Thursday 19 February 2009

Software for stereographic projection. Stereonet

It is never a bad idea to refresh our memory about the software available online for free (freeware, GNU licenses, etc) in our profession. I have thought that it would be a good idea to dedicate some posts in our website to that topic. So we start today with...:

Software for stereographic projection

There are several pieces of software that you'd like to check out for that purposes. Basically all of them do the same job: project, display, analise and modify orientation data on a stereonet. More in detail, you can project in equal area, or you can choose to project in equeal projection. You can choose the hemisphere (high or low), you can choose to work with a pole or with a plane projection... And of course, rose diagramas, changes in directions for palaeocurrents, etc.

As we know, that is a basic procedure in structural geology, and therefore, my first recommendation is to masterise the stereonet by hand, using (oh, yes!) drafting paper, a pencil and a paper stereonet (And a flat pin, of course*). It is not difficult at all, and it can be fun. I loved it during my degree.

OpenStereo: Reviewed in one of my articles here: So far, I am really impressed by it!

(by Rick Allmendinger): In his website you can download not only Stereonet, but a fair amount of other useful tools. For non commercial purposes. It is my favourite one, as it works very well, and I haven't found any bugs in it. Go here:

StereoNett: German software produced in the University of Bochum. This is the old version, but perhaps it can be still useful in some old machine... anyway the new version is Stereo32, that you find in this article, below :-) :

Stereo32: Same software than the one mention above, but rewritten and designed for Windows 2000, XP and Vista:

If you know more software, please mention it in the comments of this article and I will add it to the list.

Soon, more software...

* That reminds me my lessons of "Structural Geology" in the second year of my degree. I studied Geology in Spain, where the basic degrees was, and still is, 5 years. Two of my classmates had exactly the same results during a test, and the lecturer knew perfectly who copied from who: one of them presented his drafting paper without a hole in the center for the pin!!

Sunday 15 February 2009

Congress: Salt tectonics, sediments and prospectivity

I joined the Geo-Tectonic mail list ( several years ago and, in my opinion, one of its most useful features is the contribution of news about congresses and meetings related with structural geology and adjacent areas (of knowledge!).

In this case, Ian Alsop has sent the information related with a very interesting congress on salt tectonics, titled "Salt tectonics, sediments and prospectivity", due to be celebrated in The Geological Society next January. Not a long way, after all!

Salt Tectonics, Sediments and Prospectivity
International conference sponsored by The Geological Society, Petroleum Group and SEPM
January 20-21st 2010
The Geological Society, Burlington House, Picadilly, London.
This two day international conference aims to bring together academic and industrial geoscientists to review recent advances in our understanding of halokinetic processes and to explore the links between salt tectonics and sediments. Encouraging the interaction between structural geologists and sedimentologists is a desired outcome. Contributions are invited that address key technical issues that include:
  • How does salt tectonics manifest itself in sedimentary basins?
  • Comparisons of subsidence rates between tectonically generated basins and salt withdrawal minibasins?
  • Prediction of reservoir presence and quality and new generation facies models
  • What traps hydrocarbons in salt flank structures – salt side seal or sand pinch out?
  • Salt as a trapping and breaching mechanism – are salt welds sealing or leaky?
  • To what extent does salt suppress hydrocarbon maturation?
  • What role does salt play in sandstone diagenesis?
  • Sub-salt imaging – how far have we come, new approaches / techniques to make further improvements?
  • Papers are welcomed from a wide range of sub-disciplines including, earth surface processes and landforms, outcrop or mining data, subsurface seismic, well and core data, potential fields and physical and numerical modelling.
More information, abstract deadlines and posters to download etc may be found at our web page:
Stuart Archer ( University of Aberdeen)
Ian Alsop (University of Aberdeen)
Adrian Hartley (University of Aberdeen)
Neil Grant (ConocoPhillips)
Richard Hodgkinson (Bowleven)

Tuesday 3 February 2009

Trishear deformation: the yet to bloom concept


We are used to draw fault related folds using graphic methods involving kink folding and parallel folding. This methods allow us to get an idea of the folding mechanism ruling some structures, but in general nature is more complicated than that...

Rick Allmendinger, structural geologist from the Department of Earth and Atmospheric Sciences at Cornell University explains it in full in his website :-)

What the heck is "Trishear," anyway?
Eric Erslev (1991) deserves full credit for developing the concept of trishear. During his studies of the Laramide Rocky Mountain foreland in Colorado and Wyoming, he noticed that discrete fault zones within the basement diffuse outward and upward in a triangular zone of deformation in the overlying sedimentary section. He called these triangular zones of deformation "trishear." Trishear provides an alternative to the parallel kink fold description of fault-propagation folding. Unlike the simple kink fold model, trishear can produce footwall synclines, downward steepening dips and thickening and thinning of forelimb strata. Furthermore, trishear provides a richer description of heterogeneous strain distribution at the tips of propagating faults (see the above graphic), which may ultimately prove useful, for example, in studies of fracture distribution and orientation. However, whereas parallel kink fold angular relations can be determined graphically (e.g., Suppe & Medwedeff, 1990), trishear models can only be calculated numerically.
Since 1997, we have been studying trishear extensively at Cornell and have concluded that trishear structures are far more widely distributed than previously recognized. We have written general 2D and pseudo-3D trishear modeling programs which enable us to explore the complete broad range of trishear-associated deformation In these web pages, we give a brief, mostly graphical, introduction to trishear, with the intent of illustrating how it might be used. Be sure to check out the trishear movies!
This material in this site is partly based upon work supported by the National Science Foundation under Grant No. EAR-9814348. Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF). Additional support comes from the Donors to the Petroleum Research Fund of the American Chemical Society. And finally, there is a lot of unsupported stuff in here as well :-)
I think a good understanding of this concept should be a requirement to anyone approaching structural geology in a degree. Unfortunately, it doesn't seem to be a very spread idea yet. So you know... Visit it, play it, learn it!

Monday 2 February 2009

Online sale of the GeoSoc bookshop: February'09

Hopefully you don't read this message too late!

The Geological Society of London, through its bookstore service, offers periodically at a very low price different volumes in an online sale. The volumes belong basically to the Special Publications series, amongst others.

In this occasion the GeolSoc runs the sales from 30 of January to 6th of February of 2009; but don't worry, this sales are repeated every 2-3 months.

This time most of the books are offered at £25 (sales price for the last years, as far as I remember), and having in mind the quality of the titles, this is a real bargain.

Check it out here:

Box Cube Cut

My friend Raik sent me last week this video from YouTube, a very funny presentation that, from a very cinical point of view, shows us the... reality behind software in the Exploration and Production world :) Read carefully the introduction to the video.

Sunday 1 February 2009

Great set of paleogeographic maps

Who doesn't surf the net and find very interesting links that after a couple of days are totally forgotten? Some days ago I found this superb collection of paleogeographic maps in the website of Dr Ron Blakey.

The globes presented in this series show how Earth may have appeared over the last 600 million years (Ma). The global views were prepared from rectangular projections drawn at a resolution of 3000x1500 pixels for each of the 26 time slices (small files of the rectangular maps are also included). Topography was "cloned" from digital elevation maps of modern Earth from the USGS. Colors were adjusted to portray climate and vegetation for the given time and location. The modern Earth was also drawn in this manner using a color pallet derived from satellite images created by ARC Science of Loveland, Colorado. The geologic data was gathered from the references listed below. The completed rectangular images were then wrapped on a sphere and saved as jpg files.

Take a look. They don't only look great, they show great geology. Enjoy it!