Abstract:

To study the Mesozoic-Cenozoic tectonic evolution of the Ningwu Basin and occurrence conditions of coalbed methane resources, samples were collected from the basin for fission track dating. The obtained fission track ages are of 156~139 Ma (zircon) and 97~47 Ma (apatite). Mesozoic-Cenozoic tectonic evolution of the basin is divided into three stages accordingly: Late Jurassic (156 Ma): granites on both sides of Ningwu basin began to uplift slowly, and the core depression was deposited; late Early Cretaceous (100 Ma): the paleo-temperature of the basin reached its peak, and the source rocks also reached the gas-generation peak; Late Cretaceous-Paleocene (79~59 Ma): rapid uplift erosion occurred. Although there was a short burial later, the region remained uplifted. Since the Late Oligocene (40~30 Ma), the region has been rapidly uplifted to the present position. Uplift erosion of the basin was spatially uneven: uplifting in the northeast was earlier than in the south, and the intrusion uplift and denudation rate on both sides was higher than that in the core. In the Mesozoic, the regional tectonics formed a series of en-echelon complex anticlines and synclines. In the Cenozoic, Indian Ocean plate compression on Eurasia may have formed the Ningwu Basin via strong uplift and thrusting of mountain ranges on both sides, which responded to the regional tectonic events in the North China Craton.

Key words: fission-track, uplift-erosion, Mesozoic-Cenozoic, Ningwu Basin