I think it's due to the highly organic matter associated with limestone as a result of the burying of organisms which had lived in this environment in that time.

What is lithology of the strange thing in the middle, and the delicate laminated one?

is it continuous or the  kerogenous  limestone formed as a lenticular shape with limited lateral extension. In any case, this may form due to biological activity and most likely controlled by the organic matter decaying or sulphide formation. In addition, it must be formed in anoxic environment.

The strange thing is highly kerogenous/bitumenous carbonate, and the delicate laminated is limestone.

If it is  associated with several other ones in same horizon, it is ball and pillow structure ( or boudinage) formed by breakage of  a competent  inside several incompetent beds., but if it is single one so it is growth of nudule , either pyrite  or calcite ... ect, see this paper may be useful    http://kurdistan-geology.com/?p=1388

http://kurdistan-geology.com/?p=1388

Rzger  Saalam Alikum

Sidi 

This resembles a concretion of altered lst.  The mineral fragmentation of the sample from the pic suggests calcification post deposition..    Could you send on a couple of pics of the crystal faces within the feature.. I do not believe that it has anything to do with the kerogen component of the strata.  My best guess now.

Pls ack owledge

Alla Wasaalan

Bob

Wa alaikum salaam Robert,

Unfortunately, I do not have any picture of crystal faces and I'm in US, far away from outcrop. Outcrop is in Iraqi Kurdistan and it is Upper Jurassic in age.

 Nauroztan Peroz

This structure is common in Jurassic rocks. Mostly it is diagenetic and post depositional structure. I am not sure it is ball and pillow structure!

The large crystals inside the structure is possibly due to growing or recrystallization!

it is better to examine the composition of hosted and the structure .

That looks like a coprolite to me. Is it phosphatic? Look for fish scales.

Dr. Rzgar: Please can you upload more photos? I am looking at the boundary between the strange thing (nodule??) and the fine-laminated around it. In the photo, it looks gradational (upper-right corner) and sharp (lower left corner) contact. So, the question: is it sharp or gradation?

Dilshad

Dear Dilshad,

Unfortunately, I do not have any more photos and I'm in US, far away from outcrop. Outcrop is in Basta Reawas (به سته ڕێۄاس), Iraqi Kurdistan and it is Upper Jurassic in age (Naokelekan Formation).

If you go back to Kurdistan in July, we can go together, but prepare yourself for hiking on Armusha Mountain (see the video). We can collect more samples and capture more photos.

Regards

In similar features of other places the formations are associated with petroleum geology.

The rolled, concentric shape and internal spiraling suggest to me an algal (microbialite, thrombolite) origin for this, perhaps rolling into this position by falling  off a nearby algal buildup, down the steep open-water face into the euxinic basin. Three dimensional form and thin section work might confirm, but I have seen similar pictures and wondered....unable to get back to the outcrop.