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Tectonic geomorphology and neotectonic setting of the seismically active South Wagad Fault (SWF), Western India, using field and GPR data

Maurya D. C., Chowksey V., Tiwari P., Chamyal L. S.

Acta Geophysica

2017

Vol. 65, no. 6

1167--1184

The South Wagad Fault (SWF) is an E–W trending fault that delimits the Wagad uplift comprising Mesozoic rocks in its northern upthrown block and Neogene–Quaternary sediments in the southern downthrown block. Detailed GPR investigations were carried out at seven sites selected after field studies. All profiles clearly showed the lithological contrast across the fault. The sharp amplitude contrast of the radar waves along a vertical to sub-vertical line is interpreted as the near surface trace of the SWF. As the Quaternary sediments are not displaced, we infer that no large magnitude earthquake has occurred along the SWF in late Quaternary. We attribute the low magnitude of neotectonic activity along the SWF to gentle warping of the Tertiary rocks in the southern downthrown block and greater accumulation of compressive stresses along the nearby KMF with an opposite structural setting. This is consistent with the observed variable levels of ongoing seismicity in the region around the SWF.

Temporal facies and diagenetic evolution of the mixed siliciclastic-carbonate Jajiya Member (Callovian–Oxfordian), Jaisalmer Formation, West India

Bhat G. M., Ahmat A. H. M.

Volumina Jurassica

2013

Vol. 11, no. 1

147–-162

Three broad lithofacies – bioturbated packstone- to rudstone, calcareous sandstone and cross-bedded rudstone to packstone are recognized within the Jajiya Member. The facies architecture and stalking pattern suggests deposition related to TST, HST and TST events punctuated by MFZ events in sequence stratigraphic terms. The 11.4 m thick sequence represents two fining upward and three coarsening upward cycles representing bar-bank depositional settings. The framework constituents of these facies were mainly controlled by the depositional conditions through space and time and have greatly influenced their diagenetic evolution. The main diagenetic features observed within the facies include compaction, early cementation and porosity reduction, micritization and neomorphism representing early or syn-depositional and post-depositional changes. Two phases of early mechanical compaction have largely governed porosity development in these facies. However, cementation, micritization and neomorphism have also contributed significantly in this respect. Evidence suggests that marine phreatic and fresh water phreatic environments dominated the diagenetic evolution of these facies. Calcite cementation was first formed, followed by iron oxide, while silica cementation occurred probably at a late stage.