The Permian-Triassic crisis in the biosphere as manifested in the Paleo-Pacific deep-water sequences

The deep-water successions in Japan, Sikhote-Alin, and Nevada demonstrate a sharply decreased silica productivity across the Permian-Triassic boundary , accumulation of carbonaceous shales, and virtually absolute absence of fo ssil radiolarians and sponges. In Japanese sections, this stratigraphic lev el is enriched in titanium, phosphorus, and yttrium, and also demonstrate a sharp decline in cerium content relative to other rare-earth elements. The se phenomena are directly or indirectly related to the biotic crisis at the Permian-Triassic boundary. The geochemical anomalies are interpreted as re lated to significant environmental changes in response to intense tectonic activity. The changes caused extinction of many marine biotic groups, inclu ding siliceous plankton, and increased the primary productivity of lower ph ytoplankton taxa. The event in question differs from the Mesozoic anoxic ep isodes in its origin, significance, and duration, being followed by the wel l-manifested biotic crisis.