Occurrence of a Likely Tuff Bed between the Middle and Upper Siwaliks, Taunsa area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan

International Journal of Economic and Environment Geology

Rahman Ullah, Nie Fengjuin, Zhang Chengyong, Saqib Izhar, Idrees Safdar, Zhang Xin, Asim Ali¹ 

[1] State Key Laboratory of Nuclear Resources and Environment,East China University of Technology, Nanchang, Jiangxi, China, Atomic Energy Minerals Centre, Lahore, Pakistan;

关键词: tuff;    mineralogy;    illite;    chlorite;    biotite;    siwaliks;    sulaiman range;    pakistan;   

DOI  :  https://doi.org/10.46660/ijeeg.Vol11.Iss1.2020.407

来源: DOAJ

【 摘 要 】

AlikelytuffbedliesalongthegradationalcontactoftheMiddleandUpperSiwaliksineastern SulaimanRange,TaunsaareaofDeraGhaziKhandistrict,Pakistan.Thistuffaceous unitis0.5–3mthickand extends for 10 kmalong the north-south strike in the eastern limb of the Zindapir anticline. It is greyish white to whiteonfreshsurface,fine-grainedtosiltyatthebottom andclayeyatthetopandthusshowsafining upward grain-size grading. The lower part of the ashbedshows a prominent lamination defined bymegascopically visible abundant biotite,while the central and upper parts are so fine-grained that the individual minerals cannot be seen inhandsample.Unlikethelowerwell-laminatedpart,thecentralandupperpartsarecrudelylaminatedto apparentlymassive.Thebulksamples analysedwithX-raydiffraction consistofquartz,feldspar(plagioclase), biotite,clays,calciteandsomeoreminerallikelyspinel,whiletheclay-sizefractionscontainillite,chlorite, biotiteandprobablytheirmixed-layeredvarieties.Thecolour,texture,presenceofabundantbiotiteand stratigraphicpositionoftheTaunsatuffcorrelatewiththosereportedfromPotwarplateauand fromKashmir basin. However,the apparent absence of smectite fromthe XRD pattern makes the Taunsa ash bed different from bothPotwarandKashmirtuffs. Thepresent stratigraphicpositionof the tuffbedcorrespondstoshallow diagenetic zone, while the absence of smectite in the tuff and crystallinity of illite suggest that the tuff is probably deriveduponreworkingfromadeeperdiageneticzonebelongingtoalowerstratigraphiclevel. TheEoceneor otherolder pre-Siwalikunits inPakistanmayhaveorhadsomeprimary ashfalldepositsasreported in the northwesternHimalayasofIndia.Thisolder volcanicashmayhavebeenreworkedtoitspresentsiteof occurrencealongthe gradational contactof the Middleand the UpperSiwaliksinTaunsaareaofDeraGhazi Khan. However, theprimarysourceof the Taunsa tuffmaybelong morelikelyto ChagaiarcinPakistan thanto Dacht-e-Nawar volcanic complex in Afghanistan.

【 授权许可】

Unknown