A detailed investigation of Jutana Formation for depositional setting in Indus Basin, Pakistan

Abstract

The origin and depositional setting of dolomites remain a complex and debated topic. In the Indus Basin Pakistan, the dolomites in Jutana Formation form a thick sequence within the Cambrian stratigraphy. The current study investigates the detailed depositional setting as well as the mineralogical composition of dolomites in the Jutana Formation to provide insight into their origin. The study focuses on integrating the microfacies and Scanning Electron Microscopy (SEM) with X-ray diffraction (XRD) data along with Wireline logs of Jutana Formation in Khewra Gorge, Eastern Salt Range. Based on field and petrographic observations, four microfacies were identified including (a) siliciclastic algal laminated dolomitic breccia (MJD-1), (b) burrowed sandy ferroan dolomicrite (MJD-2), (c) in-situ medium-coarse grained dolomicrite-dolosparite (MJD-3), (d) fine grained micaceous dolosparite (MJD-4). The microfacies analysis reveals that the deposition of the Jutana Formation is primary on carbonate platform in peritidal environments, ranging from supratidal to subtidal. Digenesis has obliterated most of the primary depositional features, making the interpretation of the original depositional setting challenging. The XRD analysis suggests that these dolomites are nearly stoichiometric and less ordered, indicating an early diagenetic setting, further supported by the presence of anhydrite seen under the SEM. The original depositional setting on the carbonate platform is also supported by cross plot graph wireline logs.