中文摘要：

1931～1932年，博格·步林两次率领中瑞考察团（又名斯文·赫定考察团）到青海省柴达木盆地东部进行考察，在克鲁克湖与托素湖地区首次发现了丰富的新近纪哺乳动物化石。这批化石成为我国早期青藏高原古生物研究的奠基石。直至今日，双湖地区仍是青藏高原脊椎动物化石最丰富、研究程度最高的地区。柴达木盆地新近纪的堆积巨厚且连续，地层构造相对简单，盆地北缘地层出露好，是研究陆生哺乳动物演化的理想地点。

英文摘要：

The discovery by Birger Bohlin of a series of vertebrate fossil sites in the twin lakes region ( Tuosu Nor and Keluke Nor) of eastern Qaidam Basin during the Sino-Swedish Expedition in 1931 and 1932 was a major milestone in vertebrate paleontology for the Tibetan Plateau. Qaidam fossil mammals collected by Bohlin still represent the best collections from the plateau and serve as an important reference point for a period of time that saw dramatic climatic changes. The more than 4600 m of strata in eastern Qaidam, spanning over 13 million years in time, are ideal for establishing a detailed biostratigraphic record, but Bohlin's published specimens lack any reference to stratigraphy, which causes much confusion about the nature of his "Tsaidam Fauna."Bohlin did, however, make a fairly detailed documentation of locality information, much of which remains buried in archival records in Stockholm. This paper is an attempt to reconstruct Bohlin's fossil localities by synthesizing relevant archives and historical accounts, as well as field observations of our own during the past 13 years. Fieldnotes in Swedish are translated to English and several field sketches are published for the first time. As a result, we are able to relocate many fossil localities that are of stratigraphic and taxonomic importance.Bohlin mainly collected in three major areas, along the northwestern shore of Tuosu Nor, south of Huaitoutala, and south of Quanshuiliang train station, each with stratigraphic settings of their own. In his published descriptions, all fossils are included in his "Tsaidam Fauna." With the help of his notes and sketches and our field verification, we are now in a position to recognize at least three faunal horizons among Bohlin's collections: middle Miocene (Tunggurian) Olongbuluk Fauna, early late Miocene (early Bahean) Tuosu Fauna, and early Pliocene (Yushean) Huaitoutala Fauna.Of these fossil sites, Bohlin's Tuosu Nor locality is the best constrained within the modern stratigraphic framework due to the relatively short s