Trace Fossils and Sed/Strat

Ichnofacies represent recurring groupings of trace fossils, and are the backbone of many sedimentological and stratigraphic applications of trace fossil studies. Initial identification of recurring ichnofossil assemblages lead Adolf Seilacher to propose several distinct ichnofacies, and relate them to specific marine depositional environments (Seilacher, 1953; Seilacher, 1967). The fact that many of these ichnofacies seemed to be depth dependent caused quite a stir; after all, infallible bathymetric data would considerably simplify much of our interpretations of marine depositional environments. This simple relationship was shown to be incorrect, however (Frey et al., 1990). Various environmental factors, including energy (which controls sedimentation rate, turbidity, and substrate characteristics), the availability of light and oxygen, and the salinity of the ambient water all plays an important role in the occurrence of critters and their traces (Pemberton and MacEachern, 2006).

Reproduced here is Figure 1 (page 156) from Frey et al. (1990), showing the distribution of various ichnofacies as representative of, but NOT exclusive to, specific suites of depositional systems. For instance, the diagrammatic sandy submarine fan system on the right side of the diagram is shown as being typified by the Skolithos ichnofacies, which is also shown as occurring in the nearshore (foreshore) environment on the left side of the diagram. This illustrates that the creatures are more attuned to the exploitation of high energy, sandy subtrates, rather than being restricted by some bathymetric concern.

Although this more complicated view of ichnofacies pretty much dashes our hopes of a simple bathymetric evaluation of marine rocks based on critter tracks, it does provide us a very useful way to track changing energy conditions in a succession of rocks. Additionally, the time scale at which animals produce their tracks is considerably finer than any resolution we can have in the rock record. Most trace-makers have life spans in the range of months, allowing us to compare cross-cutting and tiering relationships, or the relative timing of emplacement (particularly where escape structures are preserved).

Distinguishing event beds in the rock record is an area where trace assemblages have been shown to help. Frey (1990) identified an assemblage unique to storm beds; as one might expect, the background quiet-water conditions were typified by lots of delicate surface traces, and are juxtaposed with hardier and deeper-burrowing forms in the sandy storm beds.

The picture above, a heavily bioturbated sandstone from the Blackleaf Formation in Montana, shows almost no distinguishing morphologies (possible Ophiomorphia can be distinguished if you are up-close and lucky); however, because of the preferential diagenetic alteration of the tunnel networks, we can see pretty clearly distinct horizons of trace-maker activity, suggesting that there are cryptic surfaces of nondeposition preserved within lower shoreface sand. One can trace these surfaces out laterally, where they sometimes grade into bounding surfaces for packages of swaley-cross stratified sands.

Another ichnofacies with time-stratigraphic importance is the Glossifungites icnhofacies. This is an assemblage of burrows formed in a firmground, often compacted and dewatered muds, and dominated by vertical burrows (like Skolithos or Diplocraterion) and box-work tunnel systems (like Thalassinoides) (Pemberton and Frey, 1985). Commonly, many of these traces are passively infilled, often by coarser material than the substrate. In siliciclastic settings, most firmgrounds are often associated with erosionally exhumed substrates that have been inundated by marine waters. These firmgrounds indicate the presence of a depositional discontinuity between initial erosional exposure of the substrate and later sedimentation (Pemberton and MacEachern, 2006). It is during this discontinuity that the surface is colonized and bioturbated. Thus, the presence of this ichnofacies can have important implications for demarcating erosional surfaces, and therefore has implications for genetic stratigraphic or sequence stratigraphic frameworks.

REFERENCES

Frey, R.W., 1990, Trace fossils and hummocky cross-stratification, Upper Cretaceous of Utah:
Journal of Sedimentary Petrology, v. 43, p. 203-218.

Frey, R.W., Pemberton, S.G., and Saunders, T.D.A., 1990, Ichnofacies and bathymetry: a passive
relationship: Journal of Paleontology, v. 64, p. 155-158.

Pemberton, S.G., and Frey, R.W., 1985, The Glossifungites ichnofacies: modern examples from
the Georgia coast, USA in Curran, H.A. (ed), Biogenic Structures: Their Use in Interpreting Depositional Environments, SEPM Special Publication 35, p. 237-259.

Pemberton, S.G., and MacEachern J.A., 2006, Applied Ichnology Short Course: The Use of Trace
Fossils in Sequence Stratigraphy, Exploration and Production Geology: SEPM Short Course 18, Houston, TX, 274 p.

Seilacher, A., 1953: Studien zur palichnologie. I: Uber die methoden der palichnologie: Neues
Jahrbuch fur Geologie und Paleontologie, Abandlungen, 98, p. 87-124.

Seilacher, A., 1967, Bathymetry of Trace Fossils: Marine Geology, v. 5, p. 413-428.

Trace Fossils - Critterology meets Sedimentology

Thanks, gentle readers, for indulging my ichno-fetish.

Trace fossils represent the intersection of critterology with sedimentology, preserving a wide variety of information valuable to both the sedimentologist/stratigrapher and the paleontologist. Importantly, trace fossils are essentially un-reworkable, and therefore reflect biological activity preserved in situ within the host sediment. The morphology of an individual trace is determined by three things: the Morphology of the animal, the Behavior of the animal, and the Substrate characteristics in which the trace is being made. It’s the intersection of these three attributes that define the resultant trace. For instance, if a trilobite is hanging around the sea-floor, resting up for a late night foraging party, it might produce Rusophycus; if that trilobite gets scared by some predatory critter swimming overhead and decides to make a run for it, it might produce a Cruziana. So the behavior of the little guy decides the morphology of the trace (similarly, think about sediment bulldozers scooping up food versus sediment probers that search out organic matter systematically). Substrate can have a very strong influence on traces; when a shrimp is burrowing in a firm substrate, it might produce a Thalassinoides, whereas in goopy or shifting sediment conditions, it will make an Ophiomorpha.

The recognition of various repetitive behaviors has lead to a categorization of traces based on classes of activity. This ethological nomenclature has produced seven categories:

CUBICHNIA: resting traces
DOMICHNIA: dwelling traces
FODICHNIA: food mining traces
AGRICHNIA: farming traces
PASCICHNIA: grazing traces
REPICHNIA: crawling traces
FUGICHNIA: escape traces

Importantly, some of these behaviors may overlap. For instance, some critters may live in a burrow, and probe the surrounding sediments for food, producing a combination feeding trace/dwelling trace.

Of course, though trace fossils may represent these above behaviors, we all know that the nomenclature of traces is considerably more complicated. In reality, ichnologists classify individual traces on the basis of their morphological characteristics, separating individual morphs into ichnogenera and ichnospecies based on specific characteristics. The interpretation of the trace maker’s biology is secondary to the classification of traces; indeed, traces can be produced by a variety of disparate critters which have evolved to exploit the same niche (Trilobites and Horseshoe crabs, for instance) and therefore perform the same behaviors.

However, the ethological concept does have important implications for the recognition of patterns within the trace fossil record. Importantly, the behaviors and morphology of the critters in question are the result of evolutionary processes; natural selection driving species to exploit specific niches in order to survive. Important selective pressures in the ocean include food and light availability, salinity, substrate consistency, and wave or current energy, which are themselves often contingent on geologically important processes. So suites of organisms have evolved to live in the upper shoreface (for instance), where energy is high (and substrates are therefore sandy and often mobilized) and food is scare. Similarly, some organisms have evolved to live in deep water conditions, with low energy but lots of organic matter available. The strategies that these organisms employ for their survival determine the traces they leave behind. This is the foundation for the concept of ichnofacies.


This image is a picture of a pyritized Ophiomorpha burrow from the Eagle Sandstone in Montana (Upper K, and equivalent to the Milk River in Canada).

This image is a heavily bioturbated sandstone from the Thermopolis shale (Albian) near Bozeman, MT. This is a view of the sole of the bed. Faint HCS could be seen in the bed, and the sands exhibit a sharp contact with the underlying offshore muds. Above, the beds grade into Swaley X-strata and low-angle and planer cross-beds, so it’s interpreted as a shallowing upward shoreface succession.


This medium- to coarse-sandstone bed shows basal scours, rip-ups, and HCS, and has a pretty heavily churned upper surface. Handlens and cathead for scale.

I think next time we’ll dive into the nitty gritty of ichnofacies.

Lebensspuren

Or, as those of us who don’t speak German would say, Trace Fossils.

Trace fossils are a truly unique source of sedimentological and stratigraphic data, providing us with all sorts of nitty-gritty detail about salinity, turbidity, and time relationships along surfaces and within deposits. Marine traces provide us with nifty zonation schemes that can differentiate sub-environments based on wave and current energy, provide sequence stratigraphic info, and even have important ramifications for petroleum geology.

As a field geologists, traces can be a big help in deciphering depositional environments. For folks who work in core, however, they may be even more important; when all you’ve got is 3 inches, spotting a Skolithos or Zoophycus is much easier than nabbing a hummock, for instance.

Anyway, I thought I’d share a few pictures of traces I’ve run across in the field. In future posts, I think I’ll discuss ichnofacies models, petroleum geology applications, and maybe delve into the controversy of nonmarine ichnofacies.

As always, click on the pictures to make em bigger

This first picture is from the Albian Blackleaf Formation in Southwest Montana, and shows some meandering Planolites winding there way along a the contact between a mudrock below and a sandstone above (the sandstone shows some Micro-HCS, which I may talk about later...)

This second image shows a surface chewed up by a whole bunch of little guys; Planolites, maybe some Skolithos. I suppose this is why we have experts in this stuff; takes a trained eye to pick out all the different morphs! This image is from the Book Cliffs, Utah.

This image shows Ophiomorpha; this is a dwelling trace for a shrimp-like fellow, who stuck fecal pellets to the side wall in order to support the tube-structure, implying that the sediment was fairly loose and shifty when the little guy decided to live there. This is a Book Cliffs trace, too.

Finally, shallowing somewhat, here's a picture of a Psilonichnus, a branching, y-shaped tube. These guys can go pretty far into the substrate, and are dwelling tubes for little crab-like critters living in the foreshore. The animals would have to burrow down deep to hit the water table, allowing them to live above wave base.

Expanding Earth and the Conspiracy of Science

As far as wonky pseudo-science goes, the expanding earth nonsense really stands out as a noteworthy endeavor. The high priest of an em-biggening (to borrow from the Simpsons) Earth is one Neal Adams, former comic book illustrator and the man that designed the Nasenex Bee from those commercials (for which he must be punished). I first heard about ol’ Neal from a podcast called “The Skeptic’s Guide to the Galaxy” (which hails from a little corner of the internet known as http://www.theskepticsguide.org/ ), where they actually interview the guy; apoplexy ensued, I can assure you.

Anyway, Neal “the Bee” Adams believes that the Earth is getting bigger through time. He’s convinced that subduction doesn’t actually exist, that oceanic crust is spontaneously generated at spreading ridges, and all sorts of fun stuff. Below, you’ll find an animation from Adams explaining his idea. Be forewarned, however, that the narration is strongly reminiscent of Kirk Cameron’s hyper-smug, aggressively ignorant young earth creationism spiels; those with heart conditions or anger management issues may wish to abstain.



It’s all pretty silly stuff; my favorite line is the “knee-jerk theory of Pangaea”; I hear that was Naomi Oreskes’ original title for “The Rejection of Continental Drift: Theory and Method in American Earth Science” (a great read, by the way).

Though it would be easy (and entertaining, too; it would probably make a good drinking game) to pick apart all the inaccuracies with our “facts”, that’s not what we’re going to do here. Rather, what interests me is the WHY question: WHY do Adams, and others, believe what they believe?

First and foremost, as you must have gleaned from watching the ceaseless (10 minutes!!! Really!?! C’mon!) video above, the Expanding Earth theory is much more than an attack on the Earth Sciences. According to the theory, the earth must have been much smaller back in dinosaur days; to those of us who are shackled by our “reality-based” worldview (quote from the current Bush administration), this would seem to imply that the earth must have been much more dense in old times, right? Au contraire, gentle readers; Neil says the earth was MUCH lighter then (as reported from the podcast; I’ll link to it if I can find it in the archives). In fact it was the lessened gravity that allowed the Dinosaurs to walk around, since they would have been too heavy to survive otherwise. So how does the earth expand? Matter is being created and added through some “quantum” process. Duh.

So it’s not like Adams thinks we’ve mapped a few thrusts wrong, or incorrectly interpreted ophiolites. In fact, Geology is just one little wrong-bit on the vast, incorrect corpus of science itself. The Expanding Earth theory is a fundamental rejection of not just one or two sciences, but the ENTIRE body of science, its methodologies, its theories and interpretations, and its practitioners.

Why? Why is there such antagonism towards the sciences? The narration in the video pleadingly states that the universe must be simpler than we “experts” would have it. Such good old arguing from ignorance is a well-worn tactic from a variety of pseudo-science folks, of course, and sadly difficult to remedy. Facts have little strength when arrayed against someone who “knows” that they are meaningless.

None of this is new, of course; anybody who has gone to the mat with some bible-thumping young-earthers has heard all this before. What is new, at least to me, is the EXPLICIT statement of a scientific conspiracy meant to hide the truth, and promulgate our Wegenerian worldview at the expense of the TRUTH. My feeling is that most Creationists view us as sadly misguided individuals, blinded by our atheistic hubris into believing what we say about evolution.

But the expanding earth crowd calls us out on our duplicity; they state that we KNOW the earth is expanding, and are nefariously trying to hide it from the public. Man, if this is true, why the hell did I spend all of December and January furiously writing grants? Shouldn’t I have just called up my local Illuminati and had then send over a couple of sacks of cash (all the while cackling madly, mind you).

To my eye, this is anti-intellectualism of a different color. The creationists define the world into a humanistic, rationalistic view versus their divinely inspired book, forming their attacks on us in terms of heretical (sciences) versus canonical (them) language. Neil Adams’ approach is a distinctly Gnostic anti-intellectualism, wherein his intuitive understanding that the world simply can’t work the way we say it does gives him all the authority he needs to effectively throw out everything we know.

This is a disturbing trend. The creationists are, in many ways, beyond our reach. Their reaction to us is understandable, in the context that a world view requiring special creation at 4004 BCE is fundamentally incompatible with Canyon Diablo radiometric dating, natural selection, and deep time. More disturbing to me is the conspiratorial view of sciences, the rejection of reality in favor of a self-made delusion formed from a visceral dislike of scientists. Expanding earthers, holistic medicine types, vaccine-opponents, climate change deniers; all of these groups are symptoms of a broader disease at the heart of our society. This Gnostic anti-intellectual movement is more insidious and probably more pervasive in our culture than we realize. Additionally, I would argue that it is caused by our collective failure to have engaged the public in any meaningful way. It’s this disseminated distrust of scientists that has allowed the Discovery Institute to come into existence. It’s this that has allowed such a divisive group of creationists nut-jobs, each with their own pet story of creation, to present a unified front. The creationists and their rhetoric aren’t the only enemies we face in the struggle for the brains of America, and we might want to start thinking more about how we can make research more transparent and understandable for the regular folks out there if we ever want to move science funding and scientific work back into a valued component of our culture.

Departmental Accreditation

I’m sure we’ve all been getting demands from various societies (GSA, AAPG, SEPM, et. al) to partake in a survey meant to address the issue of department accreditation. The preamble cites decreased enrollment in geosciences programs, departments threatened with merging and closure, and low hiring in the academic realm as reasons for developing a national accreditation for geology departments. Additionally, the generally low impact the geosciences have had on policy, decreased public awareness, and little pre-college earth science education seem to be concerns.

This accreditation scheme is summarized by five models (mostly ranging from impotent to draconian in severity), which we can peruse at http://www.geosociety.org/flyers/GSA_AccredSurveyModelGrid.pdf .

I’m not certain what I think of this idea yet. What do other folks think? Is a national system of accreditation the way to go? It might force departments to take a more active interest in the broader community, but then again it might stretch stressed departments to the breaking point. Any thoughts?

Nonmarine Waltherian Successions?

The key to much of our understanding of stratigraphy relies heavily on Walther’s Law. The vertical juxtaposition of deposits that represent various depositional environments allows us to pick surfaces, correlate wide-spread geological processes, and determine time-rock and time-surface relationships; in other words, it’s kind of important to the whole sedimentology and stratigraphy thing.

While Walther’s Law works pretty well for shallow marine successions (for instance, the shoreface succession), we start to get into hazy territory in nonmarine environments (and deep marine, too). What is a Waltherian succession in an evaporative lake? How about in fluvial/alluvial successions? More to the point, when do we pick a surface that delineates a non-waltherian succession?


Once again, I present some pretty pictures gleaned from NASA World Wind! ENJOY!



This first picture is an overhead view of a lake basin north of the Ordos basin; a river, sourced from nearby mountains, feeds a large lacustrine delta, with distributary network, near a pretty good-sized dune field in the lower left. Alluvial fans make an apperance as well. If the lake levels drop, how will the migration of these disparate features be recorded, and how would we interpret them? Could get kinda complicated.



This second image is an oblique view (at 10x VE).



This last picture is a pretty nifty image of some Kelvin-Helmholtz instabilities developing on the edge of a hypopycnal plume.

Gender parity in the Geosciences

I recently received my free, complimentary issue of Nature Geoscience (Vol. 1, No. 2), the new earth-science flavored journal from Nature. I’ve always enjoyed reading through journals like Nature and Science (at the library, since they’re a little on the ridiculously expensive side), since they often have a large number of articles and editorials about scientific culture, in addition to their science content. Anyway, they seem to be keeping with that trend in this specialty journal, where there was an interesting article on gender disparity within the Geosciences (“Gender Imbalance in US Geoscience Academia” by Holmes, O’Connell, Frey, and Ongley, pg. 79-82.)

I think everyone in the geosciences is aware of the VERY low diversity (both racial and gender) in our field. In fact, according to the paper (and works cited therein), the Earth Sciences have the LOWEST ethnic and racial diversity of all science, technology, engineering, and mathematics fields. As for gender disparity, we are only better than the physics and engineering communities, and considerably worse than the chemistry and biology folks. The authors of this article are interested in why this disparity has persisted, and how members of the geosciences view the causes and consequences of this problem.

I’ve scanned and posted Fig. 1 from Holmes et al. (2008; pg. 79) below. The authors point out that the retention of women in a PhD program is the same as the retention of men in programs (so more women aren’t being driven out mid-grad school), which apparently is not the case for other fields.



The disturbing statistics, however, are seen in the numbers for academic employment (the blue portion of the graph). Only 14% of tenured faculty are women, and ONLY 8%(!!!!) are full professors. These are pretty startling numbers; I think most of us knew it was bad, but didn’t know it was THAT bad. So how do Earth Scientists explain this imbalance? The authors polled a group of 40 women and 39 men, at various levels of their academic career (from dewy young students to hoary old profs), and found three broad themes that the respondents fell into:

1) Structural Issues related to academia (for instance, family leave policies)
2) The “Pipeline” (a historical contingency related to low numbers of women PhD’s from the 70’s)
3) Intrinsic female attributes (including, apparently, comments from respondents that included views such as “women lack self-confidence or the toughness necessary to succeed in academia”

The answers given showed a strong correlation to the responder’s gender (surprise, surprise). Before I give it away, I’ll give you a minute to make your own prediction.

Done? Okay, below is Fig. 2 (pg. 81) from Holmes et al. (2008), scanned by me.

As shown above, men and women felt equally that there were structural issues within the academic world that made it more difficult for women to enter academics, while fewer women thought that the pipeline issue was of real importance. The third issue, which I shall re-term “womeny-ness”, was identified as an issue by ten men and only one woman. I’m going to go out on a limb here and guess (warning: Ad Hominem attack comin’ on-line) that these respondents thought women were too touchy-feely for the work; they probably also think Mexicans are lazy and Poles are stupid. On a serious note, maybe the disparity in issue three explains why people identified issue one (structural issues) as important.

Apparently, the responders’ quotes on issue three included such gems as “females in general prefer to teach”; “females lack self-confidence”; “females in general have a low interest in the subject matter”; and my favorite “females don’t like field work”.

Also problematic is how the solution to the disparity problem is viewed. Apparently, a majority of men think that we just have to sit back and wait for the problem to sort itself out, which sounds a lot like my strategy for cleaning my office. I don’t know what the answer is (although I’m sure lots of folks have given this very problem some serious thought), but I’m pretty sure the solution isn’t going to include a “do nothing and wait” option.

The fact of the matter is, we need to take a very serious look at the problems of racial, ethnic, and gender disparities in our field. First and foremost, it ain’t the 1880’s anymore. Women can vote, lynching is illegal, and we can’t send kids into the lead mines to work anymore; we should fix this problem because it needs to be fixed.

Secondly, no matter what we think of ourselves and our intellectual chops, science is a communal endeavor. The more people playing the game, the more stuff gets done. From a purely scientific standpoint, we all KNOW that having people with lots of different backgrounds and experiences lets us attack our geological problems with more success. We need to come together as a scientific community and seriously address where we have failed to allow a broader range of individuals to get into the Earth Sciences.

Okovango "Delta"

I was recently given a copy of the Planet Earth series (with David Attenborough), which I guess is a fairly recent set of pretty slick nature-type programs with some absolutely incredibly images. Anyway, on one of the episodes (I think the first one, “Pole to Pole”), which sort of dealt with water and how its distribution controls and effects ecosystems, there was a pretty cool segment about the Okovango “delta”, which is a huge terminal splay of the Okovango river that is completely land-locked, and empties into the Kalahari desert.

Sedimentologically, the Okovango system has become a sort of controversial model for a “terminal fan” or “subaerial fan” fluvial facies (see Stanistreet and McCarthy, 1993, Sedimentary Geology, and North and Warwick, 2007 JSR for a pretty sound rebuttal of the whole idea). I suspect that the presence of the distributary network has more to do with the presence of a relict lake basin in the terminal position, as opposed to any intrinsic river process unique to the Okovango. Regardless, it is still an absolutely incredible place, so I thought I’d post some nifty pictures, garnered from NASA World Wind (a Google Earth simulacrum). Click on 'em to make 'em big.

This first image just shows the Okovango Delta in the upper portion of the image, sort of near the center of Africa; its a pretty big feature!

This is a close up composite image of the distributary system of the Okovango.
The drainage basin of the Okovango.

Stationarity

Geomorphology-based frameworks are a part of the fundamental theoretical base upon which much of stratigraphy and sedimentary geology is built. This is most commonly seen in facies models, which use geomorphic organization of modern systems as a template to interpret (via Walther’s Law) the paleoenvironmental significance of a deposit (maybe in a future post I’ll cast all sorts of aspersions on this premise, to the tune of Roscoe Jackson).Anyway, what we, as sedimentologists, always have to keep in mind is the theoretical background deployed by geomorphologists in their work, and what the potential ramifications of this geomorph worldview is.

A recent paper in Science (Milly et al., 2008, Science v.319, 1 Feb) suggests that one of the sacred cows of modern geomorphology, the concept of stationarity, may be dead. Stationarity is the idea that natural systems, such as rivers, fluctuate around a mean value within a well defined and stationary envelope of variability. It is this concept that allows fluvial geomorphologists to take an instrumental record and establish a probability density function for various magnitudes and frequencies of events, such as peak floods.

Milly et al. (2008) however identify anthropogenic disturbances to drainage basins, channels, floodplains, and watsersheds as having effectively destroyed to stationarity concept at the local scale, while anthropogenic climate change has changed the concept at the global scale by altering long term precipitation patterns.

In fact, the authors question whether stationarity ever existed in observed systems, due to land-use changes that have been in place for hundreds of years and which have shown severe effects on the fluvial systems. The picture at left is from Providence Canyon, GA, and shows around 150 m of erosion that occured post 1850 due to poor agricultural processes. Clearly, humans can and have had a strong impact on natural systems. All this has considerable impact on planning and policy-making, which are founded on stationarity models for prediction of flood frequency and water availability.

How does this effect sedimentological facies models? Fluvial facies models are predicated upon the concept that the river system is striving to achieve some equilibrium state, with minor perturbations from the mean being accommodated within the system via feed-back loops and channel evolution. Thus, the very concept of the meandering, braided, and anastomosed river channel planform, which (unfortunately) are the basis for our sedimentological facies models, have the concept of stationarity built-in.

If natural systems, observed at the geomorphic scale, behave in a non-stationary way, then how appropriate are these models for developing interpretations at the stratigraphic scale? In some ways, we should expect the preserved record of fluvial processes to represent only non-stationary systems, since the preservation itself implies the system has been perturbed (by subsidence, or increased sedimentation) beyond the capacity of the channel-system to transport its load. Maybe our facies concepts have given us conceptual models that have made us interpret processes in a completely unrealistic fashion?

Time to step up, Candidates

I just got one of them there "automated e-mails" through the tubes from the ScienceDebate 2008 folks. Seems like they have set a date for the debate (April 18), a place (Philadelphia), and have invited the current batch of candidates, who of course have yet to respond. As a reminder, the Science Debate 2008 crowd are trying to organize a debate for the candidates focused on issues of science and technology in America. This is something we desperately need, given the fact that our current pres. is a barely literate baboon who has refused to allow stem cell funding, believes in an all-father sky deity, and denies evolution. IF you haven’t signed up yet, go to ScienceDebate2008.com immediately and GET WITH THE PROGRAM!

As I said above, the various camps haven’t yet responded, apparently. Hopefully they'll get on and agree; this ain't no small time debate. It has considerable names, including Nobel laureates and leaders of the scientific communities, large national science societies, and many of the major research universities in the country. Can you imagine Huckabee in this things? Or how about good ol' McCain, trying to walk a tightrope between his various camps, all the while hoping to win over the dumbasses in the Bible Belt. We have a word for that: rad.

Rad as hell.

Darwin Day

Or rather, the first Darwin Day of the year; we get another D-Day on Nov. 24, commemorating the publication of easily the greatest scientific work in the world, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. On a related note, everybody should start planning enormous celebrations for NEXT year’s Darwin Year, when it’ll be his 200th Birthday, the 150th anniversary of the publication of The Origin, AND the International Year of the Earth.

Aside from the obvious implications of Darwin’s work for biology and ecology, I think it’s important to keep in mind Darwin’s influence on the creation of coherent methodologies for historical sciences. By this, I mean the ability for people to recognize that the objects and phenomena we experience and observe in the study of nature have a history, and fit into the larger narrative of natural processes. It is this theoretical framework that makes the natural sciences work, distinguishes them from the physical sciences, and gave us such wonders as biology, ecology, and GEOLOGY!

So, Happy Darwin Day, folks! Punch a creationist in celebration!

Milankovitch Cycles and Stratigraphy

Part of my research deals with the controls on sedimentation, and how stratigraphic packages of rock can be used to reconstruct patterns of erosion, sediment transport, and deposition. This area of sedimentological research has been going on for quite some time, of course, with lots of different workers producing lots of data (and interpretations) that seem to point in many different directions. One of the frameworks employed has been the interpretation of repeatable packages of sedimentary rocks (i.e., stratigraphic cycles) as having been caused by Milankovitch cycles in the climate. Wikipedia has a pretty good summary of Milankovitch cycles at: http://en.wikipedia.org/wiki/Milankovitch_cycles.

Milankovitch cycles attempt to explain how variations in the orientation and orbital pattern of the Earth result in changes in the amount of incoming solar radiation (insolation). The original work (Milankovitch, 1941; translated in 1969) uses this theoretical framework to explain the cyclicity observed in glacial-interglacial periods (the Ice Ages). That’s all well and good, and I think it holds up pretty well when used to explain the past few hundred thousand years of ice dynamics, since the mechanism (insolation changes) can be reasonably hypothesized to strongly effect ice volumes. What I’ve always had a problem with seems to be the desire to extend the Milankovitch cycle into the stratigraphic record where we KNOW that there were no large scale ice sheets (The Eocene, or the Cretaceous, for example).

Finally, what are the actual impacts in a SEDIMENTOLOGICAL sense that these Milankovitch cycles would be expected to have? How would they modulate erosion or transport, and what would their impact be on the rock record? So far, I haven’t found a Milankovitch-supporter who can adequately provide me with an answer.

Coal and Creationism

Not too long ago, I ran across a creationist argument that I found particularly galling. Briefly, some Creationists have been running around telling folks that some coals, particularly those from the western U.S., have been able to be radiocarbon dated. These coals, (most from the Bighorn Basin in WY) were deposited in the Paleocene-Eocene, ~65-50 Million years ago (Mya). Coal deposits are formed by the accumulation of biomass (often plants) and its subsequent burial and compaction. In the case of the Bighorn Basin coals, these were deposited in extensive swamps that persisted for some time.

The Creationists’ point is that GEOLOGISTS say these deposits are many millions of years old, BUT if they can be radiocarbon dated, they must have 14C (carbon’s radio-isotope). 14C has a half-life of ~50-60,000 years (for more info on radiocarbon dating, I suggest going to http://www.c14dating.com/); so, to the Creationists this PROVES that geologists are morons and a magic man in the sky made everything.

Like everything Creationists say or think or believe, they have got this one all wrong. It is true that some coals do have some 14C in them, but the ORIGIN of that 14C is not necessarily related to the time of deposition for that coal. In other words, that 14C has been made in place (in situ in the science parlance) within the coal, a longtime AFTER its burial and formation.
A paper by David C. Lowe (1989, Radiocarbon v. 31, n. 2, p. 117-120: a .pdf can be found at http://digitalcommons.library.arizona.edu/index.php/objectviewer?o=http://radiocarbon.library.arizona.edu/Volume31/Number2/azu_radiocarbon_v31_n2_117_120_v.pdf) was the first (to my knowledge) paper to raise this question, and provide a plausible explanation for the discrepancy. Lowe shows how bacteria and fungi living in the coal substrate can degrade lignite as part of their own biological activity; where there is life, there is radioactive carbon being formed. Lowe shows how formation and deposition of just 0.1% by weight of modern 14C could produce a date of 45,000 years. Additionally, Lowe mentions how the decay of uranium/thorium in the coal could also lead to the production of radium, which in its decay could produce 14C.

So, once again, the whole Creationist argument is a tempest in a teacup; scientists knew about the finite 14C age dates derived from older coals, and have subsequently explained their occurrence through a very parsimonious mechanism. Instead of having to throw out the whole body of geological observations, theory, and knowledge we’ve accumulated over the past two hundred years, we were able to provide conclusive evidence for how old coals could exhibit young dates.

The really ridiculous thing is how intellectually dishonest these Creationists are. First and foremost, whichever bible-thumping troglodyte first put forward this “evidence” for creationism MUST have run across Lowe (1989). So either they didn’t bother to actually READ the paper (where the young age is explained as an artifact of modern processes) or they IGNORED that part and tried to manufacture a controversy.

Additionally, the entire Creationist argument hinges on the ACCEPTANCE of radiocarbon dating methods, which still showed the carbon dates to be 45000 years. That’s a bit older than 6000 years, fellas. On one hand, these people will tell you that radiometric dating techniques are all nonsense. Then, on the other hand, they’ll bring up this little gem, and try and tell you how the radiocarbon dates show coals are much younger. You can’t have it both ways, folks.

Immense submarine debris-flow deposit

A particular interest (professional and otherwise…whatever that means) of mine is flow hydrodynamics. That is to say, how does sediment get transported across the surface of the earth, and what processes control the subsequent deposition of sediments. A recent paper by Talling et al. (2007, Nature v. 450, Nov. 22) is a prime example of how absolutely mind-boggling some of the processes are.

Talling et al. (2007) report on an interpreted submarine debris flow deposit, approximately 1500 km offshore of northern Africa. For those not enamored of the SI, 1500 km is about 930 miles, so you’d want to pack a lunch if you were travelling that far. Anyway, this deposit represents the longest run-out flow ever described on Earth. Neat, huh!?!

What’s really interesting, however, is the interpretation of the origin of this deposit. A submarine landslide, 1500 km shoreward of the eventual deposit, probably produced a kind of sediment-gravity flow called a turbidity current. These turbidity currents are flows that are turbulently supported (ergo the name…), meaning that the motion of the sediment-water mixture keeps the whole flow in suspension. Because of the density of the flow, it hugs the bottom of the seafloor, and moves down-gradient under its own weight. These flows are commonly very erosive, and can travel long distances. Talling et al. (2007) make the interpretation that a turbidity current travelled most of the 1500 km, but as it decelerated, it transformed itself into a debris flow. Debris flows are NOT turbulently supported; rather, they exhibit what’s called laminar flow (so NO turbulence in the flow). This transformation of the turbidity current is what resulted in a debris flow, which was rapidly deposited as a many-meter thick bed 1500 km from the source of the sediment.

An impressive paper, detailing the inherent complexity in unraveling the sedimentological record. And this is just a single event that happened only a couple hundred thousand years ago; now think about strata, many millions of years ago, divorced from their geographic context (in a fold-belt, for instance). What a great challenge!

Science Debate 2008

I'm a little tired of a bunch of scientific illiterates running around, censoring or ignoring the findings of workers in a variety of fields, and deciding policy without having to justify their often ridiculous positions (i.e., Bush and his creationism, climate-change deniers, etc).

Which is why it's so exciting to see a real groundswell of support for the SCIENCE DEBATE 2008. If you havn't heard of it, go to http://www.sciencedebate2008.com/ and sign on RIGHT NOW.