Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

A. H. M. Ahmad ¹

Affiliations
1 Department of Geology, Aligarlz Muslim University, Aligarh - 202 002, IN

Abstract

No Abstract.

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K. Akhtar ¹, M. Mujtaba Khan ¹, A. H. M. Ahmad ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh-202002, IN

Abstract

The Nimar Sandstone were studied with a view to understanding the nature of the Narmada  basin and its tectonic setting during an important event which took place on a global scale. The sandstones are predominantly quartzarenitcs composed mainly of several varietics of quartz, mica, rock fragments, feldspar and heavy minerals derived from the underlying Plecambrian basement. An integrated approach suggests that the Nimar Sandstone was derived from fault-bound uplifts of continental basement rocks and accumulated without much transport in the incipient rift belt of the Narmada basin.

Keywords

Sedimentology, Tectonics, Nimar Sandstone, Cretaceous, Gujarat.

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K. Akhtar ¹, A. H. M. Ahmad ¹, M. M. Khan ¹, A. Z. Khan ¹

Affiliations
1 Dept. of Geology Aligarh Muslim University Aligarh-202 002, IN

Abstract

No Abstract.

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A. H. M. Ahmad ¹, G. M. Bhat ², Neshat Jehan ¹, A. F. Khan ¹, Aabiroo Majid ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh – 202 002, IN
2 Department of Geology, University of Jammu, J & K, IN

Abstract

The Habo Dome Sandstone of Chari Formation has been analyzed for petrofacies and diagenetic history. The sandstones are generally medium to coarse grained and moderately to well sorted. These sandstones are composed of several varieties of quartz, feldspar, rock fragments, micas and a suit of heavy minerals derived from the Aravalli Range and Nagarparkar massif. The petrofacies analysis reveals that these sandstones belong to the continental block, recycled orogen and rifted continental margin tectonic regime.

During mechanical compaction rearrangement of grains took place and point and long contacts were formed. The sandstones were cemented by calcite, iron oxide, silica, chalcedony and glauconite cements in order of abundance. Different graphs of porosity versus depth suggest a depth of burial in the range of 615 to 769m.

Keywords

Habo Dome, Chari Formation, Petrofacies, Diagenesis, Kachchh, Gujarat.

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A. H. M. Ahmad ¹, G. M. Bhat ², S. Rais ¹, C. Saikia ¹, A. E. Khan ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN
2 Postgraduate Department of Geology, University of Jammu, Jammu - 180 006, IN

Abstract

This paper describes 10 microfacies types in the Jumara Coral Limestone and Echinoderm Packstone Members (early Late Bathonian age) of Jhurio Formation of the Jumara Dome. The temporal distribution of these microfacies associations reflects an ideal shallowing upward sequence, representing a system of bioclastic bars separating the basin from lagoon environment. Evidence suggests evolving of this bioclastic bar system upward into an oolitic Bar-to-Bank system. Three types of cements (bladed to fibrous, blocky and syntaxial overgrowth) occur in these carbonates. The study also reveals that chemical compaction followed the two phases of early mechanical compaction that largely governed porosity of these limestones. Diagenetic signatures in these carbonates suggest that marine phreatic, under saturated fresh water phreatic and mixing marine fresh water phreatic environments dominated but deep burial diagenesis also played its role in shaping these rocks through time. Evidence suggests that both primary and secondary porosity exist in these carbonates, which determine the permeability in these rocks.

Keywords

Carbonates, Depositional Environments, Diagenesis, Jurassic, Jumara Dome, Kachchh, Gujarat.

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A. H. M. Ahmad ¹, G. M. Bhat ², A. F. Khan ¹, C. Saikia ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN
2 PG Department of Geology, University of Jammu, Jammu - 180 006, IN

Abstract

The sandstones of the Upper Katrol Formation were studied with a view to understand the nature of Kachchh basin in relation to provenance and tectonic setting in the vicinity of Nakhtarana area. These Upper Katrol sandstones are fine to coarse grained, moderately to poorly sorted, sub-Angular to sub-Rounded and of moderate sphericity. These sandstones are composed of several varieties of quartz, feldspar, rock fragments, micas and a suite of heavy minerals derived from the Aravalli Range and Nagarparkar massif. Our study reveals that these sediments were derived from the continental block orogen provenance characterized by collision suture and fold thrust belts. Three types of cement encountered in this study include iron oxide, calcite and silica. Evidence of diagenetic modifications suggests an early stage of burial to a depth of 748 to 932 m for these sandstones. Porosity reduction is mainly due to early stage mechanical compaction and subsequent pervasive calcite and Fe-Calcite cementation, which was followed by the late stage authigenic kaolinization in the secondary pore space.

Keywords

Katrol Formation, Kimmeridgian, Sandstones, Petrography, Diagenesis, Tectonic Provenance, Nakhtarana, Gujarat.

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A. H. M. Ahmad ¹, G. M. Bhat ², M. Shamim Khan ¹, S. Hilal Farooq ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN
2 PG Department of Geology, University of Jammu, Jammu, IN

Abstract

The paper embodies results of petrofacies, detrital mineralogy, texture and diagenetic aspects of glauconitic sandstones of Kheinjua Formation of Vindhyan Basin, Son valley These glauconitic sandstones consisting of various types of quartz, feldspar, rock fragments, mica and a sulte of heavy minerals, are medium to very fine grained, and well to moderately well sorted These sediments including glauconite grams are generally subangular to subroundcd with a few grams bang well rounded These sandstones are well compacted and dominated by interpenetrative contacts and are maniy cemented by iron cement with small amount of glauconite and silica cement The existing optical poroslly has developed due to dissolution of Iron cement, feldspar and rock fragments These observations suggest progressive compaction, which initiated at the sediment-water interface and continued till deep bunal diagenesis in a rapidly subsiding basin

The plots of petrofacies in Qt-F-L, Qm-F-Lt, Qp-Lvm-Lsm and Qm-P-K ternary diagrams suggest mainly basement uplift source (craton interior) In a rifted continental margin basin setting, which has also received sediment Input from recycled orogen provenance The plot of various quartz types on diamond diagrarn after Basu et a1 (1975) reflects derivation of the sediments from the plutonic and middle to high-rank metamorphic terrains Besides, Lower part of the Semri Group, the most probable provenance of these sandstones IS Bijawar metasedimentary and Bundelkhand Gneissic complexes, which bordered the basin in the north and northeast.

Keywords

Sandstones, Petrofacies, Provenance, Tectonic setting, Vindhyan, Son valley, Central India.

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M. Masroor Alam ¹, M. E. A. Mondal ², A. H. M. Ahmad ²

Affiliations
1 Department of Civil Engineering, Aligarh Muslim University, Aligarh - 202 002, IN
2 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN

Abstract

This study mainly deals with the sandstone lithofacies and petrofacies of Jahaj-Govindpura Formation of the Raialo Group, rich in volcaniclastics, exposed near Hathori village. These cross and planar bedded sandstones are medium grained poorly sorted, and are cemented mainly by iron oxide, carbonate and by matrix rich in phyllosilicates and vitrofelsitic material. The sandstone petrofacies arc rich in detrital modes suggestive of metamorphic source terrain as well as juvenile volcanic 1ithic fragments with textual and mineralogical characteristics typical of neo-volcanic source which was very near to the basin. The underlying clastics of Raialo Group and the overlying formations represented by the Alwar and Ajabgarh Groups of the Jahaj-Govindpura volcanics respectively, do not have a notable amount of volcanic lithics. This suggests that the volcanism was intrabasinal, took place for a shorter time period and was not vety explosive. While the sedimentation continued in this basin, detritus from the highs exposing the BGC and Aravalli Supergroup of rocks in SE and SW were mixed with intrabasinal volcaniclastics. These volcanic highs then may have been carapaced by younger sediments which were deposited in linear rift zones and were eroded from an "Accreted Basement Provenance" comprising Banded Gneissic Complex and Aravalli Supergroup in a short time span.

Keywords

Syn-Depositional Volcanism, Sandstone, Lithofacies, Petrofacies, Tectonic Setting, Bayana Basin, Aravalli-Delhi Fold Belt, Rajasthan.

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A. H. M. Ahmad ¹, M. Masroor Alam ², M. Haris Azim Khan ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, Uttar Pradesh, IN
2 Geology Section, Department of Civil Engineering, Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh, IN

Abstract

The Bayana Sub-Basin comprises thick sequence of metavolcanics and metasedimentary rocks belonging to Delhi Supergroup. The deposition of sediments took place in response to vertical tectonism during Middle Proterozoic in fluvial and shallow marine environments. The rocks are mainly clastics and include conglomerate, sandstone and shale.

The conglomerate lithofacies and petrofacies were studied with a view to understand the tectonic setting of the provenance and the basin. The conglomerate matrix consist of framework detrital grains such as several varieties of quartz followed by rock fragments, mica, feldspar, and heavy minerals. The Qt-F-L, Qm-F-Lt, Qp-Lv-Ls and Qm-P-K diagrams suggest continental block, recycled orogen provenance, rifted continental margin type of basin setting and overall maturity and stability of the continental block provenance. The cement phases in conglomerate matrix consist of iron oxide, silica, carbonate and barite. Dominance of floating, point and long contacts indicates that the sand grains did not suffer much pressure solution.

Keywords

Conglomerate, Petrofacies, Diagenesis, Bayana Sub-Basin, Delhi Supergroup, Bharatpur, Rajasthan.

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A. H. M. Ahmad ¹, M. Masroor Alam ², M. Haris Azim Khan ¹, A. Shahab M. Saeed ³

Affiliations
1 Department of Geology Aligarh Muslim University, Aligarh - 202 002, U P, IN
2 Geology Section, Department of Civil Engineering, Aligarh Muslim University, Aligarh - 202 002, U P, IN
3 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, U P, IN

Abstract

The studied rocks form a part of Upper Rewa Sandstone, which overlies the Kaimur Sandstone in northwest part of the Vindhyan basin, exposed in various isolated ridges around Baretha area of Bayana, Bharatpur district of Rajasthan The sandstones are medium to fine grained and moderately well sorted to well sorted The sandstones consist of various types of quartz followed by feldspar, rock fragments, mica and heavy minerals The petrofacies in Qt-F-L, Qm-F-Lt, Qp-Lv-Ls and Qm-P-K ternary diagrams suggest mainly basement uplift source of craton intenor in rifted continental margin type basin setting with very low input from recycled orogen provenance

The sandstones are well compacted and dominated by interpenetrative contacts and are mainiy cemented by silica with very small amount of carbonate and Iron oxide Quartz overgrowths are well developed on monocrystalline quartz than polycrystalline ones Coarser fraction of detrital quartz grains have sequestered authigenic overgrowths covering more of its grain boundary and are thicker as compared to finer grains Dissolution of quartz along gram boundaries and silica rich compaction pore water seems to be the main source of silica.

Keywords

Sedimentary Petrology, Petrofacies, Diagenesis, Rewa Sandstone, Vindhyan Basin, Rajasthan.

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A. H. M. Ahmad ¹, A. F. Khan ¹, C. Saikia ¹

Affiliations
1 Department of Geology, AJigarh Muslim University, Aligarh-202002, IN

Abstract

The Middle Jurassic Athleta Sandstone of Jhurio Dome is mainly medium grained, moderately sorted to moderately well sorted, subarkose and is composed of four major lithofacies representing near shore tidal environments. Iron oxide, silica and glauconite cements mark the sandstones. Compaction is mainly mechanical and sandstones show good amount of porosity. Porosity reduction is mainly due to mechanical compaction in the early stage of diagenesis and subsequent pervasive iron oxide cementation.

Keywords

Depositional environment, Athleta Sandstone, Middle Jurassic, Jhurio Dome, Kachchh, Gujarat.

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A. H. M. Ahmad ¹, A. Majid ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN

Abstract

The Kachchh Basin is a pericratonic rift basin situated at the western margin of the Indian plate. The Habo Dome embodies an important exposure of Bathonian to Kimmergian sediments among the Kachchh Mainland exposures. Based on vertical facies transitions, facies associations were documented: mixed shallow marine (Facies association 1), shoreface and lagoon deposits (Facies association II) and subtidal innershelf below fair weather wave base (Facies association III). The documented facies associations reflect that Habo Dome sediments deposited in a variety of environments from shallow marine to fluvio-deltaic and were strongly influenced by fluctuation of relative sea level. The dominance of floating grains and point contacts in the sandstone indicate that detrital grains do not show much pressure effects as a result of either shallow burial or early cementation. The sandstones were cemented by iron oxide, carbonate and silica in order of abundance. Three types of cements, blocky, rim and fibrous cement occur in the studied limestone representing phreatic, fresh water phreatic and deep burial diagenetic stages. Neomorphism and micritization are common. Both primary and secondary porosity exists in these sediments. Different graphs of porosity versus depth suggest a depth of burial in the range of 615-769 m.

Keywords

Sandstone, Facies Analysis, Depositional Environment, Petrography and Diagenesis, Kachchh, Gujarat.

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C. Saikia ¹, A. H. M. Ahmad ¹, S. M. Wasim ¹

Affiliations
1 Department of Geology, Aligarh Muslim University, Aligarh - 202 002, IN

Abstract

The Bayana Basin forms the eastern most limit of north Delhi fold belt covering parts of northeastern Rajasthan. The deposition of sediments took place during middle Proterozoic in fluvial and shallow marine environments. The rocks are mainly clastics and include conglomerate, sandstone and shale. During mechanical compaction rearrangement of grains took place and point and long contacts were formed. The sandstones are cemented by iron oxide, silica, carbonate and barite. The porosity has developed due to dissolution of iron, carbonate cement and feldspar grains. Dissolution of quartz along grain boundaries and silica rich compaction pore water seems to be the main source of silica. These observations suggest progressive compaction which initiated at the sediment water interface and continued till deep burial diagenesis in a rapidly subsiding basin.

Keywords

Facies Controlled Diagenetic Evolution, Delhi Group, Bayana Basin, Rajasthan.

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