Home Ec. 101 ~ The Hunt for Microfossils

As I delve deeper into micropaleontology, that study of the smallest of fossils, I feel like I’m in a high school Home Ec. class.  This post is mostly about that Home Ec. process with some asides for what continues to intrigue me – the etymological history of some of the words that crop up, some from the world of paleontology, others not.

The sedimentary material I recently prepared for microscopic study came from North Carolina’s Lee Creek Mine, specifically the Pungo River Formation, a mid-Miocene Epoch rock formation, some 20.5 to 14.8 million years old.  It’s not unusual for this amateur paleontologist to futz around in the basement and in the laundry room.  Shark teeth, whale bones, and shells often bathe in pans of water sitting on the washing machine or are strewn about drying.  But my pursuit of the microfossils hiding in this sedimentary material has decidedly more domestic trappings than that.

I cannot resist this first etymological aside.  Futz is such an expressive word for describing the idle fiddling away or squandering of time.  According to The New Oxford American Dictionary, it may have originated with the Yiddish word arumfartzen which means to “fart around.”  Ah, yes.

Anyway, the sediment preparation began with a laundry room phase involving Calgon Water Softener (“Add to your wash for whiter and brighter clothes.”).  I poured the sedimentary material into a solution of Calgon and water, and let the whole thing steep for 48 hours.

Calgon.  Though it may not have been necessary for this sediment, it certainly deserves a bit of explanation.  In this, my use of Calgon was prompted by various sources describing preparation of microfossils, including the steps briefly described by geologist T. Markham Puckett in his monumental study of Alabama ostracode fossils (Ecological Atlas of Upper Cretaceous Ostracodes of Alabama, Geological Survey of Alabama, Monograph 14, 1996.).  [I edited this previous sentence which originally stated that I followed Puckett's steps as best I could.  Clearly, not true.  For instance, he used a solution of Calgon and hydrogen peroxide (concentrations unstated), and the soaking lasted only over night.  In contrast, my material soaked for 48 hours in a roughly 0.5% Calgon solution.]  In a previous post, I briefly discussed ostracodes which are ubiquitous, microscopic crustaceans living within two tests (shells); the tests are what fossilize, though, on rare occasion, the delicate animal within is preserved.  I am really hoping that, at some point, my efforts with this Miocene material will turn up ostracodes.  No such luck to date, but fossil shells of foraminifera have graced the field of my microscope.  More on those microfossils below.

Because there are no hand tools to safely extract fragile microfossil shells from, say, a clot of clay, the addition of chemical agents to the bath is called for, in an effort to break up the sedimentary material.  Calgon, at least in its earlier formulations, acted to deflocculate particles in liquid solution.  In essence, a deflocculant chemically neutralizes the charges on the particles in a solution and, so, keeps them from aggregating.  By exposing this sediment to deflocculants, the microfossils will be separated from the other particles in the sediment.  Alkaline salts, such as sodium, act to deflocculate soil.  Calgon no longer has phosphates which, according to some websites, has robbed it of its value as a deflocculant.  I’m not so sure of that, because, based on the manufacturer’s description of its chemical composition, the ingredients in the current incarnation of Calgon sitting in my laundry room include salts that are known deflocculants.  (I didn’t explore this chemical process as much as I should have.  Nevertheless, of some use was Deflocculants: A Detailed Overview by Dr. Nilo Tozzi.  The definition of flocculation in The Facts on File Dictionary of Earth Science by John O.E. Clark and Stella Stiegeler (2000) was also helpful.)

After that digression on Calgon and its role as a deflocculant, I may as well wander even farther from my path and explore the field I find myself in, an etymological field full of . . . sheep.  All of these variations of the words deflocculate and flocculate have everything to do with floccules – that’s what a deflocculant seeks to break up and a flocculant to create.  The New Oxford American Dictionary defines a floccule (noun) as “a small clump of material that resembles a tuft of wool.”  Hiking still deeper into this field takes me to the Latin word flocc meaning “a lock of wool, flake.”  (Donald J. Borror, Dictionary of Word Roots and Combining Forms (1988).)  But it gets better.  Flocc leads ultimately to the word flock.

After two days, I did the poor man’s trick of screening my material in clean water by using pieces of a pair of woman’s stockings.  I have not taken the plunge and invested in a scientific sieve with mesh openings of the recommended size.  In a nicely done piece for K-12 educators titled Preparation Techniques for Use of Foraminifera in the Classroom, geologist Scott W. Snyder and paleobiologist Brian T. Huber note that the purchase of such a sieve is “probably the single most expensive item needed to properly prepare samples” which explains why I don’t yet have one.  Let’s see what turns up with my crude methods, first.

With my now cleaned, screened, disaggregated sediment, I crossed a critical line by taking it into . . . the kitchen.

In my household the kitchen is mostly my domain, so this shift in “culinary” activity didn’t generate much pushback from my significant other (perhaps she was still wondering what happened to that pair of stockings).  I lined several cookie sheets with aluminum foil and then covered them with a thin layer of wet sedimentary material.  I baked those sheets for two hours in an oven set at 170º F (its lowest setting – Puckett used a still lower temperature) and waited, not for rising, but for drying.  A slightly acrid, earthy smell filled the kitchen.  (Nothing to excite the salivary glands.)  Then the trays were set out to cool.

To be honest I’ve just begun the process of scanning the material under the microscope.  The results so far have been mixed.  As I noted earlier, ostracodes are my primary target and have eluded me so far.  Not so the shells of foraminifera, or forams as they are commonly called.  To date a few forams have been “captured” under the scope, using a very fine paint brush dipped in water to lift my quarry out of the sample and onto a slide for safekeeping.

Forams are amazing creatures given that they, like amoebas, consist of a single nucleated cell.  Their fossil record is long and they’re still with us.  The tests of these protists are usually made of calcite or aragonite, typically contain several chambers, and come in myriad shapes – some dramatic spirals, others seem to be random aggregations of little balls, still others complex braids like loaves of bread.  The shells for some taxa are secreted, while, for others, the animal builds them from available particles in its surroundings.  A single cell that builds structures from grains of sand and other particles simply beggars the imagination.

I was puzzled by paleontologist Donald Prothero’s description of the shells as being “internal” until I realized that a foram’s shell is pockmarked with many pores through which the foram extends “pseudopods” – long filaments of its cytoplasm by means of which it feeds and moves.  (Bringing Fossils to Life:  An Introduction to Paleobiology, 1998, p. 191).  So, when a foram is active, the shell is, for all intents and purposes, internal.  Prothero wryly notes,

Active foraminiferans are difficult to keep track of in a Petri dish, since they have the annoying habit of creeping up and out of the dish before the investigator is aware of it.  (p. 191.)

[Later edit:  I thought I'd understood the "internal" nature of the foraminifera's shell or test, but now I think I was wrong.  According to Howard A. Armstrong and Martin D. Brasier, in Microfossils (2nd edition, 2005), the test really is internal because the organism's cytoplasm is divided into (1) endoplasm which is found inside the test and contains the nucleus and organelles (mitochondria, etc.), and (2) clear ectoplasm which covers the outside of the test in a thin layer and is connected to the endoplasm through an aperture in the test.  They describe the pseudopods as extending from the ectoplasm.]

I like Prothero’s explication of the origin of the name for these protists.  He states that foramina means “windows” and ferre is “to bear.”  Yes, this animal, all of one cell large, carries many windows in its shell out which it may pour and through which it may retreat.

The photograph below shows a live foram, an Ammonia tepida, with pseudopods aflutter.  The image was taken by Scott Fay, UC Berkeley, 2005.  It is used in this blog under a Creative Commons Attribution-Share Alike 2.5 Generic license.

Foraminifera date from the early Cambrian, giving them “a fossil record as old as any other phylum of eukaryotic organism.”  (Prothero, p. 195; eukaryotes have DNA enclosed in a nucleus.)  Given their presence in nearly all marine environments, their fossils are widely used to identify marine strata and explore paleoclimates, as well as to aid in the search for oil.  In fact, “[t]he sand of many tropical beaches is composed entirely of the skeletons of benthic [bottom dwelling] foraminifera.”  (Prothero, p. 190.)

Microfossil Image Recovery and Circulation for Learning and Education (MIRACLE) of the University College London provides an excellent online introduction of foraminifera with some good images of fossil forams from different environments and time periods.

So, what did my Home Ec. class lead to?  For the moment I’m focusing on two different kinds of foram that have appeared in this Miocene sediment.  My primary source for identifications is the chapter titled Key Foraminifera From Upper Oligocene to Lower Pleistocene Strata of the Central Atlantic Coast Plain, by Thomas G. Gibson, which appears in Geology and Paleontology of the Lee Creek Mine, North Carolina, Volume I, edited by Clayton E. Ray (1983).  Gibson notes that material from Lee Creek’s Pungo River Formation is “highly phosphatized” which is not surprising given that this is a phosphate mine.  (p. 359.)  But, I’m not certain what the implications of that condition are for my efforts, though my early finds are very mineralized and lack details.  Perhaps that's part of it.

I believe the specimen that appears below is from the foram genus Bolivina and may be a B. pungoensis, a new species identified by Gibson in 1983.  It’s less than half a millimeter big.  The faint lines mark the individual chambers this creature made many millions of years ago.  This image and the second one below were captured by a small camera fit into one of the scope’s tubes.  The objective lens is a 3X power and the camera multiplies that image by some factor I have yet to figure out.

The second type is, I believe, from the genus Globorotalia, though, of course, it may not be.  Again, it’s smaller than half a millimeter.

I think I just heard a timer go off.  Time to take some cookie sheets out of the oven.