Lecture-06 Cenozoic Climate, Tectonic and Deposition | Dr. Burbank | Himalayan Geology | Naked Earth

Key controls on Late Cenozoic climate change in the Himalaya and the adjacent foreland will be briefly explored in the context of (1) big picture tectonics; (2) along-strike changes in precipitation patterns; and (3) the relationship of Himalayan precipitation to evolving topography. Along the southern flank of the Himalaya, much topographic change and resultant local climate and erosional change is driven by active thrust faults that raise resistant (pre-Neogene) bedrock above the pre-existing depositional surface. Used in combination with radiometric dates on interbedded volcanic ashes, dozens of local magnetic polarity stratigraphies of thick sequences of continental sediments, provide a robust temporal framework in which to reconstruct the deformational and depositional history of the Himalayan foreland, as well as the outward propagation of the range front. This remarkable chronologic control allows us to track the rates of propagation of major depositional units, such as late-stage conglomerates, and to reconstruct their spatial geometry in unusual detail. Bedrock cooling ages have been key in delineating major Cenozoic events of uplift, erosion, and cooling as various ranges have been actively uplifted. In some places geomorphic anomalies, such as high-elevation, low-relief surfaces, yield insights on recent deformation that is undetected by cooling ages. In other sites, such as near Nanga Parbat — where rock-uplift rates are very high — the topography does NOT reflect the rate of rock uplift, but instead reflects climatic gradients across these areas.