It is intended in our study that we can understand the characteristics of thermal properties of common sedimentary formations, and also that we obtain some useful mathematical formulation for their practical applications. Starting from the geometric mean model for the bulk thermal conductivity of composite materials, we have derived a set of general formulas for converting the observed values of porosity into three thermal properties (heat capacity, specific heat, and thermal diffusivity) of unconsolidated sediment samples. As a field example, for the clayey and sandy sediments of the eastern flank of the Juan de Fuca Ridge area, western offshore of North America, we show the particular functional relationships of how the four thermal properties, including thermal conductivity, are described mathematically when porosity is taken as the primary independent parameter. For the two major types of sediments, we have determined the standard values of solid grain thermal properties (thermal conductivity, thermal diffusivity, specific heat, and heat capacity) based on all the measured data. We can show that those standard values are compatible with another set of solid grain thermal properties which are estimated using the mineral composition data for the samples of the "clay" and "sand" types, respectively, in the studied area. We also make a brief mention about the future tasks of our studies on thermal properties prediction, in order to improve the method into the one with higher practical applicability.