Based on the 1:400,000 structural index map, the area is Dezli-Paveh Mezosoic zone, and based on the 1:100,000 geological map of the area from the Geological Survey of Iran, the location is the Darband-e- Dezli that contains the limestone unit which is a thick-bedded to massive light cream biomicrosparite and has a geological age of upper Jurassic to early Cretaceous.
Possibly oncoid in limestone which form on the surface of intertidal and supratidal flats where carbonate precipitates from salt water spray and marine flood waters. An oncoid is a coated grain of algal (but not red algal) or microbial origin that is coarser than 2 mm in diamete.
Alternatively this might’ve a calcrete soil deposit. In calcrete (= caliche) soils similar concentric structures can and do form.
Very interesting rock. I think the large grains are oncoids because they developed on skeletal-fragment and intraclast nuclei and the coatings are not isopachous. The arrangement and size of the oncoids is interesting. The great range in sizes and the fact that they are "floating" in some kind of matrix makes me wonder if they have been resedimented. There are some broken oncoids but most seem to be intact so I wouldn't expect that this sediment was reworked by high energy currents. Is it possible that this is part of a small mass wasting deposit that formed by collapse of an intertidal channel? Thanks for getting my brain working. Have you found this site before? http://www.sepmstrata.org/page.aspx?pageid=211
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