Paleomagnetic results of the Cretaceous marine sediments in Tongyouluke, southwest Tarim

Southwest Tarim (hereafter SW Tarim) is one of afew areas that well developed Cretaceous marinesedimentary rocks in China 1]. The Cretaceous marinesediments are stretched in front area along the Tian-shan and Kunlun Mountains. Toward the center ofTarim Basin, the Cretaceous sediments are buried bygreat thickness of Tertiary and Quaternary sedimentswith little exposure. Compared with the Cretaceousterrestrial strata of north Tarim, the Cretaceous marinestrata of SW Tarim continue and d…

Paleomagnetic results of the Cretaceous marine sediments in Tongyouluke, southwest Tarim

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°, a95=6.5° with pole position at f = 190.3°, ?=63.1°, dp=4.9°, dm=8.0°. The overall mean direction of the Upper Cretaceous is D = 29.1°, I = 39.4°, a95=11.2° with pole position at f =190.9°, ?=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 pa-leomagnetic data show slightly larger confidence limit, the paleolatitude of the marine Cretaceous tends to lie between that of terrestrial red beds and volcanic rocks.