Power point is prepared for UG students of Botany based on Paleobotany- Fossils and Fossilization. Dr Mangesh Dagawal, Head , Department of Botany , Smt. Radhabai Sarda College, Anjangaon Surji Dist. Amravati.

1. PALEOBOTANY
FOSSILS AND FOSSILIZATION
( UNIT-I - B.SC. SEM-II )
Dr. Mangeh Dagwal
Head
Department of Botany
Smt . Radhabai Sarda College, Anjangaon Surji
Dist. Amravati (MS)
mdagawal@gmail.com
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2. FOSSILS
• Paleoboatany- Plant life of geological past.
• Remnants of past called fossils.
• Record of former life.
• Fodere- to dig up
• Imprint of nature in womb of earth.
• Fossils included remains of whole organism or
some part.
• Preserved remains or traces of an organism that
lived in the past.
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3. Fossils
• Process of fossilization
• Whole organism buried alive or after death
without decay.
• Conditions- in bogs with very cold or acidic water and low
O2 supply stop decay.
• The kinds of tissues composing the plant
• The conditions to which they were subjected
preceding and during fossilization.
• In fact, there is no limit to the length of time
cutinized parts may retain their identity.
• The disintegration of plant tissues proceeds
according to a rather definite selective order of
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4. Fossils
• First to disappear are the protoplasmic contents of the
cells.
• Second Factor influencing the extent of tissue
preservation is the intensity and duration of the
destructive forces to which the plant is subjected before
it becomes covered to a sufficient depth to prevent
decay.
• The ideal environment for the preservation of plant
material is an enclosed or protected body of water such
as a small lake or swamp.
• A low oxygen content and a relatively high
concentration of toxic substances also retard decay.
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5. • Some protection from high winds and an
absence of strong currents is essential, because
Intensive wave action or rolling boulders will
soon reduce even the most resistant plant
tissues to pulp.
• The depth of water in to which plant material
sinks is important from the standpoint of both
decay and mechanical destruction
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6. • Sand & mud brought by river deposited in form of layer.
• sedimentation.
• Deposits protect plant.
• Similar layer form at bottom of sea or lake
• Layer one above other lower layer under weight of upper
under pressure of water.
• Pressure compressed – gradually hardened in stony rocks.
• Proteoplasmic content disappear ,soft parenchyma cell also.
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7. Preservation Methods
• 1. Unaltered remains (rare)
Soft parts - entrapment of organisms in amber or oil seeps
Hard parts - unaltered shells, bones, or teeth
• 2. Permineralization –
Minerals deposited in pore spaces (such as in wood and
bone) and may become permineralized: also called
petrification.
 Skeletal material may be the original, replaced, or
recrystallized.
 Common permineralization agents –
 calcium carbonate (CaCO3), silica (SiO2),
 pyrite (FeS2), and dolomite (CaMg(CO3)2).
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8. 3. Recrystallization –
 Original material is recrystallized into a
more stable form.
 No new material is added or taken away.
This method of preservation is hard to
identify.
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9. 4. Replacement –
New material replaces the original skeleton; common
replacement minerals includes calcite, quartz, and pyrite.
Mold - skeletal hard part dissolved resulting in a hole in the
rock.
Internal molds preserve the internal structure.
External molds preserve the external structure.
Casts - new material fills in natural molds, forming a replica of
the original skeleton.
5. Carbonization –
Heat and pressure degrade original materials leaving a thin
film of carbon in the shape of the organism, this can preserve
fine details and soft parts.
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10. • Mold - skeletal hard part dissolved resulting in a
hole in the rock.
• Internal molds preserve the internal structure.
• External molds preserve the external structure.
• Casts - new material fills in natural molds,
forming a replica of the original skeleton.
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11. Theory
Replacement theory
• Fossilization takes place by replacements of
molecule of original material of plant one by
one of mineral in soil
Infiltration theory
• Fossilization as result of infilteration and
precipitation of mineral through cell wall
• Carbon converted to carbonate by reacting
with infiltered calcium and magnesium.
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12. TYPES OF FOSSILS
IMPRESSION
COMPRESSSON
PETRIFACTION
CAST
MOULD
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13. Impression
• Fossils formed from flat, dorsiventral plant body (
leaves or sporophylls).
• Common form found in various types sedimentary
rocks- shale, sandstones, limestone.
• Represent imprint of plant part.
• Original organic matter has been completely
destroyed.
• Plant part fall near site of sedimentation or
transported immediately covered by layer of
unconsolidated sediment or mud.
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14. • This covering protected some extent.
• Before consolidation of sedimentary layer
could takes place the plant part underwent
compression due to the overlying sediments.
• Fungal and bacterial activity set in and
organic matter destroyed.
• Latter due to evaporation , consolidation of
sedimentary layer took place leaving the
imprint of plant part.
• Leaves most common organ to be preserved.
• E.g. Leaves of Glossopteris.
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17. COMPRESSION
• Second most common type of fossil.
• Important paleobotanically than impression.
• Gives more information.
• Site and process for fossilization same.
• Organic matter preserved and in altered form.
• Plant part fell and covered by fine grained
sedimentary layer.
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18. • No decomposition by bacteria and fungi.
• Water and various gases expelled from tissue.
• Flatening of plant part.
• Well preserved in clay and shales.
• Coal is an ideal type of compression.
• E.g. Glosopteris occurs in Gondwana strata.
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20. PETRIFACTION
• Yields considerable information.
• Original plant material is very well preserved.
• Allows sectioning and examination of internal
structure.
• Resembles rock.
• Plant material impregnated by minerals in the
form of solution.
• Latter on consolidated form solid stone like
structure.
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21. • Silicates – silicon dioxide and carbonate-calcium
& magnesium.
• Size and shape of plant part not undergone
alternation.
• Gives 3 D idea of original part.
• Mineral solution infilterated plant tissue.
• Cell content and intercellular spaces are replaced
by minerals.
• Reistance plant tisue- Tracheids, fibres, and
vessels.
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