Permo-Carboniferous time, about
300 million years ago, was a period of great glaciation.
By
Dr. Nitish Priyadarshi
Geologist
The Earth has a history of climate change. There have been ice ages and super-volcanoes and with them came evolutionary changes in many of the Earth’s inhabitants;
A glacial period (or alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. There have been five known ice ages in the Earth's history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively. The Earth is currently in an interglacial period of the Quaternary Ice Age, with the last glacial period of the Quaternary having ended approximately 10,000 years ago with the start of the Holocene epoch.
The Permo-Carboniferous refers to the time period including the latter parts of the Carboniferous and early part of the Permian period. Permo-Carboniferous rocks are in places not differentiated because of the presence of transitional fossils, and also where no conspicuous stratigraphic break is present.
Permo-Carboniferous time, about 300 million years ago, was a period of great glaciation. The widespread distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia was one of the major pieces of evidence for the theory of continental drift and led ultimately to the concept of a super-continent, Pangaea. Glacial activity spanned virtually the whole of Carboniferous and Early Permian time . Toward the end of the Carboniferous, around 290 million years ago, Gondwana, the southern part of Pangaea, was located near the south pole. Glacial centres expanded across the continents, producing glacial tillites and striations in pre-existing rocks.
The Late Carboniferous and Early Permian period was an
exceptional phase in the earth’s history when the precursors of the modern
continents were assembled in the form of two big landmasses (Gondwana and
Laurasia) which were connected to form a supercontinent (Pangaea) such that the major part of the
land area was in the southern hemisphere. Since the Earth’s climate is
dependent on land and ocean distribution, the global air circulation and climate
were radically different from the present.
Past Glaciation evidence in Jharkhand State.
Rocks of glacial derivation are limited to the Talchir
Formation at the base of Gondwana supergroup. The Talchir, all over Peninsular
India comprises a variety of rock types including diamictite (tillite),
conglomerate, sandstone, laminated varve-like shale-siltstone (rhythmite
facies), and locally turbide deposits. The maximum known thickness is seldom in
excess of 300 m.
The sediments comprising the Talchir Formation contain
records of a chain of events caused by the climatic evolution during the
Carboniferous–Permian boundary period in India. The occurrence of a boulder
bed derived from a glacial moraine at the base of the Talchir Formation
indicates presence of glacier ice near the basin periphery. Subsequent
occurrence of sandstone–siltstone beds and their sedimentary features signify
evolution of a large water body. Different research work suggests that the water
of this basin was supplied by melting of the glacier. The glacier later
retreated far from the lake margin when sediments were carried by melt-water streams.
This development marks a relatively rapid warming episode,
which reached a climax when waves generated by intense storms created hummocky
cross-stratification in the sedimentary layers. Several Gondwana basins in
east-central India
recorded this climatic transition in the basal part of their sedimentary
sequence typified by the Talchir Formation. The warming initiated during late
Talchir continued for a geologically long time with substantial melting of ice
in various regions leading to increase in sea level as evidenced by signature
of marine transgressions (at Umaria, Manendragarh and Daltonganj). This chain of events finally culminated in
occurrence of widespread vegetation and swampy land, which formed the massive
Permian coal deposits of eastern India.
Damodar Valley basin in Jharkhand State
contains a chain of sub-basins containing a complete stratigraphic sequence of
Talchir sediments(Ghosh and Mitra,1975). An excellent exposure occurs near the
confluence of Dudhi Nala, Dube Nala, and Silai Nala about 0.5 km south of the
village Jarwa in the western part of the
Bokaro sub-basin.
East Bokaro
coalfield:
The East Bokaro coalfield
ranks third amongst Indian coalfields in the respect of coal potentiality. The
name of the Bokaro field was given by D.H. Williams in 1846-47 as the Bokaro
river flows through the field for nearly 40 km.
The Talchir formation crops out only in the north-eastern
periphery around Chapri. The Talchir formation has its base the typical
tillite, which crops out in the nala (rivulet) south east of Lakarkatwatoli
village. The tillite is practically unstratified and devoid of sandy
interbands. It usually attains a thickness of 2m to 3m. the till favbric study
in the Chapri area indicates that the inflow at the dawn of Gondwana
sedimentation was from WNW to ESE. It is therefore evident that the Precambrian
upland lying to the north of East Bokaro coalfield
was the main gathering ground of ice.
Because of the restricted distribution of Talchir beds in
the vicinity of Chapri it is surmised that only one major lobe of ice advanced
into the eastern periphery of the coalfield.
West Bokaro
coalfield :
The base of Gondwana sequence is marked by a thick pile of
glacial and periglacial deposits of Talchir Formation. The Talchir beds are
well exposed in the western part of the coalfield to the east and northwest of
Mandu in Hazaribag district and also occur as a lenticular patch north of
Tapin. The Talchir formation comprises diamictites, sandstones, shales,
turbidites and rhythmites, which are all typified by a khaki green colour. This
section lies at a distance of 68 km, from Ranchi.
The area of study lies at a distance of nearly 3 km from Mandu, off the west
side of the Dudhi bridge.
Characteristic features of glacial transport are observed in
the forms of polished and striated boulders. Unsorted nature of the deposit
also suggests their glacial origin.
Ramgarh Coalfield:
The Talchir rocks are best developed in the northern part of
the basin around the Barki Punu. A narrow strip of such rocks is also exposed
all along the eastern periphery of the basin where good exposures are present
in the Bhera river near famous Rajrappa temple.
Till fabric analysis of the basal tillites in the Barki Punu
area has indicates glacial transport from WNW to ESE which is compatible with
ice flow directions from equivalent horizons in the adjoining Karanpura and
Bokaro basins (Ghosh and Mitra,1975).
North Karanpura
Coalfield:
The North Karanpura coalfield which is the western most
member in the east-west chain of the Damodar valley basins forms a large
expanse of coal bearing sediments spread over Hazaribag, Ranchi and Palamau districts.
Talchir formation is exposed along the fringes of the basin
in the north, east and south. Tillite which is dumped type deposit comprises
out sized clasts, which vary in size from a few centimeters to a few meters.
The different occurrences of the tillites indicate that they
were laid down by different lobes of valley glaciers as abalation till or
lodgment till rather than by a continuous ice sheet (De, !980).
Glacial pavements with undisputed glacial striae indicating
ice transport from north and NW has been reported from the north of Pakri
Barwadih at the northern margin of the basin ( Chakraborty and Bhattacharya,
1973).
Auranga Coalfield:
Auranga coalfield is the easternmost of the North Koel valley Gondwana basins. It is only 8 km away
from the North Karanpura basin, the westernmost of the Damodar Valley
coalfields.
The Talchir formation in Auranga basin has a maximum
thickness of 30 m to 35 m. It is evident the ice had moved from the southern
uplands and deposited the morainic material in bedrock depression. From the
distribution pattern and their facies organization, it can be concluded that
several lobes of ice had reached this basin and deposited glacial and
fluvioglacial sediments in the bedrock depressions.
Hutar coalfield:
The Hutar coalfield is the westernmost of the Damodar-Koel
valley Gondwana basins. It is one of the four coal bearing areas in Palamau
district of Jharkhand.
The Talchir sediments in this area exposed along the
northern, south eastern and southern boundaries of the Hutar basin and they
crop out as narrow strips. Good exposure of Talchir rocks are observed in the
section of nalas (rivulets) like the Saphi nala near Unkamanr, the Deori nala
west of Barwadih and near Paisartanr, the Baheradhora nala, the Thongwa nala,
tributaries of the Saphi nala around Nawadih, the Jamtipani nala and its
tributaries and a tributary of the Jharna nala.
An analysis of till fabric, primary directional structures
and lithofacial distribution indicates that the direction of glacial transport
was mostly towards north and north-east.
Though no sub-surface information is available, total thickness of the Talchir
formation is estimated to exist 50 m.
Deoghar Basins:
Extensive exposures of Talchir rocks are noted all along the
southern margin of Jainti basin. The formation also covers a large area along
the northern boundary of the Saharjuri and Kundit Kuraiah basins. In addition,
more detached outliers of sediments have been recorded in the vicinity of
Makranda, Alaura, Alakbera, Darabandh, Satuabad and Burhai. These occurrences
of Talchir outliers testify to widespread glaciation in the Deoghar area, the
detached outliers being erosional remnants.
Reference:
Chakraborti, S.K. and Bhattacharya, B.P. 1973: A note on the
occurrence of glacial movements along the northern boundary of North Karanpura
coalfield, Hazaribagh district, Bihar, Jour.
Geol. Soc. Ind. 14(3).
Coal Resources of Bihar,
1987. in Bulletins of the
Geological Survey of India, Vol IV (part -1).
De, A.K. 1980: Lithology and conditions of deposition of
Talchir Formation in North
Karanpura Basin.
Jour. Geol. Soc. Ind., Vol.21, 593-602.
Ghosh, P.K.
& Mitra, N.D.
(1975): History of Talchir sedimentation in Damodar Valley Basins, Mem.
Geol. Surv. Ind.,105.
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