Petrography and Provenance of the Sub-Himalayan Kuldana Formation: Implications for Tectonic Setting and Palaeoclimatic Conditions

: In this paper, the depositional environment, age, and tectonic context of the Sub-Himalayan Kuldana Formation are discussed in detail. To determine the Kuldana Formation’s depositional environment, age, and tectonic setting, sedimentological, palaeontological, and petrographic investigations have been conducted accordingly. The Kuldana Formation lithologically consists of both siliciclastic and carbonate rocks. Petrographically, the Kuldana Formation’s sandstone is divided into litharenite and feldspathic litharenite petrofacies. The sandstone plots on the QtFL and QmFLt suggest that the sandstone of the Kuldana Formation derived from a recycled orogen provenance ﬁeld that developed during the collision of the Indian and Eurasian plates in the Lesser and Higher Himalayas. The plots in the diamond diagram further demonstrate that the detritus of the Kuldana Formation was derived from low and middle-to-upper rank metamorphic rocks of the Himalayas. Throughout the deposition of sandstone, paleo-climate conditions were semi-humid to semiarid.


Introduction and Geological Setting
The Himalayas were formed by the collision of the Indian and Eurasian plates during the Paleogene [1][2][3]. The Indian Plate traveled about 5000 km from south to north before Hazara Kashmir Syntaxis (HKS) is an antiformal structure that developed in the Sub-Himalayan region due to ongoing Himalayan Orogeny. HKS is comprised of older rocks in the limbs and younger rocks in its core [12,13]. As shown by steep slopes and locally anomalous terrain of the recycled orogen, HKS is an uplifted area [14,15]. The Yadgaar Section lies in the core of HKS (Figure 1b) and is bounded by latitudes and longitudes of 34 • 24 58 N to 34 • 25 49 N and 73 • 29 03 E to 73 • 29 04 E, respectively. The Yadgaar Section contains shallow marine-continental/fluvial sedimentary deposits of Cambrianrecent [16].
The boundary between the Paleocene and Eocene periods is marked by the ophiolitic and volcanic detritus that were deposited on the passive margins of India and Eurasian plates [17]. The collisional basins on both sides of the proto-Himalayan mountain range were filled with sediment after the rise of the mountain chain. The Early Eocene Chulung La Formation was deposited in the topmost portion of the "piggyback" basin (a small sedimentary sub-basin developed in the foreland basin, above a moving thrust sheet). In this Tethys Himalayan passive-margin succession, fluvial-deltaic red beds were deposited [13]. The red beds of the Eocene-Miocene quartzo lithic deltaic facies include sedimentary and low-grade metasedimentary material that derived from pro to Himalayan thrust sheets as well as volcanic-ophiolitic deposits associated with the suture zone. The subaerial foreland basins of the Indian continent are the distal analogs of the Neogene-aged Siwalik to the Quaternary molasses of the Indo-Gangetic Plain ( Figure 2). They are underlain by the continent's crust [18]. Dickinson and Suczek [19] first developed the provenance system, and later Dickinson [20] refined it. The petrographic study of the detrital sandstone composition is an excellent approach to determining its tectonic settings, source type, and paleo-climatic conditions (Figures 3 and 4) [11,12,[21][22][23].
The Paleogene rocks are divided into two groups: marine (shallow shelf) and transitional (deltaic). In the Yadgar Section, Muzaffarabad area, the total thickness of the Kuldana Formation is 1150 m (Figures 2, 3i and 5). The Kuldana Formation has a dis-conformable contact with the underlying Early Eocene Chorgali Formation [24][25][26][27][28][29] (Figure 4b), and is dominantly comprised of variegated-colored shales, siltstone, sandstones, and lenses of limestone. The upper contact of the Kuldana Formation is found unconformable with the Murree Formation (Figure 4d). Previous studies based on biostratigraphic investigations conducted in the Murree, Muzaffarabad, and Balakot districts dated the Kuldana Formation between 53 and 43 Ma (Early-Middle Eocene) [22,30]. The Eocene strata (~55-48 Ma) were deposited in a foredeep zone [12]. They further proposed that the detritus of these sediments was derived from the Kohistan-Ladakh arc (KLA), the Lhasa Block (LB), and the Karakoram Block (KB) of the Asian terrane. Previous researchers also recovered the fossils of vertebrates, foraminifers, bivalves, and gastropods from various sections of the Kuldana Formation [31][32][33].
The petrography of detrital sandstone rocks is an important method for determining siliciclastic rock provenance and pinpointing mineralogical composition. Accurate mineralogical calculations are critical in the petrological investigation of rocks containing clay deposits for engineering and industrial purposes [34]. The fundamental goal of sand-stone petrography is to determine the lithologic qualities of the source rocks and the tectonic context [19,21,[35][36][37]. To recognize the tectonic settings of Himalayan strata, modal values were used [38,39]. The most important component in identifying provenance is understanding the tectonic settings [40,41]. Furthermore, the tectonic settings of sedimentary environments influence variables affecting sandstone composition, and some of these variables remain unchanged even after a long period of severe-tropical weathering. As a result, the composition of HFB sandstone is important for understanding the genesis of the orogenic belt, depositional environment, and geotectonic settings of the region. Kuldana Formation/Balakot Formation (Pakistan), Upper Subathu Group (Jammu and Kashmir and Himachal Pradesh, India), and Upper Bhainskati Formation (Nepal; Figure 2) [11,42]. Various geoscientists have studied the Kuldana Formation and its coeval Upper Subathu Group in the HFB to determine its provenance, tectonic development, and biostratigraphy [12,13,16,43]. However, they studied the Kuldana Formation and its coeval formations in different areas to determine its individual aspects. The depositional environment, age, and tectonic setting of the Kuldana Formation in the Yadgaar region have not yet been examined using a combined sedimentological and palaeontological approach with detailed mineralogical composition. The current study's goal is to determine the depositional environment, age, and tectonic setting of the area during the deposition of the Kuldana Formation by detailed sedimentological, palaeontological, and mineralogical investigations.

Materials and Methods
Two-week fieldwork of the Yadgaar Section was carried out (Figures 3 and 4). The Yadgaar section extends from Muzaffarabad city to Ghori village in Pakistan (Figure 1b).
Fieldwork includes identifying the formation and marking the top and bottom of the Kuldana Formation ( Figure 5). Photographs of the field and outcrops were taken using a digital camera. The petrological investigation of the sandstone was used to deduce the climatic conditions, tectonic settings, and source types during the deposition of the Kuldana Formation. About twenty (20) representative fresh Kuldana Formation sandstone and limestone samples were collected from various locations for thin section preparation in the laboratory. A petrographic microscope was used for the thin section investigation (Leica DM-750P with an attached Leica EC3 camera, Leica Microsystems Ltd., Heerbrugg, Switzerland)). The Gazzi-Dickinson method was used to quantify sandstone components [44,45]. Aside from this, seven samples of fossiliferous limestone from the Kuldana Formation were also examined under a petrographic microscope. The texture and composition of limestone, such as the texture and composition of sandstone, reflect its depositional setting. The schemes of Dunham [46] and Folk [47] were used to classify the limestone of the Kuldana Formation.

Field Study
The Kuldana Formation is composed of mudstone (Figure 3a In certain locations, variegated-colored mudstones were extremely deformed and had been transformed into shales, with a pencil-like cleavage (columnar shales; Figure 3j-l). The Kuldana Formation coursing upward succession was transported by the river system and subsequently deposited in deltas. At the base, mudstone and shale were deposited, followed by sandstone (Figure 4c). This suggests a coarsening upward sequence transported by the river system and ultimately deposited in deltas.

Petrography of Sandstone Rocks
Using the method of Gazzi-Dickinson, the sandstone of the Kuldana Formation is classified is arenite. This is because each sample induced less than 15% matrix ( Table 1). The ternary diagram of Folk [47] was used to determine the model values of quartz, rock fragments, and feldspar ( Figure 6). Except for three samples, all of the samples are classified as litharenites ( Figure 6a; Table 1). Using fragments of volcanic-plutonic, sedimentary, and metamorphic rock, litharenite and feldspathic litharenite are further subdivided. Twenty samples make up the phyllarenite, seven samples comprise the sedlithite, and a single sample was identified as volcanic arenite (Figure 6b). The Koldana Formation has two types of carbonate rocks: limestone and dolostone. According to the Folk [47] classification, the limestone is classified as biomicrite. In this formation, polycrystalline quartz decreases from base to top, whereas monocrystalline quartz progressively increases (Figure 7). Alkali feldspar, such as microcline and perthite are rarely found unevenly, while samples from the middle to the top are rich in orthoclase. Fragments of igneous rock are abundant at the base-middle and begin to decrease upwards. Fragments of metamorphic and sedimentary rock are abundant in the base and middle portion of the stratum and decrease towards the top. In terms of accessory minerals, hematite predominates in the middle portion of the formation, while muscovite, chlorite, rutile, tourmaline, and a few others are rare and unevenly distributed. There is a little increase in the percentage of calcite in the middle portion of the formation, although clay and chlorite are only identified in the top portion. Feldspar Rock Fragments
The Kuldana Formation litharenite is composed of sub-rounded, angular-sub angular, and quartz grains. In general, these grains are divided into three groups: non-undulating monocrystalline quartz, undulating monocrystalline quartz (Figure 10a), and polycrystalline quartz (Figure 10b). Due to metamorphism, quartz grains have a stretched and strained quality, which is shown by the relatively small amount of monocrystalline quartz. Contact between quartz grains is observed to be planar and concavo-convex. In the feldspathic litharenite, alkali feldspar, and plagioclase are the predominant types of feldspar (Figure 10c). Alkali feldspar comprises microcline perthite (Figure 10d

Phyllarenite
Two feldspathic litharenite samples are distinguished from phyllinite (K29b and K20). The proportion of quartz ranges from 32 to 37%, the proportion of rock fragments from 13 to 20%, and the percentage of feldspar from 6 to 7%. 0 to 12% is the percentage range for matrices (Table 1).

Sandstone Composition of the Kuldana Formation
The modal mineralogical composition of the Kuldana Formation sandstone reveals a clear trend from base to top. It was noticed that the proportion of polycrystalline quartz and volcanic, sedimentary, and metamorphic rock fragments decreased gradually. In contrast, a rise in monocrystalline quartz and orthoclase has been noticed in the sandstone of Kuldana Formation. The detrital components observed in the sandstone of Kuldana Formation suggest compositional diversity, hence explaining its source type.

Interpretation
Recycled orogenic provenance was suggested for the Kuldana sandstone by analyzing QtFL and QmFLt ternary diagrams and the recycled orogenic origin of transitionalquartzose (QmFLt plot; Figure 6c). Stratified rocks may be recycled through tectonic uplift, deformation, and erosion [20]. Due to the Himalayan Orogeny, the Kuldana Formation was deposited in the Foreland Basin. The mineral composition of the sandstone reflected the geological setting of the area. Non-undulatory quartz grains originate from granite, but undulatory quartz grains may be derived from high-grade metamorphic rocks [10]. Basaltic clasts of volcanic rocks are likely associated with the Panjal Formation (Permian) or other basaltic Himalayan rocks [50]. The Panjal Formation consists of carbonates and basaltic lava flows. The presence of heavy minerals in clastic sedimentary rocks is noteworthy due to the fact that these minerals serve as provenance markers [51]. Most reworked sediments have subrounded or rounded grains [52]. Zircon grains in the sandstone of the Kuldana Formation are rounded to sub-rounded, suggesting that they originated from igneous and metamorphic processes. The tourmaline family of minerals exhibits a vast spectrum of colors and chemical compositions. Due to their diverse chemical components, they all display pleo-chroism [53]. The formation contains subrounded grains of dravite that are yellow-brown. The occurrence of epidote in Kuldana Formation sandstone may have originated from metamorphic rocks, such as green-schist facies.  Table 3. Kuldana Formation evaluation, based on the following petrographic and other key parameters.

Total Lithic Fragments (Lt = L + Qp)
Rutile grains have a sub-rounded shape, indicating that they are likely to have originated from reworked sediments. According to Bossart [54], the presence of sericite, chlorite, and pumpellyite in the reed beds of the Balakot Formation indicates pumpellyite-grade metamorphism. Thin sections of the Yadgaar Section also exhibit the presence of pumpellyite, sericite, and chlorite, which clearly indicates prehnite-pumpellyite metamorphism. Zircon, rutile, and apatite all indicate an igneous and metamorphic origin [55]. In thin sections, tourmaline, quartz, and a small quantity of feldspar can also be observed. The origins of tourmaline are pegmatites, schists, and granites [56]. Quartz and feldspar indicate an orogenic origin from which these minerals and the large river sediments reached the foreland basins [57]. In general, the characteristic quartz lithic petrofacies show that the source type and paleoclimatic environment were almost constant throughout the deposition of Kuldana Formation sandstones.

Petrography of Carbonate Rocks
The carbonate rocks of the Kuldana Formation are classified into dolostone and limestone. The limestone is characterized as biomicrite by using Folk [47] classification. However, based on the textural classification of limestone, the limestone of the Kuldana Formation is distinguished as mudstone, wackstone, and packstone. The bioclasts include Nummulites atacicus, Nummulites mamillatus, crinoids, Nummulites discorbina, Nummulites djodjokartae, Nummulites vascus, Lockhartia pustulosa, gastropods, miliolids, brachiopods, Globigerinoides spp., bivalves and ostracodes suggesting a Middle Eocene to Oligocene age for the Kuldana Formation ( Figure 11). The diagenetic features including micro-fractures, pressure solution and stylolites of low and high amplitude can also be observed. The mudstone contributes 1-5 m thickness (Figure 4).
Miliolids and an abundance of micrite matrix are indicative of shallow water lagoonal platform environments [63]. A high proportion of micrite suggests that wave energy or current was insufficient to dissolve the fine matrix in a specific area [64,65]. Mudstone facies are deposited in an environment with low energy, either in protected seas or beneath a fair-weather base (calm water) [66].
The considerable quantity of mud matrix in the sediments suggests a slow rate of sedimentation [67]. As with benthic foraminifera, micritic facies suggests a relatively shallow marine environment [65]. In a few instances, the back reef or lagoon is an ideal environment for micritization [68]. The deposition of micrites may be considerably facilitated by a calm and low-energy water environment [69]. Silicification may be triggered at any stage of digenesis, from early to late. The presence of chert in the lower portion of the Kuldana Formation's limestone also implies a shallow marine environment with a terrestrial input source (river water with a high silica concentration) (Figure 11). Laschet [70] shown that "terrestrial" is the most important source of silica in shallow marine environments. This petrofacies is deposited in the surroundings of the inner ramp to the outer ramp.
A low proportion of bivalves and Nummulites among the gastropods indicates that deposition occurred in the deeper portion of the marine shelf and at the lagoon's edge [79]. There is an abundance of benthic foraminifera in shallow marine environments.
The presence of fragmented skeletal remains suggests that the depositional environment may have been somewhat disturbed. The association of gastropods and bivalves suggests brackish, lagoonal facies. One of the most distinguishing features of the lagoon is that almost all gastropod shells are filled with thin cement [80]. The abundance of nummulites and associated foraminifera indicated deposition in an open sea or inner-ramp environment [81]. Detrital monocrystalline quartz grains indicate a slope environment. According to Dunham [46], wackstone is a carbonate rock with a mud-supported structure and low hydraulic energy of deposition.

Interpretation
This petrofacie consists of ostracods that evolved between the Late Paleozoic and the Cenozoic [82]. Ostracods inhabit a variety of environments, including marine, transitional, and even freshwater. They are widespread from the equator to the polar seas and are found at different depths ranging from the shoreline to the bathyal zone [76]. Initially, brachiopods are inhibited at moderate water depths, usually above seamounts. Occasionally, they are transported as bypass margins from their original place to the slope angle under the influence of gravity. They eventually settled at the base of seamounts. The habitats of bivalves are diverse, ranging from nearshore to offshore conditions and even to shoral environments [83]. The features of these microfacies reveal that deposition occurs under conditions of slightly higher energy (Figure 12).

Tectonic Settings and Provenance
In the middle-late Eocene, detrital sedimentary influx supplied the Himalayan Foreland basin of Indo-Pakistan with a cover sequence dominated by sandstone, siltstone, limestone, and shale facies. In the Indian areas of Jammu and Himachal Pradesh, these deposits are located in the middle-upper Subathu Formation. The Middle-upper Subathu Formation is further subdivided into Kalakot member/zone II-V (middle Eocene) and Arnas member/zone VI-V (late Eocene) (middle Eocene-early Miocene). The Kuldana Formation is stratigraphically comparable to the lower-middle Subathu Formation in the Kohat, Hazara, and Kashmir regions (Figure 2) [84]. Typically, members of the late Kalakot Formation and the early Arnas Formation are identical to those of the Kuldana Formation.
In accordance with Dickinson [85], ternary diagrams of QtFL and QmFLt are used for provenance analysis. The QtFL diagram is filled with plots having recycled orogens as their origins. It suggests that transitional-quartzose recycled orogenic material is the source of recycled quartzose orogenic material ( Figure 13). The sandstone contains fragments of igneous, metamorphic, and sedimentary rocks, among many others. Previous research determined that volcanic rock fragments from the upper Subathu Formation in the Shimla Hills are of ophiolitic origin. The presence of volcanic and metamorphic clasts in the Subathu Formation, Kasauli Formation, Dagshai Formation, and Balakot Formation in the HFB indicated a recycled orogenic provenance [87]. They proposed an arc-type ophiolite genesis for these formations. They also argued that ophiolitic and metamorphic detritus may have been recycled from the Indus Suture Zone and Himalayan thrust sheets from the north, indicating the closing of the Ceno-Tethys Ocean. Previous studies on the sedimentary sequence of the passive continental margins revealed the presence of volcanic, metamorphic, and metasedimentary detritus, indicating a rapid rate of sedimentary accumulation induced by a recycled orogeny and also indicating the Ceno-Tethys Ocean closing event [13].
However, the present study revealed the presence of metamorphic and (basaltic) volcanic clasts in the sandstone of the Kuldana formation that were derived from the Lesser and Higher Himalayas (Figure 9g). While sedimentary rock fragments (sandstone, slate, and carbonate clasts) were derived from the Cambrian-Eocene in age, they derive from the Tethyan succession. Throughout the Himalayas, sedimentary and low-grade metamorphosed rocks of the Cambrian-Eocene Tethyan succession are exposed [16].
By using the modal data in a diamond diagram of Basu [35], the sediment source and tectonic setting have been determined (Figure 13a; Table 1). All sandstone samples had a mean of Qnu66.4 Qu23.4 Qp > 310.1. In sandstone, non-undulatory monocrystalline quartz (Qnu) is more prevalent than undulatory and polycrystalline quartz (Qp). Sandstone seems to include a greater proportion of monocrystalline quartz (Qnu) with non-undulating surfaces than monocrystalline (Qu) and polycrystalline (Pc) (Qp).
Qnu is more abundant in the Kuldana Formation, suggesting that plutonic activity was the source of the sandstone (granite) (Figure 13c). According to Basu [35], Qp and grain size have a strong correlation. Twenty sandstone samples from the Kuldana Formation seem to have provenances of mid-to-upper rank metamorphic layers, while seven samples have provenances of low-rank metamorphic strata, as shown by the results of the current study ( Figure 13a). The Himalayas are the source of plutonic and metamorphic rocks based on these sediments.
In the northwest Himalayas, the lower Subathu Formation consists of interbedded shale and siltstone with angular quartz, muscovite, and carbonate-ferruginous cementing material. The lower portion of the Subathu Formation may consist of reworked carbonates, whereas the percentage of limestone intercalations increases upwards [78]. In Kashmir, the Yadgaar section of the Upper Indus Basin is composed of litharenite and feldspathic litharenite sandstones, suggesting a re-cycled orogenic origin and semiarid-semihumid environments (Figure 13b).
The presence of metamorphic clasts, such as schists, greenstone, gneiss, and quartzite, marks the top and bottom of the Kuldana Formation sandstone. Due to the rise of the Lesser and Greater Himalayas, igneous and metamorphic fragments may have formed. However, limestone fragments likely originated in the Tethyan Himalayas. This may also explain why there are so many biotite fragments present.

Paleoclimatic Conditions
The paleoclimatic condition of the Kul-dana Formation is interpreted based on the map presented by Suttner and Dutta [86]. According to an examination of the bivariant log/log plot between Qp/(F + L) and Q/(F + L), the majority of the values fall into the semi-humid domain (Figure 13b). In contrast, a few of the diagram's semiarid regions are typically suitable for these climatic conditions (Figure 13b). Comparing Qp/(F + L) with stratigraphic extents to Q/(F + L), Qp/(F + L) displays a slightly decreasing trend up section. This shows that the composition becomes less developed as it moves up. In addition, the Grantham and Velbel index of weathering (Wi = c × r) and the diagram of Syangbo and Tamrakar [88] (Figure 13c), Wi = 0 and 1 are typical field plots for sandstone.
Depending on the prevailing climatic conditions, the relief under subhumid conditions was either low to moderate or considerable. Suttner and Dutta [86] schemes may be used to infer paleo-climatic conditions from the compositional maturity of sandstone (Figure 12d). According to their QFL ratio (65:27), they were generated in semi-humid circumstances, and their compositional maturity varies from low to moderate (Table 2) Sandstones of the Kuldana Formation include a high proportion of calcite cement (9-25%) and clay (2-11%) ( Table 1). Sandstone contains carbonate grains of detrital origin, indicating that calcite and dolostone crystallized from detritus or a primary cement. Large rivers in semi-arid regions convey these carbonate pieces ( Figure 14). The red color of the majority of river sediments that accumulate in semi-arid regions is a result of hematite. Temperature and humidity may modify less-stable minerals, but excessive humidity can preserve them, according to Boggs Jr. and Boggs [89]. As a result of the slow erosion speed of grains, he predicted that chemical and physical weathering would be boosted on gentle slopes and low relief, but fast erosion would be encouraged by debris on steep slopes and high relief before its notable oxidation.
In each scenario, thrusting (Figure 15), rapid sedimentation from rivers, or climatic humidification might have countered the uplifting of the source regions ( Figure 14). The feldspar granules in the Kuldana sandstone are quite numerous in comparison to the quartz grains. The reason for this is that they are able to weather the semi-humid environment. Subsequently, the Kuldana Formation was deposited primarily under semi-humid conditions (Figures 14 and 15). In the Subathu Formation limestone, foraminifera make up a majority of the bioclasts transported by waves and tides into the coastal environment. Possible deposition of trace fossils in littoral-subtidal zones [42]. These settings are comparable to those in the Persian Gulf, where a marine ramp environment associated with the subsidence has been identified. Foraminifera bioclasts were reported in the shallow marine Kuldana Formation of our study area and redeposited throughout the transgression and regression periods. Variegated limestone and shale facies suggest a coastal barrier and lagoonal environment, which may be linked to storm/tidal inlets. However, in the Shimla hills region, it is believed that these sediments were deposited in shelf turbidities [86] (Figure 2). In the study area, carbonate layers of the Kuldana Formation show deposition in an inner-outer ramp environment. The presence of limestone lenses indicates deposition in a neritic-bethyal setting. However, the presence of limestone lenses in sandstone and shales indicates neritic to bathyal depositional environments. The sediments are transported via a river system and ultimately deposited in a delta environment, as shown by a coarsening succession of detritus. On the top of the Subathu Formation is a forebulge unconformity, which indicates that the sediments were uplifted before the deposition of the Dagshai Formation/Murree Formation ( Figure 15). Unconformity has been identified as well, which may be regional (Figure 2). Late Paleocene foreland basin sediments of the Subathu Formation are deposited in coastal off-lap environments. The sediments deposited in this foreland basin derived from both the Indian and Asian Plates [84]. Based on the detailed investigation, it is possible to conclude that the Kuldana Formation originated in a neritic-deltaic environment with a northern source (Figures 2 and 15). Previous researchers observed the presence of gastropods (pyramidellidae), miliolids, Nummulites, Lockhartia, ostracods, bivalves, brachiopods, Lockharia pustulosa, and Neorotalia viennoti [31,32]. They assigned the Middle Eocene age to the Kuldana Formation. However, the present study showed the presence of bivalves, brachiopods, crinoid, gastropods, Globigerinoides spp., Lockhartia pustulosa, miliolids, Nummulites atacicus, Nummulites discorbina, Nummulites mamillatus, Nummulites djodjokartae, Nummulites vascus, and ostracodes suggesting that the age of Kuldana Formation is Middle Eocene-early Oligocene.

Conclusions
The following findings are based on petrographic, sedimentological, and paleontological investigations. (1) Petrographically, the Kuldana Formation sandstone is divided into litharenite and feldspathic litharenite. The ternary diagrams QtFL and QmFLt indicate a recycled orogen provenance field for the Kuldana Formation sandstone. The Kuldana Formation clastic sediments influx derived from low and middle-to-upper rank metamorphic rocks of the Lesser and Higher Himalayas under a semiarid to semi-humid climatic conditions. (2) The Kuldana Formation limestone is characterized as mudstone, wackstone, and packstone, and it was deposited in an inner-outer ramp setting of the Ceno-Tethys Ocean. Based on the presence of micro-fossils, the Kuldana Formation has been assigned a Middle Eocene-Early Oligocene age (e.g., Nummulites atacicus, Nummulites mamillatus, Nummulites discorbina, Nummulites djodjokartae, Nummulites vascus, bioclast, Lockhartia pustulosa, gastropods, miliolids, brachiopods, Globigerinoides spp., crinoid, bivalves, and ostracods). The presence of fossiliferous limestone in the form of lenses revealed that they were deposited in the Neritic to Bathyal facies while the Kul-dana coarsened upward succession. The formation of the debris revealed that it was transported by the fluvial system and subsequently deposited in deltas. (3) During the initial phase of the collision between the Indian continental plate and the Asian plate, seawater fluctuations occurred. Multiple events of transgression and regression led to the redeposition of marine fossils in terrestrial sediments and the redeposition of detritus in the Ceno-Tethys Ocean, respectively. (4) During the Middle Eocene-Early Oligocene, detrital sediments from the Higher-Tethyan Himalayas were carried by large river systems into the deltaic environment of foreland basin. In the meanwhile, the same detritus was deposited in India and Nepal as shelf turbidites and tidal flat-deltaic systems. These deposits are designated as the Upper Subathu Group and the Upper Bhainskti Formation, respectively. A forebulge above these deposits caused a regional unconformity in the Himalayan foreland regions. This unconformity is also observable in Nepal, India, and the study region of Pakistan.