Florence Bascom – Rock Star

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Thinking about Florence Bascom immediately brings to mind an image of a pioneering woman geologist making pathways into earth science way before women could even vote in the USA. She was the second woman to earn a PhD in geology in the USA in 1893 and the first female geologist hired by the U.S Geological Survey in 1896. Bascom’s expertise was in crystallography, mineralogy, and petrography where she once again led in research efforts. She published over 40 professional papers and held various professional positions including associate editor of the American Geologist, joined the Bryn Mawr College faculty, where she founded the college‚Äôs geology department, and was the first woman elected to the Council of the Geological Society of America in 1924. A good summary of Bacom’s accomplishments was written by Jill Schneiderman and appeared in GSA Today, July 1997. Just recently, a short video was produced by the Florence Bascom Geoscience Center, which is a US Geological Survey science center recently renamed in honor of Bascom. This video is embedded below:

EOCENE AND OLIGOCENE MAMMALS FROM THE GRAVELLY RANGE OF SOUTHWEST MONTANA

Our first paper on work that several of us are doing in the Gravelly Range, southwestern Montana, was just published in a special issue of Paludicola, Scientific Contributions of the Rochester Institute of Vertebrate Paleontology. This issue contains papers in honor of James Gilbert Honey, a paleontologist and stratigrapher who focused on the Cenozoic, particularly the paleontology/evolution of camels and the Paleocene’s Fort Union Formation geology and paleontology. We’re pleased to have our work included in this volume! You can find our entire paper at:

Rochester Institute of Vertebrate Paleontology – Paludicola:

Donald Lofgren, Debra Hanneman, Jackson Bibbens, Liam Gerken, Frank Hu, Anthony Runkel, Isabella Kong, Andrew Tarakji, Aspen Helgeson, Isabel Gerard, Ruoqi Li, Sihan Li, Zhihan Ji. 2020. Eocene and Oligocene mammals from the Gravelly Range of southwestern Montana. Paludicola 12: 263-297.

Our paper’s abstract is: High elevation outcrops of Tertiary strata in the Gravelly Range of southwest Montana yield late Uintan to Whitneyan vertebrates that comprise five mammalian assemblages; Rapamys Site, Black Butte Low, Teepee Mountain, Black Butte High, and Lion Mountain High. The Rapamys Site and Black Butte Low are late Uintan or early Duchesnean. Two new species are present at the Rapamys Site (the carnivore Lycophocyon tabrumi and the rodent Pareumys muffleri). Small mammalian assemblages from Teepee Mountain and Black Butte High are late Duchesnean-early Chadronian and Chadronian, respectively. The most diverse assemblage is from Lion Mountain High, which is correlative with Whitneyan faunas from Wyoming, Nebraska, and South Dakota. The Whitneyan age of the Lion Mountain High assemblage is further age constrained by an underlying tuff with a weighted mean 40Ar/39Ar age of 31.7 +- 0.02 Ma and an overlying basalt flow with a K/Ar age of 30.8 +- 0.7 Ma. Paleogeographic range extensions into Montana for Lion Mountain High taxa include Diceratherium tridactylum and Oxetocyon cuspidatus. The taxonomic composition of the combined Rapamys Site/Black Butte Low mammalian assemblage is most similar to those from southern California, rather than geographically closer assemblages found in Wyoming and Utah. Comparison of undescribed middle Eocene mammalian assemblages from southwest Montana to those from southern California will further elucidate the middle Eocene Montana-California paleobiogeographic affinity.

Our geology paper on this area is soon to follow….

Devil’s Slide and A Jumping Fox

Devil’s Slide, a part of Cinnabar Mountain, is located about 3 miles north of Yellowstone National Park’s northern boundary and about 7 miles northwest of Gardiner, Montana. The “slide” or red streak on Cinnabar Mountain is developed in Triassic red beds.

Whenever I drive to Yellowstone National Park’s northern gate, I pass by the Devil’s Slide. It seems that the slide is my gate keeper to the park, and it is always fun to see it in all our different seasons. And once again, during a chance conversation in the park, I was asked about the geology of Devil’s Slide. Because of that conversation, I thought that I’d spend some time blogging about the slide’s geology.

Devil’s Slide is a part of Cinnabar Mountain, which contains steeply-dipping to overturned Paleozoic and Mesozoic strata. Cinnabar Mountain is fault-bounded on its north side by the Gardiner Fault, a north to northeast dipping reverse fault zone. At Cinnabar Mountain’s north end, the Gardiner Fault juxtaposes Archean crystalline rock (now partly masked by Tertiary intrusive rocks and Quaternary glacial sediments as shown on geologic map snapshot below) on the fault’s northern, up-thrown side against Paleozoic strata on its down-thrown, southern side. The Paleozoic-Mesozoic strata in Cinnabar Mountain are contorted because of drag associated with the Gardiner Fault.

Cinnabar Mountain and Devil’s Slide area as a snapshot from the Geologic Map of the Gardiner 30’x60′ Quadrangle, South-Central Montana (Berg and others, 1999, Montana Bureau of Mines and Geology Open-File Report 387). Map symbols on Cinnabar Mountain are: Mm = Mississippian Madison Group, PMs = Permian-Mississippian rocks, Psh = Permian Shedhorn Sandstone, JTrs = Jurassic-Triassic rocks, Kk = Lower Cretaceous Kootenai Formation, Kmfr = Upper and Lower Cretaceous Mowry Shale through Fall River Sandstone.

According to Marius Campbell and others (1915, p. 92), “Cinnabar Mountain was named in the early days, when the bright-red streak that marks it from top to bottom was supposed to be due to the mineral cinnabar, a red ore of mercury.” (From: Guidebook of the Western United States: Part A – The Northern Pacific Route, With a Side Trip to Yellowstone Park, U.S. Geological Survey Bulletin 611). We now know that the bright red streak is not cinnabar (a brick-red form of mercury sulfide), but the area of red in Devil’s Slide is actually a set of Triassic age red beds that mark widespread continental deposition and limited marine incursions throughout the Rocky Mountain region. The red beds in this case get their color from the oxidation of iron-rich minerals contained within the rocks.

And now for the jumping fox and its association to my Devil’s Slide discussion – as I said previously in this blog, the conversation that I had with a fellow-park goer a few days ago brought about my blog on Devil’s Slide. My conversation about the slide happened while I was watching a fox hunt rodents in YNP’s Round Prairie, a gorgeous meadow near Pebble Creek Campground in the park’s northeastern area. The female fox hunted for hours that morning, and several photographers and myself were enthralled with her hunt. The light snowfall of the night before accentuated the bushy fall coat of the fox and gave the hunting scene great color contrast. Here are are few photos from the hunt:

Round Prairie fox with her gorgeous fall-winter coat.
Round Prairie fox on the hunt.
Round Prairie fox on her hunting jump.
Round Prairie fox finishing her hunting jump.

Fall Fieldwork in the Greater Yellowstone Area

Sheepeater Cliff area, Yellowstone National Park. This area is named in honor of the Shoshones who lived in this area, The name specifically comes from their use the big horn sheep – hence the name “sheepeater”. Note the columnar basalt in the cliff area which has an age of about 0.5 million years.

Doing geology field work in the greater Yellowstone area during the fall is always an adventure. This is the time that animals and birds are on the move, so it’s a good opportunity to have interesting chance encounters. In my quest to understand the Eocene thermal springs of the Gravelly Range in southwestern Montana, I’ve spent time in the Yellowstone area hiking around thermal areas. The Artists Paint Pots, located a few miles southwest of the Norris Geyser Basin, appear to be a likely analogy for the Gravelly Range thermal strata. Of particular interest is the red staining that occurs in many meters of Gravelly Range thermal deposit strata. The red stained rocks are ubiquitous in the Red Hill and Middle Springs areas.

Red Hill in the Gravelly Range, southwestern Montana, contains many meters of red-stained, thermally generated Eocene strata.
The Middle Springs area in the Gravelly Range also contains several meters of Eocene red-stained thermally-generated rocks. It’s extremely easy to confuse these rocks with the underlying red-colored Triassic Woodside Formation strata.
Red-stained thermal deposits at Artist Paint Pots.
Blood Geyser thermal pools at Artist Paint Pots, Yellowstone National Park.

The Artist Paint Pots, especially the Blood Geyser, are well known for red-colored rocks that are produced by iron oxides precipitating out of the thermal waters and staining the surrounding rocks.

As I said earlier in this blog, doing fall field work in the greater Yellowstone area usually means exciting chance encounters with various animals and birds. Some encounters are a bit more exhilarating than others, but I did manage to photo-document some in between finishing up field work for the season:

Young grizzly loading up with food (only caraway roots and mice!) in the Tom Miner Basin, Montana.

Bull moose eating on Cottonwood trees near Ennis, Montana.

Immature bald eagle near the Jefferson River, Montana.
Redtail Hawk on irrigation pipe, near Sheridan, Montana.
Trumpeter swan family resting at – ironically, Swan Lake Flats, Yellowstone National Park.
Great Horned owl giving me the evil eye…
Sandhill cranes in-flight near the Ruby Mountains, southwestern Montana.

Working On High Elevation Tertiary Strata, Southwestern Montana

Lion Mountain, south-central Gravelly Range in southwestern Montana, has about 300 m of Tertiary strata capped by basalt that is about 31 million years in age.

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.

Channel complex near top of Lion Mountain comprised of Paleozoic rock clasts.
Basal surge deposit about 25 m from top of Lion Mountain. Embedded basalt clasts, sand waves, and plane parallel beds characterize this deposit.
Basalt bombs in channel near Lion Mountain crest have paleomag drill holes – a clear sign that someone else has made this climb!
A ladder stashed in the uppermost tree-area on the mountain which is left over from past paleontology expeditions.
The orange baked zone that underlies basalt is evident in this photo. Also note the channel lenses that outcrop randomly across the Tertiary stratal expanse.
About 5 km northwest of Lion Mountain sits the basalt plug of Black Butte. Previous reported isotopic ages range from 23-25 million years, but our preliminary data show an age of about 30 million years for this volcanic feature.
The most pleasant part of the hike in the Lion Mountain area is in the glaciated meadow that lies at the base of the mountain. We’re a little late for the wild flower bloom, but it still is a gorgeous area!