Fig. 9

Compilation of detrital thermochronology results from the Himalayan foreland basin, modified from Webb et al. (2017). Detrital thermochronology involves sampling sedimentary materials and acquiring cooling ages from detrital components, in order to constrain the cooling history of the sediment source regions. In parts a and b, ⁴⁰Ar/³⁹Ar muscovite and zircon fission track zircon results are plotted, respectively, for dates younger than 50 Ma. ⁴⁰Ar/³⁹Ar muscovite ages date the cooling of muscovite crystals below 425 ± 25 °C (Harrison et al. 2009), whereas fission track zircon ages date the cooling of zircon crystals below 240 ± 30 °C (Hurford 1986; Bernet and Garver 2005). The data are shown using the Kernel Density Estimation (KDE) methodology, which plots the detrital dates as a set of Gaussian distributions (Vermeesch 2012). This approach allows the age ranges and abundances of different detrital age populations to be compared: peaks in the curves represent peaks in the detrital age populations. For these plots, the population for a single sample is shown as a curve, sample longitude is keyed to a color spectrum, and the depositional age is shown via the squares at the young (left) terminations of the curve. These data provide an approximation of the cooling experienced by adjacent Himalayan regions. Signals in the Himalayan foreland basin can be complicated by river sediment transport along the range trend, since not all river systems transport sediment perpendicularly away from the mountains and thus might not only represent cooling and exhumation over the limited extent of the range immediately adjacent to the sampling location. A general trend appears in these data: peaks in the cooling age populations appear to young to the east from 25 to 20 Ma to 10–8 Ma. This is consistent with an eastwards migrating pulse of hinterland cooling and erosion during this period