These microfacies belang to Cretaceous plagic limeston in the Azerbaijan (NW Iran). I cant identify plancton microfossils.
What is the magnification of the slide? Or else, give the scale bar to help tell what the fossil could be.
Obianuju P. Umeji
Dear Obianuju
All pictures taked by lens X10. I make scale bar for pictures too and send tou.
Tanks a lot
Mobin
Calcispheres (believed to be dinoflagellate cysts). Look e.g.:
Reháková D. 2000. Evolution and distribution of the Late Jurassic and Early Cretaceous calcareous dinoflagellates recorded in the Western Carpathian pelagic carbonate facies. Mineralia Slovaca, 32: 79–88.
Ciurej, A., Bąk, K., & Bąk, M. (2017). Late Albian calcareous dinocysts and calcitarchs record linked to environmental changes during the final phase of OAE 1d–a case study from the Tatra Mountains, Central Western Carpathians. Geological Quarterly, 61(4), 887-895.
Tanks a lot for your discussions.
Som other microfossils are in thin sections for txample Globotroncanids that I cant identify them. In attached file you can see a shell, this shell belong to which fossil?
The microfossils (dark arrows; attached file) resemble radiolaria consisting of micocrystalline calcite (calcitized radiolaria). For more details see Flugle, 2004; p 482.
As from Cretaceous limestones, these microfossil specimens are assignable to 'calcispheres' (most likely calcio-dinoflagellate cysts, probably transverse sections of Pithonella ovalis; next to the bivalve fragment lies an longitudinal-axial section of this species). The 'prismatic' shell section belongs to inoceramids (cf. reply from D. Simmons); but assignment to genus Inoceramus should be placed between hyphens ("Inoceramus") since it can not be identified in TS.
If you find any echinoderm section, I shall be interested in having a look into (In picture 52 I spotted a small transverse section of a distal brachial plate of crinoid - Roveacrinidae indet.).
Best
calcispheres and calcitized radiolaria we are identified like this microfacies in the Maastrichtain Sheranish Formation in the Euphrate - Anah Graben of iraq as open deep marine .
Calcisphers are abundant in Late Jurassic to Late Cretaceous rocks in Kurdistan, such as Chia Gara Fm., and Balambo Fm. Also most of radiolaria were calcitized. Please see my publications on RG about Chia Gara Fm. you may find some of them useful
tanks a lot for your discussions.
Dear Ibrahim, can you send me your paper of Chia Gara Fm related to my research?
These are calcispheres. Calcispheres are calcitic particles that range in size from 40 to 100 micro-mm. Their basic shapes vary from spherical to sub-spherical and ovoid to ellipsoidal (Dias-Brito, 2000). Some authors believe that calcispheres indicate deep open sea (Adams et al., 1967; Bishop, 1972).
Cretaceous calcispheres are more abundant and widespread within the Tethyan realm than elsewhere (Banner, 1972). Thus they probably were generated by organisms favoring the tropical over subtropical climatic zones (Masters & Scoot, 1978).
No oolite at all, but calcispheres (= calciodinoflagellate cysts) -@ Som Nath Kundal -
these are calcisphers pithonella spherica( for the spheric and small one) and p. ovalis (the oval one). the largest may be radiolarians. this microfacies is commun in upper cretaceous of Tunisia especialy in cenomanian/turonien boundary and in coniacian and Santonian in its north and central part.
There is no radiolarian in the pciture (neither siliceous 'glow', nor 'spiny' ornamentation visible) @ Nébiha Ben Haj Ali
In thin section, without dissolution, radiolarians often appear spherical, discoidal (Spheroidea) and can show their internal microstructure and their spines.
in some condition( dissolution, recristalisation) recognition becomes more difficult: they appear spherical with a” fuzzy” surface (a ghost).
But there is still no visible radiolarian in this picture of "chalky" facies, only calcispheres(Pithonella sphaerica and P. ovalis). They might occur elsewhere in adjacent coeval rocks, exposures and/or lateral sections, but not in the sample picture at hand. A guess or intuition is not a piece of evidence @Nébiha Ben Haj Ali
Only calacispheres are seen. Please upload more enhanced image or closeup views.
only calcisphers are clearly seen but we need a close view to identify if radiolarians are also present or note?
these are calcisphers for the spheric and small one ... the largest may be small ova of fishes dissolution and recrystallisation
Foraminiferal ooze does resemble this. Mostly spherical forms but there are tiny biserial forms. One needs an album of microfossils in thin section to give the details.
Obianuju P. Umeji
Se você fizer esta pergunda para qualquer geólogo, ele lhe dirá que é necessário e
obrigatório que se tenha essa amostra de rocha em mãos e fazer um exame a vista desarmada e/ou com lupa. Extremamente difícil fazer esse reconhecimento por foto.
Small size circule may be Calcisphers and big one may radiolaria
This facies is mostly of Late Cretaceous with calcisphere and other microfossils.
This type usually rich with calpionellids! I do not know if you observed it or not!
May be radiolaria molds which commonly replaced by calcite is also present!
I think most of this view Calcisphers and may be some radiolaria.
Foraminiferal ooze does resemble this. Mostly spherical forms but there are tiny biserial forms. One needs an album of microfossils in thin section to give the details.
Obianuju P. Umej
This microfossils are calcispheres , we have similar micorfacies in Kometan Formation (Late Turonian- Santonian) in Zargali area NE Iraq.
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