Tuesday, August 30, 2011

Stuff I should know: ichnofossils, palaeosols, calcretes, and the dolomite problem.

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I'm an economic geologist and sedimentologist by training. I search valuble minerals. But guess what keeps my mind going around and around? Issues that, at first hand, have nothing to do with mineral wealth. Today, another day in another open pit mine, and I am longing to be an expert in trace fossils (ichnofossils), soil science and palaeosols, calcretes and palustrine carbonates, diagenetic concretions, and the dolomite problem. And you ask, do they have something to do with mineral exploration and resources?

Well - yes. They do. 

Am especially puzzled by the over-whelming amount of what I interprete to be trace fossils of some kind. Though I am no palaeontologist, especially no ichnologist (is that the right word even?). I should take some palaeontologist and soils scientist to the mines. They'd be amazed. Well, I am. 

:-)

P.S. If you can recommend some superb trace fossils for dummies articles or books focusing on fluvial-limnic-lacustrine-palustrine-something depositional environments - let me know.

7 comments :

Eric said...

Trace fossils are the best...almost as much fun as hydrodynamics! The literature is, sadly, somewhat daunting, and also seems to be missing a solid "Atlas" or picture book that really nail down the ID of traces for a non-specialist.

However, if you're looking for some good overviews and references, there are a couple of pretty handy volumes available.

Dolf Seilacher, who is a famous ichnologist, has a pretty good and fairly recent volume out called, simply enough, "Trace Fossil Analysis". It's published by Springer, and has some pretty good overview chapters on invertebrate ecology and behavior as it relates to trace formation. Of course, ol' Dolf is a little TOO in love with the ichnofacies idea for my tastes, but he IS one of the Masters, so it's still a good volume.

George Pemberton at the University of Alberta has done some seriously kick-ass work in linking trace fossils and sedimentology. He's got a Ichnology Research Group website that offers some good links (http://research.eas.ualberta.ca/ichnology/index.html), and searching for publications under his (or any of the other IRG members) names is a good place to start. ALSO, if you ever have the chance, George teaches a really awesome Trace Fossil Short Course at AAPG meetings every year.

As for NON-marine trace fossils, that literature is a little less developed; one of the big names there is Steve Hasiotis (who did put out a book, "Continental Trace Fossils", that does have some good pictures in it). Luis Buatois at the University of Saskatchewan is another big name in fluvial and lacustrine traces assemblages.

If you get some good pictures of traces, you should put them up on your blog! No guarantee that they'll get ID'd, but they're always fun to look at! Good luck!

Anonymous said...

I think Eric has some good suggestions. To my knowledge, there is some controversy over the methods and interpretations of Pemberton and his research group. Environmental interpretations based on a single (or small set of traces) can be a dangerous game. That being said, however, the "Pembertonians" have created what I think is the best "atlas" of ichnology that I have been able to find. It's called "Applied Ichnology," edited by James MacEachern, Kerrie Bann, Murray Gingras, and George Pemberton. It is a 390 page set of notes from an SEPM short course. Again, to my knowledge, some people take issue with their confidence in their interpretations, so tread carefully. I would also suggest a paper by Tony Ekdale 1988 called "Pitfalls of Paleobathymetric Interpretations Based on Trace Fossil Assemblages" to get another opinion on such interpretations.

It sounds to me like you may be most interested in a set of trace fossils that are commonly associated with the teredolites or glossifungites ichnofacies.

Seilacher is a must read. He is the grand-daddy of ichnology (yes, that is the correct word!).

Lost Geologist said...

Thanks a lot for your comments so far! I'll be looking for those publications. From what I can tell at the moment is that the traces look a lot like roots to me. Considering the environments (changing between fluvial, lacustrine to limnic) it would not be odd - but..I don't know. Some roundish to oval or lensoid tubes are traceable downward for almost 3 to 4 meters (usually only half a meter though) with diameters between 1 to 4 cm. Never breanching upward, always downward or horizontally, sometimes into several directions at once. They terminate abrubtly, sometimes getting thinner towards the end or just having a roundish end. I can find no thin or tiny "rootlets" but the rock (volcanic ash or glas tuffs partially altered to bentonite) is not really suitable for preserving those. Infilled with sediment, carbonate precipates or clay. Oh, am working in the Miocene.

In another location I saw what I think are bioturbations by feeding organisms within the sediment or burrows. Also branching downward and a lot of times horizontally.

I'll be working on some fotos...

AerialGeologist said...

I'm taking a graduate-level sedimentology and stratigraphy class, so I feel your pain with the ichnofossils and ichnofacies.

Great blog!

Block Rogger said...

I'm surprised no one spoke up about the study of palaeosols (palaeopedology)!!! Well... not too surprised, since it's not one of the major fields of study since it's can get very difficult if you don't have a good basis.

I would argue that fellow by the name of Gregory J. Retallack is to paleosols as Folk or Dunham are to Sedimentary rock classification!

(You can find Dr. Retallack's site here --> http://pages.uoregon.edu/dogsci/doku.php?id=directory/faculty/greg/about)

Don't get me wrong, he's not the single greatest paleopedologist, but he has fundamental articles and a few textbooks that can get an Igneous/Metamorphic Geologist up to speed on paleosols.


I have a soft spot in my heart for palaeosols. Over this last summer through now, I've been working on an undergraduate senior project concerning the engineering properties of paleosol(response to wetting/drying, Atterberg Limits, etc) with those a geologist would classically examine (such as lithology, clay minerals, etc...).

Anywho, as for a good place to start with studying palaesols!

A condense and concise paper Retallack published that can get anyone who has done a little bit of field geology to be able to generally identify a paleosol based on some stratigraphy (horizons), structures (peds, cutans) and fossils (root traces)... granted compaction hasn't obliterated everything.

Retallack, G.J., 1988a. Field recognition of paleosols. In, Reinhardt, J. and Sigleo, W.R. (editors), Paleosols and weathering through geologic time: principles and applications. Special Paper of the Geological Society of America, 216, 1-20.


Retallack has a (few) textbooks out as well. Here's an "intro" book to the study of paleosols:

Retallack, G.J. 2001. Soils of the Past: an Introduction to Paleopedology. Second Edition, Blackwell, Oxford, 600 p.


Finally, a book that I've not been able to find for my studies (though I would do Geostatistics over again ten times if it would get me this book):

Retallack, G.J. 1997. A colour guide to paleosols. John Wiley and Sons, Chichester, 175 p.


I apologize if this appears disorganized. I just joined the blog after stumbling on your page... and being up for around 36 hours working on Sedimentary Petrography and Mineralogy! Of which I have tests in both early next week!

I do hope my suggestion helps you along in your journeys. Enjoy!

Lost Geologist said...

Your suggestions do come in handy! Thanks a lot!

I've already come across Retallack but some of his books or papers are hard to come by from my location. Few universities here have online access to the popular american geological journals. Neither are his books widely available here. My PhD supervisor though has a copy of a "A colour guide to paleosols" which is a cool book. I'd love to have the other one though which I can't seem to find.

The '88 special publication is also still out of my reach here. A shame but that's how the world is.

Currently I am deep into dolomite formation in soils, lakes and groundwater and calcrete development. The field is vast...fascinating but almost astronomically vast.

Block Rogger said...

Oh calcretes, or as one of my professors calls them: Killer Caliche due to outcrops he has studied from the Pennsylvanian having so much calcretes that it is almost like walking on marbles!

You may be able to find Retallacks text book on Amazon, the intro to paleopedology one.... And you're pretty lucky! I have been trying to find the colour guide for awhile! But I do agree, paleosols are a big field. My project has merely made me scratch the surface of it, too.