The world-famous Jehol Biota fossil lagerstätte accumulated in Ancient Lake Sihetun.
Lake Sihetun was an Early Cretaceous volcanic caldera lake (maar) in NE China.
Lake sediments record four cycles of pyroclastic eruption and lake chemistry change.
Lakewater chemistry fluctuated from acidic to alkaline during each eruption cycle.
Low molybdenum isotope values (δ98/95Mo = –2.50‰) document hydrothermal inputs.