Ma'antang Fm

The famous “Ma'antang Formation Series” refers to the strata between the underlying Middle Triassic Tianjingshan Fm (termed the Huanglianqiao Fm in this lexicon) and the overlying Upper Triassic Xiaotangzi Fm (termed Kuahongdong Fm in this lexicon) as a set of sandstone, shale and bio-limestone. The type section is located at 100 m towards Chengdu from Ma'antang Station on Baocheng Railway, Jiangyou County, Sichuan. It was named by Deng Kangling in 1975. Uppermost formation in Tianjingshan Gr.

Synonym: The Ma'antang Fm is roughly equivalent to the upper part of Tianjingshan limestone in the generalized sense in terms of stratum and lithostratigraphic range. The Shangtianjingshan Fm of Zhu Sen et al. (1942) and Wang Naiwen (1966) and the "Hanwang Formation" of Chengdu Institute of Geology (1979). Wang Zunzhou et al. (1992) based on the fact that Member C of the original "Ma'antang Fm " is basically the same in lithology, lithofacies and biological facies as the Kuahongdong Fm, so the range of rock strata of this group is limited to the former "Ma'antang Fm ". Duan and Yi Duan assign it to the Carnian period of the Late Triassic. This book continues to use this meaning.

It is mainly carbonate rock, divided into two sections. Lower section is gray thin to middle microcrystalline skeletal limestone, light gray flint-bearing clumps of insect debris, algae clastic limestone, gray microcrystalline bone clastic limestone, light gray micrite silt bioclastic limestone, light gray algae gravel debris limestone and spongy needle limestone and gray lime-bearing mudstone, bio-limestone, etc., mainly mixed with sandy or lime mudstone, 119 m thick. Upper section is lime-bearing mudstone (= micrite?), loess-colored mudstone, gray-lime silt to fine quartz sandstone, gray bioclastic limestone, gray mudstone, sandy mudstone, dark gray gravel-bearing bioclastic limestone, gray sandstone, gray bioclastic limestone, gray lime-bearing coarse sandstone and sandy bioclastic ash rock, gray limestone aggregate limestone and limestone silt rock interbedded with a thickness of 119 m.

Fossils include ammonoids, bivalves, crinoids, brachiopods, foraminifers, conodonts, corals, bryozoans, gastropods, anemones, plants and sporopollen. The important representatives in the lower part are the bivalves: Halobia cf. kui, H. subcomata; the conodont: Neogondolella polygnathiformis; the important representatives in the upper part are the ammonoid: Trachyceras sp., the bivalves: Halobia rugosa, H. convexa, H. cf. austriaca, and conodonts: Neogondolella polygnathiformis and foraminifer Aulotortus bronimanni and so on.

Marine facies