I have some samples from the Upper Cretaceous shale, North America.
I was able to obtained SEM images for what I believe some foraminifera genera; they are benthic forams. So far I identify some of them as possible as I can, but how I can be sure if my identifications are correct? Any suggestions?
Please see the attachment files as examples for some of the forams I found.
I suppose it would be useful to make up individual thin sections of the shells.
I download all of them. For me there are two species are looked agglutinated for the two first images. The others are not (if possible to put a number for each one to help you?).
To become sure for the identification it is important to redo a good preparation for the samples, where each test become clear and illuminate the maximum the detritus added in the test. There is a protocol for this.
Your forams seems very reworked, indead. I believe that the better solution will be the observation under a microscope by a specialist...
1 &2 are foraminifers highly reworked rest other 4 probably Petropods.
None of these is agglutinate! The first top two (1, 2) are not even benthics from their surface texture. The rest are calcareous benthics; most likely are (3, 4) Gavelinella plummerae and (5, 6) Lingulogavelinella modesta.
Dear Majed:
It looks like on the first two upper pictures you illustrated biserial foraminifers, the rest of the pictures - probably microgastropods. These two foraminifers are probably agglutinated, but it is not clear because of the poor preservation. To be sure that they are agglutinated you need to use a combination of SEM and energy dispersive X-ray spectroscopy, or may make thin sections of your free tests of foraminifers and look with a light microscope by using cross-nicoles. Good luck!
Galina Nestell
Thank you all for your answers. You really helped me.
Dr.Khalifa Elderbak could you please provide me with the papers that you showing these two figures from?
These are from my dissertation, but you could see better illustrations of the two species in Eicher & Worstell, 1970.
Majed,
all your figured specimens are calcareous benthic foraminifers. By my opinion fig 02and 03 show some buliminid, other are gavelinellids. Fig 05 is especially important - it looks like Gavelinella cenomanica that is marker of the Albian-Cenomanian. Good luck with further identification.
I fully support the opinion of Miroslav Bubik: 4 gavelinellids (or perhaps Anomalinoides) and 2 buliminids (perhaps Siphogenerinoides or alike). These are not agglutintated, just very poorly preserved from recrystallisation and/or corrosion.
Contrary to what I read in some of the reactions, this does not point to reworking (only if you would find this quality in modern deposits). The forams are just very old. The older the rocks, the more likely the forams become poorly preserved at some point through deep burial, orogenesis, groundwater flow, outcrop weathering, etc.
Obviously poor preservation is not a necessity: forams can be excellently preserved, particularly in old shales (little groundwater flow) that have hardly been buried. Clearly that is not the case here. Note that open/deep marine shales may contain abundant in situ agglutinated taxa, either calcareous or non-calcareous ones. Few of these consist of terrigeneous sand or coarse silt grains though.
Kenneth
Some agglutinated taxa are indeed amazing. In my classes I show some bizarre examples such as Technitella legumen, a species entirely built up from sponge spicules and a trochamminid, partly composed of razor sharp volcanic glass shards (link). Other bugs consist of radiolarians, iron concretions (originally pyrite framboids?) and probably fine (eolian?) silt. Yet, I never studied these aspects in detail. The DWAF (Deep Water Agglutinated Foraminifera) people should know much more. The open marine shales I was referring to usually contain abundant calcareous agglutinated taxa (Gaudryina, Spiroplectinella, ..) and less common non-calcareous bugs like Ammodiscus and Glomospira that consist of very fine particles.
http://www.mbari.org/mid-ocean-ridge-explosive-eruptions/
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