Dear Gaël,

thanks for attracting attention to this point. Sorry, at first glance no, I do not have such case in my memory. I I will keep this reference in mind and inform you in case I find something.

Tell me, what is your position in Birmingham.

Amicalement

Jacques

In carbonate rocks, "vertical stylolites" found within an overtrust belt are an example of horizontal shortening other than by trust faults.

See for example:

- https://www.researchgate.net/publication/229892109_Deposition_and_diagenesis_of_carbonate_conglomerates_in_the_Kremenara_anticline_Albania_A_paragenetic_time_marker_in_the_Albanian_foreland_fold-and-thrust_belt (and in particular Figure 9 therein).

- http://www.rmag.org/assets/FallSymposium/FallSymposium2016/Longman_Abstract.pdf

In these cases, of course, care must be taken to distinguish between stylolites at high angle with bedding at crestal positions (evidence of horizontal shortening by pressure solution) from the rarer stylolites at high angle with bedding in vertical limbs (evidence of normal vertically directed pressure solution after strong folding).

Article Deposition and diagenesis of carbonate conglomerates in the ...

Considering that clay contains a lot of water, and that clay can loose water and compact to some 20% of its original volume (this is an 80% compaction!), I will not be surprised if anybody finds clay-rich sediments that show some foliage and evidence of compaction at a high angle to the original bedding surfaces.

Hello all, 

Many thanks for your answers!

Roberto, I didn't know these studies, I'll read it. Thanks for the references and your opinion. Do you think we could consider such internal compaction in other types of sediments, as evaporates for example? I guess it's possible that a rock made of gypsum, marls and calcareous clay underwent this kind of deformation, isn't it?

Jacques, I'm working as a post-doc researcher at the University of Birmingham in the project of the Galicia margin (http://www.birmingham.ac.uk/research/activity/geosystems/projects/west-galicia-rifted-margin.aspx) with Prof Tim Reston. I enjoy it a lot: great team, amazing data, fascinating problematics. I have one more year here before the next. 

Best regards and thanks again!

Amicalement

Honestly I was not aware that the role of lateral compaction within sedimentary layers that high in structural shortening, for shale dominated sections it does make sense but not for the more sandy or carbonaceous stuff that commonly undergoing brittle deformation. In my experiences in the fold-thrust belts of West Timor, Lengguru of West Papua, Misool Island, Lariang of West Sulawesi or Matindok of East Sulawesi, the roles of the sedimentary compaction may have been less since most of the stratigraphy are dominated by brittle rocks.  

Hello Gaël,

Sediment compaction with associated fluid expulsion from deep marine colloidal shales is another example you may want to consider.  In this case the sediment volume reduction occurs in all three dimensions and creates polygonal faults.  The structures were first observed on 2D seismic but their scale and pattern was only recognised using 3D marine seismic data. These km scale features are now also recognised at outcrop in large fresh surface exposures e.g. brick clay quarries in Belgium

See Das, P.K., 2006. Seismic expression of layer bound polygonal fault system: An example from Bass Basin of Australia. In Proceedings of the 6th International Conference & Exposition on Petroleum Geophysics, Kolkata (pp. 606-614).. and references to Cartwright therein.

http://www.spgindia.org/conference/6thconf_kolkata06/25.pdf

Wow, more answers, thanks very much that's nice. 

Douwe, I need more references regarding this process than the current one I have, I'll check these names, thank you. 

Kartono, lateral compaction within brittle sediments is the point indeed. For instance, where I would expect folds and reverse faults in the brittle sedimentary layers of a down-slope domain subject to gravity gliding, I surprisingly observe only minor clues of compression (slight undulations of the layers). Lateral compaction could be a potential explanation. As the gravity gliding is not very strong, I guess compression could have been accommodated this way. 

Philip, you're right we very well observe polygonal faults on the 3D seismic dataset I'm currently working on. Do you think lateral compaction within sediments during a shortening event is related to the same process than polygonal faults then?

Hello Gaël,

Interesting question.  Form my observation of the 3D seismic, each individual polygon has a concave top and a convex base diagnostic of sediment volume reduction by fluid expulsion. Deep marine colliodal sediments are the ultimate in gloopy muds with up to 98% water by volume at the sea bed. Consequently these strata are optimal layers for slickensliding and slope failure.  In my study area of the Eocene in the Rockall Trough we observed an AVO anomaly which we called the egg. Detailed inspection of the 3D data at this location showed classic slope failure an arcuate upslope fracture and down slope compression, hence the egg shape.

These gloopy sediments may be deposited rapidly from airborne tuffs.  If so they provide an instant cap rock to the sediments below,  Consequent pressure build up from below and seal failure during dewatering of the muds allows for fracturing and vertical transmission of fluids.

So where does all the escaped fluid go?  Have a look at the strata above and check for any sand injection anomalies and soft sediment diapirs in the overburden.

Lateral compaction of sediments may indeed be a significant process during horizontal thrusting and shortening of sediments in a range of settings. We see structures attributable to lateral compaction in sediments around the Dead Sea Basin - check out the attached publication (especially section 7.7.3.) that is currently  'in press' in Sedimentary Geology.

Thanks

Ian Alsop

Hello Gaël,

Layer-parallel compaction (LPC) or tectonic compaction is a significant component of shortening. In couple of papers we quantified LPC in sand models it to "lithology", basal friction, stratigraphic location, and amount of bulk shortening. This is easy to quantify in models where the initial dimensions and boundary conditions are better known. We have also compared LPC in models to that in Pyrenees where we measured 16-23% depending in different sections. If you are interested, send me your email address and I will send the PDF of those articles.

Cheers,

Hemin

Hello

layer-parallel shortening is known process from many orogenic belts such as Laramide and Appalach. this is an stage of lateral compaction of rock beds that can be lead to folding or not. In an multi-layer sequence with competency contrast, layer parallel shortening will result in folding of competent layer, but when the competency contrast is low, this process can not produce significant folding, but there are some structures that accommodate this shortening, for example stylolite perpendicular to bedding in carbonate rocks. strain analysis can help us to determine aspects of layer-parallel shortening. there are many papers as well as books that consider various points of layer parallel shortening.

Hello all,

I want to thank everybody for your clever answers. Lateral compaction is definitely more common than I expected and you all provided a very nice list of references/examples/papers. No excuses now to not know this process!

I have to say as well that I was a bit sceptical about the use of Research Gate to ask questions, but it works and it is actually very pleasant to get answers from around the world. 

So many thanks again to all!

Cheers!

Gaël

Hello all

I have been following the interesting comments and insights about this process.

Sorry to add another question instead of an answer, butI wonder if this kind of mechanism applies mainly for sediments of marine basins or it could be also important in foreland basins filled  by clastic Cenozoic sediments without significant subsidence?

Many thanks in advance

Hi Gaël,

We calculate the amount of heterogeneous lateral compaction up through a deformed MTD in the attached paper on fold and thrust systems in mass transport deposits.. The variation in lateral compaction is ~ 10% - but of course this is just the variation and not necessarily the total amount. We also have a discussion as to why the amount of lateral compaction varies between nature and sand box experiments.

Hope this helps.

Thanks

Ian

Article Fold and thrust systems in Mass Transport Deposits