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NANNOFOSSILS COCCOLITHS
Hans R. Thierstein
Department of Earth Sciences, Swiss Technical
University, Zürich, Switzerland
Definition
Nannofossils/coccoliths: Minute (ca. 10
À6 m) calcite skeletons, produced by marine phytoplankton and found in
deep-sea sediments
General significance
Coccolithophorids are a major group of primary producers
in the photic zone of the world’s oceans today. Their single
cells (coccospheres) are covered by coccoliths, which are
structured aggregates of calcite crystallites (Figure 1).
The calcite platelets (coccoliths) covering these cells
sink to the ocean floor and form the dominant part of the
calcareous oozes that are found on most ocean floors
at water depths of less than 4–5 km (i.e., above the
CCD). Vast amounts of nannofossil chalks have accumulated on the world’s ocean floors since the late
Jurassic. Nannofossils include coccoliths and a few other
biogenic remains of similar size, such as calcitic cysts of
dinoflagellates (Thoracosphaera sp.), or of unknown taxonomic affinity, such as star-shaped Discoaster sp. in Tertiary sediments or rock-forming Nannoconus sp. in
Cretaceous deposits.
Coccoliths and nannofossils have been used in the dating of sediments (biostratigraphy), in the reconstruction of
the history of the world’s oceans (paleoceanography), and
in the analyses of evolutionary processes (Figure 2).
Biostratigraphy
Nannofossils have become very important in the determination of the geologic age of fine-grained, marine sediments (Perch-Nielsen, 1989; Bown, 1999) both in
academic research and in oil exploration. Nannofossils
are a major constituent of many marine sediments (up to
90 % in calcareous oozes), they are a highly diverse group
(up to 150 known species in the late Cretaceous), and they
can be quickly prepared on smear slides and examined in a
polarizing light microscope. A quantum step in our knowledge of the taxonomy and biostratigraphy of
nannofossils – and of many other marine microfossil
groups – was taken with the initiation of systematic drilling of the world’s ocean floors by the Deep-Sea Drilling
Project in 1967.
Paleoceanography
This field was initiated with the publication of Studies in
Paleo-Oceanography (Hay, 1974) containing the first
integrated attempts to reconstruct aspects of the history
of the world’s oceans. Since then, various paleoceanographic proxies – prominently among them are
nannofossils – were used to reconstruct the history of surface currents, long-term changes in water temperature,
carbonate saturation of oceanic water masses, primary
productivity, etc. (e.g., Stoll and Ziveri, 2004). Correlations between coccolith sizes of certain taxa and calcification and pCO 2 changes in laboratory experiments and a
sediment core may hold potential for a new paleoproxy
J. Harff et al. (eds.), Encyclopedia of Marine Geosciences, DOI 10.1007/978-94-007-6238-1,
© Springer Science+Business Media Dordrecht 2016
NANNOFOSSILS COCCOLITHS
Hans R. Thierstein
Department of Earth Sciences, Swiss Technical
University, Zürich, Switzerland
Definition
Nannofossils/coccoliths: Minute (ca. 10
À6 m) calcite skeletons, produced by marine phytoplankton and found in
deep-sea sediments
General significance
Coccolithophorids are a major group of primary producers
in the photic zone of the world’s oceans today. Their single
cells (coccospheres) are covered by coccoliths, which are
structured aggregates of calcite crystallites (Figure 1).
The calcite platelets (coccoliths) covering these cells
sink to the ocean floor and form the dominant part of the
calcareous oozes that are found on most ocean floors
at water depths of less than 4–5 km (i.e., above the
CCD). Vast amounts of nannofossil chalks have accumulated on the world’s ocean floors since the late
Jurassic. Nannofossils include coccoliths and a few other
biogenic remains of similar size, such as calcitic cysts of
dinoflagellates (Thoracosphaera sp.), or of unknown taxonomic affinity, such as star-shaped Discoaster sp. in Tertiary sediments or rock-forming Nannoconus sp. in
Cretaceous deposits.
Coccoliths and nannofossils have been used in the dating of sediments (biostratigraphy), in the reconstruction of
the history of the world’s oceans (paleoceanography), and
in the analyses of evolutionary processes (Figure 2).
Biostratigraphy
Nannofossils have become very important in the determination of the geologic age of fine-grained, marine sediments (Perch-Nielsen, 1989; Bown, 1999) both in
academic research and in oil exploration. Nannofossils
are a major constituent of many marine sediments (up to
90 % in calcareous oozes), they are a highly diverse group
(up to 150 known species in the late Cretaceous), and they
can be quickly prepared on smear slides and examined in a
polarizing light microscope. A quantum step in our knowledge of the taxonomy and biostratigraphy of
nannofossils – and of many other marine microfossil
groups – was taken with the initiation of systematic drilling of the world’s ocean floors by the Deep-Sea Drilling
Project in 1967.
Paleoceanography
This field was initiated with the publication of Studies in
Paleo-Oceanography (Hay, 1974) containing the first
integrated attempts to reconstruct aspects of the history
of the world’s oceans. Since then, various paleoceanographic proxies – prominently among them are
nannofossils – were used to reconstruct the history of surface currents, long-term changes in water temperature,
carbonate saturation of oceanic water masses, primary
productivity, etc. (e.g., Stoll and Ziveri, 2004). Correlations between coccolith sizes of certain taxa and calcification and pCO 2 changes in laboratory experiments and a
sediment core may hold potential for a new paleoproxy
J. Harff et al. (eds.), Encyclopedia of Marine Geosciences, DOI 10.1007/978-94-007-6238-1,
© Springer Science+Business Media Dordrecht 2016