Fossils

FOSSILS
 A fossil is an impression, cast, original material or
track of any animal or plant that is preserved in rock
after the original organic material is transformed or
removed.
 A fossil may be:
An original skeleton or shell
 a mold or cast
Material that has replaced the once living things
Traces such as footprints or worm tubes

TYPES OF FOSSILS
1. Body fossil
2. Sub fossil
3. Microfossil
4. Macrofossil
5. Unusual fossil
6. Trace fossil
7. Coprolites
8. Bioclast
9. Burrow and boring
10. Gastrolits
11. Pseudo fossil

BODY FOSSIL
The fossil of hard part of organism such as
tooth, shell or bone are called body fossils.
 These occur in all shapes and sizes and
ranges from microscopic sea dweller to huge
terristial dinosaur.

SUB FOSSIL
These are remains of animals and plants
preserved in rocks less than 10000 years.
Sub fossil giant lemur

MICROFOSSIL
 These are the fossil remain of microscopic
animals and plants which usually less than
0.5mm in size.

MACROFOSSIL
 These fossils are larger and 1cm in size.
These include fossil of more advanced plant
and animal such as skeleton of vertebrates.

Eocene fossil fish Priseacara liops
from the green river formation of
Utah

UNUSUAL FOSSIL
These fossil are found by the combination of
events and conditions which result in all or
most of the organism getting preserved in the
rock.
fossil from Lebanon:- strange
creature of the sea

Waiparaconus ; an unusual fossil.
These enigmatic fossils from waipara were
long thought to be fossil barnacle stalks

TRACE FOSSIL
 These are fossils of footprints and trails left in
mud by the organism that live in the past.
Trace fossil are formed as a result of day to
day activities of the organism such as walking,
crawling , burrowing and feeding.

Gigandipus , a dinosaur footprint in lower
jurassic

COPROLITES
 These are fossils of dropping of animals or
fickel metal.
 These may vary in size from tiny fickel pallets
of sea-snail collage coprolites of crocodile,
dinasour or mammal.
 study of fossil excreta may provide valuable
information pertening the food habit of the
fossil form.

Baena turtle coprolite , North America , 50 millions
years ago

This coprolite contains several small fish vertebrae . Its overall
shape is a clue that the coprolite was made by a small shark

BIOCLAST
 These are fossils or fragment of fossil
enclosed in sediments.
Bioclastic limestone with echinoderm
fragments

Bioclastic rock primarily composed of skeletal fragments of
organism that died and settled down as sediment

BURROWS & BORING
 Some animal in the burrows , tubes and
holes in the ground , wood or rocks for
shelter or in search of food .The burrows
may be later filled with the sediment and
preserved.

Thalassinoides , burrows produced by crustacean
from the middle Jurassic

Driftwood extensive bored by “shipworm” – a marine
bivalve that burrows into wood

GASTROLITS
 These are found in abundance in the body
cavity of certain reptiles.
 these structure are believed to have being
of some use in grinding the stomach
contents of extinct reptiles.

Psittacosaurus fossil with gastrolits in its
stomach region

PSEUDO FOSSIL
 Many objects of inorganic organism closely
resembles the forms of organic origin and
are form in sedimentary rocks . These are
referred to as pseudofossils.

Mineral thought to be fossil bird head
A marcasite crystal form resembling a sand
dollar

METHODS OF DETERMINING
AGE OF FOSSILS
• Radioactive clock method
• Radioactive carbon method

RADIOACTIVE CLOCK
METHOD
 It was introduced by Boltwood in 1907.
 This method is based upon disintegrating
properties of radioactive element.

RADIOACTIVE CARBON
METHOD
 It was discovered by W.F Libby.
 This method is quite accurate for relatively
recent fossils.

Fossils

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Fossils