Tri- and tetracyclic terpanes in oils and as condensates from the cratonic region Of the Tarim Basin have been characterized by gas, chromatography mass spectrometry to investigate their geochemical applications in organic source input and maturity assessment. Most oils Show typical marine source input characterized by the dominance of C-23 tricyclic terpane (TT), low C19TT, and low C-24 tetracyclic terpane (TeT), while some oils/condensates show typical terrigenous input signatures as indicated by the dominance Of C19TT and C24TeT, which is obviously in conflict with early Palaeozoic geological settings Commonly used organic source input parameters, such as C19TT/C20TT; C24TeT/C26TT, and: C20TT/C23TT, show complicated correlation to maturity parameters C19TT/C20TT ratios are positively correlated to n-C-18/phytane (Ph); while C24TeT/C26TT and C20TT/C23TT ratios increase with n-C-18/Ph in a narrow maturity range and then decrease at an extremely high maturity level. Unusually high C19TT/C20TT, C20TT/C23TT, and C24TeT/C26TT ratios occur only in samples with very low summed tricyclic terpane concentrations, suggesting extensive thermal Cracking. An abnormal heating influence may cause an elevated C20TT/C23TT ratio when summed tricyclic terpane concentrations remain high: Experimental:, results from gold tube pyrolysis of two heavily biodegraded Oil sands illustrate that ratios of C19TT/C20TT, C24TeT/C26TT) and C20TT/C23TT increase with heating temperature at a low- temperature and then decrease, at a high temperature. The longstanding controversial issue regarding the relative thermal stability of tricyclic terpane components might be solved because previous studies have only covered part of thermal evolution history. Nevertheless, the distribution patterns of tri- and tetracyclic terpanes are no longer necessarily valid as an oil source correlation indicator: The so-called Cambrian-sourced end member or unknown source rocks in the Tarim Basin are most likely derived from the thermal alteration of normally distributed tri- and tetracyclic terpanes.