Nannoliths

Cenozoic Taxa

Nannoliths fam inc sed sensu Young & Bown 1997

Submitted by Jeremy Young on Fri, 06/02/2009 - 13:13

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161 reads
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Neogene: Nannoliths
Paleogene: Nannoliths fam inc sed

Nannoliths ord inc sed sensu Young & Bown 1997

Submitted by Jeremy Young on Fri, 06/02/2009 - 13:13

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445 reads
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Neogene: Nannoliths
Paleogene: Nannoliths ord inc sed

Minylitha convallis

Edited by Lyndsey on Thu, 10/03/2011 - 14:34

Minylitha convallis Bukry 1973

Description: Plate-like rhomboidal nannoliths, with a raised rim on both sides. Acts as a single crystallographic unit with the optic axis nearly perpendicular to the plate.

Remarks: In plan view M. convallis shows only low birefringence and is easily overlooked. The dog-bone like side view, first described by Theodoridis (1984), is more distinctive and makes identification unambiguous.

The affinities of this species are unknown, but since it is formed of a single crystallographic unit it may be related to the Triquethrhabdulaceae.

Original description:

Size: 4-8 microns long, usually 4-6 microns.

Geological Time Data

Geological Time Periods:

NN11a

NN9

Biblio Reference:

Young, JR. 1998. Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Notes on occurrence information:

A more precise beginning of this species range is mid NN9. This species is often abundant but distribution is rather sporadic.

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519 reads
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Neogene: Minylitha; Minylitha convallis; Nannoliths

Florisphaera profunda

Edited by Lyndsey on Thu, 10/03/2011 - 13:54

Florisphaera profunda Okada and Honjo, 1973

Description: Coccospheres artichoke-like, formed of numerous plate-like, slightly curved, nannoliths. The nannoliths are single calcite crystals with c-axis parallel to the length.

Remarks: Typically the nannoliths are slightly tapered and terminated at the broader end by a pair of crystal faces. They are easily overlooked in the light microscope but can be reliably identified and have yielded very strong palaeoceanographic signals in Quaternary sediments. They are also readily observable in well-preserved Pliocene and Late Miocene sediments, with unambiguous occurrence at least to NN10 and less certainly to NN5.

Original description:

Ecology: Florisphaera profunda is an exclusively deep-photic species, usually occurring below the deep-chlorophyll maximum and is most abudant below oligotrophic surface waters. It occurs in sediments at much higher abundances than classic surface oligotrophic taxa such Umbellosphaera or Discosphaera and so is more reliable as an indicator of surface water oligotrophy.

Florisphaera is abundant in modern deep photic communities and is believed to be an Haptophyte but its precise affinities are uncertain. The coccospheres are artichoke-like with individual liths formed of single calcite crystals. Very abundant in well preserved Neogene open-ocean sediments, but easily overlooked and so rarely recorded. Monospecific.

Varieties: Modern F. profunda is rather variable, there are three formally described varieties, and several undescribed forms so it may in fact be a plexus of several species. See Quinn et al. (2005) for a longer review and much new data:

Florisphaera profunda var. profunda Okada and McIntyre, 1980 - liths ending with straight of zig-zag edge.
Florisphaera profunda var. elongata Okada and McIntyre, 1980 - liths more elongate, ending in an obtuse angle.
Florisphaera profunda var. rhinocera Quinn et al. 2005 - liths ending straight edge with spine formed from ridge along dextral (right hand) side.

Geological Time Data

Geological Time Periods:

NN21

NN5

Biblio Reference:

Young, JR. 1998. Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Notes on occurrence information:

Question occur about the start of this range.

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807 reads
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Neogene: Discosphaera; Florisphaera; Florisphaera profunda; Nannoliths; Umbellosphaera

Triquetrorhabdulus

Edited by Lyndsey on Thu, 10/03/2011 - 13:40

Genus Triquetrorhabdulus Martini 1965

Description: Elongate nannoliths formed of three blades. Entire nannolith formed of a single calcite crystal, but with variable c-axis orientation, see discussion of Family Triquetrorhabdulaceae.

Remarks: The genus contains two discrete sets of species

T. carinatus group , with c-axis parallel to length and so always strongly birefringent, with length-fast orientation
T. rugosus group , with c-axis perpendicular to length, show low biefringence in most common orientation, with length-slow orientation

Type species: T. carinatus Martini 1965

Original description:

Geological Time Data

Geological Time Periods:

NN12

NP24

Biblio Reference:

Young, JR. 1998. Neogene. Calcareous nannofossil biostratigraphy. :225-265.

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543 reads
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Neogene: Nannoliths; Triquetrorhabdulus; Triquetrorhabdulaceae

Minylitha

Edited by Lyndsey on Wed, 09/03/2011 - 11:24

Genus Minylitha Bukry 1973

Description: Monospecific genus of rhomboid nannoliths wth c-axis perpendicular to plane of nannolith, see species description for notes.

Remarks:

Original description:

Type species: M. convallis Bukry 1973

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919 reads
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Neogene: Minylitha; Nannoliths

Discoasteraceae

Edited by Lyndsey on Tue, 01/03/2011 - 16:12

FAMILY DISCOASTERACEAE TAN, 1927

Description. Discoidal nannoliths of 3-40 elements radiating from a common centre. C-axes vertical, so nannoliths appear dark in plane-polarised light. Some early forms also include a cycle of birefringent units.

Taxa included: Discoaster, Catinaster.

	Discoaster variabilis group 6-rayed discoasters with bifurcations.
	Discoaster brouweri group 6-rayed discoasters without bifurcations, and forms closely related to D. brouweri with 3 to 5 rays
	Discoaster pentaradiatus group symmetric 5-rayed discoasters
	Catinaster 6-rayed discosters in which the birfurcations meet to form a rim, which extends proximally

Original description:

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4334 reads
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Neogene: Catinaster; Discoaster; Discoaster brouweri; Discoaster pentaradiatus; Discoaster variabilis; Nannoliths; Discoasteraceae

NANNOLITHS

Edited by Lyndsey on Tue, 01/03/2011 - 15:54

Nannoliths - informal grouping. Used here in the sense of Young & Bown (1987)

Description - the following groups of Neogene nannofossils are thought to be related to coccolithophores, but produce structures which are neither heterococcoliths nor holococcoliths.


Braarudosphaeraceae	Ceratolithaceae	Discoasteraceae	Sphenolithaceae	Triquetrorhabdulaceae

The term nannolith has been used, especially by palaeontologists, as a convenient term for structures about the same size as coccoliths and occurring with coccoliths, but lacking definite coccolith affinities. In the modern nannoflora, there are fewer groups of cryptic origins, and the term has been less widely used. However, it is useful for calcareous structures that are thought to be formed by haptophytes, but probably by a different biomineralisation process to either heterococcoliths or holococcoliths (Young et al. 1999).

NB The first use of the term in this sense appears to have been by Haq (1978, in Introduction to Marine Micropaleontology), and this was followed by Perch-Nielsen (1985, in Plankton Stratigraphy). By contrast, Aubry (1988 et seq., Handbook of Calcareous Nannofossils) places most of these groups in the Ortholithae.

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4139 reads
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Neogene: Nannoliths; Braarudosphaeraceae; Ceratolithaceae; Holococcoliths; Discoasteraceae; Sphenolithaceae; Triquetrorhabdulaceae

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