Sunday, October 26, 2014

Jane Austen and wildfire?

Interesting stream of thought after returning from the 2014 annual meeting of the Geological Society of America: was relaxing at home late Thursday afternoon and caught the end of one of my favorite movies, the rather esoteric chick flick, The Jane Austen Book Club. Set in California and filmed in southern California, their last book club meeting, discussing Persuasion, was at a rocky beach, typical of many along the Pacific US coast. Besides the intensely deep blue color of Pacific water, these beaches descending from the rugged coastline are different from the wide sandy beaches I have lived near most of my life on the US Atlantic passive-margin coastal plain from New York south to Florida.

I was reminded of beaches like this in Oregon, with Haystack Hill, which was one my husband and I stopped at while driving down Pacific coastal highways from Seattle to Los Angeles in 2012.
The Oregon beach, like several others we saw, was pebbly, like the movie's 'Persuasion' beach; this Oregon one was so consistent in pebble size and color, I used it as my iPhone home screen wallpaper for a while. But thinking about that beach, led me mentally to the coastal redwood state and national parks we visited farther south in northern California during that trip.
I was fascinated by the not infrequent fire scarring on the redwoods, here from Jedediah Smith Redwoods State Park ( I was intrigued enough to take several burn scar photos). Redwoods can survive ground fires, even with obvious burning, although decay associated with scars can be a problem in recovery.
A number of trees have these fire cavities. A good explanation of these can be found at http://www.redwood.forestthreats.org/cavities.htm. Once fire starts burning the more resistant sapwood inside, fire temperature and intensity can increase and seriously threaten survival of the tree. The Coast Redwood Ecology and Management website, a consortium of private institutions and government agencies, also has case studies of individual modern fires among redwoods (http://www.redwood.forestthreats.org/canoe.htm)

Giant redwoods, a coastal tree, are a different species from the giant sequoia, which are also only found in California but at higher inland elevations. A number of studies of fire history and sequoia have been done by Thomas Swetnam (including "Fire history and climate change in giant sequoia groves" Science, v. 262, 1993), who has collaborated with, among others, Andrew Scott, mentioned in previous blogs.

In coals and organic-bearing sediments, examples of the incomplete burning of wood during wildfires millions of years ago can also be found. Under the microscope, particles are occasionally seen that show the transition from very burned to less charred wood. Fusinite, a highly reflecting inertinite maceral (see first blog entry) frequently showing the skeletal structure of charred wood or charcoal, may visibly transition to semi-fusinite, a less-reflecting maceral, but possibly still having a porous skeletal structure. Rarely, vitrinite, the maceral of uncombusted wood, may even be present showing a complete sequence from charred to unaffected.


Tuesday, October 21, 2014

Wildfire and extinction II, GSA 2014

Just heard a fantastic talk at GSA annual meeting by Victoria Hudspith, a student of Cynthia Belcher (see previous blog entry), on "Latest Permian chars may derive from wildfires, not coal combustion" (https://gsa.confex.com/gsa/2014AM/webprogram/Paper248275.html). This research is also found in the just published article of the same title (Geology, October 2014, v. 42, p. 879-882, first published on August 28, 2014, doi:10.1130/G35920.1), the volume of which I am told is available in the GSA booth area in the Exhibits hall.

Hudspith and co-authors present evidence that vesiculated chars and other fly-ash-like particles found in end-Permian high-latitude sediments can be produced from burning of peatlands and forests. Fly ash textures are normally associated with the burning of coal. (Fly ash is the uncombusted or partially-combusted residue that 'flies' up the chimney during coal combustion; theoretically, it should all be mineral matter, but if organic combustion is incomplete, there will be carbonaceous particles also.) Earlier authors hypothesized that the presence of vesiculated chars meant explosive burning of Siberian trap intruded coals, releasing methane that contributed to the largest mass extinction in Earth history. Hudspith's research indicates that burning of coal is not required to produce vesiculated chars.

I pondered myself the presence of vesiculated chars among the inertinite maceral population in Triassic Richmond basin and Jurassic Newark basin sediments that I point-counted for my dissertation particulate organic sedimentation study of cyclic rift-basin lacustrine sediments (PhD 2002; study not yet published except in meeting abstracts: my bad). If vesiculated char implied burning coal, how could that be present in basins in which 1) there were no coal beds (Newark), 2) burial, coalification, and exhumation would not have yet happened to syn-rift peat swamps (Richmond), or 3) there was no major geologic ignition process for possibly exhumed Late Paleozoic coals 100 km to the west? The results of Hudspith's experiments burning various uncoalified terrestrial plants and plant debris, and petrographically examining the products, resolves that conundrum.

Monday, October 20, 2014

Paleo-wildfires and extinctions at GSA 2014


How did I miss seeing that talk in the program?! At the 2014 Geological Society of America meeting Sunday, I made a point to go to Gerta Keller’s talk on her research on the end-Cretaceous extinction (she has long advocated that Deccan trap volcanism is the cause, not Chicxulub impact), but luckily heard the last half of Cynthia Belcher’s preceding talk “Cause or consequence? Wildfires at the Triassic-Jurassic and Cretaceous-Paleogene boundaries” (https://gsa.confex.com/gsa/2014AM/webprogram/Paper246260.html).  I was actually more interested in Belcher’s talk due my background in coal petrology, doctoral research on Triassic-Jurassic eastern US rift basins, and USGS Mendenhall post-doc research (2006-08) on the Chesapeake Bay impact crater.

For the end-Triassic, Belcher concluded, based on amounts of fossil charcoal, that subsequent increase in wildfire was a consequence of the change in vegetation after the extinction (http://www.nature.com/ngeo/journal/v3/n6/abs/ngeo871.html). Her study was in Greenland. My dissertation research on changes within and among orbitally-driven 20,000-year lacustrine sedimentary cycles in the earliest Jurassic of the Newark basin (New Jersey) showed differences in amount of fusinite (fossil charcoal) between cycles that could be attributed to the cyclic climate variability during that time period. Thinking of change across the Tr-J boundary, these Jurassic lake cycle differences could possibly mask any notable extinction-related fossil charcoal variation. I did not sample Triassic sediments since most of the immediately underlying Newark Triassic is red, therefore organically barren, and is overmature; regrettably, southern US late Mesozoic basins like the Richmond and Taylorsville basin are missing the Jurassic.

For the K/Pg (end-Cretaceous) boundary, Belcher called any wildfire due to the meteor impact a “one-and-out” event (I think that is the term she used) that did not promote environmental change. To lay my cards on the table, I have long been a fan of Andrew Scott, one of Belcher’s doctorate advisers, and his coal petrographic studies of fossil charcoal in coals across the K/Pg boundary that show NO evidence of a giant impact-related wildfire or increase in wildfire activity. Mostly due to Scott’s research, I have not been convinced, despite impact modeling studies, that the atmosphere caught on fire during Chicxulub impactor entry enough to burn vegetation or fry dinosaurs. Suggestions that the worldwide presence of soot indicates a global K/Pg impact-related wildfire is negated by modern studies that show soot from large wildfires can circle the globe in less than a month.

Various organic compounds, like polycyclic aromatic hydrocarbons (PAH), are also geochemical indicators of combustion and can be used to identify paleo-wildfire events. Geochemistry is a powerful tool, but being a petrologist, I see microscopy and geochemistry as partners in research. Sometimes one really has to look at the rock to understand the geochemical context. Both have trade-offs: geochemistry can be quick but expensive, while traditional light microscopy is economical but time-consuming.

Sunday, October 19, 2014

Coal Harbour neighborhood, Vancouver city

The 2014 Geological Society of America annual meeting is going on right now in Vancouver, BC. Just to the west of the convention center is the Coal Harbour neighborhood (some maps spell it Harbor; there is also a town of the same name on Vancouver Island). Working in coal petrology myself, I was curious about its name.

Did, of course, check Wikipedia, plus found a great local site with historic photos: http://www.insidevancouver.ca/2013/05/15/604-neighbourhoods-coal-harbour/.
Coal was found on the bluffs overlooking the harbor (along what is now West Hastings Street) in 1859 according to the Inside Vancouver website (1862 according to Wiki). However, both sources say it was of poor quality and never exploited. The associated clay was porcelain-quality, but also never produced. Being at the terminus of the Canadian Pacific Railway, the area was an industrial center. Now it boasts a marina, condominiums, shops and restaurants.

Speaking of the Canadian Pacific Railway, the grand historic old CPR hotel is on Burrard Street, just a block south of the Hyatt. Like all grandly elegant former CPR hotels, it is now run by Fairmont hotels (Fairmont Hotel Vancouver). I have been through the lobbies of historic CPR hotels in Banff, Quebec City, Lake Louise, and Victoria (in latter also had high tea and dinner while in town for an organic petrology meeting in 2007). I will definitely have to walk through the Vancouver lobby and see if I can swing afternoon tea or drink at the bar!

Friday, October 17, 2014

Rhode Island anthracites...NEIGC...Father Jim Skehan

Usually when we think of anthracite coal in the United States, we think of the Late Paleozoic anthracite fields of eastern Pennsylvania. However, the Narragansett basin in Rhode Island/Massachusetts contains similar age (Pennsylvanian period, 323-299 million years ago) anthracite- to meta-anthracite rank coals. These coal-bearing fluvial sediments were deposited after the Devonian Acadian orogeny whose imprint dominates the metamorphic terrane of New England. Columbus Day weekend, I attended the 106th New England Intercollegiate Geological Conference (NEIGC), an annual regional field conference headquartered this year at Wellesley College, Massachusetts, and went on two trips to the coastal portion of the Narragansett basin.

Anthracite coal is defined as fixed carbon 92-98%, vitrinite reflectance 2.5-6%; meta-anthracite has vitrinite reflectance >6%. It is a higher rank, with more carbon and less hydrogen and oxygen than bituminous coal. Metamorphically, anthracite rank is correlated with the anchizone, prehnite-pumpellyite grade or subgreenschist metamorphism. The metamorphic grade in the Narragansett basin increases from anthracite-coal-rank in the north to sillimanite-grade in the southwest, and this metamorphic gradient can be seen across the basin primarily within one unit, the Rhode Island Formation. This year's NEIGC Rhode Island field trips were in the southern garnet-to-staurolite metamorphic zones where carbon occurs as mineral graphite, but there have been earlier field trips to the lower-grade RI anthracite fields.

Following dramatic increases in oil prices in the early 1970's, old US domestic fossil fuel resources were re-evaluated, including the RI anthracites. These had been exploited earlier in the 20th century, but due to high ash (mineral content including quartz veining), discontinuous seams, and incipient graphitization, the RI anthracites and meta-anthracites never were as profitable as the PA anthracites. Their utilization, besides as a fuel, included lightweight aggregate and foundry graphite. Intense deformation and contact metamorphism from granitic plutons are among processes related to the Late Paleozoic Alleghanian orogeny that compromised the economic value of the RI anthracites. The Narragansett basin was perched on peri-Gondwanan terranes outboard of the craton whereas the PA anthracites were inboard on the craton and, therefore, more "sheltered", so deformation in RI during the Late Paleozoic collision of North American and Africa was, analogously, more like a head-on crash rather than the Labrador-Retriever-skidding-on-the-front-hall-rug folding/thrusting of the PA Valley and Ridge province.

Authors of post-1970 RI anthracite studies include Dan Murray, URI, a leader of my two trips last weekend, and Father James Skehan, SJ. NEIGC this year was dedicated to Father Jim, founder of the Boston College geology department, professor emeritus, and one of the eminent New England geologists of the latter 20th century. He celebrated his 90th birthday in 2013, and currently resides in a Jesuit retirement community (http://www.bc.edu/offices/pubaf/news/2012_jan-mar/jimskehan.html). This is the 50th anniversary of the 1964 NEIGC in Chestnut Hill, MA, organized by Father Jim. The first field trip on the first NEIGC I attended (1981, Kingston, RI) was led by Father Jim and Nick Rast (University of Kentucky) to the pre-Cambrian rocks of Newport. Although brought up Catholic, this was the first time I had seen a priest without a Roman collar, but dressed in flannel, field vest, and Wellington boots. Mud is the great equalizer among geologists, the student, the professor, rookie or expert, equally wet or grubby doing field work or at outcrops during field trips or conferences like NEIGC. (I have often thought, having graduated as a history major back in the day, that having to get dirty makes geology departments more relaxed, promoting discussion and collegiality.) And, through NEIGC and professional society events, I am privileged to have become a professional acquaintance of Father Jim.

Tuesday, October 14, 2014

Coal petrology?


“Black is black”: although this sentiment of heartache from the 1966 Los Bravos song implies some sort of absolutism, when it comes to coal, coal utilization byproducts, or coaly sedimentary organic matter, there is more variety than what casually meets the naked eye. I was once challenged by an organic chemist on microscopically discriminating between coal and bottom ash (residue after burning coal in a furnace or boiler), but contrary to the Rolling Stones’ lyrics “No colors any more . . . I wanna see it painted, painted black . . . black as coal”, there is a diversity in morphology, texture, luster or reflectivity, and gray-scale when particulate organic-bearing rocks or products are examined under the microscope. Even in hand-specimen, lumps of coal can reveal details of their stratigraphy and back-story. On a 1992 field trip to an open-pit anthracite mine in Pennsylvania, the dull sooty surface layer of a small slab of coal I picked up displayed large flat pieces of porous charcoal, relics of an ancient forest fire, compared to the millimeter-scale glassy black layers of mostly vitrinite, formed from gelified ancient wood: stacked chapters in the geohistory of a paleo-swamp.

I use coal petrology to solve geologic problems. (Non-geologists: "Petrology" means the study of rocks- "petro" comes from the Greek for rock; "petroleum" means oil from rock; "petrified" means turned into rock; the name "Peter" has the same root.) So what does a coal petrologist do? Four weeks ago, I did the renewal microscope exercise for my coal petrologist accreditation through the International Committee on Coal and Organic Petrology (ICCP), and the two parts of this exercise illustrate primary techniques of coal petrology.

(First as technical background, coal petrologists use reflected light microscopy under oil immersion: instead of light passing through translucent materials on a glass slide from underneath, the light is bounced off the highly-polished surface of a piece of coal. Metallurgists and geologists who study opaque economic minerals like gold, copper sulfides, steel, etc. also use reflected light microscopy. The immersion oil, with a specified index of refraction, forms a meniscus between the specimen and the microscope objective lens; it increases the contrast among the various coal macerals, much like that tasty field geologist practice of licking a rock.)

So the first segment of the accreditation exercise is maceral analysis, counting and calculating percentages of the three major maceral groups. Maceral? Besides being a frequent word in the national spelling bee, a maceral is a microscopically recognizable constituent of organic matter in coal, first defined by Marie Stopes in 1935 (http://igs.indiana.edu/Coal/Macerals.cfm). SAT analogy: maceral is to coal as mineral is to rock. The three general groups of macerals are vitrinite (woody organic matter), inertinite (~fossil charcoal and is non-reactive in some industrial processes), and liptinite (waxy plant parts like spores, leaf cuticles, resin, algae). In addition, there is mineral matter in coal, aka ash, the part of the whole coal that will not combust. The relative proportion of macerals in a coal (or organic-rich sedimentary rock) can give an indication of ancient climate conditions (lots of fossil charcoal= conditions ripe for forest fires), groundwater conditions in the coal swamp (soggier vs. drier), distance of a point in a lake or ocean from the shore line and land plant input. Industrially, the maceral proportions help predict the behavior of the coal in processes such as coke making in the steel industry.

The second part of the accreditation exercise is vitrinite reflectance. With increasing temperature the reflectance or reflectivity of vitrinite (maceral derived from woody plant matter) increases due to chemical and physical changes. The percent of incident light reflected from vitrinite is measured, like maceral counts, on a polished piece of coal or vitrinite-bearing sedimentary rock using oil-immersion reflected light microscopy, plus associated photomultiplier or digital measurement equipment and calibration to reflectance standards. (Standardized procedures are described by ASTM and ISO.) Vitrinite reflectance is a diagenetic to very-low-grade metamorphic indicator and is one of the markers for rank (i.e. lignite, high- and low-volatile bituminous, anthracite) in coals and degree of petroleum generation in organic-bearing sedimentary rocks. It is useful data for basin or regional thermal history studies, resource characterization, and industrial utilization. Vitrinite reflectance can be related to the maximum temperature experienced by a rock or coal through modeling algorithms that combine burial temperature history and vitrinite reaction kinetics.

This blog will cover a broad array of topics under the big umbrella of carbonaceous geologic or earth materials. As the blog summary in my Introduction sidebar describes, the organic carbon here will be mostly particulate and/or combustible, not dissolved in fresh or marine waters or bound in the carbonate of limestone or skeletons. Sometimes the connection of a blogpost to geologic carbon may be tenuous, and the carbonaceous “Bacon number” may be high!

(Addendum: My June 20, 2015, blogpost lists relevant online bibliography and photomicrograph atlases, coal and organic petrology-related scientific societies and books.)