Multi-Proxy Provenance Analyses of the Kingriali and Datta Formations (Triassic–Jurassic Transition): Evidence for Westward Extension of the Neo-Tethys Passive Margin from the Salt Range (Pakistan)

: The Salt Range, in Pakistan, preserves an insightful sedimentary record of passive margin dynamics along the NW margin of the Indian Plate during the Mesozoic. This study develops provenance analyses of the Upper Triassic (Kingriali Formation) to Lower Jurassic (Datta Formation) siliciclastics from the Salt and Trans Indus ranges based on outcrop analysis, petrography, bulk sediment elemental geochemistry, and heavy-mineral data. The sandstones are texturally and com-positionally mature quartz arenites and the conglomerates are quartz rich oligomictic conglomerates. Geochemical proxies support sediment derivation from acidic sources and deposition under a passive margin setting. The transparent heavy mineral suite consists of zircon, tourmaline, and rutile (ZTR) with minor staurolite in the Triassic strata that diminishes in the Jurassic strata. Together, these data indicate that the sediments were supplied by erosion of the older siliciclastics of the eastern Salt Range and adjoining areas of the Indian Plate. The proportion of recycled component exceeds the previous literature estimates for direct sediment derivation from the Indian Shield. A possible increase in detritus supply from the Salt Range itself indicates notably different conditions of sediment generation, during the Triassic–Jurassic transition. The present results suggest that, during the Triassic–Jurassic transition in the Salt Range, direct sediment supply from the Indian Shield was probably reduced and the Triassic and older siliciclastics were exhumed on an elevated passive margin and reworked by a locally established ﬂuvio-deltaic system. The sediment transport had a north-northwestward trend parallel to the northwestern Tethyan margin of the Indian Plate and normal to its opening axis. During the Late Triassic, hot and arid hot-house palaeoclimate prevailed in the area that gave way to a hot and humid greenhouse palaeoclimate across the Triassic–Jurassic Boundary. Sedimentological similarity between the Salt Range succession and the Neo-Tethyan succession exposed to the east on the northern Indian passive Neo-Tethyan margin suggests a possible westward extension of this margin.


Episode Tethyan Himalaya Succession (THS) Salt Range Succession (SRS)
Syn-Collisional Paleogene limestones followed by post Eocene fluvio-deltaic red beds derived from erosion of the Himalayas Paleogene shallow marine limestones and shales followed by Post Eocene brown-red fluvio-deltaic siliciclastics derived from erosion of Himalayas Drift (g) Cretaceous drowning and deposition of glauconitic and phosphatic ironstones.

Geological Setting and Palaeogeography
The Salt Range, with its Trans Indus extension, is a nearly east-west trending mountain range located in Pakistan ( Figure 1). The SRS preserves thick Precambrian to recent sedimentary record e.g., [36,37,40,[46][47][48]. According to the literature, the SRS displays considerable similarity to the THS e.g., [16,19,23]. The SRS can be broadly subdivided into four supersequences similar to that of the THS (Table 1): (a) the Late Neoproterozoic-Cambrian sequence consists of evaporites of the Salt Range Formation and overlying siliciclastics of the Cambrian Jhelum Group that can be correlated with the pre-rift sequence of the THS; (b) the Lower Permian siliciclastics of the Tobra and Dandot formations of the Nilawahan Group, which are correlatable with the syn-rift sequence of the THS; (c) the middle Permian-Cretaceous sequence, which can be correlated with the drift sequence of the THS; and (d) the Paleocene-Eocene sequence, a probable stratigraphic equivalent of the syncollisional sequence of the THS. This succession of the SRS is capped by postcollisional siliciclastics of post Eocene age.
The SRS displays a major Ordovician-Carboniferous unconformity between the pr-rift and the syn-rift supersequences ( Figure 2 and Table 1). This points towards the possible occurrence of the Cambro-Ordovician orogeny in the Salt Range that is documented over large parts of Gondwana [49,50]. The Ordovician to Carboniferous strata is, however, well developed in the Peshawar Basin [38] located ca. 200 km to the north of the Salt Range.
The syn-rift sequence on the northwestern margin of the Indian Plate documents the tectonic processes that resulted in the continental break-up and Neo-Tethys opening. The drift sequence of the area preserves the sedimentation and subsidence history of the NW passive continental margin of the Indian Plate [51][52][53]. The sudden increase in siliciclastic detritus during the Late Triassic points to a possible passive-margin rejuvenation in the NW Greater India. Quartzose sandstones were deposited during this interval in THS and this deposition locally continued until the middle Early Jurassic [16]. The quartzose sandstones of the SRS around the TJB interval were possibly deposited during this passive margin rejuvenation phase. The Kingriali Formation consists of dolostones, limestones with green-black shales, and sandstones in the upper part. A Rhaetian age is confirmed by new palynology data [15]. The Datta Formation, of Hettangian age, consists of conglomerates, sandstones, shales, and carbonates.
Around 200 Ma ago, the Salt Range ( Figure 1) was located on the NW margin of the Indian Plate, close to the Arabian and Greater Somalian plates, in the tropical-near tropical region of the southern hemisphere in the Tethyan realm at ∼20 • -25 • S latitude [34,54,55]. The TJB interval witnessed a transition from hot and arid to hot and humid greenhouse palaeoclimate [56][57][58]. During this interval, a fluvio-deltaic system developed in the areas, nowadays the Salt Range-Kohat-Potwar Plateau, and deposited the siliciclastics of Kingriali and Datta formations on an area of ca. 15,000 km 2 [15,36].

Fieldwork and Sampling
In the Salt and Trans Indus ranges of Pakistan the upper part of the Kingriali Formation and the overlying entire Datta Formation were studied (Figure 1b,c). A total of six (6) stratigraphic sections were measured along a ca. 300 km transect from the western Salt Range through the Surghar Range, and the Khisor Range (Figures 2 and 3; Table 2).
Sedimentological analyses were conducted in the field (Figures 2-5). In total, 400 samples were collected from the entire facies' variation.

Palaeocurrent Analysis
Palaeocurrent data, mostly from trough cross bedding and where possible from the imbricated clasts and ripples, were collected. In total, 229 readings for palaeocurrents were collected in the field, including 209 from cross bedding and 20 from imbricated clasts and ripples. For each reading, measurements of the dip and azimuth of the structure and dip and strike of the beds were taken using a Brunton compass. The direction for each reading was recorded as a plunge with respect to the orientation of the bedding, and this direction was then rotated back to the depositional horizontal using stereonet techniques [59]. The data were restored to reconstruct the palaeoflow pathway and rose diagrams were prepared for each stratigraphic section ( Figure 5).

Petrographic Studies
Except for loose shale, thin sections were made for all siltstones, sandstones, conglomerates, carbonates, and evaporites samples. In total, 300 thin sections were made at the Department of Geology, University of Vienna. All thin sections were studied systematically using a Leica DM2700 P microscope with a Leica MC170 HD camera. Herein, the petrographic studies were focused on point counting of 500 grains per thin section (Supplementary Materials S1) and its application for provenance analysis. The petrographic detail of the carbonates present in the succession are avoided as these are not significant in provenance analysis. Similarly, the various types of cementation and diagenetic features add little to the provenance analysis and have been avoided.
For point counting, the total quartz (Q total ) was subdivided into monocrystalline (Q m ) and polycrystalline (Q p ) varieties. The latter also included chert. Q m was further classified into Q m with unit extinction (Q mue ) and Q m with undulose extinction (Q muu ). Similarly, Q p was subdivided into Q p with 2-3 crystals (Q pq (2)(3) ) and Q p with >3 crystals (Q pq>3 ). Total feldspars (F total ) were subdivided into plagioclase (P) and K-feldspar (A). The total lithic fragments (L total ) were subdivided into sedimentary (L s ), metamorphic (L m ), and volcanic-metavolcanic (L v ) lithics [60,61]. The data were plotted on Quartz-Feldspars-Lithic fragments (QFL) plots for sandstone classifications and tectonic setting discrimination [62].

Clay Mineralogy/XRD Separation
Thirty samples from the clays/shale horizons were selected and investigated for clay mineralogy. These include 10 samples from the Kingriali Formation and 20 samples from the Datta Formation. XRD separation analysis was conducted using a PANalytical X'Pert Pro diffractometer (CuKα-radiation (40 kV, 40 mA), step size 0.0167, 5 s per step) at the University of Vienna. Each sample was treated with 15% hydrogenperoxide (H 2 O 2 ) to remove the organic matter [63] and then dispersed with a 400 W ultrasonic probe. The <2 µm fraction of each sample was separated using Atterberg cylinders and dried in oven at a temperature <40 • C to avoid the destruction of kaolinite. Then, 1 mL suspension (10 mg/mL) of each sample was pipetted out onto a glass slide to prepare oriented clay samples. Each sample was saturated with Mg and K ions and the mounts were analysed. These samples were saturated with glycerol (Mg-samples) and ethylene-glycol (K-samples) to separate smectite and vermiculite. Every sample was heated to 550 • C [64] and analysed as kaolinite loses it structure at this temperature. The XRD patterns were interpreted [65] and quantified using the correction factors [66].

Bulk Geochemistry
In total, 150 samples were selected, including 40 samples from the Kingirali Formation and 110 samples from the Datta Formation, for bulk rock geochemical analysis based on field and petrographic studies. Each sample was powdered and homogenised and the analysis was conducted at Bureau Veritas, Canada using inductively coupled plasma optical emission spectroscopy/mass spectrometry (ICP-OES/MS). The analysis included major, minor oxides, trace, and rare earth elements (REEs) (Supplementary Materials S2).
For each sample, a split of 0.2 mg powdered and homogenised sample was fused in lithium metaborate/tetraborate followed by nitric acid digestion to extract Si, Nb, and Rb and measured by ICP-OES (Spectro Ciros Vision). Besides, 0.5 g of each sample was digested in 95 • C Aqua Regia and analysed for Al, Fe, Mg, Ca, Na, K, Ti, P, Mn, Cr, Ba, Co, Sr, Th, U, V, W, and Zr using ICP-MS (Perkin Elmer ELAN 9000, Sciex). Both splits were calibrated against reference materials SO18, DS 10, and OREAS 45 EA. Thirteen samples were analysed in duplicates. The average analytical error in the analysis is 0.18%.
The interpretation of geochemical data is based on widely used proxies to reconstruct weathering and palaeoclimatic trends including the Chemical Index of Alteration (CIA) [67,68], Al 2 O 3 -CaO*+Na 2 O-K 2 O (A-CN-K) plot, and Th/U versus Th plot [69]. In both the CIA and A-CN-K, all the quantities were used in molar proportions and the CaO* is the amount of CaO incorporated in the silicate fraction of the rock and correction for K-metasomatism was also made [70]. Th/Sc versus Zr/Sc plot [71] was used to understand the sediment recycling. Th/Co versus La/Sc plot [72] and V-Ni-Thx10 plot [73] were used for the identification of parent rocks composition. La/Th versus Hf plot [74]; Ti/Zr versus La/Sc, La-Th-Sc, Th-Sc-Zr/10, and Th-Co-Zr/10 plots [75]; and Nb/La versus (La/Sm)N plot have been used for discrimination of tectonic settings. These proxies are widely used for provenance analysis worldwide e.g., [76][77][78][79][80][81][82][83][84][85][86][87].

Heavy Minerals
Subsequent to detail petrography and geochemistry, 30 rock samples from the siltstones and sandstones of the succession (Supplementary Materials S3) were selected for heavy mineral analysis. Each sample was gently crushed to separate the constituent particles. A solution of 3:2 distilled water and 80% acetic acid was prepared to decalcify each sample. Each of the treated samples was sieved to separate the 0.4 mm to 63 µm fraction used for the heavy mineral separation e.g., [84]. Heavy minerals were separated by gravity settling in low-toxicity inorganic solutions, based on tungsten compounds lithium heteropolytungstates (LST) with a specific gravity of 2.90 g/cm 3 [88,89]. The grain concentrates containing the whole heavy mineral fraction were embedded in a Canada Balsam mount. Herein, heavy mineral data for the Kasanwala section are presented as this section preserves the complete lithofacies variations of the succession.

Field Data
A summary of the outcrop observations and facies distribution based on the present study is included in Table 3  The lower part of the Datta Formation consists of rounded, well-sorted, and quartzose conglomerates, as well as pebbly and coarse quartz rich sandstones (Figure 4a-e). The coarsest pebbles (average diameter = 5-7 cm) occur in the Kasanwala section ( Figure 4c); the Zaluch Nala section displays finer pebbles (average diameter = 2-3 cm). In the Surghar and Khisor ranges, conglomerates are not present. Upsection, red-brown colour fine to medium grained sandstones, siltstones, and light to dark brown shale occur throughout the study area. Brown-black calcareous shale and carbonates are limited to the western Salt Range and eastern parts of the Surghar Range.
The conglomerates, pebbly sandstones, sandstones, and siltstones possess abundant trough cross-beds and cross bed sets (Figure 4b,d,e). Laminated siltstone with erosive upper bedding plane and fining upward pebbly sandstones occur in the Datta Formation at Nammal Gorge ( Figure 4f). In the Kasanwala section, plant remains occur in the pebbly sandstones of the Datta Formation ( Figure 4g). In the Gulla Khel section, ripple-laminated fine-grained sandstones are common in the Datta Formation ( Figure 4h). Additionally, aligned pebbles with their longer axes parallel to the bedding plane and pebble's imbrication indicative of transport direction occur. All these palaeoflow indicators indicate a general southeast to northwest transport of the sediments ( Figure 5).

Framework Composition/Petrographic Studies
The Triassic sandstones are fine to medium grained and consist of poorly sorted angular to subrounded clasts (Figure 6a,b). Silica and iron oxide are the major cementing material, while carbonate cements are minor. The grains display a sharp margin with point and long linear contacts. Corroded grain margins and sutured contacts are rare (Figure 6a). The Jurassic sandstones are medium to very coarse grained and pebbly, are rounded to very well rounded, and are very well sorted (Figure 6c,d). A fining upward trend is observable in the sandstones (Figure 6e). Point and long linear contacts are common, and concavo-convex contacts are also observable, while suture contacts are rare (Figure 6f). Fine silt and clay size particles are present in the pore spaces of the coarse grained to pebbly sandstones. Iron oxide, calcite, dolomite/ferroan dolomite, and silica are the common cementing materials. Matrix is generally lacking, but where the grains are not in contact, they are floating in iron oxide, finely crystalline calcite, and dolomite (Figure 6c,d).
Fractures filled with brown colour iron oxide are crosscut by sparry calcite veins/fractures.
Point counting data indicate that quartz is the dominant framework component and Q total averages 98% in the Triassic strata (Figure 7a). L t is 1%, while the sum of F t and other framework components is 1%. Q total is a mixture of Q m (96%) and Q p (4%). Q m consists of Q mue (90%) and Q muu (6%), while Q p consists of Q pq(2-3) (3%) and Q pq>3 (1%) (Figure 7b). The Jurassic strata consist of 96% average Q total (Figure 7c). L t averages 2% of the total framework composition, while F t is less than 1% (Figure 7c). The Q total consists of 94% Q m , of which 81% is Q mue and 11% Q muu . Q p counts for 6% of Q total and is subdivided into 4% Q pq (2)(3) and 2% Q pq>3 (Figure 7d).
The average of the total point counting data indicates that Q total averaged 96% of the total framework composition. Q mue predominates, averaging 81%, followed by Q muu (10%), whereas Q pq(2-3) averages 3% and Q pq>3 averages 2%. Comparatively high Q muu and Q p contents occur in the conglomerates and pebbly sandstones. The F total accounts for only 0.13%, of which A averages 0.12%, while P is 0.01%. The L t averages 1.4% and is the combination of L s , L m , and L v . According to the Q t F t L t plot, >96% of the samples plot in the pure quartzose field (Figure 8a). Around 97% of the samples plot in the undissected part of the continental block provenance field (Figure 8b).

Clay Mineralogy
Analysis of the oriented clay samples displays a mixture of illite and kaolinite ( Figure 9). Illite is the dominant clay mineral in the Kingriali Formation that averages 94% of the total clay content, while the remaining 6% is kaolinite. By contrast, the overlying Datta Formation is rich in kaolinite, which averages 69% of the total clays, while the remaining 31% is all illite. Following the very high illite content during the Triassic (100% in the uppermost part of the Kingriali Formation), a jump to very high kaolinite content (92%) is observed in the basal part of the Datta Formation ( Figure 9). The present samples have Ti/Zr ratios of <35 and a broad La/Sc range of 1 to >14. Around 75% of samples from the Kingriali Formation occupy the andesitic arc source and active continental margin fields. While the Datta Formation show 50% samples population in these fields and the remaining 50% are positioned in the passive margin source field (Figure 10b).
The Nb/La versus (La/Sm)N plot indicates that all the samples have an Nb/La ratio of <1.4 (Figure 10c). Similarly, the (La/Sm)N values are >3 for most of the samples (>95%). More than 90% of the samples plot in the passive margin settings.
La-Th-Sc, Th-Sc-Zr/10, and Th-Co-Zr/10 Plots The results of the La/Th and La/Sc have already been included in the previous section.
The Th/Sc ratio shows an average of 1.6 for the Kingriali Formation that increases to 2.8 for the Datta Formation. On the La-Th-Sc plot (Figure 11a), around 60% of the samples from the Kingriali Formation plot in the continental island arc field and 25% in the active and passive margins combined field. Moreover, 40% of the samples from the Datta Formation occupy the continental island arc field and 40% plot in the combined active and passive margin field (Figure 11a).

Source Rock Composition Identification Plots
The Th/Sc versus Zr/Sc plot illustrates that >95% of the samples yield Th/Sc values above 1 (Figure 12c). Similarly, >95% of the samples show Zr/Sc values above 10. In general, the Datta Formation yielded higher Th/Sc and Zr/Sc values than the Kingriali Formation (Figure 12c).

Heavy Minerals Analysis
In the present case, the heavy mineral assemblage represents a simple mixture (Supplementary Materials S3) of ultra-stable zircon, tourmaline, and rutile with minor staurolite and rare chloritoid. In general, the Triassic heavy minerals are smaller in size; have well preserved crystal faces, sharp edges, and corners; and display less dissolution and corrosion effects. The Jurassic heavy minerals are comparatively bigger in size and display advanced stage corrosion and dissolution and are rounded and broken (Figures 13 and 14).  Tourmaline is the most abundant transparent heavy mineral that averages 44.3% of the heavy mineral assemblage. It averages 39.8% in the strata below the thick laterite (hereafter called the Triassic strata). In the strata above the thick laterite (hereafter called Jurassic strata), tourmaline averages 51.7% of the total assemblage. Zircon represents the second most abundant transparent heavy mineral and represents 32% of the Triassic heavy mineral population and 29.4% in the Jurassic strata ( Figure 14). Rutile constitutes the third most abundant transparent heavy mineral and averages 21.5% of the assemblage (23.9% in the Triassic and 17.7% in the Jurassic). Staurolite is the least abundant heavy mineral, averaging nearly 3%.
The only visible difference in heavy mineral assemblage is the higher concentration of staurolite in the Triassic strata (averaging 4.1%) that diminished to less than 1% in the Jurassic (Figure 14).

ZTR Index
The sum of total zircons, tourmalines, and rutiles (ZTR) is termed as the ZTR-Index [96]. The lowest ZTR-Index of 87 is measured for the basal unit of the Triassic strata that displays an increasing upsection trend and reaches 100 in the Jurassic strata ( Figure 14). The Triassic succession displays an average ZTR-Index of 95.7, while it reaches an average of 98.9 in the overlying Jurassic strata.

Tectonic Setting Using Heavy Minerals Plot
The present sediments lack any of the heavy minerals that can provide evidence for a basic igneous or metamorphic provenance; therefore, the ternary plot of the transport limited (TL) heavy minerals (zircon, tourmaline, rutile)-low grade metamorphic (LGM) heavy minerals (epidote, chloritoid, chlorite, actinolite)-high grade metamorphic (HGM) heavy minerals (sillimanite, staurolite, garnet, andalusite) becomes the ideal candidate for tectonic settings and palaeoclimatic discriminations [97]. Presently, all the samples are clustered near the TL apex of the plot ( Figure 15).  [97]. TL = transport limited; LGM = low grade metamorphic; HGM = high-grade metamorphic.

Sediments Transport Pathways
Restored palaeocurrents data, in combination with the sedimentological characteristics of the investigated strata, advocate for a fluvial system that transported sediments from the palaeo-south-southeast toward the palaeo-north-northwest. The bimodal palaeoflow suggests the interaction between the fluvial system and the beach/tides [98]. On the other hand, channel avulsion and switching of the meander lobs may also yield bimodal flow [99]. The western Salt Range occupied a comparatively proximal position to the source region, while the Surghar Range was most probably the depocenter of the fluvial-deltaic system. The Khirsor Range (at least the southwestern part) was on the distal side of the depocenter.

Quartz-Feldspars-Lithics (QFL) Plots
The pure quartzose nature of the sediments provides evidence for polycyclicity (Figures 7 and 8) and supports sediment derivation from a stable cratonic interior in a continental block provenance setting [99]. Presently, the concentration of samples in the continental block provenance field (Figure 8b) may negate sediment derivation from magmatic arc source or orogenic belt. Dissolution and differential removal of the liable minerals such as feldspar during weathering produced mature quartz arenite.

La/Th versus Hf(ppm) and Ti/Zr versus La/Sc and Nb/La versus (La/Sm)N Plots
Sediments with acidic arc provenance generally have low La/Th ratio and Hf content of about 3-7 ppm [74]. Progressive erosion of the plutonic roots and continental basement of ancient (meta)sedimentary rocks concentrate zircon and hence Hf content in such sediments. The present samples cluster roughly parallel to the Hf axis (Figure 10a). More than 95% of samples support derivation from the acidic arc and passive margin source areas with increasing recycling components. However, possible poor control on the oceanic island arc composition using this plot may question its application. The Ti/Zr versus La/Sc plot [75] addresses this issue.
The oceanic island arc-derived sediments have a higher Ti/Zr ratio (generally > 40) accompanied by a very low La/Sc ratio (<1). The continental island arc detritus displays a Ti/Zr ratio of 10-35 and their La/Sc ratios are 1-3. The active continental margin sediments have Ti/Zr values like the continental island arc, but are discriminated from the latter by their higher La/Sc ratio (3)(4)(5)(6). The passive margin siliciclastics have wide variation in their La/Sc ratio, and their low Ti/Zr ratio (generally < 10) discriminate them from sediments of other tectonic settings [75]. The present samples indicate sediment derivation under passive margin setting with a significant component from active continental margin and continental island arc settings (Figure 10b).
The REEs provide significant information in tracing sediment source [100][101][102][103]. Oceanic island arc sediments have a high Nb/La ratio and low (La/Sm)N values. The continental arc and passive margin sediments have opposite trends and are positioned parallel to the (La/Sm)N axis [91]. Among these, the passive margin sediments generally have high (La/Sm)N values. The present samples support passive margin settings (Figure 10c).

La-Th-Sc, Th-Sc-Zr/10, and Th-Co-Zr/10 Plots
The significance of La/Th and La/Sc values has already been discussed; therefore, repetition is avoided. The Th/Sc ratio is very low (average = 0.15 ± 0.08) for the oceanic island arc sediments and these will plot close to the Sc apex. The Th/Sc ratio averages 0.85 ± 0.13 for the continental island arc sediments and 2.59 ± 0.5 for the active continental margin sediments. Sediments derived from passive margin settings have an average Th/Sc ratio of 3.06 ± 0.8 [75].
The La-Th-Sc ternary plot negates oceanic arc-derived sedimentation (Figure 11a). However, with the increasing Th/Sc value, the average error increases. This limitation of the plot does not allow clear discrimination of active continental margin from passive margins. The Zr/Th ratio is helpful in such discriminations. Further, Co behaves concordantly with Sc. Therefore, the Th-Sc-Zr/10 and Th-Co-Zr/10 plots [75] are valuable tools for such discriminations.
The oceanic island arc sediments are depleted in Th, and thus have a high Zr/Th ratio (average = 48 ± 13.4) and yield high Th/Sc and Th/Co ratios. Therefore, such sediments plot close to Sc and Co apices. The Zr/Th ratio for the active continental margin sediments is 9.5 ± 0.7 and is accompanied by low Th/Sc and Th/Co ratios. Hence, such sediments plot in closest vicinity to the Th pole on both plots. The passive margin siliciclastics have a Zr/Th ratio of 19.1 ± 5.8 and their Zr enrichment forces such sediments to plot near the Zr pole. Sediments derived from continental island arc have a Zr/Th average of 21.5 ± 2.4 and on both diagrams occupy an in-between position.
In the present case, the Th-Sc-Zr/10 and Th-Co-Zr/10 plots (Figure 11b,c) support sedimentation of the Datta Formation mostly under passive margin condition. Samples from the Kingriali Formation support sedimentation in an active continental margin and continental island arc source scenario. This apparent difference in sample position is an interplay of the palaeoclimatic conditions. The hot and arid climate during the Rhaetian e.g., [15] probably did not allow the differential leaching of Co [104]; therefore, the Kingriali Formation samples plot away from the passive margin field. The concentration of Co in sediments under reducing conditions [105,106] strengthens this argument. High Zr values in the Datta Formation suggest zircon concentration due to weathering during the Hettangian as interpreted for this time interval in the area and globally e.g., [15]. On the contrary, the transition elements (Co, Ni, and V) are immobile during weathering, and are compatible in magmatic processes. Therefore, Co is highly concentrated in ultramafic and mafic source rocks than felsic rocks [107], and thus mirror the chemistry of their source rocks [108]. Presently, no sediment contribution from oceanic island arc setting is indicated; however, to verify this, the concentration of V and Ni provides valuable information.

Source Compositions Identification V-Ni-Th × 10 and Th/Co versus La/Sc Plots
Mafic source rocks are rich in V and Ni. Therefore, sediments derived from such sources will occupy position along the V-Ni side of the plot. Samples close to Ni-apex support ultramafic source derivation, whereas mafics are close to the V-apex. As felsic sources are rich in Th, such sediments plot close to Th-apex. Presently, the V-Ni-Th × 10 plot favours sediment derivation from a felsic source (Figure 11d).
The La/Sc versus Th/Co plot [72] provides good discrimination between the acidic and basic source rocks. Generally, Co and Sc are compatible with basic rocks, while La and Th display the opposite trend [73]. Therefore, basic rocks have low La/Sc and Th/Co values. As the felsic sources are rich in Th, sediments derived from these rocks have higher Th/Co ratios. Presently, the La/Sc versus Th/Co plot supports sediment derivation from the silicic composition (Figure 12a).

Clay Mineralogy
Illite is a common clay mineral in arid climates [109]. Dominance of Illite in the shales of the Kingriali Formation indicates semiarid to arid conditions of deposition during Triassic [110]. The 100% illitic mineralogy of the uppermost green shales of the Kingriali Formation may suggest arid and potentially cooler conditions established during volcanic winters at the start of the Triassic-Jurassic transition [6]. Kaolinite is generally a product of intense chemical weathering, and hence hot and humid climates e.g., [111]. Thus, the kaolinite rich shales of the Datta Formation (Figure 9) support strong chemical weathering during Jurassic. Diagenetic controls generally limit the paleoclimatic significance of clay minerals; however, the sharp change from illite rich clays (in Triassic strata) to kaolinite rich clays (in Jurassic strata) in a confirmable succession supports depositional controls on clay mineralogy [112,113].

CIA and A-CN-K Plots
CIA values may be the direct indication of the intensity of chemical weathering, which is a function of temperature and humidity of the prevailing palaeoclimate [67,68]. CIA values of <80 for the Kingriali Formation (Figure 12d) indicate weak chemical weather-ing, and thus semiarid to arid palaeoclimate, during the Late Triassic. High CIA values (>90) in the Datta Formation favour increased chemical weathering, and thus hot and humid palaeoclimate, during Jurassic. The kaolinite rich clay mineralogy and the presence of laterite/bauxite horizons in the Datta Formation support this palaeoclimatic interpretation [114].
The A-CN-K plot (Figure 12d) is useful in interpreting the weathering trend of sediments [115]. Presently, the sample population between A vertex and muscovite position parallel to the A-K side hints for a recycled origin of the sediments. The muscovite-illite position of samples favours semiarid to arid palaeoclimate for the Kingriali Formation. The cluster of samples close to A apex (kaolinite position) for the Datta Formation indicates increasing chemical maturity, a support of recycling under a hot/warm and humid palaeoclimate. Correlation between the CIA and A-CN-K plot [116] shows coherence between the two data sets (Figure 12d). A possible diagenetic input of carbonates and K-metasomatism may have overprinted the results of CIA and A-CN-K plot, but both of the related corrections have been applied [70].

Th/U versus Th(ppm) and Th/Zr versus Zr/Sc Plots
During weathering, the Th/U value rises above the upper crustal values of 3.5-4.0 [69,111,117]. Sediment weathering and recycling under oxidising conditions results in oxidation of U 4+ to U 6+ . The U 6+ is more soluble and is lost resulting in elevated Th/U ratio e.g., [78,118,119]. Therefore, the Datta Formation (Figure 12b) supports increasing intensity of chemical weathering across the TJB interval into the Hettangian. Low Th/U values in the Kingriali Formation indicate poor chemical weathering during the Rhaetian.
Zr is particularly enriched in zircons, while Sc generally preserves its provenance signature; therefore, the Zr/Sc ratio is a useful index of zircon enrichment [120]. The incompatibility of Th makes Th/Sc a good indicator of igneous chemical differentiation processes. Presently, the higher Zr/Sc and Th/Sc ratios indicate increasing weathering and sediment recycling from the Kingriali Formation to the Datta Formation (Figure 12c).

Heavy Minerals and Weathering and Tectonics
Heavy mineral analyses have a wide range of applications in studying the provenance of siliciclastic rocks e.g., [121]. Specific heavy minerals assemblages are a characteristic of specific source rocks and are sensitive indicators of provenance [122]. The dominance of ultra-stable heavy minerals (zircon, tourmaline, and rutile, i.e., high ZTR > 87) supports the differential removal of chemically unstable minerals under multi-cyclic weathering, erosion, and transportation. The presence of well-preserved crystals (Figure 13a,b) in the Triassic strata does not support rounding and thus long transportation. Their relatively small grain-sizes ( Figure 14) further hint for the absence of high energy transporting agent. The presence of sharp edges and lack of corroded margins and dissolution cavities may negate strong chemical weathering (Figure 13b). The presence of staurolite suggests derivation from a nearby metamorphic source.
The rounded to very well rounded heavy mineral assemblage of the Jurassic strata supports an efficient transport mechanism. This supports hydraulic sorting during fluvial transport under prolonged exposure of the low-relief source areas. The relatively coarsegrained nature of these minerals indicates high energy transporting agent. The corroded and etched grains indicate strong chemical weathering (Figure 13a).
The concentration of ultra-stable heavy mineral suites (ZTR) suggests extensive recycling with no contemporaneous volcanic activity. The corroded margins in the Jurassic heavy minerals could hint for dissolution and differential removal of the liable heavy minerals during diagenesis. However, the presence of well-preserved crystals in the Triassic strata does not favour deep burial diagenesis.
The cluster of samples along the TL apex ( Figure 15) indicates sediment derivation from a mature and recycled source such as passive margins, cratonic basins, and craton lowlands. Additionally, such mature quartz-rich sediments may indicate uplift and erosion of mature sedimentary rocks [97].

Palaeogeography and Possible Detritus Suppliers
The neo-Proterozoic (800 Ma to 600 Ma) marks the peak time of crust production during the Pan-African Orogeny prior to the assembly of Gondwana [123]. Geochronology of the Pan-African orogenic belts in the central-north Africa, Saudi Arabia, Kazakhstan, eastern Baltica, and Pakistan Block supports continental crust formation during this period. The final Gondwana assembly occurred at ca. 540 Ma and, by the late Cambrian (ca. 500 Ma), the orogeny had produced sufficient positive relief structures in Arabia, East Africa, as well in Pakistan that could have provided the long-term source for sedimentary basins [123].
The palaeogeographic position [90] of the study area (Figure 16a,b) puts the nearby Arabian Plate, Greater Somalian Plate (southeastern margin of northeastern Africa), and Indian Plate as the candidate sources of the siliciclastics. The Arabian-Nubian Shield in these areas formed during the Pan-African Orogeny, closure of Mozambique Ocean, and subsequent collision of east and west Gondwana at ca. 540 Ma [124]. The basement rocks of Arabian Peninsula include amphibolite facies gneissic terrains, diorites, tonalites, and granitoids, as well as granites with rhyolites, tuffs, lava breccias, quartzites, marbles, and mafic dykes [125]. Similar gneisses, basalts, tuffs, rhyolites, granites, quartzites, and marbles also occur in Somalia [126]. However, both the pinching out of the strata and decreasing grain size towards the west-northwest and south-southwest [40] negate siliciclastic supply from the Arabian and Greater Somalian plates. Further, the palaeoflow direction ( Figure 5) argues against sediment supply from these two sites and advocate for an easterly (present-day) source of the sediments. Thus, the Indian Plate most likely served as the principal source for the siliciclastics (Figures 16c and 17).

Correlation with Northern Indian Passive Tethyan Margin
The Salt Range (Kohat-Potwar Basin) represents a rim basin along the NW margin of India (Figure 16c) associated with the Neo-Tethys rift system [127]. It possibly opened into a rift that separated Arabia and India, which extended towards Madagascar [128] and connected southwards up with the Karoo system [129]. The rifting activity most likely commenced during the Late Carboniferous [16,19,42]. Evidence for various stages of the Neo-Tethys opening in SRS and their tentative correlation with the THS is provided in the Geological setting and palaeogeography chapter (Table 1) and an extended correlation between the syn-rift and drift sequences of the THS and the SRS is presented here.
The syn-rift sequence in the THS includes the Pennsylvanian to lowermost Permian glacigenic diamictites overlain by Sakmarian deglaciation mudrocks [130]. The glacigenic diamictites of the Tobra Formation e.g., [45] and the overlying deglaciation shale/mudrocks of the Dandot Formation with cold water Eurydesma fauna [40] of Gondwanan characters may be an indication of the westward extension of the synrift sequence in the SRS. A gentle angular unconformity (1-2 • ) exists between the Tobra Formation and the underlying Cambrian strata (Figure 2) in the Salt Range [131]. This correlates with the angular unconformity between Upper Devonian to Tournaisian limestones and the overlying rift sequence in the THS [132]. Furthermore, normal faults in the strata underlying the Tobra Formation are observed in the field and reported in the basement on seismic data e.g., [47] that provide additional evidence for rift-related tectonics in the Salt Range area like those observed in THS e.g., [133].
The "break-up unconformity" on top of the rift sequence observed in THS (Lahul-Zanskar) [21] is not truly reported in the SRS. However, the Dandot Formation (uppermost part of the syn-rift sequence) is missing in the western Salt Range and in the Khisor Range [40]. The basal part of the drift sequence in the Salt Range consists of Permian sands and shales (Warchha and Sardhai formations) overlain by limestones (Zaulch Group) and displays an overall transgressive trend like that observed in the Lahul-Zanskar area (THS) e.g., [21]. The presence of Lower Triassic ammonoid-rich sediments (Mianwali Formation) in the Salt Range e.g., [47] may indicate subsidence of the newly formed rift margin and correlates with the ammonoid-rich sediments of THS deposited in Lower Triassic [134,135]. Thick sandstones of the Tredian Formation succeed the Mianwali Formation [47]. This may provide evidence for the sudden increase in siliciclastic supply in the Salt Range during the Middle-Late Triassic like that observed in the THS [136]. Large-scale syndepositional slumps occur especially in the lower part of the Tredian Formation [47]. These slumps provide evidence for possible occurrence of tectonic activity in the Salt Range like passive margin rejuvenation observed in the THS. The present quartz-rich sediments of the Kingriali and Datta formations in the Salt Range during the Late Triassic to Early Jurassic [15] may correlate with the deposition of quartzose sands until the middle Early Jurassic in the THS [22]. In the Salt Range the platform carbonates of the Samana Suk Formation were deposited following the Datta Formation and reflect the mature passivemargin stage of the Neo-Tethys as observed by carbonate-platform sedimentation during the mature passive-margin stage in the THS [23].  [42]) with pre-rift, syn-rift, and drift sequences marked e.g., [16]. Location of cross section C-D (explained in Figure 17) is also given.
The break-up of Gondwana and formation of NW passive margin of the India began in Late Carboniferous, around 100 ma prior to the deposition of the sediments under study e.g., [137]. By the Late Triassic, passive margin setting had established in the area now the Salt Range. A possible faulting and tilting of strata during passive margin rejuvenation occurred during this time [16,136,138,139]. These complicated processes probably resulted in the post-break-up exhumation of the passive margin in the eastern Salt Range and adjoining areas e.g., [140,141]. The prominent sea-level fall observed at the TJB interval in the Salt Range and globally [9][10][11]15] may also have facilitated exposure in the eastern Salt Range. This passive margin exhumation and subsequent exposure of the Triassic and older strata in the Salt Range and further south-southeast in Greater India may have provided the main source for sediments that were transported north-northwestward by the newly established fluvial system during the Late Triassic-Early Jurassic ( Figure 17).

Possible Sediment Suppliers
The north-south trending, nearly 700 km long, Aravalli-Malani Range ( Figure 18) is a part of the foreland normal-sense high strain zones that were active in the Paleoproterozoic [142]. The range is located 600 km to the southeast of the Salt Range and was a positive topographic feature by Early Permian [43]. The Precambrian Aravalli Supergroup overlies the banded gneisses [143] and consists of granites, siliciclastics, carbonates, slates, and phyllites [144]. The Malani Suite consists of porphyritic rhyolites and granites [145]. The rhyolites have abundant pink orthoclase and some sanidine, oligoclase, quartz, and rare hornblende and magnetite. The pink coloured Malani Granite intruded the rhyolites and is composed of orthoclase, quartz, sodic plagioclase, biotite, hornblende, and less common occurrences of muscovite. Accessory minerals include tourmaline and fluorite.
The Lower Permian, glacial-periglacial Tobra Formation in the Salt Range contains lithoclasts of Aravalli-Malani origin [45]. Similarly, the same ranges shed detritus for the Permian Warchha Sandstone of the Salt Range. Further, the sedimentary clasts within the Warchha Sandstone are considered to have been the product of local recycling of the underlying Permian, Cambrian, and Precambrian strata in the Salt Range region itself [43].
The Salt Range contains thick Cambrian, Permian, and Triassic siliciclastics that could prove detritus suppliers if exposed to surficial weathering and denudation. These include the thick sandstones and shales of the Cambrian Khewra Sandstone (sandstones), Kussak Formation (sandstones and shale), and Baghanwala Formation (sandstones, shales). The Lower Permian Nilawahan Group in the area consists of thick conglomerates of Tobra Formation, shales of Dandot Formation, sandstones and shales of Warchha Sandstone, and shales of Sardhai formations. The shales and sandstones of Mianwali Formation and the thick sandstones of Tredian Formation constitute the Triassic siliciclastics in the Salt Range [40,43]. Exposure of these Triassic and older sediments of the Salt Range itself during the eastward exhumation of the passive margin may have provided siliciclastic detritus for the Triassic-Jurassic sediments of the western Salt Range and adjoining area. The tropical palaeogeographic position of the area favoured dissolution of the liable components, thereby producing highly mature quartz arenites [15]. The comparative low relief did not allow sediment derivation from diverse source rocks. The meandering fluvial system reworked and transported mostly the older Triassic and Permian siliciclastics (Figure 17a) [146]. This is confirmed by the eastward disappearance of the Triassic and Permian strata in the present-day eastern Salt Range ( Figure 2). A possible destruction of the unstable minerals during diagenesis may have further facilitated the formation of quartz arenites [147][148][149][150]. However, lack of evidence does not allow reliable understanding of the diagenetic history of the present sediments, while the recently published burial history of the area [131] does not indicate deep burial of the strata during Mesozoic.
The extreme wet greenhouse conditions interpreted for the Jurassic strata [15,57,58] could have easily removed unstable components, thereby forcing highly mature quartz arenites with very high ZTR-index and hiding evidence for sediment incorporation from the basement or other diverse sources. However, Cambrian and older strata are widely distributed throughout the Salt and Trans-Indus ranges ( Figure 17a) and reported in the subsurface in the Kohat-Potwar Plateau and Punjab platform [40], thereby indicating that the fluvial system was unable to cut into the Cambrian and older strata and the basement rocks were not exposed to reworking.

Conclusions
The Neo-Tethys opening produced passive margin settings on the north-northwestern margin of the Indian Plate. Tectonic activity during this passive margin formation produced elevated passive margin in the eastern Salt Range and area further to the east on the Indian Plate. A prominent sea-level fall and a possible passive margin rejuvenation in the area during the late Triassic resulted in the demise of the Rhaetian platform carbonates deposition and a fluvial system initiated during the TJB interval in the Salt and Trans-Indus ranges. During the following Hettangian, this system matured into a fluvio-deltaic system under wet greenhouse palaeoclimatic conditions and had a general south-southeast to north-northwest palaeoflow. The present analyses do not support direct sediment derivation from the Indian Plate basement rocks. Instead, the fluvial system reworked the older (Carboniferous-Permian-Triassic) strata in the present-day eastern Salt Range and adjoining western-northwestern part of the Indian Plate. These polycyclic sediments were deposited (as the upper part of the Kingriali Formation and the Datta Formation) in the western Salt Range and Trans-Indus ranges in a fluvio-deltaic depositional system in a Neo-Tethyan passive margin setting like that observed in the Tethyan Himalaya. Thus, the Triassic-Jurassic sediments of the Salt and Trans Indus ranges, Pakistan, provide evidence for westward extension of the Neo-Tethyan passive margin and possible occurrence of Tethyan Himalayan Succession in the Salt Range. Varietal studies and isotopic geochronology are suggested to be carried to further pinpoint the source rock for these sediments.
Supplementary Materials: The following are available online at https://www.mdpi.com/article/ 10.3390/min11060573/s1. Supplementary Materials S1. Point counting data for framework mineralogical composition of the selected samples. Q mue = monocrystalline quartz with unit extinction, Q muu = monocrystalline quartz with undulose extinction, Q pq = polycrystalline quartz including chert, Q total = total quartz, A = K-feldspar, P = plagioclase, F total = total feldspar, L v = volcanic and hypabyssal lithic, L m = metamorphic lithic, L s = sedimentary lithic excluding chert, L total = total lithic, M = phyllosilicates, D = heavy minerals, O = others/not recognizable. Supplementary Materials S2. Bulk rock geochemistry data for the selected samples. The concentration of major oxides/elements is provided in percentage (%), while trace element concentrations are listed in parts per million (ppm). Note that only those chemical species are included here that are used in the present study. Supplementary Materials S3. Point count data for heavy minerals of the selected samples.