Figure and table captions
Fig. 1. Simplified tectonic map of the southern Tibet (modified
from Pan et al., 2004). Location of the study area is indicated by a red
star.
Fig. 2. Photos are showing: (a) bioclastic grainstone, (b)
bioclastic wackestone, (c) coral framestones, (d) shell bed mainly
composed of Lithiotis , (e) mudstone and grainstone, (f) sand lens
and erosive base. The contact between mudstones and grianstones is
erosive.
Fig. 3. Correlation of stratigraphic distribution of carbonate
carbon isotopes of the Menqu section and distribution of organic carbon
isotopes of the Nianduo section (Han, Hu, Kemp, & Li, 2018). The blue
dashed line means the boundary between the Pupuga Formation and the
Nieniexiongla Formation.
Fig. 4. Photo of oolitic grainstones from Nieniexiongla
Formation (plane polarized light microscopy image).
Fig. 5. EPMA points of ooilitic grainstones (polished thin
section, EPMA backscattered electron image, results of green points with
numbers could be seen in Table 1). (a) 17MQ56-03:1 and 17MQ56-03:2 are
ferruginous mineral, 17MQ56-03:3 is quartz; (b) 17MQ66-02:1,
17MQ66-02:2, 17MQ66-02:3 and 17MQ66-02:4 are all ferruginous mineral.
Fig. 6. (a) ooid with euhedral ferruginous minerals in nuclei
and ferruginous spheroids in cortex (polished thin section, SEM
backscattered electron image), (b) ooid with euhedral ferruginous
(polished thin section, SEM backscattered electron image), (c) euhedral
ferruginous particles (fresh fragment, SEM image), (d) regular six-sided
euhedral ferruginous particles (polished thin section, SEM backscattered
electron image), (e, f) euhedral ferruginous minerals show concentric
structure (polished thin section, SEM backscattered electron image).
Fig. 7. (a) ferruginous particles make up of a concentric layer
around the cortex (polished thin section, SEM backscattered electron
image), (b) ooids contain ferruginous particles with quartz nuclei
(polished thin section, SEM backscattered electron image), (c)
ferruginous aggregated spheroids (fresh fragment, SEM backscattered
electron image), (d) ooids contain ferruginous particles with different
nuclei (polished thin section, SEM backscattered electron image).
Fig. 8. Linear scan of sulfur and iron distribution of a
ferruginous particle by SEM-EDS. Polished thin section, SEM
backscattered electron image.
Table 1. Results of EPMA analysis of different minerals in red
ooid grainstones (oxide values are given in molar).