Morphological diversity of Quercus fossil pollen in the northern South China Sea during the last glacial maximum and its paleoclimatic implication

We aimed to obtain high resolution vegetation data and climate information about the LGM in the inland of the northern SCS based on key pollen types. Dominant Quercus fossil pollen grains in the core from the continental shelf of the northern SCS have been identified at the infrageneric level by using scanning electron microscopy. Based on tectum ornamentation, we recognized five sculpture types of Quercus pollen, namely, rodlike, rodlike masked, rodlike vertical, verrucate and micro-verrucate. Such a high diversity of Quercus fossil pollen types indicated that broadleaved forests were widely distributed in the inland along the northern SCS and included species of the subgenera Cyclobalanopsis and Quercus, of which subgenus Cyclobalanopsis populations were highly dominant. Low abundance of deciduous Quercus pollen probably derived from temperate-subtropical forests, while abundant evergreen pollen types of subgenura Quercus and Cyclobalanopsis, as well as other pollen of broadleaved taxa in the pollen assemblages, strongly suggest that the inland has been covered by dense subtropical forests. Consequently, the warm and humid subtropical climate prevailed during the LGM in the inland along the northern SCS. Our results shed new light on regional climatic conditions during the LGM in eastern Asia based on high diversity of Quercus fossil pollen in marine deposits from northern SCS.