Journal of Conference Abstracts

Permian Sponge Reefs in the East Kunlun Mountains, Southeastern Xinjiang, China

Shugang Tian¹, Jiasong Fan (6204@ihw.com.cn)² & Zengji Wang¹

¹ Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China

² Institute of Geology, Chinese Academy of Sciences, Beijing 100029, China

A well exposed Permian reef zone has recently been discovered in the western sector of the East Kunlun Mountains. This zone extends over 300 km in an East-West direction, from the Buhadaban Peak to the Aqikekule Lake, and has an outcrop width of 25-50 km in a North-South direction. Strata of the zone are folded into a compound syncline and have a rare thickness of over 7000 m. According to fusulinid assemblages, the strata are divided into two stages, the Qixian and the Maokouan, which span the Kungarian (late Early Permian) to Capitanian (Early Late Permian). The Qixian stage contains an assemblage mainly of Misellina, Pseudofusulina, Schwagerina and Parafusulina, and the Maokouan stage, Polydiexodina, Yangchiena, Toriyamaia and Afghanella.

The reef zone can be separated into three parts, with reef core facies, approximately 3000 m thick, occupying the middle part. Underlying strata consist of terrigenous clastic rocks, composed mainly of sandstone and conglomerate. These clastic rocks possess the character of fluvial and deltaic facies and are regarded as the basement to the reef core. Overlying strata comprise an alternation of sandstone and shale intercalated with limestone, and are interpreted as reef front facies.

The reef core carbonate unit is composed of grey-dark grey, massive sponge framestones and is made up of sphinctozoans, inozoans, bryozoans, Tubiphytes, solenoporacean algae and phyoloid algae. These frame builders are bound by Archaeolithoporella, Tubiphytes, fistuliporid bryozoans and tabulozoan sclerosponges. Accessory organisms include echinoderms, fenestrate bryozoans, brachiopods, bivalves, gastropods, ostracods and abundant foraminifera. Framework and intraclast grains are usually coated by several generations of submarine cement, i.e. isopachous fibrous calcite or radiaxial fibrous calcite. The remaining reef cavities were later filled by blocky sparry calcite. Based on their reef texture and framework, these sponge reefs can be well compared with examples of the same age from South China, the southern part of the Alps, and the Guadalupe Mountains.

The discovery of such a laterally extensive and thick Permian reef complex, with an extraordinarily well-developed reef core, at the northern margin of Palaeo-Tethys, is highly noteworthy.

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