New Study Of Late Cretaceous Flora From The Yong’ancun Formation In Jiayin Of Heilongjiang, China

Jiayin area is located in the north of Heilongjiang Province, China, adjacent tothe Zeya-Bureya Basin of Russia and not far to southwest from the Songliao Basin,the largest non-marine sedimentary basin in Northeast China. Jiayin is well known inthe world for yielding dinosaur fossils represented by Mandschurosaurus. Themiddle-late Late Cretaceous strata are well exposed in Jiayin area, yielding abundantfossils, which is an ideal place for studying the Late Cretaceous biota, strata andterrestrial K-Pg boundary. However, all the previous study was focusing on themiddle-upper parts of the Yong’ancun Formation in the Jiayin area, while the strataand flora of the lower-middle parts of the Yong’ancun Formation have been limited toknow due to lacking the fossil material and good outcrops, which has affected thein-depth study of the middle Upper Cretaceous flora in this area.In early2014, since the new road construction carried out in the East Hill of theYong’ancun village, which provides a valuable opportunity to the author to do thenew circle study of the fossils from the lower-middle parts of Yong’ancun Formation.Under the supervisor’s advice, the author has done the new field work in the East Hillof the Yong’ancun village, with measuring a new stratigraphic section, collectingmore than200pieces of mega-plant fossils,11palynological samples, over20samples for study of ostracodes, and5pieces of fossil bivalves, and has done thelaboratory work in detail. The main achievements of the present study include thefollowing aspects:1. The author first found the aquatic angiosperm fossils represented by Cabbonia,with detailed description on Cabbonia corrugate and analysis on its function for itspalaeoecological reconstruction. The new discovery not only promotes the knowledge of the composition of the flora from the Yong’ancun Formation and the geologicalrange of this taxon, but also put forward the study of the Cretaceous Cabbonia inChina and the North-Hemisphere.2. Newly found the important reproductive organs of angiosperm, Nyssidiumarcticum, which greatly improved the research level of the angiosperms in the LateCretaceous flora from the Yong’ancun Formation. The new finding of the10taxa ofplants (including6taxa of angiosperm) enriched the studying contents of the florafrom the Yong’ancun Formation in Jiayin, and improved the paleoecological study onthis flora.3. The new studying of43genera and54species of palynomorphs, and withnewly recognizing3palynological sub-assemblages (including Cyathidites-Pinuspollenites-Retitricolpites Sub-Ass., Dictyotriletes-Cyathidites-PinuspollenitesSub-Ass. and Dictyotriletes-Pinuspollenites-Podocarpidites Sub-Ass.) from thelower-middle parts of Yong’ancun Formation for the first time, plays a significantcomplementary role for the study of the Yong’ancun palynoflora.4. Stratigraphically, the new palynological study provides important evidencethat the palynoflora of the Yong’ancun Formation can be correlated to the Members2-3of the Yaojia Formation and the Member1of the Nenjiang Formation in theSongliao basin, which strongly evidenced the age of the Yong’ancun Formation as theSantonian of middle Late Cretaceous.5. The study of the Yong’ancun Formation flora was integrated with mega-plantand spore-pollen fossils in combination, which provides more comprehensive andreliable evidence for better understanding of the floral composition, age, andpaleoecological background of the Yong’ancun Formation.In sum, the new circle study made by the author, has provided new data for thestudy of the mega-flora, micro-flora, stratigraphy, paleoclimate and paleoenvironmentof the Late Cretaceous Yong’ancun Formation, which would clearly put forward theresearch level promoted in this areas.