摘要
A total of 120 samples from 12 sites were collected from two flanks of a fold. Stepwise thermal demagnetization has successfully revealed characteristic magnetization components from the rocks in each case. A well defined component determined from red fine grained sandstone is clustered in the northeasterly direction with shallow upward inclination ( D =29.3°, I =-19.2°, k =283.7, α 95 =7 3°, tilt corrected). The pole position (39.5°N, 247.3°E, dp =4 0°, dm =7 6°) derived from this component is close to the Permian pole for the Yangtze Block, indicating that the red fine grained sandstone has been overprinted. The red mudstone reveals two characteristic components. Component A with lower unblocking temperature, characterized by northerly declination and moderate to steep inclination, corresponds to a pole position overlay with the present North Pole. Component B ( D =129.1°, I =-23.6°, k =44 6, α 95 =7.8°, tilt corrected) with higher unblocking temperature, passes fold test, and yields a pole position (39.5°S, 185 1°E, dp =4.4°, dm =8.3°) different from the other poles for the Yangtze Block. It is therefore suggested that component B was probably a primary magnetization and the Yangtze Block was situated at low latitudes in the Southern Hemisphere in the Middle Cambrian.
A total of 120 samples from 12 sites were collected from two flanks of a fold. Stepwise thermal demagnetization has successfully revealed characteristic magnetization components from the rocks in each case. A well defined component determined from red fine grained sandstone is clustered in the northeasterly direction with shallow upward inclination ( D =29.3°, I =-19.2°, k =283.7, α 95 =7 3°, tilt corrected). The pole position (39.5°N, 247.3°E, dp =4 0°, dm =7 6°) derived from this component is close to the Permian pole for the Yangtze Block, indicating that the red fine grained sandstone has been overprinted. The red mudstone reveals two characteristic components. Component A with lower unblocking temperature, characterized by northerly declination and moderate to steep inclination, corresponds to a pole position overlay with the present North Pole. Component B ( D =129.1°, I =-23.6°, k =44 6, α 95 =7.8°, tilt corrected) with higher unblocking temperature, passes fold test, and yields a pole position (39.5°S, 185 1°E, dp =4.4°, dm =8.3°) different from the other poles for the Yangtze Block. It is therefore suggested that component B was probably a primary magnetization and the Yangtze Block was situated at low latitudes in the Southern Hemisphere in the Middle Cambrian.
基金
theNationalNaturalScienceFoundationofChina (GrantNo .4 93340 5 0 )
