一、前言西藏位于我国的西南边疆。它以世界最高、最大的高原雄伟容貌,屹立在亚洲的南部。西藏是世界上地层发育最全的地区之一,自古至今各时代地层几乎都有分布。各地层多属海相沉积,所含化石具有门类多、分布广的特点。自奥陶系起,地层时代的确定,多有化石佐证。 I. Preface Tibet is located in the southwest frontier of our country. It stands in the highest part of the world, the largest plateau majestic appearance, in southern Asia. Tibet is one of the most developed regions in the world. Since ancient times, Tibet has almost all strata of its own. The strata are mostly marine sediments, containing a wide range of fossils, widely distributed. Since the Ordovician Department, the formation of the era, there are many fossils evidence.