1. A method comprising: obtaining a gamma count rate decay curve one each for a plurality of gamma detectors of a nuclear logging tool, the gamma count rate decay curves recorded at a particular borehole depth; applying the gamma count rate decay curves to input nodes of a neural network; predicting by the neural network a geophysical parameter of the formation surrounding the borehole; repeating the obtaining, applying and predicting for a plurality of borehole depths; producing a plot of the geophysical parameter of the formation as a function of borehole depth.