June 4, 2010

Pliocene Cyprinids From Kunlun Pass Basin, Northeastern Tibetan Plateau

Through studying the newly-found cyprinid fish fossils, Wang and Chang have shown that the existence of comparatively rich waters in the Kunlun Pass Basin on the southern slope of the East Kunlun Mountain (at 4769 m above sea level) and possible connections between the water systems on north and south sides of the East Kunlun Mountain during the Pliocene. They also suggest a more humid climate in the area during the Pliocene than it is today and a less amplitude of uplift (approximately 1000 m) since the Pliocene than previously proposed.

The study is reported in Issue 4 of Volume 53 (April, 2010) of SCIENCE CHINA Earth Sciences by Wang Ning and Chang Mee-mann at Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.

Situated on the south slope of the East Kunlun Mountain, northeastern Tibetan Plateau, the Kunlun Pass Basin is a fault basin formed at the beginning of the late Cenozoic. It contains comparatively thick late Cenozoic sediments (~700 m), which documented the geological history of the area that is closely linked to the uplift of the Tibetan Plateau and the global climate and environmental changes. The geology of this area has long attracted the attention of geologists and paleontologists worldwide. Paleontological studies conducted in this area, however, have focused mainly on palynology, ostracods, and mollusks, indicating significant environmental changes since the Pliocene. Vertebrate fossils from the Basin, however, have not yet been specifically reported, and in general, the Cenozoic fossil fishes found from Tibetan Plateau are extremely rare.

In this work, Wang and Chang described newly-collected fossil fish bones, part of which is assigned to the genus Gymnocypris and the rest referred to the Cyprinidae bearing general similarities to those of the Schizothoracini or even the Gymnocypris. As the majority of modern Gymnocypris lives in lakes and rivers with broad valleys, they suggested the abundant Gymnocypris materials from the Kunlun Pass Basin may indicate a relatively extensive water system in the area of the Kunlun Pass basin during the Pliocene. The genus Gymnocypris was also referred to the "highly specialized grade", which would have been lived at an altitude ranging from 3750 m to 4750 m above sea level. Therefore, they estimated the amplitude of uplift in the East Kunlun area to be approximately 1000 m since the Pliocene, based on the comparison between the height span of the highly specialized grade of Recent schizothoracines and the elevation of the fossil locality.

"Our paper represents one of the first major studies on fossil fishes from the Tibetan Plateau, and hopefully will stimulate more researches in the area," said Chang. Recently, Chang and her colleagues have published another important paper (Chang et al., 2008) in this area, which described an extraordinarily thick-boned cyprinid from the northern Tibetan plateau. That Pliocene fossil fish was linked to the aridification of the region, and bears importantly on the paleoecology and paleoenvironment.

"This paper is interesting and important in several aspects. First, it reports the new paleontological discoveries from a place that is a living laboratory in studying evolution in action as well as history of the tectonic uplift of the 'roof of the world'. Second, the stepwise uplift of the Tibetan Plateau during the late Cenozoic is the most important and brought the profound changes of the environment"”geological, biological, and paleoclimatic etc. These changes in turn caused gradation and diversity in the fish group they reported. This paper definitely provides a lot of information to help us better understand how the fishes evolved when they ascended to the successive higher altitudes. This is a beautiful case study indeed," said one journal reviewer.


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