Multiphase dolomitization in the Jutana Formation (Cambrian), Salt Range (Pakistan): Evidences from field observations, microscopic studies and isotopic analysis

Geologica Acta

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Title Multiphase dolomitization in the Jutana Formation (Cambrian), Salt Range (Pakistan): Evidences from field observations, microscopic studies and isotopic analysis
 
Creator Khan, S.
Shah, M.M.
 
Subject Cambrian dolomite; Salt Range; Diagenetic phases; O/C isotopes; Mg-isotopes.
 
Description Excellent dolomite exposures are observed in the eastern Salt Range (Pakistan), where the Cambrian Jutana Formation consists of two distinct units (i.e. oolitic – pisolitic unit and massive dolomite unit). Field observations revealed that the lower, oolitic-pisolitic unit mostly comprises medium to thick bedded, interlayered brown yellowish dolostone containing ooids/pisoids and faunal assemblages, and grey whitish sandstone with distinct depositional sedimentary features (i.e. trough-, herringbone- and hhummocky crossbedding). The upper massive dolostone unit consists of thick bedded to massive dolostone. These two units are separated by shale. Petrographic studies identified three dolomite types, which include: fine crystalline dolomite (Dol. I), medium-coarse crystalline dolomite (Dol. II) and fracture associated, coarse crystalline dolomite (Dol. III). Stable isotope studies indicate less depleted δ18O values for Dol. I (-6.44 to -3.76‰V-PDB), slightly depleted δ18O values for Dol. II (-7.73 to -5.24‰V-PDB) and more depleted δ18O values for Dol. III (-7.29 to -7.20‰V-PDB). The δ13C values of the three dolomite phases are well within the range of Cambrian sea-water signatures. Furthermore, δ26Mg-δ25Mg signatures (Dol. I; δ26Mg=-1.19 to -1.67, δ25Mg=-0.61 to -0.86 and Dol. II; δ26Mg=-1.34 to -1.59, δ25Mg=-0.70 to -0.83) indicate three phases of dolomitization in different diagenetic settings. First, an initial stage of dolomitization during the early Cambrian resulted from altered marine, Mg-rich fluids associated with the mixing zone mechanism. Second, a late stage of dolomitization was associated with burial during late Permian. A third dolomitization phase was related to post-Eocene times.
 
Publisher Geologica Acta
Geologica Acta
Geologica Acta
 
Contributor Addrian Immenheuser, Ruhr University Bochum
Higher Education Commission, Pakistan
Pakistan Institute of Nuclear Science and Technology, Pakistan
 
Date 2019-01-21
 
Type info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion

 
Format application/pdf
 
Identifier http://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2019.17.2
10.1344/GeologicaActa2019.17.2
 
Source Geologica Acta; Vol 17; 1-18
Geologica Acta; Vol 17; 1-18
Geologica Acta; Vol 17; 1-18
1696-5728
1695-6133
 
Language eng
 
Relation http://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2019.17.2/28458
 
Coverage Pakistan
Cambrian
Dolostone
 
Rights Copyright (c) 2019 Geologica Acta
 

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