The Changhsingian foraminiferal fauna of a Neotethyan seamount: the Gyanyima Limestone along the Yarlung‐Zangbo Suture in southern Tibet, China

Abstract

The Gyanyima Limestone is one of the isolated carbonate build-ups that have a probable Neotethyan seamount origin, distributed along the Yarlung-Zangbo Suture in southern Tibet. The limestone yields a highly diversified foraminiferal fauna consisting of nine fusuline and 37 taxa of non-fusuline foraminifers. This foraminiferal fauna is dominated by Reichelina pulchra, Colaniella parva and the characteristic boultoniid genus Dilatofusulina. We propose a new foraminiferal zone, the Reichelina pulchra-Colaniella parva-Dilatofusulina orthogonios Zone that represents the last prosperous stage of foraminifers just before the end-Permian mass extinction. This zone can be correlated broadly with the Palaeofusulina sinensis Zone in the Eastern Tethys based on advanced features observed in the major elements of the fauna. The composition of the fauna suggests that during the late Changhsingian, the Gyanyima Limestone occupied a palaeogeographic position at lower latitudes in the Neotethys. The fauna was largely influenced by the warm-water equatoro-tropical Palaeotethys.

Middle-Late Permian (Murgabian-Djulfian) foraminifers of the northern Maku area (western Azerbaijan, Iran

“…Wuchiapingian of Yunnan . ?Changhsingian of southern Tibet (Wang et al, 2010). ?Lopingian of Japan (Kobayashi, 2013, fig.…”

“…Changhsingian of NW Caucasus (Pronina-Nestell and Nestell, 2001). Changhsingian of Hungary (Théry et al, 2007) and southern Tibet (Wang et al, 2010). Lopingian of Japan (Kobayashi, 2013).…”

The Lopingian (Late Permian) of mid‐oceanic carbonates in the Eastern Palaeotethys: stratigraphical outline and foraminiferal faunal succession

“…Lopingian foraminifers have been studied in detail in two limestone blocks of these Neotethyan mid-oceanic carbonates; they are those at Lamayuru of Ladakh in northern India (Lys et al, 1980) and Gyanyima of southern Tibet in China (Wang and Ueno, 2009;Shen et al, in press;Wang et al, 2010) x . These studies provided basic data for summarizing important features of the Changhsingian foraminiferal fauna in the oceanic domain of the Neotethys.…”

“…Codonofusiella appears again; it is slightly different from pre-Changhsingian forms in having a rather smaller inner coiled part and relatively well-developed outer flaring lip. Late Changhsingian Codonofusiella is quite uncommon but is reported also from the north-western Caucasus (Pronina-Nestell and Nestell, 2001) and the Gyanyima Limestone of southern Tibet, China (Wang et al, 2010) x . In non-fusuline foraminifers, most genera that were found in the early Changhsingian fauna continue to occur.…”

“…One of the remarkable faunal characteristics is the occurrence of Dilatofusulina orthogonios, a peculiar boultoniid fusuline that has been only recorded in Qinghai Province of China (Sheng and Sun, 1975), the Lamayuru Limestone (Lys et al, 1980) and the Gyanyima Limestone (Wang and Ueno, 2009; Figure 9). In the Gyanyima Limestone, this species is restricted in the upper part of the Lopingian Gyanyima Formation while Reichelina pulchra and Colaniella parva are important throughout the succession (Wang and Ueno, 2009;Wang et al, 2010) x . Based on these characteristic foraminifers, Wang et al (2010) x proposed the Reichelina pulchra-Colaniella parva-Dilatofusulina orthogonios Zone to represent the latest stage of Permian foraminifers for the Gyanyima Limestone and correlated it to the middle to upper parts of the late Changhsingian Palaeofusulina sinensis x Zone of South China.…”