Palaeozoic Geology Of India 1n707

THE PALEOZOIC ERA AT A GLANCE

SALIENT FEATURES OF PALEOZOIC ERA

Started at about 542 Ma and lasted for ~290 My and culminated at about 252 Ma Occupies ~6% of the total time of the life of the earth Provides better geological environment for coal formation which is the main source of energy Suitable time for organic evolution (both flora and fauna) Rocks are less deformed and hence provide good sections for research In India, Paleozoic rocks occur mainly in the Himalayan region and that too most of them in the Tethyan basin, extending from Kashmir in NW to Bhutan in the east. Apart from this, grabens in peninsula too preserve Paleozoic rocks

Rocks of Paleozoic Era have been exposed in different isolated basins along the Himalayan regions. It is thought that an earlier single basin has been divided into many due to deformation and erosion The stratigraphy of the Himalayan terrain was worked out mainly based on observations made during traverses along the river sections across the mountain ranges Due to difficulties in terrain accessibility, inadequate thickness, lack of habitations for the formations to be named after, only regional lithostratigraphic nomenclature have been adopted.

Tethyan Basin It comprises the Paleozoic and younger sediments in the Himalayan domain, north of the Main Central Thrust (MCT) and its analogous extent from Kashmir in the NW to Arunachal Pradesh in SE.

The Kashmir, Bhadarwah-Chamba, Zanskar-Spiti-Kinnaur, Gharwal-Kumaun, NepalSikkim-Bhutan-Arunachal Pradesh are the individual segments of the vast spread Tethyan Basin. Conspicuous feature in this area are unconformities at Late Cambrian, Late Carboniferous and Middle Permian

Kashmir sub-basin: It trends NW-SE and covers 18,000 km2 area and is separated from the adjacent Spiti-Zanskar sub-basin by crystalline rocks. The Lidder valley forms a part of the sub-basin and is situated in the SE part where an excellent section of the sub-basin has been exposed as Lidder anticline composed by Paleozoic as well as Triassic sequence.

Bhadarwah-Chamba sub-basin: It lies SE of the main Kashmir sub-basin. It exposes the Permo-Triassic sediments overlying the Panjal volcanics

Spiti-Zanskar and Kinnaur sub-basin: The Paleozoic and Mesozoic sequence in the south Ladakh of J & K and Spiti and Kinnaur area of Himachal Pradesh occur in two isolated synclinoria. These two isolated basins were together and later separated due to erosion of the central structural axis. The Spiti-Zanskar basin of the Indus Himalayas exposes a spectacular section.

Anticlinal valley

Gharwal- Kumayun Tethyan Sub-Basin: It is mainly seen in the Malla Johar and northern Kumayun area. This sequence composed of a thick sequence of Proterozoic and Phanerozoic rocks. But the most significant features of the area is, though the basins are situated close to each other, but the thickness of sediments from one place to other vary considerably and it is probably due to the effect of paleogeography of the region.

PRECAMBRIAN-CAMBRIAN BOUNDARY

Precambrian-Cambrian boundary is marked by major biotic changes (emergence of softbodied Ediacaran fauna and their subsequent extinction, emergence of fauna and their hard part or chemical changes, particularly variation of C and Sr isotopes in carbonates). These evidences are used to correlate the terminal Proterozoic and Early Cambrian strata Nutrient Enriched Water mass (NEW) with high level dissolved phosphate and silica with low level of oxygen left a clear imprint in fossil record in the Pc/C boundary Explosion of life in the Pc/C boundary saw variety of animals as builders, binders and encrusters in various build-ups. Around 544 Ma during the Early Cambrian, there was an evolutionary explosion called “Cambrian Big Bang” which extended up to Middle Ordovician.

But some people by the study of nucliotide (an organic matter constitutes Purine and Pyrimidine) sequence studies, put the origin and diversification of major phyla between 1000-2000 Ma. But lack of fossils to the theory is probably s the origin of organism as soft bodied. Stromatolites: Stromatolites are blue green algae. These are believed to be present in the world at 3.77 BY ago. In India these have been reported in rocks from Sandur, Simoga, Chitradurga in Karnataka state dated 2.9 BY. These are not body fossils , these are the sedimentary structures build by bacteria (cyanophytus and microscopic algae) and only rare do they contains remaining of organisms.

These are also reported in Raisi Group of Jammu Himalayas,, Gharwal-Kumaon Himalayas, Himachal Himalayas, Nepal, Sikim, Arunachal Pradesh Himalayas. In all the reported places both in peninsular and Extrapeninsular, the stromatolites represent Precambrian sequences except in Tal Formation of Uttarakhand, where stromatolites occur in Early Cambrian Pc/C Boundary in The Himalayas

The sedimentation of the terminal Proterozoic-Cambrian succession commenced with a wide spread marine transgression in response to global warming after the Varangian glaciation at about 610-590 Ma. Salkhala Group and parts of Haimanta Group represent Neo-and Terminal Proterozoic in Lahaul-Spiti and Himachal Himalayas. The transgression was terminated by the Pan-African orogeny in Late cambrian. The sediments are now exposed in Krol belt, Lesser Himalayas, in Kashmir basin in Higher Himalayas and Spiti-Zanskar and Kumayun basins. Blainia-Krol-Tal sequence is considered as the standard Pc/C boundary in the Himalayas which can be correlated with global standards

Cambrian stratigraphic sections with ages of strata and positions of trilobite fossil recovery. Data source: 1 —Garzanti et al. (1986), Myrow et al. (2006a); 2—Brookfield (1993), Myrow et al. (2006b); 3—Kumar (1985), Brookfield (1993); 4—Zhang (1988); 5—Searle et al. (2003). Inset map shows position of sections and adjacent tectonic zones.

Pc/C boundary in Rajasthan The Nagaur-Ganganagar evaporite intra cratoinc basin exposes marine sediments of Late Precambrian-Cambrian age over the basement of Malani volcanic suit between Kalu and Kaksar Over the Malani volcanic suit, the evaporites of Jodhpur, Bilara, Hanseran evaporites represent Terminal Proterozoic, which is followed by Birmania Formation of Cambrian age. In the Himalayas, the Pc/C boundary is well known but in the Aravali-Vindhyan belt it is tentative

PALEOZOIC LIFE Plant Life Acritarcha are unicellular micro phytoplankton of organic composition and with a known life cycle is the first appearance of plant life in marine environments started at Precambrian and continued to Recent. They appeared their acme period during Ordovician-Devonian

Vascular plants appeared in Cambrian

Though vascular plants came into existence in Cambrian, but further diversified and advanced during Devonian Luxuriant plant life is noticed in Carboniferous which ultimately gave rise vast coal deposits world wide, but a few representative in the Himalayas. However, in Peninsular India, environment was suitable for coal deposits. Many families of plant in Gondwana strata are of Permian age.

Animal Life  Early life seems to have been essentially marine and particularly most of the invertebrate fauna and their lineage known today (whether living or fossil), existed in some part or other of the Paleozoic

 Unicellular organisms are quite common

 Foraminifers were present from the Cambrian but they assumed some importance during the Carboniferous  Sponges, one of the simplest multicellular organism and essentially marine, increased in number only in carboniferous  Corals came into prominence in Ordovician and Silurian and continued further, they are the main carbonate builder in the marine environment

 Echinoderms were flourished through out the Phanerozoic but, prominent in Ordovician and Silurian and were extinct by Permian  Brachiopods (bivalves) shows one of the longest range of existence and were survived up to Tertiary. Since most of them are calcareous shells, these are well preserved and are used in stratigraphic classification. (Lingulella, Obolus Wastonia and Obolela Atlantica are well preserved in Cambrian in Spiti)

Pelecypods appeared in Cambrian and also live in Holocene These can live in fresh, brackish and marine water

 Gastropods appear in Cambrian, represented by few species in Ordovician-Silurian and occur in considerable numbers in Permian. They can live in all types of environments from marine to mountain

Cephalopods, which are exclusive marine, are represented by few species in Ordovician And a few more in Permian. After that they flourished Ostracods are known from Paleozoic. These are very important in petroleum exploration

Trilobites are index fossil in Lower Paleozoic specialy during Cambrian and almost extinct by the end of Permian

Conodonts appeared in Cambrian and extended up to Triassic. Due to their lack of facies restriction and world wide distribution these are used in correlation.

Vertebrates The primitive vertebrates came into being in Devonian

Amphibians evolved from fishes of the Earlier Silurian Period

MAGMATIC ACTIVITIES There was invasion of granitic magma on large scale throughout the Himalayan province from Manshera in northern Pakistan to Manaslu in Nepal and beyond during 525 to 475 Ma. The intrusion of granitic magma caused low grade metamorphism to the invaded Proterozoic rocks

Cambrian Period/System The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's Cambrian rocks are best exposed

THE CAMBRIAN PERIOD The Cambrian strata does not show any profound unconformity from the lower lying Proterozoic succession and hence it is difficult to mark the boundary sharply. However, on the basis of the faunal appearance, it is demarcated in many places. Another problem is that, the fossils in the Cambrian are too varied that their first appearance is doubted. It is apparent that some of them have been evolved over a long period of time.

Strata belong to the Cambrian occur in the Tethys Himalayas and in Lower Himalayas in the state of Jammu and Kashmir, Himachal Pradesh and Uttarakhand. In the Lower Himalayas, the Cambrian strata are separated by profound unconformities from the overlying Permians but in the Tethys Himalayas there is almost continuous with Mesozoic and Cenozoic with occasional minor unconformities. The Upper most Cambrian strata are absent in the entire Himalayas indicating a major hiatus

Cambrian in Jammu & Kashmir Cambrian strata occur in Jammu-Kashmir and in Zanskar-Spiti sector. Of all the known strata of the age, the Kashmir succession is by far the most accessible and complete. Good sections are exposed in Lidder valley, Basmai anticline in Sind valley.

Cambrian in Himachal Pradesh Cambrian strata occur both in Tethys Himalayas and Lesser Himalayas in Himachal Pradesh. The Kunzun La is the principal Cambrian Formation in Lahaul-Spiti-Kinnaur sub-basin in the Tethys Himalayas of HP. It comprises greenish grey shale, siltstone, slate, quartzite and dolomite. In the Lesser Himalayas, the Cambrian is represented by Tal basin Cambrian in Uttarakhand Excellent exposure of Tal Formation lying over Krol formation is found in the Mussoorie syncline in Uttarakhand. The rocks consists from bottom to top are Chert Phosphorite Member, argillaceous, arenaceous, calcareous, quartzitic and limestone. Presence of phosphorite at the base of Tal Formation establishes the Global Cambrian Phosphogenic Province in the Indian subcontinent.

ORDOVICIAN AND SILURIAN There are difficulties to separate the rocks of Ordovician and Silurian because: 1.Due to considerable thickness of unfossiliferous strata 2.Paucity of fossils to distinguish 3.The cyclicity of sedimentation in rocks of both ages So there are no means by which the rocks of these two different rocks can be separated and hence are clubbed together

Jammu & Kashmir Region: In Jammu and Kashmir, Ordovician and Silurian rocks are exposed in Doda, Poonch, Anantnag and Baramulla districts. Rocks are represented by volcanics, slate, phyllite etc. In Shans Abria syncline, a large exposure of variegated slate with numerous distorted, crushed and obliterated fossils is found overlying the blue clay of Cambrian age.

In Anantnag district, the entire sections exposed representing from Late Cambrian to Silurian is grouped under Hapatnagar Group But the Late Cambrian is absent here as in the other parts of the Himalayas too Himachal Pradesh region: The Thango Formation is represented by basal conglomerate followed by quartzite, doleranite and slate and characterized by typical purple colour and shows a rugged topography. Shale partings in between preserve well preserved trace fossils Numerous small sills of gabbro-norite affinity are observed within this Formation The sedimentation of Thango Formation was started by fluvial material reworked in beach and ed through essentially tidal zone with storm episodes where wave action was prominent. Toward the terminal phase there was decrease in energy level, possibly due to relative deepening of the basin. The entire sedimentation was taken place under oxidizing condition

Takche Formation: Takche Formation is rich in carbonate and is easily distinguishable from distance by its brown colour Small transgressive sills of dolerite composition are intruded into the Takche Formation. The rocks of the Takche Formation are represented by Sandstone to shale to limestone to dolomite with a lot of facies changes in between giving rise to mudstone, packstone, floatstone etc. Besides these there have been considerable reef build-ups by corals, stromatopods and solenoporoids.

Uttarakhand Region: In Uttarakhand, the Ordovician and Silurian successions are represented by Upper Garbyang, Shiala and Young Limestone Formations. Lithologically these are representing variegated shale, crinoidal breccia and sandy limestone lies above the Garbyang Formation All the three Formations are rich in fossils. The presence of age marker Acritarch reveals the Ordovician-Silurian boundary lies in the Shiala Formation

DEVONIAN The characteristic litho unit of this age is Muth Quartzite, which is white colour, hard and compact and can be easily distinguished from areal photograph. It extends from Kashmir valley to Kumayun Jammu and Kashmir region: Muth Quartzite is the marker horizon and occurs repeatedly due to folding. Rare plant remains are reported from this litho unit. Pre-Devonian plant life is recorded in India Himachal Pradesh region: The Muth Quartzite rests on Takche Formation sharply indicating a break in sedimentation in Spiti area. In Spiti area it is more or less uniform thickness. At places, olive green shales and conglomerates are associated with it along minor amount of dolomites. The presence of trace fossils, herringbone cross bedding, subaquoussubaerial mud cracks indicates littoral zone of deposition. It is overlain by Lipak Formation

Uttarakhand: In Kumayun, Devonian is represented by Quartzite and dolomite layers. It is overlain by the Quartzite typical of Muth Formation CARBONIFEROUS In some part of the world, Carboniferous is represented by both terrestrial and marine sediments, some of them are rich in coal seams. Marine sediments are confined in the Himalayan region (J & K, Spiti-Zanskar-Kinnaur in HP, Kumaun in Uttarakhand) with a hiatus in Upper Carboniferous. But the Upper carboniferous sediments are preserved in Peninsular India and forms the base of the Gondwana Supergroup. Glaciation was initiated in the Upper Carboniferous. Towards Lower Carboniferous, there was marine transgression in Peninsular India and hence intercalation of marine sediments with Gondwana sediments. This gives a clear evidence of paleogeography of Peninsular India

Jammu and Kashmir: In Kashmir sub-basin, Carboniferous is represented by Tannaki Conglomerate, Syringothyris Limestone and Fenestella Shale

Himachal Pradesh: Carboniferous strata in HP is represented by Kanwar Group having three Formations i.e. Lipak, Po and Ganmachidam Formations Lipak Formation: It starts with dirty white grey locally cross bedded sandstone followed by grey shale inter bedded with limestone and sandstone in middle and local shale with lenticular gypsum bed in the upper part. Depositional environment change is well noticed in sedimentary sequences. Po Formation: It is composed of dark grey, pale green shale, siltstone and white grey sandstone with shale predominantly in the middle part of the sequence. Burrows, sole marks, ripple marks are present in quartz arenite. Ganmachidam Formation: It is composed of pebbly mud stone, pebbly sandstone, pebbly siltstone, conglomeratic sandstone and black shale alternations. The entire sequence is unfossiliferous

Uttarakhand: In Uttarakhand the Carboniferous is represented by Kanawar Group having two Formations Po Formation Lipak Formation These are the continuation from Spiti area PERMIAN In Peninsular India, after a great hiatus since the Precambrian, terrestrial deposition commenced with pockets of glacial tillites of Upper Carboniferous followed by deposition of terrestrial strata of the Gondwana Supergroup extending Lower Cretaceous. In the Himalayan terrain, after the deposition of the Muth Quartzite, there was a hiatus Frequent volcanism and intercalated plant fossils are reported in Pir Panjal Range

Extensive marine sedimentation is a conspicuous feature in Himalayan terrain. Marine incursion in Permian within Peninsular India is also recorded in Rajasthan, Madhya Pradesh and Bihar. Permian in Jammu and Kashmir: Panjal Volcanics: The rocks of this Group are prominently visible on the summits of Pir Panjal range hill masses. This volcanic suits forms the central axis of the range. Relation between successive flows indicate less time gap between successive flows. Without erosion surface and fused nature of s less time gap between successive flows. The flows are basaltic to andesitic in nature. Zewan Formation: Marine fossiliferous rocks of Permian age known as Zewan Formation in Kashmir stratigraphy are well exposed in Zewan valley in Vihi district. Khunamuh Formation: Dominated by Permian brachiopods and foraminifers

Himachal Pradesh: Permian in HP is represented by Kukti Formation: Carbonaceous phyllite, thin-bedded limestone calcareous phyllite, calcarenite and pebble bed Salooni Formation: Black shale, slate, calcareous slate and lenticles of limestone Gechang Formation: Brown to grey, pale grey, coarse-grained weakly bioturbated cross-bedded, calcareous sandstone with local conglomerate and/or shale lag at base. Gungri Formation: Black shale, calcareous silty shale, phosphatic cherty calcareous nodules and thin limestone with coquina lenses.

Uttarakhand Permian: Kuling Formation : Rich in plant fossils Arunachal Pradesh: Arunachal Himalayas remained a landmass of no sedimentation from Neoproterozoic to Carboniferous. Paleozoic is represented by Lower Permian rocks of Lower Gondwana Supergroup.

PENINSULAR INDIA: Marine incursion in southern belt of Himalaya in Early Permian took place possibly through rift valleys in Indian shield. These together with salt range through light on paleogeography of Central India during Permian. Umaria marine Bed: About 3m thick marine strata occurs intercalated in Lower Gondwana strata in Umaria, Madhya Pradesh. This bed overlies on the Talchir Boulder Bed and es gradually into Barakar rocks of Lower Gondwana. The marine bed is composed of sandstone and clays with numbers of marine species like Productus, Spiriferina, Reticulariia and Athyris.

It is inferred that an arm of sea was extended from the west up to Umaria and a little beyond leading to the deposition of these sediments Mahendragarh Marine Bed: A marine bed of about 5m thick associated with the basal member of Talchir Formation. This marine bed starts with shale followed by conglomerate, blackish shale, green splintery shale and an upper member of green sandstone. Fossils are mainly confined in the basal conglomerate bed. The faunal assemblage and their similarity with Bihar, Darjeeling, Rajhara, West Bengal, Sikkim, Arunachal Pradesh indicate the marine incursion from north. But in Umaria, the faunal assemblage resembles to Salt Range, Badhaura, Rajasthan indicate the marine incursion from west probably through the Narmada rift. The faunal record indicate the two marine beds were deposited in different times during Early Permian.

GONDWANA SUPERGROUP After the deposition of Vindhyan and Kurnool sediments and their subsequent deformation, there was a great hiatus in Peninsular Indian Geology

Gondwana Basins of India occur within the suture zones of Precambrian cratonic blocks of Peninsular India along some linear belts. More than 99% of the total coal resource of the country is present within these basins. The basins are demarcated by boundary faults having graben or half-graben geometry.

It was almost closing phase of the uppermost Carboniferous, deposition of glacial sediments were initiated in a number of basins in some parts of peninsular India. Most of them were confined in major River valleys, namely Damodar, Son, Narmada, Mahanadi, and Godavari

Apart from these basins, few sections in the Himalayas and along the coast, deposition was continued up to Early/Middle Mesozoic Sedimentation was continued from Upper Carboniferous to Late Jurassic/Early Cretaceous As a result a thick pile of sediments were deposited ranging thickness of ~200m to >4000m.

Though these sediments were essentially terrestrial, marine incursion has been evidenced at places H.B. Medlicott coined the name “Gondwana” to these sediments after a tribe “Gond” live in Central India The term was mainly denoted to the glacial boulder bed and subsequent conglomerate, sandstone, shale, coal beds of fluvial and lacustrine origin from Peninsular India

Subsequently, sediments, flora, and fauna, of Gondwana affinity are recorded from almost all the southern continents of the world. Edward Suess in 1855 coined the term “Gondwanaland” to all the southern continents i.e. Indian Peninsula, Madagascar (Malagasy) Central and Southern Africa tracing their Common features in geological history

The sequence represent a long period of continental sedimentation that was started in Permian Period and was closed in Cretaceous covering 180 MY of geological Time scale. The most significant feature of this sequence is that sedimentation and faulting was going on simultaneously.

Another view is that, the Gondwana rocks were covered much wider area than now but have been eroded from the positive geographical positions and preserved in the grabens Characteristics feature of Gondwana sediments are, these are rich in floral remains and poor in vertebral remains and especially these are restricted to the middle part of the succession CLASSIFICATION OF GONDWANA Classification of Gondwana succession in Indian geology is a disputed one. Some workers like C.S. Fox (1931), Cottor (1917) and Oldham (1893) proposed two fold classification. However, other previous workers adopted three fold classification. Two fold Classification Classification of Gondwana is based on plant fossils. The Lower Gondwana is dominated by Glossopteris flora. However, the Upper Gondwana is dominated by Ptilophyllum flora

Upper Gondwana

Ptylophyllum Flora Glossopteris Flora

Lower Gondwana

The change in floral characteristics has been attributed to the climate change through the successive periods of earth’s history Three fold Classification: Three fold classification of Gondwana was proposed by O. Feistmental (1880), Vredenberg (1910) and Wadia (1926). Their classification was mainly based on lithology. The Upper part of the Lower Gondwana and the Lower part of the Upper Gondwana show similar lithology. Hence they clubbed those sections together and named it as Middle Gondwana. This Triprtite classification fits into the International standard scale and corresponds to Upper Gondwana--------Jurassic Middle Gondwana-------Triassic Lower Gondwana--------Permian But in India, two fold classification is widely adopted. The Lower Gondwana corresponds to the Paleozoic rocks and the Upper Gondwana corresponds to Mesozoic rocks

SEDIMENTATION AND PALEOCLIMATE Gondwana begins with glacial sediments.

Study of till fabric, boulder trains, and pavement striae indicate that glaciers were moved by complex lobes of ice sheets from NW of present Godavari valley towards N and NW directions In Damodar valley region, the high lands were located in N and NW and glacial advancement was towards South In East coast of India, ice movement was from a high land that was existed east of the present day east coast