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Lithostromation perdurum
Lithostromation perdurum Deflandre, 1942
Description:
Original description
Constitué par un plateau triangulaire portant six perforations, sur les deux faces duquel le centre, formant piller, soutient un appendice à trois branches fourchues, évidées au-dessous, et dont les axes sont décalés de 30° à droite par rapport à ceux du plateau; chaque branche envoie un prolongement vers l'un des sommets du triangle et l'autre vers le milieu de chaque côté. En vue latérale (figs. 7, 8), l'organisme apparaît fortement bombé et rappelle un coussinet. 12 à 1 6 µ.
Translation of original description (translated by Sarah-Jane Jacket for Mike Styzen):
Triangular
plate with six holes on both sides, the centre, forms a pillar supporting an
appendix which has three forked branches, hollow below, and the axes are
shifted 30 to the right relative to that of the plate: each branch has an
extension to one of the vertices of the triangle and another branch towards the
middle of each side of the triangle. In lateral view, it appears strongly
curved and reminiscent of a cushion.
Reference
Deflandre G. (1942): Calcareous and siliceous morphogenetic possibilities compared, a new
calcareous microfossil with a complex structure, Lithostromation
perdurum n. g. n. sp. C. R. Acad.
Sci., vol. 214, pp. 917-920, text-figs. 1-9
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Neogene: Lithostromation perdurum
Comments
Paleogene reference
Bybell, L.M. 1975. Middle Eocene calcareous nannofossils at Little Stave Creek, Alabama. Tulane Stud.Geol. Paleontol., 11 (4)
Plate 19 figure 6
Pleistocene marker
This taxon is used as a Pleistocene biostratigraphic marker in the Gulf of Mexico. I have heard it works other places as well. This utility is generally better in shelf areas (paleobathymetry of Outer Neritic or shallower) although it is often seen in material from below the stratigraphic top. It can be quite common in shallow water sediments.
The placement of this marker is somewhat problematic. On my published GOM chart I place it just below the top of C. macintyrei. I've seen others place it just above that horizon. This may depend more on how C. macintyrei is picked than on reasons of diachronaity (is that a word?)...
Operosum?
I'm pretty sure that what I saw down there was L. perdurum, not L. operosum. If my concept is correct, L. operosum is comparatively round, where L. perdurum is triangular (though can have some "bulging" on the sides).
It's been a long time, but I'm pretty sure I could recognize both back then. Valid question, of course!
Thanks for the discussion.
So that places the top
So that places the top occurrence in the early Pleistocene, any idea how far down it goes?
I'm not sure
As I recall, I've seen it in Paleogene material. If it prefers shallow water settings throughout it's range as it appears to at the top, it may be necessary to look at sediment from shallower facies than we are used to working with for that answer.
agree...
I'm pretty sure I've seen it down there as well... but the bug is so spotty down there its base is useless -- at least in the GoM.
Spotty
Part of the problem may be that in older material we are looking at deep water. Up in the Plio/Pleistocene we looked at a lot of shelf wells.
L. perdurum
I've recorded L. perdurum from middle Eocene sediments (NP15) and I checked Laurel's database and she has it recorded from NP16. These samples typically represent middle to outer neritic water depths.