3. Introduction
Geosynclines refers to thick pile of sediments that
were deposited in a deep marine basin & subsequently
compressed, deformed& uplifted in to a mountain range
, with associated volcanism .
The filling of a geosynclines with tons of sediment is
accompanied in the late stages of deposition by
folding, and faulting of the deposits.
Intrusion of crystalline igneous rock and regional
uplift It is then transformed into a belt of folded
mountains.
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4. History of geosyncline
The geosynclinal concept first developed by
American geologists James hall & J D Dana during the
studies of Appalachian mountain.
They 1st
to convince the ideas of sinking
Geosyncline&their relation to orogeny
Dana was 1st
to use the term geosyncline
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5. Cont…
This concept was later developed E Haug (1900)
in Europe with some modification.
Haug also established the existence of geosynclines
in the regions of the present day mountain ranges.
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6. Types of geosynclines
Broadly geosynclines are classified in to two:
Orthogeosynclines
Parageosynclines
Ortho geosyncline: These are elongated basins which
become filled with very great thickness of sediments,
which is subsequently deformed to form a fold
mountain chain. These are divided in to two:
Eugeosyncline
Miogeosyncline
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7. Eugeosyncline:
These are found far away from continental crust. In
these geosyncline, the pile of sediments are found with
an abundance of volcanic rock; these are formed at some
distance from the shield area.
Eugeosynclinal rocks include thick sequence of grey
wack,chert,slate and sub marine lavas. Here the
deposits are more deformed and metamorphosed and
intruded by small to large igneous plutons.
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8. Miogeosynclines: A miogeosyncline develops along a continental
margin on continental crust and is composed of sediments with lime
stones, sandstones and shale.
The occurrences of lime stones and well-sorted quartz, sandstones
indicate a shallow-water formation, and such rocks form in the inner
segment of a geosyncline.
Modern examples include the continental shelf of the northern Gulf
of Mexico and the Atlantic coast of North and South America.
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10. 2.Para geosyncline: it is an opeirogenic geosynclinal
basin located within a craton having oval in
shape. It is less active than eugeosyncline and
having shorter lifes. Para geosynclines are
again divided in to 3.
Exogeosyncline
Zeugogeosyncline
Autogeosyncline
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11. Exogeosyncline: It is a parageosyncline that lies along the
cratonal border and obtains its clastic sediments from erosion of
the orthogeosynclinal belt outside the craton. It is also known as
delta geosyncline.
Zeugogeosyncline: A geosyncline in a craton or stable area,
within which is also an uplifted area, receiving clastic sediments.
Also known as yoked basin.
Autogeosyncline: It is a parageosyncline located as isolated
depositional centre within a craton and gave sediments from distant
cratons.
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14. Charles schuchert(1923)has recognized three
types of geosynclines
monogeosyncline: This is a long relatively narrow
sinking structural basin, similar to that postulated by Dana
&Hall situated either with continent or just on its borders. A
monogeosyncline gives rise to a single mountain ranges.
eg:appalchian geosyncline of America.
CHARLES
SCHUCHERT(1923)
classification
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15. Polygeosyncline: This is a complex of a
number of monogeosyncline whose axes are more
or less parallel to each other. Polygeosynclines are
relatively wider, long enduring & give rise to
mountain ranges.
e.g.: rocky mountain orogeny
Mesogeosyncline: This is a complex of
several monogeosyncline whose axes not parallel
to each other. They are very narrow elongated
mobile ocean basin bordered by continents.
e.g.: The Himalayan orogeny
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17. Geosynclinal Theory
According to geosynclinal theory
Folded mountain originate in three phases over a very
long period of time of millions of years.
1.geosynclinal phase(evolution of geosyncline)
2.tectonic phase( revolution of geosyncline )
3.orogenic phase( collapse of geosyncline)
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18. Geosynclinal phase
formation of geosyncline & accumulation of
sediments in an elongated lens-like shape to
estimated thickness of 10000 to20000 m. As the
sediments get accumulated the floor of the
geosyncline begin to subside due to continuosly
increasing weight on it.
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19. Tectonic phase
when the sediment become deeply
buried in considerably warmer zone, their
strength gets reduced by heat & pressure and
become plastic and yield to deforming
compressive forces by folding.
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20. Orogenic phase
The elevated foreland slowly encroach on
the geosyncline like the jaws of a vice exterting
great horizontal compressive force on the
sediments. By this sediments get further folded
followed by igneous activity, emplacement of
dikes & batholiths and upheaval give rise to
mountain ranges of tens of thousands of meters
elevation.
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21. conclusion
Geosynclines is a subsiding linear trough that was caused
during accumulation of succeeding sediments and volcanic
rocks.
sediments were deposited in a deep marine basin &
subsequently compressed, deformed& uplifted in to a
mountain range , with associated volcanism .
The geosynclinal theory is of fundamental importance to
sedimentation, petrology, geomorphology, ore deposits,
structural geology, geophysics, and in fact all branches of
geological science.
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22. B S Sathya narayanaswamy (1994), structural geology , Dhanpat rai and sons
publications, p.p-168 to 170.
Girija bhushan mahapatra (2008), A text book of geology(with special
reference to India), cbs publications
,p.p-30 to32
• L U De Sitter (1956),structural geology, McGraw hill book company,p.p-
349-355
• Jean Aubouin(1965),geosyncline,ELSEUIER publisher company,p.p-18-
19,26-29
• Websites
www.goole.com
www.wikepedia .com
reference
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