MICROFACIES, DEPOSITIONAL ENVIRONMENTS LIMEST ONE HORIZONS OF KIRTHAR FORMATION (MIDDLE-LATE EOCENE) IN FRONTAL PARTS OF SULAIMAN FOLD-BELT AND ADJOINING AREAS, PAKISTAN

Ghulam, Abbas (2013) MICROFACIES, DEPOSITIONAL ENVIRONMENTS LIMEST ONE HORIZONS OF KIRTHAR FORMATION (MIDDLE-LATE EOCENE) IN FRONTAL PARTS OF SULAIMAN FOLD-BELT AND ADJOINING AREAS, PAKISTAN. Doctoral thesis, University of the Punjab.

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Abstract

Kirthar formation (Middle to Late Eocene) is conformably underlain by Ghazij formation (Early Eocene) and is unconformably overlain by Nari formation (Oligocene) in Sulaiman sub-basin of Pakistan where it is comprized of four lithologic units: Habib Rahi limestone member, Sirki member, Pirkoh limestone and marl member, Drazinda member. These units are persistently present with variable thickness in study area. Nine major microfacies are recognized in 211 core and 248 outcrop samples from eleven (11) limestone horizons recorded in the Kirthar formation. The four lithologic units are end result of sea-level fluctuations in combination of tectonic events. Thick alabaster in the upper part of the Ghazij formation represents late Early Eocene regressive cycle resulting in restricted, evaporitic basin. Middle Eocene is the period of transgression during which the Kirthar formation is deposited in shelf setting extending from semi-restricted inner (lagoonal) to open marine outer part (shallow carbonate shoal/platform edge setting to deep basinal environments).The Habib Rahi limestone and Pirkoh limestone & marl are transgressive to highstand units deposited in 'catch-up' to 'keep-up' pattern while thick shales of Sirki and Drazinda members are generally prograding units. The limestones members experienced shallow to deep burial diagenetic environments involving marine phreatic, freshwater phreatic (super-saturation and under-saturation) and mixed marine diagenetic conditions. Algal encrustation and bioerosion were active under marine phreatic environments. Primary porosities were destroyed during overburden compaction while secondary moldic and fracture porosities were developed by dissolutions which later were occluded by successive calcite and dolomite cementation phases in eugenetic stage. Chemical compaction( pressure dissolution) was active in deep burial realm in mesogenetic stage. Present outcrops are subjected to sub-aerial conditions through uplifting in telogenetic stage. The microvuggy matrix and solution enlarged secondary intrapartcle porosities are common to abundant in core samples of Mari gas field while rare to sparse (2-5%) secondary moldic and vuggy porosities are ohserved in core as well as at outerops. These porositie are generally fabric selective and facies related and are produced by dissolution phase in deep burial diagentic conditions occurring in mesogenesis zone. The nature of aggressive fluids responsible for porosity development are indeterminate. The reservoir characters of the Habib Rahi limestone member should be well developed in the north and southern part of the Sulaiman sub-basin where potential facies for porosity development (platform edge/shoal/lagoonal) are thickly deposited. Same is the case with the Pirkoh limestone & marl member which has good reservoir potential in south western and southern parts of the study area. The source rock potential facies (deep, open marine shelf basinal) are thickly deposited in the central part of the basin, where the environments were conductive for deposition of organic rich oil shale horizons.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: microfacies, kirthar formation, ghazij formation, sirki, pirkoh limestone, drazinda, lagoonal, habib rahi, diagenetic, phreatic, eugenetic, telogenetic, mesogenetic stages, microvuggy, intrapartcle, microcystalline dolomite, ostracod grainstones, nari formation, habib rahi limestone member, sirki member, pirkoh limestone member, drazinda member
Subjects: Q Science > QE Geology
Depositing User: Muhammad Khan Khan
Date Deposited: 07 Nov 2016 10:34
Last Modified: 07 Nov 2016 10:34
URI: http://eprints.hec.gov.pk/id/eprint/3180

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