overview (8)
Arkhangelskiales (2)
Eiffellithales (3)
Holococcoliths (26)
Nannoliths (10)
Podorhabdales (7)
Watznaueriales (1)
Mesozoic
User login
Paleogene
Paleogene (9)
Coccolithales (2)
Discoasterales (4)
Holococcoliths (1)
Isochrysidales (2)
Syracosphaerales (3)
Zygodiscales (3)
Search
Who's online
There are currently 0 users and 3 guests online.
Recent blog posts
Statistics
- Pages: 8613
- Users: 353
- Total Page Views: 1024603
Reticulofenestra pseudoumbilicus
Edited by Jeremy Young on Wed, 09/03/2011 - 17:10
Reticulofenestra pseudoumbilicus (Gartner, 1967) Gartner, 1969 [Coccolithus]
Description: Coccoliths >5μm (cf. e.g.: Backman, 1980; Young, 1991). Often dominates Middle Miocene - Early Pliocene assemblages.
Remarks: For biostratigraphy it is better to separate the >7μm specimens (e.g.: Rio et al., 1990; Raffi et al., 1995); i.e. a definition of >7µm is preferable for unambiguous identification of both the NN15/16 boundary (last occurrence of R. pseudoumiblicus) and the NN10A/B boundary (start of small Reticulofenestra interval/R.pseudoumbilicus paracme) .
Original description:
Variants:
R. ampliumbilicus Theodoridis, 1984 - forms with very wide central-area, possibly an early growth phase.
R. antarctica (Haq, 1976) Driever, 1988 [Dictyococcites]- closed central-area
R. tenuistriata (Kamptner, 1963) Martini, 1979 [Coccolithus] - sensu Varol, 1989 = 5-7μm R. pseudoumbilicus.
- Login or register to post comments
- 1868 reads
- Printer-friendly version
Comments
Reticulofenestra (Dictyococcites) antarctica
The extinction or LCO of this variant/morphotype/species, usually under the name Dictyococcites antarcticus, is used in the Gulf of Mexico as a stratigraphic marker in the Early Pliocene, probably within NN 15.
Wei (1990) contended that this taxon is a junior synonym of Reticulofenestra perplexa (Burns) which was described as being an order of magnitude different in size. The (informal) consensus amongst GOM workers appears to be that Burns had the unfortunate experience of describing something that did not in fact exist, and should therefore be ignored. Common usage continues to be D. antarcticus.
R. pseudoumbilicus
Specimens between 5 um and 7 um have been described by Sato et al 1991 as Reticulofenestra ampla. This species has a LAD in NN16. (ref.: Sato, T., Kameo, K., Takayama, T., 1991 - Coccolith biostratigraphy of the Arabian Sea. Proc. ODP Sci. Res., 117: 37 - 54)
I do mention R. ampla on the
I do mention R. ampla on the minutula page, and suggesting it should be regarded as a synonym of R. minutula. That is plainly not right since I also gave 5 microns as the maximum size for R. minutula. recognising these medium size reticulos in the late Pliocene is useful. There is a problem that R. ampla Sato is a junior homonym of R. ampla Theodoridis, but it would be straightforward to propose a substitute name.