East Asia occupies the key position in the Triassic correlation of the circum-Pacific region, Tethys, and marginal Gondwana, because it includes important areas from all of those realms. This chapter presents biostratigraphic correlations for the major Triassic groups of organisms (Tables 19.1–19.3). Detailed discussion of how these charts were worked out would be lengthy and will be omitted here.
Early Triassic biogeography of East Asia
The East Asian area of the early Triassic has been subdivided into the following realms and regions: the northern temperate North Laurasian Realm, including the Boreal Sea Region (northeastern Asia, I1) and the North Eurasian Region (I2); the northern warm-temperature Central Laurasian Realm, including the Central Eurasian Region (II2) and its Marginal Seas Region (II1); the tropical–subtropical Laurasian Tethys Realm, including the Cathaysian Tethys Region (III1) and its Southern Margin Region (III2); the southern temperate Gondwanan Realm, including the Indian Subcontinent Region (V); and the Gondwanan Tethys Realm, including the Himalaya–Banda Loop Region (IV) (Figure 19.1)
Boreal Sea Region of the North Laurasian Realm (northeastern Asia, I1)
This region covers the Verkhoyan (Verchojan)–Chukote (Chukchi) and Mongol–Okhotsk areas, where carbonate sediments are extremely rare. The biota was dominated by ammonoids and bivalves (Dagys, Arkhipov, and Bychkov, 1979): early Griesbachian ammonoids Otoceras, Tompophiceras, Hypophiceras, Anotoceras; late Griesbachian Boreal ophiceratids (Ophiceras boreale, Ophiceras indigirense, Ophiceras commune); a Spathian Keyserlingites assemblage, including Olenikites, Svalbar dicer as, Sibirites, and Nordophiceras; there were no Smithian Owenites and Spathian Columbites and Tirolites [Tirolites morpheus (Popov) from Verkhoyan has been renamed Tompoites].