Dhouha:

No, it is not a Mud Crack but a weathered feature. You may find this link informative:

https://www.researchgate.net/publication/235623842_Evolution_of_mud-crack_patterns_during_repeated_drying_cycles

Best

Syed 

Article Evolution of mud-crack patterns during repeated drying cycles

Dear Mr. Jafar,

Thank you for the information and thank you for the link & article.

Best regards,

Cordially

Dhouha J.S.

 Dear Dhouha,

I agree with Dr Syed: it does not look as mud cracking, rather as weathering / selective erosion of bedding.

Regards,

Diego E. Angelucci 

Dear Dr. Angelucci

Thank you sir for the confirmation of Dr. Syed's response.

Best regards, 

Sincerly,

Dhouha J.S.

Hi,

I do not see that as a mud-crack at all!

Can we get a larger scale picture?

Cheers.

Michel

KMT:

Martian Mud cracks predominantly display sequentially appearing 3-way joints at 90 degrees matching with those commonly seen in inelastic glaze material of antique porcelain / Glass. In contrast, elastic and homogenous material like a Rock boulder on impact cracks and displays more common 3-way joints at 120 degrees - this is the most common pattern seen in nature with aided or unaided human eye. Goehring et al. experiments (plus see file) would have been more exciting if material of different elasticity were used, because even in 120 degree crack pattern there are small hidden areas with 90 degree joints. Martian "Mud-Cracks" are 3 billion year old (see link) and are too large and in no way suggest shrinkage cracks caused by loss of water ! NASA'S sensational claim needs to be more critically assessed.

http://www.usatoday.com/story/news/nation-now/2017/01/18/check-out-these-possible-martian-mud-cracks/96720726/

Best

Syed 

I'd agree, not mud-cracks but a weathering feature running along bedding and fracture plains. Usually these kind of features are associated with the release of burial-stress (that keeps these features closed) as previously buried sediment get close to being exhumed at the surface. I don't have a reference for this effect (anyone?) but it's very common in outcrop. Good luck, Stan

Thank you everybody for your comments.

Best regards

Dhouha

Good paper, may be helpful.

HANCOCK P. L. 1985. Brittle microtectonics; principles and practice. Journal of Structural Geology 7, 437-457.

Certainly not mud cracks.  Mudcracking normally develops roughly polygonal patterns due to contraction towards central foci.  The feature shown is jointing, in which the long partings going across the picture are bedding joints and the shorter partings at right angles to the bedding are dilation joints.  Indeed these carbonate rocks are not dissimilar to Carboniferous limestones found in northern England - see photo.

The first photo in the field is mud cracking.  The second photo is of Carboniferous limestone pavement showing the pattern you have.  A power point has got attached inadvertently!

George

Link to Wikimedia Commons with several images of similar jointing:

https://commons.wikimedia.org/wiki/Category:Joint_(geology)

Caithness flags, in northeast Scotland are a classic example, as are the Marcellus and Utica shales in NY & PA.  A web search for Marcellus geology would be productive.

As a sedimentologist with a long research experience also on carbonate platform, i can confirm that these structures are definitely not mud cracks. It looks like a intraclastic breccia, with some superimposed stylolitization. 

thank you everybody for your valuable feedback.

No, it's not mud crack, typical bedded limestone. 

the almost regular and opened-up defects in bioturbated/ clastic limestone have been confused for the mudcracks. the structure as commented by many reviewers should be polygonal, which is missing but what is more important that any crack in the bedrocks happened in the geological past, can not be preserved as an empty opening, rather necessarily be filled with some secondary material. in case of mud cracks, it should be the superimposing sediment filled in these cracked/ desiccated openings in the mud/clay beds. the filled up crack would be represented similar to the fig shown in the attached photo.

Dear Dr. Sati,

Thank you for the explanation. of course in my photos opening between limestones are not filled by any cement. in Conclusion as commented by almost everybody, this structure corresponds to a weathering process.

They are not mud cracks because they usually are constituted by poligons whithout any preferred orientation of their sides. The photo's fractures seem two orthogonal joint system.

Hi,

Mud-cracks are formed on mud, that is why they are named as "mud-cracks". This picture belongs to limestone.

Regards

it is apparent, the lithology is limestone not mud. It is most like joint, fissures due to weathering, moreover, these joint are not filled with secondary materials (cement).

These are not mudcracks.  In addition, I want to clarify an important point.  The previous comments that imply that limestone is not mud are highly misleading.  Limestone is a sedimentary rock composed of calcium carbonate.  Limestones can be composed of any grain size, as long as it is mainly made of calcium carbonate.  Therefore, limestones can be composed of mud-sized grains.  And, so, yes, many limestones do contain mudcracks.

According to the surface texture and the facies you describe, I am sure that it is not mud crack. Mud crack forms in supratidal environments under arid conditions. The arid conditions and dewatering of water led to cracking of mud, in which with decending to lower parts the crack will be thinner and narrower. That is why the mud cracks are wedge-shaped. Under this condition we expect fenestral fabric and calcite pseudomeorphs after gypsum/anhydrite. This surface represents fractures relatued to folding.

These fractures are certainly not the mud cracks as the same are usually polygonal /irregular and filled with secondary cement.

Certainly they are NOT mud crack, most probably a bedding plane with two well defined joints.

Certainly they are NOT mud crack, they form in secondary

Hi Dhouha,

I agree with all that they are not mud crack, but they should be issue of the phenomena of diaclase.

Best regards,

Hakima

The man's foot in the picture shows that this snap was taken vertically, camera looking downward. Outcrop's first impression displays that the geologist is standing just on the bedding plane and the fractures/cracks might be initiated/generated due to unloading effect; and in a latter stage, they were filled before exhumation. Still a guess!

It is true sir. The case is closed. This is not a mud-crack. But it's good to read the comments of others that's how we learn and we improve. Thank you everybody

Best regards,

 Certainly they are NOT mud crack, they developed in lithified rock and mud cracks develop in the soft unconsolidated sediment

No mudcracks indeed!

No it is not mud crack. It s a jointed carbonate rock, the joint spacing is very wide and filled most probably by clayey soil

In mud, crack patterns are frequently seen with either an approximately rectilinear or hexagonal tiling. Here we show, experimentally, how a desiccation crack pattern changes from being dominated by 90° joint angles, to 120° joint angles. Layers of bentonite clay, a few mm thick, were repeatedly wetted and dried. When dried, the layers crack. These cracks visibly close when rewetted, but a similar crack pattern forms when the layer is redried, with cracks forming along the lines of previously open cracks. Time-lapse photography was used to show how the sequence in which individual cracks open is different in each generation of drying. The geometry of the crack pattern was observed after each of 25 generations of wetting and drying. The angles between cracks were found to approach 120°, with a relaxation time of approximately 4 generations. This was accompanied by a gradual change in the position of the crack vertices, as the crack pattern evolved. A simple model of crack behavior in a layer where the positions of previously open cracks define lines of weakness is developed to explain these observations.

Certainly it is not a mud crack, normal joint of two sets.

Of course it is not mud crack..

Not mud cracks. Looking like traces of secondary planes like joints.

Certainly, it is not mud crack, mud cracks usually have irregular shapes. These are bedding planes and joints in carbonate rocks.

Hi

For me it corresponds to large desiccation cracks

The hexagonal pattern is not well developed because the sediments are coarse

Yes it is joint got open due to weathering.