Groove

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Fig. 1. Feathered grooves. All specimens figured as SEM graphs. A-B: Ammonia beccarii (Linné), Adriatic Sea, Recent. Peripheral and oblique - umbilical views. Note the ridges on the apertural face that initiate the feathering when the next chamber is added during ontogeny. C-D: Neorotalia calcar (d'Orbigny), Keij Island, Indonesia. Recent. Ventral view of an entire specimen and detail of a ventral feathered groove covered by a folded outer lamella. Note the imperforate nature of the cover and the orifices of the canal system. Compare: enveloping canals. E-G: Unfeathered grooves in Ammonia ikebei (Inoue et Nakaseko), Eastern Kalimantan, Borneo, Upper Miocene. Peripheral view of entire specimen and details in oblique-umbilical and in dorsal views. Note the hemicircular attachment of the septal flap and the undivided umbilical plug that correspond to unfeathered septal grooves; af: apertural face; f: foramen; fea: feathered grooves; ol: (folded) outer lamella covering a septal groove that is converted to an interlocular space; or: canal orifice; pil: pile; s: septum; sgr; septal groove (unfeathered); spgr: spiral groove (unfeathered); upl: umbilical plug; (Hottinger, 2006; fig. 50)[1] CC/BY-NC-SA)
Fig. 2. Marginal cord in nummulitids. A-B: Assilina ammonoides (Gronovius), Recent, Gulf of Aqaba, Red Sea. SEM graphs after Hottinger, 1977. A: Detail of marginal cord in a shell broken in the axial plane. Double arrow B - B indicates the approximate position of the cut in the cast of Fig. B. B: Detail of marginal cord in an epoxy resin cast that was cut approximately in the equatorial plane (as indicated in Fig. A), showing canal and chamber lumina after dissolution of shell. White arrows indicate direction of growth. C: Nummulitic limestone from Steinbach, Einsiedeln, Swiss Helvetic Alps, Lower Eocene (Cuisian). Transparent light micrograph of section perpendicular to bedding plane. 1: Assilina sp. of A. ammonea- praespira phyletic line, with particularly large and prominent marginal cord; 2: Nummulites spp.; 3: Assilina sp. of A. spira phyletic line; 4: Assilina sp. of A. exponens phyletic line; 5: Asterigerina cf. rotula (Kaufmann): no marginal cord. ch: chamber lumen; isc: intraseptal canal system; mc: marginal cord; mcc: marginal cord canals; sf: septal flap; st: stolon; sulc: sulcus canal; (Hottinger, 2006; fig. 64)[2] CC/BY-NC-SA)

Definition

  • according to Hottinger (2006):

GROOVE - an elongated depression produced by external local thinning of the outer lamella. It is deepened by persistent thinning ot the secondary laminations and a concurrent thickening of adjacent inflational costae or ridges that are usually present. The grooves reflect the flow of pseudopodial protoplasm extruding from interlocular spaces (feathering) or along the shell's periphery (cord). They my be covered or partially closed by secondary lamellation in later stages of growth and converted into canals.




See also



References

Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744

Hottinger (1977), Foraminifères operculiniformes.- Mémoires du Muséum National d'Histoire Naturelle, Paris, (Série C, Sciences de la terre), t. XL, 159 p. + 66 pls.

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