This document discusses calcareous nannofossils, which are microscopic algal fossils found in marine sediments. It provides background on nannofossils, including that they are coccoliths and coccospheres produced by haptophyte algae. The document outlines different forms of coccoliths, the geologic range of nannofossils from the late Triassic to today, how they are classified, their life cycles, and applications for using them in biostratigraphy. Examples of common nannofossil genera from different eras are also provided.

1. UNIVERSITY OF ALLAHABD
DEPARTMENT OF BOTANY
TOPIC: NANNOFOSSILS
Under the supervision of:
Prof. D K Chauhan
Presented by:
Swapnil Anand
M.Sc 1st Sem

2. INTRODUCTION
• Calcareous nannofossils include the coccoliths and coccospheres
of haptophyte algae and the associated nannoliths which are of
unknown provenance.
• The organism which creates the coccosphere is called a
coccolithophore, they are phytoplankton.
• Their calcareous skeletons are found in marine deposits often in
vast numbers, sometimes making up the major component of a
particular rock.
• A coccolith is a single disc-like plate which is secreted by the algal
organism and held in combination with several other, sometimes
varying shaped plates by an organic coating to form the
coccosphere.
• On death the individual coccoliths invariably become separated
and it is these that are most commonly preserved in the
sedimentary record.

3. DIFFERENT FORMS
Occasionally complete coccospheres are preserved and
provide valuable information, particularly regarding
coccospheres which possess two or more morphologicaly
different coccoliths.
There are two forms of coccoliths-
• The holococcoliths which are formed from calcite crystals
which are essentially identical in shape and size.
• The heterococcoliths which are formed from larger calcite
crystals which vary in size and shape.
• Most living forms are known to produce only
heterococcoliths and then only during the non-motile
stage of their life cycle. Those that do produce
holococcoliths do so only during their motile stage.

4. RANGE
• First recorded occurrences of calcareous nannofossils
(nannoliths) are from the late Triassic (Carnian).
• The locations from which the earliest nannofossils are
found include; the Northern and Southern Calcareous
Alps, Timor, North-West Australia and Queen Charlotte
Islands (Canada), all low latitude sites at the time.
• There are many claims for earlier occurrences but a lack
of substantiated evidence means these must be
excluded.
• One consequence of the first occurrence of calcareous
nannofossils in the late Triassic lies in the fact that this
was the first time open ocean planktonic organisms
utilised calcareous skeletons and exported calcium
carbonate into the deep oceans.
• Today coccolithophores are one of the most important
forms of phytoplankton found in the oceans, and may be
described as the grass of the sea.

6. CLASSIFICATION
• The classification of calcareous nannoplankton is carried out
under the International Code of Botanical Nomenclature.
• They are formally classified in the-
Kingdom Protoctista,
Phylum (or Division) Haptophyta,
Class Prymnesiophyceae.
• Classification is complicated by the fact that some species are
dimorphic, that is they possess more than one coccolith on a
single coccosphere. This may lead to the belief that two species
exist where in fact there is only one.
• Also, pleomorphism (where a holococcolith phase alternates
with a heterococcolith phase) may also result in coccoliths being
placed in different species or even genera when in fact they are
simply different stages in the life cycle of the same species.

7. LIFE CYCLE
• The chief reproductive mode of coccolithophores is
asexual by mitotic division through which the
coccoliths are redistributed amongst the daughter
cells.
• In some haptophytes complex life cycle is
demonstrated involving two or more
morphologically distinct phases.
• A typical coccolithophore life cycle consist of a
diploid stage, which is covered by heterococcoliths.
• Alternation of life cycle has been demonstrated in
culture studies. No conclusion data is drawn about
the causative factors controlling the trigger of phase
change.

9. APPLICATION
As the groups name suggests calcareous nannofossils are small,
generally less than 30 microns across and usually between 5 and 10
microns (individual coccoliths). This has advantages and
disadvantages.
Advantages include:
• Good preservation, their small size makes mechanical damage
unlikely.
• Widespread distribution, as part of the phytoplankton
coccolithophores are distributed throughout the photic zone
(predominantly the upper 50m of the water column) across almost
all marine habitats.
• A very large number of individual coccoliths may be preserved in a
tiny amount of sediment hence only very small quantities of sample
are needed to produce statistically valid results.

10. Disadvantages include:
• Because of dissolution of calcium carbonate at depth in
sea water (called the carbonate compensation depth
(CCD)), preservation is compromised in deep water
sediments.
• Because of their small size and resistance to mechanical
breakdown nannofossils can be reworked, great care is
therefore needed especially when utilising nannofossils for
biostratigraphic studies.
• Again, because of the small size the opportunities for
contamination are high, although careful and thorough
preparation and collection techniques should significantly
reduce this risk.

11. FUNCTION OF COCCOLITHS
Coccoliths supposedly shield the enclosed cell
from excessive sunlight, or concentrate light
towards cell centre due to convexo-concave
shape of coccoliths. Other varied functions
are floating devices, metabolic barriers,
stabilizers, defensive shields etc. Some
biologists are of the opinion that coccoliths
are by product of detoxification of carbonate
through the fixation of calcium.

12. Triassic & Jurassic Nannofossils
Anulasphaera helvetica Biscutum novum
Crucirhabdus minutus

13. Lower cretaceous nannofossils
Nannoconus abundans
Eprolithus floralis
Calcicalathina oblongata

14. Upper cretaceous nannofossils
Tranolithus orionatus Micula staurophora
Eiffellithus eximius

15. Discoaster tanii Chiasmolithus solitus
Palaeogene nannofossils

16. Neogene nannofossils
Coccolithus pelagicus Calcidiscus tropicus

17. REFERENCE
•https://www.ucl.ac.uk/GeolSci/micropa
l/calcnanno.html
•https://www.researchgate.net/publicati
on/287197575_Calcareous_nannofossils
_and_their_applications/