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Revue de micropaléontologie xxx (2013) xxx–xxx

Original article

A new Oligocene-Miocene calcareous nannofossil species:Pontosphaera wallacei

Une nouvelle espèce oligo-miocène de nannofossiles calcaires : Pontosphaera wallacei

Davide Persico ∗, Giuliana VillaDipartimento di Fisica e Scienze della Terra “M. Melloni”, Università degli Studi di Parma, Parco Area delle Scienze, 157/A, 43124 Parma, Italy

bstract

A high-resolution study of sediments from DSDP Leg 72 Site 516 provided the opportunity to reconstruct a detailed biostratigraphy for the lateligocene - early Miocene time interval. The detailed taxonomic investigation of calcareous nannofossils, performed by a quantitative analysis,ighlighted the presence of a species of Pontosphaera that does not show the morphologic features of any recognized species of this genus. Thispecies, which was previously classified as Pontosphaera sp., is here described as Pontosphaera wallacei nov. sp.

2013 Elsevier Masson SAS. All rights reserved.

eywords: Oligocene; Miocene; Taxonomy; Calcareous nannofossils; Atlantic Ocean

ésumé

L’étude à haute résolution de sédiments provenant du DSDP Leg 72 Site 516 a été l’occasion pour reconstruire une biostratigraphie détailléee l’Oligocène supérieur - Miocène inférieur. L’étude taxonomique détaillée, assistée par une analyse quantitative, a mis en évidence la présence

’une nouvelle espèce, déterminée précédemment en tant que Pontosphaera sp., et décrite ici formellement en tant que Pontosphaera wallacei nov.p.

2013 Elsevier Masson SAS. Tous droits réservés.

ots clés : Oligocène ; Miocène ; Taxonomie ; Nannofossiles calcaires ; Océan Atlantique

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. Introduction

This contribution is part of a larger project aiming to improvehe biostratigraphy of the Oligocene-Miocene boundary, throughevision of existent biostratigraphic schemes (Aubry and Villa,996; Raffi et al., 2006) by means of an integrated study of cal-areous nannofossil and foraminifera and the partial taxonomicevision of both paleontological groups.

Pontosphaera was first described by Lohmann (1902) in monograph on flagellate coccoliths, contributing to the

Please cite this article in press as: Persico, D., Villa, G., A new OligoceRevue de micropaléontologie (2013), http://dx.doi.org/10.1016/j.revmic.2

nowledge of their buoyancy in the Mediterranean area. Theriginal study of the genus is based on the living species Pon-osphaera syracusana, allowing a detailed description of the

∗ Corresponding author.E-mail address: persico.davide@gmail.com (D. Persico).

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035-1598/$ – see front matter © 2013 Elsevier Masson SAS. All rights reserved.ttp://dx.doi.org/10.1016/j.revmic.2013.07.002

rganism. The coccoliths are muroliths with a central area gen-rally characterized by a variable number of perforations. Aurolith is a loxolith characterized by a subvertical wall com-

osed of an outer rim-cycle with anti-clockwise imbricationnd an inner rim with clockwise imbrication (Young et al.,003).

A calcareous nannofossil biostratigraphic study of Deep Searilling Project (DSDP) Leg 72, Hole 516F from the southestern tropical Atlantic Ocean (Fig. 1) revealed the presencef well-preserved specimens of Pontosphaera sp. The speci-ens have been extensively examined in the light microscope

LM) and scanning electron microscope (SEM) to better observehe coccolith morphology. More particularly, the SEM was

ne-Miocene calcareous nannofossil species: Pontosphaera wallacei.013.07.002

pplied to observe the three-dimensional morphology of theoccoliths and in particular the differences between the prox-mal and distal sides. The LM and SEM analyses revealed anique morphology that, together with a distinct stratigraphic

ARTICLE IN PRESS+ModelREVMIC-224; No. of Pages 6

2 D. Persico, G. Villa / Revue de micropaléontologie xxx (2013) xxx–xxx

Fig. 1. Site 516: location Map.M

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istribution, brought us to the erection of a new Pontosphaerapecies.

. Materials and methods

The studied sediments are whitish-gray nannofossil oozesrom an Upper Oligocene to Lower Miocene carbonate richection recovered during DSDP Leg 72, Site 516 in the Southtlantic Ocean. The site was cored on the Rio Grande Riseear 30◦16′S, 35◦17′W (Shipboard Scientific Party, 1983, Leg2) (Fig. 1). The studied sequence from Hole 516F spans thetratigraphic interval from Core 11 to Core 03 (Fig. 2).

Quantitative analyses have been carried out at 10-cm inter-als on a total of 219 samples; in each sample at least 500pecimens have been counted. In 99 samples, the occurrence ofpecimens of Pontosphaera with taxonomic features not ascrib-ble to any described species suggested the need to undertake aore detailed taxonomic study.Smear slides were prepared by the settling technique (de

aenel and Villa, 1996), Norlan 61 optical adhesive was useds a permanent mounting medium. The slides were examined

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sing Zeiss Axioscop II microscope under cross-polarised lightXP) and phase contrast light (PC) at 1250× magnification.elected samples were re-prepared with the standard smear-slide

echnique (Bown, 1998), gold metallized and examined in the

miio

EM. A JEOL 6400 SEM was employed to observe fine-scalend three-dimensional structures. All materials are depositedn the collection of the Calcareous Nannofossil Laboratory athe Department of Physics and Earth Sciences “M. Melloni”,niversity of Parma (Italy).

. Results and discussion

At Hole 516F, the nannofossil assemblages are typi-al of tropical latitudes, characterized by Cyclicargolithus,mbilicosphaera, Coccolithus, Helicosphaera, Discoaster andphenolithus. The nannofossil assemblages show low total abun-ance and are affected by carbonate dissolution throughout theecovered interval.

The studied section is assigned to the Zones NP25 up toN2 (Martini, 1971, 1976), based on the occurrence of Sphe-olithus ciperoensis from the bottom of the sequence (Highestccurrence [HO] = 254.91 mbsf), and of Discoaster druggii

rom 196.38 mbsf up to the top (Fig. 2). The Oligocene-iocene boundary is recognized by the HO of Sphenolithus

apricornutus. In several samples, the occurrence of speci-

ne-Miocene calcareous nannofossil species: Pontosphaera wallacei.013.07.002

ens of Pontosphaera characterised by peculiar morphologys documented. The specimens are generally rare in the stud-ed sequence and the highest abundance is detected at the basef NN1 (Fig. 2). On the basis of a unique morphology and a

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MIO

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NP25

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D. druggii

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Age (Ma)

Martini (1971, 1976)

Pontosphaera wallacei (%)

CALCAREOUS NANNOFOSSI BIOEVENTS(Gradstein

et al. 2012)

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200

210

220

230

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Fig. 2. Percentage abundance and biostratigraphic distribution of Pontosphaera wallacei at Site 516 in the late Oligocene - early Miocene interval. (Gradstein et al.,2

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istinct stratigraphic distribution, we suggest the creation ofhe new species Pontosphaera wallacei described in Section 4Fig. 3).

At Site 516, Berggren et al. (1983) reported occurrences ofontosphaera spp. in the same time interval, however, these wereot classified at the specific level, and are probably ascribableo the new species P. wallacei. Yet, in Berggren et al. (1983), theresence of some specimens of Reticulofenestra oamaruensis inhe late Oligocene, a time interval not compatible with the bio-tratigraphic range of R. oamaruensis (HO = 34.09 Ma, Persicot al., 2011), required a more accurate taxonomic investigationo verify the presence of reworked specimens. Our taxonomic

Please cite this article in press as: Persico, D., Villa, G., A new OligoceRevue de micropaléontologie (2013), http://dx.doi.org/10.1016/j.revmic.2

tudy revealed that R. oamaruensis is not present and that mostrobably the species identified by Berggren et al. (1983) as

ab

. oamaruensis, is actually the new species P. wallacei hereescribed (Fig. 3).

Moreover, Bown and Dunkley Jones (2012) at Sites U1331-334, Integrated Ocean Drilling Program (IODP), Expedition20, report of indeterminate Pontosphaera specimens morpho-ogically compatible with P. wallacei (Plate 7, Photo 2), but in anlder interval (NP24). This datum could suggest an extensionf the range of P. wallacei down to NP24. As a consequence,. wallacei that is distributed in the study section from NP25o NN2, could have a stratigraphic range extending from thepper Oligocene NP24 Zone to the Lower Miocene NN2 Zone.lthough it does not represent a bioevent, its easily identifi-

ne-Miocene calcareous nannofossil species: Pontosphaera wallacei.013.07.002

ble occurrence may be a valuable tool for Oligocene-Mioceneiostratigraphy.

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Pontosphaera wallacei

distal view

lateral view

proximal view

outer rim

central area

inner rim

outer rim

central area

inner rim

outer rimcentral area

1 µm

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ig. 3. Pontosphaera wallacei: morphological features.

. Systematic palaeontology

Order ZYGODISCALES Young and Bown, 1997Family PONTOSPHAERACEAE Lemmerman, 1908

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Genus Pontosphaera Lohmann, 1902Species Pontosphaera wallacei Persico, nov. sp.(Plate 1, Figs. 1–24)

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Diagnosis: large, elliptical murolith with a closed central area,ith very bright distal rim in cross-polarized light (XP).

ne-Miocene calcareous nannofossil species: Pontosphaera wallacei.013.07.002

Description: the central area is closed and composed by 19-20attened crystals, with variable shape, arranged radially to form

central longitudinal slit. Typically V-units form the narrow

Please cite this article in press as: Persico, D., Villa, G., A new Oligocene-Miocene calcareous nannofossil species: Pontosphaera wallacei.Revue de micropaléontologie (2013), http://dx.doi.org/10.1016/j.revmic.2013.07.002

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Plate 1. Figs. 1–4. P. wallacei, Sample 516F 9R-4, 120–122 cm, light microscope (LM), X-nicols, 1250X. Figs. 5–8. P. wallacei, Sample 516F 9R-4 144–146 cm, LM,X-nicols, 1250X. Figs. 9–12. P. wallacei, distal view, Sample 516F 3R-6 108–110 cm, SEM. Figs. 13–16. P. wallacei, distal view, Sample 516F 9R-2 20.5–22.5 cm,SEM. Figs. 17–20. P. wallacei, proximal view, Sample 516F 3R-6 108–110 cm, SEM. Figs. 21–24. P. wallacei, proximal view, Sample 516F 9R-2 20.5–22.5 cm,SEM.

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mbricate outer rim, and R-units form the inner rim and theentral area (Young et al., 1997).

Differentiation: P. wallacei differs from Pontosphaera versas the latter shows two longitudinal slits in the closed centralrea and a broader raised rim. The stratigraphic distribution ofhe two species suggests that P. wallacei could have originatedrom P. versa, that goes extinct stratigraphically in NP23.

At the LM, P. wallacei can be easily confused with. oamaruensis. The central area, characterized by a longitu-inal suture composed by flattened crystals radially arranged,s very similar, but in Pontosphaera two thin rims are visible,hile in R. oamaruensis only one rim is birefringent in the LM.

n addition, the stratigraphic distribution of the two species doesot overlap.

Remarks: rare in Hole 516F; however, although severe car-onate dissolution affected this site, the main taxonomic featuresf this species are still recognizable.

Derivatio nominis: in honour of Alfred Russel Wallace, aritish naturalist, in the centenary of his death (8 January 1823

7 November 1913). He is best known for independently con-eiving the theory of evolution through natural selection, whichrompted Charles R. Darwin to publish his own ideas in “On therigin of Species”.Dimension: Length (L) = 8.5 �m (Paratype L = 9.4 �m).Holotype: Plate 1, Fig. 9Paratype: Plate 1, Fig. 13Type locality: DSDP 72 Site 516 Hole F, Atlantic Ocean

Coordinates: Latitude: −30.2765◦; Longitude: −35.285◦).Type level: Oligocene, Sample DSDP 9R-2-20.5-22.5 cm

Zone NN1).Occurrence: Zone NP24 to Zone NN2; present in sporadic

ccurrences; DSDP Hole 516F.

cknowledgements

The authors are grateful to Jean M. Self-Trail and Jorgutterlose for their critical review of the manuscript. Bryan

adner, Claudia Lupi and Fabio Florindo are also thanked foronstructive comments and suggestions.

ppendix A.

Calcareous nannofossils considered in this paper inlphabetical order of generic epithets:

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Discoaster druggii Bramlette and Wilcoxon, 1967; Pontosphaera syracusana Lohmann, 1902;

Y

aléontologie xxx (2013) xxx–xxx

Pontosphaera versa (Bramlette and Sullivan, 1961) Sher-wood, 1974;

Reticulofenestra oamaruensis (Deflandre in Deflandre andFert, 1954) Stradner in Haq, 1968;

Sphenolithus capricornutus Bukry and Percival, 1971; Sphenolithus ciperoensis Bramlette and Wilcoxon, 1967.

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