1. GENERAL GEOLOGY
( FOSSIL AND USES )
Diyar Shamsadeen Ahmed
Head of the department Lecturer
Dr. Ammar Isam Dr. Rashied Ja’afar
Technical College of Petroleum Mineral
Sciences - Zakho
Dept. of Petroleum Geology
first Year / 2nd
Semester (2022 – 2023)
Fossil, remains or imprints of plants or animals preserved from prehistoric times
by the operation of natural conditions. Fossils are found in sedimentary rock,
asphalt deposits, and coal and sometimes in amber and certain other materials.
Scientific study of fossils is pale ontology.
Types of Fossil
Fossils have broadly classified in to three types on the basis of their
1. Actual remains
3. Actual remains
▪ Frozen in ice
✓ In this type the remains of soft and hard parts of the
organism won’t alter.
➢ Molds or Casts in mud, sand and etc... that turn to rock.
➢ Imprint fossils are formed from an organism moving in some way, leaving
behind a trace or track. These tracks are preserved when the clay/silt dries
slowly and is covered by other sediment. Plants can also leave imprint
fossils when they are covered by sediment. The leaf tissue degrades, leaving
an imprint of where the leaf once was.
➢ Petrified fossils result from per mineralization, the replacement of
onceliving matter by minerals. Solutions containing silicates, carbonates,
iron or other minerals seep into the gaps and spaces between the cells, first
encasing the cells and eventually replacing the cells themselves. Over time,
minerals entirely replace the organic material, creating a petrified fossil.
✓ On the basis of the fossils distribution, occurrence and by their
haracteristics the fossils have divided into different types
5. • Body fossils: Well preserved entire organism unaltered and altered hard
parts and naturally formed moulds and casts are classed has body fossils.
• Chemical fossils. Well preserved palaeoproteins and amino acids and
structures resulting from recrystallization and carbonization process are
grouped as chemical fossils
6. • Trace fossils: Footprints, trails, burrows and tubes, coprolites and
fossilized eggs are termed as trace fossils and they also known as
• Derived fossils: The erosion of a fossiliferous rock may release fossils into
streams, and may deposit in younger sediments, so could be a source of
confusion when a stratigrapher tries to date the younger sediments. This is
not common, but fossils recycled in this way are called derived fossils.
7. • Living fossils: Fossils which range from ancient time upto the present day
without any change in their primitive characters are known as living fossils.
• Remaine fossils: Organic materials which have been rolled and abraded,
accumulating over a considerable period before their deposition are
termed as Remaine fossils.
8. • Facies fossils: Dissimilar assemblage of fossils which are controlled by
environment and restricted to certain sedimentary environment are known
as facies fossils.
• Pseudo fossils: Certain structures of sedimentary or tectonic origin which
resembles fossilized organic remains are termed as Pseudo fossils.
9. Uses of fossil
❖ Study of chronostratigraphy:
It is concern with the age of strata and their time relation.
The fossils contents of beds are used in interpreting the historical
❖ Index fossil and correlation of rocks:
Certain animal or plant remains are so characteristics of certain
geological origin that they are called as index. fossils. They used in
correlating in other areas.
❖ Study of paleogeography:
The adaptation of organisms are characteristics of particular
environment hence those shown by fossil forms may indicate the
extent and boundaries of formers land, water deltas, mountains,
deserts, lake, rivers, shorelines and the position of deep and
❖ Study of palaeoclimate:
The variation of temperature and the degree of moisture is
perhaps most clearly indicate by fossil plant and animals.
❖ Study of paleoecology:
The study of ancient organisms in relation to their total physical,
chemical and biological environment.
❖ Study of organic evolution: No line of evidence more forcefully
and clearly supports the fundamental postulate of evolution
descent with accumulative modifications.
10. ❖ Use of fossils in the discovery of new deposits of coal and
petroleum. Important coal deposits are normally associated with
sedimentary bed containing plant fossils deposited in lake basin
during the upper Paleozoic times in India south America south
Africa Madagascar and Australia
❖ Study of paleogeophysic:
Fossils play an important role in the study of paleogeophysics they
can be used to determine spatial relationship of the earth and the
moon, the length of days and years, earths force of gravity and
paleotides or ancient tidal force during the past.
❖ Study of paleoneurology:
Under a very resent branch paleoneurology the study of
endocranium of the fossil fauna is done basing research on
natural or artificial endocranial moulds.
❖ Micro fossils:
Microfossils data can be used in the study of palaeo currents of
sea. The presence of microfossils in shallow water sediments
which lived in deep water, Indicates a global change in the sea
level. The study of microfossils has been helpful in the evaluation
of the conditions in which petroleum deposits have been formed.
The study of microfossils is very important for petroleum
prospecting. Certain characters of microfossils like color, outer
shell composition etc. gives an idea about type of petroleum
✓ Study of fossils have been given a data about the past life
on the earth surface.
✓ By studying the these fossils will help in understanding the
evolutionary trends in life.
✓ The fossil studies gives the key to the past environment.