Lithological studies of sedimentary rocks exposed at Wadi village (Jhura dome), Palanpur area, Kutch mainland, Gujarat

Ms. Apurva D. Fuladi* Ms.Pushpa Zamarkar** Assistant Professor, Department of Geology, S. S.E.S. A’s Science College, Nagpur, M.S., India. Email: [email protected] 1 Corresponding Author : Ms.Pushpa Zamarkar, Assistant Professor, Department of Geology, S. S.E.S. A’s Science College, Nagpur, M.S., India.

ABSTRACT The Jhura Dome (Jhurio and Jumara formations) of Mainland Kachchh, western India, comprises a 500-meter thick succession of clastic carbonates and mixed siliciclastic-carbonates intercalated with shales from the Middle to Late (Patel, J. S. et. al. 2015). Present study, therefore, focusses on the lithological study of Golden Oolitic of Middle Jurassic of Kachchh in its type section. The study deals with the depositional environment of Jhura Dome sediments.. On the basis of field studies and megascopic characteristics, the major rock types are identified as Golden Oolitic , Dark brown and yellow Fossiliferous Limestone, Ferruginous iron coated Fossiliferous intraclastic Grainstone, Brownish yellow Bioturbated Limestone, Sandy Fossiliferous grainstone, Grayish white medium grain sandy grainstone, Yellow color argillaceous silt to fine grained sandy Packstone and Ferruginous shale. The Chari fossil of these beds is ammonite called Macrocephalites Macrocephalus. The Megafaunal remains are mostly represented by abundance such as Foraminifera, Bryozoans, Belemnoids, Echinoides, Corals, Bivalves and presence of small amounts of Algae. Keywords: Lithology, Jhura dome, Kutch mainland, Sedimentary rocks.

I INTRODUCTION The Kutch basin is situated in the western sector of Indian plate in the State of Gujarat is one of the most important Mesozoic Sedimentary basins of India (Krishna, J., et al., 1991). The Jhurio Formation is a Middle Jurassic marine carbonate-siliciclastic succession deposited in Kachchh, India's west coast, in a pericratonic embayed basin. The simplified stratigraphic horizons and abundant fossil content of this succession distinguish it. The origin of Golden Oolitic Limestone and

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Oolitic ironstones has been studied by many workers (Young, 1989); Macquaker et al., (1996); Donaldson et al., (1999), Taylor et al., (2002). Ooidal ironstones have a distinctive mineralogical composition of iron silicates (berthierine and chamosite), iron carbonate (siderite), iron oxide (haematite) and iron hydroxide (goethite) (Young, 1989) and Macquaker et al., 1996). Many researchers proposed that ooidal ironstone mark the key stratal surfaces in sedimentary successions, formation at sequence boundaries (Macquaker and Taylor, 1996). Mitra & Ghosh (1964) carried out biostratigraphic work in the Jhura dome area and gave more importance to brachiopods. He suggested that the brachiopod assemblage zone should be used for correlation and classification instead of ammonite zones. The Jhurio Formation exposes thick sequences of limestones and shales with bands of golden oolites in the type section in Jhura Dome, forming the lower part of the Mainland stratigraphy. The Jhurio Formation was formed during the period (Callomon, 1993; Khadkikar, 1996). The Jhurio Formation is overlain by part of the Jumara Formation in the Jhura dome, which is the present study area. Jhura dome, located northwest of Bhuj, is roughly elliptical in shape, with a longer axis that runs E-W. Lithostratigraphically, the Jurassic successions (Mesozoic rocks) of Kutch has been attempted in deal by Krishnan (1968) and Biswas (1971) i.e Krishnan (1968) subdivided the succession into four divisions namely, Patcham, Chari, Katrol, and Umia. Later, Biswas (1971) proposed four formations i.e., Jhurio (Jhura), Jumara, Jhuran and Bhuj formations in ascending order. The Bhuj Formation is disconformably overlain by the basic flows of the Deccan trap formation on the formation on the south while the base of the Jhurio Formation is unexposed. sedimentary rock types exposed Wadi Village, Palanpur (Jhura Dome), Kutch Mainland, Gujarat.

1 II STUDY AREA In the study area, small successions of Sedimentary rocks belonging to the Jurassic (Mesozoic) rocks of Chari Formation are exposed at Wadi village, Palanpur (Jhura Dome), Kutch Mainland, Gujarat. In Stratigraphy, the sequence of Mainland is one of the formations named as Jhurio hill that is called Jhura Dome. The study area covered the state of Gujarat of latitude 23°30’N and 23°40’E, longitude 69°32’N and 69°43’E, Toposheet number 41E/11. III METHODOLOGY The Methodologies adopted are as field trips to collect the field data and material, Collection of rock samples of the area for Sedimentological studies. To study lithounits and depositional dynamics of “Golden Oolites” (Bathonian - ) Jhura Dome, Kutch Mainland, Gujarat. Detailed study of lithological Studies of various sedimentary rock types exposed wadi village, Palanpur (Jhura Dome), Kutch Mainland.

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FIELD OBSERVATION AND ITS LITHOUNITS: In field observations, Focus in the compilation and interpretation of Field data. In the study area, the samples are collected and interpret the field data. An attempt has been made to elaborate the detailed Lithological characteristics of various rock types exposed in the area, establishment of Stratigraphic order i.e. different Lithounits. Detailed account of the geology or the Palanpur wadi area Golden Oolites member Chari formation in Jhura dome.In this area the different types of rock types are observed. The Chari Formation of Golden Oolite members the base or Macrocephalus bed i.e. crimson limestone.

EXPOSURE AT “MACROCEPHALUS BED IN GOLDEN OOLITES MEMBER IN CHARI FORMATION OF JHURA DOME, KUTCH MAINLAND : The Chari Formation rests unconformably over the Patcham formation and is made of sandy limestones marked shale and Oolitic limestone. The total thickness of the succession is about 400 meter. The Chari Formation is very rich in ammonites in the middle Jurassic age. It has divided the base or Macrocephalus beds. There a bed occurs at the base which is composed of shales and Oolites. The characteristic fossil or these have been is an ammonite caused. “Macrocephalites Macrocephalus''. They are developed mainly in the four islands of Kutch lying on the southern limit or the great Rann the Macrocephalus bed is characterized by the presence of several Macrocephalitides with ammonites of lower age only. The Macrocephalitides in Kutch often occur associated with “Golden Oolite'' in many outcrops in the mainland. But in the island where Ammonoides are scarce but “Golden Oolite '' is very well developed. The systematic and exhaustive study of the Ammonoides other fossil groups and sediments of the concerned formation throughout Kutch.On the basis of the occurrence of the limestone, Golden Oolite and shales the different types of litho units of the Formation. The thick alternate sequence of lime stones and mudstone are well exposed in the study area. The different four types such as- a) Oolitic fossiliferous grain stone, b) Fossiliferous Intraclastic grain stone, c) Sandy Fossiliferous grain stone, d) Pebbly Fossiliferous grain stone. The different rock type’s assemblage with calcareous mudstone is characterized by interbedding of moderately to thickly bedded hard and compact, golden colored Oolitic Fossiliferous grain stone. It contains well preserved Bioclasts. Assemblage is characterized by abundant bioclast, reworked intraclasts, bioturbated golden colored Oolitic Fossiliferous grain stone and calcareous mudstone having micritic groundmass with intraclarts and microfossils. The formation of Golden Oolites is two main depositional processes Mishra D. et. al. (2006) such as- a) High energy physical sedimentation from comer flows during transgression characterized by irregular to sharp nature of

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basal contact of each cycle, abundance of well preserved lasts and also shows sedimentary structure, b) Settings of Fines from suspension during fair weather period as distinguished by homogeneous fine grain interbeds of mudstone in the sequence.Waagen et al. (1875) subdivided the Mesozoic rocks of Kachchh into Patcham, Charee, Katrol and Umia Groups and correlated them with the European equivalents. However, a much more comprehensive account of the Mesozoic stratigraphy of Kachchh was proposed by Rajnath (1932) and Krishnan (1982).

MAJOR LITHOUNITS

The rock units proposed mainly on the physical characters of the sediments such as mineralogy, color, grain size, fossil content etc. The exposures of Jhura hill (Wadi village Palanpur) of Chari formation identified the different rock units and described them. The detailed Megascopic observation of the above mentioned types which is described as follows: Dark brown and yellow fossiliferous limestone: This horizon is comparatively hard and dark brown in color represented by fine grained limestone with abundant broken shell fragments with thin and elongated shape (Fig.2.1). The secondary infilling of brown color iron oxide present in this sample.

Ferruginous iron coated fossiliferous intraclastic grainstone: This rock type is comparatively hard and compact brownish yellow in color and it shows Golden Oolitic with presence of class. The brown color iron oxide is present in this sample and shows broken shale fragments. (Fig. 2.3)

Brownish yellow bioturbated limestone: It is represented by brownish yellow in color Fine grained hard and compact limestone. This rock type is highly bioturbated mostly showing vertical burrows. It is locally silicified and. The unit is marked by preservation by the behavioral activities of organisms . Sandy Fossiliferous grain stone: It is represented by medium to Fine grain sand with the presence of shell Fragments. It is hard and compact brownish yellow in color with sandy packstone.

Grayish white medium grain sandy grain stone: It is represented by medium grain sandy particles. It is hard and compact grayish white in color. It is rarely represented by small shell fragments.

Yellow color argillaceous silt to Fine grain Sandy packstone: These rock types are represented by interbedding of yellow color argillaceous silt to Fine grain sandy packstone. It is hard and compact with yellow color. The alteration of shale and limestone with well preserved deep marine

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fauna. The Ferruginous sandy packstone are certain hard silty and sandy Ferruginous bands.

Ferruginous shale: These Lithounits are brown in color with bands of limestone and shale. It is hard and compact with a yellowish brown color. It is the presence of Biofragments and broken shell Fragments. They are interbedded with sandy grain stone and shale which contain ferruginous Silty bands.

Fig. 2.1.: Yellow fossiliferous limestone. 2.2. Alteration of fossiliferous limestone and shale shows golden yellow to brown color. 2.3 Yellowish brown fossiliferous limestone. 2.4. Golden Oolites member, Chari formation of Jhura Dome.

V CONCLUSION In a local set-up particularly with reference to the district Kutch of which, the study area of sedimentary rock in which small part is largely represented by Jhura dome, the Jurassic of (Mesozoic) rocks Chari Formation for small successions of Sedimentary rocks exposed Wadi village, Palanpur (Jhura Dome), Kutch Mainland. The Diagenetic features are limited and represented only by the recrystallisation of groundmass. As such, no major geological features like fold, fault joints are visible.The upper part of the Pachham formation is made up of thinly bedded white to cream colored lime stones (pelmicrite and biomicrite) with thin bands of “Golden-Oolite'' (sandy intrasparite with golden Oolites). The middle part is composed of thick beds of grey, yellow weathering shales alternated with thick beads of golden Oolitic limestones and the lower part comprises thin beds of yellow and grey lime stones occasionally containing golden Oolits, in grey shales. The formation has been divided into seven informal members marked from below on the basis of the occurrences of the limestone, golden Oolite, and shale. In the island where Ammonoides are scarce but “Golden Oolite '' is very well developed. The systematic and exhaustive study of the Ammonoides other fossil groups and sediments of the concerned formation throughout Kutch. The different rock type’s assemblage with calcareous mudstone is characterized by interbedding of moderately to thickly bed hard and compact, golden colored Oolitic Fossiliferous grain stone. It contains well preserved Bioclasts. Assemblage is characterized by abundant bioclast, reworked intraclasts, bioturbated

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golden colored Oolitic fossiliferous grain stone and calcareous mudstone having micritic groundmass with intraclarts and microfossils. On the basis of field studies and megascopic characteristics, the major rock types are identified as Golden Oolitic limestone, Dark brown and yellow fossiliferous limestone, Ferruginous iron coated fossiliferous intraclastic

Grainstone, Brownish yellow Bioturbated limestone, Sandy Fossiliferous grain stone, Grayish white medium grain sandy grain stone, Yellow color argillaceous silt to fine grained sandy packstone and Ferruginous shale. The detailed megascopic observation of the above rock types. The petrography and diagenesis of carbonate rocks exposed in the area. The Macrocephhalus beds occur at the base of Chari formation. They are composed of Shales and Oolites. The Chari fossil of these beds is an ammonite called Macrocephalites Macrocephalus. The Megafaunal remains are mostly represented by abundant such as Foraminifera, Bryozoans, Belemnoids, Echinoides, Corals, Bivalves and presence of small amt of algae.

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