CHAPTER - 1 INTRODUCTIONshodhganga.inflibnet.ac.in/bitstream/10603/107374/8/08... · 2018-07-07 · 1 CHAPTER - 1 INTRODUCTION 1.1 GENERAL The long period of quiescence that ruled

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CHAPTER - 1

INTRODUCTION

1.1 GENERAL

The long period of quiescence that ruled the landmass since the dawn of

Proterozoic ended with the initiation of sedimentation in three newly formed

depressions (basins), on or close to the margins of the craton. They are Cuddapah

Supergroup, Pakhal Supergroup and Neo Proterozoic Groups such as Kurnool,

Penganga and Bhima groups.

Sedimentary basins have not received as much attention as they deserve. The

variety of sediments deposited in these basins, have sampled the continental crust of

that period and have, therefore, a great deal to tell us of the condition of the

atmosphere and hydrosphere and the nature of the weathering prevailing then.

The term Proterozoic is synonymous with Algonkian (USA), which is widely

used to represent late Precambrian. A variety of rocks are found in Precambrian

terrains, and each continent differs little from another in this regard. They are

represented by all kinds of sedimentary rocks, extensive lava flows and some still

relatively undeformed and unmetamorphosed. The name ‘Purana’ was given by

Holland (1907) to the group of unfossiliferous rocks lying unconformably over the

highly metamorphosed schists and gneisses of assumed Archaean age. Since there is

no precise age limit assigned for rocks falling with in this group, Dhaundiyal has

advocated dropping the term altogether in preference to the well defined chrono-

stratigraphic name “Proterozoic” with its proposed 3 divisions into early, middle and

late Proterozoic. The name Purana, however, is a most convenient term applicable to

sediments deposited in the middle to late Proterozoic, somewhat equivalent to the

Riphean of Russia. Proterozoic rocks in the form of least disturbed platform

sediments in India are younger than 1600 ma.

The Precambrian sedimentary formations are very well developed throughout

India. The Peninsular India offers a better scope for the study of these sedimentary

formations. The Kurnool sediments, which rest unconformably on the denuded edges

of the Cuddapah Formation, forms one of the sedimentary basins of the Precambrians

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(Purana) in the southern part of the Peninsular India, and are exposed in two basins

one in Kundair valley and the other in the Palnad tract. The Kurnools have been

broadly classified by King (1872) into four major divisions: Banaganapalle,

Jammalamadugu, Paniam and Kundair Formations, of which the first two are grouped

under lower Kurnools and the other two under upper Kunools.

This thesis deals with the stratigraphy, lithology, structure, sedimentology,

geochemistry, provenance and depositional environment of the Palnad sediments

(Kurnool Group). The sequence of rocks studied is exposed in Guntur, Krishna and

Nalgonda district of Andhra Pradesh. The area is found to be of particular interest,

since the Kurnools are very well exposed and their actual contact with the underlying

Archaeans and Cuddapahs is quite distinct, providing a continuous geological

succession, enabling to establish the detailed lithostratigraphy of the area.

1.2 LOCATION AND COMMUNICATION

The Kurnool Group of rocks are well exposed in Kurnool, Cuddapah, Guntur,

Krishna, Nalgonda and Mahabubnagar districts of Andhra Pradesh. The exposures can

be noticed in two basins, one in the Kurnool basin and the other in the Palnad Sub

basin. The Kurnool basin, extends between the latitude 14°30" - 16°00" and longitude

77°58" -78°45", covering an area of about 14,500 sq Kms The Palnad Sub basin

which is found in the North-Eastern part of Cuddapah basin extends between the

latitude 16°18" - 16°55" and longitude 79°18" -80°26" covering an area of about 3600

sq. Kms (Survey of India toposheets : 56 P/6, 7, 8, 10, 11 and 65D/1 and 2). The

location map of the area is shown inFig1.1.

The area is accessible from Hyderabad, Kurnool and Vijayawada. Two major

towns in the area, Macherla in Guntur district and Jaggayyapeta in Krishna district are

very well connected by rail and road network. There are good metalled roads

connecting railway stations, district and taluk headquarters. Also, the villages are very

well connected by metalled roads. The communication network, both by rail and

road, has enabled Guntur and Krishna districts in the development of few cement

factories such as Andhra cements Ltd., (Dachepalli, Piduguralla) KCP Ltd,

(Macherla), Bhavya cements, (Tangeda), Sri Durga cement works (Old Guntur), JK

white cement works, (Old Guntur), Madras cements Ltd., (Jayanthipuram),Ramco

cements Ltd., (Jayanthipuram) situated at Macherla and Jaggayyapeta.

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Fig 1.1 LOCATION MAP OF THE STUDY AREA

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1.3 GEOMORPHOLOGY

The geomorphology of the area is essentially a reflection of the lithology and

structure of underlying rocks. Therefore a brief account of the same is presented as it

could help in deciphering the continuity of lithounits and their structural disposition.

The terrain in the South-western part of the basin ie, around Macherla,

Veldurti and Dwarakapuri is made up of either steep slopes or scarps and flat topped

hillocks of quartzites. Hillocks run roughly in east-west direction covered by

Kandlagunta, Mandadi and Veldurti Reserved forest. In the North – Eastern part of

the basin ie, around Jaggayyapeta town the terrain is a broad flat plain consisting of

carbonate rocks.

1.4 DRAINAGE

The drainage is mostly sub-dendritic to sub parallel (Vaidyanadhan, 1964).

Krishna riveris the northern boundary of the study area. Chandravanka which is

perennially flowing from south to north, is a tributary of Krishna river. A few small

streams flow in the area, important among them being Edibogulavagu and

Bottalavagu. All these streams are affluent and join Chandravankariver. Numerous

seepages are observed at the contact between quartzites and limestones. There are

waterfalls on the Chandravankariver with a fall of 20 mts at Ettipotala. These falls are

exactly at the contact of quartzites with limestones.

The drainage patterns of the study area varies considerably. A combination of

angulate, dendritic, rectangular and trellis drainage patterns have been noticed in

many parts of the study area. The important river draining the area is Krishna and a

multipurpose dam is constructed across this river 20 kms NW of Macherla town (Fig

1.2).

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Fig 1.2 PANORAMIC VIEW OF NAGARJUNASAGAR DAM ACROSS RIVERKRISHNA

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1.5 CLIMATE AND RAINFALL

The climate is the day-to-day variations in weather of a locality and it includes

the following elements as temperature, precipitation, humidity, sunshine and wind

velocity. Palnad area enjoys a warm summer and dry winter. The hot season

commences early in March and ends up sometime in June, when the monsoon starts.

The minimum annual temperature varies from 16°C to18°C. The maximum

temperature is around 40°C. The average annual rainfall varies from 100 to 125 cms.

Area receives rainfall both during SW monsoon and NE monsoon. Often the NE

monsoon brings out floods causing severe damage to human life. Periodically, the

rainfall is precariously low or unseasonal, causing drought and famine.

1.6 MINERAL RESOURCES

The area is endowed with a fairly large number of mineral deposits, important

of which are asbestos, barites, copper, steatite, lead and diamond(Fig1.3). Although

the Kurnool Formations do not contain metalliferous deposits, they contain clays,

ochres, limestones and dolomites, besides excellent building stones and raw materials

for cement. There are also a few deposits of high grade calcareous tufa and

efflorescence of earth salts and soda.

Old workings for diamond are noticed in basal Banaganapalle conglomerates

in numerous localities. Yellow ocherous shales occur in pockets in the Owk shale

member. This material can be used in colour wash distempers and also possibly in the

cement industry for making coloured cements. Small deposits of white clays are

exposed in the Owk Shales and are used as a filler.

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Fig 1.3 MINERAL MAP OF ANDHRA STATE

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1.7 GEOLOGY

The foundations of the geology of the area were laid by several workers

during the last part of 19th

century and the early part of 20th

Century. The rock types

constituting the Kurnool Group of rocks in Palnad Sub basin are mainly of quartzites,

shales and limestones. The generalized geological succession or stratigraphy of the

area was first given by King (1872).

The Kurnool strata cropout in two isolated areas, namely in Kurnool basin and

the other in the Palnad Sub basin. The lowermost formation of the Kurnool is the

Banaganapalle conglomerate, sandstone and quartzite. The conglomerate being

occasionally diamondiferous. It is succeeded by the Narji massive or flaggy limestone

with shale and quartzite intercalations. This is well developed in both the basins,

where huge reserves of limestone suitable for the manufacture of cement exist. The

Narji is succeeded by the Owk Shale. The Owk shale is overlain by the Paniam

quartzite, which in turn is overlain by earthy siliceous Koilkuntla Limestone, followed

by purple calcareous Nandyal Shale with thin intercalations of limestone.

1.8 SOIL AND AGRICULTURE

Soil quality is an important factor in the crop yield. The area is characterized

mainly by three types of soils, namely black cotton soil, red loamy soil and dark

brown soil. Most part of the research area is covered by black cotton soil, and are

found in areas where limestones are occurring. The red loamy soil is formed due to

the weathering and erosion of quartzites. Another type of soil is dark brown in colour

and is covering the area between Mandadi and Mutukuru. This colour is due to the

weathering of purple coloured shales of Kundairs.

The dry climate in Guntur and Krishna district is not conducive for a good

vegetational cover. The most fertile and rich tract of land bordering the banks of the

river Krishna is however intensely cultivated. The main crops cultivated in the area

are Chillies, Jowar, Ragi, Paddy, Blackgram and cotton. Except for the green strips of

vegetation along the valleys, the flat topped hills are not covered by vegetation. The

vegetation is dry savannah and poor steppe. The drought resisting xerophytes, thorny

bushes and scrubs along with grass grow over the hill tops and along the slopes. The

region is characterized by open spaced short trees of acacias and euphorbias, with an

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under growth of thorny shrubs and grasses. Grasses grow rapidly during the rainy

season. The reserve forest in the area is reported to contain bear, leopards, wild hogs,

hares, porcupine, hyena, deer, rabbits, snakes and few sambars.

1.9 PREVIOUS WORK

The Cuddapah Group of rocks are overlained by a set of predominantly

sedimentary rocks called Kurnools and the two groups are separated by an angular

unconformity. These sedimentary rocks belong to the upper Proterozoic. It is

significant to note, while reviewing the literature on Kurnools that much of the

contributions in the early periods come from the officers of the Geological Survey of

India. The earliest work on Kurnools dates back to 1794 by Mackenzie, who focused

his attention on the lithology of this tract. During further attempts emphasis was

mostly on economic evaluation of the area, particularly for diamond and iron by

Heyne (1814) and by Voysey (1825). Four other contemporary workers, namely

Cullen (1827), Christie (1828), Malcolmson (1836) and Newbold (1836) for the first

time started describing various rock types of Cuddapahs and Kurnools. Carter (1854),

attempted to secure a position for Cuddapahs and Kurnools in the geological scale of

formations. None of these writers has dealt with the stratigraphy and structure of these

rocks and their account on lithology is also very brief. A pioneering geological work

was carriedout by trio geologist Sir Thomas Oldham (1786), William King(1872) and

Robert Bruce Foote(1892). A very comprehensive treatise on the Kurnool group came

off from King (1872). This memoir still remains a valuable geological document on

the Kurnools. His greatest contribution to the geology of the Kurnools is the first ever

formulation of comprehensive stratigraphy of the entire basin. By the test of

superposition he classified Kurnools into four major lithological units, each of which

comprising several subunits named after the predominant rock type. The four major

lithological formations are Banaganapalle, Jammalamadugu, Paniam and Kundair.

Though, the earliest geological work in the area is by King (1872) but, the first to

record about the geology of the area is Bruce Foote whose notes were freely quoted

by King (1872) in his memoir.

After the monumental work of King (1872), there was a period of lull and only

during the last fifty year or so substantial amount of work has been turned out on

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various aspects of Kurnools. It is significant to note that the original stratigraphy

proposed for Kurnools by King, however, stands undisputed throughout.

The Kurnool formations of the northern part of the Kurnool district were

mapped by Roy (1945-46 & 1946-47). Venkatesh (1947-48 & 1948-49) and

Madhusudhana Rao (1950-51). Balasundaram (1944-45) and Venkatram (1945-46)

examined the limestone in this area belonging to Kurnool Group.

As regard to the geomorphology of the basin, no detailed work has been

carriedout till 1955. Dutt (1955) described various geomorphological features and

carriedout extensive work on Geology of the Kurnool sediments. Again in 1962, 1975

and 1986 mapped the Kurnool formations and reported flux grade and cement grade

limestones from the basin. He recognized a disconformity at the base of the Paniam

Quartzite and identified Kurnool as a group.

The evidence for finding out life during upper Proterozoic times was

carriedout in detail by Saluja et al., (1972). They had done detailed palynological

investigations and reported some of the micro-planktons for the first time from the

Kurnool shales. On the basis of this investigation they assigned late Precambrian to

Cambrian age for these sediments and inferred that the Kurnool sediments are

deposited under shallow marine conditions. Later Sharma and Shukla (1973) reported

carbonaceous mega remains from the Owk Shales and inferred the Neoproterozoic

age for it. Also, Crawford and Compston (1973) worked on the age factor of

Cuddapah and Kurnool Group of rocks.

Subsequently, Reddy and Vijayam (1974, 76) have studied the lithology and

tectonic framework of sedimentation of the Kurnool sediments in the Western part of

Palnad basin, besides studied in detail clay minerals in Owk and Nandyal Shales and

inferred the marine depositional environment for these shales. Also, they have made a

detailed study on microstylolites in Narji Limestones and discussed in detail the

diagenetic aspects of limestones and inferred the tectonic activity in the area.

Natarajan and Rajagopalan Nair (1977) have reported post Kurnool thrust and

other structural features (primary and secondary) in the north-eastern part of the

Palnad basin, Krishna district, which constitutes a very important factor in

interpreting the tectonic history of the area. They have done detailed work on pressure

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solution structures (stylolites) in Narji Limestones from Jaggayyapeta area and

described their nature and types, megascopic and microscopic features and tectonic

effects on them. They have discussed in detail the usefulness of stylolites in

recognizing the bedding planes and their importance in estimating the thickness of the

limestone units.

Later Arya and Rao (1979) worked on the Narji Limestones and reported

bioturbation structures from the Narji Formations. A detailed work on structural

aspects of Cuddapahs and Kurnools has been carriedout by Rajurkar (1977). From the

analysis of structural patterns and other details, it is concluded that the Cuddapah

orogeny resulting in severe deformation of the Cuddapah is of Pre Kurnool age. There

has been another period of deformation in the post Kurnool period, where in the

Cuddapahs and Kurnools suffered very little folding, but extensive faulting. Besides,

reported discoidal impressions akin to Fermoria, from the Owk Shales of Kurnool

Group by this author.

Later, Kamal (1982) carriedout detailed petrographic studies and on the basis

of the types of cementing material, authigenic products and replacement textures, it is

inferred that the Paniam sands deposited in beach to dune environments, subjected to

shallow to medium burial and involved in redexomorphic to locomorphic stages of

diagenesis. Besides, Kamal and Vijayam (1982) have reported intraformational

conglomerate from this group and attempted to discuss mode of origin.

Rao and Dasari (1989) has worked in detail on the isotopic variations in

limestones (Narji and Koilkuntla). Observed a progressive increase of δ O18

values for

Narji Limestones from basal to top horizons and inferred that the gradation of δ O18

value is due to interaction of various horizons with fresh water in the later geological

periods and possible consequent exchange.

Venkatachalapathy et al., (1992) have carried out detailed work on

palynological aspects of Kurnool Group and reported some of the microplanktons

from this group. From this study they inferred Precambrian-Cambrian age for the

Kurnool Group of sediments and also attributed shallow marine intertidal depositional

environment for these sediments.

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Lakshminarayana et al., (1999) studied in detail the Paleocurrent pattern of the

Banaganapalle Formation in the Kurnool sub basin and inferred the provenance as

mainly the intrabasinal tract occupied by lower Cuddapah sediments, igneous

intrusive and the basement located to the west.

Grururaja et al., (2000) recognized a boundary strata separating Precambrian

from the Cambrian in the Cuddapah basin.

Patil. D.J et al., (2002) carriedout Carbon, Oxygen and strontium isotope

geochemistry of carbonate rocks from Kurnool Group and inferred the open system

diagenetic trends for the carbonate rocks of Narji Formation and for Koilkuntla

Formation does not show any definite alteration trends.

Harish et al., (2003) worked on the petrography and fluid inclusion studies on

Palnadsiliciclastics and suggested that the Archaean granites, granitic gneisses and

sedimentary formations belonging to Cuddapah Group are the source rocks for the

Palnadsiliciclastics.

Saha and Chakraborty (2003) studied in detail the deformation pattern in the

Kurnool and Nallamalai groups in the NE part (Palnad basin) of the Cuddapah basin.

Subsequently Saha et al., (2006) carriedout a detailed work on sedimentary sequences

in Palnad and Kurnool subbasins and interpreted their paleogeographic and tectonic

implications.

Jeyagopal, A.V et al., (2006) worked on the geology of the Julakallu area,

Guntur district, Palnad sub-basin. The geological studies have brought out the

presence of unknown Cumbum shale/phyllite in the Julakallu-pinneliare within the

Palnad sub-basin. Cumbum shale/Phyllite and quartzite was found to rest above the

Narji Limestone.

Later Butchi Babu et al., (2008) estimated the thickness of limestone

formation in Kurnool sub basin by Aeromagnetic anomalies.

Subsequently Babu (2011) carriedout provenance studies by U-Pb-H-L-O

isotopic composition of Zircons from the conglomerates and Sharma (2011) reported

Neoproterozoic and Ediacaran paleobiological remains in the purana basins of

Peninsular India and inferred the age of Kurnool, Bhima and Vindhyans.

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Joy et al., (2012) worked on geology of the Banaganapalle conglomerate of

Kurnool Group and inferred the diamond provenance for the sequence. Saha and

Tripathy (2012) worked on Tuff beds in Kurnool sub basin and inferred the felsic

volcanism in Proterozoic intracratonic basins. Sharma and Shukla (2012) reported

helically coiled microfossil in the Owk shale of Kurnool Group and discussed their

significance.

Bickford et al., (2013) carriedout a detailed work on U-Pb ages of Zircons in

the Owk Shales and inferred the age and the provenance for the Owk Shales.

Paul. A.K et al., (2013) carriedout a detailed study on mineral chemistry of

radioactive uranium deposit of Koppunuru area in Palnad basin. The study has

revealed the potential for multi-episodic epigenetic U-mineralisation in basement

granitoids and the overlying Banaganapalle Formation.

Singh, R.V et al., (2013) also has reported uranium mineralization in

Koppunuru area of Guntur district in Palnad basin. They have reported uranium

mineralization in the granitic rocks which forms the basement for Palnad sediments.

1.10SCOPE OF THE WORK

A survey of previous literature indicates that many of the aspects were either

largely regional or limited to report some salient and specific occurrences. As such no

attempt had been made to know the characteristics of the Kurnools. This status has

remained so because of the very large size of the basin and the voluminous amount of

work needed to achieve the desired goal.

In line with the aforesaid objective, this work has been primarily oriented on

lithostratigraphy, sedimentary structures associated with the lithotypes and their

significance in the interpretation of the paleo environmental conditions of deposition.

The detailed study of the sedimentology helps in understanding the media of

transportation, depositional environment and provenance. The geochemical studies of

shales and limestones helps to evaluate the sedimentary environment under which

they were deposited and the reconstruction of ancient environmental conditions. Also

a detailed study of the diagenetic effects in the area helps to reveal the environment of

deposition as well as post-depositional textural and mineralogical modifications.

Besides, the clay mineralogy, XRD and staining technique have also been applied in

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this study, which may throw a better light as to the geological setting and the nature of

deposition of the sediments. The aspects like stratigraphy, structure, sedimentology,

geochemistry diagenesis are particularly chosen for the following reasons.

1. No detailed work regarding the above said aspects is on record.

2. The basin presents contrasting lithotypes having mainly sedimentary rocks

1.11 OBJECTIVES OF THE WORK

1. Construction of lithostratigraphical column.

2. Sedimentological studies including Textures, Modal Analysis, Petrography and

Structures.

3. Detailed Study of Carbonates and argillites by XRD and Staining technique.

4. Study of Provenance and depostional environment of the rocks based on

Geochemistry, Pre and post diagenetic effects in the area.

1.12 METHODOLOGY

Survey of India Toposheet (Scale 1:50,000) are used for field work to collect

the basic data required to know the geological history of the area. The main purpose

of field work is to construct the lithostratigraphic sequence of the study area (Palnad

Sub basin), along with a detailed study of lithounits. The basic data collected in the

field includes the study of primary and secondary structures, variation in colour and

thickness of the arenites carbonates and argillites, contact between the different litho

units within the stratigraphic divisions, the significance of paleo environmental and

depositional evidences. The different methods and techniques applied in investigating

research problem is as follows:

1. Lithostratigraphical columns of the rocks of Palnad Sub basin were constructed

using measured outcrops.

2. About 200 samples were collected from different lithological units for studying

the petrographical and textural characters and compositional variations.

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3. The Sedimentological work of quartzarenites includes grain size analysis,

petrographic study, modal and heavy mineral analysis with a view to understand

their genesis and environmental significance.

4. Quartzarenites are studied in detail as to their associated structures (cross

stratification, ripple marks, desiccation cracks) and in conglomerate orientation

of pebbles, pebble counting, matrix study were also carried out.

5. The macro and micro stylolites associated with the carbonates have been studied

in detail which helped in understanding the probable tectonic influence in the

area.

6. The colour and nature of the shales are used for classifying the Owk Shale into

lower and upper divisions and in the like manner the colour and nature of the

limestone are used for classifying the carbonates of Kurnool Group.

7. As the limestones of the group are cryptocrystalline in nature it is difficult to

carryout petrographic studies, hence staining technique is applied to differentiate

calcite and dolomite among the carbonates.

8. Separated clay minerals from shales using 1/10 N HCL by suspension method

and identified the clay mineral by obtaining the XRD curves. Illite is the

dominant clay mineral, the presence of which indicates the marine alkaline

environment for the shales. Besides, determination of pH substantiates that the

shales are deposited in marine alkaline environment.

9. Carbonates of the Kurnool Group are cryptocrystalline in nature and is difficult

to study their petrography. Hence, X-ray diffractogram analysis is used in the

identification of minerals, which revealed that calcite and quartz are the dominant

constituents.

10. The major and trace element analysis of arenites, argillites and carbonates were

carried out by Calorimetric, Titrimetric and by wet chemical analysis through

ICP.

11. Pre and post diagenetic effects in the area were studied in order to reveal the

environment of deposition.