A spectral natural gamma-ray log in a 190 m borehole in Faxe chalk quarry confirms that Danish bryozoan and corallic limestones contain very low levels of natural radioactivity. Due to the low content of natural radioactivity it has been possible to observe the influence from cosmic radiation. The upper 20 m of the SNG-log shows a peak at 2.2 MeV caused by neutrons captured in hydrogen. As no neutron source is present, the neutrons originate from interactions beteen energetic cosmic radiation and the atoms of the chalk. Below 20 m no 2.2 MeV signal is observed.