Dear Linda,

I agree with your observation and interpretation. The grade of metamorphism being very low, the planktonic foraminiferal tests survived alteration; in some cases perforation in the wall and initial tiny whorls are recognizable. Diverse forms in satisfactorily preserved state are visible in the thin sections. The forms appear identifiable if extracted undamaged from the sediments. The semi-opaque material filling the chambers may be calc-ferruginous matrix/cement or glauconitic sediments.

Sincerely,

Sanjay K. Mukhopadhyay

Dear Mrs. Vidal,

although micropaleontology is not my focal discipline I tend to describe these items as relic forams. I suggest finding circumstantial evidence based upon the material draped around these unknown objects.

What is the metamorphism like (very low grade stage?)?

What kind of minerals we have to deal with in the host rock enabling us to determine precisely the environment of deposition (marine?)?

At the very end the age of formation is key.

But there may experts on both groups of microfossils who can directly guide you to the genus or so. As a geoscientists treating the inorganic matter of geosciences but have a high opinion of paleontology as a means for chronology and palecology I try to take a stepwise approach and then I hand over my issue to the colleagues from the organic part of geosciences.

I wish you much success H.G.Dill

Dear Mrs. Vidal,

I know calcispheres from the Devonian. I agree with Mr. Mukhopadhyay: These are foraminiferes. Twin spheres, as you figure, do not occur among calcispheres.

Best wishes,

Andreas May

Dear Linda,

These pictures are indeed disturbing: the oval/elongate sections showing an opening might be interpreted as a calcisphere (calcio-dinoflagellate cysts, especially to "Pithonella" conoidea or alike); this also resembles some tangential section of a single chamber of formainferal test. But the "twin" spherical sections originate unambiguously from the tranverse section of biserial foraminifers (if planktic: Globigerinida, but it looks also like benthic agglutinating formas: Textulariacea - s please chech up whether the wall is rather "calcitic" recrystallized or consists of several metamorphized mineral grains).

Hope it will contribute positively to make up your opinion.

Best regards

Dear Linda,

Despite my little experience in the matter, here goes my humble contribution.

To begin with, it is not wrong to call these structures 'calcispheres' since the word itself, act as a descriptive term for those spherical hollow bodies made of calcite/aragonite. However, the term 'calcisphere' is generally used to refer to calcareous dinoflagellate cysts when it comes to post paleozoic sediments. Calcispheres (in this case calcareous dinoflagellate cysts) are always single chambered entities, and, when looked in thin section, they usually show a microcrystalline brown coloured wall, or a light coloured hyaline wall with acicular crystals disposed in a radial arrangement, and can be single o doubled layered, or mixed. Although this doesn't seem to be the case, taphonomic biases due to metamorphism effects can not be discarded at all, specially for those single spheres lying around there, however, and in agreement with opinions above, i think they are most likely foraminiferous tests.

Best wishes, and sorry for my poor english.

Lautaro

Your contributions have been very enriching for me, and I am very grateful to you for sharing your knowledge.

Finally, I can ratify and confirm the idea that they are foraminifera and can discard at all possible twined calcispheres because they just don't exist. Now, I can go on with my analysis confidently.

Thank you very much!

Dear Mrs. Vidal,

I enjoyed reading your answer that confirmed the item to belong to the group of foraminifera.

So I learnt something during my studies in paleontology by the beginning of the 1970s at Würzburg University, Germany. Since then I have not been dealing anymore with microfossils, only with the inorganic part of geosciences.

It is a paleontological residue of mine.

With kind regards

Harald G. Dill

Dear Linda

They are indeed foraminifera with their small globigeriniform test, spherical chambers and aperture position. Their thin test wall, few chambers and low spiral side invoke : Globuligerina calloviensis which is Callovian in age.

Best wishes

Dear Vidal

they are two chambers test of Foraminifera

Dear.Linda

All the attached pics represent Foraminifera, whereas the calcispheres represent ONE INTACT spheroid Chamber...

The pictured spheroidal shape is calcisphere ( pithonella sp.) not foraminiferal one. it seems as single free one.

Reda ElGammal

Indeed the spheroidal fossil is a calcisphere but the globigeriniform tests are of Foraminifera.

Indeed these are foraminifera.

Yes, spherical form is calcispher.

The globular chamberd forms are foraminifers.

probbly is double spheric chamberes of early foraminifera

Most of them are the sp. of Globigerinoides and/or globojerinita which are the planktonic foraminifers of deeper marine setting and spheroidal fossils do resemble calcisphere but it's not a thumb rule always, calcisphere can be easily confused with a planktonic foram, e.g Orbulina universa but the morhpmetric analysis is taken into account.

Definitely, they are globigerinid planktonic tests. As Carmen stated previously single spheres are due to random sections. They lack the double-layered wall, the characteristics of calcispheres.

They lack the characteristic morpho;ogical and optical features of calcisphers (e.g. individual sphere, rings and centeral areas). The specimens shown in the pictures appeared as two or more sphers attached together.

definitly, It is a planktonic foraminifera suffered from diagenesis.

Hi Linda,

Having regard to: 1) my professional experience in working in areas with predominantly metamorphic rocks; 2) the study of calcareous dinoflagellate cysts mainly in thins sections; 3) the definition of Keupp, 1991: "the calcareous dinoflagellate cysts definition is based on the crystallographic orientation of calcite crystals forming the calcareous wall (or at least its outer part); 4) the lack of definitive features of calcareous dinoflagellate cysts;

I support your opinion, as well as that of other colleagues, who defined the sections shown in your pictures as sections of planktonic foraminifera.

Good luck !

Greetings,

Daria

Dear Linda,

Please indicate the age of your samples.

They are planktonic foraminifera ( Globigerinids ). Calcispheres is dominant in Cretaceous, while the Globigerinids are dominant during Cenozoic

Helo Maher i saw your image specially the first one on the left, my first impression it is Foraminifera (Globigerinoids), i can't figure the species and its not Calcisphere.

Thank you

They appear to be planktonic foraminifera.