From craton stabilization to continent-continent collision : temporal and low-temperature thermal constraints on the long-term geologic evolution of central and northern India

Abstract

The geology of northern and central India preserves a rich and prolonged history of ancient crustal formation and stabilization, sedimentation and erosion, large igneous province magmatism, and modern continent-continent collision. Spatial and temporal constraints on these processes are imperative to (1) understand the long-term evolution of the Indian sub-continent, and (2) assess their potential relationships to Earth system evolution throughout deep-time. This study utilizes modern methods in low-temperature thermochronology, geochronology, geochemistry, and basin analysis to elucidate the complex evolution of central to northern India, from the formation and stabilization of the ~3.4–2.5 Ga Bundelkhand craton, to the timing of modern collision between the Indian and Asian continents. New apatite U-Pb ages from the Bundelkhand craton indicate that the Bundelkhand craton was exhumed through mid-crustal depths from ~2.4–2.3 Ga following the final stage of major felsic magmatism at ~2.5 Ga. Broad-scale exhumation at this time may have helped facilitate cooling and formation of a lithospheric root necessary to achieve craton longevity. Detrital zircon age populations from marginal basin deposits surrounding the Bundelkhand craton indicate major unconformities with distinct phases of deposition initiating by ~2.2 Ga (Gwalior and Bijawar basins), ~1.7 Ga (Lower Vindhyan succession), and ~1.2 Ga (Upper Vindhyan succession). Basement zircon and apatite (U-Th)/He (ZHe and AHe, respectively) data reveal an extreme inversion in AHe and ZHe dates that current radiation damage accumulation and annealing models cannot adequately predict for a given thermal history. However, thermal models derived from detrital ZHe and AHe data suggest that the craton last experienced peak burial temperatures of ~150 °C between ~850–475 Ma, followed by a major phase of exhumation at ~350–310 Ma that may have been driven by either late Paleozoic glacial scouring and/or dynamic topographic uplift. This unroofing is decoupled from a proposed global-scale increase in Neoproterozoic erosion, and comparison of low-temperature thermal models from continental interiors across the globe instead reveal diverse and diachronous unroofing histories that were in part impacted by their paleogeographic position in relation to various geologic events through time. Thermal models from central India additionally indicate that ~66–65 Ma Deccan Traps volcanism thermally perturbed the Bundelkhand region ~200 km north of present-day basalt exposures. The significant inversion in AHe and ZHe dates likely resulted from this short-lived heat pulse that occurred late-phase relative to a prolonged period of damage accumulation at low-temperatures. Although it remains unclear if the northern Bundelkhand craton was heated via burial beneath Deccan Traps flood basalts, it is possible that forebulge migration associated with the Himalayan orogenic system may have induced Cenozoic uplift and erosion of these rocks. New detrital zircon U-Pb-Hf data from early foreland basin deposits within the frontal Himalayan system of northwest India support models for initiation of India–Asia collision at ~59–54 Ma. Following collision, the modern Himalayan foreland basin system developed, and modern Himalayan alluvial deposits unconformably onlap Bundelkhand craton at its northernmost exposed margin.