但其基底地层和混合岩形成时代较晚，为寒武纪和下古生代。
The basement strata and the migmatite, however, were formed much later, about Cambrian period and early palaeozoic era.
区内下古生界烃源岩经历了两次成油过程，第一次发生在加里东运动前的盆地沉降阶段，第二次发生在加里东运动后晚古生代陆表海沉积阶段。
The first was in the basin subsidence stage that was prior to the Caledonian movement. The second took place in the marginal sea deposition stage after the Caledonian movement.
研究认为中国古生代海相盆地在纵向上主要发育下寒武统、中上奥陶统—下志留统和二叠系3套烃源岩。
Vertically, 3sets of source rocks including the Lower Cambrian, the Middle-o-Upper Ordovician-Lower Silurian and the Permian were developed in Chinese Paleozoic Marine basins.
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