Much of my research has been focused on Cenozoic sequence stratigraphy of continental basin-fill in southwestern Montana. This approach to the stratigraphy of continental deposits has facilitated correlation of stratigraphic units both within and among the various basins of this area. I recently gave a talk about my work in this area at Montana Tech of the University of Montana. Here’s the You Tube version of my talk:
My field season is in full swing. I recently spent time with students from the Webb Schools in Claremont, CA, during their annual sojourn to southwestern Montana. We prospected a few Tertiary localities, with the students making some good fossil mammal and fossil invertebrate finds. We were also extremely lucky to have a southwest Montana landowner give us a tour of a buffalo jump that is on his land. The following photos are from our various fossil site and buffalo jump field adventures.
The Dog Town Mine Tertiary fossil vertebrate locality is nestled on private property within the southern extent of the Elkhorn Mountains, southwestern Montana. The locality is about 20 miles southwest of Townsend, Montana, where Mesozoic and Paleozoic carbonate, quartzite, and red-colored mudstone, siltstone, and sandstone rocks underlie Eocene (Chadronian) strata. These unconformable Eocene strata contain the Dog Town Mine vertebrate fossil locality.
Earl Douglass (yes, that Earl Douglass of the Dinosaur National Monument fame) first collected at the site on Friday, June 27, 1902 (based on transcriptions from Earl Douglass’ journals done by Alan Tabrum and volunteers from the Carnegie Museum of Natural History). According to his journal, Douglass met a man from Toston, Montana, on horseback and this person told him about the Dog Town Mine, which was located on the divide between the Toston/Townsend and North Boulder Valleys. Douglass was headed to the North Boulder Valley anyways, so he rode to the mine where he found invertebrate fossils (brachiopods and bryozoa) in carbonate rock which was in contact with the ore deposit. A Mr. Allen, who he dined with that evening, told him that more fossils could be found a little ways west of the mine. After dinner Douglass rode a short way west of the mine and found banks along a ravine that looked like Tertiary White River beds. Here he found “Oreodont, Ischyromys, Palaeolagus, Titanotherium, and turtle remains” (June 28, 1902, Douglass Journal entry). This area is the present Dog Town Mine vertebrate fossil locality.
Tertiary strata at the Dog Town Mine are fine-grained, predominantly consisting of siltstone with minor fine-grained sandstone units. The deposits are probably of aeolian origin, originating from areal sediments rich in volcanic ash. These deposits are probably similar lithologically and in mode of origin to those Tertiary White River units found at high elevations within the Laramie Range and Medicine Bow Mountains (Evanoff, E., 1990, Early Oligocene paleovalleys in southern and central Wyoming: Evidence of high local relief on the late Eocene unconformity: Geology, v. 18, p. 443–446; Lloyd and Eberle, 2012, A late Eocene (Chadronian) mammalian fauna from the White River Formation in Kings Canyon, northern Colorado: Rocky Mountain Geology, v. 47, no. 2, p. 113–132).
Vertebrate fossils have been collected at the Dog Town Mine site for various museums since Douglass’ initial collection. The Carnegie Museum of Natural History in Pittsburgh, PA houses a collection from the site as well as the Museum of the Rockies in Bozeman, MT.
Most vertebrate paleontologists probably think of the spectacular dinosaur finds near Jensen, Utah, when the name Earl Douglass is mentioned. Douglass’s discovery of a partial Apatosaurus near Jensen in 1909 did spark the beginning of his long career with finding more dinosaur material in what we now know as Dinosaur National Monument. But Douglass began his quest for fossil vertebrates while he was in southwestern Montana – several years before he was summoned by the Carnegie Museum of Natural History’s director William Jacob Holland to find dinosaurs.
From the spring of 1894 to 1896, Douglass taught at a one-room school in the lower Madison Valley of southwestern Montana. The school house was located in the lower Madison Valley, directly west of the area known as the Madison Bluffs. These bluffs contain strata that range in age from probably as old as Eocene through the late Miocene. The strata are continental units that include alluvial fan to fluvial trunk stream deposits.
During his tenure at the lower Madison Valley school, Douglass spent much of his spare time exploring the Madison Bluffs. At the beginning of his teaching contract in 1894, he had very little knowledge of vertebrate paleontology and of the area geology. He initially considered the Madison Bluff beds as Cretaceous in age. But when he found a “tooth very much like a Protohippus” (Earl Douglass journal entry on May 12, 1894), Douglass knew that the beds were younger in age. As time passed, he began to find a significant quantity of fossil vertebrate mammal material within the bluff’s deposits. Consequently, he immersed himself into reading about comparative anatomy so he could readily identify the fossil material. Douglass eventually used his collected fossil material for his 1899 Master’s thesis at the University of Montana – ostensibly the first Master’s degree awarded by the University.
Douglass kept journals of his time in the lower Madison Valley, and often detailed both the area geology as well as his fossil finds. Alan Tabrum and volunteers from the Carnegie Museum of Natural History have transcribed many of his journal entries from southwestern Montana. I’ve included two portions of journal entries to illustrate his finding of a horse jaw from the bluffs (above diagram) and one of Douglass’s drawings of “Big Round Top” (an area in the bluffs near the one-room school house) as compared to that same area today in a photo that I took about a week ago.
It’s not difficult to understand how Earl Douglass became enthralled with the geology and paleontology of the Madison Bluffs. In addition to the fossil vertebrates, the bluffs contain many other fascinating geological features. Towards the central part of the bluffs (immediately south of the Madison Buffalo Jump State Park), calcic paleosol stacks mark the boundary between most likely Eocene and Miocene strata. The calcic paleosol stacks contain at least two generations of soil profiles (typically minus the A and upper part of the B horizons). Rootlets and burrows are commonly associated with these paleosols.
Volcanic tuffs also occur within the bluff’s strata, which is really handy for those of us who like isotopic age control for southwestern Montana Tertiary deposits. The tuffs could potentially help age constrain the paleosol stacks and sedimentation within the so far non-fossil bearing part of the bluffs. And with the help of the New Mexico Geochronology Lab, a group of us are working on just that aspect of Madison Bluff geology.
Iceberg Lake is situated in the Many Glacier area of Glacier National Park. The hike is about a 10 mile round trip and gains about 1275 feet in elevation. The trail winds through prime grizzly bear habitat, so be sure to hike with a group, make lots of noise, and carry bear spray. When I hiked the trail back in September, many returning hikers told our group about a grizzly sow and two cubs that were roaming around by Iceberg Lake. The bears actually walked by the lake shore while my group and many others were at the lake, but there were no harmful encounters. However – just this past week, in this same general area, a sow grizzly with 2 sub-adult cubs (I’m guessing that this is the same set of bears that walked by my group at Iceberg Lake) was surprised by a lone hiker and the sow grabbed and shook the hiker. The hiker used his bear spray escaped with puncture wounds to his lower leg and a hand. So – some words of caution about about hiking in bear country!
The Iceberg Lake Trail
The trailhead to Iceberg Lake is behind the cabins near the Swiftcurrent Motor Inn. The first part of the hike, about 1/4 mile, gains about 185 feet. After that initial elevation gain, the trail’s elevation gain moderates. Ptarmigan Falls is about 2.5 miles from the trailhead, and a short way above this is a footbridge that crosses Ptarmigan Creek. The rocky area near the footbridge is a great place for a snack break. Another 1/10 mile beyond the footbridge is the Iceberg Lake Trail junction. The Ptarmigan Trail continues towards the right and goes to Ptarmigan Tunnel and Ptarmigan Lake.Take the other trail branch to continue on to Iceberg Lake. A good trail hike summary for the Iceberg Lake Trail is found at the website “Hiking in Glacier”.
The popularity of the trail was clear to me when even on a rainy, sleety, and snowy day,I passed many people on the trail. My group did a leisurely hike, stopping at several places to look at the geology alongside the trail and to do a snack stop by the Ptarmigan Creek footbridge both on the way up and back. It took us about 5 hours for the round trip. That put us back just in time to have a much enjoyed dinner at the Swiftcurrent Motor Inn.
The Iceberg Glacier: Recession from 1940 to the Present
The Iceberg Glacier is shown in the above photo set beginning in 1940 (this is the photo on the left, which is a Hileman photo from the Glacier National Park Archives) and ending with the 9/6/2015 photo on the right, which I took during my hike to Iceberg Lake. In the 1940 photo, the glacier terminus is quite thick and extends into the basin. By 2015, there is not much left of the glacier. Even with a comparison between the center 2008 photo by Lisa McKeon and my 2015 photo, one can see that much more bedrock is exposed. The older photos are also posted on the US Geological Survey’s Repeat Photography Map Tour Website. For those interested in glacial recession within Glacier National Park, the Repeat Photography website is a valuable resource. The Repeat Photography project is summarized on the USGS website –
This project began in 1997 with a search of photo archives. We used many of the high quality historic photographs to select and frame repeated photographs of seventeen different glaciers. Thirteen of those glaciers have shown marked recession and some of the more intensely studied glaciers have proved to be just 1/3 of their estimated maximum size that occurred at the end of the Little Ice Age (circa 1850). In fact, only 26 named glaciers presently exist of the 150 glaciers present in 1850.
Much of the Iceberg Lake Trail winds through the Grinnell Formation, which is a Proterozoic geologic unit within the Belt Supergroup. As Callan Bentley has succintly said of the Belt Supergroup rocks in Glacier National Park:
The rocks exposed firstly from the top down are old sedimentary rocks of the Belt Supergroup. It is called “Belt” after Belt, Montana, and “supergroup” because it is immense. These rocks were deposited in a Mesoproteozoic (1.6-1.2 Ga) sea basin, and show little to no metamorphism despite their age.
I was lucky to be hiking with Jeff Kuhn from Helena, Montana, who has done much work with Belt Supergroup rocks in the Glacier Park to Whitefish Range areas. Jeff stopped us at several locations along the trail to look more closely at features within the Grinnell Formation. In general, the Grinnell Formation consists of sandstone and argillite and is approximately 1740-2590 feet thick. It has a deep brick-red color owing to its contained hematite and because it was deposited in a shallow oxygen-rich environment. Sedimentary features that are consistent with the shallow water depositional interpretation include mudstone rip-up clasts, mudcracks, and ripple marks.
All told, it was a hike well worth doing, even if you are not a geology enthusiast!
The Gravelly Range is located in southwest Montana, about 10 miles southwest of Ennis, Montana. Much of the range is covered by the Beaverhead-Deerlodge National Forest. The Axolotl Lakes Wilderness Study Area, managed by the Bureau of Land Management, is in the northern part of the Gravelly Range.
Our field group was interested in looking at Tertiary rocks, so we headed for the Black Butte – Lion Mountain area, the more south-central part of the range. A cold front had just swept through western Montana a few days prior to my field trip. That storm left some snow up on the range crest – yep, that’s right, snow in July. But it did melt off fast and it left vegetation along the Gravelly Range road (the main road that stretches along much of the top of the range’s extent) extremely lush. So it was a gorgeous drive from the Lyon Bridge crossing on the Madison River up to Lion Mountain and Black Butte. And as Black Butte is the highest peak in the Gravelly Range at 10,542 feet in elevation, it was not difficult to find our destination.
The Tertiary rocks of interest to us were primarily the Tertiary strata exposed on the west side of Lion Mountain. Fossil fauna from these strata have a North American Land Mammal Age of Whitneyan, and are approximately 29 to 32 million years in age. Carnivore, rodent, insectivore, and rabbit are some of the fauna of the fossil assemblage collected here by past workers.
It was a good workout to reach the top of Lion Mountain, but really was well worth the effort. The Tertiary strata had plenty of features to keep a sedimentologist like myself busy. And the views – just spectacular! To top off the trip – it was obvious that someone had been there before us because we found an aluminum ladder stashed is the trees near the top of the Tertiary exposures. None of us availed ourselves of its use, but maybe next time it will come in handy!
Last Thursday (July 10),Yellowstone National Park (YNP) temporarily closed the 3.3 mile-long Firehole Lake Drive, a paved road that traverses some of Lower Geyser Basin. Melting asphalt on a part of the road near the start of the loop drive became a “soupy mess”, according to Dan Hottle, YNP spokesman. Hottle told Live Science that Firehole Lake Drive’s surface reached 160° Fahrenheit (70° Celsius) on Thursday, roughly 30° to 40° F (17° to 22° C) hotter than usual. Hot gases from area thermal activity that were trapped by the asphalt road surface and warm weather combined to cause the road damage.
YNP said that the road would reopen soon and sure enough, by the time I was there on Monday (July 14), the road was driveable. One of the YNP information rangers at Canyon Village told me that the road repairs included road crews removing damaged pavement and applying a mixture of sand and lime to soak up some of the thick bubbly road oil. The road section was then graveled so that the hot gases could better escape a more permeable road surface.
Thermal activity affecting YNP roads and parking areas is not uncommon. During my Monday travels in Yellowstone, another Canyon area YNP ranger told me that about 10 years ago, a new thermal feature melted a small part of the Mud Volcano parking lot. This area is now fenced off, but the rest of the parking lot is still used. YNP spokesman Hottle also informed Live Science that YNP has closed Firehole Lake Drive in the past for repairs due to heat damage, but that these closures are not frequent.
And – just for some perspective on this latest road meltdown: the YNP website home page says “Yellowstone contains approximately one-half of the world’s hydrothermal features. There are over 10,000 hydrothermal features, including over 300 geysers, in the park”. Given the profusion of thermal activity, I’m not surprised that a small section of asphalt melts once in a while. I guess I’m amazed that the YNP can keep park infrastructure maintained such that millions of people can visit the park every year.