Dabieshan  
 

   The Dabieshan orogenic belt is a zone of long-lived shortening with late-stage extension that formed during Mesozoic time in central China. Regional basin analysis coupled with structural cross sections provides a means of reconstructing the paleogeography of the region from Triassic continental collision through early Tertiary extension. The overall distribution of different basin types in the orogenic belt indicates that there was a prolonged period of shortening throughout the Mesozoic that became less intense over time. Meanwhile, extension became more common from Jurassic into Tertiary time. Either compression or extension was isochronous but limited to different geographic regions and/or crustal levels or alternated repeatedly orogen-wide through time. Nonetheless, the orogen underwent gradual transition from overall shortening and crustal thickening to dominantly extension and rift basin formation although these events overlapped in time from the Jurassic through Early Cretaceous. Penecontemporaneous compression and extension across the orogen may reflect long-term (>100 m.y.) shortening and crustal thickening leading to gravitational spreading of the resultant thick crustal welt. We suspect that this prolonged history of shortening across two nearby (100 km apart) suture zones played some role in the exhumation of ultrahigh-pressure rocks from beneath the Dabieshan.

 
 

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