东秦岭晚白垩世恐龙多样性降低的气候因素

Late Cretaceous paleoclimatic effects on the decreased dinosaur biodiversity in East Qinling

气候与环境变化是影响生物群演化的关键驱动因素,因此研究陆地生态系统所处的古气候与古环境背景对于探讨生物盛衰甚至灭绝具有重要的意义.我国盛产恐龙骨骼和恐龙蛋化石,但迄今对于古气候-环境演化与恐龙种群数量和多样性演化联系的研究相对匮乏.东秦岭地区发育多个晚中生代-早新生代陆相沉积盆地,蕴含大量晚白垩世恐龙骨骼和蛋、新生代哺乳动物化石,是开展古气候与恐龙动物群多样性演化关系,探究恐龙灭绝原因的理想场所.本研究对东秦岭灵宝盆地好阳河剖面开展环境磁学和元素地球化学研究,重建了该区晚白垩世-早始新世期间的化学风化强度和古水文循环过程,以揭示生物-环境协同演化的关系.化学风化强度和磁化率记录表明晚白垩世-早始新世期间灵宝盆地古气候-水文环境发生了三次大的阶段性变化:在约74.4~68.0 Ma,研究区处于水动力较稳定的深湖相沉积环境和逐渐变冷的气候状态;随后68.0~65.8 Ma时期研究区逐渐干旱化,水文波动变强;在65.8~54.7 Ma,区域气候变化强烈,呈现明显增强的干湿水文循环.本研究揭示了古气候-水文环境变化与恐龙种群演化的关系,提出东秦岭地区在晚白垩世末期(约68~66 Ma)的气候干旱化及变强的水文波动可能是驱动该区恐龙动物群多样性降低的主要原因,为深入理解生物-环境协同演化提供了新数据支撑.

Climatic and environmental changes are the principal drivers affecting biota evolution.Therefore,reconstructing the paleoclimate and paleoenvironment background of terrestrial ecosystems is critical for discussing the evolution and extinction of biota.China is located in East Asia and is rich in dinosaur bone fossils and eggshells.However,the effects of climate and hydrologic environment in China on dinosaur biodiversity variation remain unclear.In East Qinling,several Late Mesozoic-early Cenozoic sedimentary basins preserve abundant Late Cretaceous dinosaur bone and egg fossils and Cenozoic mammal fossils.Thus,it is an ideal area to explore the relationship between the evolution of dinosaur biodiversity and regional climate changes.Here,we performed environmental magnetism and geochemistry at the Haoyanghe section of the Lingbao Basin to reconstruct the silicate weathering history and climate-hydrologic environment variation.The magnetic susceptibility and chemical weathering intensity reveal three stages of climatic-hydrological evolution.During ca.74.4~68.0 Ma,the study area was in a stable hydrodynamic and deep-lacustrine environment with a gradually cold climate.From 68.0 to 65.8 Ma,the region became increasingly aridification,and the intensity of hydrological fluctuation strengthens.During ca.65.8~54.7 Ma,the regional climate changed strongly,showing an enhanced dry-wet hydrological cycle.This study reveals the relationship between paleoclimate-hydrologic environment changes and dinosaur population evolution,suggesting that the climatic aridity and increased hydrologic fluctuation at the end of the Late Cretaceous(ca.68~66 Ma)may be the main driving factor for the low biodiversity and extinction of the dinosaurs in East Qinling.Our study provides new data support for further understanding of the co-evolution of biology and environment.