New evidence suggests pyroclastic flows are responsible for the remarkable preservation of the Jehol biota.
The lower Cretaceous Yixian and Jiufotang formations contain numerous exceptionally well-preserved invertebrate, vertebrate and plant fossils that comprise the Jehol Biota. Freshwater and terrestrial fossils of the biota usually occur together within some horizons and have been interpreted as deposits of mass mortality events. The nature of the events and the mechanisms behind the exceptional preservation of the fossils, however, are poorly understood. Here, after examining and analysing sediments and residual fossils from several key horizons, we postulate that the causal events were mainly phreatomagmatic eruptions. Pyroclastic density currents were probably responsible for the major causalities and for transporting the bulk of the terrestrial vertebrates from different habitats, such as lizards, birds, non-avian dinosaurs and mammals, into lacustrine environments for burial. Terrestrial vertebrate carcasses transported by and sealed within the pyroclastic flows were clearly preserved as exceptional fossils through this process.
State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, 163th Xianlin Avenue, Qixia District, Nanjing, Jiangsu 210046, China.
Baoyu
B
Jiang
Department of Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th St. New York, New York 10024, USA.
George E
GE
Harlow
Geophysics Group, EES-17, MS F665 Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Kenneth
K
Wohletz
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, China.
Zhonghe
Z
Zhou
Division of Paleontology, American Museum of Natural History, Central Park West at 79th St. New York, New York 10024, USA.
Jin
J
Meng
D000818:Animals; D044822:Biodiversity; D002681:China; D005580:Fossils; D019015:Geologic Sediments; D018707:Volcanic Eruptions