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 unconform ability of dip,such as Dahalaljun shan 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 rega rded as a directly sign to appraise orogeny,soit probably imply us that the Paleozoic ocean had closed and collided before Early Carboniferous.From that time,Tianshan has come in to continental activity.