Articles

Print Email

Pteropoda (Mollusca, Gastropoda, Thecosomata)
from the Eocene/Oligocene boundary interval
of three cored boreholes in southern coastal Tanzania
and their response to the global cooling event

Laura J. Cotton, Arie W. Janssen, Paul N. Pearson, and Rens van Driel

Plain Language Abstract

A major cooling event took place between 33.5 and 34 Ma, known as the Eocene-Oligocene transition (EOT). The response of many marine micro-biota, such as foraminifera, has been well documented, however, records of other marine organisms, such as pteropods, are less well-known. Pteropods are planktic gastropods, which spend their life in the water column, and are sensitive to changes in the ocean environment. Here we describe the assemblage and ranges of well-preserved pteropods though the EOT from three borehole records from Tanzania, an exceptionally understudied region. In total eight species were found in this material, three of which are new. The two most common species pass through the climatic event with no noticeable change in abundance. Three other species disappear during the transition, at a level similar to the planktic extinctions. The remaining species are too few to comment on. This demonstrates a likely response to the changing conditions, similar to some foraminiferal groups. Despite the small sample sizes, this study represents an important new record from an understudied region.

Resumen en Español

Pteropoda (Mollusca, Gastropoda, Thecosomata) del intervalo del límite Eoceno/Oligoceno de tres testigos de pozos en la costa sur de Tanzania y su respuesta al evento global de enfriamiento

La Transición del Eoceno-Oligoceno fue un período de grandes cambios climáticos y oceanográficos, que dio lugar a un cambio biótico generalizado. Sin embargo, el registro fósil de muchos organismos marinos sigue siendo irregular. Los moluscos planctónicos (Pteropoda) de tres pozos, de los que se obtuvieron testigos, que abarcan el límite Eoceno/Oligoceno (EOB) en el sur de la costa de Tanzania, están representados por ocho especies, tres de las cuales se describen como nuevas: Heliconoides nikkieae sp. nov., Limacina tanzaniaensis sp. nov. y Limacina timi sp. nov. Tres de las otras especies solo pueden determinarse con el uso de la nomenclatura abierta. Las dos especies más abundantes, H. nikkieae y L. timi, se encuentran a horcajadas sobre el EOB sin una pérdida notable en abundancia. Dos especies, Limacina robusta (Eames, 1952) y L. tanzaniaensis desaparecen antes del EOB. La especie Bovicornu aff. eocenense Meyer, 1886 desaparece poco después del EOB. Dos especies solo se encontraron en una sola muestra cada una, concretamente en el Eoceno de la sucesión. La respuesta a las cambiantes condiciones ambientales parece estar demostrada por dos o tres de las especies de Pteropoda que se extinguen antes o poco después del EOB.

Palabras clave: Gasterópodos planctónicos; Altaspiratella; Heliconoides; Limacina; Bovicornu; nuevas especies; distribución geográfica; rangos verticales; Transición Eoceno-Oligoceno (EOT)

Traducción: Enrique Peñalver (Sociedad Española de Paleontología)

Résumé en Français

in progress

Translator: Antoine Souron

Deutsche Zusammenfassung

Pteropoda (Mollusca, Gastropoda, Thecosomata) aus dem eozänen/oligozänen Grenzintervall aus drei Bohrkernen im südlichen Küstenbereich von Tansania und ihre Reaktion auf das globale Abkühlungs-Ereignis

Der Eozän-Oligozän Übergang war eine Periode großer klimatischer und ozeanografischer Veränderungen, die in einer weitverbreiteten biotischen Umwälzung resultierte. Der Fossilnachweis vieler mariner Organismen bleibt jedoch lückenhaft. Planktische Mollusken (Pteropoda) aus drei Bohrkernen aus dem südlichen Küstenbereich von Tansania, die die Eozän/Oligozän-Grenze umfassen, repräsentieren acht Arten, von denen drei als neu vorgestellt werden: Heliconoides nikkieae sp. nov., Limacina tanzaniaensis sp. nov. und Limacina timi sp. nov. Drei der anderen Arten können nur in die offene Nomenklatur gestellt werden. Die zwei am häufigsten vorkommenden Arten H. nikkieae und L. timi, überbrücken die Eozän/Oligozän -Grenze ohne nennenswerte Abnahme der Häufigkeit. Zwei Arten, Limacina robusta (Eames, 1952) und L. tanzaniaensis verschwinden vor der Eozän/Oligozän-Grenze. Die Art Bovicornu aff. eocenense Meyer, 1886 verschwindet kurz nach der Eozän/Oligozän-Grenze. Zwei Arten wurden jeweils nur in einer einzigen Probe gefunden und zwar im eozänen Bereich der Abfolge. Es scheint, dass eine Reaktion auf die sich verändernden Umweltbedingungen durch zwei oder drei der Pteropoden-Arten, die kurz vor oder kurz nach der Eozän/Oligozän-Grenze ausgestorben sind, aufgezeigt wird.

Schlüsselwörter: planktische Gastropoda; Altaspiratella; Heliconoides; Limacina; Bovicornu; neue Art; geografische Verbreitung; vertikale Reichweite; Eozän-Oligozän-Übergang

Translator: Eva Gebauer

Arabic

Translator: Ashraf M.T. Elewa

 

 

FIGURE 1. Location and geological map of the Tanzanian Drilling Project Eocene/Oligocene boundary sites (TDP 11, 12 and 17), additional Tanzanian Drilling Project sites in the area are also shown, modified from Nicholas et al. (2006). After Cotton and Pearson, (2011).

 figure 1

FIGURE 2. Altaspiratella bearnensis (Curry, 1982); RGM 777374; 1: apical view, 2: apertural view. Bar equals 100 μm.

 figure 2

FIGURE 3. Heliconoides nikkieae sp. nov.; 1: Holotype, RGM 777415a, apertural view; 2: apertural view, specimen lost; 3: paratype 1, RGM 777415b, umbilical view; 4: paratype 3, RGM 777 381, umbilical view; 5: paratype 2, RGM 777415c, apical view. Figures 3-1, -2, -3 and -5 from the type locality, TDP 17.36.1, 10-25 cm; Figure 3-4 from TDP 17.21.1, 9-20 cm. Bar equals 100 μm.

 figure 3

FIGURE 4. Heliconoides nikkieae sp. nov.; holotype, RGM 777415a, 3dPDF. To download zipped file of all animated PDFs click here.

figure 4 

FIGURE 5. Limacina robusta (Eames, 195); RGM 777423b, apertural view. Bar equals 100 μm.

 figure 5

FIGURE 6. Limacina robusta (Eames, 1952), Holotype, Natural History Museum, London BM 68457. Rahki Nala (Pakistan, western Punjab); Kirthar Formation, Lower Chocolate Clays (late Lutetian - Priabonian); 1: apical, 2: apertural, 3: lateral view. Bar equals 100 μm.

figure 6 

FIGURE 7. Limacina tanzaniaensis sp. nov. 1: Holotype, apertural view, RGM 777428b, TDP 17.38.2, 22-29 cm; 2: paratype 1, apertural view, RGM 777438, TDP 17.36.2, 80-95 cm; 3: paratype 2, umbilical view, RGM 777416b, TDP 17.36.1, 10-25 cm; 4: paratype 3, apical view, RGM 777416c, same data as 3. Bar equals 100 μm.

 figure 7

FIGURE 8. Limacina tanzaniaensis sp. nov.; holotype, apertural view, RGM 777428b, 3dPDF.  To download zipped file of all animated PDFs click here.

 figure 8

FIGURE 9. Limacina timi sp. nov.; 1: holotype, RGM 1007748b; 2: paratype 1, RGM 777408a; 3: paratype 2, RGM 777408b; 4: paratype 3, RGM 777414 m;. Apertural views. Bar equals 100 μm.

 figure 9

FIGURE 10. Limacina timi sp. nov.; holotype, RGM 1007748b, 3dPDF.  To download zipped file of all animated PDFs click here.

 figure 10

FIGURE 11. Limacina sp. 1. 1: RGM 777440c; apical view; 2: RGM 777440b; apertural view. Bar equals 100 μm.

figure 11 

FIGURE 12. Limacina sp. 2, RGM 777373,; 1: apertural, 2: apical, 3: oblique apical, and 4: umbilical views. Bar equals 100 μm.

 figure 12

FIGURE 13. Bovicornu aff. eocenense Meyer, 1886; 1: RGM 777370, apertural view; 2: RGM 1007784, basal view. Bar equals 100 μm.

 figure 13

FIGURE 14. Holotypes of Bovicornu eocenense Meyer, 1886 (1, 2) and B. gracile Meyer, 1887 (3, 4). Shell height of 1 = 2.8 mm, of 2 = 2.7 mm; 2 and 4 are magnifications of 1 and 3, respectively. Photographs after Hodgkinson et al. (1992, pl. 7, figures 9-12).

figure 14 

FIGURE 15. Range chart of pteropods, combined data of TDP 11, 12 and 17, calibrated to composite depths. Basic stratigraphical data mainly from Pearson et al. (2008, figure 16).

figure 15 

 

 

author1Laura J. Cotton. Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The Netherlands; present address: Florida Museum of Natural History, 1659 Museum Road, University of Florida, Gainesville, FL 32611, USA and Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL32611, USA ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Laura Cotton is a research assistant professor at the Department of Geological Sciences, University of Florida and Florida Museum of Natural History where she is additionally responsible for curating the micropalaeontological collections. Laura completed her MEarthSci at Oxford in 2008 and her PhD at Cardiff in 2013 working on the larger foraminifera of Tanzania. She has since held post doctoral positions at Naturalis Biodiversity Center, Leiden and the School of Biological Sciences at the University of Hong Kong. Her research interests are biostratigraphy, biodiversity and evolution of larger benthic foraminifera particularly through climate events such as the Eocene - Oligocene transition.

divider

author2Arie W. Janssen. Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The Netherlands; This email address is being protected from spambots. You need JavaScript enabled to view it.

From 1969 to early retirement in 1997 Arie W. Janssen used to be a curator of the Palaeontology Department (Cainozoic Mollusca) of the National Museum of Geology and Mineralogy (nowadays incorporated in Naturalis Biodiversity Center) at Leiden, The Netherlands). He was responsible for the large collections, amassed substantial material from all over Europe and published many papers on molluscan faunas, mainly on those from the North Sea Basin. From c. 1980 onward he specialized on fossil holoplanktic Mollusca, concentrating on systematics and biostratigraphy on a global scale. After retirement he remained an associate researcher of the Naturalis museum until the present day.

divider

author3Paul N. Pearson. School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff. CF10 3AT, United Kingdom; This email address is being protected from spambots. You need JavaScript enabled to view it.

Paul Pearson is Professor of Geology at the School of Earth and Ocean Sciences in Cardiff University in Wales, U.K. He specializes in the study of palaeoclimate and stratigraphy, with a special interest in the evolution, taxonomy, and geochemistry of planktic foraminifera. He has sailed on several occasions with the Integrated Ocean Discovery Program and its predecessors and has led campaigns of onshore drilling and field collecting in Tanzania and elsewhere.

divider

author4Rens van Driel. Buys Ballotsingel 85A, 3112 JD, Schiedam, The Netherlands; This email address is being protected from spambots. You need JavaScript enabled to view it.

Rens van Driel is an undergraduate student Applied Biology at the Aeres University of Applied Sciences. At his internship at Naturalis Biodiversity Center he got knowledgeable on 3D imaging by means of CT-scanning when he was working on comparative morphology of lower Diptera and Mecoptera. He wants to continue his studies to specialize in systematics. 

 

TABLE 1. Distribution of pteropod species in core TDP 11.

TDP Core section Depth interval (cm) Subsurface depth
(m)
Composite depth
(m)
Heliconoides nikkieae Limacina robusta Limacina timi Bovicornu aff. eocenense
11.26.2 64-74 82.14 98.14 1 - - -
11.32.1 33-40 89.63 109.63 - 1 - -
11.32.3 64-72 91.94 111.94 1 - 1 -
11.33.2 74-84 94.04 114.04 - - - 2

 

TABLE 2. Distribution of pteropod species in core TDP 12.

TDP Core section Depth interval
(cm)
Subsurface depth
(m)
Composite depth
(m)
Altaspiratella bearnensis Heliconoides nikkieae Limacina robusta Limacina timi Limacina sp. 2 Limacinidae indet. Bovicornu aff. eocenense
12.11.4 20-26 38.20 96.20 - - - 1 - - -
12.12.1 23-31 38.23 96.23 - 1 - - - - -
12.14.1 47-48,5 44.47 102.47 - - - - - - 2
12.14.1 51-53 44.51 102.51 - - - - - - 1
12.14.1 56-58 44.56 102.56 - - - - - - 1
12.14.3 23-31 46.23 104.23 - - - - - - 1
12.18.3 65-76 58.65 116.65 - - - 1 - - -
12.19.1 22-34 59.22 117.22 - - - 1 - - -
12.21.1 37-48 65.37 123.37 - - - 1 - - -
12.23.3 89-96 73.89 131.89 - - - - - - 1
12.24.3 0-10 76.30 134.30 - - - - - 1? -
12.26.2 54-62 81.79 139.79 - - - 1 - - -
12.27.1 35-45 89,60 147,60 - - 1 1 1 - -
12.28.1 66-76 90.91 148.91 1 - - - - - 2
12.29.1 25-35 91.90 149.90 - - - 1 - - -
12.29.2 20-30 92.85 150.75 - - - - - -  

 

TABLE 3. Distribution of pteropod species in core TDP 17 (question mark denotes poorly preserved specimens).

TDP Core section Depth interval
(cm)
Subsurface depth
(m)
Composite depth
(m)
Heliconoides nikkieae Limacina robusta Limacina tanzaniaensis Limacina timi Limacina sp. 1 Limacina sp. 2 Limacinidae indet. Bovicornu aff. eocenense
17.15.1 50-63 47.95 47.95 2 - - - - - - -
17.17.2 0-14 54.45 54.45 2? - - - - - - -
17.18.3 10-25 58.55 58.55 2 - - 1 - - - -
17.21.2 9-20 62.87 62.87 1 - - - - - - -
17.23.2 0-10 66.57 66.57 - - - 1? - - - -
17.23.3 0-13 67.54 67.5 2? - - - - - - -
17.23.3 99-105 68.56 68.56 2 - - - - - - -
17.24.1 20-35 68.30 68.30 5 - - - - - - -
17.24.2 0-15 69.10 69.10 - -  - 1 - - - -
17.25.1 0-15 71,40 71.40 2 - - - - 1 - -
17.25.1 50-60 71.90 71.90 1 - - - - - - -
17.25.2 48-58 72.88 72.88 1 - - 1 - - - -
17.26.3 10-25 77.90 77.90 2 - - - - - - -
17.31.1 20-35 89.10 89.10 2? - - - - - - -
17.31.2 0-15 89.90 89.90 1 - - - - - - -
17.31.3 0-15 90.90 90.90 3? - - - - - - -
17.31.4 0-12 91.90 91.90 1? - - - - - - -
17.32.1 10-25 92.00 92.00 2? - - - - - - -
17.32.2 0-15 92.90 92.90 3 - - - - 1 1? 1
17.32.4 14-20 95.04 95.04 1 - - - - - - 1
17.33.1 3-18 95.93 95.93 1 - - - - - - 2
17.33.3 0-15 97.90 97.90 3 - - 1 - - - 1
17.34.1 0-7 98.90 98.90 4?   - 2 - - 3? 1
17.34.2 91-99 100.81 100.81 - - - - - - - 2
17.36.1 0-5 103.90 115.90 1 - - 1 - 2? 1? 2
17.36.1 5-13 103.95 115.95 - - 1 - - - - -
17.36.1 10-25 104.00 116.00 11 - 7 - - - - 3
17.36.2 52-59 105.42 117.42 - 1 - - - - 3? -
17.36.2 80-95 105.70 117.70 3+5? 2 1 2? - - 2? -  
17.37.1 0-13 106.90 118.90 - 6 - - 5 - - -
17.37.1 32-47 107.22 119.22 - 1 - - - - - -
17.38.1 25-35 110.15 122.15 - - 5 1 - - - -
17.38.2 22-29 111.12 123.12 - 1 2 - - - - -
  62-70 113.52 123.52 - - - 1 - - - -
17.41.1 8-18 119.48 131.48 - - 1 2? - - - -
17.41.3 0-15 121.40 133.40 - 1 1 - - - - -