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CHAPTER-II
STRATIGRAPHIC NOMENCLATURE
The classification and stratigraphic nomenclature of Gondwana
'Formations' of India have been a matter of debate and revision
from time to time (Holland, 1926 and Sastry et al., 1977a). On
the basis of palaeontological evidence, Medlicott and Blanford
(1879), first proposed a two-fold classification and divided
Gondwana 'Formations,' into 'Lower' and 'Upper'. The 'Lower*
Gondwana Formation is characterized by the 'Glossopteris ' flora
and the 'Upper* by 'Ptilophyllum' flora. Top of Panchet 'Stage'
of Damodar Valley Coalfield was considered as 'transitional* and
the unconfornity above it represented a stratigraphic and pnlaeo-
ntologica] break. This bi-fold classification of Gondwana strata
is favoure.i by Oldham (1893), Cotter (1917), Fox (1931, 1934),
Krishnan (1949, 1982), Pascoe (1959), Bose (1966), Bakhshi (1967),
Ghosh and Basu (1969), Kutty (1969), Mitra (1972), and many more.
On the basis of depositional environment, previa ling climate
and occurrence of 'Discroidium' flora from Parsora Formation,
and the so-called 'transitional bed' of South Rewa, Feistmantel
(1881) adopted a tripartite subdivision as Lower, Middle
and Upper Gondwana. He also included Panchet within the
10
transitional beds, where flora findings closely resemble to
the Lower but it appears lithologically more akin to the Upper
Gondwana (Sastry et al., 1977a). The three-fold classification
was supported by Vredenburg (1914), Wadia (1926), Roychowdhury
et al., (1^12), etc. and an emphasis was given to the presence
of the red beds and Triassic reptiles within the Middle Gondwana.
They also equated this three fold classification of Indian
Gondwanas with European Standard Time Scale. Later on, some
other workers also supported this tri-fold classification
(Saxena, 1952, 1974; Lele, 1962, 1964); but the two fold
classification of the Gondwanas still holds good and more
popular amongst the stratigraphers because it has been adopted
by Geological Survey of India.
Like other countries, in India also, stratigraphers (Hughes,
1885) classified Gondwana deposits into 'System', 'Series*,
'Stage', 'Sub-stage', and the hierarchy evolved through
convention and usage. On the other hand, some workers
(Feistmantel, 1882; Oldham, 1893) used terms such as 'System',
'Series' and 'Group' to classify the Gondwana rocks of India.
However, following the publication of the Code of Stratigraphical
Nomenclature of India (1971), many workers have revised the
stratigraphic nomenclature for the 'Lower' and 'Upper' Gondwana
rock sequence. Currently there seems to be little agreement as
to the stratigraphic nomenclature scheme to be adopted in
classifying the Lower Gondwana strata. Krishnan (1949, 1982),
11
Pascoe (1959), Wadia (1961), Ghosh and Basu (1967), adopted
tiine-stratigraphic (chrono-stratigraphic) scheme, while Sen
(1965), Bakhshi (1967), Casshyap (1970), Sengupta (1970),
Qidwai (1972), Khan (1978), Tewari (1980), Kumar (1984),
besides many other classified these rocks following litho-
stratigraphic scheme of classification.
Lower Gondwana rocks of Indian sub-continent are fossiliferous
and contain plant, invertebrate and vertebrate fossils. Plant
fossils are known to have been widely distributed in the Gondwana
strata but unfortunately almost none of them is useful as 'index
fossil' in the light of our present knowledge. Whereas,
invertebrate fossils occur in few widely separated localities
(Umaria, Bhadura, Anukpur, Manendragarh and Daltonganj), These
are of little chrono-stratigraphic use, as they are restricted
to basal unit (Talchir) of Lower Gondwana sequence (Reed, 1928;
Ghosh, 1954; Thomas, 1954; Sahni and Srivastava, 1956; Ahmad,
1957; Sastry and Shah, 1964; Dutt and Shah, 1969). Fossil
vertebrates have been recorded in Bijori (Lydekker, 1885, see
Pascoe, 1959, p, 957) and Raniganj beds (Upper Permian) of
Madhya Pradesh, Panchet beds of West Bengal and Mangli beds
(Lower Triassic) of Madhya Pradesh (Tripathi and Satsangi,
1963; Satsangi, 1965; Ghosh and Sastry, 1967), These fojssils
also do not fall in the category of the 'index fossils'.
Floral and faunal content of Lower Gondwana strata can be used
to assign the probable age to respective stratum, but these
12
isolated occurrences are not suitable for subdivision of these
rocks according to the time-stratigraphic (chrono-stratigraphic)
scheme, because a properly defined chrono-stratigraphic unit,
has to be tenable throughout the continent (Ghosh and Basu, 1969;
Sengupta, 1970; Qidwai, 1972; Tewari, 1980; Kumar, 1984, etc.).
Gondwana rocks of Peninsular India, show similarities in
lithological and sedimentological characters. Recent studies
have revealed that the Gondwana sequence, cannot be assigned
a chrono-stratigraphic status, sensu-stricto, specially in the
absence of corroborative evidence of the geological time gaps,
that had elapsed from the beginning to the end of deposition
of lithounits (Ghosh and Basu, 1967). Hence, the different units
of the Gondwana strata can be best distinguished and further
differentiated on the basis of lithological characters and thus
would be in accordance with litho-stratigraphic classification.
Terms like 'System', 'Series', and'Stage' of Gondwana stratigraphy,
presently used by Stratigraphers and Geological Survey of India,
should be abandoned and litho-stratigraphic terms such as
'Supergroup', 'Group', 'Formation' and 'Member' (Article 10.06,
Stratigraphic Code of India, 1971) be used. The geographic names
used in the existing scheme of nomenclature have been retained
(Article, 12.01, Stratigraphic Code of India, 1971). The terms
•Lower' and 'Upper*, used freely in the published literature
do not find any place in the litho-stratigraphic classification
(Article, 6.00, Stratigraphic Code of India, 1971). AS the
13
present study of Gondwana rocks exposed in the south of
Ambikapur town, is focused on the sediraentological attributes
of these rocks, the litho-stratigraphic scheme of classification
which appears most pragmatic and suitable, is adopted in the
foregoing work.
There is difference of opinion regarding the stratigraphical
status of Talchir deposits. Some geologists have used the term
•Group* for this sequence (sen, 1966; Ghosh and Basu, 1969;
Das and Sen, 1980 and few publications of Geological Survey of
India), whereas, Casshyap (1977), Mitra et al, (1977), Sastry
et al. (1977a, 1977b), etc. have assigned the status of
•Formation* to Talchir rocks. Though, some workers have given,
Talchir sediments the status of 'Formation*, however, according
to litho~stratigraphic classification, it should be part of a
•Group* (Code of Stratigraphical Nomenclature of India, 1971),
If these sediments are classified as a 'Group* then they should
be sub-divided into 'Formations*, which are yet to be identified.
In the light of available evidence, it is difficult to conclude
about the exact status of Talchir strata, because it needs
surface and sub-surface geological data from the entire
sub-continent. Due to the lack of conclusive evidence and
unanimity of opinion, for the purpose of foregoing study,
Talchir sequence has been assigned the status of *Group*,
14
STRATIGRAPHY :
Mainpat area, has been selected for the purpose of present
study. This area has thickly vegetated hill slopes and
cultivated low-lands. It is very difficult to get fresh
exposures even in the drainage channels because the streams
have been danunea for water storage. Rock exposures are only
found in isolated patches. Nevertheless, all possible efforts
have been made to collect maximum amount of geological
informations. Stratigraphical sections from individual river
and nala beds or isolated hill slope exposures have been
systematically prepared. For the convenience of the work,
this area has been divided into three broad divisions, namely,
northern, southern and western sides of Mainpat ridge.
In this area, Talchir Group unconformably overlies Precambrian
rocks. The different Talchir members show considerable variation
in lithological attributes and internal sedimentary structures.
Generally, the exposures of Talchir rocks are seen in the
depressions of the uneven Precambrian basement. Owing to this,
the exposures of Talchir rocks are found at different levels.
However, in the foregoing chapter, an attempt has been made to
describe separately, the lithological characteristics of the
individual beds found in different exposures and their
stratigraphy. The studied individual sections are as follows :
15
I. Sections along the northern side of Mainpat ridge :
1. Gungntta river section
2. Lotma nala section
3. Banderkot hill section
4. Barnai nala section
5. Khiridongar hill section
II. Sections along the southern side of Mainpat ridge :
1. Koirja nala section
2. Bogudega nala section
III. Sections along the western side of Mainpat ridge s
1. Hasdo river section
2. Matin section 3. Tan nadi section
After carefully examining different field exposures of the
lithologic units made up of megaclasts embedded in unsorted
sandy/silty matrix, the non-genetic terms like the diamictite/
diamictone (Flint et al., 1960; Flint, 1971). para-conglomerate
(Pettijohn, 1957), pebbly mudstone (Crowell, 1957) or mixtite
(Schermerhorn, 1966) have been dropped in the present work.
The term 'tillite' 'indurated till' (Penck, 1906) has been
16
used for these lithofacies. The genesis and types of these
'tillite* facies have been discussed later in Chapter-VIII.
As and wherever, more than one unit of 'tillite* facies was
found, it has been inferred to as basal, facies I, II and so
on in the ascending order.
SECTIONS ALONG THE SOUTHERN SIDE OF MAINPAT RIDGE :
Gungatta River Section :
In the south of Ambikapur town (headquarters of Sarguja district,
Madhya Pradesh), rocks of Talchir Group are well exposed in the
•U' shaped channel of Gungatta river (23°2•-2 3°6'N : 83°13'-
83 15*E). In this section the total thickness of Talchir
sediments is about 130 meters.
Talchir sediments overlie the sub-glacially eroded pink granite
surface (Fig. 3), Different members of Talchir Group (Table-1),
are discussed in detail in the following paragraphs.
Basal tillite fades :
Basal tillite facies which is about 2 meters thick, is found
almost plastered on eroded uneven Precambrian granite surface.
This tillite facies is massive, poorly sorted with dull yellowish
coloured matrix. The percentage of the matrix in comparison
17
TABLE-1
Stratigraphic succession and lithologic characters of Talchir Group outlier, Gungatta river, Sarguja district
(Madhya Pradesh)
Lithologic characters Thickness(m)
Fine grained, greenish grey coloured sandstone
facies with shale and thin clayey beds, showing 15.50
ripple marks, dropstones, pseudo-mudcracks and
some other structures
Tillite facies-III 06.00
Alternating, stratified, medium to fine grained
sandstone and shale/siltstone facies (? varves) 27.00
with dropstones and occasional graded and cross
bedding
Tillite facies-Il 10.00
24.60 Intercalations of sandstone-mudstone facies,
calcareous lenses, ball and pillow structures
Yellow coloured, thickly bedded sandstone
facies with subordinate shale facies, showing 17.00
scour-and-fill structures, graded bedding and
sand dyke
Tillite facies-I 08,00
Yellowish coloured, thickly bedded sandstone
facies showing scour-and-fill structure, 20.00
dropstones with thin clayey interbeds
Basal tillite facies 02.00
Precambrian pink granite
f -
u-iT l '-
' - ' J i/> a» o rO
U .
<L>
c o TD 3
Z a>
• ^ I T
T3 e c 0
CO ' ' J3
'!'*
'•' c tJ c
(/» Jla
.i e o (
a, CL
10 J C i/)
w M
a> c </>
C Lino
cO tt' C o • J
J * «i (7) a> o iii nj ro
U . J C t / )
<1> . • i 4> =3 C
o *-• . J — • (/) <\J "O W C fO (fl cr: 3 U)
•ZL O
h-O uJ cO
cc uJ > a:
< t— H-< o -z. 3 O
Q. < Z o I Q. < a
< cc H-CO O X
_ i
ro O U-
:^ liiil
19
to boulders and other megaclasts, is very high. The embedded
clasts are heterogenous in composition. Granite of different
types contributes about 50% of the total clasts followed by
maroon red quartzite, smoky quartzite, pegmatite, mica schist,
granite gneiss, vein quartz, phyllite, dolerite, etc. Many of
these clasts are faceted and show flat iron surfaces. About 20%
of maroon red quartzite clasts bear clear and prominent criss
cross striations (PI. 1, Fig. 1).
Majority of clasts found in this tillite facies are below 2 0 cm.
in diameter but boulder up to 1 meter in diameter are also not
uncommon. Most of these clasts are sub-angular, sub-rounded to
rounded in shape. Flow direction deduced from fabric study is
almost from southeast to northwest and has been discussed in
details in Chapter-VII.
The presence of striated, faceted and flat ironed phenoclasts
of heterogenous nature, extreme variation in the grain size,
massive and compact nature of the exposure suggest that the
tillite is of glacial origin, where water has played very
insignificant or almost no role during the deposition of this
facies.
20
Yellowish coloured, thickly bedded sandstone fades showing scour-and-£lll structure, dropstones with thin clayey Interbeds :
The basal tllllte is seen to wedge out and found to grade
upward into 20 meters thick, poorly sorted, medium to fine
grained, yellow coloured sandstone fades with thin clayey
interbeds. The dip and strike of this unit is 12°NW and 225°,
respectively. This sandstone unit is thickly bedded and
thickness of individual sandstone beds varies from 70 cm. to
1.5 meters and those of clayey interbeds from 15 to 30 cm.
Clasts ranging in size from boulder to cobble, having
composition similar to those of underlying tillite are found
widely distributed in this unit. Some of these megaclasts are
faceted and bear striations. At some places these megaclasts
are found in abundance and are arranged like the conglomeratic
bands (PI. 1, Fig.2). Some scour-and-fill structures showing
graded bedding are noted in the upper part of this unit. Towards
the top of this lithofacies the fining upwards cycle is notable
that occasionally shows silty characters. The characteristic
features of this fades show much similarities with that of
deposits reported from Burhai basin, Bihar (Niyogi, 1961) and
Daltongaj Coalfield, Bihar (Sen et al., 1977).
The yellow colour and thick bedding in sandstone and presence
of clay interbeds seems to bear a close relationship with calm
and quiet fluvial (?) condition of deposition with probable
slightly higher temperatures that prevailed during deposition.
21
During the seasons of comparatively lower temperatures probably
the clay interbeds were deposited. The presence of dropstones
show that glacial front was not far away from the site of
deposition, icebergs were floating and as the ice wasted debris
were dropped and deposited.
Tillite facies-I :
The sandstone facies is overlain by tillite facies-I, which
is about 8 meters thick. Although, this exposure of tillite
facies appears massive but the presence of many small lenses
of sandstone and shale usually give vague impression of
stratification (PI. 1, Fig. 3). Boulders, cobbles and gravels
are embedded in sandy and silty matrix of greenish colour, at
some places the colour appears greyish or ashy. Matrix
constitutes about 80 per cent of the total tillite unit.
These megaclasts are generally subangular, subrounded to
rounded.
Pinkish coloured, very coarse grained to gritty sandstone
lenses, showing graded bedding are often met with towards
the top of this tillite facies. Some calcareous lenses of
variable sizes are also found enclosed in this exposure. The
absolute unsorted nature of this facies does not show any
feature which could suggest significant current action.
22
Among the lithologies of the embedded megaclasts, granite of
different types constitutes the majority, followed by maroon
red, smoky and dirty white quartzites, granite gneiss, mica
schist, pegmatite, vein quartz, jasperised conglomerate, chert,
in order of abundance. Many of these raegaclasts are faceted,
flat ironed and pentagonal in shape. Some of the maroon red
quartzite clasts bear criss-cross striations (PI. 2, Figs.l, 2)
All these characters strongly advocate the nomenclature of this
unit as tillite.
The deposition of tillite facies-I» after the sandstone facies,
show that the temperature in the area dropped and the probable
glacier advanced. However, the presence of sandy, shaly and
calcareous lenses in the upper part of the exposure indicate
that towards the end of this phase warming had started and
meltwater might have played some role in the deposition of
these sediments.
Yellow coloured, thickly bedded sandstone facies with subordinate shale facies, showing scour-and-lill structure, graded bedding and sand dyke ?
Tillite facies-I, is succeeded by 17 meters thick, stratified,
medium to fine grained and yellow coloured sandstone facies.
The thickness of individual beds varies from 1 to 3 meters. In
the lower part of this unit, grains are reasonably coarse and
show graded bedding, however, towards the top, the grain size
23
gradually decreases and have been represented by the finer
fractions. In the central part of the unit, some lenses of
coarse grained material similar to channel deposits, showing
graded bedding (PI. 2, Fig. 3) occur. The thickness of such
lenses ranges between 40 and 80 cm. and colour varies from
yellowish to earthy. In the upper part of this unit, thin beds
of greenish coloured shale are also present. Few dropstones have
also been noted in this unit.
This facies is intruded by a sand dyke (Pl. 3, Fig. 1), The
trend of this dyke is N48°S and it has nearly vertical dip.
The maximum width of this dyke is about 1.5 meter and laterally
it can be traced for about 15 meters. There is variation in the
width of the dyke in vertical section as it slightly decreases
towards the top. The intruded material is finer and brittle in
comparison to enclosing sandstone beds. This dyke is further
intruded by zeolite veins. The thickestvein of zeolite is of
15 cm. while thinnest is only of the order of few millimeters.
The possible causes of intrusion of this dyke have been discussed
in the Chapter-VI.
After the deposition of tillite facies-I, probably the
temperature started increasing and turbulent fluvial conditions
were established in which sandstone facies with scour-and-fill
structure in the form of channel deposits were developed, however,
towards the top of this unit, probable quite and calm conditions
24
similar to lacustrine, prevailed in which shale facies were
deposited.
Intercalations of mudstone-sandstone facies with calcareous lenses, ball and pillow structures i
The sandstone-shale facies is overlain by mudstone-sadnstone
facies which is about 24.60 meters thick. The individual
sandstone beds are up to 2.5 meters thick. All non-fissile
silt and clay grade sediments are considered here as mudstone
(Twenhofel, 1932), Mudstone might have originated from mud
flows (Pl. 3, Fig. 2) and presently constitutes the major
portion of this unit. Due to mixing of sandy material with
mud flows, ball and pillow type structures have developed.
The colour of this mudstone-sandstone facies appears muddy
or earthy due to the predominence of clayey material. Due to
the presence of soft fine muddy material below these beds,
the base of sandstone beds appears irregular and uneven.
f*adstone-sandstone facies show spheriodal type of weathering.
The predominence of mud in this unit suggests that the
temperature increased after the deposition of the sandstone-
shale facies and these sediments were laid in water below
the slopes of Mainpat ridge, morainal deposits laid by the
receeding glacier (?), could have blocked the channel and a
lake might have formed. The increased of water in the lake
might have exerted pressure on the walls of the lake which
25
gave way. All the material present in the lake rushed out and
deposited in the form of mudstone (finer material) and sandstone
(coarser material). The presence of sand dyke and ball and
pillow structures suggest presence some feeble tectonic activity.
Tillite facies-II :
The mudstone-sandstone facies is followed by about 10 meters
thick tillite facies-ll, having clayey or muddy/and sandy matrix.
The clayey matrix bands are grey or ash coloured, while sandy
matrix bands appear buff. These bands have irregular lense shape
and generally pinch out after few centimeters. The irregular
pinching of such lenses have given the confused pattern similar
to cross bedding. This exposure of tillite shows indistinct
bedding but some shale beds are irregularly enclosed in this
tillite facies. The individual thickness of shale beds varies
from 5 to 50 cm.
The maximum size of granite boulders found in this unit ranges
to about 2 meters in diameter. However, majority of the clasts
found in this tillite are of pebble size. The systematic
countdown, to find out the lithology of the clasts, revealed
that the boulders and pebbles of granite of different types
are in majority (V^ 55%), followed by quartzite of maroon red,
smoky and dirty brown colour (^^ 30%), gneiss, mica schist,
jasperised conglomerate, chert, shale, mudstone, etc. (*^15%),
26
Some of the maroon red quartzite clasts bear prominent
irregular, criss-cross striations on the surface. Most of
the enclosed clasts are subangular, subrounded to round in
shape and show faceted and flat ironed faces.
Pew of the mudstone, maroon red quartzite and shale boulders,
found in the basal part of this tillite unit, are crushed and
fractured along certain definite planes. One of such hexagonal
shaped shale boulder shows, two sets of stress fractures, one
horizontal and other diagonal (Pl. 3, Fig. 3). This boulder is
recemented by calcite. While, crushed pieces of some other
clasts were deposited separately but close to each other that
have been reassembled and recemented (for details see Chapter-IV)
Alternating stratified, medium to fine grained sandstone and shale/siltstone facies (Tvarvesi* with dropstones and occasional, graded and cross bedding :
About 27 meters thick alternating thickly bedded, buff
coloured, medium to fine grained sandstone and thinly
laminated, grey coloured shale/siltstone facies (? varves),
overlied the tillite facies-II. In the basal part of this unit,
sandstone beds are medium grained and quite thick (1-2 meters),
while,upwards grain size progressively becomes finer and beds
thinner. Some sandstone beds show both graded and cross bedding.
The thickness of the individual shale/siltstone beds varies from
27
50 cm. to 1.30 meters. On the exposed surface, these shale/
siltstone fades appear similar to the famous 'needle shales',
that are widely reported from the different Gondwana basins
of India (Krishnan, 1982).
In this unit of sandstone-shale/siltstone (? varves) facias,
dropstones of different sizes ranging from boulder to cobble
occur frequently. At several places due to the dropping of
these stones, the underlying beds are punctured, while lower
beds show curve due to the probable impact of overlying clasts.
Few of these dropped stones are striated, faceted and flat iron
shaped. These beds might have been deposited by a readvancing
glacier, which had given out icebergs.
Tillite facles-Ill :
The sandstone-shale/siltstone (? varves) facies is overlain
by tillite facies-III having a thickness of about 6 meters,
with crudely developed bedding characters. In this tillite
facies, striated, flat ironed and faceted sub-angular, rounded
to well rounded clasts has been recorded (PI. 4, Fig. 1). These
phenoclasts belong to different types of granite, maroon red
quartzite, gneiss, smoky quartzite, jasperised conglomerate,
mica schist, pegmatite, buff sandstone, greenish shale, etc.
The average size of these clasts is about 10 cm. and they are
chaotically embedded in dirty greenish sandy and silty matrix.
28
In this tillite facies, the percentage of the matrix is
comparatively lower than the other tillite units exposed in
this outlier but contributes to about 60 per cent of the unit.
Twisted chunks of tillite facies-II (Pl. 4, Fig. 2) sandstone
and shale/siltstone are also found redeposited in this unit.
About one meter thick gritty sandstone lense was found enclosed
towards the top of this unit which shows well developed graded
bedding.
After the deposition of different sandstone, shale/siltstone
(? varves) facies, the climate once again changed to cold and
frigid. The lower percentage of matrix, occurrence of subangular
to well rounded phenoclast with striated, flat iron and faceted
surfaces and presence of gritty lenses, provide convincing
evidence that besides glacier, water has also played important
role in the deposition of this tillite facies. With all
probabilities it could be a tillite deposited by an advancing
glacier under shallow water conditions.
Fine grained, greenish grey coloured sandstone facies with shale and thin clayey beds, showing ripple marks, dropstones, p3eudo-mudcracks,etc. :
Tillite facies-IIl is overlain by about 15.50 meters thick
sandstone facies. The colour of sandstone facies is variable
from greenish grey to dark brownish, dirty yellowish to light
pinkish, whereas, shale and clayey beds are greenish or khaki
29
green (olive green) to grey and light pinkish in colour.
Generally, shale and clayey beds are thin (2-3 cm.), while
sandstone beds are up to 20 cm. in thickness. The dropstones,
from the size of boulders to cobbles are widely distributed
in this unit. Some of the dropped boulders are quite large in
size and show post depositional spheriodal weathering. Few
sandstone beds show poorly developed cross bedding, ripple
marks (Pl. 4, Pig. 3) pseudo-mudcracks (Raza et al., 1981) and
pseudo-rillmarks (PI. 5, Fig. 1). For details, see Chapter-VI.
Occasionally, sandstone is very gritty and coarse grained but
by and large, it is medium to fine grained. Some fine grained
light khaki green coloured, hard and compact sandstone beds
show rafted pieces of greenish shale and large calcareous
nodules.
It appears that after the deposition of the tillite facies,
temperature increased, ice started receeding and melting, and
the fluvial conditions started developing. Poorly developed
cross bedding and ripple marks suggest a low energy environment
(low flow regime). The floating icebergs might have dropped the
trapped stones during the thaw. The presence of calcareous
nodules also suggest rise in the temperature.
Lotma Nala Section :
About 15 kms. in the north of Gungatta river, an outlier of
Talchir Group of rocks is exposed, in Lotma nala, a tributary
30
of Gungatta river (Fig. 4). The total thickness of the exposed
Talchir sediments is about 97 meters. The base of this
stratigraphical sequence is at 487 meters above sea level
and the succession of the various Talchir rocks is presented
in Table-2.
Basal tillite facies :
In this area, the basal tillite facies unconformably overlie
the eroded granite surface (Pl. 5, Fig, 2) of Precambrian age.
The thickness of exposed basal tillite is only about 8 meters.
Size of the clasts within the tillite very largely, ranging
from 1.5-2.0 meter in diameter to the size of a small pebble.
They occur chaotically dispersed in the buff, yellowish and
greenish, silty and sandy matrix. The tillite facies is poorly
sorted and at places stones from boulder to gravel size have
been dumped and accumulated. This type of structure appears
very similar to 'pebble nest'. At some places in this tillite
unit, coarse and fine yellowish sandstone and greenish shale
lenses have been found enclosed. The presence of these lenses
gives a false impression of bedding, otherwise it is massive.
Some dolomitic lenses have also been noted enclosed in the
upper portion of the tillite.
Composition of the clasts, which are generally subangular,
rounded to well rounded in shape, is very diversified.
31
TABLE-2
Stratigraphic succession and lithologic characters of Talchir Group outlier/ Lotma nala area, Sarguja
district (Madhya Pradesh)
Lithologic characters Thickness (m)
Drab and dull red shale facies showing cross . . QQ and graded bedding
Coarse to fine grained, yellowish coloured 10 00
sandstone facies
Tillite facies-III 05.00
Intensely folded khaki shale (needle shale) and 21 00 greenish-greyish sandstone facies with calcareous
lenses
Tillite facies-II
Reddish and buff coloured, shale and yellowish
coloured, medium grained sandstone facies
Tillite facies-I
Greyish coloured alternating medium grained,
sandstone and shale facies (? varves)
Basal tillite facies
Precambrian granite
08.00
20.00
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33
Lithologically, granite of different compositions and sizes
range from huge boulder (2 m. in diameter) to predominantly
gravel <iC=70%), followed in order of abundance by maroon red
quartzite (i= 10%), dirty white and smoky quartzite (!S2K7%),
vein quartz, mica schist, jasperised conglomerate, vesicular
basalt (= 5%) and granite gneiss ( ^ 3%). Some of the maroon
red coloured quartzite clasts of different sizes show well
developed criss-cross striations (Pl. 5, Fig. 3), deep gouges and
pits on the surface. Many of these clasts occur faceted and show
flat iron surfaces. Some of the enclosed coarse and gritty
sandstone lenses show graded bedding. In the upper portion of
the tillite exposure some greenish coloured shale beds have
also been noted. It seems that this tillite, probably, has been
deposited sub-glacially.
Greyish-coloured alternating, medium grained sandstone-shale facies (? varves) I
Basal tillite facies is overlain by about 5 meters thick
sandstone-shale facies (? varves), in this outcrop sandstone
is raediura grained. The sandy beds are thicker and darker in
colour than shale beds. Clasts of different sizes and
lithologies are randomly rafted throughout the thickness of
this exposure. Most common lithology of such rafted clasts
is granite of different compositions. This facies appears to
have been deposited in the glacio-aquatic conditions.
34
Tllllte facies-l :
About 6 meters thick tllllte facies-I, succeeds the sandstone-
shale (? varves) fades. Subangular to rounded clasts of
different sizes and shapes are embedded in the greenish
coloured, poorly sorted matrix. Pseudo-stratification is
represented by sandy-silty streaks of the matrix, otherwise
by and large, the tillite unit is essentially massive. The
matrix is finer in size in the basal part but progressively
becomes coarser towards the upper part. Composition of the
clasts includes mostly granites of different composition,
granite gneiss, mica schist, maroon red quartzite, vein
quartz, smoky quartzite, jasperised conglomerate, chert,
etc. Maroon red quartzite clasts are commonly faceted, show
flat iron and glacial striations (PI. 6, Fig, 1). Perhaps
this facies has been deposited sub-glacially.
Reddish and buff coloured shale facies and yellowish coloured, medium grained sandstone facies :
About 20 meters thick alternate beds of shale and sandstone
follow the tillite facies-I, The colour of the shale facies
is dull red and buff, while subordinate sandstone is light
yellowish in colour. The maximum thickness of single shale
bed generally 4-5 meters, whereas, individual laminae are
less than 5 cm. thick. The shale beds have alternate
35
laminations of red and buff colour. The darker red coloured
laminae, are generally thicker than lighter buff coloured
laminae. Shale beds are quite hard and brittle.
The light yellowish coloured, medium grained sandstone beds
are generally, 1-2 meters thick. In the basal part of this
outcrop, the enclosed sandy beds are pebbly in nature. The
base of such sandstone beds is wavy at few places. In some
of the sandstone beds cross bedding and graded bedding types
and poorly developed ball and pillow structures have also been
obseirved. Some drops tones are occasionally found in this unit
(Pl. 6, Fig, 2), This facies largely appears to have been
deposited in lacustrine conditions with comparatively high
atmospheric temperature,
Tillite facies-II :
Moving uphill towards the Banderkot, the shale and sandstone
facies is succeeded by 8 meters thick tillite facies-II.
Clayey and sandy matrix of ash grey colour predominates over
the clasts of variable sizes and shapes. The matrix of the
tillite is clayey in the basal part and gradually becomes
sandy towards the upper part. At some places, chunks of
greenish coloured of underlying tillite facies-I are included
in this facies. In this exposure, tillite is massive (PI. 6,
Fig. 3) compact and tough. The distribution of the clasts
36
within the tillite is very irregular and at places within a
radius of one meter, stones ranging from the size of boulder
to gravel were deposited closely resembling to pebble nest.
These nests are dominantly lense shaped and their diameter
rarely exceeds one meter. The composition of the clasts is
diverse in character and includes pink granite, smoky quartzite,
maroon red quartzite, other lithologies as yellowish sandstone
greenish shale, chert, schist, jasperised conglomerate, in order
of abundance. In about 4% of maroon quartzite clasts irregularly
developed striations have been observed. The boulders and other
clasts are generally subangular to rounded in shape.
Intensely folded khaki (greenish) shale and greenish grey coloured sandstone fades with dolomitic lenses :
The tillite facies-II is overlain by khaki green shale and
greenish, grey coloured sandstone facies with occasional
dolomitic lenses. The sandstone beds form about one fourth
of the total thickness of about 21 meters. Majority of these
sandstone beds are found in the basal part of the outcrop.
Some sandy beds, which are also noted in the upper part of
the exposure are generally, fine grained and compact in nature.
The thickness of these upper sandstone beds range from 50 cm.
to' one meter. In many sandstone beds pebbles show random
distribution.
37
The characters of the shale are very similar to the well known
•needle shales', which are reported from most of the Gondwana
basins of India. Shale facies show very thin bedding and
generally varies from 10 to 15 cm. The exposed shale facies
is very brittle and it crumbles into small pieces under a
slight tap of hammer. Here, in this area this shale outcrop
is weathered and occur in form of heap of small pieces. Calcareous
lenses are found throughout this unit of shale and sandstone. Most
of these lenses are lenticular in shape and less than 30 cm.thick.
Towards the upper part of this unit, the shale strata is
intensely folded and show mainly symmetrical, asymmetrical
and overturned types of folding <P1, 7, Pig. 1). The upper and
lower horizons of these folded beds are undisturbed and their
angle of dip is 5-8 towards the northwest. The possible causes
of such type of intense folding has been discussed in the
Chapter-VI. It is noticed that the number of calcareous lenses
has increased after the folding. This type of lithological
characters are usually found in glacio-lacustrine sediments.
Tillite facies-III :
The khaki green shale-sandstone facies is overlain by about
5 meters thick tillite facies-Ili. it is generally massive
but at some levels, traces of stratification occur (Pi. 7,
Fig. 2). The greenish coloured matrix is medium grained and
38
forms about 60 per cent of the total volume of the rock. The
boulders and pebbles vary in size from 7 to 5 cm. Most of
the clasts belong to granites, maroon red quartzite, smoky
quartzite, granite gneiss, jasperised conglomerate and mica
schist plus more rarely buff coloured sandstone, greenish
shale, vein quartz, chert, pegmatite, etc. These clasts are
generally subangular to well rounded. About 5% of maroon red
quartzite stones are faceted and bear striations, which are
generally randomly oriented and occasionally produce deep scar
on surface. Fragments of underlying tillite facies~II, sandstone
and shale, some of which are twisted, are also found enclosed in
this tillite facies.
Coarse to fine grained, yellowish coloured sandstone facies :
The tillite facies-Ill is overlain by about 10 meters thick
yellowish coloured, coarse to fine grained sandstone. This
sandstone facies is coarse grained and pebbly but coarseness
decreases progressively towards the top and passes on to shale.
The same -is true with stratification, the beds are thicker and
faintly developed in the basal part and thinner and clearly
developed in the upper part of the exposure. Graded bedding is
present in coarse fractions but poorly developed cross bedding
is noticed at many places in the finer grained beds. Dropstones
of different sizes are hapazardly distributed throughout the
sandstone facies. Some calcareous lenses are also enclosed in
this anit.
39
Drab and dull red coloured shale fades showing cross and graded bedding :
14 meters thick, drab and dull red coloured shale fades with
occasional sandy lenses overlie the sandstone fades.The colour
of- the shale is variable from drab and dull red, at some places
it also shows khaki green colour. This shale unit is very hard,
compact, brittle and highly fractured. It generally breaks into
rectangular pieces. The sandy bands are mostly in the basal part
of the unit and show graded and cross bedding. Dropstones are
rarely seen in this unit. The presence of graded and cross
bedding indicate that fades might have been deposited in high
flow regime and turbulent conditions.
Barnai Nala Section ;
Barnai nala is a tributary of Lotma nala, it starts from the
north side of Khiridongar hill and flows from further north
of the Gungatta river. Most of the Talchir rocks have been
eroded away and only few discontinuous remanents are left
(Fig. 4). The stratigraphical sequence of the Talchir strata
exposed in this nala is given in the table-3, The base of this
section noted in this area, is 500.63 meters above sea level.
The detailed description of different members of Talchir
Group is given in the following paragraphs.
40
TABLE-3
Stratigraphic succession and lithologic characters of Talchir Group outlier, Barnai nala area, Sarguja district,
(Madhya Pradesh)
Lithologic characters Thickness (m)
Khaki shale facies 10.00
Yellowish coloured medium to fine grained sandstone
facies with scour-and-fill structures *
Dull reddish coloured shale facies
Grey coloured shale-siltstone facies (? varves)
03.00
09.00
Light greenish grey coloured shale facies with Q^ QQ calcareous lenses
Greyish coloured pebbly sandstone facies 05.00
41
Greyish coloured pebbly sandstone fades :
About 5 meters thick, greyish coloured sandstone with pebbles
is the lowermost member of the Talchir Group exposed in the
Barnai nala. The pebbles are randomly distributed throughout
this exposure. Base of the sandstone is not traceable as it
is hidden under thick cover of soil. The sandstone appear
massive but are soft in nature and show limited sedimentary
structures including graded bedding and poorly developed cross
bedding (PI. 1, Pig. 3). The pebbles found in this facies are
rounded to well rounded. In composition these pebbles are of
granite, granite gneiss, vein quartz, white quartzite, maroon
red quartzite, etc.
Light greenish grey coloured shale facies with calcareous lenses )
The pebbly sandstone facies is overlain by about 4 meters
thick shale facies with few calcareous lenses. The greenish
grey and light greenish grey coloured facies has lamination
from few mm. to 20 cm. thickness. The calcareous lenses are
of clayey colour and are up to 10 cm, thick. The shale is hard
and compact and breaks into book like pieces.
42
Yellowish coloured/ medium to fine grained sandstone facies with scour-and-fill structures:
About 30 meters thick yellowish coloured medium to fine
grained sandstone facies overlies the shale facies. The
sandstone is soft and easily breakable, it appears well
stratified into beds of 10-30 cm. thickness, and is found
intercalated with calcareous beds, which are up to 10 cm.
thick. The dip and strike angles of sandstone beds near
village Arvan are 5 northwest and 160 , respectively. The
scattered pieces of different sizes and lithologies are
randomly dispersed throughout this exposure. At some places
few gritty lenses of up to 30 cm. thickness occur in the form
of scour-and-fill structure. These gritty lenses show graded
bedding. In few of such lenses many sets of graded beds are
repeated.
Khaki green shale facies :
Dark khaki green coloured shale facies succeeds the yellowish
sandstone unit. The total thickness of this unit is about 10
meters. The characteristic feature of this shale facies are
very much similar to well known 'needle shales' found in most
of the Gondwana basins of India.
43
Grey coloured shale-slltstone fades (? varves) :
The shale is overlain by 9 meters thick interbedded grey shales
and siltstone facies (? vairves). The individual lamina of shale
facies are very thin measurable generally within the range of
5 mm. The dip of this shale facies varies from 4-7 towards the
northwest.
The siltstone facies show dark and light grey colour. The
thickness of the siltstone beds increases from the base of
the unit towards the top. These siltstone beds show intense
folding, which are mainly symmetrical, asymmetrical, recumbent
and box shaped (Pi. 8, Fig. 1). The type of folding is closely
similar to the shales of Lotma nala (described elsewhere), the
upper and lower beds of these folds aie undisturbed and nearly
horizontal or showing a low iip 4-7° (PI. 8, Fig. 2). The
possible causes of folding are discussed in the Chapter-VI.
The dropstones are very rare in this facies.
Dull reddish coloured shale facies :
The shale-siltstone facies is overlain by 3 meter thick dull
reddish coloured highly weathered and decomposed shale facies.
The bedding in this unit is not clearly visible as the whole
exposure is crumbling, but on the surface of the shale,
pebbles belonging to different lithologies are found scattered
loose.
44
Banderkot Hill Section :
Banderkot is a flat topped mesa on the northern slopes of
Mainpat ridge. On this mesa about nearly 62 meters thick rocks
of Talchir Group, unconformably overlie the granite of Precambrian
age (Table-4). Talchir rocks are overlain by about 30-40 meters
thick Barakar sandstone which in turn is followed by Kamthi Beds
and Deccan Trap (Fig. 4).
In the Pasina Pani nala on the southern slope of Banderkot,
striated granite surface is exposed. The direction of the ice
movement depicted with the help of the s triations appears to be
SE-NW. Further moving upward near Parsa Kathar village rouches
moutonnfees, showing grooved and plucked granite surface are
seen. The gentle sloped side of these rouches moutonnfees face
the Mainpat ridge. On the surface of these rouches moutonnfees
striations are not clearly visible but chatter and crescentic
gouge marks are very prominent (PI. 8, Fig. 3). The direction
of ice movement inferred from these two structures also coincides
with the movement direction deduced from the clast orientation
from this and adjacent areas (Chapter-VIl) and also from striated
pavements exposed in Pasina Pani nala, Hasdo and Tan rivers
(Ahmad et al., 1976). The maximum length of the long axis of the
rouches moutonn4es, is up to 2 0 meters and show almost SE-NE ice
movement direction.
45
TABLE-4
Stratigraphic succession and lithologic characters of Talchir Group outlier, Banderkot hill, Sarguja district
(Madhya Pradesh)
Lithologic characters Thickness (m)
Deccan Trap
Kamthi Beds
Barakar Sandstone
30-40
Massive, coarse to fine grained, cream
coloured sandstone facies
21.00
Thinly laminated, jointed and greenish, grey
coloured shale/siltstone facies 0 9 . 0 0
Tillite facies-I 05.00
Alternating yellowish-greenish coloured, medium to
fine grained sandstone and greenish grey shale 22.00
facies with scour-and-fill structure
Basal tillite facies 05.00
Striated, grooved and plucked Precambrian granite
46
The detailed description of the various lithological facies
is given in tne following paragraphs.
Basal tillite facies j
About 5 meters thick basal tillite facies overlie, the
Precambrian granite, which shows striated, plucked and
grooved surfaces. The greenish coloured matrix is sandy,
unsorted and massive looking (Pi. 9, Fig. l). The matrix
occupies more than thrte fourth of the bulk. Maximum size
of the granite boulder noted in this tillite is about 2.5
meter in diameter but majority of the clasts lie between
5-8 cm. in diameter. The composition of the clasts found in
this tillite facies is highly variable. Most of these clasts
belong to granite of different types, maroon red quartzite,
granite gneiss, smoky quartzite, jasperised conglomerate,
mica schist, chert, etc. Some of the maroon red quartzite
clasts are faceted and bear sub-parallel striations on the
surface (Pl. 9, Fig. 2).
Alternating yellowish, greenish coloured, medium to fine grained sandstone and greenish grey shale facies :
Basal tillite facies is overlain by the alternating beds of
sandstone and shale facies, having a thickness of about 22
meters. General colour of this unit is yellowish and grey
47
with greenish tinge. The contact of basal tillite facies and
sandstone facies is exposed in the Pasina Pani nala near
village Parsa Khatar. Medium to fine grained, yellowish
sandstone facies shows absence of any significant sedimentary
structure. Some sandstone beds show scour-and-fill structure
in the form of gritty lenses (Pi. 9, Fig. 3). These gritty
lenses show grading of the grain size. The dropstones of
variable lithologies and sizes are found distributed generally
in sandstone beds and also noted occasionally in shale beds.
The lamination in shale facies is relatively finer than
sandstone facies. The greenish-grey shale facies is very
hard and compact. At some places shale beds become silty.
Paint traces of cross bedding are preserved in this shale
exposure. Some scattered calcareous lenses are also enclosed
in this unit.
Tillite facies-I :
The sandstone-shale facies is followed by the 5 meters thick
tillite facies-I. The tillite facies has shaly-clayey matrix,
which forms about 80% of the total volume of tillite facies.
In this exposure the differentiation of each bedding plane is
not possible, but it shows faint traces of bedding (PI. 10,
Fig. 1). Size of the clasts, which are embedded in this
tillite facies, ranges from few centimeters to 1.5 meter in
48
diameter. Bigger clasts are generally that of granite. Sub-
angular to rounded boulders and pebbles are dominated by-
granite, granite gneiss, smoky quartzite, maroon red quartzite,
vein quartz, jasperised conglomerate, mica schist, greenish
shale, chert, etc. Towards the upper part of tillite unit few
limestone beds of 20-30 cm. thickness have been recorded.
Thinly laminated, jointed and greenish grey coloured shale/siltstone fades :
About 9 meters thick green shale and light greenish grey
coloured siltstone facies overlie the tillite facies-I. The
alternate shale and siltstone facies is thinly laminated and
highly jointed. The thickness of the lamination ranges from
0,3 to 5 cm. Pebbles and gravels are randomly distributed
throughout the thickness of this unit.
Massive coarse to fine grained cream coloured sandstone facies :
The shale/siltstone facies is overlain by 21 meters thick
light yellowish or cream coloured, massive to faintly bedded,
coarse to fine grained sandstone. The basal part of this unit
is dominated by fine grained, thinly bedded sandstone and
thinly laminated shale facies. In this portion some poorly
developed small scale cross bedding is also noticed. While
in the upper part of this unit, the grain size progressively
49
increases and occasionally becomes gritty. Some calcareous
nodular structures in circular as well as oblong shapes,
having up to 20 cm. diameter are also associated with this
sandstone facies. Dropstones ranging from the size of boulder
to pebble are randomly distributed throughout the thickness
of this facies.
The sandstone facies is unconformably overlain by about 30-40
meters thick Barakar sandstone which in turn is overlain by
Kamthi Beds and Deccan Trap.
Khiridongar Hill Section :
Only one member of Talchir Group is exposed on the Khiridongar
hill. The base of this section is at 950 meters above sea level,
The maximum thickness of the exposed Talchir rocks recorded in
this area is about 30 meters (Table-5, Fig. 4).
The detailed description of the various members are as follows.
On the Khiridongar hill cream coloured sandstone, the only
member of Talchir Group, unconformably overlies the uneven
Precambrian granite gneiss. This sandstone facies is massive
to faintly bedded containing usually pebbles size clasts of
white quartzite. The sandstone is coarse to medium grained
50
TABIiE-5
Stratigraphic succession and lithologic characters of Talchir Group outlier, Khiridongar hill, Sarguja district,
( Madhya Pradesh )
Lithologic characters Thickness (m)
Kamthi Beds
BARAKAR Yellowish coloured sandstone facies 30.00
Conglomerate with white pebbles and matrix 01.00
TALCHIR Cream coloured, coarse to medium grained, -Q -Q
GROUP massive to faintly bedded sandstone facies
Precambrian granite gneiss
51
with occasional gritty lenses. These gritty lenses are found
in the form of scour-and-fill structures and show graded
bedding. This cream coloured Talchir sandstone facies is
overlain by about one meter thick conglomerate with clasts
of white quartzite, vein quartz, pink granite, dispersed in
sandy matrix.
The conglomerate bed is overlain by 30 meters thick massive
yellowish Barakar sandstone facies which in turn is succeeded
by Kamthi Beds.
II' SECTIONS ALONG THE SOUTHERN SIDE OF MAINPAT RIDGE :
Koirja Nala Section :
Koirja nala drains the southern slope of Mainpat ridge and it
joins Mand river near Dharmjaygarh. Outcrops of Talchir Group
are best seen along both banks of Koirja nala between the
village Bhojpur and Babola in the south of Dharmjaygarh
(22°31* : 83°16'). Talchir sediments unconformably overlie
Precambrian granite in this area (Table-6, Fig. 5), The base
of this section is at 32 0 meters above the mean sea level.
Basal tillite facies :
About 4 meters thick basal tillite facies unconformably overlie
the Precambrian pinkish granite, clasts of various sizes are
52
TABLE-6
Stratigraphlc succession and lithologic characters of Talchir Group outlier, Koirja nala, Raigarh district,
{Madhya Prade sh)
Lithologic characters Thickness (m)
Barakar Beds
Sandstone with boulders and pebbles 18,00
Tillite facles-I 03.00
Sandstone facies with gritty and calcareous lenses 12.00
Shale facies 11.00
Basal tillite facies 04,00
Precambrian granite
83*16'
22. 34
•r
22 31'L
FIS Sandstoiie Faciej,
{c*Vl TiUite Facies-1 l-.»i:| Sandstone Facies with
Calcareous lenses E 3 Shale Facies
Ei3 Basal Tillite Facies
[13 Precambrian Basement
0 2 4 6 8 l O M t T R E S
83*19' X 22
34'
22 31'
63*16' 63'19
FIG. 5: LITHOSTRATIGRAPHIC MAPiKOlRJA NALA
54
chaotically dispersed in a sandy, unsorted, greenish and greyish
coloured matrix, which comprises about 80 per cent of this unit.
The whole of this tillite is massive except at few places, where
the streaks of sandy and shaly material has locally given rise
to traces of bedding. The diameter of the clasts usually range
between 40-50 cm. but some show even the diameter of the order
of 1.5 meter. They are generally angular to subangular or even
rounded. Composition of the clasts is highly variable and
includes maroon red quartzite, mica schist, vein quartz,
pegmatite, jasperised conglomerate, granite, granite gneiss,
chert, etc. Some of the maroon red quartzite clasts bear
striations with random orientations (Pl. 10, Fig. 2).
Shale facies :
11 meters thick khaki green shale with occasional interbeds
of sand and siltstones overlie the basal tillite unit. The
lenticular sandy lenses are confined to basal portion of the
unit. These lenses measurable between 50-70 cm. in thickness
are generally medium grained. The shale appears almost similar
to famous 'needle shales* and breaks into small splinters with
a slight touch of hammer. The bedding is occasionally visible
specially where sandy or siltstone lenses are present (Pl.lO,
Fig. 2), but generally it occurs in the form of heaps of small
particles. At few places boulders and pebbles of granite,
granite gneiss, maroon red quartzite, etc. are seen. All these
clasts bear much similarity to those embedded in the basal
tillite. This clearly indicates that these clasts have been
55
derived by winnowing of matrix of the underlying tillite. The
siltstone is light greenish in colour, hard, compact and thinly
laminated as compared with the associated shale beds.
Sandstone facies :
About 12 meters thick coarse grained and yellowish coloured,
sandstone overlie the shale with an undulatory base. This unit
is grossly bedded. The sand beds are separated by thin
argillaceous beds. At many places gritty lenses occur in
form of cut-and-fill structure. These gritty lenses which
are about 50 cm. in width and 1.30 meter in length show graded
bedding. Some calcareous lenses are also found in the upper
portion of the unit.
Tillite facies-I :
Sandstone is overlain by about 3 meters thick tillite-I.
It is practically devoid of any stratification but at places
faint traces of bedding are developed (PI. 10, Fig. 3). The
clasts of variable sizes from boulder to pebble are set at
in an unsorted, greenish coloured, sandy matrix. The boulders
sometimes are as large as 2 meters across diameter. Most of
the larger boulders are of maroon red quartzite. Clasts found
in this tillite unit show wide range of composition, consisting
mainly of maroon red quartzite, pegmatite, jasperised conglomerate.
56
vein quartz, mica schist, granite, granite gneiss, greenish
shale/sandstone, sandstone, etc. Few maroon red quartzite
boulders and pebble show sub-parallel and criss-cross
striations.
Sandstone facies :
Tillite is overlain by yellow coloured 18 meters thick
sandstone with intercalations of shale and siltstone. The
sandstone is thickly bedded and coarse grained. Towards the
upper portion of the unit grain size and thickness of the
individual sand beds generally decreases. Sometimes, there
is an alternation of a sand bed into shale/siltstone and
again to sandstone. Boulders and pebbles of pink granite,
granite gneiss, quartzite, etc. are found dispersed throughout
this unit.
This sandstone unit forms the uppermost member of the Talchir
Group exposed in this area and in turn is overlain by Barakar
sandstone.
Bogudega Nala Section :
Bogudega nala is a tributary of Mand, and it joins the main
river east of Dharmjaygarh (22°28' ; 83°13'). The stratigraphical
section of the rocks of Talchir Group obseirved in this area is
given in table-7 and figure-6.
57
TABLE-7
Stratigraphic succession and lithologic characters of Talchir Group outlier, Bogudega nala, Raigarh district
(Madhya Pradesh)
Lithologic characters Thickness (ra)
Khaki green coloured shale facies 3.00
Sandstone facies 5.00
Thinly bedded sandstone and shale facies 8.00
(? varves)
Basal tillite facies 4.00
Precambrian granite
58
FIG. 6 ; LITHOSTRATIGRAPHIC MAP : BOGUDEGA NALA
59
The total thickness of Talchir rocks exposed here is about
20 meters. The base of the section is at 244 meter above the
mean sea level. The detailed description of the various members
is given below.
Basal tillite facies :
The lowermost member of Talchir Group exposed in this area
forms 4 meters thick tillite, Clasts from the size of boulder
to pebble are dispersed in greenish coloured sandy matrix
showing crude bedding. Clasts composition is variable. Granite
predominates over other lithologies (about 40%) followed by
granite gneiss, mica schist, jasperised conglomerate, maroon
red quartzite, black quartzite, pegmatite, chert, etc. in the
order of abundance. Some maroon red quartzite clasts bear
irregular striations. The orientation of clast in this tillite
unit is random and appears unrelated to glacial movement.
Thinly bedded sandstone and shale facies (? varves) :
Tillite is succeeded by 8 meters thick alternating thinly
bedded sandstone and shale facies. Buff coloured, medium
grained, moderately sorted sandstone shows thick bedding
measurable up to 1 meter or so. Whereas, dusky reddish coloured
shale is evenly laminated. This sequence is repeated many times.
At many places often dropped boulders and pebbles have been
noticed.
60
Sandstone fades :
About 5 meters thick sandstone facies overlie sandstone-shale
unit. Buff coloured sandstone is medium grained having individual
beds up to 60 cm. in thickness with intercalations of argillaceous
material. At few places occasional graded bedding and poorly-
developed cross bedding are recorded.
Khaki green shale facies i
Sandstone unit is overlain by 3 meters thick khaki green shale
similar to 'needle shale'. The bedding is not visible and is
noticed only in the form of heaps of particles of shale. Pebbles
are generally found dispersed on the surface.
III. SECTIONS ALONG THE WESTERN SIDE OF MAINPAT RIDGE :
Hasdo River Section s
The members of Talchir Group are ejqjosed within the Hasdo gorge,
near bridge on the Ambikapur-Katghora road, in this section,
Talchir sediments unconformably overlie the striated granite
(PI. 11, Fig. 1). The striations indicate that the ice was
moving from southeast to northwest (towards 308*^). At this
place the base of the Talchir section is at 266 meters above
mean sea level. The stratigraphical sequence of Talchir sediments
of this area, is presented in table-S, figure-?.
61
TABLE-8
Stratigraphic succession and lithologic characters of Talchir Group outlier, Hasdo river section, Bilaspur district
(Madhya Pradesh)
Lithologic characters Thickness (m)
Gritty conglomerate facies 19,00
Sandstone facies 06.00
Thinly bedded siItstone-shale-sandstone facies 16.00
<? varves)
Yellowish coloured, fine grained sandstone facies 07.00
Dusky red shale facies 10,00
Precannbrian granite
62
rg
00 N 00 <M
00 CM • M
E
l« OQ
c
tZ
e u « c O.
s
y«OHOMlV>»OA-
M
> CC
o Q < X a. <
o X Q. <
o
o X
o
(D
«S» N CO (VI
63
Dusky red shale fades :
Shale of dusky red coloured, having a dip of 32°NW and strike
285°, overlie the granite, which show very prominent striations,
caused by glacial abrasion. This unit shows well developed
bedding. The thickness of each bed varies from few centimeters
to 2 0 cm. Few boulders and pebbles are occasionally dispersed
in this unit.
Yellowish coloured, fine grained sandstone facies :
Shale is conformably overlain by yellowish coloured, fine
grained, evenly bedded soft sandstone. There is no significant
sedimentary structure except few cross bedding indicate flow of
current towards northwest.
Thinly bedded siltstone-shale-sandstone facies <? varves) :
Sandstone is conformably overlain by siltstone-shale-sandstone
facies. The alternations of siltstone-shale-sandstone occur
frequently. Individual beds range from few centimeters (of
siltstone-shale) to 1 meter <of sandstone). At many places these
alternate beds are arranged in groups,the lowermost light green
siltstone beds, gradually grade into dark greeh shale bed and
subsequently to fine grained sandstone. This facies abruptly
change to siltstone and the whole sequence is repeated many
64
times. Clasts from boulder to pebble in size with glacial
striations and facets are found rafted occasionally in this
unit. There appears little doubt that these are glacial varves
deposited in the pro-glacial lake.
Mauve coloured, fine grained sandstone facies :
Mauve coloured fine grained sandstone with well developed
bedding overlie the varves. The dip of the sandstone beds is
12 towards northwest. Thin argillaceous beds-are also seen in
this unit and are intercalated with sandstone beds. This unit
shows cut-and-fill structures. The presence of such structures
indicates that fast flowing current scoured the unconsolidated
sand bed and quickly filled it with coarser material.
Gritty conglomerate facies :
On the upstream side from the road bridge massive gritty
conglomerate unconformably overlie the sandstone facies. The
surface of the underlying sandstone unit shows signs of erosion.
Gritty conglomerate includes the sediments from the size of
boulder to gravel. The percentage of the matrix is very low.
The lithology of the clasts found in this unit ranges from
granite, granite gneiss, mica schist, pegmatite, maroon red
quartzite to the clasts of underlying sandstone and shale.
Current bedding and scour-and-fill structures have occasionally
65
been noticed in this unit. The current bedding azimuths show
that at the time of deposition of these sediments the aqueous
flow was towards northwest direction.
Matin Section :
In Matin area (22°42•-22°50*N : 82°20'-82°30«E), in Bilaspur
district (Madhya Pradesh), about 134 meters thick, rocks of
Talchir Group are well exposed, in different nala cuttings.
These rocks overlie Precambrian granite gneiss with profound
unconformity. The stratigraphical sequence recorded in this
area is presented in the table-9, figure-8.
Brief description of different members is as follows.
Basal tillite fades :
About 4 meters thick basal tillite facies unconformably overlie
the Precambrian granite gneiss. The clasts of heterogenous
composition are embedded in the brownish colour, sandy-silty
matrix, which forms about 80 per cent of the bulk rock by volume,
Subrounded to rounded clasts of granite gneiss, granite, maroon
red quartzite, mica schist, smoky quartzite, pegmatite, vein
quartz, chert, jasperised conglomerate, etc. are randomly
dispersed in almost structureless, unsorted matrix, devoid of
any feature suggestive of current action. The biggest boulder.
66
TABLE-9
Stratigraphic succession and lithologic characters of Talchir Group outlier. Matin, Bilaspur district (Madhya Pradesh)
Lithologic characters
Barakars
Conglomerate facies with white clasts
Thickness (m)
About 163.00
01.00
Buff coloured, coarse to fine grained, sandstone 27 00 facies with graded bedding and scour-and-fill *
structures
Alternate beds of deep grey sandstone-shale facies
showing graded bedding
Olive green shale (needle shales) facies
with dropstones
Greyish coloured, medium to fine grained sandstone
facies with horizontal cylindrical structures
Grey coloured, alternate thinly laminated
shale-siltstone facies
Tillite facies-I
Yellowish, greenish coloured, alternating thinly
laminated sandstone-shale-siltstone facies
Varves
20,
21,
13,
13.
07.
21.
07,
.00
.00
.00
.00
.00
,00
,00
Basal tillite facies 04.00
Precambrian granite gneiss
67
t ' i , ' , | Precambrian Basfment
l*.','\ fidsalTiiiitf Facifs ^ j Varves tV '.*J Sandttonr FACIK
t'/ti)] Till ite Faci-s- I ^Jl Shale Sitstone Facifs O Sandston* Faciet
nun] Shale Facies ["T^ Sandstone Shale Faciei CZZ] Sandstone Factet
5113 6 \f*k4r Sandstone
E 3 Dol«r(te DyKe
FIG 8 LI rMObrMATlOMAPHiC M A P MATIN ARLA
68
recorded in this tillite facies is about 2 meters along its
longest axis, but the average size of the clast is 5 cm. Some
of the maroon red quartzite boulders and pebbles show flat
ironed, faceted and striated surfaces (Pl. 11, Fig. 2). All
these characteristic features, relate and justify the use of
the term 'tillite' for this facies.
Varves :
The tillite facies is overlain by about 7 meters thicK varves,
which show light and dark reddish coloured bands. The thicker
bands are darker in colour and coarse grained as compared to the
thinner bands. However, in the lower portion of this exposure the
colour of the varves is olive green. Some bands also show deep
greyish and clayey colour. The thickness of these bands, varies
between 1.5 cm. to 5 mm. Dropstones are not uncommon but generally
retain the size of pebbles. In a sample collected from this facies
prominent small scale penecontemporaneous micro-faults have been
noted (PI. 11, Pig. 3). A dolerite dyke is also found intruded in
this facies.
Yellowish, greenish coloured, alternating thinly laminated sandstone-shale-siltstone facies :
About 21 meters thick alternating, thinly laminated sandstone-
shale-siltstone facies is exposed in Bakramora nala and near
village Nawapara. These alternate beds of sandstone-shale-
siltstone, are yellowish and greenish in colour. In this
sequence the sandstone lies at the base followed successively
69
by the repeated sequence of shale and siltstone. The type of
sedimentation could easily be called as 'cyclic sedimentation*
(Allen, 1964a, 1965c). The thickness of fine to medium grained
sandstone beds is variable from 15 to 70 cm. The yellowish
coloured sandstone beds show graded bedding, poorly developed
ripple marks and cross bedding. The khaki green coloured shale
beds varies between 15 to 30 cm, and of siltstone generally
less than 15 cm. in thickness.
Tillite facies-I :
The sandstone-shale-siltstone facies show sharp lithological
change from fine grained, thinly bedded to very coarse grained,
vaguely bedded, 7 meters thick tillite facies. The clast size
in this tillite unit varies generally from boulder to gravel.
Composition of these clasts substantially includes, granite
gneiss, granite, maroon red quartzite, jasperised conglomerate,
mica schist, smoky quartzite, yellowish sandstone, green shale,
chert and few boulders of basal tillite facies. There appears no
distinct bedding except at some places the presence of coarse
grained sandstone lenses give vague impression of bedding. These
sandstone lenses are devoid of any sedimentary structure and can
be measured up to 30 cm. in thickness.
70
Grey coloured, alternate, thinly laminated shale-siltstone fades :
13 meters thick, greenish grey shale and grey siltstone facies
overlie, the tillite facies-I. The shale beds are between 1 and
3 meters thick, while the interbedded siltstone appear relatively
thinner. This unit is devoid of any prominent sedimentary
structure except few dropstones and poorly developed cross
bedding.
Greyish coloured, medium to fine grained sandstone facies with horizontal cylindrical structures :
The shale-siltstone facies is overlain by 13 meters thick,
medium to fine grained sandstone facies of deep greyish colour.
The thickness of individual beds are measurable up to 1.25 meter.
This unit of sandstone shows some sedimentary structures such as
graded beds, and poorly developed cross bedding. The horizontally
disposed cylindrical structures (PI. 12, Figs. 1, 2), are of
special interest (discussed in Chapter-Vl). At places fragments
of greenish shale from 1 to 5 cm. in size, have been found
rafted in the sandstone beds.
Olive green shale with dropstones j
About 21 meters thick shale facies succeeds the greyish sandstone
facies. This shale facies is olive green in colour and crumbles
into small splinters with a slight touch of hammer. This facies
shows characters similar t6 well known 'needle shales', which
71
are reported from most of the Gondwana basins of India (Krishnan,
1982). Almost parallel laminations have thickness between 0.8 mm
and 2 cm. Few sandy and silty lenses are also found enclosed in
this unit. At places dropstones of variable sizes and lithologies
are noted in this unit, largest size of such clast, is of a boulder
of maroon red quartzite (about 2 meters in diameter) bearing criss
cross striations.
Alternate beds of deep grey sandstone-shale facies showing graded bedding :
Repeated alterations of sandstone and shale facies overlie,
the olive green 'needle shale' facies, having a total thickness
of about 20 meters. The sandstone is massive but at places it
shows very thin laminations. The beds of sandstone show graded
bedding and by and large the size grading start from the base
of the sandstone bed with gradual decrease in grain size towards
the top passing on into shale. The shale facies is thinly
laminated and show numerous joints and break into small pieces
with a slight tap of the hammer.
Buff coloured, coarse to fine grained, sandstone facies with graded bedding and sGOur-and-£iIl structures ;
The uppermost member of Talchir Group found in this outlier,
is about 27 meters thick, buff coloured, coarse to fine grained
and thickly bedded sandstone facies. The maximum thickness of
72
individual beds is about 3 meters. Well developed graded
bedding poorly developed current bedding have been recorded
in this unit. At few places lense shaped, scour-and-fill
structures have been recorded. The coatse material, which
forms these lenses shows grading in grain size.
Conglomerate :
Sandstone unit is overlain by about 1 meter thick conglomerate
band. This conglomerate is highly charged with the clasts of
white quartzite, vein quartz, granite, chert, granite gneiss,
schist, etc. The percentage of the matrix is very low in this
conglomerate.
This conglomerate unit is overlain by Barakar Sandstone which
forms perhaps the transition zone between Talchir and Barakar
Groups in the absence of Karharbari. The thickness of the
Barakars exposed in this area is about 163 meters.
INTRUSIVE I
About 2 meters thick dolerite dyke is found intruded in the
varves. This dolerite dyke is exposed in the channel of Tan
nadi. Due to the affect of the dyke intrusion, the varves are
metamorphosed.
73
TAN NADI SECTION :
Tan is a tributary of Hasdo river. The members of Talchir
Group are exposed in this nadi (22 37* : 82 36') along the
upstream side of bridge on Kathghora-Ambikapur road. In the
river bed shales and sandstone with boulders and pebbles
overlie striated granite surface. The beds are dipping at 8°
towards northwest and the base of the shale is at 300 m above
the mean sea level. The total thickness of Talchir rocks is
about 18 meters.
This striated pavement reported by Ahmad et al. (1976), has
whalebacks, chatter marks and crescentic gouge marks and all
these features indicate that the movement of ice was towards
northwest (298°).
