Geological meaning of unconformility of dip between the Lower Carboniferous strata and its underlying strata

The Lower Carboniferous strata outcropped in the most of Tianshan mountains in China , and most of them are in contact with underlying strata by unconformability of dip, such as Dahalaljunshan Formation in west ,which belongs to north Tianshan tectonics , Maanqiao Formation in middle, which belongs to middle Tianshan tectonics, Gancaohu Formation in east,which belongs to south Tianshan tectonics and so on . They are all in this way distinctly , it is a kind of zonal unconformility of dip, and always regarded as a directly sign to appraise orogeny , so it probably imply us that the Paleozoic ocean had closed and collided before Early Carboniferous. From that time , Tianshan has come into continental activity .