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Paleomagnetic and rock magnetic studies on samples of 18 sites from the Cretaceous marine sedimentary rocks in the Tongyouluke section, Akto County, southwest Tarim,China show that the magnetic carriers of the Lower Cretaceous are dominated by hematite with some magnetite, while the magnetic carriers of the Upper Cretaceous are characterized by a combination of magnetite and titanomagnetite as well as hematite and goethite. Stepwise thermal demagnetization is performed and vector analysis is used to isolate magnetic components, which illustrates a single magnetic component or double magnetic components. The high temperature stable components are dual polarities and pass polarity test, reversal test and consistency test.The overall mean direction of the Lower Cretaceous is D = 27.0° , I = 42.0°, α95=6.5° with pole position at φ = 190.3° , λ=63.1 °, dp=4.9° , dm=8.0° . The overall mean direction of the Upper Cretaceous is D = 29.1 °, I = 39.4° , α95=11.2° with pole position at φ =190.9° , λ=60.3° , dp=8.0° , dm=13.4° . Compared with the inclination of the Early Cretaceous from red beds of north Tarim, the contemporary inclination of southwest Tarim is 10.0°±7.8° sharper, but it is still 8.1 °±8.9°, shallower than that of Early Cretaceous basalts in southwest Tarim. Although these paleomagnetic data show slightly larger confidence limit, the paleolatitude of the marine Cretaceous tends to lie between that of terrestrial red beds and volcanic rocks.