PETROGRAPHY OF PALEOGENE CARBONATES IN KALAMULA AND KHURSHEEDABAD AREA , KAHUTA , AZAD KASHMIR

The rocks exposed in the study area are carbonates of Lockhart Limestone. The carbonates are nodular, thin to thick bedded, fossiliferous with minor intercalcations of marl. The microfacies investigation was carried out in two different geological field sections based on field and petrographic data in the area. The carbonate microfacies are, Micritic Crystalline Carbonate Mudstone-Wackstone Micrifacie (LMF-1), Mixed Bioclastic Mudstone-Packstone Microfacies (LMF-2) and Benthic Foraminiferal wacke-Packstonet Microfacies (LMF-3). The recognized fossils are Algaes, Texularia, Tokhartia sp, Opperculina, Assilina sp, Nimmulites sp, Ranikothalia sp, Mascellena sp, Nodosaria and Milliolid. The deposition of limestone with larger benthic foraminifer took place. The large Foraminifera’s and dasycladacean algae in the rocks indicate shallow marine shelf environment. The carbonate microfacies suggested limestone deposition under clastic free shallow shelf conditions. The predominantly wackstone to packstone fabric nodularity in limestone and presence of fossils suggest deposition in shallow marine environment.


Introduction
The Himalayas are formed as a result of collision between Indian and Eurasian plates.Ganssar [1] subdivided the Himalayas into Sub Himalayas, Lesser Himalayas and Higher Himalayas.The study area lies in lesser Himalayas bounded by MBT and PT (Fig. 1).The Carbonate rocks are confined to the Pir Panjal Range in Kashmir.Geographically these rocks are exposed in the Kalamula and Khursheedabad area (Fig. 2).Fused nodular fossiliferous carbonate rocks of Paleocene age are exposed in this area.
imetamorphic.The unconformities are marked while some contacts are faulted.The oldest unconformity is between Dogra Slates and Gondwana Group of Carboniferous marked by the presence of conglomerate bed (Fig. 2).Second unconformity is present between Panjal Formation of Permo Carboniferous and Lockhart Limestone of Paleocene age.Chorgali Formation which is marked in other areas is missing here and Patala Formation exhibits a faulted contact with Kuldana Formation (Fig. 2).Another unconformity is marked between Kuldana Formation of Eocene age and Murree Formation of Miocene age in the area.

Geological Setting:
The study area lies in the eastern limb of HKS in Lesser-Himalayas (Fig.  Facies were identified by correlating with classification of Folk [3] and Dunham [4].Crystalline carbonate and mudstone microfacies were also identified.Intraclasts are present in the mudstone microfacie.Three microfacies were identified on the basis of fossils.The fossil assemblage in the limestone indicates a shallow marine shelf conditions.The microfacies identified are described as below:

Materials and methods:
Carbonates of Paleocene age were selected for research work which are exposed in Kalamula and Khursheedabad areas (Figs. 2) in Betar valley.
The color of limestone is dark grey to grey in the study area.The limestone is hard and compacted.In Khumgala to Kalamula section it forms hill topography.Solution weathering and pot holes are commonly observed in the section.Calcite veins and fossils are clearly seen on the surface of the limestone.In Khursheedabad section shales are interbedded in limestone near the base (Fig. 5).Fused nodules are common in middle section and nodularity increased towards the top.The basal contact of limestone is unconformable with Panjal formation and upper contact is normal at some places with Patala Formation and at some places it is faulted with Kuldana Formation.On the basis of fossils like Algae sp, Lokhartia sp, Assilina sp, Nimmulite sp, and Milliolid sp, the formation is marked as Lockhart Limestone of Paleocene age.The field work was carried out in the study area to obtain geological data.Topographic sheet was used for the location of the rock samples collection.The dip and strike of the beds was measured by using Brunton compass.The geological hammer was used to take the samples from the outcrops.Hand lens (10x, 20x) was used for study of the megascopic features of the rock units in the field.Camera was used to take the photographs of the prominent features present on the rock units.Brunton compass, measuring tape and survey pol were used for section measurement.This research study was completed in two phases, field and laboratory work.Field work consists of 1. Rock samples collection for petrographic studies 2.
Photography of outcrop sections 3.
Recording geological data i.e. contact relationship and structural details 4.
Measurement of stratigraphic section of the area The geological and sample location map (Fig. 2) of the area was prepared using Toposheet no.43K/1 of the Survey of Pakistan.The nineteen fresh and representative limestone samples of different color and texture were selected for thin section preparation.Thin sections were studied using LEICA DM750 polarizing microscope with attached LEICA EC3 camera in the petrology laboratory of the Institute of Geology.

3.1.1Micritic Crystalline Carbonate Mudstone Wackstone Microfacie(LMF-1): Description
This microfacie is comprised of thinly laminated fractured, dark grey limestone beds with thin beds of interbedded black shales.Thin section studies show that rock sample consist of crystalline carbonate, mudstone to wackstone microfacies.Micrite and spar is the dominant constituent of the rock samples.Styolites, calcite veins, albite plagioclase and quartz grains were found in the microfacie.This microfacie is represented by four thin sections at Kalamula and five thin sections at Khursheedabad.The total thickness of this microfacie is 42 meter in Khursheedabad and is repeated two times from base to 42m and at 149m hights respectively (Fig. 5).

Interpretation
Dominating presence of lime mud indicates that this facie is deposited in low energy, calm and shallow water lagoonal environment often on the edge of channels.This micrifacie is similar to SMF-22 of Wilson [5] and [6] Flugel [7].

Mixed Biolastic Mudstone-Packstone Microfacies (LMF-2): Description
This microfacie comprised of medium bedded greyish limestone with minor shale.It consists of mudstone-packstone microfacie.Dasycladacean algae, Spirozoa Algaes, Operculina, Texularia, mixed fossil and broken fragments of fossils are found.This microfacie is represented by one thin sections at Kalamula and three thin sections at Khursheedabad.The total thickness of this microfacie is 30 meter in Khursheedabad and is repeated two times at 70m and 190m hights respectively (Fig. 5).

Sample No.
LK    [8].This microfacie is represented by three thin sections at Kalamula and three two thin sections at Khursheedabad.The total thickness of this microfacie is 28 meter in Khursheedabad and is repeated two times at 100m and 120m hights respectively (Fig. 5).

Interpretation
There is a large variety of large benthic foramaminiferas.Welldeveloped fossils indicates normal salinity.Micrite matrix shows deposition under low energy conditions relatively deeper middle shelf area.This microfacie is similar to SMF-8 and 9 based on Wilson [5] and

Depositional Settings of Lockhart Limestone:
The deposition of Lockhart Limestone with larger benthic foraminifera took place during the upper Paleocene after the transgression of the sea water in the area.Lockhart Limestone microfacies are indicative of marine shallow shelf environments.Topographically the formation forms ridges and cliffs.The Lockhart Limestone is present between the Panjal Formation and Kuldana Formation.The limestone is dirty grey to light grey on weathered surfaces and grey to dark grey on fresh surfaces.The limestone contains secondary calcite veins.The Lockhart Limestone is dominantly nodular and massive with subordinate shale intercalations.The nodular habit of the limestone seems to be of sedimentary origin.The shales and marl are interbedded with this nodular limestone in the lower part.There is a marked decrease of nodules towards the middle part of the unit.However, nodularity increases towards its top.Microfossils of foraminifer can be seen on the weathered surfaces in the form of tiny speaks less than one millimeter.The massive portions of limestone show diffused nodularity.Nodules are generally 2 -6 centimeters in long direction and 1-5 centimeter in width.Based on carbonate microfacies identification and interpretation, the Lockhart Limestone exhibits deposition under clastic free shallow shelf conditions.Presence of wide variety of fauna, predominantly wackstone to packstone fabric of rocks and nodular nature support the above interpretation.The foraminifers like Lockhartia, Assilina, Discocyclina and Ranikothalia are present in the Lockhart limestone.The larger foraminifera are known to characterize the shallow shelf carbonate environments.The Lockhart Limestone represents a shallow shelf carbonate platform as is evidenced by the occurrence of a number of larger foraminifera and dasycladacean algae in the formation.It is inferred that relatively constant water depth was maintained during accumulation of entire sequence.This is an indication of shallow shelf deposits.The inner and middle shelfs are the sub environments in which three major types of microfacies were marked which includes 1) Micritic Crystalline Carbonate Mudstone-Wackstone Micrifacie (LMF-1), 2) Mixed Bioclastic Mudstone-Packstone Microfacies (LMF-2) and 3) Benthic Foraminiferal wacke-Packstonet Microfacies (LMF-3; Fig. 6).greyish to blue in color.Limestone is hard and compacted.Weathering and dissolution features are clearly found on surface.Large pot holes are common in the formation.The formation forms cliffy topography in the area.Limestone is highly folded, faulted and fractured.Shales and marls are interbedded near the base of the formation.Nodularity decreases towards the middle part of the formation.In the middle part of the Lockhart Limestone the recrystallized fossils on weathered surface are abundant.As a result of recrystallization calcite completely replaced internal structure of the fossils.Fossils are less common on base and top of the formation.Micrite is the dominant constituent in most of the rock samples.Sparite is also present abundantly in the rock samples.Three microfacie zones were identified on the basis of fossils.In the first zone (LMF-1) fossils are absent.Micrite is the dominant constituent of the rock samples.In the second zone (LMF-2) dasycladacean algae and variety of Algaes were found in this part which mark shallow shelf depth.Third zone (LMF-3) is marked by mixed bioclast which are abundant in middle part of the formation.They are large Foraminifera which includes species of Assilina, Lockhartia, Nimmulites, Ranikothalia, Massilina, Texularia and Milliolids.These fossils indicate shallow marine shelf depositional environment for Lockhart Limestone.

Conclusion
On the basis of field and petrographical studies these conclusions are drawn:

3.3
Diagenetic Fabric of The Lockhart Limestone: Carbonate rocks are susceptible to diagenesis and alteration processes [9].The older carbonate rock exhibit dissolution and reprecipitation in response to change in chemical environment [10].The limestone are subjected to a variety of physical and chemical changes during deposition.The allochemical constituents of the carbonate rocks are changed into micrite or lime mud through boring activity of endolithic algae [11].In the Lockhart Limestone, the micritized fabric is formed by activity of benthic organisms specifically dasycladacean algae and larger foraminifera of inner and subtidal distal shelf facies.The formation of microspar has been attributed to aggrading neomorphism [12].In the Lockhart Limestone, conversion of micrite to microspar is a common phenomenon and is characterized by the development of isolated, patches of granular microspar selectively converting micrite into sparite.The Lockhart Limestone is texturaly wacke to packstone with large amount of lime mud matrix.The allochem constituents consists of a wide assemblage of large foraminifers.The abrasion and fracturing of allochems due to lithostatic pressure results formation of micrite in the rock.The compaction refers to changes in original texture of the rocks as a result of overburden pressures in shallow to deep burial conditions.During compaction bioclasts are fractured and under deep burial conditions styolites were developed (Plate 1, A).

Figure 2 :
Figure 2: Geological and sample location map of the project area.
). Lesser Himalayas are bounded by MBT towards the South and MCT towards the North.The rock units in the area are folded, MBT are comparatively less deformed and fractured.Rocks in the area are from Pre Cambrian to Quaternary and consist of sedimentary, volcanics and https://doi.org/10.26480/esmy.01.2017.36.41This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Figure 2 :
Figure 2: Paleogeographic sketch map of Paleocene-Eocene sequence (Modified after Shah, 2009).Asterisks show the distribution of Kuldana Formation of Middle Eocene in different areas.

Figure 6 :
Figure 6: Depositional model of Lockhart Limestone based on both field sections in Kahuta area.
They vary in width up to several centimeter.The fractures in the limestone are noted in the field and in the thin sections.These fractures are formed by lithostatic pressure and tectonic activity related with Himalayan orogeny.These fractures are later filled with coarse spary calcite and are termed as calcite veins.A wide variety of calcite veins and veinlets are present in almost all micorfacies of Lockhart Limestone.The Lockhart Limestone exhibits nodular bedding in the area.The individual nodules are highly irregular and are attributed to chemical compaction.The stylolites and solution seams are parallel to bedding in the Lockhart limestone indicate a diagenetic change.The presence of several diagenetic features indicate that the Lockhart Limestone of the studied area has been subjected to post-depositional low grade diagenesis.These diagenetic changes includes micritization, neomorphism (microspar, aragonite calcite transformation), dolomitization, compaction (disorientation of biocalst, pressure dissolution fabric), nature and origin of calcite filled micro fractures.4. Discussion: Transgression of sea water occurred in Paleocene on the northwestern margins of the Indian plate [13].The Paleocene Lockhart Limestone and Patala Formation were deposited in shallow marine sea in the area.The limestone of Lockhart Limestone is Paleocene Lockhart Limestone is exposed in Kalamula and Khursheedabad area which lies on the Eastern limb of Hazara Kashmir Syntaxis.Lower contact of Lockhart Limestone is unconformable with Panjal volcanics and the upper contact is conformable with Patala Formation.The Lockhart Limestone in Folk's classification is classified as bio-micrite while in Dunham's classification it is termed as wackstone to packstone.The petrographic study of the Limestone showed that the rock is composed of allochems, micrite and sparite.The fossils are recrystallized fossils are algae, opperculina, assilina sp, nimmulites, ranikothalia sp, masselena, millioid and lokhartia sp.The large Foraminifera's and dasycladacean algae in the rocks indicate shallow marine shelf environment.Three shallow shelf facies LMF-1, LMF-2 and LMF-3 were identified from bottom to top on the basis of fossils.The deposition of Lockhart Limestone with larger benthic foraminifer took place during the Upper Paleocene after the transgression of the sea water.

Table 4 .
1.1: Showing modal analysis of limestone in Kalamula section.

Table 4 .
1.3: Showing modal analysis of limestone in Khursheedabad section.

Table 4 .
1.4: Showing modal analysis of limestone in Khursheedabad section.