This slide-share focuses on Geology of Maharashtra.Different varieties of Deccan trap Basalt & its application in civil engineering field.

1. Dept. of MBA, Sanjivani COE, Kopargaon 1
Advanced Engineering Geology With Rock
Mechanics
( T.Y. B.Tech. Civil – PE- 314 Elective )
Unit- I
1.2 Geology Of Maharashtra
Sanjivani College of Engineering, Kopargaon
Civil Engineering Department
Prepared By:
Dr. A.V. Deshpande
Ph. D (Geology), M.Tech (Env.Engg.)
Asst.Professor Civil Engg.Dept.
www.sanjivani.org.in

2. Geology Of Maharashtra
 Mostly follows stratigraphy of Peninsular India
 From bottom to top stratigraphy Unconformably
overlain by one another
Deccan Trap (Cretaceous – Eocene)
Infratrappeans (Cretaceous)
Gondwanas (Upper Carboniferous – Cretaceous)
Vindhyans (Late Pre Cambrian to Early Cambrian)
Kaladgis (Pre – Cambrian)
Dharwars (Pre – Cambrian) Archaean
Eparchaean
Unconfirmity

3. DECCAN TRAP

4. Deccan Trap
 Lithology
 Either vesicular or amygdaloidal Compact
 Also found rhyolite, granophyres, nepheline syenite
 Structures
 Generally horizontal
 Dip 50 to 100
 Columnar jointing
 Found as dykes in part of Gujrat, Narmada Vally Konkan
& NW Maharashtra
 Gentla folding – Satpura Region
 Faulting – some place of M.P.

5. Deccan Trap
 Classification
 Into three group
Upper Trap (450m) West coast of India Flow with
Intertrappean beds &
beds of volcanic ash
Middle Trap (1200m) Central India Flow with Intertrappean
beds & no beds of
volcanic ash
Lower Trap (150m) M.P. Flow with Intertrappean
beds & rare beds of
volcanic ash

6. Deccan Trap
 Occurrence or Distribution
 Found in Maharashtra, Gujrat, M.P., Karnataka, A.P.
 Economic Minerals
 Gemstones, Bauxite, Quartz, Amethyst, Agate&
chalcedony
 Building Stone
 Besaltic Origin
 Dence, durable, hard, tough, wearing resistance & black
in colour
 As rode stone
 As aggregate in cement concrete
 Economic Importance
 Black cotton soil
 Good aquifer – vesicular & highly jointed lava flow

7. Types of Deccan Trap
 Giant Phenocrysts Basalt
 Phenocrysts of Plagioclase
 Up to 1cm
 At places 5 to 10 cm
Phenocrysts of
Plagioclase
Ground mass

9. Types of Deccan Trap
 Solid or Compact Basalt
 No empty cavities
 Flow Compact basalt
 Occurs as thick extensive Flow
 Tabular flow
 Top & bottom plain Surface
 Lateral extend large – up to 20 km
 Thickness varies - may up to 70 km

11. Types of Deccan Trap
 Vesicular & Amygdaloidal Basalt
 Empty cavities
 Cavities filled
 Usually occur 1 km lateral
 Up to 10 m thickness
 Low than compact basalt
 Rock are unjointed

14. Deccan Trap Basalt
Compact Basalt (C.M.):
Field characters of compact basalt: Compact basalt is black or bluish black in
colour & free from gas cavities. vertical section of compact basalt shows following
characters,
It is very thick & extensive.
Its thickness varies from 7 m to 125m .
Laterally it is can trace up to 20 km.
Top surface is almost horizontal with some minor undulation.
Immediately below top surface for some thickness it becomes hydro thermally
altered, as gases cannot escape in that portion rock becomes vesicular,
amygdaloidal basalt.
Middle & lower portion of some flow is always black & compact in nature. it is
always dissected by joints.

15. Compact Porphyritic Basalt:
This is one of the major rock type where porphyritic texture is present in which the
phenocryst is (when phenocryst is giant 2 to 10 cm) Giant porphritic basalt
plagioclase mineral.
The sub verities can be recognized on the basis of no. of nature & size of
phenocryst.
The common phencryst is plagioclase, but in Thane, Sal bardi (Vidarbha), Diva Chat
and in Meighat area the phenocryst is Augite in nature.
In C.P.B. the shape of phenocryst may be lathe shape, stumply as seen in warje
area (Pune), Accrcular (Needle like) or may be floret shape. The floret shape C.P.B
is occurring at Alwani, & Vaitarna dam sites in M. S.
The C.P.B. becomes Giant Porphyritic Basalt when length of phenocryst is more
than 2 cm & depending upon the variation in the ground mass two types of G.P.B.
are recognized namely Donragaon, Aurangabad type.

16. B) Amygdaloidal Basalt:
This rock type shows vesicular structure & vesicles are filled with quartz, zeolite,
calcite which are in the form of secondary minerals.
A.B. type and its sub varieties are recognized on the basis of no. of vesicles, nature
of infilling material & on size, shape of the infilling material.
The common minerals present is zeolite. In nature 26 varieties of zeolites are
occurring which are opophyllite, stiblite, Natrolite, Henlandite etc. in addition to this
varieties of quartz like agate, Chalcedoney are also occurring.
The no. of vesicles & thus no. of amygdals are also seen to be varying from place to
place.
In Nashik & northan dist. of Maharashtra no. of amygdals are more. Also the
vessicals are more or less spherical in shape and show zeolite as secondary mineral.
AB belonging to Aurangabad & other dist. consist of less no. of amygdals and
sometimes quartz may be seen as secondary mineral.

17. Filed characters of amygdaloidal basalt flows :
A.B. in general having irregular form.
Small quantity of highly viscous lava was outpoured this flows at lower level are
connected with tail like intrusions. Through which lava was out poured.
Another peculiarity of A.B. is that they are vascular & amygdaloidal throughout
the thickness
Another peculiarity of A.B. when it is fresh it is always in unjointed & occurs as
homogenous rock.
Those vesicles present most of them are filled up with secondary mineral even in
vesicle are empty they are not interconnect or vesicular amygdaloidal basalt may
be porous between it is perfectly impervious due to unjointed impervious layer if
provide suitable media for foundation of dam or craving tunnel & creating power
houses.

18. C)Volcanic Breccia:
These flows of Volcanic breccia have very irregular form at place it reaches
down at place it shows virgin.
It flows very slowly. In addition to this lava has to flow along loose fragment of
rock after the eruption. Therefore it never acquire uniform shape.
Volcanic breccia is very heterogeneous type of rock. In which rock fragments
are held together in diff. binding material. On the basis of matrix material
volcanic breccia is group in to three categories,

19. D) Tachylitic Basalt :
This word is derived from latin word Tachylyte means Glassy.
Tachylyte is very similar to Basalt in all respect except the rapid cooling.
Degree of crystallization is very poor due to rapid cooling and the peculiarity of T. B.
flows is their occurrence in the discontinuous manner in the form of lenses and pockets
between two basaltic flows.
These flows sends tail & tongue like intrusions in the overlaying & underlying flows.
TB is very much hard in the confined state but when exposed to atmosphere turn into red
bole material.
When fresh it is Black sometimes Red in colour even if it submerged for longer period of
time does not disintegrate into Red Bole Material. Deposits of T.B. are occurring in the
Manjra river in Latur dist.

20. Origin of red tachylite basalt : Give a details account of origin of Tachylyte.
Discuss old and new theories about the origin of tachylyte supported with case
history.
Characters of tachylite basalt :
From due to rapid cooling of basalt magma.
Texture is nearly glassy
Mineral composition is same as basalt.
Black, red, green in colour.
Shows luster when fresh.
Origin of red tachylitic basalt :
Generally in roads cuts & railway cuts thin red bands are seen
which are commonly called red bole bands.