Monday, December 15, 2014

A side of bacon...or algae?

In mid-November here in Easton, Pennsylvania, before winter temperatures descended on us with a thud and preceding the turkey frenzy of Thanksgiving, Bacon Fest was held in our center square. (Through spring into early fall, our Farmer's Market, the nation's oldest continuous open-air market (~1752) is held in the square.) I did not go to Bacon Fest this year, but last year my dog and I enjoyed some delicious bacony macaroni and cheese, looked at the little piggies before the piglet races, and drooled over beautiful imaginative bacon-ingredient cupcakes in the baking competition. I did not realize until a few years ago, that some people are crazy for bacon!

Last entry, I mentioned the petroleum potential of amorphous organic marine snow. Sometimes I have used frying bacon as an analogy, for non-scientists, to describe petroleum generation from kerogen (insoluble organic matter residue in rocks): heat up the fatty bacon and liquid grease is produced, some greasy gas, and eventually one ends up with more grease and a burnt up solid, if the cook has not been paying attention. Same in a rock: oil-prone organic matter, such as lipid-rich plankton. algae, marine snow, spores/pollen, will, as temperature slowly increases with deep burial over geologic time, eventually produce oil as they are cooked in the "petroleum kitchen" (AKA hydrocarbon kitchen, oil kitchen: yes, they really do use that term in the oil business). A solid refractory high-carbon-content residue usually remains.

You may wonder, why we just don't industrially fry up algae to produce oil? There has actually been research into that, both fossil algae and fresh algae. Thirty-to-forty years ago, after the 1973 Arab Oil Embargo, there was a peak of research and pilot plants, in the United States, for producing liquid fuels from Western US oil shale, a rock rich in algal kerogen. The research looked at the feasibility of heating oil shale to produce and extract oil that had not yet been geologically cooked out of the fossil algae. The Green River Shale in Wyoming, Utah, Colorado, was a prime target rock. A positive outcome of this research was improved understanding of the chemical reaction kinetics of petroleum generation; kinetic algorithms by Lawrence Livermore National Lab scientists are the standard today in petroleum generation modeling (A nice review of proposed oil shale extraction methods, research, and economics can be found at http://www.ceri-mines.org/documents/A14b-AlanBurnhampaper.pdf). A major environmental, and political, issue, however, is that some methods can require a lot of water, which would monopolize excessive amounts of upstream Colorado River water to the detriment of downstream agricultural and drinking water customers in the SW US and Mexico.

Considering that farming algae on a large scale would be a possible transportation biofuels source, ExxonMobil, in 2009, supported ongoing research on growing algae on a large (numbers) scale and then extracting the lipids. (http://www.bloomberg.com/news/2013-05-21/exxon-refocusing-algae-biofuels-program-after-100-million-spend.html).  Advantages of the algae-farm technique is that it is renewable on the short term, may consume carbon dioxide, and does not include mining or mine waste disposal, like the Synfuels oil shale project would. However, as the Bloomberg article says, existing strains of algae were found not to produce an economically viable amount of product. Research by Exxon's partner will now focus on potential genetic modifications that may in a couple decades be successful. The business reports bemoan the project as a failure since $100 million (out of the original $600 million budgeted) has been spent without success. But actually . . . it is a success of the scientific method! There was a hypothesis, experiments were designed to test it. Even though the hypothesis was not proven true, there is valuable knowledge gained, and a new path proposed. It did cost money, but scientific inquiry does cost money, and advancement of basic science and technology can not happen without it.

Thursday, November 20, 2014

It's winter! Marine snow?

Six feet in 24 hours: that was the unfortunate high rate of snowfall in Buffalo, New York, on the shore of Lake Erie on Tuesday, 11/18/2014. Even for a region used to very snowy winters, that was excessive and paralyzing.

Six meters in a million years. That is the accumulation rate for "marine snow". Marine snow, according to the National Oceanic and Atmospheric Administration (NOAA) informational webpage on the subject (http://oceanservice.noaa.gov/facts/marinesnow.html), is the shower of organic matter falling from upper marine waters to the ocean bottom. The "snow" consists of fluffy agglomerations of generally structureless decaying organic matter, the microbes feasting on it, clay particles, dust, tiny plankton shell pieces. The "flakes" may get to several centimeters. The organic matter may be consumed or depleted before it settles on the bottom, or may accumulate and be a food source at the seafloor. The NOAA page says that 3/4 of the seafloor may be covered with an accumulated organic ooze from marine snow deposition.
One-centimeter aquatic snow aggregate, Lake Constance, Germany.
Microbes consume organic matter in marine snow and release carbon dioxide, so the velocity of settling affects exposure time and has a direct impact on the amount of CO2 released back to the ocean. The amount and type of particulates in the snow affect the density of a clump and its settling rate. In Proceedings of the National Academy of Sciences in 2010, Kindler and others (http://www.sciencedaily.com/releases/2010/12/101208125759.htm) conclude that the highly porous marine snow (~95% water) may stall during their journey to the bottom when increasing water density halts settling. When diffusion eventually replaces the less dense water from shallower depths within the flakes with denser water, the agglomerations resume their journey to the bottom.
Besides its importance in the ocean carbon cycle, the amorphous organic matter (AOM) in marine snow is a great petroleum precursor. If preserved, due to low or zero oxygen in ocean floor sediments or overlying waters, and buried to a few km or more, the AOM will start producing liquid hydrocarbons. A good description of amorphous organic matter and various formation pathways, modern and ancient, is found in the 1995 text "Sedimentary Organic Matter" by R. V. Tyson. Pacton and others (2011; http://www.climategeology.ethz.ch/publications/2011a_Pacton_et_al.pdf) describe the structures and process of formation of amorphous organic matter at the sediment/water interface.

Tuesday, November 11, 2014

Veterans Day and carbon helping those who served

Today in the United States is Veterans' Day, a federal holiday honoring all Americans who have served in the military. Originally, this day was called Armistice Day, commemorating the end, by treaty, of hostilities on 11/11/1918 at 11:00 a.m. (in western Europe) in World War I, "the war to end all wars". However, after World War II, the day was expanded and renamed to honor all who have served in the armed forces. My grandfather served in Europe in WWI: he had been in the cavalry previously, riding a horse in the Mexican Expedition against Pancho Villa in 1916, but by the time of US involvement in WWI, his unit did not use horses, but tanks, as the "cavalry" still does today.

Googling his name online, I found my grandfather was reported to have been "wounded, degree undetermined" in September 1918. I never remember hearing about or noticing this injury, so it obviously must not have been debilitating. Hundreds of veterans of all wars, however, do live with permanent physical and mental disabilities. There is a new monument opened recently in Washington, DC, at the southwest foot of Capitol Hill, American Veterans Disabled for Life Memorial, that honors the sacrifice of military members severely wounded.
Looking to the south, across star-shaped and rectangular reflecting infinity pools to Voices of Veterans walls.

To the north towards the Botanic Gardens and US Capitol.


The bottom quote in the above portion of the Voices of Veterans wall is by Harold Russell, a World War II veteran who lost both his hands in a 1944 training accident. He is most famous for his portrayal of a returning wounded soldier, Homer Parrish, in "The Best Years of Our Lives" which won Best Picture at the 1947 Academy Awards. Russell won two Oscars: Best Supporting Actor and an honorary award for "bringing hope and courage to fellow veterans". I have seen the movie through at least once, but my favorite part, that I have seen several times, is at the end, when Homer, who has emotionally pushed away his fiancée since his return, accepts her love and commitment after she insists on helping him remove his prostheses getting ready for bed (http://www.youtube.com/watch?v=t-VB9JnppAU).

In the movie, Russell's prostheses appear to be primarily metal with leather. Charlie McGonegal, quoted above Russell on the Voices of Veterans wall, lost both arms in WWI and is featured in a 1944 War Department film, "Meet McGonegal", made to show how a double amputee can successfully manage every-day tasks. From watching the film, McGonegal's prostheses may include plastic.(McGonegal visited and worked with Russell during his recovery period, described in the book, Enabling Lives, 1999.)

A 2012 article from Collector's Weekly ("War and Prothetics: How Veterans Fought for the Perfect Artificial Limb; http://www.collectorsweekly.com/articles/war-and-prosthetics/) describes the history of prosthetic development and how, regrettably, war injuries have driven advancements in this technology, even though there are more US amputees due to diabetes. According to the article, plastics were first used by the Germans, after WWI, in prosthetic manufacture. Among the more space-age materials now used are carbon-fiber composites which have carbon fibers for reinforcement and a polymer matrix binder. Carbon fibers are manufactured primarily from petroleum-refinery byproducts or, rarely, directly from petroleum pitch or coal tar. These carbon materials provide strength and flexibility and are relatively lightweight. Carbon composites have myriad automotive and aerospace applications and are popular materials in sports equipment. An internet search reveals that prosthetic feet seem to be the most common artificial limbs using carbon composites. Of course, an important carbon fiber in military applications is Kevlar, used in body armor to protect from injury those that volunteer to defend their countries in the armed forces.

Wednesday, November 5, 2014

"Deep Carbon Through Deep Time" short course, GSA 2014


On Saturday, October 18, during the 2014 Geological Society of America annual meeting in Vancouver, I attended the short course “Deep Carbon Through Deep Time” sponsored by the Deep Carbon Observatory (DCO, ten-year interdisciplinary international project administered out of the Geophysical Laboratory, Carnegie Institution of Washington [CIW; https://deepcarbon.net/dco/deep-carbon-science]) and the Mineralogical Society of America. Having experience, either long-term or in passing, with a temperature range of carbon-bearing or organic rocks from mushy ocean floor muds through the anchizone to graphitic schists, I was interested in boldly going deeper than I carbonaceously had gone before.

What is the purpose of the Deep Carbon Observatory initiative? To quote from the short course description, “Yet in spite of carbon’s importance to geology, many aspects of the physical, chemical, and biological behavior of Earth’s subsurface carbon-bearing systems remain unresolved. . . How do deep reservoirs form and evolve? How does carbon move from one deep repository to another?”

Since most of us, when we think of the carbon cycle, usually consider the relatively-shallow upper crust, and Phanerozoic oceans and atmosphere, this short course could have been called “Deeper Carbon Through Deeper Time” because that is where it took me. As Robert Hazen, DCO Executive Director, and Craig Schiffries, DCO Director and former GSA Director for Geoscience Policy, wrote in the first chapter, "Why Deep Carbon?" in Carbon in Earth (2013, Reviews in Mineralogy and Geochemistry, Volume 75; http://www.minsocam.org/MSA/RIM/RiMG075/RiMG075_Ch01.pdf), possibly 90% of the earth's carbon may be in the Earth's deep interior: if carbonaceous chondrite meteorites, used as a compositional model for early planets, have 10-100 times the concentration of carbon as the earth's known carbon reservoirs, where is our missing carbon? Hazen and Schiffries write that identifying and quantifying carbon fluxes to and from the mantle are key in answering this question.

Seven speakers in the short course covered a range of topics within the four DCO communities (extreme physics and chemistry; reservoirs and fluxes; deep life; deep energy) including deep (mantle/core) carbon cycle, diamonds, volcano outgassing, carbon fluids, deep extremophiles (https://deepcarbon.net/sites/dco.rpi.edu/files/shortcourse-schedule-18oct14.pdf). These talks averaged 45-minutes to an hour each, which for soporific me in a small windowless conference room, could have meant a constant battle to stay awake, but I found the talks so gripping that only a couple times all day did I have to pinch myself.

A common theme among the talks was the history of the carbon itself: where it is now, where it had been, how long it was there: transport, reservoirs, residence time (=cycle time). Radiometric age dating, trace element geochemistry, and staple isotopes are among the techniques used on natural samples obtained through deep drilling or that have been brought within our relatively shallow sampling reach by geologic processes (i.e. diamonds). The magnitude of transit in time and depth for Earth carbon was apparent in Steve Shirey's (CIW) diamond talk in which inclusions captured within those crystals record ancient and profound journeys. While I have familiarity with crustal scale advective heat flow in basin thermal modeling, and some of that research has been associated with deep extremophile studies (how hot was the microbes’ environment), it was fascinating to hear Barbara Sherwood Lollar talk about adjacent (meter-scale), but separate, water sources in deep South African gold mines where one source had relatively young meteoric water and the other, unmixed, was millions of years old, both bearing microbes. Sherwood Lollar has also identified 1.5 billion-year-old fluid (non-microbial-bearing) in fractures in a deep mine in Ontario.

While there was a lot of new information presented, relative to my own background, the major take-away for me was a new or expanded scope of thinking about Earth carbon history and distribution. Perhaps the best example was the first talk by Bob Hazen on Mineral Evolution. From our earliest education as geologists, we are aware that plate tectonics, lithospheric differentiation, oxygen atmosphere, life were not present at planet formation, but evolved over the first few billion years of Earth history. However, I never knew or considered that the number of and variety within minerals has changed also, even though now this seems blatantly logical. Hazen’s talk went beyond the Earth and its infancy to mention where the first mineral formed: diamond condensed from supernova vapor in the early universe. The big stunner for some of us was that there are organic minerals, taking the definition of mineral as anything that creates a diffraction pattern, not the general inorganic vs. organic classifier we are initially taught.

Although the DCO initiative focuses on carbon, this endeavor encompasses essentially all disciplines of the earth sciences. I started to list the involved disciplines that came to mind, but realized I was listing everything under the geoscience umbrella. While participating researchers focus on what their own specialties can add to carbon knowledge, the conversation fostered by the DCO will produce a comprehensive and connected understanding of the Earth carbon system, and expand our individual scientific experience from local to “cosmos”-politan in terms of time, space, and process.

I highly recommend Carbon in Earth, Reviews in Mineralogy and Geochemistry, Volume 75 (2013, 680 pages), the medial publication of the 10-year DCO project. Many of the speakers at the short course are authors of chapters in this volume. It (and its spectacular graphics) is available as an Open Access publication at http://www.minsocam.org/MSA/RIM/Rim75.html

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.)