Palynology of Yanchang Formation of Middle and Late Triassic in Eastern Gansu Province and Its Paleoclimatic Significance

The oleaginous Botryococcus from the Triassic Yanchang Formation in Ordos Basin, Northwestern China: Morphology and its paleoenvironmental significance

“…Spores and pollen that accompany Botryococcus in the lake sediment consists mainly of pinaceous pollen, tropical/subtropic evergreen or latifoliate angiosperm pollen, and wetland Pteris and Cibotium spores. This is similar to the spore and pollen assemblage in Ch 7-Ch 8 sections of the Yanchang Formation (Ji and Meng, 2006). It suggests that the latitude and climate of the palaeolake in the Middle-Late Triassic Ordos Basin were similar to that of Fuxian Lake and conducive to the bloom of Botryococcus.…”

“…The lake transgression and water area expansion, warm temperature, and abundant rain during the period resulted in flourishing conditions for Botryococcus. Not only are abundant Botryococcus fossils are found in the Xifeng area, but other researches have confirmed through analysis of spores, pollen, and acritarchs that limnetic and palaeoclimatic conditions during the development stage of the Ch 7 section (Yanchang Formation, Ordos Basin) was similar to that in the Tertiary Jiyang Depression (Ji and Meng, 2006;.…”

“…The study of sporopollen assembles from the Ch 8 to Ch 7 sections in the Xifeng area reveals that their geological ages are the Ladinian (late Middle Triassic) and the Carnian (early Late Triassic). Hereby, their time limits should respectively be 6.9 and 6.7 Ma (Ji and Meng, 2006). The mediumduration cycles in the Ch 8-Ch 7 sections can be subdivided into many short-duration cycles, even sub short-duration cycles (Ni et al, 2007).…”

Upper Permian Junggar and Upper Triassic Ordos lacustrine source rocks in Northwest and Central China: Organic geochemistry, petroleum potential and predicted organofacies

“…Late Permian (~270 Ma) Palynomorphs (Carroll et al 1992;Carroll et al 1995;Metcalfe et al 2009); nonmarine ostracods and molluscs (Liao et al 1987;Zhang 1981) Late Triassic (~240 Ma) Zircon SHRIMP U-Pb of tuffs ; palynomorphs (Ji et al 2010) Palaeolatitude 39°-43°N Palaeomagnetism (Nie et al 1993;Sharps et al 1992); palaeogeographic reconstructions (Lottes and Rowley 1990) 31°N Palaeomagnetism (Wu et al 1991;Yang et al 1991) Environment Lake Fish fossils (Liao et al 1987); macrofauna Lake Palaeogeography, fish fossils, palynology (Chen et al 2007;Ji and Meng 2006;Ji et al 2006a;Ji et al 2010) Local climate Temperature Cool, temperate Floral assemblages (Hu 1985;Liao et al 1987;Zhang 1981;Ziegler 1990) Temperate to subtropical Palynology (Ji and Meng 2006) Laminated lithofacies (Carroll et al 1992); fish scales and other remains (Carroll 1998) Anoxic below Storm wave base Laminated lithofacies (Lin et al 2013;Yuan et al 2015); trace element analysis (Yang et al 2010b;Zhang et al 2008 (2) Silicic Lucaogou basinal mudstones deposited under oxygendeficient conditions comprise the best quality source rocks with high total organic carbon (up to 12.40%), the most generative S 2 content (66.01 mg HC/g) and relatively high Hydrogen Indices Otherwise, lesser oil-generative potential exists in shallower water, better oxygenated Hongyanchi marginal mudstones which have more aromaticity derived from terrestrial vitrinite input. Homogenous laminated black shales in Chang 7 display distinct geochemical behaviour in each unit.…”

“…3a). Detailed paleontological information about palynomorphs including an Asseretospora-Walchiites assemblage (Ji and Meng 2006), various flora of prolific Leiosphaeridia and Botryococcus (Ji et al 2010), and extensive fauna of Coelacanth suborder, Congiopodoidei, Ostracoda, and Amellibranchia (Chen et al 2007) have been reported from the Chang 7 Member. …”