LATE EOCENE CHRONOSTRATIGRAPHY, DEPOSITIONAL ENVIRONMENT, AND PALEOSOL-TRACE FOSSIL ASSOCIATIONS, PIPESTONE SPRINGS, SOUTHWEST MONTANA

I just received notice from the Geological Society of America (GSA) that our abstract is now accepted for the GSA 2020 annual meeting. I was very much looking forward to going to Montreal for the meeting, but like much else, it will now be virtual. Our presentation is scheduled for the session titled “D23. Recent Advances in Understanding Environmental Changes and Their Effects on Sedimentation”, which will be on Monday, 26, October 2020, beginning at 1:30 PM. And I say our abstract, because my co-authors are: Steve Hasiotis (Department of Geology, University of Kansas, Lawrence, Kansas), Don Lofgren (Raymond M. Alf Museum of Paleontology, Claremont, California,) and Bill McIntosh (New Mexico Bureau of Mines and Mineral Resources, Socorro, New Mexico). We’re excited to get this abstract out in the public domain as it details the first single-crystal sanidine 40Ar/39Ar ages for the well-known vertebrate locality of Pipestone Springs in southwestern Montana. We also have other significant findings, such as newly-identified trace fossils and the presence of loessites in the Pipestone Springs section. Our paper on these findings is nearing completion, soon to be submitted to a peer-reviewed journal. Anyways, here’s our Pipestone Springs abstract:

Sanidine 40Ar/39Ar ages of lapilli tuffs and the mammalian fauna of Pipestone Springs Main Pocket provide a high-resolution chronostratigraphy of late Eocene strata in the Pipestone Springs area of southwestern Montana. Two felsic lapilli tuffs, with weighted-mean 40Ar/39Ar single crystal sanidine ages of 37.50 + 0.02 Ma and 36.00 + 0.20 Ma, occur within the basal to mid-section of the 55 m of exposed Pipestone Springs strata, whereas the upper 15 m yields a diverse and abundant assemblage of mostly small-bodied middle Chadronian mammals. The older lapilli tuff is an airfall tuff whereas the younger lapilli tuff exhibits some aeolian reworking. Loessites intercalated with paleosols dominate Pipestone Springs deposits. Andic paleosols are developed on the lapilli tuffs. Buried B cambic to weakly developed argillic horizons characterize the remaining paleosols that are also classified as andic because there is a significant component of volcanic grains mixed with identifiable non-volcanic grains in their parent material. All paleosols are extensively bioturbated, containing newly identified trace fossils likely constructed by dung beetles (Coleoptera) based on comparisons to modern and ancient traces attributed to this group. Close examination shows that the tracemakers built these structures in a helical pattern from the inside and outside by adding pelletized sediment from the base upward, such that the architectural elements resemble features of Rebuffoichnus, FeoichnusEatonichnus, and Coprinisphaera. The preserved forms likely reflect a continuum of state of completion by adults and usage by larvae and pupae, and final preservation in the paleosols. The new isotopic age constraints significantly increase the age range of the Pipestone Springs strata to include early Chadronian deposits in addition to its well-known middle Chadronian vertebrate assemblage. Recognition of loessites comprising these strata is also a new interpretation, making these deposits some of the oldest known aeolian Eocene strata in the Great Plains–Rocky Mountains region.

Pipestone Springs Main Pocket vertebrate locality (middle Chadronian).

Cuban Geology – An Updated Resource List

Vinales Valley in Cuba was designated a UNESCO World Heritage Site in 1999.

Within the last few weeks I’ve had several requests for available resources on Cuban geology. The requests, of course, have come from individuals outside of the U.S.A. Guess that they sense opportunities for working with and understanding Cuba’s geology that we are backing away from. In any case, I’ve sent the requests on to Manuel Iturralde-Vinet, the person who has worked and published an immense amount of information regarding Cuba’s geology. Manuel has now sent me back an updated list of resources and said:

You can advertise to all your friends and colleagues that a large
percentage of the geology, geography, paleontology, geophysics and
mining papers are free to be visited at
http://www.redciencia.cu/geobiblio/inicioEN.html

Other resources that are available include: http://www.redciencia.cu/cdorigen/arca/iturra.html

Field Trip Guides to Cuban Geology: 2001, IV Cuban Geological and Mining Congress: K-T Boundary of Western Cuba

— 2001, IV Cuban Geological and Mining Congress: Former Caribbean Plate Boundary, Camaguey, central Cuba

Compendio de Geología de Cuba y del Caribe. Segunda Edición 2012:
http://www.editorialcitmatel.cu/producto.php?producto=128

Videos de Viajes: http://www.youtube.com/user/IturraldeVinent2011#grid/user/A43949937C36E7BC

Videos de Geología y Naturaleza: http://www.youtube.com/user/IturraldeVinent2011#grid/user/DE8FDB5CE5960C19

Geological Society of America: The Geological Society’s (GSA) annual meeting in Denver, 2016, hosted a special session on the Geologic Evolution of Cuba. A link to session abstracts is: GSA Geologic Evolution of Cuba. The GSA Today October 2016 issue also highlighted Cuba Geology with the article “The geology of Cuba: A brief overview and synthesisauthored by Manuel Iturralde-Vinet and others.

Earth Magazine: Travels in Geology: Journeying Through Cuba’s Geology and Culture.

 

Glacial Geology Field Tripping in the Northern Yellowstone Area

Living near Yellowstone National Park has its advantages – and the best of these is being easily able to go on field trips to the Park area. A field trip opportunity came up last week when the Rocky Mountain section of the Geological Society of America came to Bozeman, Montana, for its annual meeting. One of the meeting field trips was the “Glacial and Quaternary geology of the northern Yellowstone area, Montana and Wyoming”. The trip was led by Ken Pierce, Joe Licciardi, Teresa Krause, and Cathy Whitlock. Having spent much time in the Yellowstone area, I was ecstatic about going along to find out about recent geological work. I won’t elaborate on the specifics of the trip, but for those interested in more than the photos posted below, the field trip guide is available in The Geological Society of America Field Guide 37, 2014, p. 189-203. It’s worth a read!

A few of the stops on the trip:

Paradise Valley – Chico Moraines and Chico Outwash (45.3402 N, 110.6967 W)

Chico moraine boulders have an average cosmogenic age of 16.1 +- 1.7 10BE ka.

 

A succession of outwash terraces border the melt-water channel which is now the Chico Hot Springs road.

North Gardiner Area – Giant Ripples (45.0551 N, 110.7659 W)

Giant ripples occur on a mid-channel bar a few miles north of Gardiner, Montana.

Cosmogenic ages on the flood deposit boulders of the giant ripples average 13.4 +- 1.2 10Be ka.

Northern Yellowstone NP – Blacktail Deer Plateau (44.9577 N, 110.5652 W)

The Blacktail Plateau is capped by moraines of Deckard Flats age - 14.2 +- 10Be ka.

The Blacktail Plateau is capped by moraines of Deckard Flats age – 14.2 +- 10Be ka.

Northern Yellowstone NP – Phantom Lake Ice-Marginal Channel (44.9554 N, 110.5289 W)

The ice-marginal channel that Phantom Lake lies in was cut into volcanic bedrock during the Pinedale glacial recession. The lake is dammed on its down-stream end by a post-glacial age alluvial fan.

The ice-marginal channel that Phantom Lake lies in was cut into volcanic bedrock during the Pinedale glacial recession. The lake is dammed on its down-stream end by a post-glacial age alluvial fan.

Northern Yellowstone NP – Junction Butte Moraines (44.9128 N, 110.3854 W)

The Junction Butte moraines have an age date of 15.2 +-1.3 10Be ka. Large  boulders of Precambrian crystalline rocks and several ponds typify the morainal surface.

The Junction Butte moraines have an age date of 15.2 +-1.3 10Be ka. Large boulders of Precambrian crystalline rocks and several ponds typify the morainal surface.