Arctic Mesozoic Floras: ABSTRACT

Abstract

Mesophytic floras (Late Triassic-Early Cretaceous) of the Arctic are irregularly distributed and poorly studied. The floras studied in more detail are Carnian-Norian of Spitsbergen, Rhaetian and early Lias of East Greenland, Late Jurassic of the Lena basin, and Early Cretaceous of West Greenland, Spitsbergen, Franz Josef Land, and the Lena and Kolyma basins. Mesozoic floras of Arctic Islands were not isolated from continental ones. Undoubtedly close connection existed between the Late Triassic floras of Spitsbergen and Franz Josef Land and the middle Keuper floras of Western Europe; the Early Cretaceous floras of Spitsbergen, Kong Karls Land, Franz Josef Land, and Kotel'nyy Island were connected with coeval floras of northern Asia. Botanic-geographic zonation was more prominent during the second phase (Late Jurassic-Early Cretaceous) of the mesophytic floras than during the first phase (Late Triassic-Middle Jurassic). It is assumed that Late Triassic floras of Spitsbergen and Franz Josef Land comprised a special part of the European province of the Indo-European paleofloristic area. Late Triassic thermophilic vegetation traces are preserved in the southern Lena basin (Aldan River). Beginning in the Early Jurassic temperate vegetation formed in the Lena basin (Vilyuy trough) and farther south (South Yakutsk basin and other regions); later, in the Middle Jurassic temperate vegetation appeared farther north (lower Yenisey River), and then more widely in the Late Jurassic, and especially in the Early Cretaceous Arctic and Subarctic floras. The Early Jurassic flora of northeastern USSR (west bank of the Kolyma River) is similar to the Indo-European area floras; it is possible that an Indo-European and Siberian area boundary is farther north than Central Siberia, or that a special area existed which included Early Jurassic floras of southern Alaska. Late Jurassic and Early Cretaceous Arctic floras (except West Greenland floras) are typical floras of the Siberian paleofloristic area. The Arctic climate changed between Late Triassic and Early Cretaceous times from a hot (possibly tropical) climate to a temperate warm and humid climate favorable for profuse woody plant development. End_of_Article - Last_Page 2511------------