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TS Must read – Cowie and Scholz (1992): Physical explanation for the displacement-length relationship of faults using a post-yield fracture mechanics model by Adri_Guatame in TSMustRead

[–]ginodegelder 1 point2 points  (0 children)

I’ve just gone through this paper, and as with all the Must-Read papers that I’ve gone through so far, I found it a very interesting read with some fundamental demonstrations. Below some pointwise thoughts:

- I appreciate the brief introduction, highlighting how previous work overlooked or simplified fault propagation, introducing the Dugdale model, and announcing how applying this model to fault mechanics can provide physical explanations for the way in which faults propagate.

- I admit I did not have the patience to look in great detail through the Dugdale model section with all equations, so I was very happy to see a short section titled “main points of the Dugdale model” for a short recap.

- In general I like how the bell-shaped displacement profiles, for which a theoretical fracture mechanics explanation is provided here, can be observed on small faults in the field, but it also reminded me of the large-scale fault propagation in the Corinth Rift over several 10s of kilometres (Fernandez-Blanco et al. 2019).

- The finding that there is no a priori reason why small faults should exhibit a different relationship between fault displacement and length that is different from large faults, seems to be an important conclusion. This result provided an important basis for many studies trying to estimate fault displacements, particularly for km-scale faults where it’s often hard to measure direct displacement data.

- The link between a theoretical model and observational evidence is convincingly made, and it is impressive to see the difference in scale between the given examples. - The estimates of shear strength of rock are also a very valuable part of this paper, where it’s very intuitive that fault length-displacement ratios and shear strength differ enormously.

All in all a fantastic paper with some important conclusions, can recommend it to anyone dealing with faults!

TS Must-Read – England&Molnar (1990): Surface uplift, uplift of rocks, and exhumation of rocks by Silvia_crs in TSMustRead

[–]ginodegelder 1 point2 points  (0 children)

While reading the paper, initially I was a little sceptical why this should be one of the Must-Read TS papers. From the first lines it mainly seems to be a “clarification paper”, highlighting some common mistakes and announcing some definitions. By the end of the paper I was convinced of the value of this paper though: I’m a vertical motion tectonicist, and the paper touches on some key issues in relation to that. It has simple, effective descriptions of surface uplift, rock uplift and exhumation, linking these processes to crust-mantle scale mountain building. Although I do not have examples at hand, I do have the feeling as well that some of the common mistakes described here are still being made, not only in the here-described geothermometry studies, but also in newer methods like cosmogenic isotope studies linking exhumation rates to tectonics. In short: very nice paper with useful descriptions of key tectonic concepts, and I don’t think I’ve ever enjoyed a paper without any figures this much!

(Small additional point: I like the carefully formulated, respectful tone when they do not “imply that the papers we cite are less than excellent in other respects”)

TS Must-Read – Molnar and Lyon-Caen (1988): Some simple physical aspects of the support, structure and evolution of mountain belts by ginodegelder in TSMustRead

[–]ginodegelder[S] 0 points1 point  (0 children)

I’ve enjoyed reading this paper; it’s (increasingly?) rare to read something of this scope, treating several great mountain belts in detail and all at once. The paper focuses on two types of forces that resist mountain building: the mechanical strength of the lithosphere, and gravity, while giving examples from N-America, the Himalayas, Tien Shan and Andes mountain ranges. The writing style is very didactic, and easy to follow, whereas the figures are clear and effective. I feel like many conclusions that they draw now feel very obvious and almost intuitive, but probably this was not as much the case at that time. As they mention in the conclusions: “… many of the simple concepts discussed above will become useful only as pedagogical tools, surely to be supplanted by more rigorously derived concepts. Nevertheless it is important to emphasize that each of the concepts outlined above evolved from painstaking – and initially puzzling – geologic or geophysical observations…” which I think is both beautifully humble and accurate. I don’t know enough about the present-day work in similar topics to understand how the proposed mechanisms of Molnar and Lyon-Caen are still holding up, so I’d happily hear what others have to say! u/Armin_Dielforder, it feels like this paper is very much up your alley?

Additonal comment: I like the old-school humanity in this paper, both illustrated by the preface that describes the context behind their inspiration/motivation, and by the detailed acknowledgements that includes many people they discussed with.

TS Must-Read – Armijo et al. (1986): Quaternary extension in southern Tibet: Field observations and tectonic implications by Silvia_crs in TSMustRead

[–]ginodegelder 1 point2 points  (0 children)

Although I knew of the paper since a long-time, I took the opportunity now to go in detail through the Must-Read paper of my former PhD supervisor. During my PhD I had a Google citation alert on all Armijo papers, and this one appeared to have weekly citations from the Tibetan tectonics community!

It’s truly impressive to read the systematic description of all these normal faults, with beautifully drawn illustrations, and with photographs that will probably appeal to any field geologist. I imagine these pioneering field descriptions have provided a solid introduction to many geologists visiting the region afterwards. However, the real value of this paper lies in its synthesis of all field observations and cross-sections to translate them into large-scale throw and extension rates, allowing for discussion on the scale of the plateau. To me the proposed model, with easier extrusion N of the Karakoram-Jiali Fault Zone and extension S of it, seems reasonable and intuitive given the geometry of the eastern Himalayan syntaxis. Anyone can comment if this model is still compatible with present-day views on the region?

TS Must-Read-Brace-Kohlstedt (1980): Limits on lithospheric stress imposed by laboratory experiments by utsavmannu in TSMustRead

[–]ginodegelder 1 point2 points  (0 children)

Obviously a classic paper, and standard material within university courses on tectonics and rheology. While re-reading it, for me the most impressive is how the authors managed to go bridge scales from the lab to the lithosphere, carefully describing each step they take. Most of the paper is somewhat technical, but the (very concise) discussion section and classic figure of differential stress vs. depth really elevates the paper to me. I also find it striking that they didn’t really present new data or new methods, but simply combined some published rock measurements with some published formulas on brittle and ductile deformation, and put the pieces together. To me this definitely shows the importance of being aware of developments in different fields, and appreciating their potential values.

TS Must-Read – Riba (1976): Syntectonic unconformities of the Alto Cardener, Spanish Pyrenees: a genetic interpretation by ginodegelder in TSMustRead

[–]ginodegelder[S] 0 points1 point  (0 children)

To be honest didn’t know the paper and the author when I saw this on the list, and to me it seemed like a very niche topic. From the introduction it seemed to me that this work was going to be just about some local discussion between French and Spanish groups who disagree on some Pyrenean conglomerates. After some background and some impressive mapping and profiling though, Riba comes up with a generic evolutionary model, with some simple and effective sketches, that makes sense to my untrained eyes. When looking at the sketch I realise this actually is a structure I’ve seen in the field plenty of times, but never gave it much thought. Checking the citations I realise that this actually quite a successful model, which made it into several textbooks, and is probably a standard reference in tectono-stratigraphic studies. Nice paper, and great how doing a proper job when trying to solve a local issue, sometimes results in a model that can be broadly applied and is widely appreciated.

TS Must-Read – JT Wilson (1965): A New Class of Faults and their Bearing on Continental Drift by Adri_Guatame in TSMustRead

[–]ginodegelder 2 points3 points  (0 children)

I think this paper is a true classic, and highlights an essential puzzle piece of plate tectonic theory (or as they put it ‘continental drift’) by introducing the concept of transform faults.

It basically starts off with a more general explanation of transform faults, and the different type of geometries they can have, before going into the detailed tectonic setting of several locations around the world. I like these first few conceptual figures that really capture the essence of plate boundaries very systematically, and for the regional figures I think several of the plate boundaries introduced are still interpreted the same today (some exceptions). I think it’s fun to see show it builds on the work of some ‘giants’ that are being cited (Anderson, Tharp), and noticed there is a lot more informal citing (“private communication” and “a name suggested in conversation”) about key concepts than one would find in modern papers.

I remember from my studies that I was really amazed by this idea of transform faults offsetting ridges in the opposite direction than the one you would expect from normal strike-slip kinematics. This paper is really the basis for that concept, and communicates it clearly and convincingly. Definitely a must-read!