1 Introduction

The chemical composition of terrigenous sedimentary rocks can be studied to understand the tectonic setting, weathering, source rock compositions, provenance and diagenesis (Nesbitt and Young 1982; Bhatia 1983; Roser and Korsch 1986; McLennan 1989; Condie 1993; Cullers 1995). Traditional petrographic analyses reveal the processes associated with provenance, environment of deposition and transportation of clastic materials (Dickinson and Suczek 1979; Ingersoll and Suczek 1979; Dickinson 1985). However, the framework grains of sandstone are liable to be modified under burial and compaction which can mislead the conclusions. Whereas, the precision of geochemical data enable researchers to understand in detail the information contained in clastic sedimentary rocks (McLennan et al. 1993; Kroonenberg 1994; Armstrong-Altrin et al. 2004). In addition, the distribution of major elements in sandstone provides more insight details on tectonic setting in terms of discrimination diagrams as long as the bulk chemical composition of a rock is not altered (Bhatia 1983; Roser and Korsch 1986; McLennan 1989; Nesbitt and Young 1989). Also, the trace and rare earth element (REE) composition of sandstone can reflect the provenance and tectonic settings of sedimentary basin due to their immobility during weathering and transportation processes and relatively short residence time in sea water (Holland 1978; McLennan et al. 1983; Armstrong-Altrin and Verma 2005; Verma and Armstrong-Altrin 2013).

Kachchh sedimentary basin is a peri-cratonic and paleo rift basin in the western margin of India, where the development of sediments during Jurassic period is well known (Biswas 1987). The east–west trending basin is southernmost end of Indus shelf, bordered on north by fossil rift of Thar and southern Indus basin and in south by Narmada rift (Zaigham and Mallick 2000; Biswas 2005). The well exposed outcrops of sedimentary rocks in Kachchh basin has received significant attention from several authors in all aspects of paleontological, structural, stratigraphical and hydrocarbon prospects for many decades (Waagen 1873; Biswas 1987; Biswas and Deshpande 1983; Krishna 1987; Bhawani Singh et al. 2008). However, many lithocolumns of this basin remained untouched in terms of geochemical study. The aim of this study is to integrate petrography, major, trace and REE results to assess: (1) the source rock identification and its implications for provenance, (2) to evaluate the weathering intensity and (3) to study the tectonic setting of the region.

2 Geological setting

Kachchh basin is situated in the state of Gujarat, western India in between the lat. 22 ∘30′–24 ∘30′N and long. 68 ∘–72 ∘E (figure 1). The basin was formed as a consequence of the break-up of eastern part of the western Gondwanaland during late Triassic/Early Jurassic period (Norton and Sclater 1979). It is bounded by Nagar Parkar Fault (NPF) block and North Kathiawar Fault (NKF) block on northern and southern rifts, respectively. The rift basin contains several intra-basinal strike faults trending in east–west direction, resulted in a series of half-grabens. The main strike faults in the basin, such as the Island Belt Fault (IBF), the Banni Fault (BF), the Kachchh Mainland Fault (KMF), the Katrol Hill Fault (KHF) and South Wagad Fault (SWF) have the uplifted footwalls exposed as excellent outcrop areas and half-grabens to form as an extensive plain covered by recent sediments (Biswas 2005). The unique feature of this rift basin is the occurrence of the first order meridional (NNE–SSW) high across the middle of the basin (Biswas 1987).

Figure 1
figure 1

Generalised geological map of the Kachchh basin, western India (modified after Wynne 1872) showing the study area in red box.

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The basin consists of 2000–3000-m thick Mesozoic sediments ranging in age from Middle Jurassic to Lower Cretaceous, 600 m of Tertiary sediments and thin sheet of Quaternary sediments deposited in different rift stages of the basin. The major outcrop areas occurred in several uplifted regions of the basin such as Kachchh Mainland, Pachham Island, Khadir Island, Bela Island, Chorar Island and Wagad uplifts (figure 1), which are separated by vast plains of the Great and Little Ranns and Banni plains occupied by alluvial sediments and salt pan (Biswas 1977).

The lithostratigraphy of the Kachchh basin is chiefly controlled by fault-bounded regions; however, the development of rock sequences from middle Jurassic to lower Cretaceous is well preserved in Kachchh Mainland. The stratigraphic succession of Kachchh Mainland is divided into four formations named as Jhurio (Bathonian–Callovian), Jumara (Callovian–Oxfordian), Jhuran (Kimmeridgian–Lower Cretaceous) and Bhuj (pre-Aptian–Santonian(?)) formations in ascending stratigraphic order (Biswas 1977), which are best exposed in a series of domes at Habo, Jhura, Keera, Nara, Jumara and Jara hills (figure 1). The lithological sequence of these formations consists of clastic sandstone, siltstone, shale and limestone with distinct demarcation boundary, deposited in marine to fluvio-deltaic conditions. The present study was focussed on the Jhuran Formation of Upper Jurassic period (Kimmeridgian–Tithonian) in and around Jara dome since the greatest thickness of the sediments is preserved and exposed here.

Jara dome is located in western fringe of the Mainland Kachchh where the Jumara, Jhuran and Bhuj formations are best exposed (figure 1). The stratigraphic sequence of the Jhuran Formation in Jara dome contains alternating beds of sandstone and shale (figure 2) deposited from Kimmeridgian to Tithonian period overlies the Jumara formation (Biswas 1977; Kanjilal and Prasad 1992). The sequences of the Jhuran Formation commence with Rudramata shale, Katasar member followed by Upper member are well exposed around Jara dome and Lakhapar section (Biswas 1977). The lower boundary of the formation is demarcated by Dhosa Oolite bed of the Jumara Formation and the upper by distinct lithological variation. The studied section is located around lat. 23∘43′96″N and long. 68 ∘56′17 ″E composed of ∼500-m thick sediments belonging to lower and middle members of the Jhuran Formation. The lithology of lower member beds consists of repetitive siliceous and thin calcareous sandstones with shale interbedded and the middle member is characterized by alternations of dark grey to light grey shales and calcareous, flaggy, whitish to yellowish siltstone bands.

Figure 2
figure 2

Lithostratigraphic column of the Jhuran Formation, Jara dome showing the sampling locations in numbers.

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3 Materials and methods

A total of 50 samples were collected from the outcrops of lower and middle members of the Jhuran Formation from Jara dome of western Kachchh basin (figure 2). We prepared 25 thin sections representing entire ∼500-m thick litho column and all were subjected to detailed petrographic analysis with optical microscopy. Four hundred points were counted on 20 clastic sandstone samples using conventional point counting method following the method given by Dickinson and Suczek (1979) and Dickinson et al. (1983). The XRD analyses were performed on arkose, sub-litharenite, wacke and quartz arenite samples using Bruker D-8 Advance power XRD available at CSIR-Indian Institute of Chemical Technology, Hyderabad.

Major oxide concentrations were determined using X-ray fluorescence (XRF) spectrometry. For this experiment, 30 fresh sandstone rock samples were selected and washed thoroughly with distilled water. Samples were powdered individually on agate mortar to prevent from contamination and made pellets using backing of boric acid in collapsible aluminum cups and pressing at 20 tons of pressure by hydraulic press. A Philips MagiX PRO Model PW 2440 X-ray fluorescence spectrometer coupled with an automatic sample changer PW 2540 available at CSIR-National Geophysical Research Institute (NGRI), India was used to determine the major oxides in the sandstone samples. The standard GSR4 was used for calibration and to check the accuracy of XRF instrument for major oxide analysis. The precision of the chemical analysis is better than 10% which is observed from replicate analysis of samples and standard. Loss on ignition (LOI) was determined by weighing 1 g of dried samples before and after heating at 1000 ∘C for 1.5 hrs.

Trace-element and REE geochemistry analysis were performed for 20 representative samples by inductively coupled plasma mass spectrometer (ICP-MS) available at CSIR-NGRI, India. The sample solutions were prepared following the in-house standard method developed by Parijat Roy et al. (2007). A Perkin Elmer SCIEX, Model ELAN®; DRC II ICP-mass spectrometer (Toronto, ON, Canada) was used in this study, the instrument was calibrated with the standard GSR4. The analytical precision for trace elements and REEs is generally better than 5%.

4 Results

4.1 Sandstone petrography

The petrographic analysis revealed that the sandstones from the Jhuran Formation are characterized by fine-to-coarse grained sandstone with fair amount of matrix. Point counting study was performed on 20 representative thin sections from the studied area (table 1). The microphotographs of sandstones of the Jhuran Formation, Jara dome are shown in figure 3. The framework grains of Jhuran sandstones are made of monocrystalline quartz

Table 1 Modal analysis data (in %) for Jhuran Formation from Jara dome, Kachchh basin.
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Figure 3
figure 3

Microphotographs of sandstones from the Jhuran Formation. (a) Arkosic sandstone with subrounded monocrystalline quartz (Qm), K-felspar (Kf), plagioclase (Pl) and chert (Ch) minerals cemented by carbonate matrix. (b) Arkose sandstone contains largely of monocrystalline quartz (Qm), chert (Ch) and carbonate cement. (c) Wacke sandstone shows fresh K-felspar (Kf) and fine grained monocrystalline quartz (Qm). (d) Quartz arenite with monocrystalline quartz (Qm), polycrystalline quartz (Qp), undulose quartz (Qu), K-felspar (Kf) and iron cement. (e) Quartz arenite shows subrounded monocrystalline quartz (Qm) and fresh K-felspar (Kf). (f) Quartz arenite with large size grains of monocrystalline quartz (Qm) shows mechanical fracture.

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(Qn), polycrystalline quartz (Qp), undulatory monocrystalline quartz (Qu), K-feldspar, plagioclase and lithic fragments. Quartz is subrounded to subangular with mechanical fractures and on an average, monocrystalline quartz (87%) dominates over polycrystalline quartz (1.62%) (figure 3a). Subrounded-to-subangular feldspars (both plagioclase and K-feldspar) are present in considerable amount, but K-felspar especially microcline (4.5%) is higher (figure 3a). K-feldspars in Jhuran sandstones are fresh with cross-hatched twinning (microcline) and the plagioclase shows polysynthetic twinning. On an average, lithic fragments in the samples comprise of 2.7% of the modal percentage. Among the lithic fragments, sedimentary lithics especially chert are common (figure 3a, b). The sandstones of the Jhuran Formation are cemented with both calcareous and ferruginous matrices with the amount varying from 2 to 15% (figure 3c, d and e). The quartz grains vary in size largely and show mechanical fractures due to compaction (figure 3f). The average modal percentage of quartz, feldspar and lithic fragments from all the studied samples are 89, 7, and 4%, respectively. The XRD result shows that the d spacing \(\acute {\mathrm {\AA }}\) equivalent values of zircons apart from quartz, orthoclase, microcline, ilmenite and few clay minerals.

5 Geochemistry

5.1 Major elements

The major oxide concentration of the Jhuran Formation from Jara dome is presented in table 2. The sandstones from the Jhuran Formation are classified into arkose, sub-litharenite, wacke and quartz arenite based on geochemical characteristics after Herron (1988). Figure 4 shows the geochemical classification of sandstone samples from the Jhuran Formation. The sandstones of all types from the Jhuran Formation shows relatively high SiO2 content with minor variation among arkose (72%), sub-litharenite (74%) and wacke (65%), while slight enrichment of SiO2 (wt%) in quartz arenite (78 wt%) is observed as a consequence of higher quantity of quartz. Except quartz arenite all other sandstone types show related Al2O3 (5.11%) content, the depletion of Al2O3 in quartz arenite (0.6%) can be attributed to the larger amount of detrital quartz grains in this sandstone which is consistent with petrographic evidence. The Na2O concentration in arkose is 0.26–0.62%, sub-litharenite (0.04–0.42%), wacke (0.10–0.42%) and quartz arenite (0.01–0.05%). Sandstones show depleted nature. All sandstone samples from the Jhuran Formation are enriched with K2O content in arkose (2.42–3.25 wt%), sub-litharenite (1.77–2.24 wt%), wacke (3.41–4.31 wt%) and quartz arenite (0.09–1.58 wt%) proves the dominance of K-rich feldspar in their mineral composition. However, slight depletion is observed in quartz arenite, which is consistent with petrographic analysis. In addition, the ratio of K2O/Na2O for all sandstone types is 27.25%, which is > 1, strongly support the dominance of K-rich feldspar content. The average concentrations of MgOand MnO among all sandstones are 3.41 and 0.1%, respectively (table 2).

Table 2 Major element concentrations (in wt.%) of sandstones from the Jhuran Formation, Jara Dome.
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Figure 4
figure 4

Geochemical classification diagram of sandstone samples from the Jhuran Formation based on log(SiO2/Al2O3)–log(Fe2O3/K2O) (after Herron 1988).

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Figure 5 is the Harker variation diagram of Al2O3 vs. selected major oxides of sandstones from the Jhuran Formation. In Harker diagram, Al2O3 against SiO2 demonstrates negative and positive correlations with Na2O, K2O, TiO2 and MgOindicates the mineral maturity in studied rocks (figure 6). All sandstone types from the Jhuran Formation are normalized to UCC (Taylor and McLennan 1985) and shown in figure 6(a). The plotted major oxides show flat trend to UCC except Al2O3 and Na2O, which show moderate to strong depletions especially in quartz arenite samples (figure 6a). The enrichment of MgOcan be attributed to the association with phyllosilicates input, whereas depletion of Al2O3 and Na2O can be associated with nonphyllosilicate in the sediments. All the samples have relatively high LOI caused by elevated concentration of CaO in the studied samples.

Figure 5
figure 5

Harker variation diagram of Al2O3 vs. selected major oxides of sandstones from the Jhuran Formation.

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Figure 6
figure 6

Plot of upper continental crust pattern for (a) major oxides, (b) trace elements and (c) chondrite-normalized average REE from Jhuran Formation. The values of Taylor and McLennan (1985) were used for UCC and chondrite normalization.

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5.2 Trace elements

Trace element concentrations of sandstone samples from the Jhuran Formation are analysed and presented in table 3. The distribution of trace elements in all the analyzed sandstone samples display relatively similar pattern normalized to UCC with depletion and enrichment of certain elements (figure 6b). The large-ion lithophile elements (LILE) such as Rb, Sr, Cs, Ba, Th, and U are compared with UCC in which the Rb (16.7–86.8 ppm, n = 20), Sr (44.6–222 ppm, n = 20) and Cs (0.27–2.6 ppm, n = 20) are slightly depleted in all sandstone types with minor enrichment of Th (1.83–66.6 ppm) and U (0.64–5.21 ppm) in wacke sandstone (figure 6b). The Ba (180–896 ppm) and Cs (0.27–2.6 ppm) concentrations in the Jhuran sandstones are lower than in UCC, while wacke sandstone slightly enriched with Ba. The ratios of Rb/Sr and Th/U in analyzed samples ranging from 0.16–0.58 and 0.94–12.78, respectively (table 3). All the LILE, i.e., Rb, Sr, Cs, Ba, Th and U are showing high positive correlation coefficient (r = 0.98, 0.59, 0.86, 0.96, 0.47 and 0.55, respectively) with Al2O3 which implies that their distributions in the Jhuran sandstones is predominantly controlled by phyllosilicates (suggested by McLennan et al. 1983).

Table 3 Trace elements concentrations (in ppm) of Jhuran sandstones from Jara dome.
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The concentrations of Zr, Hf, Y and Nb (high-field strength elements, HFSE) are relatively similar to those of UCC. Among HFSE, Zr (avg. = 407 ppm) and Hf (avg. = 723 ppm) are enriched in arkose, sub-litharenite and wacke sandstones, respectively and depleted in quartz arenite (figure 6b) due to their strong affinity with fine-grained sediments (mostly clays) by grain size fractionation process. All the samples show low Nb (1.4–15.5 ppm) content than in UCC. Overall ratio of Zr/Hf ranges from 16.7 to 34.3 (table 3), which suggests the presence of heavy minerals in the studied samples. The correlation coefficient of Zr with Hf is 0.99, which is matching with the value obtained by Murali et al. (1983) suggests that these elements are primarily controlled by zircon.

The distribution of transition trace elements (TTE) Cr, Ni, Sc, Cu, and V in Jhuran sandstones show slight depletion as comparable to UCC (figure 6b), which can be attributed to low basic rock in the source area. In TTE, the Sc (1.5–8.4 ppm) content is lower in all sandstones, whereas other elements are similar to those in UCC. The Cr concentration in the samples varies from 13.3 to 46.3 ppm and show strong positive correlation coefficient with Al2O3 (r = 0.85, n = 20) implies to be incorporated into clay minerals. In addition, Ni (r = 0.63), Sc (r = 0.89), Cu (r = 0.69) and V (r = 0.55) show significant positive correlation with Al2O3 due to their association with phyllosilicates. The enrichment of Ni in the studied samples is an indicator of slight mafic contribution in the source rock.

5.3 Rare earth elements

The determined REE contents in the Jhuran sandstones are given in table 4. The detection limit for the REE concentrations were also given in table 4 (Armstrong-Altrin et al. 2015). The chondrite-normalized values display relatively similar to UCC pattern (figure 6c) with slight enrichment and depletion. The average ΣREE concentrations of all sandstones from the Jhuran Formation are slightly higher than UCC values. Considering individual sandstones, the total REE in arkose (140 ppm, n = 5), sub-litharenite (115.6 ppm, n = 7) and quartz arenite (90.8 ppm, n = 4) are comparatively lower than UCC values and higher in wacke (307 ppm, n = 4). The enrichment of ΣREE in wacke and depletion in quartz arenite reflects their grain size influence and amount of clay contents. The values of ΣREE, heavy REE (HREE) and light REE (LREE) are separately correlated with Al2O3, which show significant positive correlation 0.50, 0.48 and 0.7 (n = 20) suggest that phyllosilicates are important in these samples in hosting REE.

Table 4 Rare earth element (in ppm) data for sandstones from the Jhuran Formation.
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The average ratio of ΣLREE/ ΣHREE in the studied samples is 12.38. The chondrite-normalized (LREE) pattern in figure 6(c) demonstrates their higher enrichment (143.5 ppm) in Jhuran sandstones than in UCC, relatively flat HREE profile (11.4 ppm) and negative Eu (Eu/Eu ∗ = 0.66 ppm) anomaly. Although, significant variations in the concentration of ΣREE among the Jhuran sandstones are observed, but there is no overall difference in Eu anomaly is noticed. The ratios of Gd N/Yb N of arkose, sub-litharenite, wacke and quartz arenite are < 2 (0.8–3.04), which is suggestive of post-Archean source rock; however, few samples of wacke and sub-litharenite falls in Archean field (figure 15).

6 Discussion

6.1 Palaeoweathering pattern

Major element geochemistry and mineralogy of siliciclastic sedimentary rocks is greatly influenced by the intensity of chemical weathering at the source region, physical sorting and diagenesis (Nesbitt and Young 1982; McLennan 1993). Generally, feldspar is the more reactive mineral in the upper crust during chemical weathering and diagenesis, which results in the formation of clay minerals (Nesbitt and Young 1984; Taylor and McLennan 1985). The chemical weathering in the Jhuran sandstones were quantified using chemical index of alternation (CIA) (Nesbitt and Young 1982), which is widely used paleoweathering index by formula

$$\begin{array}{@{}rcl@{}} \text{CIA} \!\!\!\!\!&=&\!\!\!\!\! \frac{\text{Al}_{2}\text{O}_{3}}{(\text{Al}_{2}\text{O}_{3}+ \text{CaO}^{{\ast} } + \text{Na}_{2}\text{O} + \text{K}_{2}\text{O})\times 100}. \end{array} $$

The above equation is calculated using molar proportion ratio of respective elements, where CaO∗ represents the quantity of CaO incorporated in silicates/non-carbonate minerals only. The CaO in the Jhuran sandstone samples varies from 0.36 to 14.12 (wt%). The higher concentration of CaO in the studied samples were corrected using the method developed by McLennan (1993) to discriminate the content of CaO in silicate fraction (CaO∗) and non-silicate fraction. Higher concentration of CaO can be attributed to the presence of rich calcite cement and dolomitic matrix. For each sandstone type, the average calculated CIA values varies from 58.3–65.7% (arkose), 46.6–57.6% (sub-litharenite), 64.5–71.7% (wacke) and 15.6–36.8% (quartz arenite). Overall the calculated CIA values range from 15.6 to 71.7% for the Jhuran Formation sandstones. In general, the CIA value of typical unweathered granite to granodiorite rock is below 50, while feldspar, mica, illite and kaolinite minerals have 75, 75–85, 100, respectively (Nesbitt and Young 1982). Higher CIA values (> 70) suggest intense chemical weathering (Armstrong-Altrin et al. 2013, 2014; Deepthi et al. 2013; Sun et al. 2013).

The CIA values of arkose, sub-litharenite and wacke imply low to moderate intensity of chemical weathering at the source area, whereas quartz arenite (< 50) has CIA value lower than upper continental crust. Thus the low range of CIA value in these sandstones may not be very effective to characterize the original paleoweathering condition at the source area. The compositional changes associated with paleoweathering and source rock composition of the Jhuran sandstones are evaluated by plotting the CIA data on A–CN–K (Al2O3–(CaO* + Na2O)–K2O) triangular diagram after Nesbitt and Young (1984), where CaO* depicts Ca in silicate fractions only. All the sandstone samples plotted in A–CN–K ternary diagram (figure 7) show deviation from general weathering trend parallel to A–CN edge except wacke sandstone. The grouping of wacke and arkose samples close to illite composition indicates moderate to intense weathering condition at source area and consistent with predicted path. Whereas the sub-litharenite plot near to muscovite point and quartz arenite sample plot along A–K join due to depletion of Al2O3 and Na2O. The depletion of these elements resulted in low CIA values in quartz arenite, which gives little clue about paleoweathering condition of quartz arenite. The more smooth and elevated values of CIA indicate the stable tectonic settings and steady-state weathering trend. Whereas active tectonism results wide range of CIA values in the sediments due to erosion of all zones of weathering profile by rapid upliftment (Nesbitt et al. 1997; Selvaraj and Chen 2006; Armstrong-Altrin 2009). The wide range of CIA value in the Jhuran sandstone samples probably indicate that the sediments originated from non-steady state weathering through active tectonism. In addition, the ratio of Th/U can also indicate the source rock weathering pattern since U is generally removed during intense weathering (McLennan et al. 1993). The average Th/U ratio in the arkose, sub-litharenite, wacke and quartz arenite samples are 6.7, 5.0, 6.8 and 3.1, respectively (table 3), which are suggestive of moderate to intense weathering in the source region except for quartz arenite.

Figure 7
figure 7

A–CN–K ternary diagram (after Nesbitt and Young 1982) for sandstones of the Jhuran Formation (A = Al2O3, CN = CaO∗ + Na2O, K = K2O). CaO∗ depicts CaO incorporated in silicate fraction. UCC values (Taylor and McLennan 1985).

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6.2 Sediment sorting and recycling

Clastic sediments undergo hydraulic/mechanical sorting during transportation which significantly influences the bulk chemical composition of the resultant rocks by enriching certain minerals due to fractionation (Cullers et al. 1979; McLennan 1989; Bauluz et al. 2000; Armstrong-Altrin 2009; Singh 2009; Wu et al. 2013). Index of compositional variability [(Fe2O3 + K 2O + Na2O + CaO + MgO+ MnO + TiO2)/Al2O3, ICV] is used to study the geochemical variability due to hydraulic sorting (Cox et al. 1995). Generally, ICV values > 0.84 show the presence of rock forming minerals, while < 0.84 is characteristic of altered products, viz., clay minerals (Cox et al. 1995; Cullers 2000; Armstrong-Altrin et al. 2014). The ICV value of arkose (2.00–2.94), sublitharenite (5.61–8.80), wacke (1.99–2.87) and quartz arenite (> 25) in the studied samples are > 0.84 (table 2), which suggests the enrichment of primary minerals. In addition, ICV > 1 is suggestive of first cycle of sediments, which is well reflected in arkose, sub-litharenite and wacke samples. Also, SiO2/Al2O3 ratio is calculated to know the textural maturity of sediments, higher SiO2/Al2O3 values indicate maturity of sediments (Ahmad and Chandra 2013; Armstrong-Altrin et al. 2014). The SiO2/Al2O3 ratio of arkose and wacke samples varies between 6.80–13.01 and 5.05–6.82, respectively, while they are 19.70–31.59 and > 103 in sublitharenite and quartz arenite, respectively, infer that these sediments are highly matured than arkose and wacke.

The ΣREE concentration in Jhuran sandstones, i.e., arkose (139.9, n = 5), sub-litharenite (115.6, n = 7), wacke (307, n = 4) and quartz arenite (90.9, n = 4) varies considerably in spite of its immobility during weathering and transportation. None of the sandstone types of the Jhuran Formation show equivalent amount of total REE normalized to UCC and PAAS because of their grain-size variability and heavy mineral concentration (Condie et al. 1995; Cullers et al. 1997).

Also, the concentration of high weathering resistant phases (like zircon) in the samples can reflect the sorting and recycling processes involved (Armstrong-Altrin et al. 2012). Figure 8 shows that Th/Sc is plotted against Zr/Sc to depict the enrichment of Zr in the studied samples. In general, Zr/Sc ratio increases by addition of zircon mineral during sorting and/or recycling processes (McLennan et al. 1993; Armstrong-Altrin et al. 2012). The Jhuran sandstone samples fall in the trend 2 with enrichment of zircon indicates the significant influence of sorting and recycling of sediments. It is further supported by the positive correlation of Zr against Th (r = 0.75, n = 20) and Zr against total REE (r = 0.8, n = 20). Hence, it can be interpreted that both grain-size fraction and heavy mineral (zircon) content are responsible for difference in contents of total REE in the Jhuran sandstone samples.

Figure 8
figure 8

Binary scatter diagram of Zr/Sc against Th/Sc (McLennan et al. 1993) showing single trend for the Jhuran sandstones. The trend represents the sediments of the Jhuran Formation significantly affected by sediment sorting and recycling.

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XRD data of zircon peaks in the analysed samples are shown in table 5. Figure 9 shows the XRD patterns of arkose, sub-litharenite, wacke and quartz arenite samples. The distribution of zircon in arkose is comparatively higher than that observed in quartz arenite and wacke. They are detrital in nature, allogenic and are derived from a granitic source. The availability of zircon population in these samples shows their resistance to transportation and weathering, hence indicating their proximity to the source of formation.

Table 5 XRD data of zircon peaks in the analyzed rock samples.
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Figure 9
figure 9

X-ray diffraction patterns of the Jhuran sandstone samples.

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6.3 Tectonic setting

The petrographic study reveals that the studied sediments are characterized with higher proportions of monocrystalline quartz, smaller amount of polycrystalline quartz, more K-feldspar than plagioclase and a minor amount of rock fragments. Many authors have successfully established the tectonic environment by the proportions of frame work grains (Crook 1974; Schwab 1975; Potter 1975, 1986; Dickinson and Suczek 1979; Dickinson et al. 1983; Taylor and McLennan 1985). On the Qt–F–L diagram of Dickinson and Suczek (1979), the samples of the Jhuran Formation fall within the craton interior margin as shown in figure 10. The frame work grain properties (like quartz and feldspar) of studied formations are consistent with those of sediments deposited in a craton interior margin. Sandstones that fall within the passive continental block are chiefly derived from exposed shield areas and platforms or from uplifted areas.

Figure 10
figure 10

Tectonic setting discrimination diagram for the Jhuran sandstones based on Q–F–Lt (Dickinson and Suczek 1979).

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Tectonic setting discrimination diagrams using SiO2 content and K2O/Na2O ratios proposed by Bhatia (1983) and Roser and Korsch (1986) for sedimentary rocks is used to identify the tectonic setting of unknown basins that are still extensively used by many authors thus, shows consistency with the modal analysis (Drobe et al. 2009; Gabo et al. 2009; Bhushan and Sahoo 2010; Maslov et al. 2010; Wani and Mondal 2010). The Jhuran sediments plot within the passive continental margin (figure 11), which represents quartz-rich sediments derived from adjacent continental stable or rifted margin.

Figure 11
figure 11

Tectonic discrimination diagram of SiO2 vs. K2O/Na2O after Bhatia (1983) and Roser and Korsch (1986), where in three fields are passive margin, active continental margin and arc settings.

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Bhatia and Crook (1986) proposed various plots using certain immobile trace elements (for example, La, Th, Y, Sc, Cr and Zr) to discriminate the provenance and tectonic settings of clastic sediments and later successfully used by recent authors (Sun et al. 2012; Yang et al. 2012; Jorge et al. 2013). The bivariate plot of Sc/Cr vs. La/Y (figure 12) indicates that Jhuran sandstone samples were deposited in passive continental margin settings since most of the samples fall within the passive field and some are scattered, which is consistent with the plots based on the framework grains (figure 10) and major elements (figure 11).

Figure 12
figure 12

Plot of the trace element compositions for Jhuran sandstones represents Sc/Cr vs. La/Y (after Bhatia and Crook 1986). A, B, C and D are oceanic island arc, continental island arc, active continental margin and passive continental margin settings, respectively.

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6.4 Source rock and provenance

To identify the source rock composition using discrimination diagram of Roser and Korsch (1988) (figure 13), wherein all the samples of the Jhuran sandstone fall within the quartzose sedimentary provenance imply that they were derived from quartz rich or recycled sources. However, angular to sub-angular grains of quartz arenite (figure 3e) suggests that the sediments are texturally immature and indicate first cycle sediments transported to a shorter distance. This statement is confirmed by petrographic analysis.

Figure 13
figure 13

Provenance discrimination diagram for sandstones of the Jhuran Formation (after Roser and Korsch 1988). Discriminate function 1 = (−1.773 × TiO2%) + (0.607 × Al2O3%) + (0.76 × Fe2O3%) (−1.5 × MgO%) + (0.616 × CaO%) + (0.509 × Na2O%) + (−1.22 × K2O%) + (−9.09). Discriminate function 2 = (0.445 × TiO2%) + (0.07 × Al2O3%) + (0.25 × Fe2O3%) + (1.142 × MgO%) + (0.432 × Na2O%) + (1.426 × K2O%) + (−6.861).

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The bivariate plot of La/Sc vs. Th/Co (Cullers 2002) (figure 14) support the silicic source rock composition. REEs are most widely used as an indicator of the source rock composition because they are virtually insoluble and immobile during sedimentary processes and preserve the signature of the source rock (Taylor and McLennan 1985; Cullers 1995; Armstrong-Altrin et al. 2014, 2015). Generally, low LREE/HREE ratios and small/ absence of Eu anomalies are indicative of basic rock source, whereas higher ratio and negative Eu anomaly indicate the silicic igneous rock sources (Cullers et al. 1987; Cullers 1994). The samples of the Jhuran sandstones show high ratio of LREE/ HREE and negative Eu anomaly (figure 6c) supported the silicic rock source. Table 6 shows the selected elemental ratios, i.e., Eu/Eu ∗, Th/Co, Cr/Th, Th/Sc, La/Th, La/Sc and La/Co of the Jhuran sandstone samples compared with other studies suggest that the studied sediments were derived from felsic rocks. The ratio of Gd N/Yb N indicates the nature of source rocks composition of the continental crust (Taylor and McLennan 1985). The plot of Eu/Eu ∗ vs. (Gd/Yb) N in figure 15 with the ratio of Gd N/Yb N = 0.8 − 3.04 shows that all the samples fall within post-Archean field, which is suggestive of post-Archean felsic rocks which could act as source rock.

Figure 14
figure 14

Bivariate plot of La/Sc vs. Th/Co (after Cullers 2002) shows that all the samples of the Jhuran Formation plot in silicic rock source.

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Figure 15
figure 15

Plot of (Gd/Yb) N against Eu/Eu ∗ of the Jhuran samples (after McLennan and Taylor 1991).

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Table 6 Selected elemental ratios of Jhuran sandstones correlated with those of sediments derived from silicic and basic sources, UCC and PAAS.
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The REE data of present study is compared with geochemistry of Nagar Parkar Complex, which is located in the northern part of Kachchh basin. The chondrite normalized REE pattern of grey granites, pink granites, rhyolites and basic dykes from Nagar Parkar Complex (Laghari 2004; Ahmad and Chaudhry 2008) is closely associated with the studied sediments (figure 6c). These rocks of Nagar Parkar complex are identified as possible source rock for the studied region with slight mafic input as it shows similar trend of studied samples. The negative Eu anomaly from the source rock is reflected in the sediments of the Jhuran Formation (figure 6c). Further detailed studies are required to understand the complexity and tectonic setting of Kachchh basin.

7 Conclusions

A comprehensive analysis based on petrography and geochemistry (major, trace and REE elements) were performed on the sandstones of the Jhuran Formation from Jara dome, Kachchh basin to deduce their palaeoweathering conditions, tectonic setting, source rock and provenance. The studied sandstone members of the Jhuran Formation have been analysed based on geochemical signatures to be arkose, sub-litharenite, wacke and quartz arenite type.

The value of CIA (15.6–71.7%) for all the sandstones suggests moderate to intense degree of weathering at the source area and the wide variation indicates non-steady state of weathering. The enrichment of Zr in the samples suggests the multiple recycling of sediments.

Various tectonic discriminant diagrams based on petrographic observations, major and trace elements infer that the studied sandstones were deposited in a passive continental setting. The present study suggests that the sediments of the Jhuran Formation were chiefly derived from felsic rock sources, i.e., granite and granitoid compositions and show no mafic input which was further supported by negative Eu anomaly and Zr enrichment. Geochemical characteristics of the sandstones from this study indicate that the possible provenance is from Nagar Parkar ridge rocks in the northern part of the basin.