J. Nannoplankton Res. 36 (1), 2016, pp.61–63 © 2016 International Nannoplankton Association
ISSN 1210-8049 Printed by The Sheridan Press, USA61

A new early Miocene Sphenolithus species from the South
China Sea
Shijun Jiang*, Yasu Wang
Department of Ecology, Jinan University, Guangzhou 510632, China; *sjiang@jnu.edu.cn

Osman Varol
Varol Research Limited, 12 Tan-y-Bryn Road, Rhos-on-Sea, LL28 4AE, UK

Rui O.B.P. Da Gama
Applied Stratigraphy and Paleontology, Shell International Exploration and Production, 200 North Dairy Ashford, Houston, TX 77079-1197, USA

Teodora Blaj
BugWare Inc., 1615 Village Square Blvd., Ste. 8, Tallahassee, FL 32309, USA
Manuscript received 2nd February, 2016; revised manuscript accepted 29th February, 2016

Abstract A routine biostratigraphic study has revealed a new early Miocene calcareous nannofossil species,
Sphenolithus pospichalii sp. nov. from cutting materials in Well LW13-1-1 drilled by the China National Offshore Oil
Corporation (CNOOC) in the northern shelf of the South China Sea. This new species is medium to large in size witha tapered, monocrystalline apical spine and a wide, trapezoidal proximal cycle. It displays a needle-nose-plier-shaped
birefringence pattern with a characteristic flat-topped, arch-shaped base. Sphenolithus pospichalii sp. nov. occurs in
Martini Zone NN4 and shows its acme in the basal part of this zone, and thus is a potential marker for the subdivisionof NN4 due to its short stratigraphic range.

Keywords Calcareous nannofossil, Sphenolithus, early Miocene, South China Sea, new species
1. Introduction
Sphenolithus are an extinct group of calcareous nannofossils that are wedge-shaped with a proximal cycle of radial
elements surmounted by an apical spine. This group firstoccurred in the early middle Paleocene (Martini, 1971),
rapidly diversified and thrived in the Eocene through early
Miocene (Perch-Nielsen, 1985), and finally disappeared in
the late Pliocene (Boudreaux, 1974). During their diversification period, more than 23 species evolved within a <30Ma
period in the mid-low latitudes and thus provided many
excellent biostratigraphic markers (Martini, 1971; Bukry,1973). The description herein of a new, short-ranging, early
Miocene Sphenolithus species further strengthens the usefulness of this group in biostratigraphy.
2. Materials and methods
Drill cuttings were the only materials available for the biostratigraphic study of Well LW13-1-1, an oil exploration
well drilled by the China National Offshore Oil Corporation (CNOOC). The well is located approximately 150km
NWW of Ocean Drilling Program Site 1148 (18.8362°N,116.5657°E; water depth: 3294m), in a water depth of1920.6m on the northern slope of the South China Sea. Thecuttings are mostly dark-to-medium-dark-gray, calcareous
silty shale. The well has a complete sequence into the lateOligocene without major unconformities as evidenced bybiostratigraphy and the through-well seismic profile.
Routine smear slides were prepared following the“double slurry” method (Watkins & Bergen, 2003), andwere mounted with Norland 61 optical adhesive. This

procedure was adapted here by adding a few drops of~5% sodium hexametaphosphate solution during smearing to better disperse the materials, in order to processcoarse clastic rocks and cutting samples typically fromoil industry (Jiang & Zhang, in press). Nannofossils wereexamined with a Zeiss Axio Imager A2 microscope undercross-polarized light at 1000x magnification. A ½λ gypsum plate was used to demonstrate birefringence patterns
indicating C-axis orientation of various crystallographicunits. For SEM study, a settling technique was used instub preparation to remove large particles and fine clays(Bukry, 1969), and a Zeiss Ultra55 field emission scanning electron microscope (FSEM) was employed to examine fine-scale structures. Nannofossil zonation follows
Martini (1971).
3. Systematic paleontology
Order DISCOASTERALES Hay, 1977
Family SPHENOLITHACEAE Deflandre in Grassé, 1952Genus Sphenolithus Deflandre in Grassé, 1952
Sphenolithus pospichalii sp. nov.
Pl.1, figs 1–8
Derivation of name: After Dr. James J. Pospichal(BugWare Inc., Tallahassee, Florida, USA) in honor of
his tremendous knowledge of Mesozoic and Cenozoic
calcareous nannofossils.
Diagnosis: Medium to large pyramidal-shaped sphenolithwith the upper proximal elements always aligned parallel

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Jiang, Wang, Varol, Da Gama, Blaj

to the length of the species, displaying a needle-nose
plier-shaped birefringence pattern with characteristic
arched base.
Description: Sphenolithus pospichalii is medium to large
in size with a tapered, monocrystalline apical spine anda well-developed, trapezoidal proximal cycle. The mostimportant feature of this form is that the lateral elements(upper proximal elements) are always aligned parallel tothe length of the species. Its birefringence pattern underpolarized light resembles a needle-nose plier, in which theupper quadrants are triangular while the lower quadrants
are bracket-shaped forming a flat-topped arch. The upper
quadrants are ≤ ½ the size of the proximal quadrants.
Under polarized light, only the outer elements of theproximal cycle are highly birefringent when oriented at
0˚ to either optical axis; while oriented at the 45˚ position, the apical spine and the upper quadrant are highly
birefringent with the entire lower quadrant faintly so.
Differentiation: S. pospichalii differs from all othersphenoliths by its needle-nose plier shaped overall birefringence pattern, particularly the bracket-shaped lower
quadrants forming a flat-topped arch. It is most similar
to Sphenolithus milanetti; however, the latter species
has a much shorter apical spine, and also has no lateralelements aligned parallel to the length that instead gives
S. pospichalii a flat-topped arch shaped birefringence pattern under cross polarized light.
Remarks: S. pospichalii shows very close resemblancein the overall birefringence pattern to Sphenolithus “vietnamensis”, which is considered invalid because it is only
illustrated in a web page (http://www.varol.demon.co.uk/vietnamensis.html). However, the former has a characteristic flat-topped arch-shaped lower quadrant at both the 0˚and 45˚ positions, possibly as a result of better preservation.
Dimensions: For the 20 specimens measured, Base width:4.5mm (min.), 6.1mm (max.), 5.3mm (mean); Height: 6.0mm(min.), 10.2mm (max.), 8.1mm (mean).
Holotype size: Base width: 5.0mm; Height: 8.0mm.
Holotype: Pl.1, fig. 1.
Paratype: Pl.1, fig. 3.
Type locality: South China Sea; CNOOC Well LW13-1-1(~19.21°N, ~114.97°E; water depth: 1920.6m).
Type level: early Miocene (Zone NN4) CNOOC Sample
LW13-1-1, 2710–2720m (2720m below sea floor).
Observed stratigraphic range: Zone NN4. Its highest
occurrence was found right below that of Helicosphaera
ampliaperta (upper boundary of Zone NN4), its acme at

the basal part of NN4. Its first occurrence may be in upper
NN3 (Lord et al., 2009) but cannot be determined in thisstudy due to the uncertainties inherent to the use of drill
cuttings.
Observed geographic distribution: This species was observed from the offshore Philippines, the northern slopeof the South China Sea, and the Gulf of Mexico, whichsuggests a global, subtropical distribution.
Depository: All materials are archived and deposited at theDepartment of Ecology, Jinan University, Guangzhou, China.
Acknowledgements
We thank James Pospichal, Jackie Lees, and Jean Self-Trail for
their encouragement, and helpful comments and discussions;
Jamie Shamrock for her meticulous editorial comments and constructive suggestions; and two anonymous peers for their helpful reviews. We are grateful to Xiang Yu of the Jinan University
Analytical and Testing Center for his technical assistance with theSEM. This work was funded by a National Science Foundation ofChina grant (41372034) to SJ.

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A new early Miocene Sphenolithus species from the South China Sea

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