Soft Sedimentary Deformations Structures (SSDS) in Neoproterozoic Sharaban Formation, Kirana Complex, Pakistan: Regional Tectonic Implications

Abstract: Soft sedimentary deformation structures (SSDs) are imperative intuition into the paleotectonic history of an active tectonic setting; however, they become arduous when dealing with Neoproterozoic intracratonic regions. A lesser known stratigraphic unit of Neoproterozoic age Sharaban Formation in Pakistan was undocumented for its SSDs and other stratigraphic details. Sharaban Formation was always thought to be a unit of metaquartzites in previous studies. Though, sedimentary and metasedimentary rocks were present. These rocks are associated with primary and secondary sedimentary structures (especially SSDs). This paper aims to identify facies, primary and secondary sedimentary structures, especially SSDs, and later link them to the paleotectonic history of the region. For this purpose, a detailed field study was designed and carried out for more than a decade, with high-resolution field photographs, sketches, and plotting. Our fieldwork reveals that the formation is made up of four rock types, metasandstone, metaconglomeratic sandstone, limestone, and quartz veins. Numerous types of sedimentary structures are found like graded bedding, cross-bedding, imbrication, synsedimentary deformation structures, convolute structure, flame structure, folds and faults, chevron–type folding, ball and pillow structure, chaotic bedding, etc. The Sharaban Formation’s depositional environment is represented from low energy coastal environment to possibly a braided river system, while limestone could have deposited in a lagoonal setting. Later the SSDs could have been formed as a result of seismic activity subsequently controlled by the cratonic rifting in the larger Kirana-Malani Basin. Our results reveal that the Neoproterozoic was a time of extreme changes in tectonic conditions in the Kirana Malani Basin. Additionally, the SSDs found in the Sharaban Formation may help to understand the paleo-tectonics, tectono-dynamic reconstructions and structural kinematic studies in the NE Gondwana and other terrains like India (Bilara Formation), China and Siberia.