New evidence for a thin crust and magmatic underplating beneath the Cambay rift basin, Western India through modelling o
- PDF / 2,718,234 Bytes
- 16 Pages / 595.276 x 790.866 pts Page_size
- 45 Downloads / 177 Views
Ó Indian Academy of Sciences (0123456789().,-volV)(0123456 789().,-volV)
New evidence for a thin crust and magmatic underplating beneath the Cambay rift basin, Western India through modelling of EIGEN-6C4 gravity data AVINASH KUMAR CHOUHAN1,2,*, PALLABEE CHOUDHURY1 and SANJIT KUMAR PAL2 1 Institute 2
of Seismological Research, Gandhinagar 382 009, India. Department of Applied Geophysics, Indian Institute of Technology (Indian School of Mines), Dhanbad 826 004, India. *Corresponding author. e-mail: [email protected] MS received 5 January 2019; revised 1 November 2019; accepted 15 November 2019
The Cambay rift basin (CRB) is an intracratonic rift in the western part of India. The basin assumes great importance in petroleum exploration owing to the presence of thick hydrocarbon bearing sedimentary rocks. Previous investigations using deep seismic soundings (DSS), gravity and heat Cow data reveal that the CRB is characterised by a thin crust, high heat Cow and high density lower crust. In this study, a detailed crustal structure of the basin is presented by performing a 2.5D density modelling of the EIGEN-6C4 gravity data. Present study attempt to Bnd a plausible explanation for the variation in the Bouguer anomaly (BA) values from +20 to 50 mGal within the basin. It reBned the crustal model that is constrained using results from radial average power spectrum (RAPS) analysis of gravity data along with previous seismological and geophysical studies, which reveals that the values of average sedimentary and Deccan Traps thickness are in the order of 4–5 and 1.5–3 km, respectively, along the rift. It also presents possible evidences for a high density underplated layer of thickness 7–15 km along the central part of the CRB. To study the deep-seated features, upward continuation of the BA is carried out at heights of 30, 40 and 50 km. The extension of underplating layer is noticed in the present crustal model and in the upward continued BA in the western part, while it merges with the Moho in eastern part of the CRB. The Moho depths, varying from 31 to 37 km, are found to be shallower inside the CRB than the surroundings. It is inferred that the high BA values in the basin are due to the combined eAect of the high density underplated layer in the lower crust and a shallow Moho. Keywords. Cambay rift basin; EIGEN-6C4 gravity data; underplated layer; 2.5D density modelling.
1. Introduction Intracratonic rift basins are tectonic depressions in the Earth’s surface, which are generally formed within the stable cratonic platform (Withjack et al. 2002; Thybo and Nielsen 2009). These intracratonic basins originate from lithospheric thinning and subsidence (White and McKenzie 1989) and assume great importance in the hydrocarbon-
bearing provinces throughout the world. In the western margin of India, three intracratonic rift basins, namely, Kachchh, Cambay and Narmada, have been formed during the northward drifting of the Indian plate in early Jurassic, early Cretaceous and late Cretaceous, respectively (Biswas 1982, 1987).
Data Loading...
