peninsula became part of my travels in Iceland.
The best way to access the Tjornes sequence is to go to the Tungulending Guesthouse, which is about 12 km north of Husavik. The turnoff for the guesthouse is just off Highway 85 and signed as shown by the photo below. Of course we missed it and kept driving a few km up the main road before we stopped to ask a local farmer. The farmer knew exactly where we wanted to go and sent us back down the road to Tungulending. Once we saw the Tungulending main sign and then passed the guesthouse gate, we knew we were headed in the right direction.
The Tjornes Pliocene strata contain both marine and continental deposits. The strata sit on the Kaldakvisl lavas while the Hoskuldsvik lavas cap the sedimentary sequence. The Tjornes Formation records a coastal environment that includes estuary-swamp, shallow marine-beach, and swamp-fluvial settings that existed in between the basaltic lava events (Simonarsson and Eriksson, 2008). These strata include a diverse mollusc fauna and recently the oldest marine vertebrate fossil in Iceland, a partial skull from a fossil whale (a large right whale), was also found within the Tjornes Formation (Field and others, 2017). Jonathon Hall, a Doctoral Researcher in the School of Geography, Earth and Environmental Sciences, University of Birmingham – UK, has put together a great leaflet on the geology of the Tjornes Peninsula, and the leaflet content can be found here: Geology of the Tjornes Peninsula.
Even if you are enthralled with Iceland’s volcanic and glacial geology, it is still well worth a look at the Tjornes Formation and a visit to the Tungulending Guesthouse for good conversation and food!
I did a snorkel tour of the Silfra fissure with Dive.is while I was in Iceland a couple weeks ago. That is a very impressive way to view part of the mid-Atlantic ridge system! Here’s what Dive.is says about Silfra that makes it so unique:
“Silfra is a fissure between the North American and Eurasian tectonic plates in Thingvellir National Park. The rift was formed in 1789 by the earthquakes accompanying the divergent movement of the two tectonic plates . The diving and snorkeling site at Silfra is right where the two continents meet and drift apart about 2 cm per year. Silfra is the only place in the world where you can dive or snorkel directly in a crack between two tectonic plates. The earthquakes of 1789 opened up several fissures in the Thingvellir area, but the Silfra fissure cut into the underground spring filled with glacial meltwater from the nearby Langjökull glacier.”
There are 6 people to a group for the snorkel tour, with each group accompanied by a guide from Dive.is. Jake was our guide and he was great! The tour is simply snorkeling through basalt and more basalt, but with the water clarity, the colors are beautiful. There is also one place where you can stretch across the fissure and basically touch both plates.
I also took video while I was snorkeling, so am inserting a clip from the first part of the snorkel tour at the end of this blog. The video clip includes the time when we all get geared up, have our gear checked, and then flipper-walk down the entrance ramp, into the water. We all have to do a flip over to our back once we’re in the water, just to make sure we can maneuver once we’re in the water. The clip continues on as we snorkel through the first several minutes of exploring the fissure. At the end of the snorkel tour, we hike back to where the Dive.is vans/equipment are. After taking off our gear – which getting off the dry suit is somewhat of a challenge – we have hot chocolate and cookies. Because the weather was so nice, it was a pleasurable experience to stand around and feast. But – we were told that in the wintertime the guides take the hot water that is suppose to be used for the hot chocolate and it pour down the snorkelers’ necks so the dry suits can be pulled off. Glad I opted for late May to do this!
Montana’s autumn is my favorite time of the year to do field work. Daytime temperatures are usually cool enough to encourage one to keep moving and the lighting is simply gorgeous. It is also one of the best times to visit areas in and around Yellowstone National Park (YNP) because most of the tourists have gone home. So no huge bear traffic jams or jostling for parking spots at the better known thermal spots in YNP and surrounding environs – it’s just a wonderfully introspective time for field forays. What follows are several photos that chronicle some of my fall wanderings in the greater Yellowstone area, both in terms of wildlife and geology.
Some of my favorite sightings in YNP are bison at any time of the year. But the autumn snows bring on the bison’s technique of using its head to clear snow away from any vegetative food source. The result of their snow-clearing activity is a snow-masked face.
And where the snow hasn’t stacked up much, the YNP bison calmly graze and occasionally congregate on a ridge line to watch what remains of the YNP visitor traffic.
Geological features in YNP take on new dimensions with the golden low and slanting light of autumn. I’ve spent much time re-photographing geologic features at all scales that seem to glow in this season’s light.
The fall staging areas of sandhill cranes in southwestern Montana are mesmerizing. Staging areas are those locations where cranes annually congregate during late September into October, spend several days foraging through fields for food, and eventually continue on their migration southward from Montana to Colorado and the southwestern U.S.. The staging area that I usually go to is near Dillon, Montana, where hundreds of cranes can be viewed.
As I said initially, it’s hard to surpass a Montana/YNP autumn!
Over 100 wildlands fires are burning in the U.S., with most of them being in the western U.S. The California fires are exceedingly destructive, with Cal Fire officials calling this the new normal for the now extended and catastrophic fire seasons that we are experiencing. In the midst of all this, there’s a particularly good Ted talk on megafires done by Paul Hessburg at the TEDx event in Bend, Oregon, 2017. The video is well worth viewing:
Geologic field work is always fun, but especially so when it turns up something unexpected. Working on Eocene to Recent geology and vertebrate paleontology in the Gravelly Range, southwestern Montana promised to be enthralling because the volcanics, sedimentary units, and vertebrate fossils are at elevations of about 9,000 feet. But to come across extensive, unmapped calcareous spring deposits of probable Eocene age is topping off research efforts.
At this point, I’ll just say that our field team is still at work on the Tertiary spring deposits. We’ve found numerous leaf impressions including those of ginkgo, palm, metasequoia, Fagopsis (extinct member of Beech family), and alder – just to name a few. We’ve shown the plant assemblage collected to date to several paleobotanists, and, at least for age, their take is that the assemblage is probably latest Eocene in age, and bears many similarities to Florissant, Colorado fossil plant assemblages.
The spring deposits in the Gravelly Range are extensive, covering an area roughly 2 miles in length with deposits up to 120 feet in thickness. The springs are best characterized as travertine, although the spring systems’ edges contain clastic fluvial units and both the springs’ edges and pools have features such as plant impressions, root systems, and small travertine balls.
Because the Gravelly Range is so close to Yellowstone National Park, it is extremely interesting to compare its Eocene spring deposits to hydrothermal units at both the currently active Mammoth Hot Springs (which probably began its activity about 7,700 years ago), and to the fossil travertine found just north of Gardiner, Montana, that formed about 19.500 to 38,700 years ago (Fouke and Murphy, 2016: The Art of Yellowstone Science: Mammoth Hot Springs as a Window on the Universe).
The Gardiner travertine is fairly well exposed because it has been extensively quarried for several decades. Of interest for comparison are numerous plant impressions that occur within microterracettes. Fouke and Murphy (2016) suggest that these may be impressions of sage brush. A photo of the quarried wall with the plant impressions is shown below.
Other features in the Gardiner travertine, now partly covered by graffiti, include a quarry wall that shows terracettes and microterracettes that are outlined by darker lines within the travertine. These features are probably indicative of a proximal slope facies.
Jumping forward in time to the extensive spring deposits of Mammoth Hot Springs (just within the northeast park boundary of Yellowstone National Park), is mind boggling. As in any comparison with rocks as old as Eocene to active deposition, one realizes how much detail is lost over time. But it is still worthwhile to try to compare spring features, so I’ll show a few photos of the Mammoth Hot Springs that may match up with various features of the fossil springs.
Suffice it to say, that the upcoming field season should be a good one, with more work to be done on the Gravelly Range spring deposits. And – it’s always fun to get a trip in to Yellowstone!
It’s time for our yearly update talk on field work and data compilation for the Tertiary geology and paleontology of the central Gravelly Range project in southwestern Montana. The Madison Ranger District in Ennis, Montana (5 Forest Service Road) will be hosting my talk on Monday, April 2nd at 10am in the Madison Ranger District conference room. We have a project permit from the US Forest Service because our project area lies within the Madison Ranger District – and the USFS District people have been really helpful with our project logistics. Thus, this is the perfect way to let them know what we did this past field season and how the whole project is coming together. The Madison District just sent their public announcement for the talk:
Dr. Hanneman and Dr. Don Lofgren, PhD (Director, Raymond M. Alf Museum of Paleontology, Claremont, CA 91711) and their team have been executing a multiyear study in the Gravelly Range near Black Butte resulting in many interesting paleontological findings right here in our own back yard. Please join Dr. Hanneman and the Madison Ranger District for an update on this project and what they hope to unearth this year!
It’s a very intriguing project on high-elevation, mainly Eocene-Oligocene Tertiary geology and paleontology (mostly vertebrate and floral). So – anyone with an interest in this and who is in the geographic area, is welcome at the talk!
An op-ed in today’s New York Times, How We Know It Was Climate Change, is well worth reading. The author of the op-ed, N.S. Diffenbaugh, lays out the rationale for a link between climate change and extreme weather events. Diffenbaugh’s op-ed is based on a journal article written by himself and others that was published in the Proceedings of the National Academy of Sciences (PNAS – 3/17), Quantifying the influence of global warming on unprecedented extreme climate events.
Both the op-ed and the PNAS article are essential reads for the new year.