17
Stratigraphic and palaeoenvironmental framework of the Early Permian sequence in the Salt Range, Pakistan Shahid Ghazi 1,2,, Nigel P Mountney 1 , Aftab Ahmad Butt 2 and Sadaf Sharif 2 1 School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK. 2 Institute of Geology, Punjab University, Lahore 54590, Pakistan. Corresponding author. e-mail: [email protected] The Early Permian Gondwana regime succession of the Nilawahan Group is exposed only in the Salt Range of Pakistan. After a prolonged episode of non-deposition that spanned much of the Palaeozoic, the 350 m thick predominantly clastic sequence of the Nilawahan Group records a late glacial and post-glacial episode in which a range of glacio-fluvial, marine and fluvial environments evolved and accumulated. The Early Permian succession of the Salt Range has been classified into four formations, which together indicates a changing climatic regime during the Early Permian in the Salt Range region. The lower-most, Tobra Formation unconformably overlies a Cambrian sequence and is composed of tillite, diamictite and fresh water facies, which contain a floral assemblage (Gangamopteris and Glossopteris ) that confirms an Asselianage. The Tobra Formation is overlain by marginal marine deposits of the Dandot Formation (Sakmarian), which contain an abundant brachiopods assemblage (Eurydesma and Conularia ). Accumu- lation of the Dandot Formation was terminated by a regional sea-level fall and a change to the deposition of the fluvial deposits of the Warchha Sandstone (Artinskian). The Warchha Sandstone was deposited by high sinuosity meandering, avulsion prone river with well developed floodplains. This episode of flu- vial sedimentation was terminated by a widespread marine transgression, as represented by the abrupt upward transition to the overlying shallow marine Sardhai Formation (Kungurian). The Early Permian Gondwana sequence represented by the Nilawahan Group is capped by predominantly shallow shelf car- bonate deposits of the Tethyan realm. The sedimentologic and stratigraphic relationship of these four lithostratigraphic units in the Salt Range reveals a complex stratigraphic history for the Early Permian, which is mainly controlled by eustatic sea-level change due to climatic variation associated with climatic amelioration at the end of the major Gondwana glacial episode, and the gradual regional northward drift to a lower latitude of the Indian plate. 1. Introduction The Salt Range region of Pakistan has long been the focus of geological study because of its varied geology that ranges from Precambrian to Recent in age (Gee 1989; Ghazi 2009), yet the detailed sedimentology of the succession and its palaeoen- vironmental significance remain relatively poorly understood. The Salt Range of Pakistan forms southernmost part of the Sub-Himalayan Moun- tains, which stretch for more than 180 km east-west between the Jehlum and Indus rivers, along the southern margin of the Potwar Basin (figure 1). Within the Salt Range, a thick sedimentary cover, consisting of Precambrian to recent deposits (figure 2), unconformably overlies low-grade meta- morphic and igneous rocks (Gee 1989). The ini- tiation of Permian sedimentation in Pakistan and Keywords. Early Permian; palaeoenvironment; Salt Range; Pakistan. J. Earth Syst. Sci. 121, No. 5, Ocotber 2012, pp. 1239–1255 c Indian Academy of Sciences 1239

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  • Stratigraphic and palaeoenvironmental framework of theEarly Permian sequence in the Salt Range, Pakistan

    Shahid Ghazi1,2,, Nigel P Mountney1, Aftab Ahmad Butt2 and Sadaf Sharif2

    1School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.2Institute of Geology, Punjab University, Lahore 54590, Pakistan.

    Corresponding author. e-mail: [email protected]

    The Early Permian Gondwana regime succession of the Nilawahan Group is exposed only in the SaltRange of Pakistan. After a prolonged episode of non-deposition that spanned much of the Palaeozoic, the350 m thick predominantly clastic sequence of the Nilawahan Group records a late glacial and post-glacialepisode in which a range of glacio-uvial, marine and uvial environments evolved and accumulated.The Early Permian succession of the Salt Range has been classied into four formations, which togetherindicates a changing climatic regime during the Early Permian in the Salt Range region. The lower-most,Tobra Formation unconformably overlies a Cambrian sequence and is composed of tillite, diamictite andfresh water facies, which contain a oral assemblage (Gangamopteris and Glossopteris) that conrmsan Asselian age. The Tobra Formation is overlain by marginal marine deposits of the Dandot Formation(Sakmarian), which contain an abundant brachiopods assemblage (Eurydesma and Conularia). Accumu-lation of the Dandot Formation was terminated by a regional sea-level fall and a change to the depositionof the uvial deposits of the Warchha Sandstone (Artinskian). The Warchha Sandstone was depositedby high sinuosity meandering, avulsion prone river with well developed oodplains. This episode of u-vial sedimentation was terminated by a widespread marine transgression, as represented by the abruptupward transition to the overlying shallow marine Sardhai Formation (Kungurian). The Early PermianGondwana sequence represented by the Nilawahan Group is capped by predominantly shallow shelf car-bonate deposits of the Tethyan realm. The sedimentologic and stratigraphic relationship of these fourlithostratigraphic units in the Salt Range reveals a complex stratigraphic history for the Early Permian,which is mainly controlled by eustatic sea-level change due to climatic variation associated with climaticamelioration at the end of the major Gondwana glacial episode, and the gradual regional northward driftto a lower latitude of the Indian plate.

    1. Introduction

    The Salt Range region of Pakistan has long beenthe focus of geological study because of its variedgeology that ranges from Precambrian to Recentin age (Gee 1989; Ghazi 2009), yet the detailedsedimentology of the succession and its palaeoen-vironmental signicance remain relatively poorlyunderstood. The Salt Range of Pakistan forms

    southernmost part of the Sub-Himalayan Moun-tains, which stretch for more than 180 km east-westbetween the Jehlum and Indus rivers, along thesouthern margin of the Potwar Basin (gure 1).Within the Salt Range, a thick sedimentarycover, consisting of Precambrian to recent deposits(gure 2), unconformably overlies low-grade meta-morphic and igneous rocks (Gee 1989). The ini-tiation of Permian sedimentation in Pakistan and

    Keywords. Early Permian; palaeoenvironment; Salt Range; Pakistan.

    J. Earth Syst. Sci. 121, No. 5, Ocotber 2012, pp. 12391255c Indian Academy of Sciences 1239

  • 1240 Shahid Ghazi et al.

    AFGH

    ANIST

    ANMa

    in

    Karakorum Thrust

    Kohistan Arc reviRsudnI

    M B T

    Mantle Th

    rust

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    Potwar Basin

    Main

    Main

    BoundaryThrust

    S a lt R

    a n ge

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    Makerwal

    Isakhel

    Musakhel

    Mianwali

    Dhak Pass

    Nammal

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    Dandot

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    + + + ++

    Pail

    Bhadrar

    SALTRANG

    E

    72O 73O

    P O T W A R B A S I N

    SaloiWatli

    NilawahanKaruli

    Matan

    Amb

    SarinSanwans

    Salt Range T

    hrust(SRT)

    Precambrian

    L E G E N D

    Recent Alluvium

    Neogene

    Palaeogene

    Palaeozoic and Mesozoic+ +

    Measured sections

    Towns

    Salt Range Thrust (SRT)

    0 10 20 km

    N

    Study area

    Salt Range

    tlua

    Fhg

    aba

    laK

    a

    b

    Figure 1. Location map of the Salt Range. (a) Generalized tectonic map of northern Pakistan, showing location of the SaltRange and (b) outcrop belt of the Early Permian succession in the Salt Range of Pakistan showing the location of eightmeasured sections, which form the principal study localities discussed in this paper.

    India marked the end of long phase non-depositionthat had prevailed across much of the Indian sub-continent since the Late Proterozoic (Dasgupta2006). The Permian stratigraphy of the Salt Rangeis divisible into the Early Permian NilawahanGroup and the Late Permian Zaluch Group.These successions are of particular interest to

    sedimentologists and palaeontologists alike becausethe Gondwanan clastic sediments of Early Permianage are overlain by the highly fossiliferous LatePermian carbonate deposits of the Tethyanrealm. Thus, the two principal groups reect mar-kedly dierent geological and palaeogeographicalsettings.

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1241

    Miocene

    MiddleEocene

    EarlyEocene

    EarlyEocene

    Kamlial

    Chorgali

    Sakesar

    Nammal

    Patala

    LockhartPalaeocensequence

    AMB

    Sardhai

    Warchha

    DandotTobra

    Kussak

    Khewra

    Salt Range

    LatePalaeocene

    MiddlePalaeocene

    EarlyPalaeoceneLate Permian

    EarlyPermian

    EarlyPermian

    Cambrian

    EarlyPermian

    Early Permian

    35m

    40m

    35m

    40m

    80m

    25m

    4m

    2m

    40m

    100m

    22m

    7m

    18m

    70m

    72m

    Massive red and brown sandstone, dark red clay

    Limestone with intraformational conglomerate

    Massive limestone with chert nodules at the top

    Thinly bedded marly limestone interbedded withshale

    Black, brown, green shale with coal seams andinterbedded with limestone

    Grey limestone

    Dark-red claystone, dark-brown to reddish-brown carbonate and ferrugineous nodules

    Lavender, dark purple, dark grey shale, siltstoneand sandstone

    Light pink, red and grey sandstone with siltstoneand shale

    Conglomerate, sandstone, siltstone and shale

    Grey and purple shale and glauconitic sandstone

    Massive, maroon, fine-grained sandstone andmaroon shale

    Red gypsiferous marl with rock halite,gypsum-dolomite above and occasional oil shale

    Formation Age Max. Thickness(m) Lithology Description

    Cambrian

    Eocambrian

    Calcareous sandstone and impure limestone

    Dolomite

    Fine-grainedsandstone

    Coarse-grainedsandstone

    Shale

    Conglomerate

    Siltstone Thin-beddedlimestone

    Massive-beddedlimestone

    Marlylimestone

    Halite

    Marl

    Gypsum

    Legend

    Olive green and grey sandstone and shale with flaserbedding

    Figure 2. Summary of the principal stratigraphic units exposed in the Nilawahan Gorge area of the central Salt Range,Pakistan.

  • 1242 Shahid Ghazi et al.

    The original and still widely accepted stratigra-phic framework for the Early Permian in the SaltRange classied the Nilawahan Group successioninto four units: the Tobra Formation (Asselian),the Dandot Formation (Sakmarian), the WarchhaSandstone (Artinskian) and the Sardhai Formation(Kungurian) (Ghazi 2009). The ages assigned tothese formations are in accordance with the Strati-graphic Commission and the Geological Time Scale(Gradstein et al. 2004). Each lithostratigraphicunit is interpreted to have accumulated under adistinct climatic regime that progressively changedthroughout the Early Permian in the Salt Rangeregion from very cold to cold (the Tobra For-mation), to cold-cool (the Dandot Formation), tocool-warm (the Warchha Sandstone), to warm-hot(the Sardhai Formation) (Singh 1987; Veevers andTewari 1995).

    The aims of this paper are:

    to review the Early Permian stratigraphicnomenclature of the Salt Range,

    to demonstrate the importance of the Early Per-mian succession of the Salt Range in terms ofits signicance for assisting in the erection of aglobal palaeogeographic model for the Permianperiod, and

    to correlate the Early Permian successions of theSalt Range with other parts of the Gondwana-land sedimentary sequence.

    2. Permian rocks of the Salt Range

    The Salt Range of Pakistan is home to one ofthe best-known Permian sequences in the world(Waterhouse 1970; Singh 1987). These Permianstrata, which were deposited on the continen-tal margin of Indo-Pakistani Plate, are exposedthroughout much of the Salt Range (Wardlawand Pogue 1995). Pascoe (1959) rst noted thatthe Permian sediments unconformably overlie theCambrian sequence in the Salt Range and referredthem as the Early Permian age Shahpur System,which were sub-divided into Nilawahan Series andProductus Limestone Series. The Permian succes-sion is represented by a 700 m-thick accumula-tion of strata, which is readily sub-divided into twomajor units of roughly equal thickness (Kummeland Teichert 1970), each of which represents accu-mulation under markedly dierent depositionalconditions (gure 1). The Early Permian sequenceis assigned to the Nilawahan Group, which belongsto Gondwana regime and records sedimentationunder a range of continental and marginal-to-shallow marine setting (gure 1; Gee 1989; Ghazi2009). The Late Permian sequence is assigned tothe Zaluch Group, which belongs to the Tethyanregime and is entirely marine in origin (Kummeland Teichert 1970; Wardlaw and Pogue 1995).

    The four principal sub-divisions of the Nilawa-han Group (the Tobra, Dandot, Warchha and

    Pata

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    Amb F

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    ion

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    Khew

    raSa

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    iteGy

    psum

    Salt Ra

    nge

    Forma

    tion

    MarlGypsum

    Dolomite

    Khewra

    SandstoneKussak

    Formation

    Tobra Formation

    Dandot

    Formation

    Warchha

    SandstoneSardhai

    Formation

    noit

    amr

    oFbm

    A

    nois

    secc

    uSe

    neco

    eala

    P

    enot

    semi

    Ltra

    hkco

    L

    Patala

    Formation

    NammalLimestone

    SakesarLimestone

    ChorgaliFormation

    SW NE

    Chorgal

    i

    Formatio

    n

    Sakesar

    Limesto

    ne

    Nammal

    Limesto

    ne

    Marl

    enotsemiLtrahkcoL

    KamlialFormation

    KamlialFormation

    tlaskcoR

    Rocksalt

    Salt RangeFormation

    Figure 3. Sketch cross-section depicting the arrangement of Precambrian to Miocene stratigraphic units within theNilawahan Gorge (not to scale).

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1243

    Sardhai formations) are preserved in several out-crops distributed along the Salt Range Thrust(SRT), a major tectonic unit that denes thefrontal limit of the Salt Range uplift (gure 1).Exposure is widespread, though much is highlytectonically disturbed. However, well exposedlaterally- and vertically-continuous sections existin the main gorges that cut through the rangeand worthwhile exposures in several road cuttings(gure 1). This allows broad correlation of themain lithostratigraphic units across the Salt Rangeand a basic reconstruction of the principal palaeo-depositional environments represented (gures 2and 3). The succeeding Zaluch Group in the SaltRange is a well-exposed succession of exclusivelyshallow marine to intertidal deposits and is com-posed of the Amb, Wargal and Chhidru formations(Kummel and Teichert 1970; Fatmi 1973; Shah1977; Gee 1980, 1989; Mertmann 2003). The lowercontact of the Amb Formation is unconformablewith the Sardhai Formation and the upper contactof the Chhidru Formation is unconformable withthe overlying Mianwali Formation of Triassic age(gure 2; Kummel and Teichert 1970; Gee 1980;Mertmann 2003).

    3. Lithostratigraphic analysis of the EarlyPermian succession of the Salt Range

    The four Early Permian lithostratigraphic units ofthe Salt Range developed during four stages: the

    Asselian, Sakmarian, Artinskian and Kungurian(Pascoe 1959; Wensink 1975; Veevers and Tewari1995). These units are now known to be eachbounded by diachronous surfaces (Ghazi 2009),the nature of the diachronous relationships beingdemonstrable by the occurrence of distinctive bio-stratigraphic and lithostratigraphic characteristics(gure 4). Based on biostratigraphy and correl-ative stratigraphic position (gure 4) the age ofthe Tobra Formation is largely Asselian, the Dan-dot Formation is largely Sakmarian, the WarchhaSandstone is largely Artinskian and the SardhaiFormation is largely Kungurian (e.g., Krishnan1960; Balme 1970; Ghosh and Mitra 1970; Shahand Sastry 1973; Singh 1987; Veevers and Tewari1995; Wardlaw and Pogue 1995). The four litho-stratigraphic units of the Early Permian Nilawa-han Group of the Salt Range record sedimenta-tion within a variety of depositional environmentsthat range from glacio-uvial to shallow marine inthe Tobra Formation, marginal to shallow marinein the Dandot Formation, meandering uvial tomarginal marine in the Warchha Sandstone andopen shallow marine in the Sardhai Formation(gures 4 and 5).

    3.1 Tobra Formation

    The Tobra Formation is the oldest lithostrati-graphic unit of the Early Permian NilawahanGroup (gures 4 and 5). The Tobra Formation was

    Warchha Sandstone

    Sardhai Formation

    Dandot Formation

    Cambrian Sequence

    Tobra Formation

    Marginal marine facies

    Shallow water facies

    Glacio-marine facies

    Tillite faciesGlacio-fluvial facies

    Cam

    b-ria

    nE

    AR

    LY

    PE

    RM

    IA

    NLa

    tePe

    rmia

    n Palaeocene sedimentsAmb Formation

    SaloiWatliKaruliMatanNilawahanAmbSarinSanwans5.5 km27 km11 km9.5 km40 km25 km10 km

    eastwest

    Figure 4. Regional stratigraphic framework of the Early Permian Nilawahan Group in the Salt Range region.

  • 1244 Shahid Ghazi et al.

    ahhcraWtodnaD iahdraS

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    ains.

    Hindeodus

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    FenestellaAthysisSpirifer

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    Skolithos

    AgePeriod

    Stage/M

    a

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    284.4

    275.6

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    ondwana

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    (Veeve

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    ari,1995)

    (Valdiya,1997)

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    299

    noitamroFrihclaT

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    Gangam

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    BR

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    Figure 5. Correlation of the Early Permian formations of the Salt Range with the Gondwanan Basins of India and themarine Tethys deposits. Data are compiled from Noetling (1901), Fatmi (1973), Singh (1987), Veevers and Tewari (1995),Wardlaw and Pogue (1995), Valdiya (1997), Mertmann (2003) and Gradstein et al. (2004).

    originally referred to as the Talchir Boulder Bedsby Noetling (1901), the name having been takenfrom the Talchir Group of Blanford et al. (1856)after its occurrence in Talchir State (Cuttack Dis-trict), Orissa, India (Krishnan 1960). Subsequently,the Stratigraphic Committee of Pakistan formal-ized the name of the unit as the Tobra Formation,after the village of Tobra in the eastern Salt RangePakistan (Fatmi 1973) and this is now consideredas type locality of the formation. The Tobra For-mation was the rst unit to accumulate and be pre-served in response to the CarboniferousPermianglaciations that inuenced the subcontinent duringthe Early Permian times. The unit is widespread inthe Salt and Trans-Indus ranges and its thicknessvaries from 10 m in the Khewra area of the easternSalt Range to 150 m in the Sarin and Zaluch areasof the western Salt Range (gures 1 and 4).

    The Tobra Formation is predominantly com-posed of greenish-grey to dark-grey, brown and

    black-coloured conglomerate and sandstone (gure6ab). Pebble to boulder-sized clasts are com-mon and are mainly composed of pink granite,gneiss and quartzite in a poorly sorted sandy andolive-green-coloured silty and mudy matrix (gure6ab). The average size of clasts measured at theWatli, Karuli, Nilawahan, Sarin and Sanwans areais 0.10.15 m in diameter. However, rarely largerclasts up to 0.35 m in diameter have been observedelsewhere (gure 6b). The surfaces of the majorityof clasts are generally polished and striated.

    Three lithofacies were identied by Teichert(1967) in the Tobra Formation (gure 4). A tillitefacies is restricted to the eastern Salt Range. Afresh water facies of alternating siltstone and shaleand containing a spore ora and a few scatteredboulders in its basal parts (glacio-uvial facies) islocated predominantly in the central Salt Range. Amixed facies of diamictite, sandstone and boulderbeds of marine and estuarine origin (glacio-marine

    Figure 6. (a) Example of matrix-rich conglomeratic tillite deposits in the upper part of the Tobra Formation in the Watliarea, eastern Salt Range. Note the varied composition and size of the clasts (hammer is 0.3 m long). (b) Example ofstratied glacio-marine diamictite (shale with large dropstone of pink granite) in the upper part of the Tobra Formationin the Sarin area, western Salt Range (hammer is 0.3 m long). (c) The erosional contact between the marine shale of theDandot Formation and an overlying uvial channel at the base of the Warchha Sandstone, Amb area, central Salt Range(hammer is 0.3 m long). (d) Petried wood in the upper part of the Dandot Formation in the Saloi area, eastern SaltRange (pencil is 0.154 m long). (e) The contacts between ne-grained marine sandstone facies of the Dandot Formationwith underlying glacio-marine facies of the Tobra Formation and overlying uvial channel of the Warchha Sandstone inthe Sanwans area, western Salt Range. (f) Photograph showing upper erosional contact of the Warchha Sandstone withoverlying red-coloured Palaeocene sequence in the Saloi area, eastern Salt Range (hammer is 0.3 m long). (g) Photographshowing the Sardhai Formation unconformably overlain by Palaeocene Strata in the Matan area, central Salt Range. (h)Photograph showing the Sardhai Formation overlying the Warchha Sandstone with an unconformable relationship and itselfoverlain by the Amb Formation of the Zaluch Group in the Sarin area, western Salt Range.

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1245

    a

    Shale

    Shale

    Dropstoneof pink granite

    b

    c

    Dandot Formation Warchha Sandstone

    Petrified wood

    d

    Tobra Formation

    Dandot Formation

    Warchha Sandstone

    30 m

    m52

    0

    e

    Warchha Sandstone

    Palaeocene sequence

    f

    Sardhai Formation

    Palaeocene Strata

    Sandstone

    Shale

    12 m

    m5

    0

    g

    Warchha Sandstone

    Sardhai Formation

    Amb Formation

    30 m

    m52

    0

    h

    .

  • 1246 Shahid Ghazi et al.

    facies) is located predominantly in the western SaltRange.

    Based on the occurrence of age-diagnostic plantfossils including Gangamopteris, Glossopteris andStriatopodocarpites sp., an Early Permian (Asselian)age has been assigned to the Tobra Formation(Balme, in Teichert 1967; Shah and Sastry 1973;Gee 1989). The basal contact of the formationwith the underlying Cambrian sequence is markedby an angular unconformity (Lillie et al. 1987) anddemonstrates a major episode of non-deposition,uplift and erosion that resulted in the absenceof the entire Ordovician to Carboniferous record.The upper contact is gradational with the over-lying Dandot Formation and indicates a gradualtemporal change in both lithofacies and climateregime.

    3.2 Dandot Formation

    The Dandot Formation is now formally recognizedby the Stratigraphic Committee of Pakistan (Fatmi1973), and is the ocial name for a unit that waspreviously known as the Conularia Beds (Wynne1878), Conularia-Eurydesma Beds (Waagen 1878)and the Dandot Group (Noetling 1901). The unitis 50 m thick at its type locality in the Dandotarea of the eastern Salt Range (Fatmi 1973; Shah1977), though is well developed throughout the SaltRange (gures 4 and 5), deposit erroneous claimby some workers (e.g., Fatmi 1973; Shah 1977) thatit absent in the western Salt Range. The DandotFormation exhibits a lateral variation in lithofa-cies (gure 4) and gradually changes from strata ofmarginal marine origin to strata of shallow marineorigin in the western Salt Range (Noetling 1901).The maximum exposed thickness of this formationis 70 m and is recorded in the Sarin and Sanwansareas in the western Salt Range.

    The formation in the eastern Salt Range is mainlycomposed of alternating laminated ne-grainedsandstone, claystone and shale units. The sand-stone is generally micaceous, greenish-grey, light-brown and olive-green in colour, whereas the shalesare dark-green to dark-grey in colour (gure 6c).In the Saloi area, large pieces of petried wood(510 m long and 0.6 to 0.12 m thick) have beenobserved at the top of the formation (gure 6d),which was previously wrongly described by Buttet al. (1994) as a vitric ow or volcanic glass bed.Thin beds of black shale (12 m thick) are recordedat a few places. In the Karuli, Matan and Nilawa-han areas of the central Salt Range thin sandstonebeds about 2030 mm thick are interbedded inan otherwise shale-dominated succession and theseare predominantly restricted to the lower part ofthe formation. The upper part of the formation is

    composed of alternately laminated micaceous ne-grained siltstone and claystone and shale beds thatare extensively burrowed.

    The Dandot Formation is generally composed ofthick, dark-coloured massive mudstone and ne-to medium-grained sandstone in its lower parts inthe western Salt Range, whereas, in its upper partsthe unit is composed of interbedded, light-brown ordark-grey, micaceous, ne-grained sandstone andsiltstone. The top-most part of the Dandot Forma-tion exhibits thin coal seams in the Sarin area ofthe western Salt Range.

    Flaser, lenticular and wavy-bedding, and ripplecross-lamination are abundant in the sandstonebeds of the Dandot Formation. Some sandstonebeds show bituminous staining in the lower andmiddle parts of the formation. Additionally, theinterbedded, ne-grained sandstone, siltstone andshale units are rich in glauconite in places. Anabundant and varied of faunal assemblage hasbeen reported from the Dandot Formation, includ-ing Eurydesma, Conularia, Discina, Martiniopsis,Chonetes, Neochonetes (Waagen 1883; Reed 1944;Waterhouse 1970; Fatmi 1973). Pascoe (1959) andKrishnan (1960) reported marine bivalves fromeastern Salt Range belonging to genus Eurydesmaand other fossils including Eurydesma cardatum,E. hobartense, E. punjabicum, E. Subovatum,Pterinea cf. lata, Nucula pidhensis, Aviculopectensp., Astartila cf. ovalis, Cardiomorpha penguis(Brachiopod) Dielasma dadanense; (Bryozoa)Fenestella fossula.

    The gradational, transitional nature of thechange from the underlying Tobra to the overlyingDandot Formation implies a gradual but signi-cant regional rise in relative sea-level and a region-wide transgression of the Tethys Sea, probably inresponse to deglaciation across many parts of theGondwanaland at this time (Ahmad 1970; Shahand Sastry 1973; Dickins 1977, 1985; Dasgupta2006). The upper contact of the Dandot Formationwith the overlying Warchha Sandstone is uncon-formable (gure 6c) and is characterized by anabrupt change in lithology and sedimentary style.

    3.3 Warchha Sandstone

    The name Warchha Sandstone, which was pro-posed by Hussain (1967), has now been for-mally adopted by the Stratigraphic Committee ofPakistan (Fatmi 1973). Warchha Sandstone refersto the speckled sandstone of Waagen (1878), whichformed the lower part of the Warchha Group ofNoetling (1901). The Warchha Gorge in the cen-tral Salt Range was proposed as the type localityof the Warchha Sandstone, though no coordinatesor grid references were given (Fatmi 1973; Shah

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1247

    1977). However, in more than ve years of detailedeld work in the vicinity of the Warchha Gorgeand in the surrounding area, the principal authorhas not been able to identify a representative com-plete outcrop-section of the Warchha Sandstone.Therefore, based on its well exposed occur-rence and lateral continuity of outcrop, theMatan (724138E, 323946N) area and Karuli(724132E, 323740N) areas in the central SaltRange are herein proposed as the type localityand reference section for the Warchha Sandstone(gures 1 and 4).

    The Warchha Sandstone is exposed throughoutthe Salt Range and its thickness increases system-atically from the east (30 m) to west (155 m) ofthe outcrop belt (gure 4). The reduced thick-ness of the Warchha Sandstone in the easternSalt Range can be related to the gradual con-tinuous uplift of the eastern Salt Range (cf. Gee1989). The succession is composed of light-pink,red, reddish-brown and white-coloured ne- tocoarse-grained sandstone, which is conglomeraticin places and has interbeds of siltstone and clay-stone. It is characteristically speckled in places.Several ning-upward cycles are recognised withinthe formation and these are composed of con-glomerate and cross-bedded sandstone in theirbasal part and bioturbated siltstone and claystone/mudstone in their upper part (Ghazi 2005, 2009;Ghazi and Mountney 2009). Complete examplesof such cycles are characterised by seven litho-facies that occur in ascending order as stratiedgravely sandstone (Gt), coarse-grained troughcross-bedded sandstone (St), medium- to coarse-grained planar cross-bedded sandstone (Sp), rip-ple cross-laminated sandstone (Sr), very ne- tomedium-grained sandstone with at-bedding (Sh),parallel laminated siltstone and claystone (Fl) andmassive claystone/mudstone (Fm). Trace fossilsincluding Helminthopsis and Skolithos are observedat the top of the Warchha Sandstone.

    Clasts are mainly of plutonic and low-grademetamorphic origin, with an additional minor sed-imentary component (Ghazi and Mountney 2011).Textural properties of the sandstone are ne- tocoarse-grained, poorly- to moderately-sorted, sub-angular to sub-rounded and generally with a loosepacking. Compositionally, the Warchha Sandstoneis dominantly a sub-arkose to arkose in nature(Ghazi and Mountney 2011). A broad range ofsedimentary structures are recognised, includingdierent forms of bedding, cross bedding, rippleforms, ripple stratication, channels, ute casts,load casts, desiccation cracks, rain imprints, cone-in-cone structures, a variety of concretions and bio-turbation. The occurrence and abundance of thesestructures varies in a systematic manner through-out the vertical thickness of the succession. The

    nature of sedimentary structures in the WarchhaSandstone succession is closely analogous to themodern uvial deposits (Ghazi 2009). The grosslithology, sedimentary structures and cyclic natureof the Warchha Sandstone reveal a uvial style ofdeposition. Most of the Warchha Sandstone bedswere formed by continuous or intermittent cur-rent ow within migrating river channels, in whichbodies of standing water were rare (Ghazi 2009).

    The Warchha Sandstone unconformably overliesthe marginal marine Dandot Formation of EarlyPermian (Sakmarian) age (gure 6e). In the east-ern Salt Range, the Warchha Sandstone is uncon-formably overlain by shallow marine deposits ofPalaeocene age (gure 6f), and in rest of the SaltRange it is unconformably overlain by the Sard-hai Formation of Early Permian (Kungurian) age,which forms the uppermost unit in the Nilawa-han Group. Balme (1970) and Wardlaw and Pogue(1995) assigned an Early Permian (Artinskian) agefor the Warchha Sandstone on the basis of pollenspores.

    3.4 Sardhai Formation

    The Sardhai Formation represents the uppermoststratigraphic unit of the Nilawahan Group. Thename Sardhai Formation, which was taken fromthe Sardhai Gorge of the central Salt Range, wasproposed by Hussain (1967) and this locality hasnow been accepted by the Stratigraphic Commit-tee of Pakistan as the type section (Fatmi 1973).The unit was previously referred as lavender clayby Waagen (1878) and the upper part of WarchhaGroup by Noetling (1901). The Sardhai Formationis well-developed in the central and western ranges;but is absent in the easternmost part. It is 42 mthick at its type locality but its thickness variesfrom 25 to 65 m overall. The formation generallyforms poorly exposed slopes.

    The Sardhai Formation consists principally oflight- to medium-grey, greenish-grey and lavender-coloured silty-shale with thin interbeds of silt-stone and ne-grained glauconitic sandstone.Based on eld observations, the Sardhai For-mation in the Salt Range can be divided intothree parts on the basis of lithology (gures 4and 5). The lower part of the formation con-tains reddish-brown, lavender and dark-grey shaleinterbedded with greenish-grey to grey-coloured,ne-grained sandstone with occasional siltstoneinterbeds. The middle part is mainly composed oflavender and greenish-grey claystone interbeddedwith very ne-grained light-grey sandstone. Theupper part is predominantly composed of lavender,blueish to greenish-grey coloured shale with thinbedded greenish-grey siltstone. The upper parts

  • 1248 Shahid Ghazi et al.

    of the formation are generally sandier in the cen-tral Salt Range, whereas in western Salt Range thelower part is sandier. In many places the shale iscarbonaceous and contains some copper mineralsincluding chalcopyrite (Qureshi 1980). Minor chertand gypsum with occasional calcareous beds occurin the upper part of the formation (Fatmi 1973;Shah 1977). The lithology of the unit changes later-ally to black shale and brown-coloured argillaceouslimestone in Trans-Indus Ranges (Fatmi 1973).

    Hussain (1967) reported a variety of faunaincluding Anastomopora, Fenestella, Athyrsis andSpirifer from the Sardhai Formation. Bryozoansand Brachiopods are recorded in limestone bedsfrom Trans-Indus Ranges (Fatmi 1973; Qureshi1980). Alam et al. (1987) have identied shdebris, teeth and an environment-diagnostic Hin-deodus conodont from the Jhang-Well core sam-ple, which was drilled about 150 km south ofthe Salt Range in the Punjab Plain. The absenceor only limited development of the Sardhai For-mation in the eastern Salt Range area can berelated to its removal following the uplift due toa Pre-Palaeocene orogeny (Gee 1989). The upperpart of the Sardhai Formation was completelyeroded across the entire area during uplift at thistime. The lower contact of this formation with theWarchha Sandstone is erosional. The upper con-tact with the Palaeocene strata in the eastern SaltRange and with the Amb Formation of ZaluchGroup in western Salt Range is unconformable(gure 6gh).

    4. Depositional setting of the EarlyPermian succession of the Salt Range

    The region of the Salt Range at the marginof Tethys received sediments during the EarlyPermian time after a long post-Cambrian hia-tus similarly as the other Gondwana Basins ofPeninsular India (Mukhopadhyay et al. 2010). Ini-tial sedimentation in the Salt Range region tookplace due to melting of ice (Mukhopadhyay et al.2010) in the form of the Tobra Formation. Theweathering style and composition of the conglom-eratic clasts in the Tobra Formation have beeninterpreted to reect a glacial mechanism for trans-portation and deposition (Pascoe 1959; Teichert1967; Gee 1989). The Tobra Formation containsclasts dominantly of igneous and metamorphicrocks sourced from the Aravalli and Malani rangesthat lie about 600 km to the south of the SaltRange (Teichert 1967; Shah and Sastry 1973).The matrix has the same composition and ori-gin characteristics as the large clasts and likelyreects high rates of abrasion through the grind-ing eects of glacial action in the source area and

    along the sediment transport path. The presenceof glacially-polished surfaces, striations and whale-back knobs throughout much of the outcrop in theSalt Range are indicative of ice sheet movementover the older bedrock (Haldorsen et al. 2001).Melting of ice sheets resulted in glacio-uvial con-glomerate and pebbly sandstone deposits (e.g.,Angiolini et al. 2004). All the above characteris-tics indicate that the environment of deposition ofthe Tobra Formation in the Salt Range area wasmainly glacio-uvial (Teichert 1967; Fatmi 1973;Gee 1989).

    During the Sakmaria, deglaciation caused risein sea-level and seawater transgressed towardsSalt Range region, which is manifested by theoccurrence of marine fauna like Eurydesma inthe Dandot Formation (e.g., Bangert et al. 1999;Mukhopadhyay et al. 2010). Lithologically, theinterbedded, ne-grained sandstone, siltstone andshale units are rich in glauconite along withabundant aser, lenticular and wavy-bedding, andripple cross-lamination in the sandstone bedsof the Dandot Formation. The lithological andpalaeontological characteristics indicate a marineenvironment for the deposition of the DandotFormation, with cool water temperatures (

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1249

    greenish-grey and lavender-coloured shale withthin interbeds of siltstone and ne-grained glau-conitic sandstone deposits of the Sardhai Forma-tion was deposited in warmhot climatic conditions(Singh 1987; Veevers and Tewari 1995). The pres-ence of chert along with gypsum, chalcopyrite andmineral glauconite are all evidence for the preva-lence of marine environmental conditions duringdeposition of the Sardhai Formation (Wardlaw andPogue 1995).

    5. Early Permian sequencedevelopment in Salt Range

    Accumulation of the Permian sequence in theSalt Range commenced after a major break indeposition that encompassed the time intervalfrom the Middle Cambrian until the end of theCarboniferous (Kummel and Teichert 1970; Gee1989). Initial accumulation of the Early PermianNilawahan Group occurred under the inuence ofa series of major glacial episodes that aectedlarge areas of Gondwanaland throughout much ofthe CarboniferousPermian periods (Kummel andTeichert 1970; Veevers and Tewari 1995). How-ever, the later stages of the accumulation of theNilawahan Group appear to have been controlledby the eects of an increasingly warmer climateregime (Singh 1987). The occurrence of exclusive-ly marine successions both below (the DandotFormation) and above (the Sardhai Formation)the continental deposits of the Warchha Sandstoneindicate a major regression and subsequent marinetransgression associated with the lowering and ris-ing of the Tethys sea level during Early Permiantimes (Ahmad 1970; Shah and Sastry 1973; Singh1987; Ghazi 2009). Two regional sea-level changesare evident from the facies and stratigraphic rela-tionships of the Early Permian sequence in theSalt Range of Pakistan and also in India (Shah andSastry 1973). Evidence for the rst prominent sea-level change is present in the Early Permian (Sak-marian) Dandot Formation (Dickins 1977, 1985;Singh 1987). The relationship between upper partof the Tobra Formation and the overlying Dan-dot Formation is transitional (Teichert 1967) andrecords a progressive sea-level rise through theupper part of the Tobra Formation into the lowerpart of the overlying Dandot Formation, which iscorrelated with the globally identied Eurydesmatransgression (Visser 1997b) that is related to boththe melting of Gondwanan ice caps and eustaticrise in sea-level (Dickins 1977, 1985). This globalevent can be recognised in many parts of the worldincluding Indian subcontinent (Dickins 1977, 1985;Dasgupta 2006) and the Karoo Basin, South Africa

    (Von Brunn and Gravenor 1983; Visser 1997a).Eustatic sea-level rise associated with climate ame-lioration and enhanced rates of ice sheet melt-ing were the main causes of this transgression(Dickins 1977, 1985; Wardlaw and Pogue 1995).Vertical and lateral facies changes from shallowmarine to marginal marine within the DandotFormation imply a signicant basinward shift ofenvironment and lowering of the sea-level (cf.Veevers and Tewari 1995; Fielding et al. 2006). Asudden change in lithofacies from marginal-shallowmarine in the upper parts of the Dandot Forma-tion to meandering uvial in the Warchha Sand-stone is an indication of forced regression. Thisregression was most probably related to an isostaticrebound associated with the late stages of deglacia-tion across the region (Haldorsen et al. 2001). Thetopographically-elevated areas of the Aravalli andMalani ranges to the south and southeast of theSalt Range region may have been raised at thattime (Ghazi and Mountney 2011).

    The second major sea-level change occurredduring Late Artinskian to Early Kungurian time.The presence of trace fossils such as Helminthop-sis and Skolithos, which are indicative of shal-low and marginal marine conditions in sandyshoreline setting (Bjerstedt 1988), on the topsurface of the Warchha Sandstone demonstratesa landward shift of the shoreline position (e.g.,Bjerstedt 1988; Amireh et al. 2001; Fielding et al.2006) and subsequent marine ooding across theuppermost Warchha Sandstone surface. At thistime, the Tethyan Sea transgressed to form a broadembayment across much of the Salt Range area.The overlying Sardhai Formation was accumulatedin this embayment as a shallow marine succession(Veevers and Tewari 1995; Wardlaw and Pogue1995). The contact between the upper part ofthe Warchha Sandstone and the overlying Sard-hai Formation is an unconformable and erosivewave ravinement surface, which was generated asthe transgression proceeded across the area. Thistransition from uvial-coastal to shallow marinesediments in the Salt Range is the principal evi-dence for a region-wide transgressive event associ-ated with a signicant rise in relative sea level. Thissecond sea-level change can be related to eustaticsea-level rise and climatic change. As temperatureincreased, perhaps as the nal phase of the Per-mian deglaciation occurred in the northern part ofthe Gondwanaland, so the nal eustatic sea-levelrise occurred (Shah and Sastry 1973). The direc-tion of transgressions seems to have been almostperpendicular to present geographic position of theSalt Range (gure 7). Accumulation of the Nilawa-han Group was terminated by a major marinetransgression that occurred from Middle Permianthrough to Late Permian time (gures 2 and 3;

  • 1250 Shahid Ghazi et al.

    N

    km0 300

    Aravalli Range

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    Early Permian (~280 Ma) global palaeogeography

    Figure courtesy of Ron Blakey

    MollewideProjection

    Salt Range

    Figure 7. Palaeogeographic map (showing present day longitude and latitude) of the Pakistani and Indian parts of Gond-wanaland during the Early Permian. The location of the Salt Range and main sediment source areas are shown (modiedafter Shah and Sastry 1973). During Permian times, the Pakistan region occupied part of Gondwanaland at a palaeolati-tude of 5055 south of the equator and was bordered to the north by a large marine embayment that formed part of theTethys Ocean.

    Kummel and Teichert 1970; Gee 1989; Wardlawand Pogue 1995; Mertmann 2000).

    6. Correlation with other Gondwana basins

    The Tobra Formation, which was previouslyknown as the Talchir Boulder Bed (Noetling 1901)in Pakistan, and Talchir Formation, previouslyknown as Talchir Group in India, can be correlated

    in terms of age, lithofacies stratigraphic position andfaunal assemblages with the Dwyka Group of theKaroo Basin, South Africa. A major glacial episodeis known to have occurred synchronously duringLate Palaeozoic times in both continents. The Dan-dot Formation can be correlated with Eurydesma-bearing Umaria marine beds, which overlie theAsselian age Talchir Formation in India (gure 5;cf. Shah and Sastry 1973). In the Manendragarhand Rajhrara areas of central India, these marine

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1251

    beds occur between the Talchir and Karharbari for-mations (cf. Shah and Sastry 1973). Ghosh andBasu (1967) suggested that Umaria marine bedsand the Dandot Formation (Conularia Beds) arethe marine equivalent of the basal Karharbari For-mation of India. Therefore, in the areas where themarine beds are missing, the Dandot Formationis equivalent to the upper part of the Talchir andKarharbhai formations (gure 5). Similarly, basedon stratigraphic position and biostratigraphic char-acteristics, the Dandot Formation can be related tothe Late Sakmarian to Early Artinskian age shal-low marine deposits of the Pebbley Beach Forma-tion of the southern Sydney Basin in New SouthWales, Australia (cf. Fielding et al. 2006). Water-house (1970) related the Dandot Formation toparts of the Permian sequence of Tasmania andWestern Australia, which commences with tilliteand is overlain by marine beds with abundantEurydesma.

    Based on lithological analogies and stratigraphicposition, the Warchha Sandstone which overliesthe Dandot Formation in the Salt Range is cor-related to the Barakar Formation of India (cf.Casshyap and Tewari 1982). Both formations arecharacterised by a succession of several uvialning-upward cycles of sedimentation and both areinterpreted to represent the preserved deposits ofuvial environment (gure 5). These two forma-tions were deposited in a similar palaeoenvironmen-tal setting but in two dierent basins which wereseparated by a high mountain chain (representedby the Aravalli Range) (Ghazi and Mountney 2011)at the time of accumulation. The absence of coal-bearing deposits in the Warchha Sandstone andtheir presence in the Barakar Formation are mostlikely due to the dierent geographic locations ofthe two basins and their dierent prevailing palaeo-climates. Based on stratigraphic position and age,the Sardhai Formation of Salt Range (Kungurian)can be correlated to the Barren Measures For-mation (Kungurian) of India and its equivalent,the Motur Formation, in the Satpura Basin ofIndia. The Sardhai Formation overlies the WarchhaSandstone (Artinskian) in the Salt Range and theBarren Measures Formation overlies the BarakarFormation (Artinskian) in India (gure 5).

    7. Palaeoenvironmental implications

    As a north-western part of the Indian Peninsula,the Salt Range region occupied a palaeogeographicposition that formed part of east Gondwanaland(Valdiya 1997). The basement rocks beneath theSalt Range are composed of Precambrian meta-morphic and plutonic constituents of the northernextension of the Indian Shield. The Eocambrian

    Salt Range Formation directly overlies crystallinebasement rocks and is followed by a shallow marinesequence of the Cambrian age. After the Cam-brian sequence, there was a pronounced interrup-tion in basin lling in the Tethyan realm in thenorthern margin of the Indian Peninsula (cf. Gee1989; Valdiya 1997). The whole of the GondwanicIndia was evidently uplifted at this time in what isknown as the Pan-African orogeny in Gondwana-land (Valdiya 1997). This basinal feature subse-quently commenced filling with Gondwana sediments,initially with glacio-uvial deposits of the TobraFormation (the Talchir) in a cold climate (Singh1987; Valdiya 1997). At this time, glaciers coveredthe Aravalli Range at least 600 km to the southand these extended northward to the Salt Range(gure 8). Teichert (1967) reported the occurrenceof Asselian age boulder beds (Tobra Formation)about 500 km south of the Salt Range in theBadhaura area in Rajasthan, India (gure 7). Sim-ilarly, after detailed work on the clast composi-tion, lithofacies pattern and palaeocurrent analysison the Talchir Formation (a lateral equivalent tothe Tobra Formation in India), it was concludedthat direction of the ice movement in Talchir(Tobra) times was from south to north (Ahmad1970; Sengupta 1970; Dasgupta 2006). This sug-gests that during Early Permian times drainagewas from the Badhaura area in south to the SaltRange in north to northwest direction and palaeo-slope would therefore have been towards north(cf. Krishnan 1960; Shah and Sastry 1973; Valdiya1997). To the east and south of the Salt Range, theelevated area of the Aravalli Range likely formedeastern coastline limit of an extended sea (gure 7;cf. Shah and Sastry 1973).

    The glaciers retreated as the climate amelioratedand sea levels rose, resulting in transgression acrossthe basin, as recorded by the Dandot Formation(cf. Singh 1987; Veevers and Tewari 1995). Thebasement rocks were uplifted in the east of the SaltRange and a marked relative sea-level fall occurred,eventually culminating in sub-aerial exposure ofthe entire Salt Range area. Seasonally heavy rain-fall in a hot and humid climate to the south helpedto establish a major river system (as representedby the uvial Warchha Sandstone), which owedinto the basin from the southsoutheast and dis-charged into a marine embayment that lay to thenorthnorthwest. The uvial system of WarchhaSandstone is more thickly deposited in the west-ern Salt Range than in the east. It is suggestedthat the Gondwana river channel, while maintain-ing an essentially northerly-owing course, gradu-ally shifted laterally to the west at this time, withinits basin of deposition. The meandering Warchhariver repeatedly shifted its position with time in itsoodplain.

  • 1252 Shahid Ghazi et al.

    The Salt Range being part of western IndianPeninsula had a northnorthwest-directed drainagesystem during the Early Permian, and the Warchhariver owed from the Aravalli Range northwardsto the Tethys Sea (gure 8), marine deposits ofwhich are now to be found exposed in the foothillsof the Himalayas (Valdiya 1997). However, over-all the network of the northnorthwesterly-owingriver systems ultimately discharged to the Tethysas demonstrated by the presence of marginal to

    shallow marine strata at the bottom and top ofthe Warchha Sandstone, and an overall north tonorthwesterly uvial transport direction.

    The depositional history of the Warchha Sand-stone witnessed marginal uplift of the easternSalt Range and down-wrapping. Episodic pulses ofuplift of the eastern Salt Range during the middleWarchha Sandstone is indicated by the presence ofsub-angular clasts of the limestone, sandstone anddolomite of the Cambrian sequence (Ghazi and

    Tethy

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    Figure 8. Tectono-stratigraphic evolution of the present-day Salt Range area through the Early Permian (a-d) Asselianto Kungurian times. These maps illustrate the change of sedimentation style from uvio-glacial (Tobra Formation), toshallow to marginal marine (Dandot Formation), to meandering uvial (Warchha Sandstone) and shallow marine (SardhaiFormation).

  • Stratigraphic and palaeoenvironmental framework of Early Permian sequence 1253

    Mountney 2011). The cessation of Warchha Sand-stone sedimentation is marked by an abrupt ter-mination of the uvial meandering setting and itsreplacement with very shallow marine deposits ofthe overlying Sardhai Formation (gure 4). Thissecond phase records a relative sea-level rise and ismarked by a regional unconformable contact at thetop of the Warchha Sandstone that is associatedwith wave ravinement during transgression. Thisphase is dated Artinskian to Kungurian age.

    The drainage pattern remained essentiallyunchanged throughout the Early Permian time(gure 8), being directed dominantly from southsoutheast to northnorthwest (Casshyap andTewari 1982; Valdiya 1997). A major tectonicevent can be recognised after the deposition ofthe Warchha Sandstone and overlying the SardhaiFormation, during which the whole Salt Rangewitnessed tectonism by uplift and subsidence.A sedimentary platform developed on Gondwanacontinental crust in front of Indian Shield and shal-low marine carbonated deposits of the Tethyanregime (Zaluch Group) are unconformably over-lying the clastic sediments of the Gondwanalandregime (Nilawahan Group) (Mertmann 2003). Thestratigraphic relationship of the Early Permianrocks in the Salt Range indicates that the basin wasopening and deepening towards north to northwestdirection. The preferred palaeogeographic recon-struction therefore suggests that the marine incur-sion in the Salt Range came from this direction(gure 7).

    8. Conclusions

    The Early Permian sequence of the NilawahanGroup in the Salt Range of Pakistan providesa sedimentary record of a late glacial and post-glacial episode in which a range of glacio-uvial,marine and uvial environments were developed.The Nilawahan Group records three major breaksin sediment accumulation: rstly at the base of theTobra Formation, secondly between the Dandotand the Warchha formations, and thirdly at the topof the Sardhai Formation. During Late Carboni-ferous times the entire Gondwanaland landmasswas covered by glaciers. As climate ameliorated,the glaciers commenced their retreat resulting inthe deposition of the Tobra Formation during theAsselian. Clast provenance indicates that theseglacial sediments were largely derived from themovement of ice sheets over and erosion of igneousand metamorphic basement rocks of the Aravalliand Malani ranges. A gradual rise in the sea-level through the latter phase of the Tobra Forma-tion deposition culminated in the transition to theaccumulation of marine sediments of the Dandot

    Formation in the Sakmarian. The presence of faunalike Conularia and Eurydesma, together with adistinctive lithofacies characterised by a distinc-tive suite of sedimentary structures conrm themarine-marginal to marine origin of the DandotFormation. The marine incursion represented bythe Dandot Formation did not persist and a sub-sequent fall in relative sea-level is marked by theonset of uviatile sedimentation of the WarchhaSandstone. By the end of the episode of Dandotsedimentation, climate amelioration had resultedin a change to cool-temperate conditions. Withinthe overlying Warchha Sandstone, the presenceof granitic and metamorphic pebble-grade clastswithin the otherwise ne- to medium-grained sand-stone facies suggests their derivation mainly viathe reworking of igneous and metamorphic rocksand their extended transport prior to deposi-tion in distal parts of a major river course. TheWarchha Sandstone in the Salt Range area recordsan episode of uvial, coastal to estuarine condi-tions during the Artinskian. A gradual relativesea-level rise caused by further climatic warmingand/or tectonic movement was responsible for amarine transgression over the top of the upper-most Warchha Sandstone surface and the onset ofmarine sedimentation of the Sardhai Formation.

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    Alam G S, Mashhadi S T A and Khan M A 1987 Interimreport on Permian coal exploration in Punjab Plains(drilling at Ashaba, district Jhang); Geol. Surv. PakistanInformation Release 286, p. 30.

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    MS received 22 February 2012; revised 3 May 2012; accepted 16 May 2012

    Stratigraphic and palaeoenvironmental framework of the Early Permian sequence in the Salt Range, PakistanAbstractIntroductionPermian rocks of the Salt RangeLithostratigraphic analysis of the Early Permian succession of the Salt RangeTobra FormationDandot FormationWarchha SandstoneSardhai Formation

    Depositional setting of the Early Permian succession of the Salt RangeEarly Permian sequence development in Salt RangeCorrelation with other Gondwana basinsPalaeoenvironmental implicationsConclusions