Mid and late Holocene climate changes recorded by biomarkers in the sediments of Lake Gouchi and their relationship with the cultural evolution of northern Shaanxi

The climatic and environmental characteristics of the Holocene are much debated, especially the occurrence of a climatic optimum in the mid-Holocene and the interactions between human civilization and the environment. Knowledge of the Holocene climatic evolution of the Mu Us Sandy Land in North China is important for understanding the cultural development of northern Shaanxi. However, few continuous and high-resolution lake sedimentary records are available from the region. We selected Lake Gouchi, a climatically sensitive site in the Mu Us Sandy Land, for a study of sedimentary organic indicators such as n-alkanes, with the objective of reconstructing the regional climatic history since the mid-Holocene. Our results indicate that during 8130-4500 BP, the regional climate was relatively warm and humid, the terrestrial vegetation was dominated by woody plants, and the nutrient level of the lake was relatively stable. Then the climate gradually became arid. However, at the beginning of 2500 BP, there was an 800-year period of warm and humid conditions. Entering the historical period there was an increase in the environmental impacts of human activities. Overall, the climate of the Gouchi area was influenced by the response of the East Asian summer monsoon to changes in Northern Hemisphere summer insolation, which were responsible for the mid-Holocene Maximum. Comparison of the climatic record of Lake Gouchi with the sequence of cultural evolution in northern Shaanxi reveals a distinct relationship. Favorable climatic conditions were associated with technological development, an increasing population, and a flourishing civilization; whereas less favorable climatic conditions were associated with cultural stagnation or decline.