Discovery of the Late Jurassic coral fauna in the Tukari Formation at northern Oma Village, Gêrzê County, Tibet, China and its geological significances

About 33 genus 47 species corals were discovered in the so-called “Xiala Formation(Ft)” in north of Oma Village, Gêrzê County, Tibet. These newly-discovered corals indicate that the so-called Xiala Ft is the Late Jurassic Oxfordian-Kimmeridgian instead of the Early Permian in age. Therefore, the Xiala Ft is revised to be the Tukari Ft. Sabozhibule Ft is also suggested to be established and represents the strata below the Tukari Ft. Thus the Upper Jurassic in west part of the Bangong Co-Nujiang stratigraphic zone is suggested tobe divided into Sabozhibule Ft, Tukari Ft and Shamuluo Ft ascendingly. The present discovery of the Tukari Ft in the Oma area indicates that the Late Jurassic carbonate sediments spread widely and are much developed in the west part of the Bangong Co-Nujiang stratigraphic zone. Therefore, the Bangong Co-Nujiang stratigraphic zone did not suffer so strong and rapid compressional movement during the Late Jurassic as previous thoughts. The revision of the Xiala Ft to be the Tukari Ft also indicates that there wasn't the tectonic mélange phenomenon of the Permian limestone intermixed into the Jurassic Mugagangri Group. The Tukari Ft possesses good potential for petroleum-producing and storage for its considerable thickness and characteristic carbonate platform facies. Therefore, it should be pay due attentions to the petroleum prospects and evaluations of the Late Jurassic carbonate sediments in the Bangong Co-Nujiang stratigraphic zone and its north and south neighboring regions.