Lepidodendron (scale trees): Link to great blog post on these Carboniferous giants

At the time of this writing, the wallpaper of my blog is a snapshot of Lepidodendron bark. Lepidodendron is an extinct genus of Carboniferous age (358.9-298.9 million years ago [Ma]) giant trees (AKA scale trees) common in swamps that eventually were preserved as major coal deposits. Its stylized bark is quite artistically attractive, rather Art Deco in design.

Yesterday I read a great informative blog post on Lepidodendron (http://www.indefenseofplants.com/blog/2018/11/13/the-rise-and-fall-of-the-scale-trees), describing the growth, reproduction, habitat, and demise of these majestic (100 foot/ 30 meter) land plants. The post includes origin of the bark design:

“The name ‘scale tree’ stems from the fossilized remains of their bark, which resembles reptile skin more than it does anything botanical. Fossilized trunk and stem casts are adorned with diamond shaped impressions arranged in rows of ascending spirals. These are not scales, of course, but rather they are leaf scars. In life, scale trees were adorned with long, needle-like leaves, each with a single vein for plumbing. Before they started branching, young trees would have resembled a bushy, green bottle brush.”

That blog post also includes a very sharp photo of Lepidodendron bark, the roots with their own fascinating pattern (stigmaria), and drawings of Lepidodendron species, growth stages, and forest environment.

Below are two photos I took of Lepidodendron for my blog wallpaper. The sample is in the mineralogy collection of the Department of Geology and Environmental Geosciences, Lafayette College, Easton, Pennsylvania. The sample is from the Llewellyn Formation, the younger of two Pennsylvanian-age coal-bearing formations (older= Pottsville Formation) in the eastern Pennsylvania anthracite coalfields. The Pennsylvanian subsystem (323.2-298.9Ma) is the term for the late Carboniferous in North America. The Llewellyn itself was deposited between 308-300 Ma. The Llewellyn Formation also contains the famous St. Clair fossil fern locality. 

For an academic, rather than chatty, description of the St. Clair fossil locality (plus anthracite region mining, stratigraphy, fossils), I recommend two guidebooks: 1) 2015 guidebook to the Southern and Western Anthracite Fields by the Field Conference of Pennsylvania Geologists; Stop 12, page 237, is the St. Clair fossil site; 2) 1992 The Society for Organic Petrology (TSOP) guidebook to The Anthracite Basins of Eastern Pennsylvania (USGS Open File Report #92-568; (https://pubs.usgs.gov/of/1992/0568/report.pdf)); the St. Clair locality is Stop 5, page 65. Both guidebooks include references to Lepidodendron throughout.

Mineral sublimates on steaming culm (coal waste) heaps in NE Pennsylvania: one of Dr. Robert Finkelman’s (USGS) contributions in a career on trace element chemistry in coal

I have been aware of mineral sublimates (materials or minerals formed by direct solid deposition from gas) for a long time from research of friends and colleagues at Dartmouth College on fumarolic sublimates at Izalco volcano in El Salvador. Early collection of minerals there occurred in the 1960’s before and after the 1966 eruption of Izalco*. Vanadates and copper vanadate minerals were found among the sublimates, including several newly identified minerals. For a few of the new sublimates, I, having microscope reflectance measurement experience through coal petrography work, contributed the mineral reflectivity data required for naming new opaque minerals.**

Izalco volcano, El Salvador (this photo and one below from Smithsonian Institution Global Volcanism Program)

On Monday, November 5, 2017, at the annual meeting of the Geological Society of America, I attended the initial biographical presentation by Dr. Harvey Belkin in a session honoring Bob Finkelman (US Geological Survey) for his career in inorganic trace element chemistry of coals and related contributions to the understanding health issues of trace element exposure during mining or home coal use.

Belkin related that one of Finkelman’s early publications (1987; citation below) was on his description of new mineral, downeyite, the first confirmed natural occurrence of selenium oxide. Downeyite is a sublimate formed near a hot gas vent, but not at a volcano: it was found on a burning culm heap in the Northern Anthracite field of Pennsylvania! Piled coal or coal waste can smolder or spontaneously combust. I previously wrote in 2015 about culm heap fires in northeastern Pennsylvania, and evidence that a coal fire in one of the coal bunkers on the Titanic was a possible reason for the speed of passage (easiest way to stop a bunker coal fire is to shovel down and use up coal).

Fell Township, PA, coal waste dump fire, February 2014. (The Scranton Times-Tribune)

Forestville coal dump where downeyite first found. (From PA Geological Survey, Mineral Resource Report 78, 1980)

Downeyite is acicular, colorless and extremely hygroscopic, so, as described in Finkelman and Mrose (1977), must be immediately put in a desiccator upon removal from the hot dry vent environment. Temperatures where downeyite was deposited were 190-230˚C.   Over twenty other minerals found at “anthracite smokers”, as vents of hot gas on culm heaps or over underground mine fires are called (Stracher, 1995), are detailed in Pennsylvania Geologic Survey Mineral Resource Report 78 (citation and download link below), including crystals of elemental selenium. That report indeed does cite the similar occurrence of sublimates at volcanic fumaroles including Izalco!

(From PA Geological Survey, Mineral Resource Report 78, 1980)

Finkelman, “Anthracite smoker” references

Finkelman, R. B., Mrose, M. E., 1977, Downeyite, the first verified natural occurrence of SeO2: American Mineralogist, v. 62, n. 3-4, p. 316-320. (https://pubs.geoscienceworld.org/msa/ammin/article-abstract/62/3-4/316/40741/downeyite-the-first-verified-natural-occurrence-of?redirectedFrom=fulltext)

Finkelman, Robert B., Belkin, Harvey E., and Zheng, Baoshan, 1999, Health impacts of domestic coal use in China: Proceedings of the National Academy of Sciences USA (PNAS), v. 96, n. 7, p. 3427-3431. (http://www.pnas.org/content/96/7/3427)

Lapham, Davis M., Barnes, John H., Downey, Wayne F., Jr., Finkelman, Robert B., 1980, Mineralogy associate with burning anthracite deposits of Eastern Pennsylvania: Mineral Resource Report 78, Pennsylvania Geological Survey, Fourth Series, Harrisburg, 92 pages. (Can download from this page- scroll down to “M 78”: http://www.docs.dcnr.pa.gov/topogeo/publications/pgspub/mineral/index.htm )

Stracher, Glenn, B., 1995, The anthracite smokers of eastern Pennsylvania: P_S2(g) -T stability diagram by TL analysis: Mathematical Geology, v. 7, n. 4, p. 499-511 (https://link.springer.com/article/10.1007/BF02084424)

Izalco references

*Rose, W. I., Stoiber, R. E., 1969, The 1966 eruption of Izalco Volcano, El Salvador: Journal of Geophysical Research, v. 74, n. 12, p. 3119- 3130.

Stoiber, R. E., Rose, W. I., Jr., 1974, Fumarole incrustations at active Central American volcanoes: Geochimica et Cosmochimica Acta, v. 38, p. 495-516.

**Hughes, J. M., Drexler, J. W., Campana, C. F., Malinconico, M. L., 1988, Howardevansite, (Na, K)CuFe2(VO4)3, a new fumarolic sublimate from Izalco Volcano, El Salvador, Descriptive mineralogy and crystal structure: American Mineralogist, v. 73, p. 181-186.

Hughes, J. M., Starkey, S., Malinconico, M. L., and Malinconico, L. L., Jr., 1987, Lyonsite, Cu3Fe4(VO4)O6, a new fumarolic sublimate from Izalco Volcano, El Salvador, Descriptive mineralogy and crystal structure: American Mineralogist, v. 72, p. 1000-1005.

Robinson, P. D., Hughes, J. M., Malinconico, M. L., 1987, Blossite, alpha-Cu 2V2O7, a new fumarolic sublimate from Izalco Volcano, El Salvador, Descriptive mineralogy and crystal structure: American Mineralogist, v. 72, p. 397-400.