An apparatus for use in estimating at least one property of an earth formation and a borehole fluid, comprising: a carrier configured to be disposed in a borehole in the earth formation; a pulsed neutron measurement assembly disposed at the carrier, the pulsed neutron measurement assembly including a pulsed neutron source configured to emit neutrons into the borehole and the earth formation, and a gamma ray detector configured to detect gamma rays and transmit signals corresponding to the detected gamma rays; a fluid density measurement assembly disposed at the carrier, the fluid density measurement assembly including the gamma ray detector and a gamma ray source configured to irradiate a borehole fluid with gamma rays, wherein the gamma ray detector is positioned relative to the gamma ray source to detect both of: gamma rays resulting from interactions between the neutrons and at least one of the borehole and the formation, and gamma rays emitted from the borehole fluid in response to irradiation from the gamma ray source; characterized by a processor configured to receive the signals from the gamma ray detector and generate gamma ray spectrum data, the processor configured to differentiate a pulsed neutron gamma ray spectrum associated with the interactions from a density gamma ray spectrum associated with the gamma rays emitted in response to the irradiation, wherein the gamma ray detector is configured to detect the gamma rays resulting from the interactions by detecting signals during a plurality of time gates within a pulsed neutron measurement cycle, the plurality of time gates including an inelastic gate, a thermal gate occurring after the inelastic gate and a background gate occurring after the thermal gate, and wherein the gamma ray detector is configured to detect the gamma rays emitted from the borehole fluid by detecting signals during the background gate. a carrier configured to be disposed in a borehole in the earth formation; a pulsed neutron measurement assembly disposed at the carrier, the pulsed neutron measurement assembly including a pulsed neutron source configured to emit neutrons into the borehole and the earth formation, and a gamma ray detector configured to detect gamma rays and transmit signals corresponding to the detected gamma rays; a fluid density measurement assembly disposed at the carrier, the fluid density measurement assembly including the gamma ray detector and a gamma ray source configured to irradiate a borehole fluid with gamma rays, wherein the gamma ray detector is positioned relative to the gamma ray source to detect both of: gamma rays resulting from interactions between the neutrons and at least one of the borehole and the formation, and gamma rays emitted from the borehole fluid in response to irradiation from the gamma ray source; characterized by a processor configured to receive the signals from the gamma ray detector and generate gamma ray spectrum data, the processor configured to differentiate a pulsed neutron gamma ray spectrum associated with the interactions from a density gamma ray spectrum associated with the gamma rays emitted in response to the irradiation, wherein the gamma ray detector is configured to detect the gamma rays resulting from the interactions by detecting signals during a plurality of time gates within a pulsed neutron measurement cycle, the plurality of time gates including an inelastic gate, a thermal gate occurring after the inelastic gate and a background gate occurring after the thermal gate, and wherein the gamma ray detector is configured to detect the gamma rays emitted from the borehole fluid by detecting signals during the background gate.