Hi,

could these be microbialites?

marc

You may need to obtain some petrographic sections of these structures.

Mihai

They look very much like stromatolites (=microbialite), which are accumulations of sediment that adhered to the surface of a mat. Most typically, blue-green bacteria form these mats. The bacteria grow up through the sediments on the surface, and the process repeats. I too recommend making thin-section. In recent years microbialites have been found to be interlayered with sponges (Porifera).

Please provide us with a more detailed investigation of

a) lithology (carbonates, sulfates..)

b) body fossils and trace fossils others than this

c) existing environment analysis.

I suggests algal growth forms (?)

For more details and for comparison also of images see the study:

DILL, H.G., BOTZ, R. , BERNER, Z., STÜBEN, D., NASIR, S. and AL-SAAD, H. (2005) Sedimentary facies, mineralogy and geochemistry of the sulphate -bearing Miocene Dam Formation in Qatar.- Sedimentary Geology, 174: 63-96.

HGD

Dear Harald,

Hi,

1-As other colleagues have said, it is better that you prepare thin sections perpendicular to the beds. A stromatolite section is an alternation of light layers (carbonate) and dark layers (mostly remains of cyanobacteria and to some extent bacteria). If you are lucky, in this period you will see a layer with evaporitic minerals such as anhydrite and gypsum, which you will see in birefringence light as colored crystals in beautiful colorful. which sometimes have fenestrate structures.

2- In the first photo (105457), you can probably see a dome-shaped stromatolite from the top view of this organosedimentary structure. It is less likely that the same problem exists in the side photo 104502)).

3-In the two lower right figures (104525 and 104523) you probably have a vertical cross-section of the columnar stromatolite in the middle and its wavy layers on the sides. Of course, there is a less possibility that it has been, the bed is upside down and the stromatolite layers is dome-shaped.

With best wishes,

Jafar

Observar bien que no sean pistas de invertebrados (ichnos)