Geobulletin alpha

News from the Geoblogosphere feed

New from Snet: Lithologs, a new tool to create lithological/sedimentological logs online..

Blog post recommendation

Fieldwork Equations

I’m wrestling with two realities about paleontology.  The first involves paleontological fieldwork; the second, fieldwork’s aftermath.

To begin with, take fieldwork, a challenging and time consuming endeavor with no assured success.  In an essay on his own fieldwork, evolutionary biologist Stephen Jay Gould erected a straw man argument denigrating fieldwork – “An eminent colleague, a fine theoretician who has paid his dues in the field, once said to me, only partly facetiously, that fieldwork is one hell of a way to get information.  All that time, effort, and money, often for comparatively little when measured against the hours invested.”  (Opus 100, The Flamingo’s Smile:  Reflections in Natural History, 1985, p. 183-184.)  Responding with his characteristically affirming enthusiasm, Gould said that’s not the reality of fieldwork because the rewards are so great and the enjoyment abundant.  “[A]ll the frustration and dull, repetitive effort vanish to insignificance before the unalloyed joy of finding something new – and this pleasure can be savored nearly every day if one loves the little things as well.”  (p. 184)

Paleontologist Peter Vaughn turned fieldwork into an equation.  According to paleontologist Michael Novacek in his book Time Traveler:  In Search of Dinosaurs and Ancient Mammals from Montana to Mongolia (2002), Vaughn “described paleontological fieldwork as 49 percent anticipation, 49 percent recollection, and 2 percent success.”  (p. 49.)  Certainly, Vaughn was not railing against fieldwork; he was simply being realistic that a lot goes into it and the results are not assured.  Regardless of how puzzling this equation is (e.g., I’m really not sure what “recollection” is and wonder if he’s mixing apples and oranges), that two percent success is pretty slim.  That, asserted Vaughn, is the reality.

Given my last couple of experiences of carefully planning and carrying out forays into the field looking for the fossilized calcium carbonate shells of foraminifera and ostracodes with absolutely nothing to show for the effort, I decided, for just a moment, to ward off Gould’s zeal and buy into his straw man argument because, right then, I concluded a two percent solution isn’t a strong enough allure.  I eschewed fieldwork (my half-assed version of it) and bought (oh, the horror) some Cretaceous matrix online – yes, I let someone else do the fieldwork for me.

Sight unseen, I purchased slightly more than two and a half pounds of purportedly unsorted matrix collected from a Cretaceous formation from which I hoped to extract microfossil shells.  It didn’t start off well.  What tumbled out of the box that came through the mail was some pretty dispiriting rock.

There’s another paleontological reality which came into play at this point – fieldwork engenders tedious, painstaking, seemingly never ending lab work.  When Peter Makovicky, associate curator at the Field Museum, described the work on the fossil bones of the dinosaur Siats meekerorum, an apex predator, he concluded that every hour of fieldwork generated 100 hours of lab work (and, for the S. meekerorum, there was a lot of fieldwork – a summer of exploring and finding, and two summers of excavating).  (Steve Johnson, Dinosaur Discovered by Field Expedition Rivaled T. rex, Chicago Tribune, November 22, 2013.)

I am no stranger to that reality. Take my recent, unsuccessful efforts in the field, they generated many hours of soaking and screening matrix, and days spent hunched over the microscope.  In fact, for microfossils, it’s lab work itself that determines whether the fieldwork is successful or not.  In many ways, the lab work under those circumstances becomes a continuation of the searching and exploration in the field.

The mail-order Cretaceous material came with a mix of unknowns and knowns.  It was collected, at some unknown point in the past, at a construction site somewhere near the Texas town of Prosper (about 35 miles north of Dallas and marked in the geologic map below), by someone, whom I don’t know, who, for a small price, mailed it to me.

The polka-dotted green area in this map shows the presence of rocks of the Austin Group.  (This map is a tiny excerpt from the Sherman sheet of the geologic atlas of Texas.)   Somewhere in that green near Prosper was the construction site where the Atco Formation (part of the Austin Group) outcropped.  This material, averred the seller, came from this formation which dates to the Coniacian Age (89.8 to 86.3 million years ago) during the Upper Cretaceous Period.  One could be skeptical that the seller had it right about the formation, but, for better or worse (mostly worse), much about the matrix screams “Atco Formation!”

The rocks of the Atco Formation are dominated by, and bound together by, calcium carbonate. It has been described as composed of “thin-bedded calcisiltite and indurated chalky limestone interbedded with gray calcareous shale and mudstone.”  (Charles C. Smith, Calcareous Nannoplankton and Stratigraphy of Late Turonian, Coniacian, and Early Santonian Age of the Eagle Ford and Austin Groups of Texas, Geological Survey Professional Paper 1075, U.S. Geological Survey, 1981, p. 1)  The key word is “indurated.”  Porous rock is considered indurated if it has been “cemented” together through mineral deposition.  (John O. E. Clark and Stella Stiegeler, The Facts on File Dictionary of Earth Science, 2000, p. 172.)  In other words, it becomes very solid, resistant to pressure and scraping.  Appropriately enough, the formation is named after the company whose quarry is the type locality – the Universal Atlas Cement Company (of McLennan County, Texas).

A lot of what I bought is chunks of hard rock, studded with bits of pebbles and, on occasion, teeth; the rest is fairly friable, crumbling with manual pressure.  With some of former, I decided to sacrifice the microfossil shells by soaking these chunks in vinegar, letting the acetic acid interact with the calcium carbonate in the rock, turning it into calcium acetate which stays in solution and carbon dioxide which bubbles away.  Time consuming, sure, but I just let the acid do its thing.  The effort has been going on for some three weeks – I periodically refresh the vinegar, and poke at and otherwise abrade the surfaces of the soaking rocks  to expose more calcium carbonate.  I am encouraged – some of these pieces are actually breaking apart.

There are “little things” in the effort to dissolve the calcium carbonate that have exerted a bit of magic and kept me engaged, even opening up new areas of exploration (such as the chemistry of the interaction between calcium carbonate and acetic acid).  Just the visual display that is involved in the process is entertaining.  One piece of matrix, which gave off bubbles at a furious pace from several points on its surface, amused me for some time because of the organized array of bubbles that emanated from it and how they arranged themselves on the surface of the vinegar – miniature, carbon dioxide fireworks.

The material that could be crumbled into much smaller grains was soaked in water for several days and then screened.  The smallest of the particles captured by my screens might yield forams and ostracodes, if anything in this material will.  Afraid of the verdict, I haven’t yet examined this material for microfossils.  But, I have scrutinized the particles of one millimeter or slightly larger and, though few, there have been some interesting finds.  Here are a couple of them.

The first specimen is a tooth from a shark, a Squalicorax falcatus.  The tooth is certainly the worse for wear, but some of the serrations have come through those nearly 90 million years.  The second photo shows the occlusal (left in the photo) and lingual (right) sides of a tiny tooth from what I believe to be a Ptychotrygon triangularis, a ray.  Both are first time finds for me.  (These identifications are based on Bruce J. Welton and Roger F. Farish’s The Collector’s Guide to Fossil Sharks and Rays From the Cretaceous of Texas, 1993.)

Okay, it’s not much to show for three weeks and counting invested in two and half pounds of mercenary Cretaceous matrix – some bubbles and a few teeth.  The work has been tedious and tiring, but, I have to admit that Gould had it right – be open to enjoying and marveling in those “little things” experienced in the field and, I'd add, in some of the lab work as well.

When biologist and gardener Roger B. Swain penned a piece about Viktor Muhlenbach of the Missouri Botanical Garden, who spent years walking along the railroad tracks in St. Louis cataloguing the incredible variety of flora he found growing there, Swain reflected on the possible attraction such an activity might hold.  He likened walking the rails searching for plants to similar endeavors such as birding and beachcombing.  I’d insert paleontological fieldwork and, even, some lab work into his list.  Swain concluded that their allure arises from the very doubt about the outcome.  He wrote,
Such excursions are risky, of course.  There is always the chance that you’ll find nothing, but that chance makes the finding more momentous . . . .  That very uncertainty is more important than most of us realize.  God does play dice with the universe, and out of the uncertainty comes anticipation, and, in turn, hope.  (Field Days:  Journal of an Itinerant Biologist, 1983, p. 122.) | Impressum