Petrographical and Geochemical Study of Syn-Rift Sediments, Pranhita-Godavari Intracratonic Gondwana Basin, India: Genesis and Paleo-Environmental Implications

: The approximately 2 km thick ﬂuvio-lacustrine deposits of Pranhita-Godavari Gondwana syn-rift basin, ranging in age from 235 to 196 Ma, track the compositional changes from the Middle Triassic to Early Jurassic. Mineralogical and geochemical investigations, as well as paleocurrent data of the siliciclastic deposits of the four conformable formations—Yerrapalli, Bhimaram, Maleri and Dharmaram—trace the source of sediments to the south and southwest of the Gondwana basin. The dominance of arkosic to sub-arkosic sandstones in all the formations suggests mostly felsic sources. The high value of Zr/Sc, as well a high content of Hf, reﬂects the addition of zircon by sediment recycling. The index of compositional variability (ICV) and chemical index of alteration (CIA) values of these Gondwana samples suggest intermediate weathering of Proterozoic shales, granites and gneisses. The concentration of Cr and Ni, ratios of Eu/Eu* and (Gd N /Yb N ) suggest a dominant post-Archean source. The insigniﬁcant variation in ICV and CIA values across the studied Mesozoic formations corroborates the continuation of syn-rift tectonics of the Pranhita-Godavari Gondwana basin since the Late Paleozoic. Sandstone samples show a gradual shift from arkose to subarkose in Yerrapalli, Barakar and Maleri formations, and to sublithic arenite sandstones in the younger Dharmaram formation, indicating recycling. However, the insigniﬁcant variation of feldspar and/or quartz content throughout these Mesozoic formations suggests lesser tectonic activity. The paleocurrent direction, shifting from NNW to NE direction, suggests a change in basin tectonism and/or sediment supply, which is corroborated by mineralogical and geochemical data. This study presents the investigation of early to early Early Jurassic sediments of the syn-rift Gondwana basin of peninsular India. Geochemical compositions of the mudstones and petrography of sandstones were analyzed to identify provenance, paleoweathering conditions and tectonic setting. The geochemical data of major and trace elements show that the studied rocks have the same source. The QFR and QmFLt plots indicate the derivation of sediments from cratonic interior and transitional continental origin. Sandstone shows a gradual shift from arkose to subarkose in the Yerrapalli, Barakar and Maleri formations, and to sublithic arenite sandstones in the younger Dharmaram formation. Trace element data suggests the predominance of post-Archean source rocks. The chemical composition of Mesozoic mudstone samples reveals intermediate weathering conditions from Early Middle (Yerrapalli formation) to early Early Jurassic (Dharmaram formation). The binary diagrams and source rock discrimination plots reveal that the mudstones are mostly of felsic provenance. A change in tectonism and sediment supply is suggested due to the shift in the paleocurrent direction from NNW to NE, along with a gradual change in paleoclimate from semi-arid to humid condition, which is corroborated by petrographical observation as well. This shift might suggest the initiation of paleoslope reversal. The provenance, along with the paleocurrent data during Middle Triassic–Early Jurassic, indicate that the source might have been adjacent Proterozoic sedimentary rocks, the Karimnagar Granulite belt, the Khammam schist belt and the Eastern Ghats Granulite belt.


Introduction
By the Late Jurassic period, East Gondwanaland had started breaking apart from West Gondwanaland, which separated Africa from India-Antarctica [1]. The uplift at the India-Antarctic boundary reached a maximum in the Early Cretaceous, after which India started separating from Antarctica, thus created the modern coastline of eastern India [2]. Madagascar (the connecting link between India and Africa) rifted apart from India during the Late Cretaceous and the Indian Ocean opened up all along India's western margin [2]. These tectonic events caused the tilting of the east-Indian basins towards SE [3,4]. The sedimentary strata that deposited in different areas of peninsular India, mainly in four intracratonic basins, i.e., Pranhita-Godavari, Damodar, Satpura, and Son-Mahanadi, between Permo-Carboniferous and Early Jurassic time (290-182 Ma) are referred to as the Indian Gondwanas, and the corresponding sediments as the Gondwana sediments [5][6][7][8][9]. The provenance study and mineralogical and geochemical evolution of these riftogenic Gondwana sediments deposited in these four basins is conspicuously under-represented in the literature, except for the Satpura basin [10][11][12]. These Gondwana sediments are Table 1. The stratigraphy of the four formations (discussed in this paper), of the Upper Gondwana succession of the Pranhita-Godavari basin, central India, studied and summarized from [39][40][41].

Methods
Field investigation along the banks of rivers and small creeks provided sedimentological attributes of the four formations. The area of study comprises the north-western part of the Pranhita-Godavari Gondwana basin, India ( Figure 1). This area lies within the Adilabad district of Telangana and is covered by the Survey of India toposheets, 56M/7, 56M/8, 56M/11 and 56M/12 around Nambal, Dharmaram, Nannial and Annaram ( Figure 1A). Paleocurrent directions were measured on outcrops of cross-stratified sandstones and then the overall direction was cross-checked with the data available in the literature. A brief facies analysis is given in Table 2 and field photographs in Figure 2. Forty representative samples from all four stratigraphic units were collected from different stratigraphic levels, out of which 38 sandstone samples for petrographical analyses and 30 mudstone samples for geochemical analyses were considered.
Thin sections were prepared after treating the rock with epoxy resin and hardener. Petrographic analyses were carried out using Leica DM 4500P polarizing microscope attached with Leica DFC420 camera and Leica Image Analysis software (LAS-v4.6, Wetzlar, Germany) at the Department of Earth Sciences, Indian Institute of Technology (IIT) Bombay. Since matrices, siliciclastic cement or porosity were not observed in these Mesozoic sandstone samples, point counting was done using the Gazzi-Dickinson method [18,42]. Carbonate clasts are included in the lithic fragment pool. The samples were stained with sodium cobaltinitrite solution for the identification of K-feldspars (cf. [43]). Since the number of rock/lithic fragments is lower, other discrimination diagrams were not used in this study [44]. On average, three to five hundred points were counted per thin section for modal analysis (Table 3).
Major element analyses of 20 mudstone samples were carried out using the heavy absorber fusion technique of [45] (Code-4C FUS-XRF) method at Activation Laboratories Limited, Ontario, Canada. Powdered samples of 0.25 gm (<63 µm) were mixed with 0.75 g lithium metaborate (LiBO 2 ) and 0.50 g of lithium tetraborate (LiB 4 O 7 ) in a platinum crucible and fused in a muffle furnace at 1050 • C for 10 min. The crucible containing the fusion bead was immersed in 75 mL of 1 N HCl in a 100 mL glass beaker and then magnetically stirred for 1 h until the fusion bead dissolved completely. The sample volume was then increased up to 100 mL in a volumetric flask. Five mL of this solution was diluted to 50 mL with distilled water and used for the analysis. USGS standards, MAG-1, SBC-1, SCo-1 and SCo-2 were used for the analysis. Prior to fusion, the loss on ignition (LOI) was determined after heating 1 g of a powdered sample at 1000 • C for 2 h. The trace element concentrations of mudstone samples were determined by Perkin-Elmer SCIEX Model ELAN DRC II ICP-Mass Spectrometer using the 'Open Acid Digestion Technique' with PTFE teflon beakers at the National Geophysical Research Institute (NGRI), Hyderabad, India. For each sample, two to three replicate analyses were carried out in order to check that precision and accuracy were within acceptable limits. The precision was <5% relative standard deviation. The internal standard used was 103 Rh. Analytical details are provided in Balaram and Rao [46]. Major oxide trace element concentrations and their ratios were used to prepare binary and ternary plots (data given in Tables 4-7). The major oxide concentrations of the Mesozoic mudstone samples were normalized against Post-Archean average Australian shale (PAAS [47]) and upper continental crust (UCC [48] [47]). The degree of chemical weathering of source rocks was calculated from the chemical index of alteration (CIA: [49]) using the formula where CaO* is the amount incorporated in the silicate fraction of the rock. The higher CIA values represent higher degrees of weathering.
The index of compositional variability (ICV) is a measure of the abundance of alumina relative to the other major cations and also reflects the maturity of the source material of sedimentary rocks [54]. It is defined as ICV = (n(Fe 2 O 3 ) + n(K 2 O) + n(Na 2 O) + n(CaO*) + n(MgO) + n(MnO) + n(TiO 2 ))/n(Al 2 O 3 ).  Rapid suspension fallout.
In-fills of erosional depressions. Either filled gradually from side, or rapidly, thereby obliterating structures due to rapid fluid escape after deposition.
Occur in all four formations.       The index of compositional variability (ICV) is a measure of the abundance of alumina relative to the other major cations and also reflects the maturity of the source material of sedimentary rocks [54]. It is defined as ICV = (n(Fe2O3) + n(K2O) + n(Na2O) + n(CaO*) + n(MgO) + n(MnO) + n(TiO2))/n(Al2O3).

Results
A brief facies analysis of mainly the siliciclastics of the four different formations studied here is given in Table 2. These nine different facies occur in different associations in the four formations; however, detailed work in not the focus of this present study.

Results
A brief facies analysis of mainly the siliciclastics of the four different formations studied here is given in Table 2. These nine different facies occur in different associations in the four formations; however, detailed work in not the focus of this present study.

Petrography
The sandstone of the Yerrapalli formation is moderately well-sorted arkosic arenites, consisting of quartz and orthoclase feldspar grains, with an average composition of Q 55 -97 F 2 -45 L 0-2 ( Table 3). The framework grains are mostly fine-to medium-grained, sub-angular to sub-rounded, and cemented by calcite ( Figure 3A). Monocrystalline grains dominate the quartz fraction. Some of the monocrystalline quartz shows slight to strong undulose extinction. Point contact between the framework grains are observed. Heavy minerals, biotite grains and mud aggregates occur locally ( Figure 3B,C).   The Bhimaram sandstone is moderately sorted subarkosic arenite made up of mainly quartz grains with a few K-feldspars, with a general composition of Q 79 -84 F 15 -19 L 1 -2 ( Table 3). The framework grains are mostly medium-grained and sub-angular. Although most quartz grains are monocrystalline, a few polycrystalline grains are also present. Few grains of mica, heavy minerals and lithic fragments are present ( Figure 3D-F). Grains show point contacts.
Maleri sandstone is moderately well-sorted fine-to medium-grained arkosic to subarkosic arenite consisting of quartz and orthoclase feldspar, and has a general composition of Q 64 -97 F 3 -36 L 0 -1 (Table 3). Sand-sized mud aggregates, carbonate grains, lithic fragments and heavy and opaque minerals are the subordinate components. The framework grains are subrounded in shape with moderate sphericity. They dominantly show point contact between grains, along with a few sutured and long contacts. Both monocrystalline and polycrystalline quartz grains are present. Some of the monocrystalline quartz shows slight to strong undulose extinction. Only K-feldspar is present. Heavy minerals, micas and opaques comprise a small fraction of the framework constituents. Poikilotopic calcite cement occupies the intergranular spaces ( Figure 4A,B).   Dharmaram sandstone is made of moderately to poorly sorted, mostly quartz and K-feldspar grains. The framework grains show polymodal distribution. A subordinate amount of mica, carbonate grains, lithic fragments and opaque minerals are also present. The occurrence of polycrystalline quartz grains with tectonic fabric is common, unlike other formations studied here. The framework sand is medium to coarse and mostly sub-angular. This sandstone is subarkosic to sublitharenitic, with a general composition of Q 63 -90 F 3 -36 L 0 -12 ( Table 3). The quartz is mostly monocrystalline, although the polycrystalline variety is also found. Grains show mostly point contact and are locally sutured with irregular boundaries. Calcite cement dominates the interstitial spaces. (Figure 4C,D).
The Gondwana sediments in the QFR plot (adapted from [55]) mostly cluster in the subarkose area ( Figure 5A). In the QmFLt plot (adapted from [56]), sediments of Yerrapalli and Maleri formations mostly cluster in the transitional continental provenance, whereas those of Bhimaram and Dharmaram formations mainly cluster within the cratonic interior field ( Figure 5B).

Figure 4.
Photomicrographs showing (A) fine-to medium-sand-size, sub-rounded to sub-angular framework grains with dominantly tangential or point contact between them; (B) fine-to mediumsand-size framework grains of carbonate (c) and stained orthoclase feldspar (f) along with a few opaque heavy minerals (black arrow) and garnet (g), with poikilotopic calcite cement occupying the intergranular spaces within the Maleri sandstone sample. Photomicrographs showing (C) mostly quartz (monocrystalline-qm and polycrystalline-qp) and k-feldspar (f) grains along with carbonate grains (c) with tangential or point contact between the framework grains, in poikilotopic calcite cement; (D) medium-to coarse-sand-size, sub-angular polycrystalline quartz grain (red arrow), within the Dharmaram sandstone sample.   [55]) and (B) QmFLt plot (adapted from [56]) for sandstone samples of Yerrapalli, Bhimaram, Maleri and Dharmaram formations (Q-total quartzose grains (Qt), including monocrystalline (Qm) and polycrystalline (Qp) varieties, F-total feldspar grains, R-total unstable rock fragments, L-total unstable lithic fragments, Lt-L + Qp).

Major Oxides
The SiO 2 content of the mudstone from the Dharmaram and Yerrapalli formations is the highest with 50-70%, with only 50-60% in the Maleri formation. Al 2 O 3 /TiO 2 varies between 15 and 24, with the highest and lowest values in Yerrapalli and Dharmaram samples, respectively (  Figure 6A,B). The contents of MnO and P 2 O 5 are very low and display no major differences between the different formations. LOI values range from 7.4 to 15.96 wt% ( Table 4). The CIA values of the Mesozoic samples range between 61% and 94% ( Table 4).
The ICV values of the Mesozoic samples vary from 0.5 to 1.4 ( Table 4). The mudstone samples with high CIA have low ICV values and vice versa.

Trace Elements
The concentration of Zr decreases from 8000 ppm in the oldest Yerrapalli samples to 1500 ppm for the youngest Dharmaram samples ( Table 5). The concentrations of Zr (avg. 3900 ppm; ranging from 1535 ppm to 8036 ppm) and Hf (avg. 80 ppm; ranging from 31 ppm to 170 ppm) in the samples are considerably higher than that of the PAAS (210 ppm and 5 ppm, respectively). Samples of all formations show a higher average concentration of Th (avg. 20.4 ppm) compared to PAAS (14.6 ppm). The Zr/Sc ratio of samples shows considerable variation (135-455), whereas the Th/Sc ratio is primarily consistent (1-2.4) ( Table 7) and matches with the values of PAAS and standard shale samples (see Table 2 of [57]). However, the Zr/Sc ratio for the Yerrapalli formation shows a much higher range as compared to the younger formations. Similarly, the Y/Ni ratio of the Yerrapalli formation is much higher (avg. 1.25) as compared to the younger formations (~0.6). The Th/Co ratio is considerably consistent throughout the Mesozoic succession (0.5-2). The Cr/V ratio is also consistent throughout, ranging between 0.2 and 1.

Rare Earth Elements (REE)
Samples of the Yerrapalli formation show higher content of ΣREE (226-449 ppm, Table 7), while those of the Maleri and Dharmaram formations exhibit lower ΣREEs, ranging between 210-327 ppm and 192-392 ppm, respectively ( Table 7). The REE concentrations of the Mesozoic mudstone samples are normalized against chondrite, PAAS and UCC (values taken from [47] (Figure 6C-E). The chondrite-normalized REE patterns of the samples show LREE enrichment, relatively flat HREE, and a low to moderate LREE/HREE ratio (~6-15, Figure 6C; Table 7). UCC-normalized values reveal a more or less uniform positive pattern ( Figure 6E). Most chondrite-normalized mudstone samples show a narrow range of Europium anomaly (Eu/Eu*) values lying between 0.5 and 0.8. This range is close to that of PAAS (0.64) ( Table 7).

Composition of Source Rock
The LREE enrichment and the resemblance of the chondrite-normalized REE patterns to those of PAAS and negative Eu anomalies endorse the dominance of felsic source rocks in sediments [22,23,26,[58][59][60][61][62] (Figure 6B). High ratios of Th/Sc and Th/Co indicate felsic sources ( Figure 7A,B; Table 7). Cross-plot of Th/Co versus La/Sc, triangular plot of V-Ni-Th×10 indicate the predominantly felsic provenance ( Figure 7B,C). The abundance of zircons in the studied sandstones supports the felsic provenance ( Table 5). The low Cr/V and fairly low Y/Ni is in accordance with a mix of granite and ultramafic rocks ( Figure 7D) (cf. [57,63,64]). Low La/Th ratios (ranging from 2 to 5) indicate a predominant felsic source of sediments [65][66][67][68][69] (Table 7). Field observations and petrographical study of sandstones in Yerrapalli, Bhimaram, Maleri and Dharmaram formations indicated a predominant felsic source rock ( Figure 5A). The geochemical data of mudstone samples corroborate the felsic source of the studied formations.

Source Area Weathering and Recycling
The combined ICV and CIA values of the mudstone samples indicate intermediate weathering at the time of deposition for most of the samples (Figure 8A,B). The weathering trend observed in Figure 8A indicates depletion of Ca and Na (considering disappearance of plagioclase already), with more K-feldspar, illite and kaolinite in the sediments. The absence of plagioclase in sandstone petrography supports this view. This suggests an advanced stage of weathering, probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material [54,74]. However, two mudstone samples show a more mature source with higher CIA values, which could be due to compositional variation in the sediment itself. Recycling of sediments is indicated by the high Th/Sc and Zr/Sc [75] (Figure 8C; Table 7). Zr/Sc ratios increase almost independently of Th/Sc ratios due to the high concentration of the heavy mineral zircon ( Table 5). The petrographic observations also reveal mostly medium-fine sub-rounded grains of the older formations and comparatively coarser sub-angular of the Dharmaram formation, suggesting more transportation of the older sediments.

Tectonic Setting
The measured paleocurrent data during Gondwana sedimentation, as documented for this study, are consistent with those obtained by previous workers [38][39][40][41][51][52][53] (Figure 1B). The N-NW paleocurrent direction suggests the transportation of most detritus from the highs located in the south and southeasterly direction. Though an axial drainage system was dominant, small transverse drainages also persisted along the fault margins during the Mesozoic era [53]. However, north-easterly paleocurrent data of the youngest Dharmaram formation indicate the reversal in the direction of sediment supply. As the Gondwana breakup had started since the Jurassic time [1][2][3][4]29], this shift in the paleocurrent data suggest a change in paleoslope. The sub-angular framework grains with polymodal distribution of Dharmaram sandstones, along with increased lithic fragments, might point to an elevated western basinal margin. The high content of quartz and feldspar is typical for sand related to transitional continental (Yerrapalli and Maleri formations) to craton interior provenance (Bhimaram and Dharmaram formations) ( Figure 5B). Less significant variation in climate-sensitive proxies corroborates the continuation of syn-rift tectonic setting within the Pranhita-Godavari Gondwana basin (Figure 9; Tables 5 and 7). In the cross-plot of Eu/Eu* and (Gd N /Yb N ), the majority of Yerrapalli, Bhimaram, Maleri and Dharmaram mudstone plots in the field of post-Archean rocks indicate a dominance of the post-Archean source ( Figure 10A). Further, the lower values in the Cr vs. Ni cross-plot corroborate the post-Archean age of the source ( Figure 10B, [47]). The positive (La/Yb) N values (ranging between 5 and 14,~avg. 8.23) and (La/Sm) N values (ranging between 3 and 8,~avg. 4.09) of the studied samples indicate an early diagenesis adsorption mechanism [76]. Since all the fossils documented in the studied formations are continental, along with the sedimentological and geochemical evidence, deposition took place in a fluvial, intracratonic setting.
Schematic block diagrams showing the organization of the Middle Triassic-Early Jurassic paleogeography is given in Figure 11. Please refer to Table 2 of [52] for the details of the Pranhita-Godavari Proterozoic rocks lying on either side of the Pranhita-Godavari Gondwana basin deposit. The Khammam Schist belt and the Eastern Ghat and Karimnagar Granulite belts surround the Proterozoic sedimentary rocks [31]. Age dating of the zircon and monazite heavy minerals of the basin-fill Gondwana rocks and correlating them with those from the hinterland in the surroundings will be a direct provenance study in the future. A future work taking into consideration the isotope compositions of Strontium (Sr), Niobium (Nb), and Rubidium (Rb) can be performed for further understanding the palaeoclimate and for paeleogeoraphic reconstructions. Pearson's r correlations and discriminant function multi-dimensional plots remain to be analyzed for better understanding and interpretation of the tectonic setting [77][78][79]. A provenance study of the remaining formations of Pranhita-Godavari Gondwana basin, lying above Dharmaram formation, needs to be conducted in the future. It is noteworthy that due to the reversal of the drainage pattern post-Madagascar rifting, the paleocurrent should record a change in direction from the Late Cretaceous [37]. Hence, a change of source is expected thereafter.

Paleoenvironmental Implication
The presence of gypsum crystals in the mudstones of the Yerrapalli formation indicates precipitation of sulphate in a water-logged condition corresponding to a semi-arid environment. Essentially, the environment was fluviatile, with seasonal to semi-arid climatic condition. Scarce vegetation in the Yerrapalli formation indicates that the considerably low water table and prevailing oxidizing condition were not suitable for the preservation of plant life [51].
The sub-mature nature, coarser grain size and loosely packed grains of the Bhimaram formation suggest that these sandstones were deposited in a fluvial environment with high velocity. The coarse argillaceous sandstones produced bar complexes such that the sediments of the channel and the inter-channel facies amalgamated together to form a thick sandstone body (Table 2). Essentially, the climate was moist enough for the growth of vegetation.
The petrographic and geochemical studies of the sediments and extensive aquatic fossil record of the Maleri formation suggests that the climate was semi-humid to humid during the Late Triassic. The high abundance of mud aggregates along with shrink and swell clay rich sediments suggests a seasonal climatic condition [52]. The fact that all the stable isotope data of the Maleri carbonate samples are comparable to those of the Quaternary tufa sediments [40] suggests that the temperature during deposition of the Maleri sediments was comparatively cooler.      [31]). The paleocurrent direction indicates most of the detritus we transported from the highs located in the S-SE direction with respect to the Gondwana basin alo the axial drainage system. The study area is marked by a rectangle, which corroborates with t study area shown in Figure 1A.  [31]). The paleocurrent direction indicates most of the detritus were transported from the highs located in the S-SE direction with respect to the Gondwana basin along the axial drainage system. The study area is marked by a rectangle, which corroborates with the study area shown in Figure 1A.
The presence of immature sandstone along with the easterly dipping palaeocurrent direction of the Dharmaram sediments suggests a less reworked, less matured local provenance, mainly from the western margin of the rift basin. This also explains the occurrence of thicker and coarser sandstone bodies. The presence of poikilotopic calcite cement in association with shell fragments of aquatic organisms and presence of large petrified wood fragments confirms a wetland condition that prevailed during sedimentation of the Dharmaram formation. Thus, the climate was more humid during the Early Jurassic.
Hence, it can be said that there was a gradual change with respect to tectonism and climatic condition, as well as the nature of sedimentation, from the early Middle Triassic to the early Early Jurassic period in the Pranhita-Godavari rift basin. Schematic block diagrams showing the organization of the paleoenvironments during the above-mentioned time interval are given in Figure 12. Although a brief facies analysis has been given in Table 2, a thorough study pf sedimentological details remains to be conducted for the Yerrapalli, Bhimaram and Dharmaram formations, in order to elaborate on the paleoenvironmental conditions.  [40,52]; (IV) shows the scenario of the late latest part of the Triassic to early Early Jurassic when the coarse sediments of the Dharmaram formation were deposited in a transverse system, unlike in the previous stages, during which sediments were deposited in the axial drainage system. Note that the large waterbody in figure (IV) represents the lacustrine environment of the overlying Lower Kota formation [82,83], the h545details of which are not the focus of this paper.

Conclusions
This study presents the first comprehensive mineralogical-geochemical investigation of early Middle Triassic to early Early Jurassic sediments of the Pranhita-Godavari synrift Gondwana basin of peninsular India. Geochemical compositions of the mudstones and petrography of sandstones were analyzed to identify provenance, paleoweathering conditions and tectonic setting. The geochemical data of major and trace elements show that the studied rocks have the same source. The QFR and QmFLt plots indicate the deri- (I) shows the spatial relationship among different types of lithology during the early Middle Triassic, when fine sediments of the Yerrapalli formation were deposited; (II) shows the scenario of the late Middle Triassic, when essentially sandstone deposition took place during the sedimentation process of the Bhimaram formation; (III) shows the setting of the early Late Triassic sediments of the Maleri formation [40,52]; (IV) shows the scenario of the late latest part of the Triassic to early Early Jurassic when the coarse sediments of the Dharmaram formation were deposited in a transverse system, unlike in the previous stages, during which sediments were deposited in the axial drainage system. Note that the large waterbody in figure (IV) represents the lacustrine environment of the overlying Lower Kota formation [82,83], the h545details of which are not the focus of this paper.

Conclusions
This study presents the first comprehensive mineralogical-geochemical investigation of early Middle Triassic to early Early Jurassic sediments of the Pranhita-Godavari synrift Gondwana basin of peninsular India. Geochemical compositions of the mudstones and petrography of sandstones were analyzed to identify provenance, paleoweathering conditions and tectonic setting. The geochemical data of major and trace elements show that the studied rocks have the same source. The QFR and QmFLt plots indicate the derivation of sediments from cratonic interior and transitional continental origin. Sandstone shows a gradual shift from arkose to subarkose in the Yerrapalli, Barakar and Maleri formations, and to sublithic arenite sandstones in the younger Dharmaram formation. Trace element data suggests the predominance of post-Archean source rocks. The chemical composition of Mesozoic mudstone samples reveals intermediate weathering conditions from Early Middle (Yerrapalli formation) to early Early Jurassic (Dharmaram formation). The binary diagrams and source rock discrimination plots reveal that the mudstones are mostly of felsic provenance. A change in tectonism and sediment supply is suggested due to the shift in the paleocurrent direction from NNW to NE, along with a gradual change in paleoclimate from semi-arid to humid condition, which is corroborated by petrographical observation as well. This shift might suggest the initiation of paleoslope reversal. The provenance, along with the paleocurrent data during Middle Triassic-Early Jurassic, indicate that the source might have been adjacent Proterozoic sedimentary rocks, the Karimnagar Granulite belt, the Khammam schist belt and the Eastern Ghats Granulite belt.