Abstract: Data regarding thermal properties of sedimentary rocks are fundamental for basin modelling and deep temperature
prediction of sedimentary basins. The Qiongdongnan Basin, located at the northern margin of the South China Sea, currently is the key
area of the offshore hydrocarbon exploration in China. Reliable rock thermal properties are necessary for understanding the thermal
regime and thermal evolution of source rocks of the Qiongdongnan Basin. Although previous studies of rocks thermal properties have
been carried out for this area, there still exist such problems as limited measured data, under-representation and even controversies,
and it is emergent to retrieve some new measured data to fill this gap. In this study, 32 core samples of 19 boreholes were collected from
the Qiongdongnan Basin, and a systemic measurement of the thermal properties, i.e., thermal conductivity, radioactive heat production,
these thermal properties are presented. Integrating previous thermal properties with our new data, the average thermal conductivity and
radioactive heat production of the Cenozoic formation in the Qiongdongnan Basin are established. The radioactive heat contribution of
sediments within the basin account for nearly 33% of observed present-day heat flow. These measured data could provide a benchmark
for basin modelling and geothermal regime in the sedimentary basins of the northern South China Sea.

Key words: thermal conductivity, radioactive heat production, thermal properties, Qiongdongnan Basin, South China Sea