NOAA/WDS Paleoclimatology - Lake Orurillo, Peru d2H and d18O Data Over the Past 5000 years

Tiwanaku was a regionally significant, state level polity in the south-central Andes from ca. 500-1000 CE. The development of complex society in the region was greatly facilitated through intensified agricultural systems that relied on monsoonal precipitation. At the end of the first millennium CE, the Tiwanaku political regime collapsed, and their raised field systems were mostly abandoned within 200 years or less. It has been suggested that a prolonged period of aridity contributed to the collapse, but questions have remained about its chronology and severity. In this study, we investigated the relationship between d2Hwax and d18Ocalcite values, aridity and societal change. A period of nondeposition or erosion occurred between 915 and 1025 CE indicating a low lake stand exposing the core site. This extended and pronounced drought ending 1025 CE was recorded in the isotopic proxies extracted from lake sediments that show this period of aridity persisted into the 13th century. The broad agreement between our record and other regional paleoenvironmental archives of Holocene climate variability is consistent with Northern Hemisphere oceanic and atmospheric circulation patterns as a mechanism for driving centennial scale climate change in the Andes and supports the correspondence between prolonged drought and the collapse of Tiwanaku.

蒂瓦纳库（Tiwanaku）是公元500年至1000年左右安第斯山脉中南部地区具有区域影响力的国家层级政体。该区域复杂社会的发展，极大得益于依托季风降水的集约化农业体系。公元第一个千年末期，蒂瓦纳库政权崩塌，其抬升农田系统（raised field systems）在200年以内便基本被废弃。有研究认为长期干旱是该政权崩塌的诱因之一，但关于此次干旱的年代序列与严重程度，学界仍存在诸多疑问。本研究针对氢同位素比值（d2Hwax）、方解石氧同位素比值（d18Ocalcite）与干旱程度及社会变迁之间的关联展开了探究。公元915年至1025年间存在沉积间断或侵蚀事件，表明当时湖面水位下降，核心遗址裸露。从湖相沉积物中提取的同位素代用指标记录了这场持续至公元1025年的显著干旱事件，数据显示该干旱时期一直延续至13世纪。本研究的气候记录与其他区域全新世气候波动的古环境档案高度吻合，这与驱动安第斯山脉百年尺度气候变化的北半球海洋与大气环流机制相一致，同时也佐证了长期干旱与蒂瓦纳库政权崩塌之间的对应关系。