Micromorphology of the loess-paleosol sequence of the last 130 ka in China and paleoclimatic events

The Late Quaternary loess-soil sequences in Xifeng, Luochuan and Weinan are studied to investigate the micromorphology of both loess and paleosols. Many features have clear climatic implications and may be used as indications for morpho-stratigraphic and climatic correlation. The temporal and spatial variations of these features allow us to define 16 climatic events for the last 130 ka, which are highly consistent with the variations in palco-weathering intensity. Part of these events are attributable to the orbital forcing while others are more or less synchronous with the Heinrich events recorded in the North Atlantic Ocean. During the last events, the Loess Plateau was characterized by sparse vegetation cover and strong winds while the climatic conditions between these events were considerably humid, resulting in a significant steppe cover.

约0.85Ma前后黄土高原区季风强度的变化

第四纪气候演化以周期性的冷暖更替为主要特征,在我国黄土区则表现为黄土堆积与土壤发育的更迭。黄土高原地处东亚季风区,多数学者认为,其古环境的演化在很大程度上受古季风强度变化的控制。研究东亚季风的演变是深入认识该区古环境、乃致全球变化的关键之一。但迄今对黄土记录的古季风演化的研究至少还存在两个问题:第一,对古土壤研究的不足,限制了对古季风演化趋势的认识。过去的古土壤研究侧重于离石黄土以上部分,而午城黄土中的古土壤研究甚少;第二,目前对黄土区古气候代指标的研究仍没有达到成熟的地步。