Sedimentology and the facies architecture of the Ghaggar‐Hakra Formation, Barmer Basin, India: Implications for early Cretaceous deposition on the north‐western Indian Plate margin

Stuart M Clarke,Stuart D Burley,Pinakadhar Mohapatra,Hazel Beaumont,Andrew M Taylor

doi:10.1002/dep2.53

Abstract

AbstractFluvial strata of the Lower Cretaceous Ghaggar‐Hakra Formation are exposed in fault blocks on the central‐eastern margin of the Barmer Basin, Rajasthan. The sedimentology of these outcrops are described from 114 logs (thicknesses up to 100 m) and 53 two‐dimensional correlation panels. The formation comprises three distinct channel belt sandstone packages defined as the Darjaniyon‐ki Dhani, Sarnoo and Nosar sandstones separated by thick siltstone‐dominated floodplain successions. The sediments were deposited in a sub‐tropical, low sinuosity fluvial system that matures into a highly sinuous fluvial system. The Nosar Sandstone, the youngest of the three packages, exhibits a significant increase in energy and erosive power compared to those underlying it. This distinct change in fluvial style is interpreted as being rejuvenation due to an actively developing rift network forming accommodation space, rather than climatic controls acting on part of the depositional system. Consequently, the Ghaggar‐Hakra Formation at outcrop represents Lower Cretaceous syn‐rift deposition within the Barmer Basin with active localized fault movement from Nosar Sandstone times onward. These findings provide sedimentological evidence in support of pre‐Palaeogene northwest–southeast extension in the Barmer Basin. Moreover, they imply Cretaceous extension took place widely along the northern extremity of the West Indian Rift System consistent with plate tectonic models of the break‐up of Gondwana and evolution of the Indian Ocean. Outcrops of Lower Cretaceous strata are patchy across India and Pakistan. This study provides valuable material which, when combined with the available published data, facilitates a re‐evaluation of Lower Cretaceous palaeogeography for the north‐west Indian Plate. The reconstruction demonstrates a complex fluvial system, where the sediments are preserved sporadically as early syn‐rift strata. The findings imply a high preservation potential for early Cretaceous fluvial successions within rifted fault blocks near Saraswati and Aishwarya of the Barmer Basin beneath the Palaeogene fill that likely have significant potential for further hydrocarbon exploration.

Highlights

The Barmer Basin is the northern most basin of a series of rifts that comprise the West 54 Indian Rift System (WIRS; Fig. 1A), and hosts large hydrocarbon reserves within continental sediments of the basin fill (Dolson et al, 2015)
This study provides valuable material which, when combined with the available published data, facilitates a re-evaluation of Lower Cretaceous palaeogeography for the northwest Indian Plate
The Barmer Basin was considered to have developed in response to passage of the Indian Plate over the Reunion hotspot, giving rise to a syn- and post-rift Palaeogene to Eocene sedimentary fill, overlying Precambrian rocks of the Malani Igneous Suite (Fig. 2A, Crawford & Compton, 1969) and pre-rift Mesozoic sediments (Sisodia & Singh, 2000; Compton, 2009)

Summary

Introduction

The Barmer Basin is the northern most basin of a series of rifts that comprise the West 54 Indian Rift System (WIRS; Fig. 1A), and hosts large hydrocarbon reserves within continental sediments of the basin fill (Dolson et al, 2015). The Nosar Sandstone caps the formation at outcrop and 214 comprises medium to coarse-grained sands and granule-grade conglomerates with cross215 bedded sets and channel geometries with erosive bases, typical of deposition in an actively migrating braided fluvial system (Bladon et al, 2015a). The upper half of the element comprises horizontally258 laminated sandstone (Sh) and cross-laminated sandstone (Scl) in sets climbing at 5° These sediments are overlain by mottled, bioturbated, very fine-grained pedogenic sands (Sp; Fig. 6A). Facies do not form regular definable successions, but where present cross and horizontally465 laminated sandstones (Scl, Sh) are typically preserved near element bases, followed by massive fine-grained sandstone and siltstone (Sm, lm), with pedogenic (Ip) and haematitic siltstone (lhe) dominating. A decrease in sinuosity from the Sarnoo to Nosar sandstones, coupled with an increase in the proportion of bedload, an increase in bedform and barform migration, and stacking at all scales is atypical of increasing fluvial maturity (Fig. 11) and indicates rejuvenation of the whole system

Findings

Discussion

Conclusions