Palynomorphs are acid resistant organic walled microfossils, ranging in size from 1micron to 1mm. They preserved in unoxidized, fine-grained sediments, primarily dark-colored. Palynomorphs rich rocks may contain millions of species per gram.

1. Dr Husain Shabbar
Independent Consultant Geoscientist

2. Microfossils
 Microfossils are the tiny remains of bacteria, protists,
fungi, animals, and plants.
 Size generally ranges between 1 µm to 1 mm.
 Microfossils are common feature of geological records
from the Archaean to present
 On basis of composition, they can be divided into four
groups.
I. Calcareous microfossils
II. Phosphatic microfossils
III. Siliceous microfossils
IV. Organic-walled microfossils /Palynomorphs

3. Organic-walled Microfossils/Palynomorphs
 Organic-walled microfossils are composed of entirely
mineralized proteinaceous material.
 Ranges in size 5 to 500 µm.
 Types of organic-walled microfossils:
1. Chitinozoa
2. Acritarchs
3. Spores and Pollen
4. Dinoflagellates
5. Scolecodont

5. Acritarchs
 They are defined as small,
organic-walled microfossils of
unknown biological affinity.
 They are characterised by varied
sculpture, some being spiny and
others smooth.
 The group includes any small
(20-150 microns ), organic-
walled microfossil.
 Many acritarchs are marine and
can include a wide range of
organisms, such as metazoan
egg cases, copepod eggs,
planktonic eukaryotic algae, and
cryptospores.
 Acritarchs are found in
sedimentary rocks from the
present back into the Archean.

6. Morphology of Acritarch
 Acritarch morphology forms the
basis of their classification.
 Body shape ranges from
spherical through fusiform
(grain of rice shaped), stellate to
prismatic.
 Processes may be simple or
complex, solid or hollow,
opening into the body or
separated from it.
 Ornament may occur on the
body and/or the processes.
 The form of opening called a
pylome ranges from a distinctive
opening in a defined area, a
random split anywhere on the
body or complete disintegration.

7. Classification of Acritarchs
 Acanthomorphs have spherical bodies with spines which usually
open into the body.
 Polygonomorphs have a body-shape defined by the number and
position of spines, they are often triangular or square in outline.
 Netromorphs have a fusiform body with one or more spines.
 Diacromorphs have spherical to ellipsoidal bodies with
ornament confined to the poles.
 Prismatomorphs have prismatic to polygonal bodies the edges of
which form a flange or crest which may be serrated.

8.  Oomorphs have an egg shaped body with ornament
confined to one pole.
 Herkomorphs have a roughly spherical body divided into
polygonal fields, rather like a football.
 Pteromorphs have a roughly spherical central zone often
compressed, surrounded by a flange or wing lamella which
may be sustained by radial folds or processes, they
resemble under the light microscope a fried egg!
 Sphaeromorphs have simple spherical morphology.

9. Classification of Acritarchs

10. Chitinozoa
 Chitinozoa are marine, flask-shaped
palynomorphs which appear dark,
almost opaque when viewed using a
light microscope.
 Chitinozoa range in length from about
50 to 2000µm.
 The biological affinities of Chitinozoa
are poorly understood, but they may be
eggs of marine metazoans.
 Walls of Chitinozoa are usually resistant
to oxidation, thermal alteration,
tectonism, and recrystallization of
CaCO3 matrix.
 They first appeared in the Early
Ordovician (Tremadoc Stage),
abundant and diverse until Silurian, but
majority became extinct at the end of
Devonian and disappeared in the
Earliest Carboniferous.

11. Morphology of Chitinozoa

12. Classification of Chitinozoa
 Classification within Chitinozoa is based largely upon the
gross morphology of the Test.
 The Order Operculatifera containing one family the
Desmochitina (simple spherical forms often found in
chains).
 And the Order Prosomatifera containing two families the
Conochitinidae (with little differentiation between flask
and neck) and the Lagenochitinidae (with clearly distinct
flask and neck).
 The most Tests have to some extent been distorted by
compression during compaction of sediments, so original
shape of a Chitinozoa test requires a careful interpretation.

13. Classification of Chitinozoa

14. Distribution and Paleoecology
 Chitinozoa are known only from marine sediments.
 Acritarchs are thought to be marine (Pre-Triassic).
 Chitinozoa are common in rocks deposited under well
aerated shallow water conditions, especially in shale and
siltstone but they are also found in limestone, dolomites,
graptolitic shales, slates and cherts.
 Acritarchs are typically isolated from siliciclastic
sedimentary rocks but are occasionally extracted from
carbonate-rich rocks.
 Both were planktonic, dead vesicles would have settled on
the ocean floor, where they were covered in sediment.

15. Applications
 They are important Palaeozoic microfossils as stratigraphic
markers.
 Acritarchs are extremely valuable for stratigraphic correlation of
rocks of Proterozoic and Palaeozoic age, primarily because they
are the only microfossils commonly preserved.
 Chitinozoa are similarly utilised in studies of Palaeozoic strata
especially during Ordovician, Silurian and Devonian periods.
 Both groups are also used in palaeoenvironmental
reconstructions, providing useful evidence on environmental
conditions where few other fossils exist.
 Occurrence of Chitinozoa in less metamorphosed sedimentary
rocks may allow an approximation of the depositional
environment.
 Both have potential as the Thermal Maturity Indices.