Friday 28 January 2011

OpenStereo: an opensource stereographic software

A couple of years ago I wrote an article about stereonet programs. Geologists use this type of programs for stereographic projection and structural geology analysis. It is one of the most powerful tools we have, A few weeks ago, through the comments of this article, I got to know another piece of software which, being at least as good as the well known suites (as far as I have tested it), has the pecualiarity of being open source. I am talking about OpenStereo.
OpenStereo has been released under a GNU General Public License v.3. Which means that I can use it in the office for commercial purposes! (and you too). OpenStereo has been developed at the Instituto de Geociências of the Universidade de São Paulo by Carlos H. Grohmann and Ginaldo A. Campanha. It is developed in Python and it is a cross-platform program. For further technical aspects of this work, please read this abstract presented by the developers in the AGU2010 conference:

This piece of software is truly promising, even though being in a beta phase of development (Version 0.1 Beta). Having that in mind, it is recommended to double check results, of course. A beta is a beta, after all. It is very portable, as it can be copied in an external drive and it will work. Good for having it in you work or study memory stick.
I have been testing it, and so far I haven't found any important weak point. Actually, I can only speak wonders of it, especially of its flexibility with its graphic interface. It supports different datasets at the same time, something very useful when comparing structural features in different zones or provinces for the same project. An imporant difference with other programs is that OpenStereo is very easy to use, and absolutely intuitive
It is possible to export the results under several graphic formats (emf, eps, ps, pdf, png, svg) and the quality of those is highly profesional. Take a look to this two examples I have done quickly. Don't you feel like starting to work with it?
Go on, download it and play with it. Probably this nice piece of software will become your favourite one:

(Thanks to Carlos H. Grohmann for his comment, which lead me to this great piece of work)

Thursday 27 January 2011

Midland Valley's Student Structural Prize Winners 2010

Midland Valley has unveiled the name of the winners of their "Student structural prize" for 2010. Congratulations from!

Post-graduate award:
- 1st prize: Justin Macdonald, from University of Waterloo (Canada).
- 2nd prize: Koen Van Noten, from the Katholieke Universiteit Leuven (Belgium).
- Runner-up: Chao Lei, from the University of Geosciences in Wuhan (China).

Undergraduate award:
- 1st prize: Harry McClelland, from University of Cambridge (England, UK).
- 2nd prize: Rowena Gunn, from the University of Glasgow (Scotland, UK).

Best use of Move:
- José Mescua, from Universidad de Buenos Aires (Argentina).

Remember that the Student structural prize is now open for entries for the current year, 2011!

Penrose conference on "Deformation localization in rocks: new advances"

(From the Geo-Tectonics list, sent by Ian Alsop)

Dear all,
This is an e-mail announcing a Penrose conference on "Deformation localization in rocks: new advances."
The conference will be held this summer from the 27th June to the 2 July 2011 and will be situated in Cadaques within the Cap de Creus peninsula of Catalonia, Spain.
The GSA website on the conference displays registration and application details at
The application deadline is 25th February 2011. Applications should be sent directly to Elena Druguet (e-mail:
Further details (including a pdf flyer) may also be found at

Some of the main anticipated topics include:
Shear zones - new perspectives on geometry, kinematics and mechanics;
Field, numerical and analogue modelling of mesoscopic elements of shear zones;
The role and interaction of fluids, melts and metamorphism in strain localization;
Physical and numerical experiments on strain localization;
Approaches to the study of strain localization in orogens.

Keynote speakers include John Cosgrove, Laurel Goodwin, Scott Johnson, Neil Mancktelow and Cees Passchier.

Best wishes

GAC-MAC 2011 call for abstracts

(From the Geo-Tectonics list, sent by Cees van Staal)

Dear Friends and Colleagues,

The abstract submission deadline for GAC-MAC 2011 Meeting in Ottawa (May 25-27, 2011) has been extended to January 31. If you have not had a chance to submit an abstract yet, we encourage you to consider our special session entitled: "Tectonic history of the Appalachian-Caledonian and related orogens". We have received quite a number of abstracts by the original January 15th deadline (over 20) but let's try to increase that number to demonstrate that Appalachian-Caledonide geology is even more important than most of those other special sessions! If you already submitted an abstract, perhaps forward this message to a colleague who might not have done so.
This multi-disciplinary international session is aimed at all aspects of the geological evolution of the Appalachian-Caledonian and related mountain belts, including but not limited to establishment of Iapetan oceanic basins, terrane provenance, evolution, accretion, and post-assembly translation. We hope to showcase the tremendous progress that has been made in our understanding of the Appalachian-Caledonian orogen in the past 20 years, and also to emphasize the outstanding problems and the ways in which they can be addressed. Both oral and poster contributions are welcome, as is student participation.
For further details and to submit an abstract please visit:


Sandra Barr, Cees van Staal, John Waldron, Chris White and Alex Zagorevski
Session co-chairs

This special session  has an associated 5 day fieldtrip (starting at 8 am on May 28-ending the late afternoon of June 1st):

The defining tectonic elements of Ganderia by: Cees van Staal, Sandra Barr, Les Fyffe, Susan Johnson, Adrian Park, Chris White, Reg Wilson
The fieldtrip will provide a nearly complete transect through the Ganderia microcontinent, New Brunswick Appalachians. This trip will visit all constituent parts of Ganderia relevant to its Late Neoproterozoic to Devonian tectonic history, which include the Penobscot, Salinic and Acadian orogenic cycles. Elements visited comprise the Neoproterozoic to Early Cambrian Brookville and New River terranes (Ganderia basement); the late Early Cambrian to Early Ordovician Penobscot arc/backarc complex, the Middle Ordovician Popelogan arc/Tetagouche backarc and Late Ordovician to Late Silurian Salinic Brunswick subduction complex and associated forearc rocks in northern New Brunswick (with the only known blueschists in the Appalachians), the Silurian Fredericton trough and the Silurian coastal arc and Mascarene backarc. The fieldtrip officially begins (pick-up on the 27th) and ends in Fredericton (drop off late afternoon/evening June 1st), New Brunswick. Participants can also fly to Saint John on the 27th
Cees van Staal on behalf of other session co-chairs and co-fieldtrip leaders

Thursday 20 January 2011

Classic papers in structural geology I

I want to start a series of posts where I will compile abstracts of classic papers in structural geology. These are papers that should be part of the libraries of any structural geologist, and they marked a difference in their time. We are talking about publications from the 80's, 70's, or older, or perhaps younger, that changed the understanding of geology at that time. If possible, I also include a link to a downloadable version of each article*.
Because I am biased by contractional tectonics, please feel free to post in the comments the title of the papers you consider foundational in structural geology.
*Note: I am simply linking a url where you can find each article. I am also pasting here the abstracts, but I am not hosting the articles themselves, so I am not sharing any copyrighted material.

The structural relations of the Cumberland overthrust block are such as would occur if gliding on the thrust plane took place parallel with the bedding along certain shale beds in such a way that the thrust plane followed a lower shale bed for some distance, then sheared diagonally up across the intervening beds to a higher shale, followed that for several miles, and again sheared across the bedding to the surface.
Reasons are given for the belief that subsidiary faults and folds within the block are superficial and do not extend below the thrust plane. This possibility should be borne in mind when exploration of such structures for oil or gas is contemplated.
Study of the Cumberland block throws new light on the broader problems of the nature of folding and faulting in the sedimentary rocks bordering great mountain ranges and on the function of friction in setting limits to the distance through which overthrust blocks can be moved.

Balanced cross sections. Dahlstrom, C.D.A., 1969, Canadian Journal of Earth Sciences, vol. 6, p. 743
Post-depositional concentric deformation produces no significant change in rock volume. Since bed thickness remains constant in concentric thickness remains constant in concentric deformation, the surface area of a bed and its length in a cross-sectional plane must also remain constant. Under these conditions, a simple test of the geometric validity of a cross section is to measure bed lengths at several horizons between reference lines located on the axial planes of major synclines or other areas of no interbed slip. These bed Iengths must be consistent unless a discontinuity, like a decollement, intervene. Consistency or bed length also requires consistency of shortening, whether by folding and (or) faulting, within one cross section and between adjacent cross sections.
The number of possible cross-sectional explanations of a set of data is reduced by the fact that, in a specific geological environment, there is only a limited suite of structures which can exist. This imposes a set of local "ground rules" on interpretation. When these local restrictions are coupled with the geometric restrictions which follow from the law of conservation of volume, it is often possible to produce structural cross sections that have a better-than-normal chance of being right. The concept of consistency of shortening can be extrapolated to a mountain belt as a whole, thereby indicating the necessity for some kind of transfer mechanism wherein waning faults or folds are compensated by waxing en echelon features. These concepts are illustrated diagrammatically and by examples from the Alberta Foothills.

Mountain Belts and the New Global Tectonics. Dewey, J.F. and Bird, J.M., 1970. Journal of Geophysical Research, vol. 75, 14, 2625-2647.
Analysis of the sedimentary, volcanic, structural, and metamorphic chronology in mountain belts, and consideration of the implications of the new global tectonics (plate tectonics), strongly indicate that mountain belts are a consequence of plate evolution. It is proposed that mountain belts develop by the deformation and metamorphism of the sedimentary and volcanic assemblages of Atlantic-type continental margins. These assemblages result from the events associated with the rupture of continents and the expansion of oceans by lithosphere plate generation at oceanic ridges. The earliest assemblages thus developed are volcanic rocks and coarse clastic sediments deposited in fault-bounded troughs on a distending and segmenting continental crust, subsequently split apart and carried away from the ridge on essentially aseismic continental margins. As the continental margins move away from the ridge, nonvolcanic continental shelf and rise assemblages of orthoquartzite-carbonate, and lutite (shelf), and lutite, slump deposits, and turbidites (rise) accumulate. This kind of continental margin is transformed into an orogenic belt in one of two ways. If a trench develops near, or at, the continenal margin to consume lithosphere from the oceanic side, a mountain belt (cordilleran type) grows by dominantly thermal mechanisms related to the rise of calc-alkaline and basaltic magmas. Cordilleran-type mountain belts are characterized by paired metamorphic belts (blueschist on the oceanic side and high temperature on the continental side) and divergent thrusting and synorogenic sediment transport from the high-temperature volcanic axis. If the continental margin collides with an island arc, or with another continent, a collision-type mountain belt develops by dominantly mechanical processes. Where a continent/island arc collision occurs, the resulting mountains will be small (e.g., the Tertiary fold belt of northern New Guinea), and a new trench will develop on the oceanic side of the arc. Where a continent/continent collision occurs, the mountains will be large (e.g., the Himalayas), and the single trench zone of plate consumption is replaced by a wide zone of deformation. Collision-type mountain belts do not have paired metamorphic belts; they are characterized by a single dominant direction of thrusting and synorogenic sediment transport, away from the site of the trench over the underthrust plate. Stratigraphic sequences of mountain belts (geosynclinal sequences) match those asciated with present-day oceans, island arcs, and continental margins.

Thrust systems. Steven E. Boyer, and David Elliott, 1982. AAPG Bulletin; v. 66; no. 9; p. 1196-1230.
Geometric framework; a certain family of lines must exist where thrust surfaces join along branch lines or end at tip lines. The order in which the fault slices form has a marked effect on the geometry of the thrust system. These systems must be identified to understand the provenance of the synorogenic sediments. Part of a thrust belt may be dominated by one particularly large thrust sheet. In front and beneath these dominant sheets, there is a characteristic sequence of thrust systems with a regular pattern to the involvement of basement. New insight into some classic areas Mountain City and Grandfather Mountain windows, in the Southern Appalachians, Jura to the Pennines (in the Western Alps).

End of the first lot :-)

Wednesday 12 January 2011

Fancy a creationist job?

If you are a geologist and you are a creationist, you are a lucky person. Answer in Genesis offer, from time to time, positions for you at their Creationist Museum:

It is a great deal. You only need to forget that you are a REAL SCIENTIST, forget evidences, and believe a text about mythology liks if what it said actually happened.

My point of view about religion is very clear and sound: I am an atheist. And as an atheist and a rational person, I consider science incompatible with any religion. But I also think this is something personal of each of us, and if we don't mix our beliefs with the world of facts and things, it is OK.

The problem is when one finds creationists indoctrinating others with their own beliefs, neglecting evidences and well proven scientific theories and laws. I thought this sort of people where a minority, but not, they are, apparently, growing in number. The most prominent website of this kind is "Answer in Genesis", a nonsense collection of pseudoscience and superstition.

Let's start saying that if you want to work in any of their centres (Like a "Museum of Creationism"), you have to agree with this AiG Statement of Faith, where they basically ask you to politely switch off your brain:

- "The Noachian Flood was a significant geological event and much (but not all) fossiliferous sediment originated at that time."

- "By definition, no apparent, perceived or claimed evidence in any field, including history and chronology, can be valid if it contradicts the scriptural record."

This people don't want just to live in their own faith... They basically want to convert others to their own belief, going backwards in time ignoring everything we know about our little planet. Read that question of a poor tormented couple:

I have a son who is interested in pursuing a career as a geologist / geoscientist. He just finished his first year of college and is seeking God’s will and direction.
We both are concerned that this field is filled with evolutionists and even christians who don’t believe in a literal interprutation of Genesis 1:1.
. . .
—P.L., U.S.

The answer... funny if it wouldn't be so serious:

This answers and other material has been created by geologists, even Ph.D. in geology. Just read any of the following guides:

I have opened the guide about Dover, as I live in London. I can't make any sense of all that, really. We have dated most of our planet. The evidences are crystal clear. We know pretty well our origin, the origin of Earth and the Solar System. The Universe is a big ocean of nothing, and we also know quite well its evolution. Many people independently have reached the same conclusions, after a painful and slow way. What do creationist have in their hands? Two pages in the bible.

Why there are creationists amongst geologist? Where is the point?

Comments are welcomed.

(If you have kids, take them to a proper museum, take them also to an outcrop where they can see how rocks are deformed, how fossils indicate the age of the rocks where they are embedded, and show them the wonders of nature).