This datasheet includes the results of thermogravimetric analysis (TGA) from marine surface sediments from the Laptev Sea. Sediment samples of ~20 mg were dried, ground, and analyzed in 70 μL aluminum oxide crucibles using a Mettler Toledo TGA/DSC 1. The samples were heated from 25 to 1000 °C at a rate of 10 °C min-1 under a constant argon flow of 20 mL min-1, following similar settings from Smeaton & Austin (2022). Following Lopez-Capel et al. (2006), weight loss between 200–400 °C is attributed to the decomposition of labile organic matter (OML), while weight loss between 400–650°C corresponds to the decomposition of recalcitrant and refractory organic matter (OMR). The percentage of labile organic matter (OML/OM) is calculated as [OML/(OML+OMR)]*100%